Compound emulsifier for oil-based drilling fluid and preparation method thereof

Abstract

The application provides a composite emulsifier for oil-based drilling fluid and a preparation method thereof, and the composite emulsifier comprises the following components in mass fractions: 30-40 parts of a main emulsifier, 10-20 parts of auxiliary emulsifier A: sulfonate, 8-18 parts of auxiliary emulsifier B: oleic acid, 12-17 parts of a wetting agent, 3-8 parts of modified cyclodextrin and 5-10 parts of a cut point agent; wherein the preparation method of the main emulsifier is as follows: (1) 1 mole fraction of ricinoleic acid and 1.1 mole fraction of diethylenetriamine are mixed and reacted at a constant temperature of 165-170 DEG C until no by-product water is generated, to obtain product A; (2) 1.1 mole fraction of acrylonitrile is slowly added into the product A, and reacted at 40-45 DEG C for 2-3 h, and then distilled under reduced pressure, to obtain the main emulsifier. The composite emulsifier has high emulsifying performance, good stability at high temperature, and good rheological property of the prepared drilling fluid under high density.

Description

Technical Field

[0001] This invention belongs to the field of drilling fluid technology, specifically relating to composite emulsifiers for oil-based drilling fluids and their preparation methods. Background Technology

[0002] With the continuous deepening and development of research in China's oil and gas sector, the exploration and development of oil and gas resources in my country is gradually moving towards complex oil and gas formations such as deep formations, deep water, and unconventional areas. Complex oil and gas has become an important alternative energy source for China and even globally. However, the safety and efficiency under ultra-deep well and ultra-deep water conditions still need further improvement. Compared with water-based drilling fluids, oil-based drilling fluids have stronger anti-fouling capabilities, better lubrication, and stronger inhibition properties, which are conducive to maintaining wellbore stability and can maximize the protection of oil and gas reservoirs. At the same time, oil-based drilling fluids have stable performance, are easy to maintain, have strong temperature resistance, and good thermal stability. The excellent inhibition and temperature resistance of oil-based drilling fluids make them more advantageous in drilling complex wells, especially in high-temperature deep wells and water-sensitive formations, enabling them to more effectively protect water-sensitive oil and gas reservoirs and increase oil and gas production in the drilling fluid field.

[0003] Oil-based drilling fluids have become crucial materials for drilling high-temperature deep wells, highly deviated directional wells, horizontal wells, various complex wells, and reservoir protection. As a key component of oil-based drilling fluid systems, emulsifiers play a vital role. However, the development of oil-based drilling fluids has been relatively slow due to cost and environmental constraints, and their application in fewer blocks is limited. With the declining reserves in existing oilfields and the increasing complexity of formations and environments encountered in new exploration areas, research is urgently needed to develop emulsifiers suitable for preparing stable and efficient oil-based drilling fluids, providing technical support for their widespread application. The stability of oil-based drilling fluids largely depends on the rational use of emulsifiers. In recent years, with the continuous deepening of oil and gas resource exploration and development both domestically and internationally, the number of deep and ultra-deep wells has gradually increased, and the upper limit of bottom hole temperature has been constantly refreshed, making it extremely important to ensure the emulsion stability of oil-based drilling fluids. Currently, the main indicator of emulsion stability is the demulsification voltage. The demulsification voltage is typically measured at low temperatures using aged drilling fluids. However, the temperature resistance of emulsifiers currently used in oil-based drilling fluids cannot meet the requirements of existing usage conditions, and although the amount added is high, the effect is not good. Summary of the Invention

[0004] The purpose of this invention is to provide a composite emulsifier for oil-based drilling fluids and its preparation method. The composite emulsifier exhibits high emulsifying performance, good stability at high temperatures, and good rheological properties in the formulated drilling fluid under high density conditions. The raw materials used in this invention are inexpensive, readily available, safe, non-toxic, and easy to mass-produce.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a composite emulsifier for oil-based drilling fluids, wherein the composite emulsifier comprises the following components in parts by weight: 30-40 parts of primary emulsifier, 10-20 parts of co-emulsifier A: sulfonate, 8-18 parts of co-emulsifier B: oleic acid, 12-17 parts of wetting agent, 3-8 parts of modified cyclodextrin, and 5-10 parts of shearing agent;

[0006] The preparation method of the main emulsifier is as follows:

[0007] (1) Mix 1 molar amount of ricinoleic acid and 1.1 molar amount of diethylenetriamine and react at a constant temperature of 165-170℃ until no byproduct water is produced to obtain product A;

[0008]

[0009] (2) Continue to slowly add 1.1 molar amount of acrylonitrile to product A, react at 40-45℃ for 2-3 hours, and then distill under reduced pressure to obtain the main emulsifier;

[0010]

[0011] Furthermore, the co-emulsifier A is selected from one or more of sodium dodecylbenzene sulfonate, sodium petroleum sulfonate, and sodium dodecyl diphenyl ether disulfonate.

[0012] Furthermore, the co-emulsifier A is a compound of sodium dodecylbenzenesulfonate, sodium petroleum sulfonate and sodium dodecyl diphenyl ether disulfonate in a mass ratio of 1.4-1.8:0.8-1.2:0.3-0.7.

[0013] Furthermore, the mass ratio of the primary emulsifier, co-emulsifier A, and co-emulsifier B is 3.2-3.3:1.1-1.2:1.

[0014] Currently, in the oil and gas extraction field, to address the issue of poor environmental performance of oil-based drilling fluids caused by traditional mineral oils, some literature has proposed using non-toxic, biodegradable biodiesel as the base oil for environmentally friendly oil-based drilling fluids. Castor oil acid is a natural surfactant, but its temperature resistance is insufficient, and high-temperature aging reduces the performance of composite emulsifiers. This invention modifies the carboxyl groups on castor oil acid and combines it with two co-emulsifiers to obtain a composite emulsifier with good emulsifying properties and good temperature resistance. However, the electrical stability of the composite emulsifier is not ideal. Extensive experiments have shown that when the primary emulsifier, co-emulsifier A, and co-emulsifier B are compounded in a specific mass ratio, the demulsification voltage of the composite emulsifier can be improved. It is speculated that the composite emulsifier formed under these conditions can better regulate the surface tension at the liquid interface, forming a stable emulsion, and the charge distribution formed in the composite emulsifier simultaneously improves the demulsification voltage.

[0015] Furthermore, the wetting agent is dodecyltrimethylammonium bromide.

[0016] Further, the preparation method of the modified cyclodextrin is as follows: by mass, 10 parts of γ-cyclodextrin are dispersed in 100 parts of deionized water and stirred evenly to form a suspension. 0.5 parts of 2-octenyl succinic anhydride are added to 3 parts of anhydrous ethanol to prepare a mixture. The mixture is added dropwise to the suspension. At the same time, the pH of the reaction system is controlled at 8-9 with 4wt% NaOH aqueous solution. The reaction is continued until the pH of the system is constant. The pH of the reaction system is adjusted to 6 with 4wt% HCl aqueous solution. After washing, centrifugation, drying, and pulverizing through an 80-mesh sieve, the modified cyclodextrin is obtained.

[0017] This invention attempts to use γ-cyclodextrin to encapsulate the groups on the main emulsifier to improve the temperature resistance of the composite emulsifier. However, the inventors found that the encapsulation effect of γ-cyclodextrin in the system of this invention is not ideal due to the hydrophobic groups on its surface. The inventors improved the compatibility of γ-cyclodextrin with the system of this invention by modifying it, resulting in better temperature resistance of the composite emulsifier. Drilling fluid density can affect drilling fluid column pressure. Since there is a formation pressure in the formation through which drilling passes, the drilling fluid column pressure is used to balance this formation pressure. If the drilling fluid density is low, it cannot balance a certain formation pressure, and the wellbore may collapse. Fluids in the formation (oil, gas, water, etc.) may also enter the wellbore and flow to the surface. Mild cases result in well kicks, while severe cases lead to blowouts. Uncontrolled blowouts result in accidents. Therefore, high-density oil-based drilling fluids are of great importance. However, for a long time, ultra-high density (≥2.4 g / cm³) oil-based drilling fluids have been insufficient. 3 Oil-based drilling fluids, due to their extremely high solids content, high viscosity, and excessive flow resistance, cannot achieve the required drilling flow rate to clean the wellbore, making them unsuitable for the long-term drilling requirements of ultra-deep oil and gas wells and high-pressure shale gas wells. The inventors unexpectedly discovered that, under these conditions, oil-based drilling fluids formulated with composite emulsifiers can also exhibit good fluidity even at high densities.

[0018] Furthermore, the cutting agent is cutting agent D2833.

[0019] The present invention also provides a method for preparing a composite emulsifier for oil-based drilling fluid, comprising the following steps: mixing a primary emulsifier, a secondary emulsifier A and a secondary emulsifier B, heating to 43-45°C and stirring for 2-3 hours; continuing to add a temperature-resistant agent, heating to 55-57°C and stirring for 1.5-2.5 hours; cooling to 25-30°C, and then adding the remaining components and stirring for 2-3 hours.

[0020] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0021] 1. The purpose of this invention is to provide a composite emulsifier for oil-based drilling fluids and its preparation method. The oil-based drilling fluid exhibits high emulsification performance, good stability at high temperatures, and good rheological properties under high density conditions. The raw materials used in this invention are inexpensive, readily available, safe, and non-toxic.

[0022] 2. Ricinoleic acid is a natural surfactant, but its temperature resistance is insufficient, and the performance of the composite emulsifier will decrease after high-temperature aging. This invention modifies the carboxyl groups on ricinoleic acid and combines it with two co-emulsifiers to obtain a composite emulsifier with good emulsifying properties and good temperature resistance. When the main emulsifier, co-emulsifier A, and co-emulsifier B are compounded in a specific mass ratio, the demulsification voltage of the composite emulsifier can be improved.

[0023] 3. This invention attempts to use γ-cyclodextrin to encapsulate the groups on the main emulsifier to improve the temperature resistance of the composite emulsifier. However, the inventors found that the encapsulation effect of γ-cyclodextrin in the system of this invention is not ideal due to the hydrophobic groups on its surface. The inventors improved the compatibility of γ-cyclodextrin with the system of this invention by modifying it, resulting in better temperature resistance of the composite emulsifier. The composite emulsifier of this invention, when formulated into oil-based drilling fluid, can maintain good fluidity even at high densities. This solves the problem that ultra-high density oil-based drilling fluids, due to their extremely high solid content, high viscosity, and excessive flow resistance, cannot meet the drilling flow rate requirements for wellbore purification and are difficult to adapt to the long-term drilling requirements of ultra-deep oil and gas wells and high-pressure shale gas wells. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] This embodiment provides a composite emulsifier for oil-based drilling fluids. The composite emulsifier comprises the following components in parts by weight: 32 parts of primary emulsifier, 12 parts of co-emulsifier A (sulfonate), 10 parts of co-emulsifier B (oleic acid), 15 parts of wetting agent, 5 parts of modified cyclodextrin, and 8 parts of shearing agent.

[0027] The preparation method of the main emulsifier is as follows:

[0028] (1) Mix 1 molar amount of ricinoleic acid and 1.1 molar amount of diethylenetriamine and react at 167°C until no byproduct water is produced to obtain product A;

[0029]

[0030] (2) Continue to slowly add 1.1 molar amount of acrylonitrile to product A, react at 43℃ for 2.5h, and distill under reduced pressure to obtain the main emulsifier;

[0031]

[0032] The co-emulsifier A is a compound of sodium dodecylbenzenesulfonate, sodium petroleum sulfonate and sodium dodecyl diphenyl ether disulfonate in a mass ratio of 1.6:1.0:0.5.

[0033] The wetting agent is dodecyltrimethylammonium bromide.

[0034] The modified cyclodextrin is prepared as follows: 10 parts by mass of γ-cyclodextrin are dispersed in 100 parts of deionized water and stirred evenly to form a suspension. 0.5 parts of 2-octenyl succinic anhydride are added to 3 parts of anhydrous ethanol to prepare a mixture. The mixture is added dropwise to the suspension, while the pH of the reaction system is controlled at 8.5 using 4wt% NaOH aqueous solution. The reaction continues until the pH of the system is constant. The pH of the reaction system is adjusted to 6 using 4wt% HCl aqueous solution. After washing, centrifugation, drying, and pulverizing through an 80-mesh sieve, the modified cyclodextrin is obtained.

[0035] The cutting agent is cutting agent D2833, purchased from Jiujiang Lanzhuo New Material Technology Co., Ltd.

[0036] The present invention also provides a method for preparing a composite emulsifier for oil-based drilling fluid, comprising the following steps: mixing a primary emulsifier, a secondary emulsifier A and a secondary emulsifier B, heating to 44°C and stirring for 2.5 hours; continuing to add a temperature-resistant agent, heating to 56°C and stirring for 2 hours; cooling to 27°C, and then adding the remaining components and stirring for 2.5 hours.

[0037] Example 2

[0038] This embodiment provides a composite emulsifier for oil-based drilling fluids. The composite emulsifier comprises the following components in parts by weight: 33 parts of primary emulsifier, 12 parts of co-emulsifier A (sulfonate), 10 parts of co-emulsifier B (oleic acid), 17 parts of wetting agent, 8 parts of modified cyclodextrin, and 6 parts of shearing agent.

[0039] The preparation method of the main emulsifier is as follows:

[0040] (1) Mix 1 molar amount of ricinoleic acid and 1.1 molar amount of diethylenetriamine and react at 165°C until no byproduct water is produced to obtain product A;

[0041]

[0042] (2) Continue to slowly add 1.1 molar amount of acrylonitrile to product A, react at 40℃ for 3h, and then distill under reduced pressure to obtain the main emulsifier;

[0043]

[0044] The co-emulsifier A is a compound of sodium dodecylbenzenesulfonate, sodium petroleum sulfonate and sodium dodecyl diphenyl ether disulfonate in a mass ratio of 1.8:0.8:0.3.

[0045] The wetting agent is dodecyltrimethylammonium bromide.

[0046] The modified cyclodextrin is prepared as follows: 10 parts by mass of γ-cyclodextrin are dispersed in 100 parts of deionized water and stirred evenly to form a suspension. 0.5 parts of 2-octenyl succinic anhydride are added to 3 parts of anhydrous ethanol to prepare a mixture. The mixture is added dropwise to the suspension, while the pH of the reaction system is controlled at 9 using 4 wt% NaOH aqueous solution. The reaction continues until the pH of the system is constant. The pH of the reaction system is then adjusted to 6 using 4 wt% HCl aqueous solution. After washing, centrifugation, drying, and pulverizing through an 80-mesh sieve, the modified cyclodextrin is obtained.

[0047] The cutting agent is cutting agent D2833, purchased from Jiujiang Lanzhuo New Material Technology Co., Ltd.

[0048] The present invention also provides a method for preparing a composite emulsifier for oil-based drilling fluid, comprising the following steps: mixing a primary emulsifier, a secondary emulsifier A and a secondary emulsifier B, heating to 45°C and stirring for 2 hours; continuing to add a temperature-resistant agent, heating to 55°C and stirring for 2.5 hours; cooling to 25°C, and then adding the remaining components and stirring for 2 hours.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 is that it does not contain co-emulsifier B. Specifically, the composite emulsifier comprises the following components in parts by weight: 32 parts of primary emulsifier, 22 parts of co-emulsifier A (sulfonate), 15 parts of wetting agent, 5 parts of modified cyclodextrin, and 8 parts of slitting agent.

[0051] Comparative Example 2

[0052] The difference between this comparative example and Example 1 is that the proportions of the main emulsifier, co-emulsifier A, and co-emulsifier B are different. Specifically, the composite emulsifier comprises the following components in parts by weight: 25 parts of main emulsifier, 17 parts of co-emulsifier A (sulfonate), 12 parts of co-emulsifier B (oleic acid), 15 parts of wetting agent, 5 parts of modified cyclodextrin, and 8 parts of slitting agent.

[0053] Comparative Example 3

[0054] The difference between this comparative example and Example 1 is that the mass ratio of the main emulsifier, co-emulsifier A, and co-emulsifier B is not within the preferred range. Specifically, the composite emulsifier comprises the following components in parts by mass: 31 parts of main emulsifier, 15 parts of co-emulsifier A (sulfonate), 8 parts of co-emulsifier B (oleic acid), 15 parts of wetting agent, 5 parts of modified cyclodextrin, and 8 parts of slitting agent.

[0055] Comparative Example 4

[0056] The difference between this comparative example and Example 1 is that the co-emulsifier A is a compound of sodium dodecylbenzenesulfonate, sodium petroleum sulfonate and sodium dodecyl diphenyl ether disulfonate in a mass ratio of 1:1:1.

[0057] Comparative Example 5

[0058] The difference between this comparative example and Example 1 is that the modified cyclodextrin was not modified. Specifically, the composite emulsifier comprises the following components in parts by weight: 32 parts of primary emulsifier, 12 parts of co-emulsifier A (sulfonate), 10 parts of co-emulsifier B (oleic acid), 15 parts of wetting agent, 5 parts of γ-cyclodextrin, and 8 parts of slitting agent.

[0059] Comparative Example 6

[0060] The difference between this comparative example and Example 1 is the amount of 2-octenyl succinic anhydride added. The modified cyclodextrin is prepared as follows: 10 parts by mass of γ-cyclodextrin are dispersed in 100 parts of deionized water and stirred until a suspension is formed. 0.1 parts of 2-octenyl succinic anhydride are added to 3 parts of anhydrous ethanol to form a mixture. The mixture is added dropwise to the suspension, while the pH of the reaction system is controlled at 9 using a 4 wt% NaOH aqueous solution. The reaction continues until the pH of the system is constant. The pH of the reaction system is then adjusted to 6 using a 4 wt% HCl aqueous solution. After washing, centrifugation, drying, and pulverizing through an 80-mesh sieve, the modified cyclodextrin is obtained.

[0061] Performance testing

[0062] Oil-based drilling fluids were formulated using the composite emulsifiers prepared in Examples 1-2 and Comparative Examples 1-6. The basic formulation was: 280 mL of 0# diesel oil + 8.3 wt / vol% composite emulsifier + 0.1 wt / vol% organomontmorillonite + 15 mL of 25 wt% calcium chloride aqueous solution + 2.0 wt / vol% calcium oxide + 3.0 wt / vol% sulfonated asphalt + 1500 g of manganese tetroxide. The density of the prepared oil-based drilling fluid was 3.0 g / cm³. 3 Refer to GB / T16783.2 The properties of oil-based drilling fluids were determined in 2012. The results are shown in Table 1.

[0063] Table 1 Performance Test Results (-- indicates not tested)

[0064]

[0065]

[0066] As can be seen from Examples 1-2, the composite emulsifier prepared by the present invention has high emulsifying performance, good stability at high temperatures, and good stability at high concentrations (3.0 g / cm³). 3 The drilling fluid exhibits good rheological properties. Comparative examples 1-6 show that changing the conditions of the raw materials used in preparation leads to varying degrees of performance degradation in the composite emulsifier.

[0067] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite emulsifier for oil-based drilling fluids, characterized in that, The composite emulsifier comprises the following components in parts by weight: 30-40 parts of primary emulsifier, 10-20 parts of co-emulsifier A (sulfonate), 8-18 parts of co-emulsifier B (oleic acid), 12-17 parts of wetting agent, 3-8 parts of modified cyclodextrin, and 5-10 parts of cutting agent. The preparation method of the main emulsifier is as follows: (1) Mix 1 molar amount of ricinoleic acid and 1.1 molar amount of diethylenetriamine and react at a constant temperature of 165-170 °C until no byproduct water is produced to obtain product A; ； (2) Continue to slowly add 1.1 molar amount of acrylonitrile to product A, react at 40-45℃ for 2-3 hours, and distill under reduced pressure to obtain the main emulsifier; ； Co-emulsifier A is a compound of sodium dodecylbenzene sulfonate, sodium petroleum sulfonate, and sodium dodecyl diphenyl ether disulfonate in a mass ratio of 1.4-1.8:0.8-1.2:0.3-0.

7. The modified cyclodextrin is prepared as follows: 10 parts by mass of γ-cyclodextrin are dispersed in 100 parts of deionized water and stirred evenly to form a suspension; 0.5 parts of 2-octenyl succinic anhydride are added to 3 parts of anhydrous ethanol to prepare a mixture; the mixture is added dropwise to the suspension while controlling the pH of the reaction system to 8-9, and the reaction continues until the pH of the system is constant. The pH of the reaction system is then adjusted to 6, followed by washing, centrifugation, drying, and pulverizing through an 80-mesh sieve to obtain the modified cyclodextrin. The wetting agent is dodecyltrimethylammonium bromide.

2. The composite emulsifier for oil-based drilling fluid according to claim 1, characterized in that, The mass ratio of the primary emulsifier, co-emulsifier A, and co-emulsifier B is 3.2-3.3:1.1-1.2:

1.

3. The composite emulsifier for oil-based drilling fluid according to claim 1, characterized in that, The pH of the reaction system was controlled to be 8-9 using a 4wt% NaOH aqueous solution.

4. The composite emulsifier for oil-based drilling fluid according to claim 1, characterized in that, The pH of the reaction system was adjusted to 6 using a 4 wt% HCl aqueous solution.

5. The composite emulsifier for oil-based drilling fluids according to claim 1, characterized in that, The cutting agent is cutting agent D2833.

6. The method for preparing the composite emulsifier for oil-based drilling fluid according to any one of claims 1-5, characterized in that, The process includes the following steps: mixing the main emulsifier, co-emulsifier A, and co-emulsifier B, heating to 43-45℃, and stirring for 2-3 hours; adding the anti-temperature agent, heating to 55-57℃, and stirring for 1.5-2.5 hours; cooling to 25-30℃, and then adding the remaining components, stirring for 2-3 hours.

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