The use of palm oil fatty acid methyl ester as a base fluid for a flat rheology high-performance drilling fluid

Accepted Manuscript The use of palm oil fatty acid methyl ester as a base fluid for a flat rheology highperformance drilling fluid Mohammed Mokhtar Said, Abdel-Alim Hashim El-Sayed PII:

S0920-4105(18)30293-6

DOI:

10.1016/j.petrol.2018.03.101

Reference:

PETROL 4842

To appear in:

Journal of Petroleum Science and Engineering

Received Date: 4 August 2017 Revised Date:

26 March 2018

Accepted Date: 28 March 2018

Please cite this article as: Said, M.M., El-Sayed, A.-A.H., The use of palm oil fatty acid methyl ester as a base fluid for a flat rheology high-performance drilling fluid, Journal of Petroleum Science and Engineering (2018), doi: 10.1016/j.petrol.2018.03.101. 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.

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Title:

The use of palm oil fatty acid methyl ester as a base fluid for a flat rheology high-performance drilling fluid

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Authors: Mohammed Mokhtar Said

PhD Student, Memorial University of Newfoundland (2016-Present) Masters Student, Cairo University (2011-2014) Drilling Fluids Engineer, MI-SWACO a Schlumberger Company (2006-2015)

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Dr. Abdel-Alim Hashim El-Sayed

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Emeritus Professor of Petroleum Engineering, Cairo University

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The use of palm oil fatty acid methyl ester as a base fluid for a flat rheology high-performance drilling fluid

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Abstract Exploration for oil and gas in increasingly difficult environments is constantly fueled by rising world energy demand. Exploration is now extending into environmentally-sensitive regions, particularly in offshore fields. Oil and synthetic-based muds have always performed better with hostile drilling cases. However, they are also a cause for environmental concern and potential long-term liabilities for damage caused by mud spills, and are associated with problems in disposing of oil-contaminated drill cuttings. In response to these concerns, the oil industry has been replacing high-aromatic oils (e.g., diesel) with low-aromatic mineral oils as well as synthetic oils. One of the possibilities in avoiding these problems, while keeping the advantages of oil-based muds, is to substitute mineral oils with biodegradable vegetable oils. In this paper, it is shown that palm oil fatty acid methyl ester is successfully used as a base fluid for a highperformance, oil-based flat rheology drilling fluid. The performance of this newly formulated vegetable oil-based drilling fluid is compared to that of commercially available oil-based drilling fluids to evaluate the potential of their use. Fluid samples were formulated up to 18 ppg density and passed contamination tests. The formulated fluid was also statically aged and hot rolled for performance tests. The resulting drilling fluid is an environmentally-friendly fluid suitable for environmentally sensitive areas. The fluid testing results are then used to perform hydraulic simulations to estimate the fluid performance in the field. Nomenclature API : American Petroleum Institute : Equivalent circulating density : Low toxic base fluid

Fatty acid methyl ester Hydrochloric acid High temperature high pressure Potassium hydroxide Lethal concentration 50 Lost circulation material Normality (unit of measuring concentration) Sodium hydroxide Oil-based mud Palm oil fatty acid methyl ester Pounds per gallon Permeability plugging tester Rotation per minute Viscometer sag shoe test

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: : : : : : : : : : : : : :

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ECD Escaid 110 FAME HCl HTHP KOH LC50 LCM N NaOH OBM PFAME PPG PPT RPM VSST

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CH3ONa : Sodium methoxide

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1. Introduction

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Since their development in the early 20th century, oil-based muds (OBM) have dominated over other kinds of mud. They provide excellent borehole stability, perform superbly in high temperature and sour environments, provide high lubricity, and they generate negligible aqueous filtrate invasion; thus, they mitigate formation damage [1].

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The performance of oil-based muds however, is negatively impacted in deep-water drilling projects. The cold temperatures encountered at the sea bed result in a three to fourfold increase in the viscosity of conventional invert emulsion fluids. Viscous mud generates high break circulation pressures, as well as elevated equivalent circulation densities (ECD’s) during circulation and drilling. Elevated viscosities of return mud usually require the use of coarser shaker screens to avoid mud losses over the shakers. This practice results in a build-up of the drilled solids in the mud, and thus, necessitates higher dilution rates and consequently, results in higher mud costs [1-7].

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To address the elevated ECD’s issue in conventional fluids, operators have had to reduce rheology at lower temperatures to keep the viscosity low in the seabed region of the well. This often results in poor hole cleaning, sag, and/or other drilling problems related to low rheology at bottom-hole static and circulating temperatures. On the other hand, adjusting the rheology upwards to prevent these problems, leads to excessive ECD values and gel strengths. This limits the rates of penetration, increases downtime, and leads to loss of circulation [1].

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Flat rheology drilling fluids, which are invert-emulsion fluids that were developed to address the elevated ECD’s in cold temperature conditions, were introduced as fluids which have the 6RPM reading as close as possible to either the 100-RPM reading or the fluid yield point as measured using an industry-standard viscometer at a single temperature of 50°C (122°F). This "flatness” of rheology is supposed to improve the cuttings-bed pickup and reduce sag in highangle holes. A more recent definition of flat rheology describes a fluid that has comparatively unchanging gel strength, yield point, and a 6-RPM reading at 4°C (39°F), 50°C (122°F), and 75°C (167°F) as measured with a standard viscometer [2]. The aquatic toxicity of diesel oil, and even that of low toxic mineral oils that are used for modern day high-performance fluids, makes them unsuitable for use in many environmentallysensitive offshore areas. In the year 2000, the US Environmental Protection Agency added synthetic based fluids to its effluent limitation guidelines. These guidelines allow for the controlled discharge of cuttings, which meet a certain specification (as determined by a static sheen test) [7]. The North Sea, on the other hand, has more restrictive regulations, insisting on zero discharge of synthetic based cuttings. Therefore, all cuttings must be hauled to shore for treatment and disposal. Since the average well generates 1000 to 1500 tons of cuttings with average oil retention of about 15%, this will generate 150 to 225 tons of base oil. As a result, these cuttings need special treatment, which increases operational costs, before being safely discharged in the environment [8] 2

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Researchers have explored the use of vegetable oils and their derivatives as an alternative to diesel oil since the early nineties. Palm oil, rapeseed oil, soybean oil, jatropha oil, castor oil, rubber seed oil, ground nut oil, and canola oil are the top contenders for replacing diesel oil. All the vegetable oils exhibit remarkably low toxicity, but their performance falls short when rheological parameters are compared to those of mineral oils due to the oils’ inherently high viscosities.

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The earliest studies started experimenting with palm oil as a base fluid. The oil was promising as it was non-toxic. It also exhibited desirable qualities such as: a high flash point, low price, high availability and good emulsion stability. However, it had many undesirable properties such as: high PV, low aniline point, and high fluid loss. Further studies demonstrated the oil’s low toxicity compared to diesel with 82% survival rate of the organisms exposed to the formulated drilling mud. It also has favorable rheological properties comparable to some commercial drilling fluids. Later studies compared palm oil to other oils. One such study compared palm oil to groundnut oil. The study focused on rheology and toxicity. Mud was successfully formulated at 90/10 oil water ratio, but it exhibited high viscosity and progressive gel characteristics. The formulated mud congealed during formulation when higher ratios were used. Plants exposed to the formulated from these two oils exhibited a 20% and 12% average rate of growth without losing all its greenness. The study encouraged the use of Palm oil due to its high biodegradability, friendlier eco-toxicological properties and a lower cost of treatment of cuttings compared to Oil-based drilling mud formulated with diesel. Mineral and conventional synthetic oil. [8-12]

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A study focusing on filtration control conducted a comparison to demonstrate the effect of industrial starch on the filtration properties of melon, groundnut, soybean, and palm oils. All the oils had their filtration properties tend towards that of diesel oil at ambient temperature and atmospheric pressure. The study concluded that polymer and thinners significantly improved the filtration properties of the formulated mud. The ranking from the results showing the order of better and effective filtration properties for the oils are Melon Oil; Groundnut Oil; Soybean Oil and Palm oil. [13]

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Another worthy alternative considered by recent studies was jatropha oil. A study in 2013 showed that Jatropha Oil based mud were more adaptable, had higher carrying capacity and less in pipe pressure loss than diesel oil based mud. The study was motivated by several comparisons with other vegetable and mineral oils. The comparisons started with A study comparing the performance of Jatropha to that of rapeseed oil. Jatropha oil was found to be of lower viscosity thereby implying less resistance to flow and pressure. Later, Jatropha, Moringa and Canola oils were used to formulate three different muds. The mud’s toxicity, rheology and filtration properties were tested, and the results of the tests carried out indicate that Jatropha, Moringa and Canola OBM'S have great chances of being among the technically viable replacements for mineral OBM's, if additive chemistry is employed in the mud formulation, to overcome the inherently high viscosity of the oil. Further studies developed a model for predicting the downhole mud density of diesel, jatropha and canola based fluids. The density 3

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variation with temperature difference became constant at some point. The diesel OBM showed the highest variation range, while the canola OBM showed the lowest. [14-16]

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A later study comparing jatropha and ground nut oils to diesel found that the viscosity values of the mud samples from the three oils varied considerably at the same viscometer speed, 600 RPM, at 60°C (140°F). the viscosities were 155, 135 and 50 (cP) for jatropha, groundnut and diesel oils based mud samples respectively. The jatropha and groundnut oil based mud samples were respectively 3 and 2.7 times more viscous than diesel oil based mud. Other studies were conducted using castor oil, rapeseed oil, rubber seed oil, and soybean oil as their primary point of focus. [17]

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These works showed that using vegetable oils we can formulate an environmentally friendly unweighted drilling fluid. Filtration control of the formulated muds can be comparable to that of industry standard diesel based muds, but rheology and density are far from the desired industry performance, due to the high viscosity of vegetable oils compared to mineral oils. Most works suggest the use of special additives to overcome the higher viscosity, while others suggest the use of esters derived from the vegetable oil. [18-21]

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Esters derived from vegetable oils retain all the oils’ favorable properties without the excess viscosities that lead to unfavorable rheological properties in the formulated mud. They possess unique ecotoxicological properties, which dramatically reduce the impact of drilling fluids on the marine environment. Ester-based fluids meet the highest US Environmental Protection Agency standards. They satisfy the EPA’s 275-day biodegradation test and the Leptocheirus LC50 toxicity test. Their environmentally-benign properties have been confirmed by seafloor surveys in the North Sea, Gulf of Mexico, offshore Australia, and Brunei, as well as from ongoing toxicity testing with various marine species [6],[24],[22-31].

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Vegetable esters have surpassed expectations since their introduction in 1990 in the Norwegian waters, though the chemical and drilling industries have produced alternatives to esters (primarily based on synthetic petrochemicals). Esters have consistently outperformed these alternatives, particularly at high anaerobic biodegradability tests. Esters also have the lowest toxicity to marine species. Vegetable esters pose a much smaller risk to human health (no inhalation toxicity), do not taint marine life or accumulate in the marine environment, and do not have any negative effects on algal photosynthesis. In addition, they reduce the danger of fires as they have a higher flash point and a lower vapor pressure than mineral oils. They have also been proven in the field in more than 400 wells [25-26]. Palm oil in particular is abundant in Malaysia, and several other tropical countries. It is used after processing to produce Biodiesel through transesterification with alcohols. Several blends of different esters and mineral oils were tested as base fluids for invert emulsion fluids with varying degrees of success. Palm oil methyl ester remains the best candidate for the application, due to its lower viscosity as it has the shortest molecular chain, even though it was observed to have alkaline hydrolysis at high temperatures [6].

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This paper demonstrates a process for extracting palm oil fatty acid methyl ester from refined bleached deodorized palm oil through a transesterification reaction. The extracted ester is used to formulate a high-performance oil-based flat rheology drilling fluid. The performance of the newly formulated vegetable oil-based drilling fluid is compared to a commercially available low toxic mineral oil-based drilling fluid to evaluate the potential of its use. 2. Experimental Procedures 2.1. Fatty acid methyl ester extraction

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2.1.1. Materials

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According to recent research, a high-purity fatty acid methyl ester (FAME) can be obtained from vegetable oils through a single-phase transesterification reaction. The addition of a simple ether, to act as a co-solvent to achieve miscibility between the oil and the alcohol, allows for the reaction to take place much faster, without heating or agitation, which eliminates the need for using a reactor. The transesterification of triglycerides produces fatty acid alkyl esters and glycerol. Due to its higher density, the glycerol layer settles at the bottom of the reaction vessel. The reaction is reversible; thus, an excess of alcohol is required to shift the reaction towards ester formation. The process is quite simple and has been adapted for mass production of alkyl esters by the bio fuel industry. Using high shear mixers and pumps instead of the reactors used for conventional transesterification. Transesterification is faster when catalyzed by an alkali, and the most commonly-used alkali catalysts are sodium hydroxide (NaOH), sodium methoxide (CH3ONa), and potassium hydroxide (KOH) [32].

The oils and materials used were as follows: High purity bleached palm oil (obtained from local markets), as well as hydrochloric acid (HCl) 2N, sodium hydroxide, anhydrous methanol and diethyl-ether which were obtained from Morgan Chemical Company.

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2.1.2. Ester extraction procedure

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The ester extraction process was carried out using equipment readily available in a standard mud-testing facility. The ambient temperature was 18°C (64°F). 1082 cc of oil was mixed with 310 cc of di-ethyl-ether in a 2000 cc beaker on a magnetic stirrer below a fume extractor. 10 gm of NaOH were dissolved in 355 cc of methanol and were then added to the oil-ether mixture and stirred at 1000 RPM for 60 minutes at room temperature. The mixture was moved to a fume hood, and was left in a static condition for the glycerol to settle at the bottom of the beaker through gravity. After the separation was complete, the upper ester layer was moved to another beaker and 125 cc of 2N (2 Normal) HCl was then added to the beaker to quench the alkaline catalyst. The ester was then heated to 110°C (230°F) to remove the ether, excess methanol, and any traces of water from the catalyst neutralization reaction. The resulting fluid was then filtered using an API filter press to remove any impurities from the final product. 5

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2.2. FAME quality control.

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According to biodiesel standards (ASTM D 6751 and EN 14214) the most important aspects of the product are having a complete transesterification reaction, the removal of the free glycerol, residual catalyst and alcohol, and the absence of free fatty acids. Having an incomplete reaction will result in the biodiesel containing triglycerides, diglycerides, or monoglycerides. These compounds contain glycerol. Fuel with excessive free glycerol may plug the fuel filters and cause combustion problems in the diesel engine. In our case for formulating a drilling fluid glycerol contributes significantly to the viscosity of the base fluid, this higher viscosity of the base fluid has a negative impact on the rheology of the drilling fluid and is generally undesirable. On the other hand, residual methanol, even as little as 1%, can have a negative impact on flashpoint of the final biodiesel product as it can lower it from 170°C to less than 40°C, causing serious safety risks to drilling operations. Several studies were conducted to ensure that single phase transesterification as conducted in this paper conforms to these standards. Gas chromatography conducted on samples during the reaction, and on the final product confirm that more than 99% of the oil was converted to methyl ester within the first 5 minutes of the reaction, and that the final product conforms to both the European and the ASTM standards. [32, 34] 2.3. Measuring base fluid properties for mud formulation

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The specific gravity of the final fluid product was measured using a hydrometer and found to be 0.865 for the palm oil (PFAME). A comparison with a current low toxic OBM base fluid used in Egypt (which is Exxon Mobile’s ultra-low toxicity Escaid-110®) was conducted.

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In order to develop an understanding of how the new oil’s viscosity behaves with temperature, the two oils were first refrigerated. A sample of each refrigerated; fluid Escaid-110® and Palm oil fatty acid methyl ester (FAME) were and then run through a standard Fann 35 viscometer to measure their flow characteristics. During refrigeration of the base oils in preparation for the test, the palm oil ester remained liquid up to -5 °C (23° F), and started to solidify at -6 °C (21.2°F). Escaid-110® freezes at -48 °C (-54°F), according to its data sheet. Measuring the flow characteristics at different temperatures for the ester and the low toxic oil, the following was found: The lowest values were for the low toxic oil (Figure 1), followed by the palm oil ester (Figure 2). These base fluids are Newtonian fluids; i.e., their viscometer readings should form straight lines intercepting at zero. However, as can be seen from Figures 1 and 2, the behavior deviates from the ideal Newtonian one. This is due to the limited accuracy of the Fann 35 viscometer and fluctuations in the test temperature as a result of equipment limitation. Straight lines were fitted to the experimental data to represent fluid behavior in a more accurate manner.

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The palm oil ester (PFAME) had viscometer dial readings that were double that of the low toxicity oil (Escaid-110®). A special formula was designed to accommodate the ester’s high viscosity, which contained significantly less viscosifiers and rheological modifiers.

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6 5

40 F 60 F

4

80 F

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Shear stress lb/100ft^2

7

3

120 F

2

150 F

0 0

200

400

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Shear rate Sec^-1

Figure 1: Escaid-110® thermal behavior.

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80 F 120 F

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Shear stress lb/100ft^2

12

150 F

2 0

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200

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600

800

1000

Shear rate Sec^-1 Figure 2: PFAME thermal behavior

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2.3.1. Compatibility tests

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A compatibility test was run on the ester with all the drilling fluids chemicals to be used in this experiment. Polymeric filtration control agents were found to be much more effective than gilsonite and asphaltene containing agents. The ester was also found to be sensitive to the presence of lime. 2.3.2. Effect of lime

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Lime is usually added to OBM to form soaps and emulsifiers through the saponification reaction with fatty acid emulsifiers [1]. Since our base fluid is a fatty acid ester, it undergoes a reaction with lime, and forms a calcium soap. A simple comparison test was conducted to quantify the effect of lime on FAME. 200 cc of FAME and 200 cc of Escaid-110® were placed in two separate mixing cups and were treated with 10 gm of Suremul®, the primary emulsifier for the fluid system being built, and 5 gm of lime. They were then mixed with 50 cc of 25% by weight calcium chloride (CaCl2) brine each. The mixture was agitated with a Hamilton Beach mixer for 30 minutes. The two samples were then left overnight in glass beakers.

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The emulsion stability was measured directly after the mixing process and was found to be 214 V for Escaid-110® and 703 V for the FAME. The next day, the Escaid-110® sample separated into two separate phases with the Escaid-110® on top and the brine at the bottom. By contrast, the FAME sample had undergone a saponification reaction that generated a gel-like structure that kept the two phases in emulsion, and yielded an increase in emulsion stability to 889 V.

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The lime reacted with the FAME to create a calcium soap. Even though this process enhanced the emulsion stability, the formed soap has a gel-like structure which contributes to the drilling fluid’s gel strength, giving very high values under high temperature high pressure (HTHP) conditions. After this experiment, it was decided to remove lime from all future fluids design, and treat it as a contaminant to maintain the fragile gel strength required in deep water applications.

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3. Drilling fluid design and analysis 3.1. Drilling fluid formulation In order to establish a performance benchmark, a reference Escaid-110® sample was mixed (Table 1), and an optimized formula was designed for the PFAME fluid based on the compatibility tests and industry standard formulas, aiming to match the performance of the benchmark sample. It was specifically designed to compensate for the PFAME’s relatively high viscosity and intolerance to lime (Table 2).

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PRODUCT/ Sample Composition Mix Order

161.55

1A

Salt

18.17

2B/5A

60 min

Gelling agent High grade organo. Clay Support emulsion

1

8A

15 min

9A

15 min

SUREMUL

Emulsifier

8

SUREWET

Wetting agent Flat Rheology additive Rheology modifier

3

1.5

EMI 943

Temp. Extender

1

ECOTROL

Filtration control

1

Water

Water phase

50.87

Barite

Weight material

263.91

Bridging agent

10

VG Plus Lime

RHEFLAT RHETHIK

Safe Carb

3 5

2

2A

15min

3A

30 min

4A

30 min

6A

15 min

7A

15 min

11A

15 min

10A

15 min

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VG Supreme

1B

13A

60 min

12A

15 min

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CaCl2

Time (min)

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PPB Base fluid

ESCAID-110

Table 1: Escaid-110® based flat rheology reference sample formula. PRODUCT/ Sample Composition FAME

Base fluid

CaCl2

Salt

VG Supreme

SUREMUL SUREWET RHEFLAT RHETHIK EMI 943 ECOTROL Water

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Barite

Safe Carb

1A

Time (min)

18.42

2B/4A

60 min

0.25

7A

15 min

0.5

8A

15 min

-

-

-

Emulsifier

12

2A

30 min

Wetting agent Flat Rheology additive Rheology modifier

3

3A

30 min

2

5A

15 min

1.5

6A

15 min

Temp. Extender

1

10A

15 min

Filtration control

1

9A

15 min

Water phase

51.59

1B

Weight material

247.31

12A

60 min

Bridging agent

10

11A

15 min

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Lime

Mix Order

Gelling agent High grade organo. Clay Support emulsion

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VG Plus

PPB

181.68

Table 2: PFAME based flat rheology fluid formula.

3.2. Drilling fluid testing and results The formulae were tested according to the API recommended practice 13B-2 for the following: 1. Rheology at 60, 80, 100, 120, and 150°F to demonstrate its flat rheology profile. 2. HTHP filtration at 500 psi differential pressure and 300°F (149°C). 3. HTHP rheology (up to 250°F (121°C) and 10000 psi). 4. Emulsion stability (at 150°F, 66°C). 9

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The same series of tests were repeated for the PFAME formula after it was hot rolled at 285°F (141°C) for 16 hours to simulate the impact of the average working conditions for the mud.

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The PFAME sample, before hot rolling, showed excellent emulsion stability, good rheology values compared to the reference sample, and very tight HTHP filtration control (Table 3, and 4). The amount of filtrate collected in 30 minutes was negligible and the filter cake quality was as good as that attained with current high performance, low-toxicity drilling fluids with a thickness of only 1/32 of an inch. Properties Hours

PERIOD AGED DYNAMIC/STATIC

BHR

BHR

12.5

12.5

60

80

600 RPM

73

70

300 RPM

44

41

200 RPM

32

100 RPM

23

6 RPM

12

3 RPM

9

Mud Weight

ppg ºF

Rheology Temp.

lbs/100ft2

GELS 10''/10' APPARENT VISC.

cP

PLASTIC VISC.

cP

YIELD POINT

lbs/100ft2

LSYP FILTRATION

lbs/100ft2

Δ Pressure Temp. Cake HTHP ES

ml

1.2

psi ºF

500

1/32"

BHR

BHR

12.5

12.5

12.5

100

120

150

62

56

47

37

33

29

30

27

22

19

21

19

16

16

11

9

10

10

10

8

9

9

16/21

14/18

13/17

12/17.

12/18.

36.5

35

31

28

23.5

29

29

25

23

18

15

12

12

10

11

6

9

7

8

8

300

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HTHP Fluid Loss

BHR

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Test Condition

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ºF

Temp. Mud Weight and Rheology

1

mV

256

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Table 3: Escaid-110® based flat rheology reference sample test results.

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Properties Hours

PERIOD AGED DYNAMIC/STATIC

ºF

Temp. Mud Weight and Rheology

BHR

BHR

BHR

BHR

BHR

12.5

12.5

12.5

12.5

12.5

60

80

100

120

150

600 RPM

117

90

70

62

300 RPM

67

53

41

200 RPM

50

39

30

100 RPM

32

25

20

6 RPM

13

11

9

3 RPM

12

10

8

Mud Weight

ppg ºF

Rheology Temp.

54

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Test Condition

37

34

27

24

19

17

9

9

8

9

16/22

14/19

11/17.

13/17

11/16.

APPARENT VISC.

cP

58.5

45

35

31

27

PLASTIC VISC.

cP

50

37

29

25

20

YIELD POINT

lbs/100ft2

17

16

12

12

14

LSYP FILTRATION

lbs/100ft2

11

9

7

7

9

Δ Pressure Temp.

ml

0

psi ºF

500

1/32"

Cake HTHP

mV

ES

300 1

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HTHP Fluid Loss

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lbs/100ft2

GELS 10''/10'

1600

1087

Table 4: PFAME based flat rheology fluid test results (BHR).

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The sample also achieved an acceptable flat rheology profile similar to that achieved with the reference benchmark sample (Escaid-110®). The test results were represented graphically in Figure 3, 4, 5, 6, and 7. The values for the 6 RPM reading, the yield point and 10 min gel strength for the sample before and after hot rolling follow the same trend as the bench mark sample.

Figure 3: Flat rheology profile for reference sample (Escaid-110®).

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Figure 4: Flat rheology profile for PFAME (BHR).

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Figure 5: Flat rheology profile for PFAME (AHR).

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30 25 20 15 10 5 0

2

3

4

5

6

11

18

14

16

13

14

10 min Gel lb/100 ft^2

18

24

22

26

18

17

6 RPM

11

14

13

14

10

8

PV Cp

23

24

23

24

23

25

4.00 2.00 0.00

2

3

K lbf - s^n / 100 ft^2

4.13

5.50

5.03

n

0.29

0.27

2 at 120 ° F and 4000 psi

1at 120 ° F and 0 psi

4

5

6

5.05

4.13

2.62

0.26

0.28

0.30

0.41

3 at 180 ° F and 4000 psi

4at 180 ° F and 8000 psi

5 at 250 ° F and 8000 psi

6 at 250 ° F and 10000 psi

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6.00

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1

YP lb/100 ft^2

n & K Values

PV,Yp, 10 min Gel,& 6 RPM Values

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35 30 25 20 15 10 5 0

1

2

3

4

5

6

12

12

9

13

12

10

10 min Gel lb/100 ft^2

8

8

7

7

4

4

6 RPM

6

8

7

8

4

5

23

33

22

26

16

19

YP lb/100 ft^2

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PV Cp

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PV, Yp, 10 min Gel,& 6 RPM Values

Figure 6: Escaid-110® based flat rheology fluid HTHP rheology graphical representation.

n & K Values

3.00 2.00 1.00 0.00

1

2

3

4

5

6

K lbf - s^n / 100 ft^2

1.64

2.55

2.20

2.62

1.21

1.20

n

0.47

0.44

0.40

0.41

0.49

0.49

1 at 120 ° F and 0 psi

2 at 120 ° F and 4000 psi

3 at 180 ° F and 4000 psi

4 at 180 ° F and 8000 psi

5 at 250 ° F and 8000 psi

6 at 250 ° F and 10000 psi

Figure 7: PFAME Based flat rheology fluid HTHP rheology graphical representation.

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As can be seen in the charts, PFAME retains its flat rheology at high temperatures and pressures that are expected to be encountered in HTHP deepwater wells showing a performance similar to current drilling fluids standards. When comparing the HTHP rheology values to that of the Escaid-110®, the difference is mainly due to the difference in viscosity of the base fluid.

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To increase the confidence level in the filtration control results, a sample was run through the permeability plugging tester (PPT) against a 20-micron ceramic disc at 300°F (149°C) and 1000 psi differential pressure. The amount of filtrate collected in 30 minutes was 3.9 cc (Table 5), and the filter cake formed on the ceramic disc was of excellent quality with a thickness of 0.5 x 1/32 inch.

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Table 5: PPT results

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Figure 8: PPT spurt loss.

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the hot rolling process show very little effect on PFAME mud properties, unlike vegetable OBMs formulated with regular palm oil, which become very thick and lose filtration control after hot rolling [8]. The PFAME sample retained its flat rheological profile, its emulsion stability, and its tight filtration control. However, it has shown a barite sag tendency.

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3.3. Weight up and contamination tests on PFAME high performance flat rheology fluid

Rev-dust Sea water 0.78 1.02 Table 6: VSST test results

Weight up 0.46

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A larger volume of the formula was mixed and a series of contamination tests were run to determine how the drilling fluid would react to the drilling environment. Tests for two distinct contaminants were run, a sample was contaminated with 10 ppb Rev-dust to simulate drilled solids, and the other was contaminated with 5% by volume sea water. A sample was weighted up to 18 ppg. A viscometer sag shoe test (VSST) was run on all samples to measure their sag tendency (Table 6).

The sample contaminated with Rev-dust showed a slight increase in rheology, while retaining its flat rheological profile. Emulsion stability and filtration control were unaffected, while an improvement in the sag index was observed.

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On the other hand, the sample contaminated with sea water had an increase in rheology, while retaining a flat rheology profile, but suffered a reduction in both filtration control and emulsion stability. A volume of 4.2 cc of filtrate was gathered in 30 minutes, but the filtrate had no free water, and the emulsion stability dropped to 487 mV. The sag index was almost unchanged. This behavior is consistent with commercial high-performance flat rheology drilling fluids and, therefore, normal treatments in such situations will be most effective.

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To establish a solids-loading trend for the rheology, the sample that was weighted up to 18 ppg was first weighted up to 15.5 ppg and required its oil water/ratio adjusted to 85/15. It was then weighted up to 18 ppg which required its oil/water ratio adjusted to 90/10. The rheology was measured for at the initial mud weight of 12.5 ppg, 15.5 ppg, and 18 ppg (Figure 9). The results show a significant increase in low-end temperature rheology. Further testing showed that the 18 ppg sample lost its flat rheology profile for the low-end temperatures, but kept it for the high end. A possible solution to keep the low-end temperatures’ rheology within the desired values is to increase density by either use of a denser weight material such as manganese tetroxide, or to use micronized barite for the weighting up process instead of regular-grade barite. This is to reduce the negative effect of solids loading that is coupled with the relatively high viscosity of the base fluid at low temperatures. Another possible solution is blending the base oil with a less viscous environmentally-acceptable base oil to control the effects of the relatively high viscosity (Figure 10). 15

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Solids Loading Trend 60 50

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Figure 9: Solids loading trend chart

Figure 10: Combined flat rheology profile (Contamination test and weight up results).

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3.4. High temperature hot rolling and static aging.

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The successful sample was prepared for further testing after extended static aging and hot rolling. The sample was placed in the oven at 350°F (177°C) and 100 psi and aged for 24 hours. Both sample, the one aged statically and the one hot rolled, severely deteriorated at these conditions. Once the aging cells were opened a characteristic burned oil odor was detected. The samples separated into 2 distinct layers, a darkened burned oil layer on surface, and a concentrated solid layer in the bottom. No further tests were conducted, and it was concluded that the formulated fluid was not suitable for such high temperature applications.

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3.5. Hydraulic simulations

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All the rheology and viscosity data that was measured was used to construct a fluid model in a commercial software suite, and a simulation of critical cases that are usually encountered during drilling and tripping was conducted to check if the fluid will perform within industry tolerances.

Figure 11: Fluid rheological model

A well profile was designed to subject the fluid to fluid to actual field conditions. The well design included: A water depth of 650 m, pore pressure of 12.2 ppg, fracture gradient of 14.3 17

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ppg, ambient temperature of 26.6°C (80°F), sea bed temperature of 1.6°C (35°F). The section total depth is 3100 m, with well geometry as shown in Figure A1, and a circulating temperature profile as shown in Figure A2.

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The formulated drilling fluid was found to match the modified power law as seen in Figure 11. From the Drilling performance chart (Figure A3) we can clearly see that the fluid maintains a flat rheology profile throughout the different regions of the well, with very little variance in YP & LSYP with changes in temperature and pressure, which helps minimize the ECD (maximum estimated ECD is 12.81ppg with the hole loaded with cuttings) and maintains a good hole cleaning index even in the low annular velocity region inside the marine rise

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Breaking circulation pressure is limited to 124 psi which is equivalent to 12.59 ppg (Figure 12) due to the flatness of and fragileness the fluids gel strength, this contributes to reducing the risk of fracturing the formation when starting circulation.

Figure 12: Calculated pressures

From the swab and surge simulations we observe that the fluid maintains a minimum ECD of 12.4 ppg (Figure A4) while pumping out at 250 GPM, and 12.39 ppg while tripping out without the pump (Figure A5), a maximum ECD of 12.73 ppg while washing down with 250 GPM (Figure A6), and 12.72 ppg for tripping in without pumping (Figure A7). These values will maintain well control and will prevent fracturing the formation as long as a fixed tripping speed that doesn’t exceed 1 m/s is kept, at this speed tripping out of the hole will require 5.18 hours which is a reasonable time for the well depth.

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The surge pressure while running the casing (Figure A8) will result in a maximum ECD of 14.2 ppg which is very close to the 14.3 ppg leak off test result, this maximum value will occur when the new casing string starts to come out inside the open hole, in this case running speed must be controlled to ensure the prevention of fracturing the formation.

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According to the simulation the fluid was able to maintain a flat rheology profile and consequently an ECD within the proposed window for all the situations. It was able to maintain good hole cleaning throughout the different zones of the well regardless of the local temperature at these zones especially at the low annular velocity region in the marine riser without impacting the hole cleaning at the bottom of the well.

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During tripping and running casing the fragile gel strength of the fluid allowed it to generate little swab and surge pressures, and consequently avoid undesirable well control or loss of circulation events. The fluid comes close to the proposed fracture gradient while running the casing but this can be mitigated by reducing the running speed or by using a surge reduction tool, in case that the reduced speed is putting a negative impact on the well economics. This simulation shows that this fluid is capable of handling the challenge and can meet all the requirements of deep-water wells. 3.6. Shelf life

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FAME is safe to store and its properties should conform to the industrial standards after an extended period of storage. However, there are several key factors that need to be considered. Chief among these factors, the storage temperature, the relatively low oxidative stability of FAME and material compatibility. Since the freezing point of FAME is very low compared to mineral oils it is recommended to keep it stored between 7° and 10°C. Even in extremely cold climates, underground storage of pure FAME usually provides the storage temperature necessary for preventing crystal formation. FAME stability is an important property for prolonged storage periods. Poor stability leads to an increased acid value and viscosity. It may also lead to the formation of gums and sediments. Therefore, if the storage duration is more than 6 months, it should be treated with an antioxidant. Water contamination is also a major issue. Contamination will lead to biological growth, which can be reduced by using biocides. Storage tanks made of aluminum, steel, Teflon, and fluorinated polyethylene or polypropylene are I deal for FAME. The tanks should be cleaned prior to storage to ensure favorable conditions for storage [35] 4. Conclusions

The viscosity of FAME is relatively higher than low toxic mineral oils, however, this can be overcome by proper engineering of drilling fluids formulation. Fluids can be formulated from FAME with oil/water ratios that are adjusted according to the desired rheology and density. Reducing the amounts of organophilic clays and using rheological modifiers in conjunction with adjusting the oil/water ratio enabled the formulation of an 18 ppg drilling fluid with relative 19

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ease. Parameters did not deteriorate after hot rolling at 285°F (141°C) for 16 hours, and were stable up to 250°F (121°C) and 10000 psi, but the fluid disintegrated after ageing at 350°F (177°C). A flat rheology profile was established using FAME as the base fluid for high performance oil based drilling fluids. The variation in gel strength, yield point, and a 6-RPM with temperature is within the industry accepted tolerances. The produced fluid shows filtration control results when a polymeric fluid loss reducer is used that are far superior to current technology. It proved to be as resistant to common drilling fluid contaminants (sea water and drilled solids) as conventional fluids, but it is sensitive to the presence of lime. This means that special precautions must be used during cementing operations to prevent contaminating the fluid with lime. The fluid lost its flat rheology profile for the low-end temperature values at high densities; this requires careful design of high density fluids to maintain the desired parameters.

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The testing results are mostly in agreement with previous publications in this field, and differences are mainly due to the different fluid design methodologies. According to the hydraulics simulation performed the downhole behavior of the formulated fluid is expected to closely match that of current industry fluids. The flat rheology profile and high stability under simulated downhole conditions suggest that the fluid will maintain a low ECD and have a consistent cuttings-carrying capacity in the different temperature conditions encountered during drilling deep-water HTHP wells. 5. Acknowledgments

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A special thanks to the staff of the Faculty of Engineering at Cairo University for their help and support, the staff at MI-SWACO Egypt for their support with lab equipment and drilling fluids chemicals, and the editor and reviewers of this journal for their constructive feedback.

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6. References

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[1] The M-I SWACO Drilling fluids manual, version 2.1. 2006. [2] Schlemmer, R, and Jonathan Sheldon, Sarawak Shell “Flat-Rheology Mud for Deepwater Wells. A New, Simplified Drilling Fluid System with Nearly Temperature –Independent Rheological Properties Dramatically Reduces Lost Circulation in Wells Drilled in South China Sea”, World Oil, 2010 Vol. 231 No.1, Jan [3] Schlemmer, R. and S. F. Khor, “Development of deepwater drilling fluid and performance comparison with a conventional fluid for use offshore Sarawak,” presented at the Petrotech International Oil & Gas Conference, New Delhi, Jan. 15–19,2007 [4] Schlemmer, R. and G. Phoon, “Field use of a flat rheology drilling fluid and fine grind barite for deep water wells,” presented at Petrotech, New Delhi, Jan. 11–15, 2009. [5] Van Oort, et al. “New flat-rheology synthetic-based mud for improved deepwater drilling,” SPE 90987 presented at SPE ATCE, Houston, Sept. 26–29, 2004. [6] A.McLean, et al “ The Top 10 Mud-Related Concerns in Deepwater Drilling Operations Revisited After 10 Years”, AADE-10-DF-HO-04, presented at AADE Fluids Conference and Exhibition, Huston, Texas 6-7 April, 2010 [7] United States Environmental Protection Agency “Development Document for Final Effluent Limitations Guidelines and Standards for Synthetic-Based Drilling Fluids and other Non-Aqueous Drilling Fluids in the Oil and Gas Extraction Point Source Category” Office of Water EPA-821-B-00-013 Dec 2000 [8] Adewale Dosunmu, and Ogunrinde Joshua “Development of Environmentally Friendly Oil Based Mud Using Palm-Oil and Groundnut-Oil”, SPE 140720, presented at 34th annual SPE International Conference and Exhibition, Tinapa-Calabar, Nigeria 31 July – 7 August 2010 [9] Adesina, F., David, O. and Olugbenga, F. “Investigating the Cuttings Carrying Capacity and the Effect of Drilling Cutting on Rheological Properties of Jatropha Oil-Based Mud.” SPE 167551 presentation at the Nigeria Annual International Conference and Exhibition held in Lagos, Nigeria. 2013. [10] Yassin, A.M; Kamis, A and Abdullah, M.O. (1991). Palm oil diesel as a base fluid in formulating oil based drilling fluid. Paper SPE 23001. pp. 190 –206. [11] Ismail, A.R. “Managing the environmentally friendly drilling fluids in petroleum industries.” The 2nd International Conference on Disaster Management, Surabaya, Indonesia, 3-5 May 2001. [12] Adesina, F; Anthony, A; Gbadegesin, A; Eseoghene, O; Oyakhire, A. “Environmental Impact Evaluation of a safe Drilling Mud.” SPE 152865 presented at the SPE Middle East Health, Safety, Security and Environment Conference and Exhibition held in Abu Dhabi, UAE, 2-4 April 2012. 21

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[13] Akintola, S., Oriji, A.B. and Momodu, M. “Analysis of Filtration Properties of Locally Sourced Base Oil for the Formulation of Oil Based Drilling Fluids.” Scientia Africana, 2014. Vol. 13, No. 1. P. 171–177, [14] Adesina, F., David, O. and Olugbenga, F. (2013). Investigating the Cuttings Carrying Capacity and the Effect of Drilling Cutting on Rheological Properties of Jatropha Oil-Based Mud. Paper SPE 167551 presentation at the Nigeria Annual International Conference and Exhibition held in Lagos, Nigeria. [15] Fadairo A.S., Adesina, A. A., Ameloko, A. and Olugbenga, F. “Modeling the Effect Of Temperature On Environmentally Safe Oil Based Drilling Mud Using Artificial Neural Network Algorithm.” Petroleum & Coal 54 (1) 1–12. 2012. [16] Fadairo, A.; Falode, O.; Ako, C., Adeyemi, A. and Ameloko, A. “Novel Formulation of Environmentally Friendly Oil Based Drilling Mud. New Technologies in the Oil and Gas Industry.” INTEC Open Science. 2012. [17] Anawe Paul A.L; Efeovbokhan, V. E; Ayoola, A. A; Akpanobong O. A. “Investigating Alternatives to Diesel in Oil Based Drilling Mud Formulations Used in the Oil Industry”. Journal of Environment and Earth Science 2014, Vol.4, No. 14, [18] Okie-Aghughu, O., Aluyor, E.O. and Adewole, E.S. “Use of rubber seed oil as base fluid in the formulation of oil based drilling mud.” Advanced Materials Research 2013 Vol. 824 pp 401–405. Trans Tech Publications, Switzerland. [19] Auta, M. “Extraction and Characterization of Drilling Fluid from Castor Oil.” International Journal of Innovation and Applied Studies June 2013, Vol. 3 No. 2 p. 382–387 [20] Apaleke, A.S., Abdulaziz, A., and Hossain, M.E. “State of The Art and Future Trend of Drilling Fluid: An Experimental Study.” SPE-153676 prepared for presentation at the Latin America and Caribbean Petroleum Engineering Conference 16-18 April 2012 Mexico City, Mexico [21] Setyawan, W; Ashfahani, A.S; Fajarwati, K; Marbun, B., Manurung, R. “Alternative use of castor oil for vegetable oil based mud environmentally friendly potential domestic oil based mud.” Proceedings, Indonesian Petroleum Association. Thirty-Fifth Annual Convention & Exhibition. 2011. [22] Fechhelm, R. G., Gallaway, B. J. and Farmer, J. M. “Deepwater Sampling at a Synthetic Drilling Mud Discharge Site on the Outer Continental Shelf, Northern Gulf of Mexico”, SPE 52744. Pages 509 –513 in: 1999 SPE/EPA Exploration and Production Environmental Conference. Austin, TX. (1999). [23] Friedheim, J. E. and Conn, H. L. “Second Generation Synthetic Fluids in the North Sea: Are they better? IADC/SPE 35061. Pages 215–228 in: IADC/SPE Drilling Conference. New Orleans, 12-15 March 1996.

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[24] Mohd Kassim Salleh and Stephan von Tapavicza “Palm Oil Derived Esters- an Environmentally Safe Drilling Fluid” Oil Palm Industry Economic Journal – Vol. 5 No. 1, Jun 2005 [25] Stephan von Tapavicza, “Special Report: Vegetable Esters Make Drilling Fluids More Environmentally Friendly” Oil and Gas Journal-Vol. 103, Issue 22, Jun 2005 [26] R.A.M. Amin, et al. “Joint Development of An Environmentally Acceptable Ester-Based Drilling Fluid” SPE 132693, presented at Trinidad and Tobago Energy Resource Conference, Port of Spain, Trinidad, 27-30 June 2010 [27] Aliyu A. Sulaimon, Bamikole J. Adeyemi, Mohamad Rahimi. “Performance enhancement of selected vegetable oil as base fluid for drilling HPHT formation” Journal of Petroleum Science and Engineering 152 2017 49–59 [28] A.R. Ismail, A. Kamis, K.S. Foo.” Performance of the Mineral Blended Ester Oil Based Drilling Fluid Systems” presented at the Petroleum Society’s Canadian International Petroleum Conference 2001, Calgary, Alberta, Canada, June 12 – 14, 2001. [29] Degouy, D., Argillier, J. F., Demoulin, A. and Velghe, F. “Biodegradable Muds: An Attractive Answer to Environmental Legislations Around Offshore Drilling.” Paper SPE 26737 presented at the Offshore European Conference held in Amsterdam, Sept. 7-10, 1993. 507514. [30] Peresich, R. L., Burell, B. R. and Prentice, G. M. “Development and Field Trial of a Biodegradable Invert Emulsion Fluid.” Paper SPE/IADC 21935 presented at the 1991 SPE/IADC Drilling Conference held in Amsterdam, March 11- 14. 333-340. [31] Hodder, M. H., Dowrick, K., Navage, P. and Abdul Azis Ariffin “Palm Oil Derived Systems for Use in the Petroleum Industry as Drilling Fluids.” PORIM Intl. Palm Oil Conference. 186192. [32] Boocock David G.B. et al. “Fast Formation of High-Purity Methyl Esters from Vegetable Oils”, JAOCS, Septembre1998, Vol. 75,No. 9,P.1167-1171 [33] Noureddini, Hossein; Harkey, D; and Medikonduru, V, "A Continuous Process for the Conversion of Vegetable Oils into Methyl Esters of Fatty Acids" 1998. Papers in Biomaterials. Paper 12. [34] Dennis Y.C. Leung *, Xuan Wu, M.K.H. Leung “A review on biodiesel production using catalyzed transesterification” Applied Energy 87 (2010) 1083–1095

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Appendix A: Hydraulics results

Figure A1: Well geometry

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Figure A2: Temperature profile

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Figure A3: Drilling performance

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Figure A4: Swab simulation while pumping out

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Figure A5: Swab simulation without pumping out

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Figure A6: Surge simulation while pumping

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Figure A7: Surge simulation without pumping

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Figure A8: Surge simulation for running casing

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Highlights

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Formulation of high performance fluids is possible using Fatty acid methyl esters (FAME). Formulated fluids can have a flat rheology profile if engineered properly FAME Based Fluids are sensitive to lime FAME Based Fluids need special design when a high density fluid is required

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