High temperature resistant diesel-based drilling fluid and preparation method thereof

Abstract

This invention provides a high-temperature resistant diesel-based drilling fluid and its preparation method. The high-temperature resistant diesel-based drilling fluid comprises the following components in parts by weight: 80-90 parts diesel oil, 1-2 parts primary emulsifier, 0.5-1 part secondary emulsifier, 10-20 parts brine solution, 1-3 parts organic clay, 2-4 parts calcium oxide, and 2-4 parts high-temperature filtration reduction agent. The diesel-based drilling fluid of this invention exhibits good emulsification stability and temperature resistance, meeting the safety requirements for downhole drilling with high-temperature deep well oil-based drilling fluids.

Description

Technical Field

[0001] This invention belongs to the technical field of oil-based drilling fluids for petroleum drilling, specifically relating to a high-temperature resistant diesel-based drilling fluid and its preparation method. Background Technology

[0002] In unconventional and ultra-deep drilling, shale gas and coal gas areas face challenges such as long horizontal sections of fractured and easily collapsed formations, frequent blockages, and ultra-deep areas with abnormally high temperatures and pressures, frequent fracture losses, and contamination by gypsum and brine. Oil-based drilling fluids, due to their excellent high-temperature stability, lubricity, and inhibitory properties, have become the preferred choice for unconventional and ultra-deep drilling. Currently, oil-based drilling fluids are primarily based on diesel fuel. Diesel fuel has a wide carbon chain distribution and complex composition. Existing emulsifiers and organic clay treatment agents have poor applicability in diesel-based drilling fluids, requiring large dosages but yielding low efficiency, making it difficult to meet the technical requirements of complex high-temperature deep well conditions. Therefore, there is an urgent need to develop a diesel-based, high-temperature resistant oil-based drilling fluid specifically designed for diesel fuel, ensuring stable performance under extreme conditions such as high temperature, high pressure, and prolonged static conditions. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a high-temperature resistant diesel-based drilling fluid and its preparation method. The drilling fluid of the present invention achieves emulsification stability and high-temperature resistance of the diesel-based drilling fluid with a low addition amount of treatment agent, thereby improving the high-temperature rheological properties of the diesel-based drilling fluid.

[0004] To achieve this objective, the present invention adopts the following technical solution:

[0005] On one hand, the present invention provides a high-temperature resistant diesel-based drilling fluid, which comprises the following components in parts by weight: 80-90 parts diesel oil, 1-2 parts primary emulsifier, 0.5-1 part secondary emulsifier, 10-20 parts brine solution, 1-3 parts organic clay, 2-4 parts calcium oxide, and 2-4 parts high-temperature filtration reduction agent.

[0006] The primary emulsifier includes organic acids, polyethylene polyamines, and diluents, wherein the organic acids are a combination of coconut oil acid, tall oil fatty acids, and rosin acid.

[0007] In this invention, specific organic acids are selected for combination, allowing organic acids with different carbon chain distributions to be used in combination. After being reacted with polyethylene polyamines via amidation, an etherification reaction is carried out to improve the emulsification stability and temperature stability of diesel-based drilling fluids.

[0008] In this invention, the diesel content in the high-temperature resistant diesel-based drilling fluid can be 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, or 90 parts; the content of the primary emulsifier can be 1 part, 1.3 parts, 1.5 parts, 1.8 parts, or 2 parts; the content of the secondary emulsifier can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, or 1 part; the content of the brine can be 10 parts, 12 parts, 15 parts, 18 parts, or 20 parts; the content of the organic soil can be 1 part, 1.5 parts, 1.8 parts, 2 parts, 2.5 parts, 2.8 parts, or 3 parts; the content of the calcium oxide can be 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts; and the content of the high-temperature resistant filtration reduction agent can be 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts.

[0009] Preferably, the molar ratio of coconut oil acid to tall oil fatty acid is 1:2 to 1:4, for example, 1:2, 1:2.5, 1:2.8, 1:3, 1:3.5, 1:3.8 or 1:4.

[0010] Preferably, the molar ratio of rosin acid and tall oil fatty acid is 1:2 to 1:4, for example, 1:2, 1:2.5, 1:2.8, 1:3, 1:3.5, 1:3.8 or 1:4.

[0011] Preferably, the polyethylene polyamine is selected from one or a combination of at least two of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0012] Preferably, the polyethylene polyamine is a combination of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0013] Preferably, in the combination of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, the molar ratio of diethylenetriamine to triethylenetetramine is 3:1 to 5:1 (e.g., 3:1, 3.5:1, 3.8:1, 4:1, 4.5:1, 4.8:1, or 5:1); and the ratio of triethylenetetramine to tetraethylenepentamine is 1:1 to 2:1 (e.g., 1:1, 1.3:1, 1.5:1, 1.8:1, or 2:1).

[0014] Preferably, the diluent is selected from one or a mixture of two of white oil or ethylene glycol monobutyl ether.

[0015] Preferably, the molar ratio of organic acid to polyethylene polyamine in the main emulsifier is 2:1 to 3:1, for example, 2:1, 2.3:1, 2.5:1, 2.8:1 or 3:1.

[0016] Preferably, the amount of diluent in the primary emulsifier is 10-30% of the mass of tall oil fatty acids, for example, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28% or 30%.

[0017] Preferably, the primary emulsifier can be prepared according to the following method:

[0018] (1) Coconut oil acid, tall oil fatty acid and rosin acid are mixed, heated, and then polyethylene polyamine is added to carry out an amidation reaction;

[0019] (2) After the amidation reaction is completed, the temperature is raised to carry out an intramolecular dehydration reaction, then a diluent is added and the temperature is lowered to obtain the main emulsifier.

[0020] Preferably, the temperature rise in step (1) is to rise to 150-170°C (e.g., 150°C, 155°C, 160°C, 165°C or 170°C).

[0021] Preferably, the heating in step (1) is carried out under stirring, and the stirring speed is 100-500 r / min.

[0022] Preferably, the amidation reaction in step (1) takes 2-3 hours, for example 2 hours, 2.5 hours, 2.8 hours or 3 hours.

[0023] In the amidation reaction described in this invention, the water generated is removed by vacuuming.

[0024] Preferably, the temperature rise in step (2) is to 230-240°C (e.g., 230°C, 235°C, 238°C or 240°C).

[0025] Preferably, the intramolecular dehydration reaction in step (2) takes 4-6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0026] In this invention, the water generated during the intramolecular dehydration reaction is removed by vacuuming.

[0027] Preferably, the cooling in step (2) is to cool to room temperature.

[0028] Preferably, the co-emulsifier is selected from fatty acid alkanolamides.

[0029] Preferably, the salt solution is any one or a combination of at least two of the following: calcium chloride, potassium chloride, potassium formate, or sodium formate.

[0030] Preferably, the mass percentage concentration of the saline solution is 10% to 30%, for example, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, or 30%.

[0031] Preferably, the organic soil includes montmorillonite modified with cationic surfactants and sepiolite modified with silane coupling agents.

[0032] Preferably, the cationic surfactant is bis(octadecyldimethylammonium chloride) and / or octadecyldimethylbenzylammonium chloride.

[0033] Preferably, the cationic surfactant is a combination of bis(octadecyldimethylammonium chloride) and octadecyldimethylbenzylammonium chloride, with a molar ratio of 1:2 to 2:1, such as 1:2, 1:1.5, 1:1.8, 1:1, 1.3:1, 1.5:1, 1.8:1 or 2:1.

[0034] Preferably, the silane coupling agent is one or a combination of at least two of phenyltrimethoxysilane, phenyltriethoxysilane, methylphenyldimethoxysilane, and methylphenyldiethoxysilane.

[0035] Preferably, the montmorillonite is sodium-based montmorillonite.

[0036] Preferably, the mass ratio of the cationic surfactant-modified montmorillonite to the silane coupling agent-modified sepiolite is 1:2 to 2:1, for example, 1:2, 1:1.8, 1:1.5, 1:1.3, 1:1, 1.3:1, 1.5:1, 1.8:1 or 2:1, and more preferably 1:1.

[0037] Preferably, the cationic surfactant-modified montmorillonite is prepared by the following method:

[0038] A cationic surfactant is added to a montmorillonite suspension, the pH is adjusted to 7-8 (e.g., 7, 7.4, 7.8 or 8), and the mixture is reacted at 70-80°C (e.g., 70°C, 73°C, 75°C, 78°C or 80°C) for 3-5 hours (e.g., 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours) to obtain the cationic surfactant-modified montmorillonite.

[0039] Preferably, the solvent in the montmorillonite suspension is water, preferably distilled water.

[0040] In this invention, after the reaction to prepare cationic surfactant-modified montmorillonite is completed, the solution is taken out, allowed to stand, separated, dried, and passed through a 200-mesh sieve to obtain modified montmorillonite.

[0041] Preferably, the silane coupling agent modified sepiolite is prepared by the following method:

[0042] A. Sepiolite is treated with an acid solution to obtain acid-treated sepiolite;

[0043] B. The silane coupling agent is hydrolyzed in a solvent to obtain a hydrolyzed solution;

[0044] C. Add the acid-treated sepiolite obtained in step A to the hydrolysis solution obtained in step B, adjust the pH of the solution to above 9, and react to obtain the silane coupling agent modified sepiolite.

[0045] Preferably, the acid solution in step A is a 1 mol / L dilute hydrochloric acid solution.

[0046] Preferably, the acid treatment in step A involves dispersing sepiolite in an acid solution and stirring for 10-40 minutes, then filtering, washing with anhydrous ethanol and deionized water until neutral, and drying and pulverizing to obtain acid-treated sepiolite.

[0047] Preferably, the solvent in step B is a mixed solution of ethanol and water, and preferably, the volume ratio of ethanol to water is 9:1.

[0048] Preferably, the hydrolysis reaction in step B is carried out at a temperature of 70-90°C (e.g., 70°C, 75°C, 80°C, 85°C or 90°C) and the hydrolysis reaction time is 0.5-1h (e.g., 0.5h, 0.8h or 1h).

[0049] Preferably, the pH value in step C is 9 to 12 (e.g., 9, 9.5, 10, 10.5, 11, 11.5 or 12), and more preferably 10.

[0050] Preferably, the reaction temperature in step C is 70-90°C (e.g., 70°C, 75°C, 80°C, 85°C or 90°C), and the reaction time is 5-7h (5h, 5.5h, 6h, 6.5h or 7h).

[0051] After the reaction in step C of this invention is completed, the mixture is washed with anhydrous ethanol and deionized water until neutral, and then dried and pulverized at 105°C to obtain modified sepiolite.

[0052] This invention improves the dispersion ability and temperature resistance of organic soil in diesel fuel by modifying montmorillonite with surfactants and modifying sepiolite with silane coupling agents, thereby improving the high-temperature rheological properties of diesel-based drilling fluids.

[0053] Preferably, the high-temperature filtration loss reducing agent is selected from any one or a combination of at least two of oxidized asphalt, natural asphalt, or modified lignite.

[0054] Preferably, the high-temperature resistant diesel-based drilling fluid also includes a weighting agent.

[0055] Preferably, the weighting agent is barite.

[0056] Preferably, the amount of weighting agent added to the high-temperature resistant diesel-based drilling fluid is 0.5-4.5 times the total volume of diesel and brine solution, for example, 0.5 times, 1 time, 1.5 times, 1.8 times, 2 times, 2.5 times, 2.8 times, 3 times, 3.5 times, 3.8 times or 4 times.

[0057] In this invention, the high-temperature resistant diesel-based drilling fluid is prepared by thoroughly mixing the components.

[0058] On the other hand, the present invention provides the application of the high-temperature resistant diesel-based drilling fluid described above in the exploration and development of deep oil and gas resources.

[0059] In this invention, the high temperature resistance refers to the ability to withstand temperatures above 220°C.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] The high-temperature resistant diesel-based drilling fluid of the present invention uses specific organic acids in combination, so that organic acids with different carbon chain distributions are used in combination. After being reacted with polyethylene polyamines via amidation, an etherification reaction is carried out to improve the emulsification stability and temperature resistance of the diesel-based drilling fluid.

[0062] The present invention reduces the amount of emulsifier and organic soil used in the high-temperature diesel-based drilling fluid. With a low amount of emulsifier and organic soil, the diesel-based drilling fluid achieves high-temperature long-term stability, with a temperature resistance of over 220°C and a demulsification voltage of over 500V. This reduces the overall cost of the drilling fluid and the maintenance requirements during construction, while meeting the safety requirements for downhole construction of high-temperature deep well oil-based drilling fluid. Detailed Implementation

[0063] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0064] In the following embodiments, unless otherwise stated, all raw materials used are conventional materials and are commercially available. The methods used in the embodiments, unless otherwise specified, are existing technologies.

[0065] In the materials used in the examples, #0 diesel oil was purchased from the Ziyang Oil Depot of Sichuan Petroleum Administration Bureau.

[0066] Deionized water, anhydrous ethanol, ammonia, hydrochloric acid, calcium oxide, and calcium chloride were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and were of analytical grade.

[0067] The sepiolite was purchased from Dingxing County Antai Hengxin New Thermal Insulation Materials Co., Ltd.

[0068] Phenylacetyltrimethoxysilane, phenyltriethoxysilane, methylphenyldimethoxysilane, and methylphenyldiethoxysilane were purchased from Guangzhou Zhongjie Chemical Technology Co., Ltd., with a purity of ≥98%.

[0069] The co-emulsifier and the filtration loss reducer were both produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0070] The barite was purchased from Ankang Liyuan Mining Co., Ltd.

[0071] Example 1

[0072] 1. Preparation of the main emulsifier

[0073] (1) Coconut oil acid, tall oil fatty acid and rosin acid are loaded into a three-necked flask in a molar ratio of 1:2:1 and heated to 165°C under mechanical stirring at 300 r / min.

[0074] (2) Diethylenetriamine, triethylenetetramine and tetraethylenepentamine are added in a molar ratio of 3:1:1, and the total amount is in a molar ratio of 2:1 to the total amount of acid in step (1). The amidation reaction is carried out for 3 hours, during which the generated water is removed by vacuuming.

[0075] (3) After the amidation reaction is completed, the temperature is raised to 240°C to carry out intramolecular dehydration reaction for 6 hours. During this period, the generated water is removed by vacuuming.

[0076] (4) Add 1 / 5 of the total reactant mass of white oil as a diluent and cool to room temperature to obtain the main emulsifier.

[0077] 2. Preparation of organic soil

[0078] (1) At a rotation speed of 150 r / min, 1.3 CEC (cation exchange capacity) of dioctadecyl dimethyl ammonium chloride and octadecyl dimethyl benzyl ammonium chloride were mixed in a molar ratio of 1:1 and added to a 4% sodium montmorillonite suspension. The pH was adjusted to 7 and the mixture was reacted at 75 °C for 3 h.

[0079] (2) After the reaction is complete, the solution is taken out, allowed to stand, separated, dried, and passed through a 200-mesh sieve to obtain modified montmorillonite.

[0080] (3) Disperse the sepiolite in a three-necked flask containing 1 mol / L dilute hydrochloric acid solution, turn on the stirrer and stir for 30 min. After stirring, pour it into a vacuum filtration flask, wash it with anhydrous ethanol and deionized water in sequence until neutral, dry and crush it to obtain acid-treated sepiolite.

[0081] (4) In a three-necked flask, disperse phenyltriethoxysilane in a 90:10 ethanol / water mixture, adjust the water bath temperature to 80°C, and turn on the stirrer to stir and hydrolyze until no layering is observed.

[0082] (5) Add the acid-treated sepiolite obtained in the previous step to the mixed solution after hydrolysis of silane coupling agent. The mass ratio of sepiolite to silane coupling agent is 2:1. Then add a certain amount of ammonia water to the solution to adjust the pH value to 10. React for 5 hours under mechanical stirring at 150 r / min.

[0083] (6) After the reaction was completed, the mixture was washed with anhydrous ethanol and deionized water until neutral, and then dried and pulverized at 105°C to obtain modified sepiolite.

[0084] (7) Modified montmorillonite and modified sepiolite are mixed in a 1:1 ratio to obtain organic soil.

[0085] 3. Preparation of high-temperature resistant diesel-based drilling fluid

[0086] Maintaining a stirring speed of 11,000 rpm, add 8g of primary emulsifier and 4g of secondary emulsifier to 320mL of diesel oil and stir at high speed for 10 minutes; add 12g of organic clay and stir at high speed for 10 minutes; add 80mL of CaCl2 aqueous solution (mass concentration of 20%) and stir at high speed for 20 minutes; add 16g of calcium oxide and stir at high speed for 10 minutes; add 16g of filtration reducer and stir at high speed for 10 minutes; finally, add 595g of barite and stir for 30 minutes to obtain a high-temperature resistant diesel-based drilling fluid with an oil-water ratio of 80:20 and a density of 1.8g / cm³. 3 .

[0087] Example 2

[0088] 1. Preparation of the main emulsifier

[0089] Same as Example 1

[0090] 2. Preparation of organic soil

[0091] (1) At a rotation speed of 150 r / min, 1.3 CEC of dioctadecyl dimethyl ammonium chloride and octadecyl dimethyl benzyl ammonium chloride were mixed in a molar ratio of 1:1 and added to a 4% sodium montmorillonite suspension. The pH was adjusted to 7 and the mixture was reacted at 75 °C for 3 h.

[0092] (2) After the reaction is complete, the solution is taken out, allowed to stand, separated, dried, and passed through a 200-mesh sieve to obtain modified montmorillonite.

[0093] (3) Disperse the sepiolite in a three-necked flask containing 1 mol / L dilute hydrochloric acid solution, turn on the stirrer and stir for 30 min. After stirring, pour it into a vacuum filtration flask, wash it with anhydrous ethanol and deionized water in sequence until neutral, dry and crush it to obtain acid-treated sepiolite.

[0094] (4) In a three-necked flask, disperse phenyltriethoxysilane in a 90:10 ethanol / water mixture, adjust the water bath temperature to 80°C, and turn on the stirrer to stir and hydrolyze until no layering is observed.

[0095] (5) Add the acid-treated sepiolite obtained in the previous step to the mixed solution after hydrolysis of silane coupling agent. The mass ratio of sepiolite to silane coupling agent is 2:1. Then add a certain amount of ammonia water to the solution to adjust the pH value to 10. React for 5 hours under mechanical stirring at 150 r / min.

[0096] (6) After the reaction was completed, the mixture was washed with anhydrous ethanol and deionized water until neutral, and then dried and pulverized at 105°C to obtain modified sepiolite.

[0097] (7) Modified montmorillonite and modified sepiolite are mixed in a 2:1 ratio to obtain organic soil.

[0098] 3. Preparation of high-temperature resistant diesel-based drilling fluid

[0099] Maintaining a stirring speed of 11,000 rpm, add 8g of primary emulsifier and 4g of secondary emulsifier to 320mL of diesel oil and stir at high speed for 10min; add 12g of organic clay and stir at high speed for 10min; add 80mL of CaCl2 aqueous solution (mass concentration of 20%) and stir at high speed for 20min; add 16g of calcium oxide and stir at high speed for 10min; add 16g of filtration reducer and stir at high speed for 10min; finally, add 342g of barite and stir for 30min to obtain a high-temperature resistant diesel-based drilling fluid with an oil-water ratio of 80:20 and a density of 1.5g / cm³. 3 .

[0100] Example 3

[0101] 1. Preparation of the main emulsifier

[0102] Same as Example 1

[0103] 2. Preparation of organic soil

[0104] (1) At a rotation speed of 150 r / min, 1.3 CEC of dioctadecyl dimethyl ammonium chloride and octadecyl dimethyl benzyl ammonium chloride were mixed in a molar ratio of 1:1 and added to a 4% sodium montmorillonite suspension. The pH was adjusted to 7 and the mixture was reacted at 75 °C for 3 h.

[0105] (2) After the reaction is complete, the solution is taken out, allowed to stand, separated, dried, and passed through a 200-mesh sieve to obtain modified montmorillonite.

[0106] (3) Disperse the sepiolite in a three-necked flask containing 1 mol / L dilute hydrochloric acid solution, turn on the stirrer and stir for 30 min. After stirring, pour it into a vacuum filtration flask, wash it with anhydrous ethanol and deionized water in sequence until neutral, dry and crush it to obtain acid-treated sepiolite.

[0107] (4) In a three-necked flask, disperse phenyltriethoxysilane in a 90:10 ethanol / water mixture, adjust the water bath temperature to 80°C, and turn on the stirrer to stir and hydrolyze until no layering is observed.

[0108] (5) Add the acid-treated sepiolite obtained in the previous step to the mixed solution after hydrolysis of silane coupling agent. The mass ratio of sepiolite to silane coupling agent is 2:1. Then add a certain amount of ammonia water to the solution to adjust the pH value to 10. React for 5 hours under mechanical stirring at 150 r / min.

[0109] (6) After the reaction was completed, the mixture was washed with anhydrous ethanol and deionized water until neutral, and then dried and pulverized at 105°C to obtain modified sepiolite.

[0110] (7) Modified montmorillonite and modified sepiolite are mixed at a ratio of 1:2 to obtain organic soil.

[0111] 3. Preparation of high-temperature resistant diesel-based drilling fluid

[0112] Maintaining a stirring speed of 11,000 rpm, add 8 g of primary emulsifier and 4 g of secondary emulsifier to 360 mL of diesel oil, and stir at high speed for 10 min; add 12 g of organic clay, and stir at high speed for 10 min; add 40 mL of CaCl2 aqueous solution (mass concentration of 20%), and stir at high speed for 20 min; add 16 g of calcium oxide, and stir at high speed for 10 min; add 16 g of filtration loss reducer, and stir at high speed for 10 min; finally, add 1194 g of barite, and stir for 30 min to obtain a high-temperature resistant diesel-based drilling fluid with an oil-water ratio of 90:10 and a density of 2.3 g / cm³. 3 .

[0113] Example 4

[0114] 1. Preparation of the main emulsifier

[0115] (1) Coconut oil acid, tall oil fatty acid and rosin acid are loaded into a three-necked flask in a molar ratio of 1:2:1 and heated to 165°C under mechanical stirring at 300 r / min.

[0116] (2) Add diethylenetriamine and triethylenetetramine at a molar ratio of 3:1. The total amount of diethylenetriamine and triethylenetetramine is in a molar ratio of 2:1 to the total amount of acid in step (1). The amidation reaction is carried out for 3 hours. During this period, the generated water is removed by vacuuming.

[0117] (3) After the amidation reaction is completed, the temperature is raised to 240°C to carry out intramolecular dehydration reaction for 6 hours. During this period, the generated water is removed by vacuuming.

[0118] (4) Add 1 / 5 of the total reactant mass of ethylene glycol monobutyl ether as a diluent, and cool to room temperature to obtain the main emulsifier.

[0119] 2. Preparation of organic soil

[0120] Same as Example 1.

[0121] 3. Preparation of high-temperature resistant diesel-based drilling fluid

[0122] Same as Example 1.

[0123] Comparative Example 1

[0124] 1. Preparation of the main emulsifier

[0125] The main emulsifier used is a commercially available emulsifier (TYODF-301, Korla Tongyi Industry and Trade Co., Ltd.), which is a fatty acid amide derivative.

[0126] 2. Preparation of organic soil

[0127] Same as Example 1.

[0128] 3. Preparation of high-temperature resistant diesel-based drilling fluid

[0129] Same as Example 1.

[0130] Comparative Example 2

[0131] 1. Preparation of the main emulsifier

[0132] Same as Comparative Example 1.

[0133] 2. Preparation of organic soil

[0134] The organic soil used is commercially available organic soil (Korla Tongyi Industry and Trade Co., Ltd., TYODF-601), which is modified montmorillonite.

[0135] 3. Preparation of high-temperature resistant diesel-based drilling fluid

[0136] Same as Example 1.

[0137] Comparative Example 3

[0138] The difference from Example 1 is that the organic acids used in the preparation of the main emulsifier are coconut oil acid and tall oil fatty acid, with a molar ratio of 1:2, and the total molar amount of the two is equal to the total molar amount of coconut oil acid, tall oil fatty acid and rosin acid in Example 1. Everything else is the same as in Example 1.

[0139] Comparative Example 4

[0140] The difference from Example 1 is that the organic acids used in the preparation of the main emulsifier are soybean oleic acid, tall oil fatty acid, and rosin acid, in a molar ratio of 1:2:1. All other aspects are the same as in Example 1.

[0141] Comparative Example 5

[0142] The difference from Example 1 is that the organic acids used in the preparation of the primary emulsifier are coconut oil acid, tall oil fatty acid, and palmitic acid, in a molar ratio of 1:2:1. All other aspects are the same as in Example 1.

[0143] Table 1. Performance of Oil-Based Drilling Fluids in Examples

[0144]

[0145]

[0146] Table 2 Comparative Performance of Oil-Based Drilling Fluids

[0147]

[0148] Based on the experimental results in Table 1, the four high-temperature resistant diesel-based drilling fluids prepared in the examples had an emulsifier content of 3%, an organic clay content of 2%, and a density of 1.5–2.3 g / cm³. 3 With oil-water ratios ranging from 80:20 to 90:10, the drilling fluids maintained good performance before and after aging at 220℃, exhibiting a demulsification voltage ≥800V and a high-temperature, high-pressure filtration loss of less than 5mL. The oil-based drilling fluids prepared in Examples 1, 2, and 3, with adjustments to the ratio of modified montmorillonite and modified sepiolite based on density, demonstrated even better high-temperature rheological stability. In Example 4, the type of polyethylenepolyamine in the emulsifier was changed, resulting in minimal impact on the drilling fluid performance.

[0149] Based on the experimental results in Table 2, the diesel-based drilling fluids prepared in Comparative Examples 1 and 2 were compared with those in Example 1. In Comparative Example 1, a commercially available emulsifier was used, resulting in significant changes in the drilling fluid's demulsification voltage, rheology, and filtration loss. In particular, the demulsification voltage after aging was below 400V, failing to meet practical field application requirements, indicating that the main emulsifier in this invention plays a crucial role in stabilizing the system. In Comparative Example 2, a commercially available organic clay was used, resulting in significant changes in high-temperature rheology, indicating that the organic clay of this invention plays a key role. In Comparative Examples 3-5, changing the type of organic acid led to varying degrees of deterioration in the drilling fluid's filtration loss and rheology, demonstrating the specificity of organic acid selection.

[0150] The applicant declares that this invention illustrates the high-temperature resistant diesel-based drilling fluid and its application through the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials of the product, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A high-temperature resistant diesel-based drilling fluid, characterized in that, The high-temperature resistant diesel-based drilling fluid comprises the following components in parts by weight: 80-90 parts diesel oil, 1-2 parts primary emulsifier, 0.5-1 part secondary emulsifier, 10-20 parts brine solution, 1-3 parts organic clay, 2-4 parts calcium oxide, and 2-4 parts high-temperature filtration reduction agent. The primary emulsifier includes organic acids, polyethylene polyamines, and diluents, wherein the organic acids are a combination of coconut oil acid, tall oil fatty acids, and rosin acid.

2. The high-temperature resistant diesel-based drilling fluid according to claim 1, characterized in that, The molar ratio of coconut oil acid to tall oil fatty acid is 1:2 to 1:4; Preferably, the molar ratio of rosin acid to tall oil fatty acid is 1:2 to 1:4; Preferably, the polyethylene polyamine is selected from one or a combination of at least two of diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine; Preferably, the polyethylene polyamine is a combination of diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine; Preferably, in the combination of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, the molar ratio of diethylenetriamine to triethylenetetramine is 3:1 to 5:1; and the ratio of triethylenetetramine to tetraethylenepentamine is 1:1 to 2:

1.

3. The high-temperature resistant diesel-based drilling fluid according to claim 1 or 2, characterized in that, The diluent is selected from one or a mixture of two of white oil or ethylene glycol monobutyl ether; Preferably, the molar ratio of organic acid to polyethylene polyamine in the main emulsifier is 2:1 to 3:1; Preferably, the amount of diluent used in the primary emulsifier is 10-30% of the mass of tall oil fatty acids.

4. The high-temperature resistant diesel-based drilling fluid according to any one of claims 1-3, characterized in that, The main emulsifier is prepared by the following method: (1) Coconut oil acid, tall oil fatty acid and rosin acid are mixed, heated, and then polyethylene polyamine is added to carry out an amidation reaction; (2) After the amidation reaction is completed, the temperature is raised to carry out an intramolecular dehydration reaction, then a diluent is added and the temperature is lowered to obtain the main emulsifier.

5. The high-temperature resistant diesel-based drilling fluid according to claim 4, characterized in that, The heating in step (1) is to raise the temperature to 150-170℃; Preferably, the heating in step (1) is carried out under stirring, and the stirring speed is 100-500 r / min; Preferably, the amidation reaction in step (1) takes 2-3 hours; Preferably, the temperature rise in step (2) is to 230-240°C; Preferably, the intramolecular dehydration reaction in step (2) takes 4-6 hours; Preferably, the cooling in step (2) is to cool to room temperature.

6. The high-temperature resistant diesel-based drilling fluid according to any one of claims 1-5, characterized in that, The co-emulsifier is selected from fatty acid alkanolamides; Preferably, the salt solution is any one or a combination of at least two of the following: calcium chloride, potassium chloride, potassium formate, or sodium formate. Preferably, the mass percentage concentration of the salt solution is 10-30%.

7. The high-temperature resistant diesel-based drilling fluid according to any one of claims 1-6, characterized in that, The organic soil includes montmorillonite modified with cationic surfactants and sepiolite modified with silane coupling agents; Preferably, the cationic surfactant is dioctadecyldimethylammonium chloride and / or octadecyldimethylbenzylammonium chloride; Preferably, the cationic surfactant is a combination of bis(octadecyldimethylammonium chloride) and octadecyldimethylbenzylammonium chloride, with a molar ratio of 1:2 to 2:

1. Preferably, the silane coupling agent is one or a combination of at least two of phenyltrimethoxysilane, phenyltriethoxysilane, methylphenyldimethoxysilane, and methylphenyldiethoxysilane; Preferably, the montmorillonite is sodium-based montmorillonite; Preferably, the mass ratio of the cationic surfactant-modified montmorillonite to the silane coupling agent-modified sepiolite is 1:2 to 2:1, and more preferably 1:

1.

8. The high-temperature resistant diesel-based drilling fluid according to any one of claims 1-7, characterized in that, The cationic surfactant-modified montmorillonite was prepared by the following method: A cationic surfactant was added to the montmorillonite suspension, the pH was adjusted to 7-8, and the mixture was reacted at 70-80℃ for 3-5 hours to obtain the cationic surfactant-modified montmorillonite. Preferably, the solvent in the montmorillonite suspension is water, preferably distilled water.

9. The high-temperature resistant diesel-based drilling fluid according to any one of claims 1-8, characterized in that, The silane coupling agent modified sepiolite was prepared by the following method: A. Sepiolite is treated with an acid solution to obtain acid-treated sepiolite; B. The silane coupling agent is hydrolyzed in a solvent to obtain a hydrolyzed solution; C. Add the acid-treated sepiolite obtained in step A to the hydrolysis solution obtained in step B, adjust the pH of the solution to above 9, and react to obtain the silane coupling agent modified sepiolite. Preferably, the acid solution in step A is a 1 mol / L dilute hydrochloric acid solution; Preferably, the acid treatment in step A involves dispersing sepiolite in an acid solution and stirring for 10-40 minutes, then filtering, washing with anhydrous ethanol and deionized water until neutral, and drying and pulverizing to obtain acid-treated sepiolite. Preferably, the solvent in step B is a mixed solution of ethanol and water, and preferably, the volume ratio of ethanol to water is 9:

1. Preferably, the hydrolysis reaction in step B is carried out at a temperature of 70-90°C for 0.5-1 hour. Preferably, the pH value in step C is 9 to 12, more preferably 10; Preferably, the reaction temperature in step C is 70-90℃, and the reaction time is 5-7 hours. Preferably, the high-temperature filtration loss reducing agent is selected from any one or a combination of at least two of oxidized asphalt, natural asphalt, or modified lignite; Preferably, the high-temperature resistant diesel-based drilling fluid also includes a weighting agent; Preferably, the weighting agent is barite; Preferably, the amount of weighting agent added to the high-temperature resistant diesel-based drilling fluid is 0.5-4.5 times the total volume of diesel and brine solution, expressed in grams.

10. The application of the high-temperature resistant diesel-based drilling fluid according to any one of claims 1-9 in the exploration and development of deep oil and gas resources.

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