Accepted Manuscript A review of petroleum emulsions and recent progress on water-in-crude oil emulsions stabilized by natural surfactants and solids Abubakar Abubakar Uma, Ismail Bin Mohd Saaid, Aliyu Adebayo Sulaimon, Rashidah Bint Mohd Pilus PII:
S0920-4105(18)30198-0
DOI:
10.1016/j.petrol.2018.03.014
Reference:
PETROL 4755
To appear in:
Journal of Petroleum Science and Engineering
Received Date: 15 April 2017 Revised Date:
15 September 2017
Accepted Date: 2 March 2018
Please cite this article as: Uma, A.A., Saaid, I.B.M., Sulaimon, A.A., Pilus, R.B.M., A review of petroleum emulsions and recent progress on water-in-crude oil emulsions stabilized by natural surfactants and solids, Journal of Petroleum Science and Engineering (2018), doi: 10.1016/j.petrol.2018.03.014. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Available online at www.sciencedirect.com
Journal of Petroleum Sciences and Engineering
4 5
Abubakar Abubakar Umara, Ismail Bin Mohd Saaid*b, Aliyu Adebayo Sulaimonc, Rashidah Bint Mohd Pilusd
SC
Abstract
During production of conventional as well as heavy oils, emulsions occur at well bore, in pipelines, and at surface facilities. As the production time of the oil wells increases, there will be an increased coproduction of oil and water in the form of emulsions. These emulsions are undesirable because they result in high pressure drop due to their high viscosity. They also cause serious corrosion problems due to presence of chlorides dissolved in water. These emulsions must be treated to meet production and transportation requirements, and to maximize the overall profitability of the crude oil production. Apart from the undesirable emulsions, the petroleum industry is witnessing a surge in the application of emulsions for beneficial processes. Both cases would be discussed in this review. This subject has experienced an extensive research over the years, with highly complicated theories regarding the phenomena involved in its formation (emulsification) and breaking (demulsification). Crude oils, irrespective of their origin, contain certain components or characteristics which tend to make them emulsifiable. These crude oil components are referred to as emulsifiers, and they vary so widely with the nature of the crude oil. The natural interfacially active components responsible for emulsion stability undoubtedly come from the resin and asphaltenes of the crude oil. However, the presence of other solids like crystalline waxes, clays, corrosion products and mineral scales may lead to the formation of very stable water-in-oil (w/o) emulsions. The nature of these particles controls the type as well as the stability of emulsions produced. Apart from the natural emulsifiers, chemical enhanced oil recovery (EOR) techniques have been reported to produce stable w/o and o/w emulsions. It is believed that the alkali, surfactant and polymers used in these techniques are responsible for these stable emulsions. When they form, these emulsions increase pumping costs, heighten the chances of pipeline and equipment erosion, corrosion rate, scaling and lower the produced oil API gravity. These emulsions have to be treated to remove the dispersed water and accompanying inorganic salts in order to meet market specifications, transportation requirement and to reduce corrosion and catalyst poisoning in downstream processing. Despite the huge and concerted efforts by researchers from the academia and the petroleum industry, there are few fundamental and applied investigations into the roles of native solids in combination to natural emulsifiers on the stabilization of petroleum emulsions. This paper presents a comprehensive overview of the progress made in the field of petroleum emulsions, principally the roles of particles in combination to asphaltene and resin in stabilizing w/o emulsions. The study also charts a way for emulsions studies that could lead to an effective demulsification via thorough characterizations of the solids believed to the enhancers of emulsion stability in order to tailor demulsifiers based on the characteristics of such emulsifiers.
M AN U
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Department of Petroleum Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar 32610, Perak Malaysia
TE D
7
a,b,c,d
EP
6
AC C
2
RI PT
3
A Review of Petroleum Emulsions and Recent Progress on Waterin-Crude Oil Emulsions Stabilized by Natural Surfactants and Solids
1
Keywords: Water-In-Oil Emulsions (W/O); Oil-in-water (O/W); Pickering, Emulsifiers; Demulsifiers; solid particles; Surfactants.
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
2
36
1. Introduction The process of stabilization of oil and water droplets by solid particles has been acknowledged for over a
38
century. Currently, these particle-stabilized emulsions are largely known as Pickering emulsions. They occur in
39
personal care products, the food industry and have long been used in oil recovery and mineral processes
40
(Bernardini 2015). These are industries where such emulsions are desirable for achieving certain characteristics of
41
the products. In the oil and gas industry however, the formation of emulsion during oil production is a pricy
42
problem, both in terms of chemicals used and the production lost (Kokal 2005). These emulsions have to be treated
43
to remove the dispersed water and accompanying inorganic salts in order to meet market specifications,
44
transportation requirement and to reduce corrosion and catalyst poisoning in downstream processing (Kokal and
45
Wingrove 2000). Surfactants with small molecular weight or amphiphilic polymers have long been employed in
46
certain industries in emulsion stabilization, either by reducing interfacial tension or forming a viscoelastic
47
interfacial film. Although these surfactants have been well understood and are widely in use, they are not the only
48
potential sources of stabilization of emulsions. Colloidal particles with suitable wettability partially in both the
49
dispersed and continuous phases can function as Pickering-type stabilizer by forming a physical barrier at droplet
50
interface. This phenomenon is discussed in detail in section 6.2 of this review paper.
M AN U
SC
RI PT
37
51
Several other researches have shown that asphaltenes are the prime stabilizers of water-in-oil emulsions and that
53
resins are needed to solvate the asphaltenes (Fingas, Fieldhouse et al. 1999, Fingas and Fieldhouse 2003, Fingas
54
and Fieldhouse 2004, Fingas 2014). Certain studies however found out that a synergy in stabilization occurs when
55
asphaltenes and fine solids jointly stabilize an emulsion based on a certain fractional area ratio of 2:1 of asphaltenes
56
to solids (Sztukowski and Yarranton 2005). In a similar work, (Bobra, Fingas et al. 1992) established that waxes
57
cannot act as emulsifiers by themselves, but can stabilize emulsions in combination with asphaltenes or resins.
58
Thus, according to their findings, a concentration of 0.01g/ml of asphaltenes did not produce a stable w/o emulsion,
59
but when 0.05g/ml of wax added, stable emulsions were formed. However, an asphaltene concentration of 0.03g/ml
AC C
EP
TE D
52
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
3
60
without the presence of wax produced a stable emulsion. These findings were repeated by the authors of this paper,
61
and the results found corroborated this result.
62
2. The Emulsion Problem The problem of separating water from produced crude oil is as old as the oil industry itself. At the beginning of
64
the oil industry, the water separation problem was handled by settling the free water from oil in open tanks or pits
65
and the sludge (an intermediate phase between clean water and clean oil) was disposed of, ordinarily by burning
66
(Meyer 1964). It was not more than a century ago that attention was drawn to the fact that “sludge” is an emulsion
67
of crude oil and water, and that substantial amount of merchantable oil can be recovered from the emulsion (API
68
1961). By crude oil emulsions, we are referring to water-in-oil (W/O) emulsions because most emulsions are this
69
type (Kokal and Wingrove 2000). Although oil-in-water (O/W) emulsions also form and are encountered in the
70
industry, they are generally resolved in the same way W/O emulsions are resolved, except electrostatic treaters
71
cannot be used on O/W emulsions (Kokal 2005). At the time when crude oil and water are leaving the wellbore of
72
an oil well, tight w/o emulsions can form due to the turbulence in the choke valve at the wellhead (Janssen, Noïk et
73
al. 2001). The formation of emulsion during crude oil production is a very costly operational problem. It occurs
74
when hydrocarbon and formation water in the reservoir and in production pipes are extremely mixed under
75
shear/turbulence, and in the presence of surface active agents (Fingas, Fieldhouse et al. 1999, Opawale and
76
Osisanya 2013) (Ngai and Bon 2014).
77
The continuous phases of these emulsions depend on the water to oil ratio, the natural emulsifier systems contained
78
in the oil, and the origin of the emulsion. The emulsifiers are complex chemically, and they come in different
79
shapes and sizes. As new oil fields are developed and as production conditions change in older fields, there is a
80
constant need for new, effective demulsification methods. The emulsion must be separated before the crude oil can
81
be accepted for transportation, to meet the residual salt and water content quality criteria for a delivered crude oil.
82
The water content must be less than 1% (Fink 2015).
AC C
EP
TE D
M AN U
SC
RI PT
63
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
4
83
2.1. Definitions of Emulsions Emulsions are thermodynamically unstable systems, since they will separate to reduce the interfacial area
85
between the oil phase and the water phase, as a function of time (Sjoblom 2001). Emulsions are metastable systems
86
typically formed in the presence of surfactant molecules, amphiphilic polymers or solid particles. The relative
87
balance of the hydrophilic and lipophilic properties of these emulsifiers is known to be the most important
88
parameter dictating the emulsion type: oil-in-water (O/W) emulsions are preferentially obtained with molecules
89
which are rather hydrophilic whereas water-in-oil (W/O) emulsions are produced in the presence of hydrophobic
90
molecules (Leal-Calderon and Schmitt 2008).
RI PT
84
91
(Manning and Thompson 1991) defined emulsion as a quasi-stable suspension of fine drops of one liquid in
93
another liquid. (Roberts 1926) defined emulsion as a system containing two liquid phases, one of which is
94
dispersed as globules in the other. Other researchers defined emulsion as a mixture of two mutually immiscible
95
liquids, one of which is dispersed as very small droplets in the other, and is stabilized by an emulsifying agent
96
(Aziz, Darwish et al. 2002) (Singh, Thomason et al. 2004) (Kokal 2008).
M AN U
SC
92
97
Another definition of oil field emulsions was proposed by (Roberts 1926). According to his work, he maintained
99
that oilfield emulsions vary from extremely unstable types, which should more accurately be called suspensions, to
100
extremely stable ones. Based on that, he classified emulsions into three classes, according to their behavior in the
101
hand centrifuge. These are: (a) Emulsions that show only clear oil and; and are better referred to as suspensions,
102
thus if allowed to stand will generally separate into their different phases without any form of treatment. However,
103
certain unstable emulsions occur which are capable of resolution in the centrifuge, especially when diluted with
104
gasoline, but which will not settle to oil and water without any form of treatment. (b) Emulsions that show the
105
emulsion phase, with or without water, and a clear oil phase. These are real emulsions and must be treated to
AC C
EP
TE D
98
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
5
recover the emulsified oil (c) those that may or may not show emulsion and water phases, but which also show
107
cloudy oil after centrifuging.
108 109
Something common to all the definitions provided in this review and many others not stated here is the fact these
110
emulsions are thermodynamically unstable and separate into two phases if allowed to sit for a long time (Singh,
111
Thomason et al. 2004). These emulsions, which fall under macro-emulsions (having dispersed phase diameters
112
greater than 0.1µm) are said to be thermodynamically unstable systems because the contact between the oil and
113
water molecules is unfavourable, and so they will always break down over time. There has been more
114
comprehensive studies and a lot has been known about the formation and stabilization of oil-in-water emulsions
115
than of the water-in-oil emulsions type (Oliveira and Goncalves 2005). To understand the W/O emulsions, more
116
information is needed on the materials responsible for their formation and stabilization, and especially how solid
117
particles form or enhance their stabilizations.
118
2.2. Classifications of Emulsions
M AN U
SC
RI PT
106
Decades of far-reaching research work on water-in-oil emulsions (often called “chocolate mousse”) that form
120
after oil spill, (Fingas and Fieldhouse 2009) found that four classes of emulsions form when crude oil mixes with
121
water. Among the leading studies on classification of crude oil emulsion according to their stability are the works
122
of (Fingas, Fieldhouse et al. 1999, Fingas and Fieldhouse 2003, Fingas 2014, Fingas and Fieldhouse 2014) who
123
proposed new empirical data and corresponding physical knowledge of emulsion formation. Based on their studies,
124
the density, viscosity, saturates, asphaltene, resins and fine solids were used to propose an emulsion type
125
classification index which gives either an unstable, entrained, meso-stable or stable water-in-oil class of emulsion.
126
From the four classes, only stable and meso-stable states can be considered as emulsions. It is assumed that the
127
stability derives from the tough visco-elastic interface, triggered by asphaltenes and resins. Mesostable emulsions
128
are the emulsions between stable and unstable emulsions. It is thought that meso-stable emulsions lack sufficient
129
quantities of asphaltenes to render them completely stable. The meso-stable emulsions may degrade to form layers
AC C
EP
TE D
119
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
6
of stable emulsions. Given the oil and water phases, the type of emulsion formed depends on several factors. As a
131
rule of thumb, when the volume fraction of one phase is very small compared with the other, the phase that has the
132
smaller fraction is the dispersed phase and the other is the continuous phase. When the volume-phase ratio is close
133
to 1 (a 50:50 ratio), then other factors determine the type of emulsion formed (McClements 2008) (Kokal and
134
Wingrove 2000). Although emulsions are defined as stable dispersion of one liquid in another, not every mixture
135
or dispersion of water in oil is an emulsion. For a dispersion to qualify as an emulsion, it has to be a stable
136
dispersion (Bansbach 1965).
RI PT
130
137
M AN U
139 140 141 142 143 144 145 146 147 148 149 150
SC
138
Figure 1 (a) Water-in-Oil Emulsion
(b) Oil-in-Water Emulsion (Nalco)
Based on this, (Bansbach 1965) classified emulsions as Tight and Loose. Tight emulsions are those emulsion
152
characterized by very small sizes of the dispersed phase, while a relatively larger dispersed phase droplet
153
characterizes loose emulsions. According to (Bobra 1992) (Meyer 1964), the type of emulsifying agent determines
154
the type of emulsion that would form, either w/o or o/w. If the emulsifying agent is more favorably wetted by the
155
oil phase, the contact angle between the oil-water-solid boundaries, Ɵ, is greater than 90o and a w/o emulsion
156
forms. However, if the water phase more favorably wets the particle, then Ɵ is <90o and an o/w emulsion will
157
form. If the contact angle is much greater or much lesser than 90o, the emulsion will be unstable. According to
158
(Wang and Alvarado 2011), Stable emulsions form when the contact angle is near 90o As a rule of thumb, the
159
continuous phase of the emulsion is normally the one in which the particles are preferentially dispersed.
AC C
EP
TE D
151
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
7
160
(Fingas, Fieldhouse et al. 1999, Fingas and Fieldhouse 2003, Fingas 2014) classified emulsions into stable,
161
mesostable, entrained and unstable. Each of these emulsion types has unique characteristics and is believed to be
162
non-convertible to other types once formed.
(Kokal 2008, Fink 2015) in separate studies upheld that w/o emulsions form as a result of asphaltene and resin
165
surfactant behaviors in oil of moderate viscosities (50-2000mPa.s) and that oil field emulsions are sometimes
166
classified based on their degree of kinetic stability as Loose emulsions; those that will separate within a few
167
minutes, medium emulsions; that will separate in approximately ten minutes; and tight emulsions; that will
168
separate within hours, days, or even weeks, and even then, not completely.
Table 1 Some desirable and undesirable emulsions in the petroleum Industry (Schramm 2000).
SC
169
RI PT
163 164
Occurrence
Usual Type
Well-head Emulsions Fuel Oil Emulsions (Marine)
M AN U
Undesirable Emulsions
Oil Flotation Process (Froth) emulsions
Oil Sand Flotation Process (Diluted froth) Oil Spill Mousse Emulsions
TE D
Tanker Bilge Emulsions
W/O W/O
W/O and O/W O/W/O W/O O/W
Desirable Emulsions
Heavy oil pipeline emulsions
Oil Flotation Process froth emulsions Fuel-oil emulsion (70% heavy oil)
EP
Emulsion Drilling Fluid (Oil-Base Mud) Asphalt Emulsions
170 171
AC C
Enhanced Oil Recovery in-situ Emulsions
O/W O/W O/W W/O O/W O/W
172
Earlier, (Surfluh 1937) has classified emulsions as temporary and permanent. While a temporary emulsion will
173
break down into oil and water by settling methods, a permanent emulsion would remain stable until it is treated
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
8
174
effectively. Any method of preventing the formation of emulsions in oil and water mixtures must either reduce the
175
degree of agitation or must employ the use of chemicals to produce physicochemical changes which will aid in
176
emulsion prevention (Becker 1997). (Singh, Thomason et al. 2004) (Becker 1997) classified emulsions based on the size of the dispersed phase.
178
When the dispersed droplets are larger than 0.1 µm, the emulsion is referred to as macro-emulsion. Emulsions of
179
this kind are normally thermodynamically unstable (i.e., the two phases will separate over time because of a
180
tendency for the emulsion to reduce its interfacial energy by coalescence and separation). Emulsions are called
181
Micro-emulsions when the dispersed phase droplet sizes are less than 0.1µm. Micro emulsions are transparent and
182
can occur both as water-in-oil, or oil-in-water.
RI PT
177
Technically speaking, micro-emulsions differ from macro emulsions in several ways (McClements 2008)
184
(McClements 2015), while there exist a direct oil-water contact at the interface of a macro emulsions, such direct
185
contact is not present in micro emulsions. Also, macro emulsions are cloudy colloidal systems, while micro
186
emulsions are optically transparent (isotropic).
187
2.3. Crude Oil Emulsions formed during Enhanced Oil Recovery (EOR) Processes
188
Enhanced Oil Recovery (EOR) technique has always been a subject of interest in the oil and gas industry. Prior to
189
the fall in oil price which started June 2014, the high oil prices and energy demand all over the world has
190
necessitated the needs for Enhanced Oil Recovery (EOR) methods. Of recent, EOR techniques are getting more
191
attention by many countries since energy crises are getting worse and frightened. One of the reasons for this is due
192
to the shortage of current oil resources and difficulties in finding new oil fields all over the world. EOR has been
193
classified into five (5) categories, with general intent of reducing the mobility ratio between injected and in-situ
194
fluids, eliminating or reducing interfacial tension or doing both simultaneously (Sheng 2014, Standnes and
195
Skjevrak 2014, Talebian, Masoudi et al. 2014). Application of EOR technology gives an additional chance to get
196
out more oil from the reservoir, possibly about another 20 - 40%. These classes are Mobility-control, chemical,
197
miscible, thermal and other processes such as microbial. Despite the recorded successes, EOR processes are always
AC C
EP
TE D
M AN U
SC
183
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
9
198
accompanied with varying problems. The formation of strong emulsions and excessive formation of silicate scales
199
(Umar and Saaid 2013) especially with the application of high concentration of alkali.
200 (Li, Lin et al. 2005) studied the effect of alkaline–surfactant–polymer (ASP) flooding using sodium
202
hydroxide as the alkali constituent to enhance oil recovery of an onshore oilfield in Daqing, China. Although it has
203
increased the oil recovery, it has also created a new problem for the industry. Although the crude oil is paraffinic
204
(contains very little asphaltene), the alkali added formed stable w/o emulsion. The study reveals that the sodium
205
hydroxide solution reacts with fatty acids in the aliphatic fraction of the crude oil and/or with the fatty acids formed
206
from the slow oxidation of long chain hydrocarbons, and form soap like interfacially active components. These
207
accumulate at the crude oil–water interface and contribute to the stability of the oil/water emulsion.
SC
RI PT
201
208
(Li, Xu et al. 2007) investigated the effects of HPAM on crude oil/water Interfacial properties and the
210
stability of petroleum emulsions formed by Gudong crude oil. The investigation was conducted via measurement
211
of interfacial shear viscosity, interfacial tension, Zeta potential, and emulsion stability. They found out that HPAM
212
has the ability to adsorb at the interface between the oleic phase and water without decreasing the interfacial
213
tension. Increasing the HPAM concentration however, leads to increase in the interfacial shear viscosity, Zeta
214
potential, and stability of the emulsion.
TE D
M AN U
209
(Abidin, Puspasari et al. 2012) in a comprehensive review of polymers used in EOR processes believe that
216
there is an immense optimism that the use of polymer may play a significant role in resolving the current energy
217
crisis since its applications in some EOR fields has shown some successes to recover more than 20% additional oil
218
from OOIP. However, HPAM one of the most common polymers used in the EOR so far, was found to enhance the
219
stability of o/w emulsions and makes the water treatment difficult (Li, Xu et al. 2007).
221
AC C
220
EP
215
(Ahmadi and Shadizadeh 2012) investigated the implication of adsorption equilibrium when different
types of nanosilica and Zyziphus Spina Christi, a novel surfactant, were combined in aqueous solutions for EOR
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
10
222
and reservoir stimulation purposes. The study employed a conductivity technique to evaluate the adsorption of the
223
surfactant and nanosilica in the aqueous phase. Batch experiments were used to understand the effect of adsorbent
224
dose on sorption efficiency as well. The results from this study can help in appropriate selection of surfactants in
225
the design of EOR schemes and reservoir stimulation plans in carbonate reservoirs.
226 (Li, Lin et al. 2005, Li, Xu et al. 2007) at different times carried out laboratory studies concerning the
228
chemical nature of the emulsions produced by Da Qing crude oil (paraffinic crude oil- that contains very little
229
asphaltene and very low acid number). In this chemical flood where sodium hydroxide was used as the alkaline
230
component in the recovery of crude oil, production was enhanced but the recovered oil was accompanied by a
231
severely stabilized water-in-crude-oil emulsion. Certain studies however pointed to the fact that neither the
232
surfactant nor polymer are responsible for the stabilization of the w/o emulsion.
SC
RI PT
227
In a series of articles, Ahmadi and co-workers (Ahmadi and Shadizadeh 2012, Ahmadi and Shadizadeh
234
2013, Ahmadi and Shadizadeh 2013, Ahmadi and Shadizadeh 2015, Ahmadi and Shadizadeh 2016) have
235
conducted several studies ranging from estimation of adsorption behaviour of surfactants with nanosilica,
236
adsorption of solid surfaces like carbonate reservoirs, adsorption of new plant derived surfactants on quartz among
237
others. Results from these studies can help in making the right selection of surfactants in the design of chemical
238
EOR schemes and reservoir stimulation plans in carbonate reservoirs. Also, the studies presented economically
239
viable and environmentally friendly options for use in EOR techniques, particularly chemical flooding. Also, the
240
studies are very helpful in understanding the mechanism of surfactant loss into sandstone reservoirs.
241
2.4. Some Industry Applications of Emulsions- Desirable Emulsions
EP
TE D
M AN U
233
Despite the numerous posed to the oil and gas industry by the formation of emulsions during crude oil
243
production, emulsions and other materials like foams, have been used as mobility control or diverting agents in
244
different EOR processes and many other useful applications in the oil and gas industry, food industry, construction
245
industry, among others (Islam and Ali 1989, Israelachvili 1994).
AC C
242
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
11
(Mendoza, Thomas et al. 1991) studied the effect of injection rate on emulsion flooding for a Canadian and a
247
Venezuelan crude oil. The study was conducted using a porous media consisting of crushed Berea sandstone
248
packed in 5x30cm (diameter x length). The study employed a Lloydminster crude oil 16.4° API and 12o API
249
Morichal crude oils. The brines used for the runs and for the preparations of the emulsions had sodium chloride
250
concentrations of 3.3 and 7.5% by weight, respectively. The emulsions were prepared by adding 0.04% and
251
0.0004% by weight sodium hydroxide with pH = 12 and 10 respectively, to mixtures of crude oil and water. The
252
study revealed that water driven emulsion flooding may offer a viable alternative to thermal recovery of
253
moderately viscous oils.
RI PT
246
(Abdul and Ali 2003) carried out a study to examine the effective techniques that can better water-flood bottom
255
water reservoirs using polymer and emulsion as mobility control and/or blocking agents. In the provinces of
256
Alberta and Saskatchewan certain light and moderately heavy oil reservoirs have a high-water saturation zone in
257
connection with the oil zone. Using a conventional water-flood to produce from such reservoirs gives poor
258
performance. This is attributed to insufficient and incomplete sweep of the reservoir by the injected water, which
259
tend to move to the producing wells via those portions of the reservoir that have higher permeability. This leads to
260
low recovery. In this study, polymer was used to control the movement of water in the oil zone while the emulsion
261
was used to block the injected water from routing into the bottom water zone. The study found out that when
262
producing from reservoirs with water leg, the use of 10% quality oil-in-water emulsion as a blocking agent and
263
polymer solution as mobility control agent is the most successful strategy.
M AN U
TE D
264
SC
254
(Mandal, Samanta et al. 2010) investigated the efficiency of o/w emulsions as a displacement fluid during EOR
266
process. In the study, they used synthetic emulsions prepared by gear oil, and experiments were conducted using
267
sand pack flooding tests to observe the efficiency of the emulsion as displacing fluid. They found a substantial
268
additional recovery (more than 20% of original oil in place) over conventional water flooding.
AC C
EP
265
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
12
(Ashrafizadeh, Motaee et al. 2012) in a study of emulsification of heavy crude oil by surfactants reported
270
several findings on the application of emulsions in the oil industry. He reported the work of (Kessick and Denis
271
1982) on pipeline transportation of heavy crude oil. According to them, conventional pipelining is not suitable for
272
transporting heavy crudes from the reservoir to the refinery because of the high viscosities involved. This requires
273
alternative transportation techniques. (Saniere, Hénaut et al. 2004) in their study outlined several alternative
274
transportation methods that have been proposed. Among the techniques proposed, transporting such viscous crudes
275
as concentrated o/w emulsions is believed to be one of the most favorable ones (Poynter and Simon 1970, Marsden
276
and Raghavan 1973, Sifferman 1981).
277
Water-in-diesel emulsions (WiDE) has been studied and applied as fuel for regular diesel engines for the
278
reductions in the emissions of nitrogen oxides and particulate matters, which are both hazardous to our health, and
279
reduction in fuel consumption due to better burning efficiency (Lif and Holmberg 2006). This leads to
280
improvement in combustion efficiency when water is emulsified with diesel as a result of the micro-explosions,
281
which assist atomization of the fuel. Several studies (Lin and Wang 2003, Abu-Zaid 2004, Lif and Holmberg 2006,
282
Ghannam and Selim 2009, Alahmer, Yamin et al. 2010, Alahmer 2013, Fahd, Wenming et al. 2013, Ithnin, Noge et
283
al. 2014) have been conducted on the viability of diesel emulsion as an alternative fuel. Most of the studies pointed
284
to the fact that thermal efficiency is increased by using WiDE fuel compared to clean diesel fuel. Most of the
285
studies also agree that WiDE result in improvements in brake power, torque and specific fuel consumption
286
measurements when the total amount of diesel fuel in the emulsion is compared with that of the neat diesel fuel.
287
3. The Emulsification Process
TE D
M AN U
SC
RI PT
269
Crude oil emulsions form when oil and brine come into contact with each other, with the influence of sufficient
289
mixing, and in the presence of an emulsifying agent or emulsifier. The amount of mixing and the presence of
290
emulsifier are critical for the formation of an emulsion (Kokal and Wingrove 2000, Herrera 2012). Several sources
291
of mixing are available during the process of crude oil production, a factor frequently referred to as the amount of
292
shear. These include; Flow through reservoir rock, bottom-hole perforations/pump, flow through tubing; flow lines,
AC C
EP
288
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
13
and production headers, valves, fittings, and chokes, surface equipment, gas bubbles released because of phase
294
change etcetera (Fingas 1995, Kokal and Wingrove 2000, Langevin, Poteau et al. 2004) as indicated with letters A
295
to F on Fig. 2.
296
(Fingas, Fieldhouse et al. 1998, Langevin, Poteau et al. 2004, Fingas and Fieldhouse 2009) studied different
297
emulsions and opined that the amount of mixing depends on several near-unavoidable factors. High speed agitation
298
and shear causes vigorous mixing of oil and water and leads to smaller dispersed droplet sizes that are more stable.
299
This is, however as a result of the increased energy transferred for the break-up process which eventually lead to
300
small droplets and more stable emulsions. The sources responsible for this agitation may be present between the
301
time at which the oil enters the well and the time when the produced phases are separated at the surface (Jackson,
302
Harrington et al. 2012). Undoubtedly, certain methods of production contribute to the formation of emulsions.
304 305
Figure 2 A schematic diagram of crude oil flow from the reservoir to the storage tanks.
AC C
303
EP
TE D
M AN U
SC
RI PT
293
306
Although, there seems to be no universal theory that has been postulated for all emulsions, several theories
307
have been suggested to explain variations in emulsions formation processes (Lowe 1955).
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
14
308
According to (Clayton 1923, Becher 1988, Schramm 1992, Bhardwaj and Hartland 1994, Binks 2002, Fingas
309
2014, Umar, Saaid et al. 2017), many factors play different roles in the stabilization of emulsions, but the
310
significance of such roles vary even as they combine in a single emulsion. (Clayton 1923) presented various
311
theories for emulsions. We would mention few of such theories here in section 3.1.
All crude oils have four main constituents belonging to four broad classes of compounds. These are classified
313
as alkanes (also called saturates or aliphatics), aromatics, resins, and asphaltenes, SARA components. The
314
lower-molecular-weight compounds in crude oils are generally alkanes and aromatics, while Asphaltenes,
315
resins, and waxes (which are high-molecular-weight alkanes) account for the higher-molecular-weight
316
compounds. In a complex mixture like petroleum, all these compounds interact in such a way that all
317
components are maintained in the liquid oil phase. In other words, the lighter components of the oil act as
318
solvents for the higher molecular-weight compounds. As long as this solvency interaction is maintained in the
319
oil and thermodynamic conditions remain constant, the oil will remain stable. Should this equilibrium state be
320
changed, a point will be reached where the solvency strength of the oil is insufficient to maintain the heavy
321
components in solution, and as a result, they will precipitate out as solid particles. This is a frequent and
322
problematic occurrence during petroleum production, transportation, and storage (Griffith and Siegmund 1985,
323
Kawanaka, Leontaritis et al. 1989, Bobra 1991).
TE D
M AN U
SC
RI PT
312
3.1. The phase-volume theory.
325
This theory holds that, if small spheres of the same diameter are packed as closely as possible into a given space,
326
they will occupy 74·048 per cent of the available volume, irrespective of the size of the spheres This fact was
327
employed by Ostwald as the basis for a theory of emulsion, generally referred today as the "phase-volume theory."
328
According to Ostwald, 2 two types of emulsions are only possible over a certain range of concentration and that an
329
emulsion of one liquid in another was only possible when the volume concentration of the dispersed liquid was less
330
than 74 per cent, the double series being possible only over the range of 25·96 percent to 74·04 percent by volume.
AC C
EP
324
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
15
331 332 333
1.1. The Hydration Theory of Emulsions
334
liquid which would form the continuous phase is all used in the formation of a hydrated compound of the
335
emulsifying agent employed. Thus, substances such as acacia, soap, gelatin, casein, dextrin, and albumens are
336
considered to act as emulsifiers in virtue of their ability to form colloidal hydrated compounds. The emulsifying
337
efficiencies of these substances vary, since their "hydratability" varies qualitatively and quantitatively.
338
It is postulated by this theory that oil cannot be emulsified in a hydrated colloid until a certain minimum amount of
339
water is present; correspondingly, too much water presence (exceeding the amount used in hydrating the colloid),
340
makes the formation of stable emulsion impossible. It is reasonably accurate to emphasise the importance of
341
hydrophilic colloids in forming oil-in-water emulsions, but it is only reasonable to extend this and debate that oil-
342
soluble colloids (hydrophobic colloids) promote the formation of the water-in-oil type of emulsions.
343
3.2. Oriented wedge theory.
344
This theory has been developed from the work of Langmuir and Harkins (Clayton 1923). It postulates the manner
345
in which emulsions are stabilized. The theory is established upon the perception that the molecules of the
346
emulsifier orientate themselves in the interface between the dispersed and continuous phases, forming a wedge,
347
whose curvature determines the size of the dispersed phase.
348
3.3. The Adsorbed Film and Interfacial Tension Theory
349
At present, the Interfacial tension theory is probably the most universally accepted theory of emulsions formations.
350
Several works done by (Quincke 1889); in which he created emulsions from different oils in solutions of NaOH or
351
gum Arabic. He found out that the interfacial tensions between the oils and these solutions were lower than those
352
between the oils and pure water. Previous works (Langmuir 1917, Clayton 1923) had shown that oils containing
353
free fatty acids result to better emulsions in dilute solutions of borax or sodium carbonate than those created by
354
purer oils. (Quincke 1889), commenting on such works, recommended that the simplicity of emulsification differ
AC C
EP
TE D
M AN U
SC
RI PT
According to this theory proposed by Fischer (Finkle, Draper et al. 1923), emulsions can only be created if the
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
16
with the acidity and viscosity of the oil, the concentration of the alkaline solution, and the solubility in water of the
356
resulting soap. (Clayton 1923) holds that with this theory "emphasis is laid upon the fact that emulsification is
357
influenced by (1) the mass of the emulsifying agent present, (2) the ease with which this agent is adsorbed at the
358
interfacial separating surface, and (3) the nature of the ions adsorbed by the resultant film."
359
4. Mechanism of Emulsification
RI PT
355
Emulsification is a process of agitating two or more immiscible liquids, which result in heterogeneous systems,
361
consisting of at least one immiscible liquid intimately dispersed in another in the form of droplets, whose
362
diameters, generally exceeds 0.1 µm (Baloch and Hameed 2005). The emulsification process comprises of a certain
363
number of diverse chemical and physical processes and mechanisms, with many theories out forth to justify how
364
different emulsions are stabilized by the emulsifying agents. The emulsification history can begin right inside the
365
reservoir where the crude oil and water comingle and squeezed through constricted pores. When the crude oil is
366
produced from the well-head to the manifold (as shown in Fig. 2), there is usually a considerable pressure decrease
367
with a pressure gradient over chokes and valves where the mixing of oil and water can be intense (Sjöblom, Aske
368
et al. 2003).
M AN U
SC
360
As earlier discussed in the definitions of emulsions, they are thermodynamically unstable material systems
370
formed by at least two immiscible liquid phases, with one dispersed in the other(s). When such emulsions separate
371
into their different phases, there is reduction in the free energy of the system as a result of the large decrease in
372
interfacial area. However, the presence of a third component (referred to as a surfactant) in the erstwhile unstable
373
system makes the spontaneous formation of thermodynamically stable dispersions (Shahidzadeh, Bonn et al. 1999,
374
López-Montilla, Herrera-Morales et al. 2002). Two forms of emulsification processes are encountered and have
375
been reported in the literature; (a) Spontaneous emulsification and (b) self-emulsification.
AC C
EP
TE D
369
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
17
4.1. Spontaneous Emulsification
377
On the one hand, also called “True” Spontaneous emulsification, and it ensues when two immiscible liquids are
378
brought together, and they emulsify without the application of any form of external energy. The emulsification
379
may last for few minutes, or several days depending on the nature of liquids involved (Shahidzadeh, Bonn et al.
380
1999).
381
4.2. Self-Emulsification
382
On the other hand, emulsification in the industry is habitually accomplished with the aid of appropriate surface-
383
active agents, and is commonly called 'self-emulsification', although the emulsification process is assisted by
384
providing mechanical energy of some form, such as slight shaking, mixing (5) or sonication. In the case of self-
385
emulsifying systems, the free energy required to form the emulsion is either very low and positive or actually
386
negative (i.e., the formation is thermodynamically spontaneous) (Craig, Barker et al. 1995, Shahidzadeh, Bonn et
387
al. 1999).
388
5. Conditions necessary for Emulsion formation
389
All crude oils, whatever their origin contains certain characteristics which would likely make them emulsifiable
390
(Bansbach 1965). For emulsions to form, three conditions must be satisfied (Smith and Arnold 1992). These
391
conditions are (a) the two liquids forming the emulsion must be immiscible, (b) there must be sufficient agitation to
392
disperse one liquid as droplets in the other, and (c) the presence of an emulsifying agent (Becher 1988, Bobra,
393
Fingas et al. 1992, Smith and Arnold 1992, Fingas 2014).
TE D
M AN U
SC
RI PT
376
According to Hany et al., (Aziz, Darwish et al. 2002), for an emulsion to form, the system must have the
395
presence of water (brine), crude oil and sufficient agitation. (Becker 1997) documented that the formation of
396
emulsions requires; differences in solubility between the continuous phase and the dispersed phase, the existence of
397
intermediate agents having partial solubility in both phases and the presence of an energy source or sources,
398
sufficient enough to mix the phases.
AC C
EP
394
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
18
5.1. The Emulsifiers
400
Also, of paramount importance are the types of emulsifying agents or simply called emulsifiers. Emulsifiers are
401
associated with the produced crude oil. Since the nature and compositions of crude oils vary so widely, there exists
402
also a great variety of crude oil emulsifiers (Meyer 1964). To formulate concentrated stable emulsions, either oil-
403
in-water or water-in-oil type, a third substance is required apart from the two liquids. This substance is called an
404
emulsifying agent, or simply an emulsifier. The nature of the emulsifying agent determines what type of emulsion
405
forms (Clayton 1923). Thus, the lastingness (known as stability) of the emulsion is dependent upon the
406
rigorousness of the agitation and upon the emulsifying agents (Surfluh 1937).
407
(Roberts 1926) hold that the emulsifying agent responsible for the formation of petroleum emulsions is not
408
categorically known. However, in a sizable number of cases, it is believed to be colloidal asphalt, which includes
409
all asphalts and similar substances which occur in colloidal dispersion in crude oil. Since the nature and
410
compositions of crude oils vary so widely, there exists also a great variety of crude oil emulsifying agents (Meyer
411
1964) . These emulsifiers include asphaltic materials, “resinous substances, soluble organic acids, particles in the
412
ocean, particles found in crude oils including waxes and asphaltenes, particles found in sea water including
413
suspended sediments, dissolved surfactants which accumulate at the water/oil interface including metallic salts,
414
organic acids, organic bases and organometallics, and other tiny particles of solids, including products of corrosion
415
of the equipment involved or particles of the producing formation, in case of wells completed in unconsolidated
416
sands and sandy shales, are also the emulsifying agents contributing toward stability of the emulsions (Lee 1999).
417 418
The absence of these emulsifying agents in a crude oil can lead to the formation of a dispersion that will separate
419
quickly due to rapid coalescence of the dispersed droplets. However, the presence of these emulsifying agents in
420
the crude oil would lead to the formation of a very stable emulsion (Bobra 1992, Smith and Arnold 1992, Kokal
421
and Wingrove 2000, Gafonova and Yarranton 2001, Janssen, Noïk et al. 2001, Sjoblom 2001, Binks 2002, Kokal
422
2002, Sjöblom, Aske et al. 2003, Fingas and Fieldhouse 2004, Sjoblom 2005, Müller and Weiss 2007). These
AC C
EP
TE D
M AN U
SC
RI PT
399
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
19
natural emulsifiers form a mechanical film at the oil/water interface. The structural mechanical properties of the
424
natural crude oil emulsifiers in the interfacial layer surrounding the dispersed droplets are believed are very
425
important. This is the layer that provides resistance to coalescence in the final stage of emulsion breaking (Jones,
426
Neustadter et al. 1978). It is worthy of mention here that, understanding the chemical and physical properties of
427
these particles that reside at the interface is no doubt, key to understanding the emulsion breaking techniques. This
428
area is receiving more attention of recent. The authors of this paper intend to expound more on the effects of native
429
organic and inorganic solids on the stability of petroleum emulsions and how they can be included in emulsions
430
stability prediction models.
RI PT
423
431
(Gallup and Star 2004) in a study of Acidic crude oils identified that apart from their tendencies to cause scale
433
formation in production tubing or in surface installations, acidic crude oils also have high tendencies of forming
434
stable emulsions. The scale is often a mixture of calcium soaps associated with other minerals. Nigeria, on the
435
Afia field, Indonesia, on the Attaka field, Great Britain, on the Blake field, Norway, on the Heidrun field, Angola,
436
on the Kuito field, China, on the EDC field, Cameroon, on the Kita and Asoma fields. The acidity of crude by itself
437
is not a sufficient criterion. Some weakly acidic oils in Cameroon or in Indonesia may form stable emulsions while
438
other highly acidic crudes can be treated with no problem. It is the actual structure of the naphthenic acids that may
439
explain these differences in behaviors, hence the importance of characterizing the naphthenic acids of a crude oil.
440 441 442
5.1.1. Amphiphiles
443
(‘‘liking both’’), designating that they have some affinity for two fundamentally immiscible phases. The word
444
amphiphile was created by Paul Winsor 50 years ago (Paul and Moulik 1997). It emanates from two Greek roots.
445
The prefix ‘amphi’ means "double", "from both sides", "around", as in amphibian. Then the root philos which
446
expresses affinity, as in "philanthropist" (the friend of man), "hydrophilic" (compatible with water), or
447
"philosopher" (the friend of wisdom or science) (Salager 2002). Crude oil contains particles such as silica, clay,
TE D
M AN U
SC
432
AC C
EP
(Myers 1990) defined those substances that have chemical groups leading to surface activity as being amphiphilic
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
20
iron oxides; that are naturally hydrophilic, but can become oil-wet (hydrophobic) due to extended contact with the
449
crude oil in the absence of water. A decrease in the size of oil-wet particles results in an increase in W/O emulsion
450
stability. Emulsions with particles and asphaltenes combined can be much more stable than those stabilized by
451
asphaltenes alone, provided that enough asphaltenes are present: all the adsorption sites on the particle surface need
452
to be saturated by asphaltenes (Langevin, Poteau et al. 2004).
453
An amphiphilic substance exhibits a double affinity, which can be defined from the physico-chemical point of view
454
as a polar-apolar division. On the one hand, an amphiphiles has a polar group made up of heteroatoms such as
455
Oxygen (O), Sulphur (S), Phosphorus (P), or Nitrogen (N), incorporated in functional groups such as ether,
456
alcohol, ester, thiol, acid, sulfate, sulfonate, phosphate, amine, amide etc. Equally, it has an principally apolar
457
group which is a hydrocarbon chain of the alkyl or alkylbenzene type, sometimes with halogen atoms and even a
458
few non-ionized oxygen atoms (Salager 2002).
SC
RI PT
448
Asphaltenes and resins are among the natural amphiphiles found in crude oils. In an attempt to determine the
461
contribution of indigenous amphiphiles (the light, intermediate and the heavy ones) to emulsion stability, Dicharry
462
et al.,(Dicharry, Arla et al. 2006) evaluated and compared emulsion formed by different parts of substances. They
463
found out that the emulsions formed with the light and intermediate fractions separated immediately when the
464
agitation stopped. However, the most stable emulsions form with the fraction of crude that distilled at temperatures
465
greater than 520°C. This suggests that the amphiphiles with the highest molecular weight, i.e., resins and
466
asphaltenes, play a major role in the protection of water droplet against coalescence, thus making the emulsion
467
more stable. According to (Acevedo, Escobar et al. 1999, Yan, Elliott et al. 1999, Gu, Xu et al. 2002), the key role
468
of the heaviest amphiphilic materials in the crude oil is to stabilize the interface, while the lightest ones tend to
469
lower the emulsion stability. Due to its dual affinity, an amphiphilic molecule does not feel "at home" in any
470
solvent, whether it is polar or non-polar. This is because, there always exist one of the groups which "does not like"
471
the solvent environment. This is the reason amphiphilic molecules have a very strong tendency to migrate to
472
interfaces or surfaces and to adjust so that the polar group lies in water and the non-polar group is placed out of it,
AC C
EP
TE D
M AN U
459 460
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
21
473
and ultimately in oil. Amphiphiles have other properties other than tension lowering and this is why they are often
474
categorized based on their main use such as: soap, foaming agent, detergent, emulsifier, wetting agent, dispersant,
475
bactericide, corrosion inhibitor, antistatic agent, etc. In some cases they are known from the name of the structure
476
they are able to build, i.e. membrane, micro-emulsion, liquid crystal, liposome, vesicle or gel (Salager 2002).
477 5.1.2. Asphaltenes, Resins and Waxes as Emulsifiers
481
responsible for the formation of petroleum emulsions is not definitely known but, can be attributed to the presence
482
of colloidal asphalt, that including all asphalts and similar substances which occur in colloidal dispersion in crude
483
oil. Determining the type of an emulsion is very simple. If it is miscible with water, it is an emulsion of oil in
484
water; if miscible with oil, it is water dispersed in oil. Probably more than 95 percent of all oil field emulsions are
485
of the water in oil type (Wang, Zhang et al. 2004).
RI PT
478 479 480
M AN U
SC
(Roberts 1926) in a study on treating field emulsions in Mid-continent Field that the emulsifying agent
(McLean and Kilpatrick 1997) in an attempt to further investigate the effects of crude solvency and specific
487
resin–asphaltene interactions on emulsion stability, created model emulsions, using model oil formed by dissolving
488
varying amounts of resins and/or asphaltenes in a mixture of heptane and toluene. The resins and asphaltenes used
489
in this study were isolated from four different types—Arab Berri, Arab Heavy, Alaska North Slope, and San
490
Joaquin Valley. They found out that the prime factors governing the stability of these model emulsions were the
491
aromaticity of the crude medium, the concentration of asphaltenes, and the availability of solvating resins in the oil
492
(i.e., the resin/asphaltene or R/A ratio). The model emulsions were the most stable when the crude medium was
493
30–40% toluene and in many cases at small R/A ratios (i.e., R/A ≤1). This immensely supports the theory that
494
asphaltenes are the most effective in stabilizing emulsions when they are near the point of incipient precipitation.
495
The point of incipient precipitation, according to (Andersen and Speight 1992) is the point at which separation of
496
asphaltenes from a crude oil becomes apparent.
AC C
EP
TE D
486
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
22
(Sjöblom, Mingyuan et al. 1990b) in a study conducted to compare the destabilization of True petroleum
498
Emulsions from the Norwegian Continental Shelf and Model Systems. It was reported that True water-in-crude oil
499
emulsions are stabilized by a rigid interfacial film in which the surface-active material is accumulated, and that the
500
distinct components of this film seem, at least for the crude oils from the Norwegian continental shelf, to be
501
asphaltenes, waxes and other non-specified polar components. In addition, small wax particles are incorporated in
502
the film. On the other hand, inorganic particles such as clays have not been detected under laboratory conditions.
RI PT
497
Earlier before the works of Anderson and Speight, (Bridie, Wanders et al. 1980) investigated the roles of wax
505
and asphaltenes separately and in combination. In the study, a Kuwait 200+ fraction was first deasphaltenized
506
(thirty-fold dilutions with n-pentane) and then dewaxed. The dewaxing involves a six-fold dilution in a methyl
507
ethyl ketone/dichloromethane mixture 1/1 vol.). The asphaltenes fraction was recovered and kept under nitrogen to
508
prevent oxidation, and an emulsion of synthetic sea water (70% vol.) in the Kuwait 200 + fraction proper (30%
509
vol.) was prepared. The investigation revealed that, the de-asphaltenized, dewaxed oil did not form a stable
510
emulsion and had released 93% of its water content after standing for 15 min while the oil plus wax and
511
asphaltenes mixed to the original concentrations gave a stable emulsion.
M AN U
SC
503 504
512
(Kim, Boudh-Hir et al. 1990) investigated the role of asphaltene both in wettability reversal and as a surfactant.
514
The change in wettability is governed mainly by interfacial properties, with interfacial tension probably being the
515
most important property. When a rock surface comes in contact with crude oil, the surface of the rock can possibly
516
be modified due to asphaltene adsorption. This could alter the wettability of the rock. Whereas the polar segments
517
of an asphaltene molecule are oriented towards the surface, the non-polar portions are away from it, causing the
518
surface to be oil-wettable. It is a well-known fact that certain solids that possess dual wettability (i.e. are wetted by
519
both oil and water can play the role of emulsifiers (Sjöblom, Söderlund et al. 1990a, Bobra 1991, Becker 1997, Lee
520
1999, Vignati, Piazza et al. 2003, Sztukowski and Yarranton 2005, Al-Sahhaf, Fahim et al. 2009). Thus, when
AC C
EP
TE D
513
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
23
asphaltene adsorbs on such solids (when they come in contact with the crude oil), there is a high possibility of
522
modification of its wettability from dual wettability to single wettability.
523
(Salager 1990) in an investigation of the most effective mechanism for destabilization of W/O or O/W emulsion
524
reported that the removal of the surfactant from the water-oil interface by trapping it in a micro-emulsion is the
525
most effective destabilization mechanism. According to the study, these emulsion stabilizers have a polar part with
526
affinity to water and a nonpolar part with affinity to oil. These substances cannot fulfil this dual affinity, except
527
when they are located at the water/oil interface, with the polar part immersed in water and the nonpolar part in oil.
528
When they are adsorbed at the interface, they result to a decrease in the free energy of the system. Such include
529
naphthenic acids, resins, asphaltenes, etc.
RI PT
521
SC
530
A physicochemical study by (Bobra 1991) on the emulsification of water-in-oil emulsions reiterated the fact
532
that, the indigenous emulsifying agents are concentrated in the higher boiling fractions (boiling point > 370° C),
533
and predominantly in the residuum. It is largely accepted that asphaltenes, resins, and waxes play key roles in
534
emulsification, but specific mechanisms have not been clearly explained. These compounds are believed to be the
535
main constituents of the interfacial films that surround the water droplets contained in the emulsion. These films
536
have been shown to have high mechanical strength and therefore act as effective physical barriers, which prevent
537
droplet coalescence and in turn gives rise to the stable petroleum emulsions.
TE D
538
M AN U
531
(Sztukowski and Yarranton 2005) studied the stability of w/o emulsion with clays. In the study, heptane,
540
toluene, and asphaltenes were used as model fluids and native solids extracted from oilfield operations. They
541
established that a combination of asphaltene and fine solids (submicron scale) coverage produced the most stable
542
emulsions. They claim that fine solids compete with asphaltenes to adsorb at the interface and that a coverage of
543
the interface by asphaltenes between 60 to 80% and the remaining area covered by fine solids leads to the highest
AC C
EP
539
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
24
544
stability. Coarser solids (above 1 µm) can indeed stabilize emulsions, but only if they are in sufficiently high
545
concentration.
546
Figure 3 (a) Example of a hypothetical structure of asphaltene, among the many suggested, showing their aromatic character.
562
(b) Asphaltene structure deduced from microscopic and macroscopic analysis, showing their micro- and macro-molecular
563
bonding (Kawanaka, Leontaritis et al. 1989).
M AN U
SC
RI PT
547 548 549 550 551 552 553 554 555 556 557 558 559 560 561
(Bobra 1992) studied the emulsification of W/O emulsions, and the effects of wax, resin and asphaltenes. From
582
the studies, it was revealed that waxes cannot act as emulsifying agents by themselves but can act in combination
583
with resins or asphaltenes to produce stable oil-in-water emulsions. Thus, a concentration of 0.01 g/ml of
EP
TE D
564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581
AC C
Figure 4 Formation of water-in-oil emulsions (Lee 1999).
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
25
asphaltenes did not produce a stable water-in-oil emulsion, but when waxes were added (0.05 g/ml), stable
585
emulsions were formed. An asphaltene concentration of 0.03 g/ml, with no wax added, produced a stable emulsion.
586 587 588
(Bobra 1991) established that resins alone could act as effective emulsifiers, but the most stable emulsions were
589
produced when both asphaltenes and resins were present. It was suggested that waxes could interact with
590
asphaltenes and resins to stabilize emulsions. Stable emulsions are characterized by properties which prevent the
591
coalescence of their small water droplets (1 to 10 µm), while in unstable emulsions the larger water droplets
592
quickly coalesce as in Fig. 4.
RI PT
584
M AN U TE D
EP
Figure 5 (a) Schematic Diagram of dispersed water droplets in oil stabilized by asphaltenes, waxes and surfactants. An unstabilized region is shown where there is formation of an incomplete barrier. Modification by (Umar, Saaid et al. 2016)., from (Daling, Moldestad et al. 2003) (b) Modified from (Lee 1999).
(Daling, Moldestad et al. 2003) in a review of the major findings from laboratory studies and field trials conducted
AC C
594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617
SC
593
618
on the emulsification of oils spilled at sea, reported that among other factors, the precipitation of stabilizing agents
619
(asphaltenes, photo-oxidized compounds (resins) and in some crude oils precipitated waxes) leads to the formation
620
of stable W/O emulsions. The precipitated asphaltenes make an elastic ‘‘skin’’ between the water droplets and the
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
26
oil (see Fig. 5), leading to an increase in the stability of the emulsion- since the water droplets cannot coalesce and
622
drain so easily from the emulsion and the equilibrium will tend to favour emulsion formation. (Lee 1999) in a an
623
attempt to study the agents that promote and stabilize W/O emulsions reported that particles and surfactants found
624
in crude oil can act as emulsifying agents and thus can promote and stabilize water-in-oil emulsions. If particles
625
and surfactant concentrations are adequately high, then the coalescence of the water drops are prevented, leading to
626
stable emulsions (Fig. 5b).
627 628 629
Particles found in crude oils include waxes and asphaltenes, while particles found in sea water include suspended
630
sediments and/or particulates. Dissolved surfactants which accumulate at the water/oil interface include metallic
631
salts, organic acids, organic bases and organometallics. In oceans and during oil spills, particles in the ocean can
632
enter an oil slick and act as emulsifying agents.
633
(Bobra, Fingas et al. 1992) has advocated that asphaltenes resins and waxes must be in the form of finely divided
634
submicrometer particles before they can act as emulsifying agents.
635
According to (Filby and Van Berkel 1987), since the classification of asphaltenes and resins is an operational term,
636
i.e. they are defined based on their solubility in different solvents, there exist no clear difference between the
637
compounds found in the two fractions. Resin particles are mostly smaller than asphaltene particles and most of the
638
metal porphyrins are in the asphaltene fraction. Asphaltenes tend to have higher-molecular-weight compounds and
639
to be more polar than resins.
640
TE D
M AN U
SC
RI PT
621
(Lee 1995) disputed the fact that a direct correlation exists between the presence/concentration of asphaltene in
642
certain crude and the stability of the emulsion formed by that crude. In a study involving a Kuwait crude oil with
643
1.4% asphaltenes and TiaJuana crude oil with 3.1% asphaltenes, it was found that the Kuwait crude forms a more
644
stable emulsion than the TiaJuana crude, despite the fact that the Tiajuna crude contains a higher concentration of
645
asphaltene.
AC C
EP
641
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
27
(Jenkins, Grigson et al. 1991) carried out an empirical laboratory procedure to obtain information about the
647
different tendencies of six North Sea crude oils to form stable and highly viscous water-in-oil emulsions. They
648
found out that one crude (identified as crude A) had 1.6% asphaltenes and formed a very stable emulsion while a
649
second crude (crude B) had 1.03% asphaltenes and did not form stable emulsions. Thus, certain components of the
650
asphaltenes may play a critical role in emulsion formation. The amounts of these emulsifying agents in asphaltenes
651
are likely to vary for asphaltenes from different crude oils. However, several studies have established the
652
significance of asphaltenes, resins and waxes in promoting and stabilizing w/o emulsions.
653 654
(Brandvik 1991) in a study found that the stability of a water-in-oil emulsion was positively correlated with the
655
resin, wax and asphaltene content of the original crude oil. Also, in separate studies, (Sjöblom, Söderlund et al.
656
1990a, Ebeltoft, Børve et al. 1992, Sjöblom, Urdahl et al. 1992, Urdahl, Brekke et al. 1992, Umar, Saaid et al.
657
2017) observed that the exclusion of asphaltenes from crude oils by silica columns produced oils that did not form
658
water-in-oil emulsions.
M AN U
SC
RI PT
646
659
(Bridie, Wanders et al. 1980) found that after the removal of asphaltenes from Kuwait crude oil, very unstable
661
emulsions were produced. When wax crystals and asphaltenes were added back to the treated oil, a stable water-in-
662
oil emulsion was formed. Waxes cannot act as emulsifying agents by themselves but can act in combination with
663
resins or asphaltenes to produce stable oil-in-water emulsions. Thus, a concentration of 0.01 g/ml of asphaltenes
664
did not produce a stable water-in-oil emulsion, but when waxes were added (0.05 g/ml), stable emulsions were
665
formed (Bobra 1992, Bobra, Fingas et al. 1992).
EP
666
TE D
660
(Oliveira and Goncalves 2005) in a study on the rheology of emulsions held that the presence of W/O emulsions
668
may have a strong impact on the crude oil production, especially in offshore conditions. In such kind of systems,
669
the temperature of the crude oil varies widely along the flow from the reservoir to the platform storage tanks. For
670
example, in Campos basin, where most of the Brazilian crude oil is produced, typically the temperature of the oil
AC C
667
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
28
671
gradually decreases from 80 ºC at the bottom of the well-bore, located 3,000 m below the seabed, to about 60 ºC at
672
the top of the well-bore, located 1,000 m below the sea level, where the sea water temperature may vary from 4 ºC
673
to 10 ºC. In order to reach the storage tank, the crude oil has to flow for several hundred meters through a pipeline
674
in a cold environment. The contact with the cold seawater imposes a major decrease in the crude oil temperature;
675
hence crude oil arrival temperatures below 30 ºC have been frequently reported in some fields.
(McMahon 1992) studied the interfacial action of crude oil emulsions at the interface. He found out that in
678
certain waxy crude oils, the size of the wax crystal has a fundamental role on the stability of W/O emulsions. Data
679
obtained of the interfacial viscosity and other physical properties of the mixture show that the crystals form a
680
barrier at the W/O interface, which retards the coalescence of colliding water droplets. To associate with the
681
interface, wax, which is normally hydrophobic, has to acquire some affinity for the water phase, possibly by
682
adsorption of polar asphaltenes and resins from the crude oil. Studies with Octacosane (n-C28H58), a model crude
683
oil wax, show that limited wax/asphaltene/resin interactions do exist. However, the adsorbed layer does not confer
684
hydrophilicity to the surface of either Octacosane or real crude oil wax. Therefore, the effect of wax on emulsion
685
stability does not appear to be through action at the interface. Instead, wax may act in the bulk oil phase by
686
inhibiting film thinning between approaching droplets or by scavenging demulsifier. It is the asphaltene and resin
687
that were found to affect stability via interfacial action. They can adsorb in either dissolved or in solid form and
688
thereby inhibiting water separation. When wax crystals occur in the continuous phase, they usually act as emulsion
689
stabilizers. However, if they are present in the dispersed phase, such crystals may stick out through the interface,
690
leading to partial or complete droplet coalescence (Becker 1997, Rousseau 2000).
TE D
M AN U
SC
RI PT
676 677
(Mouraille, Skodvin et al. 1998) reported how naturally occurring surfactants in crude oils (mainly asphaltenes
693
and resins) are important for the stabilization of water-in-crude oil emulsions. According to a research reported, the
694
stability of emulsions at room temperature was mainly due to those surface-active fractions. It is crucial to gain a
695
better understanding of the mechanisms via which the stabilization processes of water-in-crude oil emulsions
AC C
EP
691 692
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
29
occur, so as to solve the emulsion problem more efficiently. In general, about 2/3rd of the world's crude oil is
697
produced in form of emulsions that must be treated (demulsified) before it can be marketed. These oilfield
698
emulsions are stabilized primarily by film-forming asphaltenes and resins containing organic acids and bases
699
(Strassner 1968). They are mostly stable and form spontaneously due to the presence of natural surfactants existing
700
in the crude oil phase. It is known that the viscosity of a w/o emulsion is strongly augmented by increasing its
701
water volume fraction and by decreasing the temperature. When w/o emulsions form, oil viscosity changes from a
702
few hundred mPa.s to about 100,000mPa.s (Selvarajan, Sivakumar et al. 2001, Ge, Yang et al. 2010, Wang and
703
Alvarado 2011, Fingas 2014, Fingas and Fieldhouse 2014).
704
6. Emulsion Stabilization Mechanisms
705
There are four principal mechanisms for the stabilization of emulsions (with cases where a combination of
706
mechanisms occurs). Certain emulsions may be weakly stabilized by the presence of adsorbed ions and non-
707
surface-active salts (a). The presence of colloidal sols partially wetted by both phases of the emulsion may form a
708
mechanical barrier to drop contact and coalescence (b). Many emulsions are stabilized by adsorbed polymer
709
molecules (c). Along with polymers, adsorbed surfactant molecules represent the most common stabilization
710
mechanism (d). These are as depicted in Fig. 6 below.
711 712 713
6.1.1. Surfactants
714
other hydrophobic (water disliking). The hydrophilic part (the head) of the surfactant molecule may be positive,
715
negative, neutral, or Zwitter ionic, and the hydrophobic part (tail) consists of one or more hydrocarbon chains,
716
usually with 6–22 carbon atoms (Migahed and Al-Sabagh 2009).
717 718
According to (Salager 2002), Surfactants are substances which exhibits some superficial or interfacial activity. It is
719
a short form for Surface-Active-Agents. Other languages such as Spanish, French or German do not have the word
720
"surfactant", but however describe these substances based on their characteristics to lower the surface or interfacial
TE D
M AN U
SC
RI PT
696
AC C
EP
Surfactants are amphiphilic molecules comprising of two dissimilar parts: one hydrophilic (water liking) and the
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
30
721
tension. For instance, the French would use tensioactif, German would use tenside, while Spanish would call it
722
tensioactivo.
This would suggest that surface activity is firmly the same to tension lowering, which is not absolutely general,
725
although it is true in many cases. It is worth mentioning that it is not all amphiphiles that display such activity. It is
726
only the amphiphiles with more or less equilibrated hydrophilic and lipophilic tendencies that are likely to migrate
727
to the surface or interface. It does not happen if the amphiphilic molecule is too hydrophilic or too hydrophobic, in
728
which case it stays in one of the phases.
RI PT
723 724
(Li, Guo et al. 2006) carried out a study on the formation of emulsions during chemical flooding (ASP) in Da
756
Qing and Sheng Li oil fields in China. In the study, partially hydrolyzed polyacrylamide (HPAM) was used as the
757
polymer, petroleum sulfonate (ORS-41 or TRS) as the surfactant, and sodium hydroxide (NaOH) or sodium
TE D
M AN U
SC
729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755
AC C
EP
Figure 6 Main emulsions stabilization mechanisms (Myers 1990).
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
31
carbonate (Na2CO3) as the alkaline component. Although, the technique yielded an increase in oil recovery of 15 to
759
20% compared with water-flooding, formation of stable w/o and o/w emulsions accompanied it. They found out
760
that the formation and properties of the crude emulsions formed in this technique are exceptionally complicated.
761
These emulsions do not only depend on the properties of the crude oil, the injection water and formation water, the
762
alkali, HPAM, and surfactant used, but also on the properties of the reservoir formed alkali–oil surfactant, the solid
763
particles from the reservoir among others.
RI PT
758
764 6.1.1.1. Surfactant Classifications
766
Surfactants can be classified commercially according to the uses they are put to in different industries. In the Oil
767
and Gas industry for instance, there is an increased used of surfactants in the formation of drilling fluids. In oil-
768
based drilling fluids, surfactants are used as emulsifiers and wetting agents. In water-based muds however, there is
769
a continually-growing diverse applications that include oil-in-water emulsification in base fluid formulations;
770
shale-swelling inhibitors to prevent wellbore instabilities, detergency to prevent cuttings sticking to drill bit,
771
defoaming additives to eliminate unwanted foam in water-based fluids; surfactant-polymer complexes for
772
enhanced properties in fluids for low-pressure reservoirs, etc. (Quintero 2002). Other applications of surfactants in
773
the oil and gas industry include: Gas/liquid systems; producing oil well and well-head foams, oil flotation process
774
froth, Liquid/liquid systems; emulsion drilling fluids (as explained above), Enhanced oil recovery in situ emulsions
775
(EOR), Well-head emulsions, Heavy oil pipeline emulsions, Fuel oil emulsions, etc (Schramm, Stasiuk et al. 2003,
776
Migahed and Al-Sabagh 2009). Classifications of surfactants based on their usage however, is not as important as
777
classifying them based on their dissociation in water (Salager 2002). Thus, based on their dissociation in water,
778
surfactants can be classified as:
EP
TE D
M AN U
SC
765
779 780 781 782
These types of Surfactants are dissociated in water in an amphiphilic anion, and a cation, that is commonly an
783
alkaline metal (Na+, K+) or a quaternary ammonium. They are the most universally used surfactants across many
AC C
• Anionic Surfactants
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
32
784
industries. They comprise alkylbenzene sulfonates (detergents), (fatty acid) soaps, lauryl sulfate (foaming agent),
785
di-alkyl sulfosuccinate (wetting agent), lignosulfonates (dispersants) etc. 50% of the world surfactants produced
786
are Anionic surfactants (Salager 2002). This moiety carries a negative charge, as in soap: C17H35COO- Na+, sodium
787
stearate (Becher 1988, Schramm, Stasiuk et al. 2003, Migahed and Al-Sabagh 2009).
788 789 790 791
These classes of surfactants are dissociated in water into an amphiphilic cation and an anion, most habitually of
792
the halogen type. These surfactants are in general more expensive than anionics, because of the high pressure
793
hydrogenation reaction to be carried out during their synthesis. As a consequence, they are only used in cases
794
where there is no cheaper substitute (Salager 2002, Migahed and Al-Sabagh 2009). The charge is positive, as in
795
quaternary ammonium salts: (C18H37)2N+(CH3)2Cl-, dimethyl dioctadecyl ammonium chloride (Schramm, Stasiuk
796
et al. 2003, Migahed and Al-Sabagh 2009).
M AN U
SC
RI PT
• Cationic Surfactants
797 798 799 800
There are situations where a single surfactant molecule exhibit both anionic and cationic dissociations. This
801
surfactant is called an amphoteric or a zwitterionic surfactant. Syhthetic products like betaines or sulfobetaines and
802
natural substances likes aminoacids and phospholipids exhibit this behavior (Salager 2002).
803
For these surfactants, solubilization is provided by the presence of positive and negative charge in the molecule, as
804
in C12H35N+(CH3)2CH2COO-, Ɓ-N-alkyl amino propionic acid (Schramm, Stasiuk et al. 2003, Migahed and Al-
805
Sabagh 2009).
TE D
• Amphoteric or Zwitterionic Surfactants
806 807 808 809
Nonionic Surfactants do not ionize in aqueous solution, because their hydrophilic group is of a non- dissociating
810
type. These comprise of groups like alcohol, phenol, ether, ester, or amide. They come as a close second with about
811
45% of the overall industrial production (Salager 2002). According to (Migahed and Al-Sabagh 2009), the
AC C
EP
• Non-Ionic Surfactants
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
33
812
solubility is provided by solvation of polyoxy ethylene oxide groups in water, such as C9H19C6H4(OCH2CH2)9OH,
813
nonyl phenol ethoxylate (Schramm, Stasiuk et al. 2003).
814 815 816 817 818
6.1.1.2. Surfactants Roles in Emulsion Stabilization
819
tension, increasing surface elasticity, increasing electric double layer repulsion (ionic surfactants), and possibly
820
increasing surface viscosity (Schramm, Stasiuk et al. 2003). Also, surfactant nature can control the arrangement of
821
the phases in an emulsion, that is, which phase will form the dispersed versus continuous phase. As discussed
822
earlier (under section 3), several experimental predictive methods based on anticipated surfactant positioning at the
823
interface exist (Schramm 2000, Dingcong 2002, Pasquali, Sacco et al. 2009). These include the Bancroft’s rule, the
824
oriented wedge theory, the hydrophile–lipophile balance (HLB), and the volume balance value (Dingcong 2002).
825
Among all the methods, the HLB has been the most widely used. The HLB dimensionless scale ranges from 0 to
826
20 for non-ionic surfactants; a low HLB (<9) refers to a lipophilic surfactant (oil soluble) and a high HLB (>11) to
827
a hydrophilic (water soluble) surfactant. Most ionic surfactants have HLB values greater than 20. Water-in-oil
828
(W/O) surfactants show HLB values in the range 3–8 while oil-in-water (O/W) emulsifiers possess HLB values of
829
about 8–18 (Schramm 2000, Pasquali, Sacco et al. 2009, Zafeiri, Horridge et al. 2017). Additionally, surfactant
830
exchanges between the interface and the bulk can drastically lower interfacial visco-elasticities (Powell, Damitz et
831
al. 2017).
• Surfactant Adsorption at Liquid-Liquid Interface
TE D
M AN U
SC
RI PT
The adsorption of surfactants at liquid interfaces can influence emulsion stability by lowering interfacial
832 833 834 835
Certain surfactants adsorb at a solid surface and by so doing, reduce interfacial tension and alters the ability of
836
water or oil to wet the solid surface. When the adsorbed surfactant positioning is in such a way that its hydrophobic
837
(water disliking) tail groups point away from the surface or along the surface, that will lead to a decrease in water-
838
wetting and an increase in oil-wetting. Similarly, if the positioning is with the polar head group away from the
AC C
EP
• Surfactants and Wettability Alteration
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
34
839
surface, there will be a resultant increase in water-wetting. An example of surfactant-induced wettability alteration
840
can be found in the treatment of swelling clays, such as montmorillonite, with a cationic surfactant, such as
841
dimethyl di(hydrogenated tallow) ammonium (Schramm 2000, Schramm, Stasiuk et al. 2003).
842
6.2. Roles of Solids in w/o Emulsion Stabilizations (Pickering) The subject of Pickering emulsions was first investigated by (Ramsden 1903)(Proc. Roy. Soc., 1903, 72, 156).
844
However, (Pickering 1907) was independently working on emulsification of solids, and only got to know about the
845
work of Ramsden after he has completed his work. Thus, the credit on Pickering emulsion is mostly given to
846
Pickering. An accumulation of continuous research in the past one century led to the recognition of distinctive
847
characteristics of Pickering emulsifiers compared with conventional emulsifiers, such as, irreversible interfacial
848
adsorption, exceptional stability against coalescence and Oswald ripening , the capability to stabilize emulsions
849
with enormous droplet size (up to several millimetres) or high internal phase, irregular rheological properties, etc.
850
(Dickinson 2012, Rayner, Marku et al. 2014, Xiao, Li et al. 2015).
M AN U
SC
RI PT
843
851
According to (Pickering 1907), the mixture of any insoluble liquid in water, where the water is broken up into
853
minute globules, like when it is forced through a syringe, the globules would remain emulsified permanently if the
854
water contains emulsifying agents. On mixing lime with paraffin and water, a kind of emulsion formed, which
855
either upsurges or descends in the excess of liquid, according to the proportions used.
856
However, describing the behaviour of the many substances that results to these different emulsions types would be
857
a tedious and unprofitable task. Thus, it is sufficient to briefly classify as those which give true emulsions, those
858
which give inadequate emulsions or quasi-emulsions, and those which do not emulsify at all.
859
This study established the fact that solids which are not adequately fine-grained to emulsify will, in most cases,
860
when present in significant amounts, form quasi-emulsions. Lime for instance forms a quasi-emulsion. Other
861
substances, including many recently formed precipitates, and, probably, all crystalline solids seem to be incapable
862
of forming even quasi-emulsions. This was the earliest documented results on Pickering emulsions, and this
AC C
EP
TE D
852
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
35
863
opened doors to further researches. (Clayton 1923) reported how finely-divided solids in certain instances can
864
promote emulsification of o/w or w/o emulsions. He found out that a North African argillaceous earth promptly
865
emulsified oils in water and could be used as a replacement for soap. (Alexander 1921) reported that emulsification is influenced by the size of the particles of the emulsifier, and that
867
the size of the emulsion droplets varied directly with the size of the particles of the emulsifying agent. He also
868
identified the ideal condition that for emulsions of oil in water the finely-divided solid emulsifying agent must be
869
more readily wetted by water than by oil while that of w/o should be more wetted by oil than water.
RI PT
866
(Briggs 1921) in a study of emulsions by finely divided solids showed that certain finely-divided solids, when
871
used together, might exert opposing emulsifying effects. For instance, adding 0·8g of carbon black (CB), an
872
amount sufficient to disperse 25 c.c. of water in 15 c.c. kerosene, to 0·1g of silica (350 mesh), no emulsion was
873
possibly formed. However, kerosene can be emulsified in a water suspension of silica, but if sufficient CB is
874
present, no emulsion is formed. Similarly, 1 part of mercuric iodide in 20 parts of silica will prevent the latter from
875
emulsifying 25 c.c. of kerosene in 25 c.c. of water.
M AN U
SC
870
(Mukerjee and Srivastava 1956) reported the action of colloidal clay as efficient emulsifying agents. According
877
to their findings, colloidal clay is capable of promoting the emulsification of o/w or of w/o emulsions. Such results
878
however had to be subjected to further investigation because as at that moment, what was understood was that a
879
given emulsifying agent only promotes one type of emulsion with any two given liquids to be emulsified. (Al-
880
Sahhaf, Fahim et al. 2009) while studying the factors that control emulsion stability in Burgan Oilfield Kuwait
881
reported that colloidal particles partially wetted by both the water and oil phases are capable of effectively
882
stabilizing emulsions.
EP
883
TE D
876
In separate studies, (Binks 2002, Binks, Clint et al. 2005, Binks and Rocher 2009) also established that colloidal
885
particles such as wax crystals can originate by direct solidification at the droplet interface, or previously formed
886
crystals can migrate and attach themselves to the interface. Colloidal particles like wax, silica, clay, iron oxide and
AC C
884
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
36
887
polymer lattices can provide kinetic stability to the dispersed phase of many oil-continuous emulsions via either the
888
presence of a particle network and/or interfacially-adsorbed colloids. The degree to which solids increases
889
emulsion stability depends on several factors such as particle size, shape and morphology, density, concentration,
890
and surface coverage, and wettability.
891 (Gelot, Friesen et al. 1984) investigated the effect of different combinations of finely divided solids and surface-
893
active agents on the stability of a w/o emulsion. In the study, they investigated the emulsification of w/o by the
894
clays (Ca−bentonite and Ca−kaolinite), as well as carbon black. The study revealed that by adding the surfactant
895
sodium dodecyl sulfate (SDS), the stability of the emulsion can be enhanced, and the wettability of the particles
896
changed. Thus, the principles that developed from this work and preceding works was that surface modification of
897
solid particles by adsorption of surface-active materials can modify the wettability of the particles and the stability
898
of the emulsions enhanced. (Finkle, Draper et al. 1923) are seemingly the pioneer researchers to link the three-
899
phase contact angle, (see Fig. 7 and 8) with the type of emulsion (O/W) or (W/O) stabilized by the solid particles.
900
According to them, the better-wetting liquid constitutes the continuous phase. (Reinders 1913) articulated three
901
important parameters that are some strong possibilities for the interfacial tension in a solid-liquid-liquid system;
902
γ12, γ13, γ23, where 1 and 2 denote the two liquids and 3 the solid. These possibilities are:
M AN U
SC
RI PT
892
1.
γ23>γ12+γ13, particle wetted completely by liquid 1;
904
2.
γ13>γ12+γ23, particle wetted completely by liquid 2;
905
3.
γ12>γ13+γ23, or γij>γik+γjk for all i≠j≠k, particle wetted partially by both liquids.
907
Only in case (3) will the particle tend to situate itself at the liquid-liquid interface.
EP
906
TE D
903
(Thompson, Taylor et al. 1985) demonstrated how wax particles and associated solids have considerable
909
influence on the emulsion stability of waxy North Sea crude. They found out that isolating the indigenous particles
910
from this oil inhibited oil’s tendency to form stable emulsions. (Bobra, Fingas et al. 1992) established that for
AC C
908
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
37
solids to act emulsifying agents, the particles must be very small compared to the droplet size of the emulsified
912
phase. They must accumulate at the interface and they must be “wetted” by both the oil and water phases.
913
(Monson 1969) in a study on chemical resolution of emulsions stated that depending on the specific characteristics
914
as geological age, chemical composition and other impurities, a wide range of materials can stabilize crude oil
915
emulsions. These include materials include finely-divided solids or mechanical stabilizers such as drilling mud
916
(Colloidal clay), produced sand, iron sulphide from pipe corrosion, precipitated minerals due to scale formation,
917
asphaltenes in the crude oil.
918 919
6.2.1. Pickering Stabilization Mechanism
RI PT
911
Several studies have been dedicated to the clarification of the mechanisms behind particle stabilization by
921
focusing on the influence of particle size, hydrophobicity, surface roughness and shape (Ngai and Bon 2014). The
922
phenomenon that solid particles can reside at the interface of droplets, thereby giving them some resistance against
923
coalescence or fusion, or Ostwald ripening, is known as Pickering stabilization (Bernardini 2015) (Ngai and Bon
924
2014). (Binks and Lumsdon 2000) reviewed some experimental findings concerning the stabilization of emulsions
925
by solid particles. They further described the preparation and properties of w/o emulsions stabilized by nanometer-
926
sized hydrophobic silica particles alone.
M AN U
TE D
927
SC
920
(Binks and Lumsdon 2000) reported, based on the works of (Abend, Bonnke et al. 1998, Lagaly, Reese et al. 1999,
929
Neuhäusler, Abend et al. 1999), at least two mechanisms by which colloidal particles stabilize emulsions
930
depending on the system. In the first mechanism, the particles are expected to adsorb at the oil/water interface and
931
stay there forming a dense monolayer or multilayer film around the dispersed droplets, thus hindering coalescence.
932
In the second, increased stabilization ensues when the particle-particle interactions are such that a three-
933
dimensional network of particles forms in the continuous phase surrounding the dispersed droplets. This has been
AC C
EP
928
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
38
934
cited mainly in clay-containing systems in which the emulsion oil drops become captured and largely immobilized
935
in the array of clay platelets in water.
936 (Kilpatrick 2012) suggested that the mechanism by which w/o emulsions are stabilized by inorganic solid particles
938
seems to be principally via the enhancement of asphaltene and/or resin or crude oil acid-stabilized emulsions by an
939
adsorption process of surface-modifying components in the crude oil to the particles that render them interfacially
940
active. There seems to be a limit to the surface coverage of inorganic particles that can effectively stabilize
941
micrometer-sized droplets, with particles in the tens to hundreds of nanometer size scale being most effective.
942
Figure 9 shows a schematic of surfactant molecule and a colloidal particle at oil-water interface. Surfactants are
943
amphiphilic molecules and they have a natural tendency to move to the oil-water interface. They decrease the oil-
944
water interfacial tension; and by so doing minimizing the energy required for emulsion formation. The adsorbed
945
surfactant molecules at the interface act as electrostatic or steric barriers against droplet coalescence thereby
946
increasing the emulsion stability. Hydrophilic-Lipophilic balance (HLB) of the surfactant molecules dictate the
947
nature of the emulsion formed; either O/W or W/O (Ramsden 1903, Pickering 1907, Clayton 1923, Binks 2002).
M AN U
SC
RI PT
937
948
Finely divided insoluble solid particles constitute an important class of emulsifying agents (Al-Sahhaf, Fahim et al.
950
2009) and behave in various ways like surfactant molecules, particularly if adsorbed to a fluid/fluid interface. Just
951
as the water or oil-liking tendency of a surfactant is quantified in terms of the hydrophile-lipophile balance HLB
952
number, so can that of a spherical particle be described in terms of its wettability via contact angle. Important
953
differences exist, however, between the two types of surface-active material, due in part to the fact that particles
954
are strongly held at interfaces (Binks 2002).
955
According to (Myers 1990), there are three conditions a solid must satisfy before it can play the role of an emulsion
956
stabilizer: (1) Particle size; In field operations, it is found that the stabilizer particles must be smaller than the
957
emulsion droplets, (2) the state of stabilizer particle dispersion; (i.e. in a state of incipient flocculation -that is, they
AC C
EP
TE D
949
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
39
should have partial colloidal stability in both liquids, otherwise their tendency to ‘‘reside’’ at the oil–water
959
interface will not be sufficiently strong for them to act as stabilizers, and (3) the comparative wettability of the
960
particles by each liquid component of the emulsion system; the solid must exhibit a significant contact angle at the
961
three-phase (oil–water–solid) contact line, usually as measured through the aqueous phase.
962
.
M AN U
963 964 965 966 967 968
SC
RI PT
958
Figure 7 (Left)Distribution of solid particles at water/oil interface (Bobra 1991). (Right) Particles positioning at oil/water interface (Binks 2002).
For maximum efficiency, the stabilizer usually should be preferentially wetted by the continuous phase (but not excessively so). (Gelot, Friesen et al. 1984, Tambe and Sharma 1993, Yan, Elliott et al. 1999, Aveyard, Binks et al.
970
2003) in separate studies establish that the extent to which solids increases emulsion stability depends on several
971
factors. Among these factors are particle size, shape of particles and morphology, particles density, concentration,
972
surface coverage, and wettability.
973
(Rousseau 2000) reviewed the effects of fat crystals in food emulsion formation and its stability. The study of
974
colloidal particles in food emulsions, particularly the role of fat crystals, is a more recent phenomenon, being first
975
examined in 1960s (Lucassen-Reynders and Tempel 1963). In quiet a number of emulsified foods (e.g. ice crystals
976
in ice cream, egg yolk particles in mayonnaise and fat particles in whipping cream) solid particles are necessary for
977
making them stable (Darling 1982). The role played by colloidal particles in the stabilization of emulsion is
978
receiving much attention, yet, the knowledge base is relatively scarce (Rousseau 2000). Some factors that are
AC C
EP
TE D
969
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
40
intimately related by inter-particle interactions and significantly affect fat crystal stabilization of emulsions ate
980
explained below.
M AN U
SC
RI PT
979
981 982 983 984 985
Figure 8 Adsorption and contact angles of fat crystals at the interface of an oil-in-water emulsion (Rousseau 2000).
986
of the crystals at the interface (Friberg, Larsson et al. 2003); (2) interfacial film rheology and (Lucassen-Reynders
987
1993); (3) polymorphism and morphology of the particle (particle structure) (Ogden and Rosenthal 1998); and (4)
988
location of fat crystals [(in the dispersed (O/W emulsion) or continuous phase (W/O emulsion)] (Darling 1982). All
989
of these factors are intimately related via inter-particle interactions (Wesdorp, Human et al. 1992).
990
(Mackay, McLean et al. 1973, Edwards and Wasan 1991) proposed that, the ability of an emulsion to oppose
991
coalescence will largely be determined by the properties of the interface. A highly viscous and rigid interfacial film
992
will retard the rate of film drainage and resist rupture thereby promotion.
993
(Wang and Alvarado 2011) in a research demonstrated how particle suspension contributes to emulsion stability. In
994
the study, Kaolinite and silica particle dispersions were characterized as functions of brine salinity using a
AC C
EP
TE D
The significant factors that determine the influence of fat crystals on emulsion stabilization are: (1) the wettability
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
41
reference water phase, as the reservoir brine, diluted with distilled water to obtain 10 and 100 times lower Total
996
Dissolved Solid (TDS) brine. Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) were employed
997
in examining the morphology and composition of the clays. The emulsions used in the studies were prepared by
998
mixing a crude oil with brine, with and without dispersed particles to investigate emulsion stability. The stability
999
was measured through the conventional bottle tests and optical microscopy. Results from the experiments show
1000
that both silica and kaolinite promote emulsion stability. Also, around 1 µm in size of kaolinite stabilizes emulsions
1001
more than does larger clay particles. A total reversal to this was observed with regards silica particles. Silica
1002
particles of bigger sizes (around 5 µm) produced more stable emulsions than smaller silica particles do.
1003
(Sztukowski and Yarranton 2005) inspected the role of solids in the stability of oil filed emulsions. They found that
1004
emulsion stabilized by fine solids and asphaltenes were most stable at a 2:1 fraction area ratio of asphaltene to
1005
solids. There is a strong correlation between asphaltene content and emulsion tightness.
SC
RI PT
995
M AN U
1006
(Binks and Rocher 2009) in a study on the effects of temperature on water-in-oil emulsions stabilized by wax
1008
microparticles claimed that micro-wax particles alone can stabilize emulsions. According to the authors, since wax
1009
particles are hydrophobic at the oil–water interface; such emulsions are water-in-oil. They found out that the
1010
stability of these emulsions at different temperatures to both sedimentation and coalescence depends significantly
1011
on whether particles are adsorbed to dispersed drop interfaces or they are not, prior to the temperature change.
1012
However, if the drops are formed at room temperature, increasing the temperature of the emulsion consequently
1013
leads to increase in the degree of coalescence as particles melt and cannot provide an obstruction to drop blending;
1014
the temperatures over which this occurs are in the same range as that of the melting range of the particles alone.
1015 1016
(Sharma, Velmurugan et al. 2015) conducted an EOR study, where oil-in-water Pickering emulsion stabilized by
1017
Nanoparticles was used in Combination with Polymer Flood. In this work, oil-in-water Pickering emulsion systems
1018
stabilized using nanoparticles, surfactant, and polymer were formulated and their efficiency tested for enhanced oil
1019
recovery with and without a conventional polymer flood. For the flooding experiments conducted, Berea core
AC C
EP
TE D
1007
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
42
samples at 13.6 MPa and temperatures of 313 and 353 K were used. The study found out that a combination of 0.5
1021
PV polymer flood with 0.5 PV Pickering emulsion was efficient and have yielded an additional 1–6% oil recovery
1022
as compared to 0.5 PV Pickering emulsion flooding alone.
SC
Figure 9 Schematic representation of (a) surfactant molecule (b) colloidal particle at oil-water interface (Katepalli 2014).
M AN U
1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038
RI PT
1020
(Yan, Gray et al. 2001) investigated the stability of w/o emulsions stabilized by fine solids with different
1040
hydrophobicities. They used model organic solvents like light mineral oil (Bayol-35), decane and toluene. The fine
1041
solids used in the study include hydrophilic and hydrophobic colloidal silica; kaolinite clay particles treated with
1042
asphaltenes, hydrophobic polystyrene latex microspheres, as well as fumed silica dry powders treated with
1043
silanization. Experimental results showed that hydrophilic colloidal silica could only produce o/w emulsion that is
1044
stable for a very short period of time. Using hydrophobic particles (either colloidal silica or polystyrene latex
1045
microspheres) that were suspended in the aqueous phase prior to emulsification produced only o/w emulsions.
1046
However, when such hydrophobic particles were suspended in organic phase prior to emulsification, stable w/o
1047
emulsions were formed, with dispersed water droplets as small as 2 mm when the solids were 12 nm in diameter.
1048
They found out that the stability of the produced emulsions studied depended on the hydrophobicity of the
1049
particles, and only particles with intermediate hydrophobicity produced very stable w/o emulsions.
AC C
EP
TE D
1039
1050
Although vast literatures on factors that affect emulsion stability exist, there is a shortage of work on inorganic
1051
and organic solids stabilized water-in-oil emulsion despite their importance (Al-Sahhaf, Fahim et al. 2009). The
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
43
authors believe that this extensive literature review would open more doors to those in the academia and the
1053
industry, especially that want to explore deeper into the issues of petroleum emulsions.
1054
7. Conclusions
1055
The formation of emulsions in the oil and gas industry is as old as the industry itself. These produced emulsions
1056
have posed serious operational and economic problems to the industry, justifying the economic and technical
1057
reasons for the resolution of these unwanted emulsions. Resolving emulsions require a detailed understanding and
1058
thorough research into not just the consequence of its formation, but the factors that prompt its formation and those
1059
that enhance its stabilization. Numerous studies have been conducted by researchers from the Industry and
1060
academia, and several factors have been experimented with respect to their roles in producing stable petroleum
1061
emulsions. Despite the vast literatures available, there is still a significant shortage of studies that deeply examine
1062
the roles of inorganic solids in stabilizing water-in-crude oil emulsions. From this review study, we found out that
1063
the concept of study adopted by most of the researchers that studied solids stabilized emulsions involve (1) Using
1064
processed solids in the study (2) preparing emulsions in the laboratory, rather than using field emulsions, and (3)
1065
inadequate knowledge on the properties of the solids – in the case of the few studies that have used field emulsions.
1066
To the best knowledge of the authors of this work, there is no study that holistically made use of solids from a field
1067
emulsion and explicitly characterized those solids, while examining their roles in stabilizing emulsions. Hence the
1068
authors of this work focus on native solids from field emulsions (both organic and inorganic), holistically
1069
understand their properties and roles in stabilizing petroleum emulsions and predict the type of emulsion that the
1070
presence of these solids may form. It is believed that understanding the compositions, behaviors and properties of
1071
these solids (that reside at the o/w interface) is fundamental in understanding the nature, severity and type of
1072
petroleum emulsions, as well as a key in developing cost-effective demulsification strategy. From the details of the
1073
papers reviewed by the authors of this paper, they believe that tackling the issue of undesirable emulsions,
1074
especially, requires a closer investigation into the problem. Due to the peculiarity of every oilfield emulsions
1075
(because of the varying factors responsible for its formation), containing the behavior of these complex mixtures is
AC C
EP
TE D
M AN U
SC
RI PT
1052
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
44
no easy task. Perhaps the best way to visualize such complex emulsions is to identify the physical and chemical
1077
properties of not just the organic emulsifiers, but also of the inorganic solids which we believe are very significant
1078
in making the emulsion more difficult to treat. As mentioned, emulsion treatment has always been more of an art
1079
than science, with many such chemicals selected based on trial and error. This we believe should be replaced with
1080
a more scientific approach to the problem, where the demulsifiers are tailored based on the exact properties of the
1081
emulsifying agents. Hence, it is important to understand the nature of the solids that stabilize the emulsions at a
1082
molecular, microscopic and macroscopic level. Also, to obtain an adequate prediction model that can predict the
1083
nature and severity of petroleum emulsions, the solids that are produced together with the crude oil should be
1084
included in the prediction model. The authors of this paper have conducted series of laboratory studies as part of
1085
an extensive study that would go a long way in tackling the problem of emulsion treatment in the oil and gas
1086
industry.
1087
Acknowledgements
1088
The authors wish to acknowledge Universiti Teknologi PETRONAS, Malaysia for providing us with state-of-the-
1089
art equipment for this study. Also, Deleum Chemicals Sdn Bhd Malaysia, PETRONAS Research Sdn Bhd (PRSB)
1090
Malaysia, Vision Petroleum Sdn Bhd, Malaysia for providing us with production data and field emulsions.
TE D
M AN U
SC
RI PT
1076
1091
References
1093
Abdul, H. and S. Ali (2003). "Combined polymer and emulsion flooding methods for oil reservoirs with a water leg." Journal of Canadian
1095 1096 1097
Petroleum Technology 42(02).
Abend, S., N. Bonnke, U. Gutschner and G. Lagaly (1998). "Stabilization of emulsions by heterocoagulation of clay minerals and layered
AC C
1094
EP
1092
double hydroxides." Colloid & Polymer Science 276(8): 730-737. Abidin, A., T. Puspasari and W. Nugroho (2012). "Polymers for enhanced oil recovery technology." Procedia Chemistry 4: 11-16.
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
1098 1099
45
Abu-Zaid, M. (2004). "Performance of single cylinder, direct injection diesel engine using water fuel emulsions." Energy Conversion and Management 45(5): 697-705.
1100
Acevedo, S., G. Escobar, M. A. Ranaudo, J. Khazen, B. Borges, J. C. Pereira and B. Méndez (1999). "Isolation and characterization of low and
1101
high molecular weight acidic compounds from Cerro Negro extraheavy crude oil. Role of these acids in the interfacial properties of the
1102
crude oil emulsions." Energy & Fuels 13(2): 333-335.
1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122
RI PT
1107
recovery implication." Energy & Fuels 26(8): 4655-4663.
Ahmadi, M. A. and S. R. Shadizadeh (2013). "Implementation of a high-performance surfactant for enhanced oil recovery from carbonate reservoirs." Journal of Petroleum Science and Engineering 110: 66-73.
Ahmadi, M. A. and S. R. Shadizadeh (2013). "Induced effect of adding nano silica on adsorption of a natural surfactant onto sandstone rock:
SC
1106
Ahmadi, M. A. and S. R. Shadizadeh (2012). "Adsorption of novel nonionic surfactant and particles mixture in carbonates: enhanced oil
experimental and theoretical study." Journal of Petroleum Science and Engineering 112: 239-247.
Ahmadi, M. A. and S. R. Shadizadeh (2016). "Adsorption of a nonionic surfactant onto a silica surface." Energy Sources, Part A: Recovery, Utilization, and Environmental Effects 38(10): 1455-1460.
M AN U
1105
kinetic and isotherm methods." Journal of Dispersion Science and Technology 36(3): 441-452.
Al-Sahhaf, T. A., M. A. Fahim and A. M. Elsharkawy (2009). "Effect of inorganic solids, wax to asphaltene ratio, and water cut on the stability of water-in-crude oil emulsions." Journal of Dispersion Science and Technology 30(5): 597-604. Alahmer, A. (2013). "Influence of using emulsified diesel fuel on the performance and pollutants emitted from diesel engine." Energy conversion and management 73: 361-369.
Alahmer, A., J. Yamin, A. Sakhrieh and M. Hamdan (2010). "Engine performance using emulsified diesel fuel." Energy Conversion and Management 51(8): 1708-1713.
TE D
1104
Ahmadi, M. A. and S. Shadizadeh (2015). "Experimental and theoretical study of a new plant derived surfactant adsorption on quartz surface:
Alexander, J. (1921). "The Zone of Maximum Colloidality. 1 Its Relation to Viscosity In Hydrophile Colloids, Especially Karaya Gum And Gelatin. 2 (Preliminary Paper.)." Journal of the American Chemical Society 43(3): 434-440. Andersen, S. and J. Speight (1992). Asphaltene Precipitation and Incipient Flocculation In Mixed-Solvents. Abstracts Of Papers Of The American Chemical Society, Amer Chemical Soc 1155 16th St, Nw, Washington, DC 20036.
EP
1103
1123
API (1961). "History of Petroleum Engineering." API Journal, Division of Production.
1124
Ashrafizadeh, S., E. Motaee and V. Hoshyargar (2012). "Emulsification of heavy crude oil in water by natural surfactants." Journal of
1126 1127
Petroleum Science and Engineering 86: 137-143.
AC C
1125
Aveyard, R., B. P. Binks and J. H. Clint (2003). "Emulsions stabilised solely by colloidal particles." Advances in Colloid and Interface Science 100: 503-546.
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
46
1128 1129 1130 1131 1132 1133
Aziz, H. M. A., S. F. Darwish and F. M. Abdeen (2002). Downhole Emulsion Problem, The Causes and Remedy, Ras Budran Field. SPE Asia Pacific Oil and Gas Conference and Exhibition, Society of Petroleum Engineers. Baloch, M. K. and G. Hameed (2005). "Emulsification of oil in water as affected by different parameters." Journal of colloid and interface science 285(2): 804-813. Bansbach, P. L. (1965). Treating emulsions produced by thermal recovery operations. SPE California Regional Meeting, Society of Petroleum Engineers. Becher, P. (1988). Encyclopedia of Emulsion Technology, Vol. 3, Basic Theory, Measurement and Applications, Dekker, New York.
1135
Becker, J. (1997). Crude oil waxes, emulsions, and asphaltenes, Pennwell Books.
1136
Bernardini, C. (2015). "Particle-Stabilized Emulsions and Colloids: Formation and Applications." Johnson Matthey’s international journal of
1138 1139 1140 1141
research exploring science and technology in industrial applications: 298.
Bhardwaj, A. and S. Hartland (1994). "Kinetics of coalescence of water droplets in water-in-crude oil emulsions." Journal Of Dispersion Science and technology 15(2): 133-146.
SC
1137
RI PT
1134
Binks, B. and S. Lumsdon (2000). "Catastrophic phase inversion of water-in-oil emulsions stabilized by hydrophobic silica." Langmuir 16(6): 2539-2547.
Binks, B. P. (2002). "Particles as surfactants—similarities and differences." Current opinion in colloid & interface science 7(1): 21-41.
1143
Binks, B. P., J. Clint, G. Mackenzie, C. Simcock and C. Whitby (2005). "Naturally occurring spore particles at planar fluid interfaces and in
1144 1145 1146
emulsions." Langmuir 21(18): 8161-8167.
M AN U
1142
Binks, B. P. and A. Rocher (2009). "Effects of temperature on Water-in-Oil Emulsions Stabilized solely by wax microparticles." Journal of colloid and interface science 335(1): 94-104.
Bobra, M. (1991). Water-in-oil emulsification: a physicochemical study. International Oil Spill Conference, American Petroleum Institute.
1148
Bobra, M. (1992). A study of water-in-oil emulsification, Consulthem.
1149
Bobra, M., M. Fingas and E. Tennyson (1992). "When oil spills emulsify." CHEMTECH;(United States) 22(4).
1150
Brandvik, D. (1991). "W/O-emulsion formation and W/ O-Emulsion stability testing: An extended study with eight oil types.".
1151
Bridie, A., T. H. Wanders, W. Zegveld and H. Van der Heijde (1980). "Formation, prevention and breaking of sea water in crude oil emulsions ‘chocolate mousses’." Marine Pollution Bulletin 11(12): 343-348.
EP
1152
TE D
1147
Briggs, T. (1921). "Emulsions with finely divided solids." Industrial & Engineering Chemistry 13(11): 1008-1010.
1154
Clayton, W. (1923). The theory of emulsions and emulsification, J. & A. Churchill.
1155
Craig, D., S. Barker, D. Banning and S. Booth (1995). "An investigation into the mechanisms of self-emulsification using particle size analysis
1156 1157 1158
AC C
1153
and low frequency dielectric spectroscopy." International journal of pharmaceutics 114(1): 103-110. Daling, P. S., M. Ø. Moldestad, Ø. Johansen, A. Lewis and J. Rødal (2003). "Norwegian testing of emulsion properties at sea––the importance of oil type and release conditions." Spill Science & Technology Bulletin 8(2): 123-136.
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
47
1159
Darling, D. F. (1982). "Recent advances in the destabilization of dairy emulsions." Journal of Dairy Research 49(4): 695-712.
1160
Dicharry, C., D. Arla, A. Sinquin, A. Graciaa and P. Bouriat (2006). "Stability of water/crude oil emulsions based on interfacial dilatational
1162 1163 1164 1165 1166 1167 1168 1169
rheology." Journal of colloid and interface science 297(2): 785-791. Dickinson, E. (2012). "Use of nanoparticles and microparticles in the formation and stabilization of food emulsions." Trends in Food Science & Technology 24(1): 4-12. Dingcong, W. (2002). "A study of identifying the emulsion type of surfactant: Volume balance value." Journal of colloid and interface science 247(2): 389-396.
RI PT
1161
Ebeltoft, H., K. N. Børve, J. Sjöblom and P. Stenius (1992). Interactions between poly (styrene-allylalcohol) monolayers and surfactants. Correlations to water-in-crude oil emulsion stability. Advances in Colloid Structures, Springer: 131-139.
Edwards, D. and D. Wasan (1991). "A micromechanical model of linear surface rheological behavior." Chemical engineering science 46(5-6): 1247-1257.
Fahd, M. E. A., Y. Wenming, P. Lee, S. Chou and C. R. Yap (2013). "Experimental investigation of the performance and emission
1171
characteristics of direct injection diesel engine by water emulsion diesel under varying engine load condition." Applied energy 102: 1042-
1172
1049.
1174 1175 1176
Filby, R. H. and G. J. Van Berkel (1987). Geochemistry of metal complexes in petroleum, source rocks, and coals: an overview, ACS
M AN U
1173
SC
1170
Publications.
Fingas, M. (1995). "Water-in-oil emulsion formation: A review of physics and mathematical modelling." Spill Science & Technology Bulletin 2(1): 55-59.
Fingas, M. (2014). Handbook of Oil Spill Science and Technology, John Wiley & Sons.
1178
Fingas, M. (2014). Handbook of oil spill science and technology, Chp 8, John Wiley & Sons.
1179
Fingas, M. (2014). New Models for Water-in-Oil Emulsion Formation. International Oil Spill Conference Proceedings, American Petroleum
1180
Institute.
TE D
1177
1181
Fingas, M. and B. Fieldhouse (2003). "Studies of the formation process of water-in-oil emulsions." Marine pollution bulletin 47(9): 369-396.
1182
Fingas, M. and B. Fieldhouse (2004). "Formation of water-in-oil emulsions and application to oil spill modelling." Journal of hazardous
1184 1185
materials 107(1): 37-50.
EP
1183
Fingas, M. and B. Fieldhouse (2009). "Studies on crude oil and petroleum product emulsions: Water resolution and rheology." Colloids and Surfaces A: Physicochemical and Engineering Aspects 333(1): 67-81. Fingas, M. and B. Fieldhouse (2014). "Water-in-oil emulsions: formation and prediction." Handbook of Oil Spill Science and Technology: 225.
1187
Fingas, M., B. Fieldhouse and J. Mullin (1998). "Studies of water-in-oil emulsions: stability studies." Oceanographic Literature Review 6(45):
1188
AC C
1186
1018.
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
48
1189 1190
Fingas, M., B. Fieldhouse and J. Mullin (1999). "Water-in-oil emulsions results of formation studies and applicability to oil spill modelling." Spill Science & Technology Bulletin 5(1): 81-91.
1191
Fink, J. (2015). Petroleum engineer's guide to oil field chemicals and fluids, Gulf Professional Publishing, Chp 23; pp 705.
1192
Finkle, P., H. D. Draper and J. H. Hildebrand (1923). "The theory of emulsification1." Journal of the American Chemical Society 45(12): 2780-
1193
2788. Friberg, S., K. Larsson and J. Sjoblom (2003). Food emulsions, CRC Press.
1195
Gafonova, O. V. and H. W. Yarranton (2001). "The stabilization of water-in-hydrocarbon emulsions by asphaltenes and resins." Journal of
1197 1198 1199 1200 1201 1202
Colloid and Interface Science 241(2): 469-478.
Gallup, D. L. and J. Star (2004). Soap sludges: aggravating factors and mitigation measures. SPE International Symposium on Oilfield Scale, Society of Petroleum Engineers.
Ge, X., J. Yang, X. Xu and J. Gao (2010). "The demulsification of crude emulsion of ASP flooding by an organic silicone demulsifier." Petroleum Science and Technology 28(10): 1013-1024.
SC
1196
RI PT
1194
Gelot, A., W. Friesen and H. Hamza (1984). "Emulsification of oil and water in the presence of finely divided solids and surface-active agents." Colloids and surfaces 12: 271-303.
Ghannam, M. and M. Selim (2009). "Stability behavior of water-in-diesel fuel emulsion." Petroleum Science and Technology 27(4): 396-411.
1204
Griffith, M. and C. Siegmund (1985). Controlling compatibility of residual fuel oils. Marine Fuels, ASTM International.
1205
Gu, G., Z. Xu, K. Nandakumar and J. Masliyah (2002). "Influence of water-soluble and water-insoluble natural surface active components on
1206
M AN U
1203
the stability of water-in-toluene-diluted bitumen emulsion." Fuel 81(14): 1859-1869.
1207
Herrera, M. (2012). Analytical techniques for studying the physical properties of lipid emulsions, Springer Science & Business Media.
1208
Islam, M. and S. Ali (1989). "New scaling criteria for polymer, emulsion and foam flooding experiments." Journal of Canadian Petroleum
1212 1213 1214 1215 1216 1217 1218 1219
TE D
1211
Israelachvili, J. (1994). "The science and applications of emulsions—an overview." Colloids and Surfaces A: Physicochemical and engineering aspects 91: 1-8.
Ithnin, A. M., H. Noge, H. A. Kadir and W. Jazair (2014). "An overview of utilizing water-in-diesel emulsion fuel in diesel engine and its potential research study." Journal of the Energy Institute 87(4): 273-288.
EP
1210
Technology 28(04).
Jackson, J., R. Harrington and D. Manko (2012). Emulsion Tendency Studies--Understanding Method, Inhibitors And Water Cut. CORROSION 2012, NACE International.
Janssen, P., C. Noïk and C. Dalmazzone (2001). Emulsion formation in a model choke-valve. SPE Annual Technical Conference and Exhibition,
AC C
1209
Society of Petroleum Engineers.
Jenkins, R., S. Grigson and J. McDougall (1991). The formation of emulsions at marine oil spills and the implications for response strategies. SPE Health, Safety and Environment in Oil and Gas Exploration and Production Conference, Society of Petroleum Engineers.
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
1220 1221
49
Jones, T., E. Neustadter and K. Whittingham (1978). "Water-in-crude oil emulsion stability and emulsion destabilization by chemical demulsifiers." Journal of Canadian Petroleum Technology 17(02).
1222
Katepalli, H. (2014). "Formation and stability of emulsions: Effect of surfactant-particle interactions and particle shape."
1223
Kawanaka, S., K. Leontaritis, S. Park and G. Mansoori (1989). Thermodynamic and colloidal models of asphaltene flocculation, ACS
1224
Publications. Kessick, M. A. and C. E. S. Denis (1982). Pipeline transportation of heavy crude oil, Google Patents.
1226
Kilpatrick, P. K. (2012). "Water-in-crude oil emulsion stabilization: Review and unanswered questions." Energy & Fuels 26(7): 4017-4026.
1227
Kim, S., M. Boudh-Hir and G. Mansoori (1990). The Role of Asphaltene in Wettability Reversal. SPE Annual Technical Conference and
1228 1229 1230
Exhibition, Society of Petroleum Engineers.
RI PT
1225
Kokal, S. (2002). Crude oil emulsions: A state-of-the-art review. SPE Annual Technical Conference and Exhibition, Society of Petroleum Engineers. Kokal, S. (2008). "Crude oil emulsions: everything you wanted to know but were afraid to ask."
1232
Kokal, S. and M. Wingrove (2000). Emulsion separation index: From laboratory to field case studies. SPE Annual Technical Conference and
1233
SC
1231
Exhibition, Society of Petroleum Engineers.
Kokal, S. L. (2005). "Crude oil emulsions: A state-of-the-art review." SPE Production & facilities 20(01): 5-13.
1235
Lagaly, G., M. Reese and S. Abend (1999). "Smectites as colloidal stabilizers of emulsions: I. Preparation and properties of emulsions with
1237 1238 1239 1240
smectites and nonionic surfactants." Applied Clay Science 14(1): 83-103.
Langevin, D., S. Poteau, I. Hénaut and J. Argillier (2004). "Crude oil emulsion properties and their application to heavy oil transportation." Oil & gas science and technology 59(5): 511-521.
Langmuir, I. (1917). "The constitution and fundamental properties of solids and liquids. II. Liquids." Journal of the American Chemical Society 39(9): 1848-1906.
TE D
1236
M AN U
1234
Leal-Calderon, F. and V. Schmitt (2008). "Solid-stabilized emulsions." Current Opinion in Colloid & Interface Science 13(4): 217-227.
1242
Lee, R. F. (1995). "Isolation and identifcation of compounds and mixture which promote and stabilize water-in-oil emulsions.".
1243
Lee, R. F. (1999). "Agents which promote and stabilize water-in-oil emulsions." Spill Science & Technology Bulletin 5(2): 117-126.
1244
Li, M., J. Guo, B. Peng, M. Lin, Z. Dong and Z. Wu (2006). "Formation of crude oil emulsions in chemical flooding." Surfactant science series
1245
132: 517-547.
EP
1241
Li, M., M. Lin, Z. Wu and A. A. Christy (2005). "The influence of NaOH on the stability of paraffinic crude oil emulsion." Fuel 84(2): 183-187.
1247
Li, M., M. Xu, M. Lin and Z. Wu (2007). "The effect of HPAM on crude oil/water interfacial properties and the stability of crude oil
1248 1249
AC C
1246
emulsions." Journal of dispersion science and technology 28(1): 189-192. Lif, A. and K. Holmberg (2006). "Water-in-diesel emulsions and related systems." Advances in colloid and interface science 123: 231-239.
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
50
1250 1251 1252 1253
Lin, C.-Y. and K.-H. Wang (2003). "The fuel properties of three-phase emulsions as an alternative fuel for diesel engines☆." Fuel 82(11): 1367-1375. López-Montilla, J. C., P. E. Herrera-Morales, S. Pandey and D. O. Shah (2002). "Spontaneous emulsification: mechanisms, physicochemical aspects, modeling, and applications." Journal of dispersion science and technology 23(1-3): 219-268. Lowe, B. (1955). "Experimental cookery, from the chemical and physical standpoint."
1255
Lucassen-Reynders, E. (1993). "Interfacial viscoelasticity in emulsions and foams." Food Structure 12(1): 1.
1256
Lucassen-Reynders, E. H. and M. V. D. Tempel (1963). "Stabilization of Water-In-Oil Emulsions by Solid Particles1." The Journal of Physical
1258 1259 1260 1261
Chemistry 67(4): 731-734.
Mackay, G., A. McLean, O. Betancourt and B. Johnson (1973). "Formation of water-in-oil emulsions subsequent to an oil spill." Institute of Petroleum, Journal of 59(568).
Mandal, A., A. Samanta, A. Bera and K. Ojha (2010). Role of oil-water emulsion in enhanced oil recovery. Chemistry and Chemical Engineering (ICCCE), 2010 International Conference on, IEEE.
SC
1257
RI PT
1254
Manning, F. S. and R. Thompson (1991). "Oilfield processing."
1263
Marsden, S. and R. Raghavan (1973). "A system for producing and transporting crude oil as an oil/water emulsion." J. Inst. Pet 59: 273-278.
1264
McClements, D. J. (2008). "Lipid-based emulsions and emulsifiers." Food Lipid Chemistry, Nutrition and Biotechnology.
1265
McClements, D. J. (2015). Food emulsions: principles, practices, and techniques, CRC press.
1266
McLean, J. D. and P. K. Kilpatrick (1997). "Effects of asphaltene aggregation in model heptane–toluene mixtures on stability of water-in-oil
1269 1270 1271 1272 1273 1274 1275
McMahon, A. J. (1992). Interfacial Aspects of Water-in-Crude Oil Emulsion Stability. Emulsions—A Fundamental and Practical Approach, Springer: 135-156.
Mendoza, H., S. Thomas and S. Ali (1991). Effect of injection rate on emulsion flooding for a Canadian and a venezuelan crude oil. Annual
TE D
1268
emulsions." Journal of Colloid and Interface Science 196(1): 23-34.
Technical Meeting, Petroleum Society of Canada.
Meyer, P. (1964). Chemelectric Treating A New Phase In The Electrical Dehydration Of Oil Emulsions. SPE Production Automation Symposium, Society of Petroleum Engineers.
Migahed, M. and A. Al-Sabagh (2009). "Beneficial role of surfactants as corrosion inhibitors in petroleum industry: a review article." Chemical
EP
1267
M AN U
1262
Engineering Communications 196(9): 1054-1075. Monson, T. (1969). Chemical resolution of emulsions In: Surface operations in petroleum production, II, Elsevier.
1277
Mouraille, O., T. Skodvin, J. Sjöblom and J.-L. Peytavy (1998). "Stability of water-in-crude oil emulsions: role played by the state of solvation
1278 1279
AC C
1276
of asphaltenes and by waxes." Journal of dispersion science and technology 19(2-3): 339-367. Mukerjee, L. and S. Srivastava (1956). "Finely divided solids as emulsifiers—Part I." Colloid & Polymer Science 147(3): 146-152.
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
51
1280
Müller, F. H. and A. Weiss (2007). Emulsions, Steinkopff.
1281
Myers, D. (1990). Surfaces, interfaces and colloids, Wiley-Vch New York etc.
1282
Neuhäusler, U., S. Abend, C. Jacobsen and G. Lagaly (1999). "Soft X-ray spectromicroscopy on solid-stabilized emulsions." Colloid &
1283
Polymer Science 277(8): 719-726.
1284
Ngai, T. and S. A. Bon (2014). Particle-stabilized emulsions and colloids, Royal Society of Chemistry.
1285
Ogden, L. G. and A. J. Rosenthal (1998). "Interactions between fat crystal networks and sodium caseinate at the sunflower oil-water interface."
1288 1289 1290 1291 1292
RI PT
1287
Journal of the American Oil Chemists' Society 75(12): 1-7. Oliveira, R. and M. Goncalves (2005). Emulsion rheology-theory vs. field observation. Offshore Technology Conference, Offshore Technology Conference.
Opawale, A. O. and S. O. Osisanya (2013). Tool for Troubleshooting Emulsion Problems in Producing Oilfields. SPE Production and Operations Symposium, Society of Petroleum Engineers.
Pasquali, R. C., N. Sacco and C. Bregni (2009). "The studies on hydrophilic–lipophilic balance (HLB): sixty years after William C. Griffin’s pioneer work (1949–2009)." Lat Am J Pharm 28(2): 313-317.
SC
1286
Paul, B. K. and S. P. Moulik (1997). "Microemulsions: an overview." Journal of Dispersion science and Technology 18(4): 301-367.
1294
Pickering, S. U. (1907). "Cxcvi.—Pickering Emulsions." Journal of the Chemical Society, Transactions 91: 2001-2021.
1295
Powell, K. C., R. Damitz and A. Chauhan (2017). "Relating emulsion stability to interfacial properties for pharmaceutical emulsions stabilized
1296
M AN U
1293
by Pluronic F68 surfactant." International Journal of Pharmaceutics 521(1): 8-18.
1297
Poynter, W. G. and R. Simon (1970). Pipelining oil/water mixtures, Google Patents.
1298
Quincke, G. (1889). "On the physical properties of thin solid laminæ."
1299
Quintero, L. (2002). "An overview of surfactant applications in drilling fluids for the petroleum industry." Journal of dispersion science and technology 23(1-3): 393-404.
TE D
1300 1301
Ramsden, W. (1903). “Separation of Solids in the Surface-Layers of Solutions and Suspensions” (Observations on Surface-Membranes,
1302
Bubbles, Emulsions, and Mechanical Coagulation).--Preliminary Account." Proceedings of the royal Society of London 72: 156-164.
1303
Rayner, M., D. Marku, M. Eriksson, M. Sjöö, P. Dejmek and M. Wahlgren (2014). "Biomass-based particles for the formulation of Pickering
1305 1306
type emulsions in food and topical applications." Colloids and Surfaces A: Physicochemical and Engineering Aspects 458: 48-62.
EP
1304
Reinders, W. (1913). "Die Verteilung eines suspendierten Pulvers oder eines kolloid gelösten Stoffes zwischen zwei Lösungsmitteln." Colloid & Polymer Science 13(5): 235-241.
Roberts, C. H. (1926). "Use of treating compounds for oil field emulsions in the mid-continent field." Transactions of the AIME(01): 321-334.
1308
Rousseau, D. (2000). "Fat crystals and emulsion stability—a review." Food Research International 33(1): 3-14.
1309
Salager, J.-L. (1990). "The fundamental basis for the action of a chemical dehydrant. Influence of the physical and chemical formulation on the
1310
AC C
1307
stability of an emulsion." International Chemical Engineering 30(1): 103-116.
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
52
1311
Salager, J.-L. (2002). "Surfactants types and uses." FIRP booklet(E300A).
1312
Saniere, A., I. Hénaut and J. Argillier (2004). "Pipeline transportation of heavy oils, a strategic, economic and technological challenge." Oil &
1313
Gas Science and Technology 59(5): 455-466.
1314
Schramm, L. L. (1992). Petroleum emulsions, ACS Publications.
1315
Schramm, L. L. (2000). Surfactants: fundamentals and applications in the petroleum industry, Cambridge University Press.
1316
Schramm, L. L., E. N. Stasiuk and D. G. Marangoni (2003). "2 Surfactants and their applications." Annual Reports Section" C"(Physical
1319 1320 1321 1322 1323
RI PT
1318
Chemistry) 99: 3-48. Selvarajan, R., A. Sivakumar and R. A. Marble (2001). Aqueous dispersion of an oil soluble demulsifier for breaking crude oil emulsions, Google Patents.
Shahidzadeh, N., D. Bonn, O. Aguerre-Chariol and J. Meunier (1999). "Spontaneous emulsification: relation to microemulsion phase behaviour." Colloids and Surfaces A: Physicochemical and Engineering Aspects 147(3): 375-380.
Sharma, T., N. Velmurugan, P. Patel, B. Chon and J. Sangwai (2015). "Use of oil-in-water pickering emulsion stabilized by nanoparticles in
SC
1317
combination with polymer flood for enhanced oil recovery." Petroleum Science and Technology 33(17-18): 1595-1604. Sheng, J. (2014). "Critical review of low-salinity waterflooding." Journal of Petroleum Science and Engineering 120: 216-224.
1325
Sifferman, T. R. (1981). Method of transporting viscous hydrocarbons, Google Patents.
1326
Singh, P., W. H. Thomason, S. Gharfeh, L. D. Nathanson and D. J. Blumer (2004). Flow properties of Alaskan heavy-oil emulsions. SPE
1327
M AN U
1324
Annual Technical Conference and Exhibition, Society of Petroleum Engineers. Sjoblom, J. (2001). Encyclopedic handbook of emulsion technology, CRC Press.
1329
Sjoblom, J. (2005). Emulsions and Emulsion Stability: Surfactant Science Series/61- Chp 14, CRC Press.
1330
Sjöblom, J., N. Aske, I. H. Auflem, Ø. Brandal, T. E. Havre, Ø. Sæther, A. Westvik, E. E. Johnsen and H. Kallevik (2003). "Our current
1331
understanding of water-in-crude oil emulsions.: Recent characterization techniques and high pressure performance." Advances in Colloid
1332
and Interface Science 100: 399-473.
1334 1335 1336
Sjöblom, J., L. Mingyuan, H. Höiland and E. J. Johansen (1990b). "Water-in-crude oil emulsions from the Norwegian continental shelf part III. A comparative destabilization of model systems." Colloids and Surfaces 46(2): 127-139. Sjöblom, J., H. Söderlund, S. Lindblad, E. Johansen and I. Skjärvö (1990a). "Water-in-crude oil emulsions from the Norwegian continental
EP
1333
TE D
1328
shelf." Colloid & Polymer Science 268(4): 389-398. Sjöblom, J., O. Urdahl, K. C. N. Børve, L. Mingyuan, J. O. Saeten, A. A. Christy and T. Gu (1992). "Stabilization and destabilization of water-
1338
in-crude oil emulsions from the Norwegian continental shelf. Correlation with model systems." Advances in colloid and Interface Science
1339
41: 241-271.
1340 1341
AC C
1337
Smith, H. V. and K. E. Arnold (1992). "Crude oil emulsions." Petroleum engineering handbook. 3rd ed. Richardson: Social of Petroleum Engineers: 19.11-19.34.
ACCEPTED MANUSCRIPT
Abubakar Abubakr Umar et al/ 00 (2017) 000–000
1342 1343 1344 1345
53
Standnes, D. C. and I. Skjevrak (2014). "Literature review of implemented polymer field projects." Journal of Petroleum Science and Engineering 122: 761-775. Strassner, J. (1968). "Effect of pH on interfacial films and stability of crude oil-water emulsions." Journal of Petroleum Technology 20(03): 303-312.
1346
Surfluh, J. (1937). Prevention of Oil-Field Emulsions. Drilling and Production Practice, American Petroleum Institute.
1347
Sztukowski, D. M. and H. W. Yarranton (2005). "Oilfield solids and water-in-oil emulsion stability." Journal of colloid and interface science
1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372
RI PT
1353
Journal of colloid and interface science 157(1): 244-253.
Thompson, D., A. Taylor and D. Graham (1985). "Emulsification and demulsification related to crude oil production." Colloids and Surfaces
SC
1352
Tambe, D. E. and M. M. Sharma (1993). "Factors controlling the stability of colloid-stabilized emulsions: I. An experimental investigation."
15: 175-189.
Umar, A., I. Saaid and A. Sulaimon (2017). The Roles of Polar Compounds in the Stability and Flow Behavior of Water-in-Oil Emulsions. ICIPEG 2016, Springer: 643-653.
M AN U
1351
prospects." Journal of Petroleum Science and Engineering 120: 202-215.
Umar, A. A., I. B. Saaid, A. A. Sulaimon, M. H. R. O. Abdullah, Y. H. Min, N. A. M. Bashar and S. M. F. S. A. Nasir (2016). Rheological and stability study of water-in-crude oil emulsions. AIP Conference Proceedings, AIP Publishing.
Umar, A. A. and I. B. M. Saaid (2013). "Silicate Scales Formation During ASP Flooding: A Review." Research Journal of Applied Sciences, Engineering and Technology 6: 1543-1555.
Urdahl, O., T. Brekke and J. Sjöblom (1992). "13C nmr and multivariate statistical analysis of adsorbed surface-active crude oil fractions and the corresponding crude oils." Fuel 71(7): 739-746.
TE D
1350
Talebian, S. H., R. Masoudi, I. M. Tan and P. L. J. Zitha (2014). "Foam assisted CO 2-EOR: a review of concept, challenges, and future
Vignati, E., R. Piazza and T. P. Lockhart (2003). "Pickering emulsions: interfacial tension, colloidal layer morphology, and trapped-particle motion." Langmuir 19(17): 6650-6656.
Wang, X. and V. Alvarado (2011). "Kaolinite and silica dispersions in low-salinity environments: Impact on a water-in-crude oil emulsion stability." Energies 4(10): 1763-1778.
EP
1349
285(2): 821-833.
Wang, Y., L. Zhang, T. Sun, S. Zhao and J. Yu (2004). "A study of interfacial dilational properties of two different structure demulsifiers at oil– water interfaces." Journal of colloid and interface science 270(1): 163-170. Wesdorp, L., H. Human and S. Bruin (1992). "Modeling and control of the product structure of food emulsions." Advances in food engineering.
AC C
1348
Boca Raton, Fla.: CRC Press. p: 409-427. Xiao, J., C. Li and Q. Huang (2015). "Kafirin Nanoparticle-Stabilized Pickering Emulsions as Oral Delivery Vehicles: Physicochemical Stability and in Vitro Digestion Profile." Journal of agricultural and food chemistry 63(47): 10263-10270.
Abubakar Abubakar Umar et al ACCEPTED MANUSCRIPT
54
1373 1374 1375 1376 1377 1378
Yan, N., M. R. Gray and J. H. Masliyah (2001). "On water-in-oil emulsions stabilized by fine solids." Colloids and Surfaces A: Physicochemical and Engineering Aspects 193(1): 97-107. Yan, Z., J. A. Elliott and J. H. Masliyah (1999). "Roles of various bitumen components in the stability of water-in-diluted-bitumen emulsions." Journal of colloid and interface science 220(2): 329-337. Zafeiri, I., C. Horridge, E. Tripodi and F. Spyropoulos (2017). "Emulsions Co-Stabilised by Edible Pickering Particles and Surfactants: The Effect of HLB Value." Colloid and Interface Science Communications 17: 5-9.
RI PT
1379 1380
AC C
EP
TE D
M AN U
SC
1381
ACCEPTED MANUSCRIPT
Highlights
RI PT
SC M AN U TE D
EP
The formation and stabilization of petroleum emulsions remain a serious problem in the oil and gas industry. Increase in solids concentrations lead to an increase in the emulsion stability. The irreversible adsorption of solids has a major consequence on the long-term stability Solids sizes play significant roles in improving emulsion stability. The stability of these emulsions in the oil industry has been a fundamental issue that necessitates continuous research. This paper provides details of the petroleum emulsions in the oil and gas industry.
AC C