阅读说明：本技术 用于反向乳化钻井液的废植物油类乳化剂 (Waste vegetable oil emulsifier for reverse emulsion drilling fluid ) 是由 乔弟巴苏·拉马萨米 姆迪·阿马努拉 穆杰塔巴·M·艾莎哈蒂 于 2018-11-06 设计创作，主要内容包括：描述了用作钻井泥浆主要乳化剂的废植物油类乳化剂。由废植物油的烷基酯制备第一乳化剂。废植物油为已经用于在制备第一乳化剂之前的过程的植物油。将一定量的第一乳化剂加入到油基钻井液中。将一定量的活化剂加入到油基钻井液中。活化剂被配置成活化该乳化剂以使乳液稳定。将一定量的增粘剂加入到油基钻井液中。将一定量的第二乳化剂加入到油基钻井液中。将一定量的增重材料加入到油基钻井液中。在钻井操作中使用所得油基钻井液以在地下区域中钻出井眼。(Waste vegetable oil-based emulsifiers are described for use as the primary emulsifier in drilling muds. The first emulsifier is prepared from alkyl esters of waste vegetable oil. The waste vegetable oil is a vegetable oil that has been used in a process before the first emulsifier is prepared. An amount of a first emulsifier is added to the oil-based drilling fluid. An amount of activator is added to the oil-based drilling fluid. The activator is configured to activate the emulsifier to stabilize the emulsion. An amount of a viscosifier is added to the oil based drilling fluid. An amount of a second emulsifier is added to the oil-based drilling fluid. An amount of weighting material is added to the oil-based drilling fluid. The resulting oil-based drilling fluid is used in a drilling operation to drill a wellbore in a subterranean zone.)

1. A method, the method comprising:

preparing a first emulsifier from an alkyl ester of a waste vegetable oil, wherein the waste vegetable oil is a vegetable oil that has been used in a process prior to preparing the first emulsifier;

adding an amount of the first emulsifier to an oil-based drilling fluid;

adding an amount of an activator to the oil-based drilling fluid, the activator configured to activate the emulsifier to stabilize an emulsion;

adding an amount of a viscosifying agent to the oil-based drilling fluid;

adding an amount of a second emulsifier to the oil-based drilling fluid;

adding a quantity of brine to the oil-based drilling fluid;

adding an amount of weighting material to the oil-based drilling fluid; and

the oil-based drilling fluid is used in a drilling operation to drill a wellbore in a subterranean zone.

2. The method of claim 1 wherein the ratio of the amount of the first emulsifier to the amount of the oil-based drilling fluid is from 4 pounds of first emulsifier/barrel of oil-based drilling fluid to 12 pounds of first emulsifier/barrel of oil-based drilling fluid.

3. The method of claim 1, wherein the ratio of the amount of activator to the amount of oil-based drilling fluid is approximately 4 grams activator per barrel of oil-based drilling fluid.

4. The method of claim 1, wherein the ratio of the amount of the viscosifying agent to the amount of the oil-based drilling fluid is approximately 4 grams viscosifying agent per barrel of oil-based drilling fluid.

5. The method of claim 1 wherein the ratio of the amount of the second emulsifier to the amount of the oil-based drilling fluid is approximately 6 grams second emulsifier/barrel of oil-based drilling fluid.

6. The method of claim 1, wherein the ratio of the amount of brine to the amount of oil-based drilling fluid is approximately 85 milliliters of brine per barrel of oil-based drilling fluid.

7. The method of claim 6, wherein the brine comprises an amount of calcium chloride dissolved in water.

8. The method of claim 7, wherein the brine comprises 61 grams of calcium chloride per 85 cubic centimeters of water.

9. The method of claim 1, wherein the ratio of the amount of weight material to the amount of the oil-based drilling fluid is approximately 161 grams weight material per barrel of oil-based drilling fluid.

10. The method of claim 1, wherein using the oil-based drilling fluid in a drilling operation to drill a wellbore in a subterranean region comprises: flowing the oil-based drilling fluid through the wellbore while drilling through the subterranean zone.

11. A method, the method comprising:

an emulsifier which cleaves ester groups of methyl esters of waste vegetable oil to produce said waste vegetable oil;

adding a caustic soda solution to the methyl ester to produce a mixture;

heat treating the mixture;

adjusting the pH of the mixture resulting in the formation of an aqueous phase and a non-aqueous phase; and

separating the aqueous phase from the non-aqueous phase.

12. The method of claim 11, wherein the caustic soda solution comprises an alkoxide dissolved in a solvent.

13. The method of claim 11, wherein the alkoxide comprises sodium hydroxide.

14. The method of claim 11, wherein the solvent comprises water.

15. The method of claim 11, further comprising agitating the mixture during the heat treating the mixer.

16. The method of claim 11, wherein the mixture is heated to a temperature above room temperature.

17. The method of claim 11, wherein the temperature is approximately 60 ℃.

18. The method of claim 11, wherein adjusting the pH of the mixture comprises adding an acid.

19. The method of claim 11, wherein the acid is approximately 31% hydrochloric acid.

20. The method of claim 11, wherein the adjusted pH of the mixture is approximately 4 to 5.

Technical Field

The present disclosure relates to drilling fluids, for example, wellbore drilling fluids for drilling wellbores in hydrocarbon formations.

Background

Drilling operations use wellbore drilling fluids for a variety of purposes including, for example, cooling drill bits, transporting wellbore cuttings from inside the wellbore to the surface, or the like. Drilling fluids are also used to reduce friction between the drill string and the casing or borehole wall by acting as a lubricating medium for the drill string while drilling the borehole. Drilling fluids may be classified into a variety of categories, for example, oil-based drilling fluids, water-based drilling fluids, or the like. Sometimes, additives are added to one or both types of drilling fluids to improve the performance of the drilling fluid.

Disclosure of Invention

This specification describes technology relating to waste vegetable oil-based emulsifiers for reverse emulsification of oil-based mud formulations.

Certain aspects of the subject matter described herein may be implemented as a method. The first emulsifier is prepared from alkyl esters of waste vegetable oil. The waste vegetable oil is a vegetable oil that has been used in a process before the first emulsifier is prepared. An amount of a first emulsifier is added to the oil-based drilling fluid. An amount of activator is added to the oil-based drilling fluid. The activator is configured to activate the emulsifier to stabilize the emulsion. An amount of a viscosifier is added to the oil based drilling fluid. An amount of a second emulsifier is added to the oil-based drilling fluid. An amount of weighting material is added to the oil-based drilling fluid. The resulting oil-based drilling fluid is used in a drilling operation to drill a wellbore in a subterranean zone.

This and other aspects may include one or more of the following features. The ratio of the amount of the first emulsifier to the amount of the oil-based drilling fluid may be from 4 pounds of first emulsifier/barrel of oil-based drilling fluid to 12 pounds of first emulsifier/barrel of oil-based drilling fluid. The ratio of the amount of activator to the amount of oil-based drilling fluid may be approximately 4 grams activator per barrel of oil-based drilling fluid. The ratio of the amount of viscosifier to the amount of oil-based drilling fluid may be approximately 4 grams viscosifier per barrel of oil-based drilling fluid. The ratio of the amount of the second emulsifier to the amount of the oil-based drilling fluid may be approximately 6 grams of second emulsifier per barrel of oil-based drilling fluid. The ratio of the amount of brine to the amount of oil-based drilling fluid may be approximately 85 milliliters of brine per barrel of oil-based drilling fluid. The brine may contain an amount of calcium chloride dissolved in water. The brine may contain approximately 61 grams of calcium chloride per 85 cubic centimeters of water. The ratio of the amount of weight material to the amount of oil-based drilling fluid may be approximately 161 grams weight material per barrel of oil-based drilling fluid. Using the oil-based drilling fluid in a drilling operation to drill a wellbore in a subterranean zone may include flowing the oil-based drilling fluid through the wellbore while drilling the subterranean zone.

Certain aspects of the subject matter described herein may be implemented as a method. Raw waste vegetable oil is esterified to produce methyl esters of raw waste vegetable oil. Caustic soda solution was added to the methyl ester to obtain a mixture. Heat treating the mixture. The pH of the mixture is adjusted resulting in the formation of an aqueous phase and a non-aqueous phase. The aqueous and non-aqueous phases are separated.

This and other aspects may include one or more of the following features. The caustic soda solution may include an alkoxide dissolved in a solvent. The alkoxide may include sodium hydroxide. The solvent may comprise water. The mixture may be stirred during the heat treatment of the mixture. The mixture may be heated to a temperature above room temperature. The temperature may be approximately 60 ℃. An acid may be added to adjust the pH of the mixture. The acid may be approximately 31% hydrochloric acid. The adjusted pH of the mixture may be approximately 4 to 5.

The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

Drawings

FIG. 1 is a schematic diagram of a drilling fluid circulation system.

FIG. 2 is a schematic diagram showing the flow of drilling fluid through the drill string and the annulus between the drill string and the wellbore.

FIG. 3 is a flow chart of an exemplary method for preparing an emulsifier using esterified waste vegetable oils.

FIG. 4 is a flow diagram of an exemplary process for preparing esterified waste vegetable oils.

FIG. 5 is a flow diagram of an example method for using an emulsifier prepared by the example method of FIG. 3 in an oil-based drilling fluid.

Like reference numbers and designations in the various drawings indicate like elements.

Detailed Description

For certain high temperature High Pressure (HPHT) sections of the borehole, water-based drilling fluids may not be a viable drilling fluid option due to extreme drilling conditions. For such HPHT sections, a reverse emulsified Oil Based Mud (OBM) may be used as the drilling fluid. OBM may also be used as a drilling fluid to stabilize the shale while drilling the active shale section. Certain oil-based drilling fluids, such as reverse emulsion OBMs, contain an emulsifier to create a stable emulsion of water in oil. Emulsifiers are a class of surfactants that have a hydrophilic head group and a hydrophobic tail (e.g., a long chain hydrophobic tail). The emulsifier can reduce the interfacial tension between the water phase and the oil phase, thereby realizing the stability of the drilling fluid.

The present disclosure describes an environmentally friendly (ecofrindly) emulsifier that can be used in oil based drilling fluids, such as reverse emulsion OBM or similar oil based drilling fluids. In some embodiments, the emulsifier is used as the primary emulsifier in a reverse emulsified oil-based mud formulation used as a drilling fluid in the HPHT section of a borehole, or as a drilling fluid to stabilize shale while drilling a highly active shale section. In general, emulsifiers may be used for OBMs used in rock formations where high friction and torque are desired, or in high extended reach wells (or both). Exemplary oil-water ratios and emulsifier concentrations in the formulations are described later. The emulsifier described herein is the primary additive used to reverse emulsify the OBM to create a stable water-in-oil emulsion. The emulsifier can reduce the interfacial tension between the water phase and the oil phase, thereby improving the stability of the drilling fluid.

Emulsifiers are a class of surfactants that have both a hydrophilic head group and a long-chain hydrophobic tail. In the present disclosure, vegetable oils, in particular used or processed vegetable oils (which may be obtained, for example, from the food industry), are used to prepare environmentally friendly emulsifiers. Vegetable oils are triglycerides extracted from plants. Triglycerides are esters of glycerol and three fatty acids. Depending on the source, vegetable oils contain mixtures of different types of fatty acids, for example, mixtures of saturated, monounsaturated, polyunsaturated, omega 3, omega 6 or omega 9 fatty acids. Most vegetable oils commonly used for cooking (e.g., olive oil, palm oil, sunflower oil, corn oil, peanut oil, or similar vegetable oils commonly used for cooking foods) contain one or more or all of these fatty acids. The presence of these different types of fatty acids makes vegetable oils a promising source of emulsifiers for drilling fluids. Vegetable oils that have been used for cooking and disposed of as waste can be used as a sustainable source of emulsifier synthesis. Virgin or unprocessed vegetable oils may also be used in the emulsifier synthesis described herein.

Fig. 1 is a schematic diagram of a drilling fluid circulation system 10. Fig. 2 is a schematic diagram showing the flow of drilling fluid through the drill string 12 and the annulus 40 between the drill string 12 and the wellbore 50. In a drilling situation using a drilling rig, the drilling fluid circulation system 10 circulates (or pumps) a drilling fluid (e.g., drilling mud) using one or more mud pumps. The drilling fluid circulation system 10 moves drilling fluid (mud, F) down the wellbore 50 through the drill string 12 and drill collars connected to the drill string 12. The drilling fluid exits through ports (nozzles) in the drill bit, picks up cuttings C and carries the cuttings from annulus 40 of wellbore 50. A mud pump 30 draws suction from the mud tank 22 and pumps the drilling fluid F out of the discharge pipe 24, up through the riser 26, through the hose 28, through the Kelly or top drive unit 31, and into the central bore of the drill string 12, drill collar and drill bit. Drilling fluid F and cuttings C return to the surface of annulus 40. At the surface, drilling fluid and cuttings exit the wellbore 50 through an outlet (not shown) and are sent to a cuttings removal system via a mud return line 60. At the end of the return line, drilling fluid F and cuttings C flow onto a shaker screen, such as a shale shaker 62. Finer solids may be removed using a sand trap (sand trap) 64. The drilling fluid may be treated with chemicals stored in the chemical tank 66 and then provided to the mud tank 22, where the process may be repeated.

The drilling fluid circulation system 10 delivers a large volume of drilling fluid under pressure for rig operations. The circulation system 10 delivers drilling fluid to the drill pipe (drill stem), flows down the drill string 12 and out through a drill bit attached to the lower end of the drill pipe. In addition to cooling the drill bit, the drilling fluid also hydrodynamically washes away debris, rock fragments, and cuttings generated as the drill bit advances into the wellbore 50. Thus, drilling fluids are an important part of component drilling operations that can flow through drilling system components, such as rotating coiled tubing, casing, or similar components, in different drilling operations, for example, under balanced drilling, overbalanced drilling, or similar drilling operations, to perform a variety of functional tasks and facilitate safe, problem-free, and economical drilling.

Fig. 3 is a flow diagram of an exemplary method 300 for preparing an emulsifier using esterified waste vegetable oils. In some embodiments, the emulsifier may be used with other wellbore fluids, for example, fracturing fluids, completion fluids, stimulation fluids, combinations thereof, or similar wellbore fluids. At 302, esterified waste vegetable oils are obtained. In some embodiments, methyl esters of waste vegetable oils are obtained. For example, waste vegetable oil (i.e., vegetable oil that has been used for cooking) is esterified to produce methyl esters.

At 304, a caustic soda solution is added to the methyl esters of the waste vegetable oil. In some embodiments, the caustic soda solution may be prepared by dissolving an amount of sodium hydroxide in water. In some embodiments, the caustic soda solution may be added to the methyl esters of the waste vegetable oil for a period of time sufficient to mix the caustic soda solution and the methyl esters. The caustic soda solution may be added at an optimal rate to delay the formation of the suspension, since the accelerated formation of the suspension will hinder the caustic reaction with the methyl ester. The reaction mixture was made into a suspension by adding caustic soda solution.

At 306, the mixture is heat treated. In some embodiments, the mixture may be stirred (or agitated) at a temperature above room temperature for a duration of time. Agitation promotes and increases contact between the caustic soda and the methyl ester. Heating at this temperature produces brownian motion of the reaction mixture and accelerates the reaction kinetics.

At 308, the heat-treated mixture is maintained in a static condition. In some embodiments, the agitation and heating of the heat-treated mixture can be stopped and the mixture allowed to cool to room temperature. No further heat treatment of the mixture is then required. Maintaining the mixture in a static condition allows the methyl groups to be cleaved to give the emulsifier.

At 310, water is added to the reaction mixture to separate the oil phase and the water phase, thereby separating the emulsifier. The volume of water may be 15% to 30% of the volume of oil initially taken for reaction.

At 312, the pH of the mixture is adjusted. In some embodiments, the pH is adjusted by adding an acid to the reaction mixture until the mixture pH reaches a level at which the oil phase separates from the reaction mixture.

At 314, the non-aqueous phase and the aqueous phase are separated. In some embodiments, the two phases are separated by: the reaction mixture was first transferred to a separation flask from which the aqueous phase was removed. In some embodiments, additional water may be added to the separation flask to wash and remove any residual inorganic salts in the non-aqueous phase. The remaining non-aqueous phase is subjected to static conditions along with the emulsion to defoam the emulsion. Defoaming may further release water, which may be removed as previously described. The non-aqueous phase from which the foam has been removed can be used as an emulsifier for use as described in this disclosure.

FIG. 4 is a flow diagram of an exemplary process 400 for preparing esterified waste vegetable oils. For example, the esterified waste vegetable oil prepared by practicing method 400 can be used to prepare an emulsifier by practicing method 300. In some embodiments, the additive may be used in a wellbore fluid, such as a drilling fluid (specifically, an oil-based drilling fluid), a fracturing fluid, a completion fluid, a stimulation fluid, combinations thereof, or the like.

At 402, waste vegetable oil comprising fatty acids is obtained. In some embodiments, the waste vegetable oil can be a processed vegetable oil produced as a byproduct of the food industry.

The waste vegetable oil can have a plastic viscosity (measured using a multi-speed rotational viscometer) greater than approximately 50 centipoise (cP) or 60.8 cP. The waste vegetable oil can have a plastic viscosity ratio of waste vegetable oil to mineral oil of greater than approximately 10 (e.g., approximately 11.18). As used in this disclosure, the term "substantially" allows for variations of up to 5% from any of the recited values. The waste vegetable oil may have a plastic viscosity ratio greater than approximately 20 relative to the plastic viscosity of refined oil produced by Safra (giba, saudi arabia) and used for offshore drilling. The waste vegetable oil may have a plastic viscosity ratio of approximately 24.12 relative to refined oil produced by Safra and used for offshore drilling. The waste vegetable oil may have a plastic viscosity ratio greater than approximately 10 relative to the plastic viscosity of the mineral oil used in the oil-based drilling fluid formulation.

The waste vegetable oil may comprise fatty acids and short chain alcohols. The short-chain alcohol may include at least one or more of methanol, ethanol, propanol, butanol, or combinations thereof. The fatty acid may include molecules averaging from approximately 16 carbon atoms to less than 20 carbon atoms.

At 404, impurities are removed from the waste vegetable oil. Impurities such as food residues may reduce the functional capability of the waste vegetable oil. In some embodiments, the waste vegetable oil can be filtered, such as by rapid filtration, at low pressure (e.g., approximately 5 pounds per square inch (psi) to approximately 10 psi). Alternative or additional methods may be used to remove impurities from the waste vegetable oil.

At 406, the feedstock slop oil is esterified. In some embodiments, the raw waste oil is esterified in the presence of a catalyst to produce alkyl ester products and triglycerides. The catalyst may include at least one of sodium hydroxide, potassium hydroxide, sodium alkoxide, potassium alkoxide, or a combination thereof. For example, the waste vegetable oil may be esterified with methanol in the presence of sodium hydroxide. At 408, the alkyl ester product and triglycerides are separated. Exemplary techniques for implementing portions of process 400 to produce esterified waste vegetable oils are described later. Alternative techniques can be implemented to produce esterified waste vegetable oils.

Removal of impurities and excess water

Low pressure filtration units can be used to remove impurities present in waste vegetable oil, such as burned and unburned food residues. The low pressure filtration unit may include filter paper having a pore size of less than 5 μm to remove impurities greater than 5 μm. A constant pressure of 5 to 10psi can be used on the low pressure unit for rapid filtration of a volume of waste vegetable oil. Other filter media or adsorbents capable of removing all impurities and excess water from the waste vegetable oil may be used instead of or in addition to the low pressure filtration unit. For example, a multi-unit filtration device may be used for removing impurities.

Determination of the amount of catalyst

The amount of catalyst required to process the waste vegetable oil can be determined by titration. To do so, for example, 1 milliliter (mL) of waste vegetable oil may be mixed with 10mL of 99.2% pure isopropanol. To this mixture may be added 2 to 3 drops of an indicator liquid (e.g., phenolphthalein or similar indicator liquid). The indicator liquid may be added dropwise to the agitated waste vegetable oil until the color becomes pink. After the end point, the mixture can be stirred for a while to check the permanence of the pink color. The titration experiment may be repeated three times to calculate the average amount of catalyst required to reach the endpoint. After determining the average value of sodium hydroxide (NaOH) based on the titration test results, a constant value (e.g., 3.5 grams (g)) may be added to determine the total amount of catalyst (e.g., 4.18g to 4.22g) required for 1 liter (L) of waste vegetable oil.

Esterification for removal of triglycerides

The viscosity of the waste vegetable oil can be reduced by esterifying the base oil with methanol to match the mineral oil viscosity. To do so, a volume of methanol (e.g., 20% of the original waste vegetable oil volume) and a mass of NaOH (e.g., 4.22g NaOH/liter of waste vegetable oil) can be mixed using a magnetic stirrer under dry conditions and then added to the waste vegetable oil in the vessel. The mixture can then be stirred using a magnetic stirrer for six hours to complete the interaction.

Sedimentation

The total reaction product may be kept in static conditions overnight to complete the settling of the glycerol and sludge at the bottom of the vessel. In the initial settling stage, the emulsion formed, e.g., due to the presence of some emulsion forming by-products in the ester layer, can be broken down by heating the processed cake at approximately 80 ℃ or adding approximately 10mL of acetic acid per liter of waste vegetable oil to break down and prevent the formation of the emulsion.

Separation and washing of the esterified oil

After complete settling, the top clear esterified oil was slowly decanted and washed with water for several hours while stirring with a magnetic stirrer. The esterified oil and wash water were then kept in static conditions overnight for effective separation of the oil and water phases. The separated oil phase was slowly decanted to remove it from the aqueous phase. The washing process is repeated, for example, twice.

Fig. 5 is a flow diagram of an example method 500 for using an emulsifier prepared by the example method of fig. 3 in an oil-based drilling fluid. The method 500 may be implemented partially, for example, at the surface of a wellbore, and partially, for example, within a wellbore. Additionally, method 500 may be implemented in part, for example, in a laboratory, and in part, for example, in the field. Further, the method 500 may be performed in part by a laboratory technician and in part by a field technician, such as a wellbore operator.

At 502, an emulsifier is prepared from alkyl esters of waste vegetable oil. For example, the emulsifier is prepared by performing the example method 300 previously described with reference to fig. 3. In some embodiments, the waste vegetable oil may be a vegetable oil that has been used in a process prior to the preparation of the emulsifier.

At 504, an amount of emulsifier is added to the oil-based drilling fluid to which the emulsifier has been added. The ratio of the amount of emulsifier to the amount of oil-based drilling fluid may range from 4 pounds (lbs) to 12lbs of emulsifier per barrel of oil-based drilling fluid. A barrel of oil-based drilling fluid contains approximately 159 litres of drilling fluid.

At 506, an amount of lime is added to the oil-based drilling fluid to which the previously mentioned components have been added. The ratio of the amount of lime to the amount of oil-based drilling fluid may be approximately 6g lime per barrel of oil-based drilling fluid. Lime activates the emulsifier, which then stabilizes the emulsion. The amount of lime is related to the amount of emulsifier. For example, the ratio of lime to emulsifier can be in the range of 1:1 to 1: 2.

At 508, an amount of viscosifier is added to the oil-based drilling fluid to which the previously mentioned components have been added. The ratio of the amount of viscosifier to the amount of oil-based drilling fluid may be approximately 4g viscosifier/barrel of oil-based drilling fluid. The viscosifier may be an organophilic clay. For example, the amount of tackifier may range from 2g to 6 g.

At 510, an amount of brine is added to the oil-based drilling fluid to which the previously mentioned components have been added. The ratio of the amount of brine to the amount of oil-based drilling fluid may be approximately 85 milliliters (ml) of brine per barrel of oil-based drilling fluid. Calcium chloride in brine is used in OBM to capture water from shale formations and stabilize the shale section. In some embodiments, the brine may include an amount of calcium chloride (e.g., approximately 61g) mixed with water (e.g., approximately 85 cubic centimeters).

At 512, an amount of weighting material is added to the oil-based drilling fluid to which the previously mentioned components have been added. The ratio of the amount of weight material to the amount of oil-based drilling fluid may be approximately 161 grams weight material per barrel of oil-based drilling fluid. The weight material may be an inert material added to the drilling fluid to adjust the density of the OBM to a desired level. The amount of weighting material depends on the desired mud density.

At 514, an oil-based drilling fluid mixed with the previously mentioned components is used in a drilling operation to drill a wellbore in a subterranean zone. For example, multiple barrels of oil-based drilling fluid are prepared, each barrel being mixed with the previously mentioned components. Multiple barrels are flowed through a subterranean zone while drilling a well in the subterranean formation.

Exemplary Process for preparing an emulsifier

Method 300 is performed as described herein to prepare an emulsifier. In the examples described herein and throughout this disclosure, the term "substantially" means that a deviation from the disclosed amount of 5% is allowable. Approximately 300 milliliters (mL) of methyl ester of waste vegetable oil was taken in a beaker with a magnetic stir bar and placed on a hot plate stirrer. The methyl ester was stirred at approximately 500 revolutions per minute (rpm). A caustic soda solution was prepared by dissolving approximately 15 grams (g) of sodium hydroxide in 50mL of water. The caustic soda solution was added to the methyl ester over a period of approximately two minutes, which caused the reaction mixture to become a suspension. The reaction mixture was stirred at approximately 60 ℃ for approximately 6 hours and then allowed to stand for approximately 16 hours, which resulted in a reaction mixture that was thickened and had a semi-solid consistency. Approximately 50mL of water was added to the mixture. Hydrochloric acid (approximately 31%) was added dropwise to the reaction mixture until the pH of the reaction mixture was approximately 4 to 5, after which the oil phase was separated from the reaction mixture. The reaction mixture was transferred to a separate flask. The aqueous phase separated from the non-aqueous phase by the emulsion layer was removed from the separation flask. Approximately 50mL of water was added to the remaining non-aqueous phase in the separation flask for washing and removing any inorganic salts remaining in the non-aqueous phase. The re-formed aqueous phase was removed from the separation flask and the procedure was repeated. The remaining non-aqueous phase is subjected to static conditions along with the emulsion to achieve defoaming of the emulsion. Water released upon defoaming is removed from time to time. Finally, the non-aqueous phase was collected as a colorless liquid.

Exemplary Process for making a reverse emulsion OBM

In one example, a total of 350ml of reverse emulsion OBM was prepared using 218ml of Safra oil as the base OBM. To the Safra oil was added 12ml of an emulsifier prepared by performing the previously described method 300. To this mixture was added 4ml of EZ-mul. EZ-Mul is a second emulsifier used as a wetting agent for solids. To this mixture 6g of activator, 4g of tackifier, 6g of emulsifier, 85ml of brine and 161g of weighting material were added. The brine was a solution of 61g calcium chloride in 85 cubic centimeters (cc) of water. The mixture was hot rolled at 300 degrees fahrenheit (F) and 500 pounds per square inch (psi) for 16 hours. The resulting reverse emulsion OBM had a plastic viscosity of 24.2cP, a yield point of 11.2 ℃ F., an American Petroleum Institute (API) fluid loss of 0ml, an API fluid loss of 0ml, an HPHT fluid loss of 0ml (at 300 ℃ F. and 500 psi), and an HPHT fluid loss of 3.4ml (at 300 ℃ F. and 500 psi).

In another example, samples of reverse emulsified OBM were prepared as described in the previous paragraph except that the concentration of emulsifier was changed to 6ml, 4ml and 0 ml. For such samples, the plastic viscosities were 35cP, 34cP, and 30cP, respectively. The yield points were 12 ° F, 17 ° F, and 30 ° F, respectively. The initial filter loss of API was 0ml, 0ml and 0.2ml, respectively. The API fluid loss was 1ml, 2ml and 9.3ml, respectively. The HPHT initial fluid losses were 2ml, 6ml and 8ml (at 300 ℃ F. and 500 psi.). HPHT fluid losses were 7ml, 18ml and 68ml (at 300 ℃ F. and 500 psi). In summary, reverse emulsion OBM shows very good rheological properties and suitability as oil based drilling fluids for concentrations in the range of 4 to 12ml of emulsifier per 218ml of Safra oil.

Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims.