Oil-absorbing graphite, its preparation method and plugging agent for oil-based drilling fluid

Abstract

The present invention provides a method for preparing lipophilic adsorbent graphite. The present invention also provides a lipophilic adsorbent graphite prepared by the method of the present invention. The present invention also provides a lost circulation material for oil-based drilling fluids, which comprises the lipophilic adsorbent graphite of the present invention. The lost circulation material of the present invention has good temperature resistance and will not fail at high temperatures, thus avoiding the occurrence of repeated lost circulation. The lost circulation material of the present invention is dispersed in the oil-based drilling fluid and does not affect the rheology of the drilling fluid, solving the drawback that conventional graphite materials cannot be dispersed in oil-based drilling fluids, resulting in unsatisfactory lost circulation plugging effects.

Description

Technical Field

[0001] The present invention belongs to the field of oil drilling materials. Specifically, the present invention relates to an oil-wettable adsorbent graphite, a preparation method thereof, and a lost circulation material for oil-based drilling fluids. Background Art

[0002] Well loss is a phenomenon in which various working fluids leak into the formation under the action of pressure difference during various downhole operations such as drilling, cementing, well completion, testing, or well repair. Once well loss occurs, it not only delays drilling time, loses drilling fluid, damages the oil and gas reservoir, interferes with geological logging work, increases drilling costs, but also easily causes a series of complex situations such as stuck pipe, blowout, and well collapse, and even leads to wellbore abandonment, resulting in huge economic losses.

[0003] With the further understanding of different well loss causes, the research and development of lost circulation materials have been continuously progressing. In China, lost circulation materials have been used to treat well loss since the 1960s, and some basic research on lost circulation materials has been carried out. This stage is the period of plugging any leakage seen. Due to the insufficient understanding of the properties of lost circulation zones such as shallow formation loss, pay zone loss, and natural leakage cracks, and the limitations of lost circulation materials during this period, bridging lost circulation materials and hard and soft plugging materials were mainly used as lost circulation materials. When well loss occurred during this period, generally, according to the different pore sizes and positions of the lost circulation zone, the compound ratio of granular, flaky, and fibrous lost circulation materials was adjusted, and appropriate inert materials were added to complement them to enhance the plugging effect. Commonly used granular lost circulation materials include walnut shells, rubber particles, diatomaceous earth, asphalt, etc.; fibrous materials include sawdust, cotton fibers, linen fibers, etc.; flaky materials include mica flakes, rice husks, etc. Artificial fractures caused by fast drilling speed or fast pipe running during drilling can be plugged by using the non-curing characteristics of hard and soft plugging materials to form a non-flowing viscous substance. Such materials mainly include diesel bentonite slurry, shear thickening fluid, barite plug, and lime milk. The above several types of lost circulation materials can solve some losses and total losses caused by pores and fractures, but some complex losses cannot be well solved. Therefore, various new plugging agents such as chemical plugging agents, high water loss plugging agents, and mixed lost circulation thick slurries have emerged, providing effective means to deal with various types of well loss and improve the success rate of treating well loss.

[0004] In the second stage of the development of lost circulation materials, various targeted lost circulation materials were developed, including high-fluid-loss lost circulation materials, chemical lost circulation materials, and mixed lost circulation slurries. After the slurry of high-fluid-loss lost circulation materials enters the lost circulation zone, under the pressure difference generated by the drilling fluid column pressure and the formation pressure, it quickly loses water to form a filter cake, plugging the lost circulation channels. Such materials mainly include percolating materials, fibrous materials, diatomaceous earth, and porous inert materials, etc.; Chemical lost circulation materials utilize the static force, intermolecular force, and chemical bond force of polymers to cause the compound to form a bond at the interface to play a role in plugging. Such materials include gel lost circulation agents, resin lost circulation agents, and swelling lost circulation agents; The mixed lost circulation slurry is mainly composed of special cement and mixed cement slurry, adding different admixtures to improve the early strength and stability of the cement stone, making it have a higher pressure-bearing capacity. These several types of lost circulation materials can play a good role in plugging permeable lost circulation and fractured lost circulation. However, with the improvement of drilling technology requirements, malignant lost circulation such as cavernous lost circulation often occurs, and these conventional lost circulation materials cannot effectively play a role in plugging.

[0005] After the 1990s, people paid more attention to the serialization and standardization of lost circulation material products. In order to improve the efficiency of plugging, the transformation began from single lost circulation materials to composite lost circulation materials. The composite lost circulation materials developed in this stage mainly include acid-soluble high-fluid-loss temporary plugging agents, unidirectional pressure sealants, acid-soluble solidifying materials, etc. Composite lost circulation materials are mainly used to handle complex lost circulation, such as water layer lost circulation, gas layer lost circulation, long open-hole well lost circulation, and large fractures and large cavernous lost circulation, etc. For severe well leakage, using composite lost circulation materials can greatly improve the success rate of plugging.

[0006] Currently, the commonly used lost circulation materials in lost circulation construction are mostly bridging lost circulation materials and chemical gel lost circulation materials. Chemical plugging mainly plays a role in sealing through chemical reactions of polymers, including cross-linking reactions, curing reactions, and other methods. Chemical plugging has a good plugging effect for malignant lost circulation, but the chemical plugging reaction is relatively intense, the construction is complex, and the risk is relatively high. The construction process of bridging lost circulation materials is simple and the cost is low, which is the most commonly used on-site. However, some materials have poor temperature resistance and are prone to decomposition and failure at high temperatures, resulting in repeated lost circulation of the lost circulation zone. At the same time, these materials have problems such as sealing the door and cannot be soaked for a long time, and the plugging effect is sometimes not ideal.

[0007] Some researchers utilized skeleton materials with high matching of sponge action and fractures for application. Such as filter sponges, fireproof sponges, etc. For example, CN103923627A discloses an oil and gas well drilling pressure-bearing lost circulation agent and its preparation and application. Specifically, CN103923627A proposes an oil and gas well drilling pressure-bearing lost circulation agent, which is composed of elastic sponge fibers, oil well cement, ground granulated blast furnace slag, calcium bentonite, mica powder, and clear water, and can be used for pressure-bearing lost circulation in oil and gas well drilling.

[0008] At present, there are few plugging agents for oil-based drilling fluid leakage. Some of them have problems such as poor compatibility between the plugging particles and the oil-based drilling fluid, floating in the oil-based drilling fluid, being difficult to disperse, and being unable to enter the wellbore through the circulation system. Summary of the Invention

[0009] The purpose of the present invention is to provide a preparation method of lipophilic adsorptive graphite. The lipophilic adsorptive graphite prepared by the method of the present invention can effectively improve the performance of the plugging agent when used as a plugging agent. Another purpose of the present invention is to provide a plugging agent for oil-based drilling fluid, which solves the compatibility problem between the plugging particles and the oil-based drilling fluid.

[0010] In the first aspect, the present invention provides a preparation method of lipophilic adsorptive graphite, which comprises the following steps:

[0011] (1) Mix the powdered adsorptive particles with the lipophilic solution to prepare a lipophilic adsorptive particle suspension;

[0012] (2) Add graphite to the lipophilic adsorptive particle suspension, stir until it becomes paste-like, and obtain lipophilic adsorptive powder after drying;

[0013] (3) Mold the lipophilic adsorptive powder and obtain lipophilic adsorptive graphite after roasting.

[0014] Preferably, in the preparation method of the lipophilic adsorptive graphite of the present invention, the particle size of the powdered adsorptive particles in the step (1) is below 20 μm.

[0015] Preferably, in the preparation method of the lipophilic adsorptive graphite of the present invention, the powdered adsorptive particles are prepared by a method comprising the following steps: sinter the adsorptive particles and grind them to obtain powdered adsorptive particles.

[0016] Preferably, in the preparation method of the lipophilic adsorptive graphite of the present invention, the sintering treatment is carried out under the following conditions: the sintering treatment temperature is 350°C to 650°C, and the sintering treatment time is 1 to 5 h.

[0017] Preferably, in the preparation method of the lipophilic adsorptive graphite of the present invention, the stirring in the step (2) is carried out at 60°C to 80°C.

[0018] Preferably, in the preparation method of the lipophilic adsorptive graphite of the present invention, the drying in the step (2) is carried out under the following conditions: the drying temperature is 40°C to 60°C, the drying time is 18 to 36 h, preferably 24 to 36 h.

[0019] Preferably, in the method for preparing the lipophilic adsorbent graphite according to the present invention, the roasting in step (3) is carried out under vacuum, and the conditions are as follows: the roasting temperature is 850-870 °C, the roasting time is 1-6 h, preferably 2-4 h.

[0020] Preferably, in the method for preparing the lipophilic adsorbent graphite according to the present invention, the graphite is expandable graphite, flake graphite, micro-powder graphite, or spherical graphite.

[0021] Preferably, in the method for preparing the lipophilic adsorbent graphite according to the present invention, the adsorbent particles are diatomaceous earth and / or sepiolite.

[0022] Preferably, in the method for preparing the lipophilic adsorbent graphite according to the present invention, the lipophilic solution is selected from one or more of sodium dodecyl benzene sulfonate solution, OP-10 solution, and aqueous polyurethane solution.

[0023] Preferably, in the method for preparing the lipophilic adsorbent graphite according to the present invention, the particle size of the lipophilic adsorbent graphite is 50-200 mesh.

[0024] Preferably, in the method for preparing the lipophilic adsorbent graphite according to the present invention, the mass ratio of the graphite, adsorbent particles, and lipophilic solution is 3-5:0.5-1.8:7-15, where the mass of the lipophilic solution is calculated based on the mass of the solute.

[0025] In a second aspect, the present invention provides the lipophilic adsorbent graphite prepared by the method for preparing the lipophilic adsorbent graphite of the present invention.

[0026] In a third aspect, the present invention provides a lost circulation material for oil-based drilling fluid, which includes elastic sponge, ultra-fine fiber, quartz, ultra-fine calcium carbonate, sawdust, graphite, and rubber particles; wherein,

[0027] The graphite is the lipophilic adsorbent graphite of the present invention.

[0028] Preferably, in the lost circulation material for oil-based drilling fluid according to the present invention, the addition amount of each component in 100 parts of the oil-based drilling fluid is in weight percentage as follows:

[0029]

[0030] Preferably, in the lost circulation material for oil-based drilling fluid according to the present invention, the elastic sponge is polyurethane with a mesh structure and / or lipophilic polyurethane modified by nano-silica.

[0031] Preferably, in the lost circulation material for oil-based drilling fluid according to the present invention, the lipophilic polyurethane modified by nano-silica is carried out by a method including the following steps:

[0032] A) Prepare a microemulsion by mixing vinyltrimethoxysilane, n-hexanol, and n-pentane;

[0033] B) Immerse the sponge in the microemulsion, add tetramethyl orthosilicate dropwise to obtain a mixture, and carry out a reaction;

[0034] C) After the reaction of the mixture, add absolute ethanol and stir well, then take out the sponge from the solution, rinse it with deionized water, and then dry it to obtain the lipophilic polyurethane modified with nano-silica.

[0035] Preferably, in the lost circulation material for oil-based drilling fluid of the present invention, in the microemulsion, the mass ratio of vinyltrimethoxysilane, n-hexanol, and n-pentane is 2-4:6-9:0.5-1.5.

[0036] Preferably, in the lost circulation material for oil-based drilling fluid of the present invention, the volume of tetramethyl orthosilicate accounts for 1%-5% of the volume of the microemulsion.

[0037] Preferably, in the lost circulation material for oil-based drilling fluid of the present invention, the reaction of the mixture is carried out in a constant temperature water bath at 20-30°C.

[0038] Preferably, in the lost circulation material for oil-based drilling fluid of the present invention, drying is carried out in a drying oven at 50-60°C.

[0039] In a specific embodiment of the present invention, when the lost circulation material of the present invention uses the lipophilic adsorbent graphite of the present invention, a commercially available elastic sponge can be used. Of course, in the case where the lost circulation material of the present invention uses the lipophilic adsorbent graphite of the present invention, if the elastic sponge is also the elastic sponge prepared by the method of the present invention, the lost circulation material of the present invention will have more excellent performance.

[0040] In the best embodiment of the present invention, the lost circulation material of the present invention uses the lipophilic adsorbent graphite of the present invention, and at the same time the elastic sponge is the elastic sponge prepared by the method of the present invention. In this best embodiment, a highly elastic pore network material (the elastic sponge prepared by the method of the present invention) is used as the skeleton, which is easy to form a bridge inside the crack; at the same time, an adsorbent particle with good lipophilicity (the lipophilic adsorbent graphite of the present invention) is used as the filler and adsorbent, which has good dispersibility in the oil-based drilling fluid, can effectively fill the pore network, improve the compactness and erosion resistance of the plugging layer, improve the success rate of lost circulation plugging, avoid the occurrence of repeated lost circulation, and has a good lost circulation plugging effect for fracture-vug type lost circulation.

[0041] The present invention has the following advantages compared with the prior art:

[0042] (1) The lost circulation material of the present invention has good temperature resistance and will not fail at high temperatures, and can avoid the occurrence of repeated lost circulation.

[0043] (2) The plugging agent of the present invention is dispersed in the oil-based drilling fluid and does not affect the rheology of the drilling fluid, solving the disadvantage that conventional graphite materials cannot be dispersed in the oil-based drilling fluid, resulting in unsatisfactory plugging effects.

[0044] (3) The elastic sponge prepared by the method of the present invention has good elasticity and good matching with cracks, which is beneficial to entering the deep part of the cracks. At the same time, it can restore its shape after entering the cracks, which is beneficial to implementing bridging and networking, and has good plugging effects on various types of leakage. Detailed implementation manners

[0045] The present invention will be further described below in conjunction with specific embodiments, but it does not constitute any limitation to the present invention.

[0046] In the embodiments of the present invention, unless otherwise specified, all raw materials are commercially available. The elastic sponge is purchased from Shenzhen Dongtai Sponge Products Factory, the ultra-fine fiber is purchased from Hebei Yixin Mineral Products Co., Ltd., the ultra-fine calcium carbonate is purchased from Hebei Jinyuan Chemical Industry, and the rubber particles are purchased from Hebei Chuanqing Building Materials.

[0047] Example 1

[0048] The addition amounts of the components of the high-elasticity plugging agent for oil-based drilling fluid in 100 parts of the oil-based drilling fluid are as follows by weight percentage:

[0049]

[0050] The preparation steps of the lipophilic adsorbent graphite are as follows:

[0051] 25 g of diatomite particles are sintered at 350 °C for 1 h and ground to a particle size of 5 μm; then the diatomite particles are poured into an aqueous solution containing 335 g of OP-10 to prepare a lipophilic adsorbent particle suspension; then 100 g of graphite is poured into the lipophilic adsorbent particle suspension and mechanically stirred at 60 °C until it becomes a paste; then, it is dried at 40 °C for 24 hours to obtain a lipophilic adsorbent powder; the lipophilic adsorbent powder is placed on a press at room temperature, molded, and then placed in a vacuum furnace. Under vacuum conditions, it is heated to 850 °C and held for 2 h, and then cooled to room temperature. The particle size of the lipophilic adsorbent graphite prepared in this example is 200 mesh.

[0052] Example 2

[0053] The addition amounts of the components of the high-elasticity plugging agent for oil-based drilling fluid in 100 parts of the oil-based drilling fluid are as follows by weight percentage:

[0054]

[0055]

[0056] The preparation steps of the lipophilic adsorbent graphite are as follows:

[0057] Sinter the sepiolite particles at 650 °C for 5 h, and grind them to a particle size of less than 20 μm;

[0058] Then pour 25 g of sepiolite particles into an aqueous solution containing 187 g of sodium dodecylbenzenesulfonate to prepare a lipophilic adsorbent particle suspension; then pour 75 g of graphite into the lipophilic adsorbent particle suspension, and mechanically stir at 80 °C until it becomes a paste; then, dry at 60 °C for 24 hours to obtain a lipophilic adsorbent powder; place the lipophilic adsorbent powder on a press at room temperature, mold it, then place it in a vacuum furnace, heat it up to 870 °C under vacuum conditions, hold for 2 h, and cool to room temperature.

[0059] Example 3

[0060] The addition amounts of the components of the high-elastic plugging agent for oil-based drilling fluids in 100 parts of oil-based drilling fluids are as follows by weight percentage:

[0061]

[0062] The preparation steps of the lipophilic adsorbent graphite are as follows:

[0063] Sinter the sepiolite particles at 650 °C for 5 h, and grind them to a particle size of less than 20 μm;

[0064] Then pour 10 g of sepiolite particles into an aqueous solution containing 125 g of waterborne polyurethane to prepare a lipophilic adsorbent particle suspension; then pour 37.5 g of graphite into the lipophilic adsorbent particle suspension, and mechanically stir at 80 °C until it becomes a paste; then, dry at 60 °C for 24 hours to obtain a lipophilic adsorbent powder; place the lipophilic adsorbent powder on a press at room temperature, mold it, then place it in a vacuum furnace, heat it up to 860 °C under vacuum conditions, hold for 2 h, and cool to room temperature.

[0065] Example 4

[0066] The addition amounts of the components of the high-elastic plugging agent for oil-based drilling fluids in 100 parts of oil-based drilling fluids are as follows by weight percentage:

[0067]

[0068] The preparation steps of the lipophilic adsorbent graphite are as follows:

[0069] Sinter the sepiolite particles at 550 °C for 3 h, and grind them to a particle size of less than 10 μm;

[0070] Then, 10 g of sepiolite particles are poured into an aqueous solution containing 171 g of sodium dodecylbenzene sulfonate to prepare a lipophilic adsorptive particle suspension; then, 60 g of graphite is poured into the lipophilic adsorptive particle suspension, and mechanically stirred at 80°C until it becomes a viscous paste; then, it is dried at 60°C for 24 hours to obtain a lipophilic adsorptive powder; the lipophilic adsorptive powder is placed on a press for compression molding at room temperature, and then placed in a vacuum furnace, heated to 870°C under vacuum conditions, kept warm for 2 hours, and cooled to room temperature.

[0071] Example 5

[0072] The addition amount of each component of the high elastic plugging agent for oil-based drilling fluid in 100 parts of oil-based drilling fluid is as follows by weight percentage:

[0073]

[0074] The preparation steps of the oleophilic adsorbent graphite are:

[0075] The diatomaceous earth particles were sintered at 550°C for 3 h and ground to a particle size of less than 10 μm;

[0076] Then, 20 g of diatomaceous earth particles are poured into an aqueous solution containing 160 g of sodium dodecylbenzene sulfonate to prepare a lipophilic adsorptive particle suspension; then, 60 g of graphite is poured into the lipophilic adsorptive particle suspension, and mechanically stirred at 80° C. until it becomes a viscous paste; then, it is dried at 60° C. for 24 hours to obtain a lipophilic adsorptive powder; the lipophilic adsorptive powder is placed on a press for compression molding at room temperature, and then placed in a vacuum furnace, heated to 870° C. under vacuum conditions, kept warm for 2 hours, and cooled to room temperature.

[0077] The elastic sponge is prepared by a method comprising the following steps:

[0078] 500 ml of a microemulsion is prepared with vinyltrimethoxysilane, n-hexanol and n-pentane in a mass ratio of 2:9:1.5; a sponge is immersed in the microemulsion, 20 ml of tetramethyl orthosilicate is added dropwise to obtain a mixed solution, and the mixed solution is reacted in a constant temperature water bath at 28°C; after the mixed solution reacts, anhydrous ethanol is added and stirred sufficiently, and then the sponge is taken out from the solution, rinsed with deionized water, and then dried at 60°C.

[0079] Example 6

[0080] The addition amount of each component of the high elastic plugging agent for oil-based drilling fluid in 100 parts of oil-based drilling fluid is as follows by weight percentage:

[0081]

[0082] The preparation steps of the oleophilic adsorbent graphite are:

[0083] The diatomite particles were sintered at 550 °C for 3 h and ground to a particle size below 10 μm.

[0084] Then, 20 g of diatomite particles were poured into an aqueous solution containing 162 g of waterborne polyurethane to prepare an oleophilic adsorbent particle suspension mixture. Then, 65 g of graphite was poured into the oleophilic adsorbent particle suspension mixture and mechanically stirred at 80 °C until it became a paste. Then, it was dried at 60 °C for 24 h to obtain an oleophilic adsorbent powder. The oleophilic adsorbent powder was placed on a press at room temperature, molded, and then placed in a vacuum furnace. Under vacuum conditions, it was heated to 870 °C and held for 2 h, and then cooled to room temperature.

[0085] Comparative Example 1

[0086] The addition amounts of the components of the high-elasticity lost circulation material for oil-based drilling fluids in 100 parts of oil-based drilling fluid are as follows by weight percentage:

[0087]

[0088] Lost circulation material performance test:

[0089] An evaluation experiment was carried out using a wedge-shaped long crack plugging experimental device. Table 1 shows the results of the lost circulation plugging evaluation experiment.

[0090] Table 1 Results of the wedge-shaped long crack plugging experiment (2×1 mm)

[0091]

[0092] The lost circulation plugging effect of Example 5 is better than that of Examples 2 and 3, and the lost circulation plugging effects of Examples 2 and 3 are better than that of Example 7. Compared with Example 7, with the addition of oleophilic adsorbent graphite in the lost circulation material, the crack plugging area moves forward, the pressure-bearing capacity of the plugging layer increases significantly, and the crack leakage amount decreases; at the same time, the increase in the concentration of oleophilic adsorbent graphite also helps to reduce the leakage amount to a certain extent. With the addition of oleophilic adsorbent graphite and modified elastic sponge in the lost circulation material, the crack plugging area moves forward further, the pressure-bearing capacity of the plugging layer is further improved, and the crack leakage amount decreases, fully demonstrating the plugging effect of oleophilic adsorbent graphite and modified elastic sponge on cracks, and the lost circulation plugging effect is further improved.

[0093] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as provided, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A plugging agent for oil-based drilling fluids, wherein, The addition amount of each component in 100 parts of oil-based drilling fluid is in weight percentage as follows: The preparation method of the lipophilic adsorptive graphite includes the following steps: (1) Mix the powdery adsorptive particles with the lipophilic solution to prepare a lipophilic adsorptive particle suspension; (2) Add graphite to the lipophilic adsorptive particle suspension, stir until it becomes paste-like, and obtain lipophilic adsorptive powder after drying; (3) Mold the lipophilic adsorptive powder and obtain lipophilic adsorptive graphite after roasting; The graphite is expandable graphite, flake graphite, micro-powder graphite or spherical graphite; The adsorptive particles are diatomite and / or sepiolite; The lipophilic solution is selected from one or more of sodium dodecylbenzenesulfonate solution, OP-10 solution and aqueous polyurethane solution; The roasting in step (3) is carried out under vacuum, and the roasting temperature is 850 - 870 °C.

2. The lost circulation material for oil-based drilling fluid according to claim 1, wherein, The particle size of the powdery adsorptive particles in step (1) is below 20 μm.

3. The lost circulation material for oil-based drilling fluids according to claim 1, wherein, The powdery adsorptive particles in step (1) are prepared by a method including the following steps: sinter the adsorptive particles and grind them to obtain powdery adsorptive particles.

4. The lost circulation material for oil-based drilling fluid according to claim 3, wherein, The sintering treatment is carried out under the following conditions: the sintering treatment temperature is 350 °C - 650 °C, and the sintering treatment time is 1 - 5 h.

5. The lost circulation material for oil-based drilling fluids according to claim 1, wherein, The stirring in step (2) is carried out at 60 °C - 80 °C.

6. The lost circulation material for oil-based drilling fluid according to claim 5, wherein, The drying in step (2) is carried out under the following conditions: the drying temperature is 40 °C - 60 °C, and the drying time is 18 - 36 h.

7. The lost circulation material for oil-based drilling fluid according to claim 6, wherein, The drying time is 24 - 36 h.

8. The lost circulation material for oil-based drilling fluid according to any one of claims 1-7, wherein, The roasting time in step (3) is 1 - 6 h.

9. The lost circulation material for oil-based drilling fluid according to claim 8, wherein, The roasting time is 2 - 4 h.

10. The lost circulation material for oil-based drilling fluids according to any one of claims 1-7, wherein, The particle size of the lipophilic adsorptive graphite is 50 - 200 mesh.

11. The lost circulation material for oil-based drilling fluid according to any one of claims 1-7, wherein, The mass ratio of the graphite, adsorptive particles, and lipophilic solution is 3 - 5:0.5 - 1.8:7 - 15, where the mass of the lipophilic solution is calculated based on the mass of the solute.

12. The lost circulation material for oil-based drilling fluid according to any one of claims 1-7, wherein, The elastic sponge is polyurethane with a mesh structure and / or lipophilic polyurethane modified by nano-silica.

13. The lost circulation material for oil-based drilling fluid according to claim 12, wherein, The modification of the lipophilic polyurethane by nano-silica is carried out by a method including the following steps: A) Prepare a microemulsion by mixing vinyltrimethoxysilane, n-hexanol, and n-pentane; B) Immerse the sponge in the microemulsion, drop in tetraethyl orthosilicate, obtain a mixed solution, and carry out a reaction; C) After the mixed solution reacts, add absolute ethanol and stir well, then take out the sponge from the solution, rinse it with deionized water, and then dry it to obtain the lipophilic polyurethane modified by nano-silica.

14. The lost circulation material for oil-based drilling fluid according to claim 13, wherein, In the microemulsion, the mass ratio of vinyltrimethoxysilane, n-hexanol, and n-pentane is 2 - 4:6 - 9:0.5 - 1.

5.

15. The lost circulation material for oil-based drilling fluids according to claim 13 or 14, wherein, The volume of tetraethyl orthosilicate accounts for 1% - 5% of the volume of the microemulsion.

16. The lost circulation material for oil-based drilling fluids according to claim 13 or 14, wherein, The reaction of the mixed solution is carried out in a constant temperature water bath at 20 - 30 °C.

17. The lost circulation material for oil-based drilling fluids according to claim 13 or 14, wherein, The drying is carried out in a drying oven at 50 - 60 °C.

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