Investigating almond seed oil as potential biodiesel-based drilling mud

Journal of Petroleum Science and Engineering 181 (2019) 106201

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Investigating almond seed oil as potential biodiesel-based drilling mud a,b,c

a,∗

a,b

Jeffrey O. Oseh , M.N.A. Mohd Norddin , Issham Ismail , Abdul R. Ismail Afeez O. Gbadamosia,c, Augustine Agia, Shadrach O. Ogirikic a b c

a,b

,

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Department of Petroleum Engineering, School of Chemical and Energy Engineering, Universiti Teknologi Malaysia, 81310, Johor Bahru, Malaysia Malaysia Petroleum Resources Corporation Institute for Oil and Gas (MPRC-UTM), Universiti Teknologi Malaysia, 81310, Johor Bahru, Malaysia Department of Chemical and Petroleum Engineering, College of Engineering, Afe Babalola University, Ado-Ekiti, P.M.B. 5454, Ekiti State, Nigeria

ARTICLE INFO

ABSTRACT

Keywords: Biodegradation Biodiesel Diesel Sweet almond seed oil Rheology Shale swelling

With increasing strict environmental laws, there is a need for operators to design a benign oil-based muds (OBMs). In this study, oil extracted from non-edible sweet almond seed (SASO) was used as the continuous phase to formulate biodiesel-based drilling mud (BBDM). Different properties of the BBDM including the economic viability were evaluated and compared with those of the diesel OBM to determine the applicability of these properties for drilling fluids and their level of toxicity to the environment. The results indicate that the rheology, filtration properties, electrical stability, thermal stability and shale swelling inhibition performance of the BBDM are comparable with those of the diesel OBM. The biodiesel has a significantly higher flash point of 169 °C than the diesel with 78 °C; demonstrating that it can supply better fire safety than the diesel. The data of the toxicity test indicate SASO to be safer and less harmful compared to diesel #2 type used. After the 28-day period of biodegradation tests, the BBDM and the diesel OBM showed 83% and 25.2% aerobic biodegradation with Penicillium sp., respectively. The low branching degree and absence of aromatic compounds in the BBDM contributes for its higher biodegradation. The economic evaluation of the BBDM indicates low cost of formulation and waste management. The general outcome of the tests illustrates that SASO has the potentials of being one of the technically and environmentally feasible substitutes for the diesel OBM.

1. Introduction Increasing demand for energy from non-renewable resources like oil and gas is driving the petroleum industry to search for novel resources in deeper formations, and unexplored areas (Harvey, 2010; Zhong et al., 2019; Nanthagopal et al., 2019). Drilling muds are circulating fluids used in a rotary drilling to perform different tasks, such as cooling and lubricating the drill string to minimize wear, balancing the formation pressure, transmitting downhole information to the surface for interpretation in the form of signals from the drilled well, maintaining wellbore stability, and circulating drilled cuttings from the wellbore to the surface (Ismail et al., 2016; Kafashi et al., 2017; Gbadamosi et al., 2018; Hakim et al., 2018; Boyou et al., 2019; Oseh et al., 2019a, b). Over the years, two major types of drilling muds used in drilling operations are water-based muds (WBMs) and invert emulsion drilling muds (IEDMs) (containing oil-based muds (OBMs) and synthetic-based muds (SBMs)) (Sayindla et al., 2017; Oseh et al., 2018; Zhong et al., 2019; Nanthagopal et al., 2019). Owing to the lower ecological effect and lower operating cost, WBMs are widely used. However, operators

∗

may have to consider tailored IEDMs to drill reactive shale formations, high pressure high temperature (HPHT) formations, deeper drilling depths and directional drillings (especially in Extended-Reach Drilling Wells) where the drill string is continually in contact with the wellbore wall. IEDMs, especially OBMs formulated with petrol-diesel or mineral oils exhibit better thermal stability, lower torque and drag, better wellbore geomechanical stability, and enhanced drilling efficiency compared with WBMs, which offset their added cost (Sulaimon et al., 2017; Li et al., 2018; Nanthagopal et al., 2019). Despite its higher efficiency, application of OBM formulated with petrol-diesel or mineral oils has been seriously restricted by increasingly strict environmental laws in recent years. This is largely due to the adverse effects of their toxic effluents on the environments. To resolve this issue, ester-based muds (EBMs) were developed. Sulaimon et al. (2017) synthesized EBMs from crude palm oil and investigated their properties for the formulation of biodegradable drilling mud. They reported that the operational performance of the formulated EBMs was comparable to those of diesel OBMs and mineral OBMs, and have reduced adverse effects on the ecosystem. In the past

Corresponding author. E-mail address: [email protected] (M.N.A. Mohd Norddin).

https://doi.org/10.1016/j.petrol.2019.106201 Received 4 March 2019; Received in revised form 20 June 2019; Accepted 21 June 2019 Available online 26 June 2019 0920-4105/ © 2019 Elsevier B.V. All rights reserved.

Journal of Petroleum Science and Engineering 181 (2019) 106201

J.O. Oseh, et al.

three decades, EBMs faced their first field trials in Norwegian offshore and were successful in numerous environmentally sensitive formations, such as Australia (Eckhout et al., 2000), North Sea (Peresich et al., 1991) and Gulf of Mexico (Burrows et al., 2001). Nonetheless, many esters utilized today in formulating EBMs are produced from chemicals. Therefore, they have higher operational costs than diesel OBMs and mineral OBMs, making their full utilization for drilling fluids limited (Ismail et al., 2001; Sulaimon et al., 2017; Li et al., 2018). In addition, EBMs have numerous drilling issues ranging from the unstable wellbore at challenging environments and poor thermal stability. Their viscosities are also difficult to control and they are susceptible to hydrolysis either in acidic or alkaline medium. These issues have also increased their limitations. Operators are in search of a lower cost, more technically dependable and high-properties performance ester source to be used as additive to formulate non-aqueous based drilling muds for enhanced drilling operations. Recently, biodiesel was introduced as a substitute for diesel OBMs and mineral OBMs. Biodiesel simply can be referred to as the monoalkyl esters of long-chain fatty acids obtained from renewable oils or fats from plant or animal source (Wang et al., 2012; Sun et al., 2013; Li et al., 2016a, b; Yadav et al., 2017; Li et al., 2018). In terms of chemical configuration, biodiesel can function as the external phase of drilling mud as it provides all the environmental and technical advantages of conventional EBMs (Ismail et al., 2001; Li et al., 2016b; Sulaimon et al., 2017). Biodiesel's are produced from sources, such as edible sugars and starches, non-edible plant materials, algae and other microbes which are non-toxic and biodegradable (Li et al., 2016a, b; Wang et al., 2017). Utilising non-edible oils as base oils to formulate biodiesel-based drilling mud (BBDM) can provide better waste management of oil rig drilling effluents and the protection of the ecosystem. Comparative studies of BBDM conducted with synthetic OBMs either of ester or mono-alkyl ester of fatty acids for drilling fluids shows that biodiesel has comparable properties with conventional petrol-diesel (Wang, 2013; Li et al., 2016a, b; Wang et al., 2017; Fakharany et al., 2017a, b). Li et al. (2016a, b) found that designed BBDM from waste cooking oil has comparable basic properties with that of the conventional petroldiesel. The biodiesel has a high flash point, acceptable elastomeric material property, remarkable biodegradability and non-toxicity. A previous study reported that Jatropha oil-based IEDM had a lower coefficient of friction, thereby indicating a higher lubricating property of the mud than that of the petrol-diesel OBM (Paswan et al., 2016). In addition, the Jatropha oil-based IEDM had a lower formation damage effect and high shale recovery performance compared to the diesel OBM. Fakharany et al. (2017a, b) also found that biodiesel formulated from Jatropha oil and soybean oil has a higher flash point and better electrical stability than those of petrol-diesel. Thus far, IEDMs formulated from biodiesel exhibits desirable and sterling operational properties comparable to diesel OBMs. This study proposed the use of almond seed oil to function as an external phase of BBDM substitutes for conventional petrol-diesel OBMs and mineral OBMs. Almond seeds are one of the oil-bearing plants for the production of biodiesel and they belong to the Rosaceae family (Ogunsuyi and Daramola, 2013; Giwa and Ogunbona, 2014). Sweet almond seed (Prunus amygdalus “dulcis”) is reported to contain approximately 51% lipid, 19% protein, 18% carbohydrate and 12% fibre (Giwa and Ogunbona, 2014). The oil content of sweet almond seed is about 35–60% (Giwa and Ogunbona, 2014; Akubude and Nwaigwe, 2016). The non-edible oil derived from sweet almond seed wastes has been utilized in Bioenergy production (Akubude and Nwaigwe, 2016). A study conducted revealed that plants wastes and by-products are costeffective alternatives to advance biodiesel production (Giwa and Ogunbona, 2014). Several studies carried out showed almond seed wastes can be used as absorbents to remove metals and dyes, and also for the production of activated carbons dyes (Ogunsuyi and Daramola, 2013; Akubude and Nwaigwe, 2016). More importantly, they are obtained at low-cost from various processing industries and their wastes

can be effective for biodiesel production (Ogunsuyi and Daramola, 2013). Therefore, non-edible seed oil from almond seed can also be used for biodiesel production as the continuous phase in BBDM just like the Jatropha seed oil (Paswan et al., 2016). This study, therefore, used a non-edible seed oil from sweet almond seed (SASO) as the continuous phase to formulate a BBDM for drilling operations. The formulated BBDM system was characterized and its fatty acid compositions and basic properties were evaluated. In addition, the microscopic and macroscopic organization, rheology, filtration characteristics, electrical stability, thermal stability, shale swelling inhibition performance, eco-toxicity, and biodegradability of the BBDM were evaluated and compared with those of the petrol-diesel. Some discussion on the results was provided and an economic evaluation study of the newly-designed BBDM was also presented. 2. Experimental 2.1. Materials For the base oil, matured sweet almond seeds were obtained from Sabongari market, Kano, Nigeria. All chemicals like potassium hydroxide (KOH), methanol, sodium hydroxide (NaOH), sulphuric acid (H2SO4), hydrochloric acid, ethanol and n-hexane were all obtained from Sigma Aldrich (Merck, Germany). Commercial grade of No. 2 diesel test fuel (diesel #2) was used as the base oil for the formulation of diesel-OBM and it was obtained from a local supplier (Forte OilSpring, Abuja, Nigeria). The specification data sheet (SDS) number of the diesel #2 product is: 100000013879 and it conform to the American Society for Testing Materials (ASTM) (ASTM D975, Grade No. 2-D S500) Specifications. The flow process used to produce the BBDM and determination of its properties is shown in Fig. 1. 2.2. Procedures for production of SASO biodiesel 2.2.1. Oil extraction 2 kg of the sweet almond seeds were collected and sun-dried for 48 h and oven-dried for 2 h at 100 °C. The dried seeds were crushed into powder using a blending machine. The resultant powder was stored in a cool and dry conditions in preparation for oil extraction. Solvent extraction method with n-hexane was used to extract 1 kg of the lipid components of the milled sweet almond seeds at 60 °C for 6 h until the extraction was finished. Rotary vacuum evaporator at 60 °C under controlled pressure was used to remove the solvent from the oil. Oil yield was determined from difference in weight of the dried seeds sample before and after extraction. The free fatty acid content of the extracted oil was determined. As shown in Fig. 1, fatty acid methyl ester (FAME) was produced from SASO by a two-step transesterification process using methanol. The use of methanol in the transesterification process is beneficial because the product glycerol can be separated at the same time during the transesterification process. The end products of the transesterification process are raw glycerol and the raw biodiesel. 2.2.2. Free fatty acids (FFAs) determination The conversion rate of FFAs in the esterification with H2SO4-catalyst reaction was estimated by the titration method (Urrutia et al., 2016). 2 g of the SASO was added into a beaker and 10 ml of ethanol was introduced into the beaker. Three drops of chlorophyll indicator were added into the solution to start up the titration. Prepared solution of potassium hydroxide (KOH)-in-ethanol (EtOH) was added into the burette dropwise. The solution was continuously stirred during titration. The volume of KOH used was monitored when the colour of the solution changes from colourless to pink. The FFA content of the extracted oil was 2.46% and the acid value was 4.9 mg KOH/g before the esterification treatment. Further analysis on the sweet almond seed oil methyl ester (SASOME) was carried out using a two-step transesterification method. 2

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Fig. 1. Flow process used to utilize the production and properties performance of non-edible almond seed oil as a biodiesel for drilling fluid.

2.2.3. Esterification of sweet almond seed oil A two-step transesterification method was used to produce the biodiesel, according to a previous research (Sulaimon et al., 2017). These methods were used to avoid the problems of saponification associated with alkaline-catalyzed transesterification and slow reaction time, typically associated with the acid-catalyzed transesterification. Due to the high FFAs content which was 4.90% (> 1%w/w), we decided to adopt H2SO4-catalyzed esterification process to reduce the FFAs content to a level below 1%w/w. A high FFA content that is above 1%w/w will result in soap formation which may weaken the efficiency of the catalyst, cause gel formation, and leads to increase in viscosity. It could also make the separation of glycerol difficult. The parameters for the esterification process is shown in Table 1 and the reaction was conducted as follows: An aluminum tray containing water was heated at 60 °C using an electric heater. 200 ml sweet almond seed oil was added into 250 ml three-necked bottom flask mounted with a reflux condenser. The flask was placed in the tray on the electric heater with magnetic stirrer and temperature regulator. 2 g of sulphuric acid (H2SO4) was mixed with 43.96 g methanol and used as a catalyst in

the three-neck bottom flask. The mixture was transferred into a separating funnel and left to cool for 3 h after being heated for 60 min at 60 °C. The mixture was transferred and cooled for 3 h in a separating funnel. The methanol upper brown layer was removed, while the yellow oil with a SASOME lower layer was kept and washed with warm water of 1000 ml at 60 °C until it attained a pH 7. The water was then removed and the oil was cooled in the separating funnel at room temperature. Afterward, electric magnetic stirrer was used to stir the oil for 20 min at 100 °C. The remaining oil was SASOME which still contain FFA that was reduced through the second step transesterification method using KOH catalyst.

Table 1 Parameters for sweet almond seed oil esterification.

Table 2 Parameters for sweet almond seed oil transesterification.

2.2.4. Transesterification process The parameters for the transesterification process is shown in Table 2. 180 g of SASO was added in three-necked 250 ml bottom flask equipped with a reflux condenser. The flask was then placed in the tray and heated using electric heater with magnetic stirrer and temperature regulator. 1.80 g of KOH concentration was mixed with 39.57 g methanol and used as a catalyst in the three-neck bottom flask. The

Parameters

Units

Values

Computations

Parameters

Units

Values

Computations

Pressure Temperature Time Oil: Methanol (ratio)

psi °C hour –

14.7 60 1 1:6

Pressure Temperature Time Oil: Methanol (ratio)

psi °C hour –

14.7 60 1 1:6

H2SO4 catalyst

wt. %

1

– – – Mass of non-edible SASO = 200 g Molecular weight of SASO = 874.5 g/mol Mole of SASO = 0.2287 Density of methanol = 0.792 g/cm3 Molecular weight of methanol = 32.04 g/mol Mole of methanol = 6 × 0.2287 = 1.3722 Mass of methanol = 32.04 × 1.3722 = 43.96 g 200 g × 0.01 = 2.0 g

KOH catalyst

wt. %

1

– – – Mass of non-edible SASO = 180 g Molecular weight of SASO = 874.5 g/mol Mole of SASO = 0.2058 Density of methanol = 0.792 g/cm3 Molecular weight of methanol = 32.04 g/mol Mole of methanol = 6 × 0.2058 = 1.2350 Mass of methanol = 32.04 × 1.2350 = 39.57 g 180 g × 0.01 = 1.80 g

3

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3. Mud testing and properties evaluation

mixture was vigorously stirred for 1 h at 350 rpm (revolutions per minute) and at 60 °C. The mixture was transferred and cooled for 3 h in a separating funnel. After the reaction, the obtained products were centrifuged to separate the SASO methyl esters from glycerol. The glycerol at the lower layer was removed by gravity while the upper layer was a mixture of SASO methyl ester and methanol. Vacuum distillation of the mixture using rotating evaporator was used to remove the methanol, and the SASO methyl ester was analyzed after purification. The extracted biodiesel yield of 78.3% was separately collected, washed with warm water and stored prior to characterization and for drilling mud formulation. After the two-step transesterification methods, the FFAs content reduced to 0.39% and the acid value reduced to 0.78 mg KOH/g. In order to avoid error, 3 tests were carried out for the SASO sample and the average values of the 3 tests were recorded for further examination.

3.1. Microscopic and macroscopic tests The same formulation shown in Table 3 was used without thermal aging the two IEDMs in the microscopic properties investigation. The scanning electron cryo-microscopy (cryo-SEM) (Model C1002, USA) equipped with temperature regulator (Oxford Instruments, Model ITC502, England) was used. This test was used to examine the microstructure (formation and transformation) development of the BBDM and the diesel OBM. The cryo-specimen holder was loaded with the mud samples and cryo-fixed in a liquid nitrogen at −173 °C, and speedily transferred to the cryo-unit in the frozen state. This is done to preserve the original structure of the mud samples. The frozen mud samples were fractured and images were taken under an accelerating voltage of 100 KV cryo-SEM. With this method, the fractured surfaces of the muds were visualized directly while maintaining the temperature at −130 °C. The imaging was obtained with a sensitive crystal detector using the backscattered electron (BSE) collection signal. For the macroscopic properties characterization, the two muds were cryo-preserved in liquid nitrogen in order to retain their flow properties without thermal aging. A Discovery Series Hybrid Rheometer-2 (DHR-2 Rheometer, TA Instruments, Washington, USA) was used to measure their viscosities at 40 °C. The rheological behaviour were determined and compared in order to determine the macroscopic difference between the two drilling muds.

2.2.5. Biodiesel characterization Some of the produced biodiesel basic properties were tested following ASTM and European Committee for Standardization (ECN EN) specifications (ASTM D97, 2002; ECN EN14214, 2003; ASTM D6751, 2009; ASTM D6371, 2010). Fatty acid methyl ester content in the biodiesel was identified with Gas Chromatograph, an Agilent 6890N model (Santa Clara, CA, USA) mass spectrometry with a flame ionization detector (FID) was used and the following procedure was followed. About 0.05 g of the extracted oil was hydrolysed at 95 °C for 5 min with 3.5 ml of 0.4 M KOH in dry methanol. Titrimetric method was used to neutralize the mixture by using 0.6 M HCl. The neutralized mixture was again heated at 90 °C for 5 min to attain complete methylation process. Redistilled n-Hexane was used to extract the fatty acid methyl esters (FAMEs) thrice from the mixture. The n-hexane extracts were concentrated and 1 μl was introduced into the measuring port for gas chromatography analysis.

3.2. Rheological and filtration properties tests The rheological properties of the two IEDMs before and after thermal aging tests were evaluated with Fann model 50SL-HT Viscometer at four different temperatures of 50 °C, 80 °C, 120 °C and 150 °C under a broad-ranging shear rates from 5.11 to 1021 (1/s). With Viscometer dial reading data at different shear rates, the mud's apparent viscosity (AV), plastic viscosity (PV), and yield point (YP) was first tested at different temperatures before they were aged in a 4-roller oven for 16 h at 50 °C. They were tested again to determine the effect of increasing temperature on the formulated IEDMs after aging. The initial and 10-min gel-strengths (GS) were tested at a low shear rate of 5.11 (1/s) at different temperatures. The API Fann filter press was used to determine the API filtrate volume, while Fann HT4700 HPHT filter press was used for the HPHT filtrate volume.

2.3. Drilling mud formulation SASO was used as the continuous phase to formulate IEDM following past researches (Li et al., 2016a, b; Sulaimon et al., 2017). Table 3 presents the additives and their functions used to design the two IEDMs having the SASO biodiesel and diesel #2 as the continuous phase in ascending order. The muds were formulated to achieve a density of 12 ppg for one laboratory barrel (1 lab bbl), which is equal to 350 ml of non-aqueous based drilling muds following the API recommended practice for field testing oil-based drilling fluids (API 13B-2, 2014). Oilwater ratio (OWR) of 80:20 was used in the formulation. The SASO base oil was mixed with the mud additives using Hamilton beach multimixer. The same procedure was repeated for the diesel #2 base oil to design the diesel OBM.

3.3. Electrical stability tests The electrical stability (ES) of the BBDM and diesel OBM was conducted with Fann electrical stability meter without thermal aging tests following a previous study (Ali et al., 1987). The test was carried out at two test temperatures of 50 °C and 120 °C. Electrode probe was cleaned thoroughly, wiped dry and circulated in the mud sample. The test sample was prepared differently without clays and barite in order not to

Table 3 Invert emulsion drilling mud formulations for laboratory scale, equivalent to 1 bbl. Additive

Unit

Function

SASO mud

Diesel OBM

Diesel EZ-MUL Invermul Lime (alkaline) Geltone II Oil-soluble resin GLO OBM WETT 1000 Water Brine (CaCl2) Barite

ml g g g g g g ml g g

Continuous phase Oil wetting and emulsifying agent Primary emulsifier Neutralize fatty acids and alkalinity; stabilize emulsion. Viscosity modifier Filtrates loss control agent Wetting agent and dispersant Dispersed phase Forms base aqueous phase and provide shale stability Weight control agent

300 26.2 19.2 10.5 3.5 6.0 1.74 75 26.5 296.7

300 26.2 19.2 10.5 3.5 6.0 1.74 75 26.5 296.7

4

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Fig. 2. Experimental process for shale swelling test.

weaken the emulsion. The sample was placed in a glass beaker and adjusted to the test temperature. The sample was hand-stirred with the electrode probe for 10 s to make certain for uniform distribution and temperature of the sample. The electrode probe was allowed to be stable and undisturbed during the testing. It was placed not to have contact with the sides or bottom of the glass beaker and its surfaces were fully covered by the sample. Automatic voltage ramp started measuring the ES of the emulsion immediately the test button was pressed. ES reading was taken as the stop of the ramp showing a voltage breakdown. The test was repeated and average ES readings were computed.

experimental procedure of the shale swelling inhibition test. 3.5. Ecotoxicology and biodegradability tests Ecotoxicity test was conducted for the two IEDMs using the acute toxicity bioassay from four different marine species in 96 h, according to the specifications of organization for economic co-operation and development for respirometry test procedures (OECD, 301 D; 2001). The marine species are Poecilia latipinna, Tilapia guineensis, Moina mongolica and Artemia. The two IEDMs were added separately into the test chemicals prepared at a specification of 10,000 ppm concentration. The fishes were randomly distributed in batches of ten into the 10,000 ppm concentration. Mortality was recorded at the end of 96 h for the two IEDMs. The aerobic biodegradation tests of the SASO BBDM and diesel OBM were conducted using the mineral salts medium in a shake flask experiment following the respirometric test procedures (OECD, 301 D, 2001). The test was conducted with isolated microorganisms for 28 days with aniline (C6H5NH2) as the control sample. The compositions of the mineral salt medium used include: 320 ppm KCl (potassium chloride); 400 ppm MgSO4.7H2O (magnesium sulphate); 1400 ppm K2HPO2 (dipotassium phosphate); 700 ppm KH2PO4 (potassium dihydrogen phosphate); 14,000 ppm agar (C14H24O9) and 400 ppm NaNO3 (sodium nitrate). Two commonly used drilled cuttings isolated Staphylococcus sp. bacteria and Penicillium sp. fungi were used for the measurement. 140 ml concentration of the mineral salt medium was introduced into 250 ml of six different conical flasks and 15 ml each of SASO mud and diesel OBM were added. Each of the isolate was suspended in a 2 ml of mineral salt medium and incubated at ambient temperature for 28 days on a rotary shaker operated at 110 rpm. The percent biodegradability was calculated from the ratio of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) after 28 days, and plotted against time. The anaerobic biodegradability test of the mud samples was conducted for 60 days with palmitic (C16H32O2), as the control sample. The test procedures can be found in the international organization for standardization instruction manual (ISO

3.4. Shale swelling inhibition test The interaction between shale and drilling fluid was studied using a Fann Linear Swell Meter (LSM) model 2100, with four channels. Shale samples were collected from Dange formation (P), Agbada formation (Q), and Nkalagu formation (R) in Nigeria, and X-ray diffraction (XRD) test was used to select the shale sample containing the highest smectite/ montmorillonite content of the inhibition test. Fig. 2 shows the experimental process of the shale swelling inhibition test, which was based on previous studies (Ismail et al., 2015; Balaban et al., 2015; Barati et al., 2017). A total of six shale specimens with the same preparation was used for the shale swelling inhibition test for the SASO BBDM and diesel #2 OBM. Fann compactor for LSM, model 2100 was used to compact the shale plugs for 90 min at 10,000 psi. The two drilling muds were aged for 16 h in a 4-roller oven at 50 °C prior to the shale swelling tests. The swelling tests were performed on the six same prepared shale specimens half immersed in the SASO BBDM and the diesel OBM. The swelling test was conducted for continuous 36 h on each shale pellet and the measuring heads record the shale swelling inhibition individually. The average of the three shale swelling tests was taken for consistency and accuracy. The initial length of the six shale samples used was 16 mm and the average shale swelling data with standard deviation error bars were reported in percentage and millimetres of expansion based on the initial length. Fig. 3 shows the 5

Journal of Petroleum Science and Engineering 181 (2019) 106201

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Fig. 3. LSM (a) set up and (b) test of SASO BBDM and diesel OBM.

the biodiesel, and the plot of temperature versus viscosity profile of the biodiesel and the diesel #2 measured by a Fann model 50SL-HT Viscometer is shown in Fig. 4.

Table 4 Chemical compositions of commercial grade diesel #2 type. Carbon (%) Hydrogen (%) Sulphur (%) Calorific value (MJ/Kg) Boiling point Aromatics (%) Paraffins (%) Olefins (%) Chemical formula

86.77 12.86 0.035 42.83 282–338 °C 33.8 62.6 3.6 C10H22 to C15H32

4.4. Microscopic and macroscopic analysis The microscopic and macroscopic properties of the two IEDMs are presented in Fig. 5. Fig. 5a and b show the microscopic structures analyzed with cryo-SEM, while Fig. 5c and d show those of the macroscopic analysis of the BBDM and the diesel OBM, respectively. 4.5. Rheological properties of drilling muds

11734: R. 2017).

Table 7 shows the optimum range of rheological properties of drilling muds as recommended by the American Society of Mechanical Engineers (ASME, 2005). Fig. 6 shows the data on AV, PV, YP, YP/PV ratio and GS before and after thermal aging tests for 16 h at 50 °C for four different temperatures of 50 °C, 80 °C, 120 °C, and 150 °C. The effect of temperature on the shear stress versus shear rate profile of the two IEDMs before and after thermal aging tests (50 °C, 16 h) is shown in Fig. 7.

4. Results section 4.1. Chemical compositions of diesel #2 grade Table 4 shows the chemical compositions of conventional diesel #2 type used in this study, and it can be seen that the diesel #2 was composed of saturated hydrocarbons, aromatic and small proportions of olefins.

4.6. Filtration properties of mud samples

4.2. Chemical and fatty acid compositions of SASO biodiesel

Fig. 8 shows the data of (a) filtrate loss volume and (b) filter cake thickness of the two IEDMs before and after thermal aging tests (50 °C, 16 h) under different temperatures.

Table 5 shows the chemical and fatty acid compositions of the SASO biodiesel, and it is found that oleic acid, linoleic acid and palmitic acid are the major fatty acids in the biodiesel.

4.7. Electrical stability

4.3. Basic properties of SASO biodiesel and diesel #2

Fig. 9 shows the data of ES for SASO biodiesel and diesel #2 at temperatures of 50 °C and 120 °C conducted with Fann electrical

Table 6 shows some of the basic (fuel) properties of diesel #2 and Table 5 Composition of extracted sweet almond seed oil biodiesel. Type

Material

Unsaturated

Saturated Total Total Total Total a b c

saturated acids monounsaturated acids polyunsaturated acids unsaturated acids

SASO yield (%) (w/w) oil Acid value (mg KOH/g) Free fatty acid (FFA) % 1. Oleic acid 2. Linoleic acid 3. Linolenic acid 4. Palmitoleic acid 5. Palmitic acid 6. Stearic acid

Lipid number

C18:1 C18:2 C18:3 C16:1 C16:0 C18:0

Chemical formula

Molar weight (g/mol)

Density (g/cm3)

Content (wt. %)

– – – C18H34O2 C18H32O2 C18H30O2 C16H30O2 C16H32O2 C18H36O2 Cn:0 Cn:1 Cn:2, 3 –

– – – 282.47 280.45 278.43 254.41 270.45 284.45 – – – –

– – – 0.895 0.900 0.914 0.894 0.853 0.870 – – – –

78.3 ± 2.7a 4.9b; 0.78c 2.46b; 0.39c 70.7 17.1 0.7 0.4 9.3 1.8 11.1 71.1 17.8 88.9

Indicate average ± standard deviation of three tests. Indicates initial acid values before treatment. Indicates values obtained after pretreating the oil - indicate not specified. 6

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Table 6 Basic properties for commercial grade No. 2 diesel type (diesel #2) and SASO for this study. Properties

Sweet almond seed oil

Diesel #2

Test method

ECN EN14124

ASTM D6751

Colour Appearance form Molecular weight (g/mol) Kinematic viscosity (40 °C) (mm2/s) Density (g/cm3): 1. At 15 °C Flash point (°C) Cloud point (°C) Pour point (°C) Cold filter plugging point (°C) Cetane number Calorific value (MJ/Kg) Linolenic acid content (%mol/mol) Acid value (mg KOH/g) Iodine value (g. I2/100 g) Oxidative stability (hour/110 °C) Free glycerol (wt. %) Total glycerol (wt. %) Aromatic materials (wt. %) Water content (wt. %) Sulphur (wt. %) Sediment (wt. %)

Pale yellow Viscous liquid 874.5 4.31 0.874 169 −3 −9 −5 57 38.74 0.7 0.13 91.6 6.0 0.013 0.174 None None None None

Light brown Viscous liquid 190 3.52 0.848 78 −9 −18 −4 52 42.83 None 0.006 – 23 None None 33.8 None 0.035 None

– – – ASTM D97 ECN EN14214 ASTM D6751 ASTM D97 ASTM D97 ASTM D6371 ECN EN14214 ASTM D6751 ASTM D6751 ASTM D6751 ASTM D6751 ASTM D6751 ASTM D6751 ASTM D6751 ASTM D6751 ASTM D6751 ASTM D6751 ASTM D6751

– – – 3.5–5.0 – 120 min

– – – 1.96–6.0 – 130 min

– – 51 min – 12.0 max 0.5 max 0.12 max 6 min 0.02 max 0.25 – – – –

– – 47 min – a

0.5 max a

3 min 0.02 max 0.24 – – – –

5. Discussion section 5.1. Basic properties of SASO biodiesel and diesel #2 As Table 6 shows, the fuel properties of the two IEDMs are comparable. The density of the biodiesel is higher than that of diesel #2, which is due to the fatty acid content, free and bound glycerine content in the biodiesel (Acaroglu and Demirbas, 2007; Benjumea et al., 2008). The biodiesel has a significantly higher flash point than the diesel #2; demonstrating that the biodiesel can supply better fire safety, transportation and storage than the diesel #2 (Wang et al., 2012; Li et al., 2016a, b). The cetane number of the SASO biodiesel is 9.6% higher than that of diesel #2, indicating a lower ignition delay, and higher speed engines than those of diesel #2 (Kim et al., 2012; Ramadhas et al., 2004; Hasan and Rahman, 2017). Nevertheless, both values meet the specified minimum limits. The cloud point, pour point and cold filter plugging point of biodiesel are similar to those of the diesel #2. The high monounsaturated content of the biodiesel is the reason for its cold flow properties (Tang et al., 2008; Verma et al., 2016; Tchameni et al., 2018). The biodiesel meets the ASTM D6751 specifications and is considered to have good oxidation stability; in which it exhibits a halfyear shelf life, but is significantly lower than that of the diesel #2. The oxidative value of the biodiesel is due to the low content of methyl ester of linoleic acid (C18:2, 17.1%) in the biodiesel (Pantoja et al., 2013). The calorific value of the diesel #2 is 9.5% higher than that of the biodiesel, which is caused by the low proportion of carbon and hydrogen in biodiesel (Ramadhas et al., 2004). There is no threat of aromatic material and sulphur in the studied biodiesel, which indicates the biodiesel to be safer, less harmful and non-fluorescent than the diesel #2 (Li et al., 2015). In relation to the purity-related indicators, the biodiesel just like the diesel #2 is free of water and sediment. Furthermore, important acid values present in the biodiesel and absent in the diesel #2 are free glycerol, total glycerol and free fatty acids, and these values are important to low operating temperature and kinematic viscosity of biodiesel (Knothe and Steidley, 2005; Acaroglu and Demirbas, 2007; Moser, 2011). Herein, the SASO biodiesel shows acceptable values of free glycerol ≤0.02, total glycerol ≤0.24 and acid value ≤ 0.5 (ECN EN14214, 2003; ASTM D6751, 2009). The iodine value of the biodiesel meets the allowable maximum specification of 120 g. I2/100 g (ECN EN14214, 2003). Fig. 4 shows higher temperature-sensitivity of the biodiesel viscosity than that of diesel #2. The kinematic viscosity of the extracted biodiesel is higher

Fig. 4. Temperature versus viscosity profile of extracted SASO and diesel #2 at shear-rate of 1021 (1/s).

stability meter without thermal aging tests. 4.8. Shale swelling inhibition performance Fig. 10 shows the results of three clay minerals (P, Q, R) tested with XRD to select the highest amount of smectite/montmorillonite, while the shale swelling inhibition performance data for the two IEDMs are presented in Fig. 11. 4.9. Ecotoxicity and biodegradable analysis The data of ecotoxicity tests for the SASO biodiesel and diesel #2 are listed in Table 8 according to the recommended specifications (OECD 301 D, 2001). Fig. 12 shows the results of (a) aerobic and (b) anaerobic biodegradability of SASO BBDM and diesel OBM measured following the recommended specifications (OECD 301 D, 2001; ISO 11734: R, 2017).

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Fig. 5. Freeze-fracture cryo-SEM micrograph of (a) diesel OBM, (b) SASO BBDM and macroscopic analysis of diesel OBM and SASO BBDM on (c) viscosity versus shear rate, and (d) shear stress versus shear rate measured at 40 °C with combination of optical microscopy and DHR-2 rheometer.

resistance to the emulsion breakage due to the presence of emulsifiers in both drilling muds. The water-in-oil emulsion appeared as a dark spherical shape and the surrounding phase of the drilling muds appeared as a bright phase and they have comparable uniform size distributions (Li et al., 2018). The diesel OBM appeared to have smaller droplet sizes, while more emulsion droplets are formed in the BBDM, which is ascribed to the formed reticular aggregates between the emulsion droplets and the organophilic clays through hydrogen bonding (Li et al., 2016a, b). As Fig. 5c shows, the viscosity of the biodiesel was lower than that of the diesel #2, and it increased when the shear rate approaches zero, which indicates their suspension's ability when fluid circulation is halted (Oseh et al., 2019b). As can be seen from Fig. 5d, the rheograms of the two IEDMs conforms to the Power law equation, expressed as τ = k(γ)n (Muherei and Basaleh, 2016). This is because, the change in shear stress with shear rate of the IEDMs passes through the origin with a Power law shape. These data are consistent with the recent investigations (Boyou et al., 2019; Oseh et al., 2019b). The rheograms of both drilling muds is related to the microstructural reorganization of the fluid molecules (Li et al., 2018).

Table 7 API specifications of drilling mud properties for 150 °C (ASME, 2005). Properties

Unit

Specified limits

Plastic viscosity (PV) Apparent viscosity (AV) Yield point (YP) YP/PV Initial gel-strength (GS) 10-min gel strength (GS) Filtrates loss (FL) Filter cake thickness (FCT) Electrical stability (ES)

cP cP lb/100 ft2 – lb/100 ft2 lb/100 ft2 ml mm volts

< 35 – 15–25 – 6–10 8–12 <4 <2 > 400

ASME: American Society of Mechanical Engineers.

than that of diesel #2, which is due to the large proportion of monounsaturated (71.1%) and total unsaturated (88.9%) fatty acids in the biodiesel (Verma et al., 2016; Li et al., 2016a, b; Li et al., 2018). The desired performance on the rheology of the biodiesel, especially in a cold region can be achieved by appropriate design of the drilling mud formulation. Briefly, characterization data shows the biodiesel met the standard requirements of a base oil for BBDM, mostly for its high flash point, non-toxic, and non-fluorescence.

5.3. Rheological properties of drilling muds The rheological data show that not much significant difference of PV, YP, YP/PV ratio, initial and 10-min gel strengths occurred between the SASO BBDM and the diesel OBM before and after thermal aging tests (Fig. 6a – d). Before thermal aging, the AVs and the PVs of the BBDM are minimally lower than those of the diesel OBM, which is attributed to the fatty acid chain length and the existence of carbon

5.2. Microscopic and macroscopic analysis The results of the microscopic tests shown in Fig. 5 reveal high magnification images, high stability of water-in-oil emulsion and high 8

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Fig. 6. Temperature increment on rheological properties of SASO BBDM and diesel OBM before and after thermal aging tests (50 °C, 16 h).

double bonds (C18:1; C18:2 and C18:3) in the BBDM (Knothe and Steidley, 2005). Temperature effect is a crucial indicator to determine the stability of the properties of drilling fluid. The PVs and AVs of both IEDMs decreased with temperature increment before and after oven treatment. This is attributed to the liquid molecules, which are more energized with increasing temperature. The cohesive intermolecular forces in the liquid molecules can be strongly be opposed by the energized liquid molecules; thereby enabling them to move more freely (Demirbas, 2008). The data in Fig. 6 shows the temperature sensitivity of the BBDM viscosity is lower than that of the diesel OBM before and after oven treatment. This is caused by the difference of the affinities of these two oils to the organophilic clay (Geltone 11) (Li et al., 2015; Sulaimon et al., 2017). These data exemplified that SASO has the lower viscosity than diesel #2, which infers less resistance to flow and pressure losses (Caenn et al., 2017). As Fig. 6a–d show, the YPs of the two IEDMs are comparable and they followed a similar trend of the PV and AV before and after heat treatment. However, a slightly better YP/PV ratio of the biodiesel than those of the diesel #2 can be observed before and after the oven treatment. The YPs of both muds met the specifications of API RP 13B-2 (2014) and ASME, 2005 (Table 7). In addition, these YPs are not so large as to induce excessive pump pressure when starting mud flow (Oseh et al., 2019a, b). The content of colloidal sizes of organophilic clays interacting with the biodiesel molecules is the reason for the improved YP of the BBDM (Sulaimon et al., 2017). Similar research carried out showed that YP reduced after hot rolling with increasing

temperature (Li et al., 2015). Fig. 6a–d also depict that temperature variation before and after oven treatment does not much affect the initial and 10-min gel strengths of the mud samples. Both IEDMs have good and similar gel strengths before and after thermal aging tests, and are within the recommended operating range (Table 7). With a good gel strength, drilled cuttings are effectively suspended in the hole when fluid circulation is paused (Sulaimon et al., 2017; Boyou et al., 2019). As Fig. 6a–d show, the rheological data of the studied BBDM are within the acceptable limit (API RP 13B-2, 2014; ASME, 2005), and are consistent with previous investigations (Li et al., 2015; Sulaimon et al., 2017). To more understand the rheological behaviour, the shear stress versus shear rate profile of the BBDM and the diesel #2 OBM under different temperatures were investigated (Fig. 7a–d). The curves or trend lines were fitted with a two-parameter rheological (Bingham plastic) model, which is widely used in the rheological properties of drilling fluids to describe the flow behaviour of many types of drilling muds owing to its high accuracy and explicit interpretation of pseudoplastic fluid behaviour (Elochukwu et al., 2017; Oseh et al., 2019b). Fig. 7a–d show the shear stress versus shear rate plot for the BBDM and the diesel OBM to be of nearly similar trend both before and after heat treatment. The diesel OBM trend lines are slightly higher than those of the biodiesel. The trend lines show the drilling muds to behave as a Bingham plastic fluid. This is because the trend lines matched the Bingham plastic model (Oseh et al., 2019b). The trend lines show that the behaviour of all the drilling muds were characteristics of shearthinning because of their increasing shear stress at increasing shear9

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Fig. 7. Shear stress versus shear rate rheograms of SASO BBDM and diesel OBM before and after thermal aging tests (50 °C, 16 h).

Fig. 8. Filtration properties of SASO BBDM and diesel OBM before and after thermal aging tests for 16 h at 50 °C under different temperature (a: filtrate loss volume; b: filter cake thickness). 10

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rate, which further exemplifies viscosity increment from 5.11 to 1022 (1/s) shear rate (Boyou et al., 2019; Oseh et al., 2019b). These rheograms of the BBDM are dependent on the high content of the biodiesel unsaturated fatty acids (88.9%) and the carbon double bonds (Oleic, C18:1; linoleic, C18:2 and linolenic C18:3) of the unsaturated fatty acids. These data are in accordance with a previous study (Li et al., 2015). 5.4. Filtration properties analysis As shown in Fig. 8, the filtration properties of the two IEDMs are comparable, and they increased, with increasing temperature both before and after oven treatment for 16 h at 50 °C. As Fig. 8a shows, the filtrate volume at the temperatures of 50 °C and 80 °C before and after thermal aging are within the API recommended limit, and are slightly above the limit at 120 °C and 150 °C (Table 7). At all temperatures, there is no much significant difference in the filter cake thickness of both drilling muds according to Fig. 8b. From the shown data, the BBDM has satisfactory filtration properties (filtrate volume < 5.0 ml) and (filter cake thickness < 4.0 ml) before and after hot rolling. The two IEDMs have a tight packing structure that effectively sealed the openings between the micron-sized particles that would otherwise allow fluid flow (Zhong et al., 2019; Oseh et al., 2019b). Based on the reference point accepted by the current drilling industry, an API filtrate loss volume less than 10 ml in 30 min is considered to have qualified for drilling operations (Yang et al., 2013). This implies that SASO has the potentials of becoming a good filtration control agent for IEDM. Furthermore, in some instances, this set-limits are raised to 15 ml (Yang et al., 2013).

Fig. 9. Electrical stability study for BBDM and diesel OBM conducted with Fann electrical stability meter without thermal aging tests.

5.5. 4. Electrical stability As Fig. 9 shows, the ES of both drilling muds significantly increased above the specified limit of 400 V at both temperature conditions. However, the ES of the diesel #2 is lower than that of the biodiesel at the two measured temperatures. It can also be seen that at higher temperature (120 °C), the ES of both drilling muds reduced, but the values were still within accepted limits. This exemplifies that the BBDM can meet the operating requirements for drilling operation at 120 °C. This finding is consistent with previous studies (Ali et al., 1987; Li et al., 2015; Sulaimon et al., 2017). The reason for the higher ES of the biodiesel being the effectiveness of the emulsifier associated with the organophilic clay in the BBDM to increase its oil wetting (Growcock et al., 1994; Ghosn, 2016).

Fig. 10. XRD tests data of SASO BBDM and diesel OBM.

5.6. Shale swelling inhibition performance Clay mineral Q was used to build the shale pellets used in the shale swelling inhibition tests because it contains the most amount of smectite/montmorillonite (Fig. 10). Fig. 11 shows the average values of shale swelling inhibition data of the two IEDMs with a standard deviation error bars to be almost the same. The shale swelling data are quite low (0.02 mm swelling of initial length 16 mm for BBDM) and (0.018 mm swelling of initial length 16 mm for diesel OBM) under the considered experimental conditions, but there is a slight little difference between them. The BBDM showed less shale swelling and lower swelling rate than the petrol-diesel in the first 18 h. The BBDM-immersed pellet started to swell slightly more, reaching swelling saturation point at 10% in 24 h, compared to the diesel-immersed pellet's 9.0% and the swelling trend continued. Shale swelling data up till 36 h showed diesel #2 with slightly better inhibition, which is due to the difference in molecular structure of the two studied oils (Ismail et al., 2014; Ismail et al., 2015; Li et al., 2015). These data are consistent with a previous study, in which it was reported that biodiesel molecules have larger polarities than those of petrol-diesel molecules, for the presence of carbonyl groups in biodiesel. This causes the biodiesel to have a strong

Fig. 11. Average linear shale swelling rate-time curves with standard deviation error bars for SASO BBDM and diesel #2 OBM. 11

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Table 8 Ecotoxicities of biodiesel and diesel fuel (test procedure: OECD 301 D, 2001). Test samples

Test species

Test procedures

Test specifications

Results

Diesel

Poecilia latipinna Tilapia Guineensis Moina mongolica Artemia Poecilia latipinna Tilapia Guineensis Moina mongolica Artemia

72 h 96 h 96 h 96 h 96 h 96 h 96 h 72 h

10, 10, 10, 10, 10, 10, 10, 10,

384.6 ppm 251.7 ppm 498.3 ppm 279.2 ppm 28, 287.4 ppm 37.841.5 ppm 42, 234.8 ppm 37, 083.6 ppm

SASO

EC50 LC50 LC50 LC50 LC50 LC50 LC50 EC50

000 ppm 000 ppm 000 ppm 000 ppm 000 ppm 000 ppm 000 ppm 000 ppm

OECD is Organization of economic co-operation and development; EC50 is effective concentration 50%, LC50 is lethal concentration 50% and ppm is parts per million.

interaction with the shale sample and reduced its swelling rate (Li et al., 2015).

where it was reported that biodiesel molecules have low branching degrees in their structure and are free of aromatic, as can be confirmed in the test data shown in Table 6. This helps the studied biodiesel to biodegrade faster and to have higher biodegradation than the diesel #2 (Li et al., 2015; Li et al., 2016a, b).

5.7. Ecotoxicity and biodegradable analysis As Table 8 shows, the biodiesel has significantly higher lethal concentration 50% (LC50) and effective concentration 50% (EC50) than those of the diesel #2. The biodiesel is safer and less harmful compared to diesel #2, because it is free of sulphur and aromatic (Li et al., 2016a, b). The biodiesel meets the toxicity specifications limit for a non-aqueous based muds, while the diesel #2 is above the limit (OECD 301 D, 2001). As reported in a previous study, which is in agreement with this study, the ranking of toxicity for the diesel #2 is moderately toxic (Li et al., 2015, 2016a). The biodiesel showed higher biodegradation than the diesel #2. As Fig. 12a shows for the aerobic biodegradation, the BBDM exhibited 78% biodegradation and 83% biodegradation with Staphylococcus sp. and Penicillium sp., respectively, during the 28-day period of testing, in comparison to those of diesel OBM of 23.7% with Staphylococcus sp. and 25.2% with Penicillium sp. The results of anaerobic biodegradation of the BBDM and the diesel OBM presented in Fig. 12b showed that a total of 60% and 62% of the BBDM with Staphylococcus sp. and Penicillium sp., was biodegraded, respectively, while those of diesel OBM displayed 29% and 31% biodegradation, respectively, after 60 days. These data are consistent with previous research,

6. Economic evaluation of SASO BBDM Table 9 shows the cost of products used to extract the SASO, while the formulations and the waste management costs of the two IEDMs are presented in Table 10. The almond seeds used were procured in the Sabon Gari market, Kano in Northern Nigeria on 4th September 2018 at a cost of (10.87 US$/kg). The cost of these seeds and each of the chemicals used to extract the SASO were scaled to the actual concentration used to formulate one laboratory barrel of the SASO BBDM (Table 9). As the table shows, the cost of extraction of the SASO (82.75 US$/bbl) was lower compared to the cost used to procure the diesel #2 grade, which was 3.03 US$/gallon (127.3 US$//bbl) as at the time of conducting this study (U.S Energy Information Administration, April 2019). According to the data shown in Table 10, cost comparison shows lower BBDM formulation and waste management costs than diesel #2 OBM with about 47.6 US$/bbl, which is mainly due to the affordable cost of the almond seeds and lower waste management cost (Puder and Veil, 2006; Fazal et al., 2011; Ihenacho et al., 2017; Ismail et al., 2017).

Fig. 12. Biodegradation of SASO BBDM and diesel #2 OBM (a: aerobic biodegradability for 28 days, according to OECD 301 D, 2001), and (b: anaerobic biodegradability for 60 days, according to ISO 11734: R2017). (BOD is the biochemical oxygen demand (mg/L) and COD is the chemical oxygen demand (mg/L)).

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Table 9 Total extraction costs of sweet almond seed oil for laboratory scale, equivalent to 1 bbl of 80:20 OWR for this study. No.

Products

Unit size bought

Quantity

Cost/unit size (US $)

Total cost (US$)

Actual concentration of products used

Actual cost of products used (US $/bbl)

1 2 3 4 5 6 7 8

Almond seeds Methanol Sodium hydroxide Potassium hydroxide Sulphuric acid n-Hexane Hydrochloric acid Ethanol

1 kg 250 ml 100 ml 250 g 100 g 100 ml 100 ml 1L

2 1 1 1 1 1 1 1

10.87 14.33 42.83 54.6 22.30 72.56 30.77 0.0078

21.74 14.33 42.83 54.6 22.30 72.56 30.77 0.0078

1200 g 120 ml 50 ml 70 g 40 g 20 ml 20 ml 250 ml

13.04 6.88 21.42 15.29 8.92 14.51 6.15 0.00195

Total cost of products used to extract almond seed oil of 1 laboratory bbl, equivalent to 350 ml of drilling fluid (US$).

Table 10 Economic evaluation of laboratory scale, equivalent to 1 bbl of 80:20 OWR for diesel #2 OBM and SASO BBDM for this study. Retail prices

Diesel #2 OBM

SASO BBDM

Total cost of SASO extraction (US$/bbl) Cost of base oils (US$/bbl) Required amount of base oils (bbl) Cost of base oil per required amount (US$/bbl) Total cost of formulating 1 bbl excluding other mud additives (US$/bbl) Transportation of drilling effluents to disposal site (US$/bbl) (Ihenacho et al., 2017) Commercial disposal of drilling effluents (US$/bbl) (Ihenacho et al., 2017) Transportation + commercial disposal cost of drilling effluents (US$/bbl) Total cost of wastes management of 1 bbl of drilling muds (US$/bbl) Total cost of formulation + total cost of wastes management (US$/bbl) Overall cost of 1 bbl of developed IEDMs (US$/bbl)

127.30 0.80 101.84 101.84 3.0 57.0 60.0 60.0 161.84 161.84

82.75 – 82.75 3.0 28.5 31.5 31.5 114.25 114.25

7. Conclusions

Acknowledgements

In the present research, the following conclusions were obtained:

The authours wish to thank the Department of Chemical and Petroleum Engineering, Afe Babalola University, Ado-Ekiti, Nigeria for providing the facilities used in this study and the Research Management Centre of UTM by providing the research grant (vote no. Q. J130000.2546.17H77) and the Malaysian Ministry of Higher Learning for their support.

1. The cold flow properties, rheological behaviour, filtration properties and shale swelling inhibition performance of the newly-designed SASO BBDM are comparable to those of diesel #2 OBM. 2. Microscopic and macroscopic investigations of the BBDM show the formation of reticular aggregates of emulsion droplets, organophilic clays, and other solid particles. The drilling mud system behaves like a Power law fluid and displays a good correspondence between its microscopic and macroscopic structures. 3. The good shale swelling inhibition, good rheological and filtration control, compatibility with OBM additives, high flash point, good electrical stability, high thermal stability, environmental friendliness, superb biodegradability, low cost, and availability can make the application of SASO as a potential candidate for BBDMs.

Nomenclature API American petroleum institute ASME American society of mechanical engineers ASTM American society for testing materials AV Apparent viscosity BBDM Biodiesel-based drilling mud BOD Biochemical oxygen demand CFPP Cold filter plugging point COD Chemical oxygen demand CP Cloud point Cryo-SEM Scanning electron cryomicroscopy EBM Ester-based mud EC50 Effective concentration 50% ECN EN European committee for standardization ES Electrical stability FAMEs Fatty acid methyl esters FFAs Free fatty acids FID Flame ionization detector GS Gel-strength HPHT High pressure high temperature IEDM Invert emulsion drilling mud ISO International organization for standardization LC50 Lethal concentration 50% LSM Linear swell meter

8. Suggestions for future work 1. The findings in this study are only limited to the standard temperature conditions below the freezing level from 50 °C to 150 °C. Outdoor low temperature conditions of drilling fluid properties are an important factor to be considered, especially on the stability of rheology in a cold flow drilling environments where the temperature could be as low as −40 °C. Future studies should investigate on how to ensure stable rheological properties of drilling fluids in a cold flow environments using various blends of SASO-petrol diesel, along with other parameters. 2. The efficiency of various blends of SASO-petrol diesel drilling fluids under dynamic flow conditions using cuttings transport flow loop should be considered. The dynamic tests in a flow loop can help to provide interpretation of the actual dynamic performance of the fluids in the field. 13

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OBM OECD OWR PME PP PV SASO SASOME WBM XRD YP

Oil-based mud Organization of economic co-operation and development Oil-water ratio Palm methyl ester Pour point Plastic viscosity Sweet almond seed oil Sweet almond seed oil methyl ester Water-based mud X-ray diffractometer Yield point

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