A composition for drilling a well and its use

Abstract

The application provides a drilling composition and application thereof. The drilling composition comprises a surfactant, a foam stabilizing tackifier, a vegetable oil and modified nanosilica, has good stability, temperature resistance and salt resistance, has small reservoir damage, has good biodegradability and is a degradable environment-friendly oil-based drilling fluid.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of drilling, and particularly relates to a drilling composition and application thereof. BACKGROUND

[0002] Oil-based drilling fluid has strong inhibition of hydration dispersion, good lubrication effect, strong high-temperature resistance and pollution resistance, and good reservoir protection performance, and has been widely used in high-temperature and high-pressure wells, large displacement horizontal wells and other high-difficulty complex wells at home and abroad. Due to its good inhibition, oil-based drilling fluid has always been the first choice for shale formation drilling. At present, oil-based drilling fluid generally uses diesel as base oil, which has the advantage of low cost, but at the same time, it has high aromatic hydrocarbon content and high toxicity, and has the problems of poor environmental protection, difficult disposal of drilling waste, and inability to meet environmental protection requirements. With the continuous strengthening of environmental protection, its application is limited, for example, oil-based drilling fluid has been restricted in use in environmentally sensitive areas. Therefore, it is urgent to develop an environmentally friendly oil-based drilling fluid with low toxicity and biodegradability. SUMMARY

[0003] In view of the problems of high aromatic hydrocarbon content, high toxicity, poor environmental protection, difficult disposal of drilling waste, and inability to meet environmental protection requirements of the oil-based drilling fluid with diesel as base oil in the prior art, the purpose of the present application is to provide an environmentally friendly oil-based drilling fluid with low toxicity and biodegradability.

[0004] To achieve the above purpose, the present application provides a drilling composition, which comprises a surfactant, a foam stabilizing and viscosity increasing agent, a vegetable oil and modified nano silicon dioxide.

[0005] According to one specific embodiment of the present application, the mass of the vegetable oil is 100%, the amount of the surfactant is 0.15 to 0.4 wt%, the amount of the foam stabilizing and viscosity increasing agent is 0.25 to 0.45 wt%, and the amount of the modified nano silicon dioxide is 0.35 to 0.65 wt%.

[0006] According to one specific embodiment of the present application, the structural formula of the surfactant is shown as formula I:

[0007]

[0008] wherein n is 1 to 5, and R is a C5 to C 18 alkyl group.

[0009] Preferably, in formula I, n is 3, and R is a C 12 to C 18 alkyl group (preferably a C 18 alkyl group).

[0010] According to an embodiment of the present application, the surfactant is prepared by the following method:

[0011] reacting the fatty alcohol and ethylene oxide under the action of a catalyst to obtain the surfactant;

[0012] Preferably, the surfactant can be directly used without purification.

[0013] Preferably, the molar ratio of the fatty alcohol to ethylene oxide is 1 : (1 to 5).

[0014] Preferably, the molar ratio of the fatty alcohol to ethylene oxide is 1 :5.

[0015] Preferably, the total mass of the fatty alcohol and ethylene oxide is 100%, and the amount of the catalyst is 15wt%.

[0016] Preferably, the fatty alcohol is a C 12 to C 18 fatty alcohol (preferably octadecanol); and / or

[0017] The catalyst is sodium hydroxide.

[0018] Preferably, the first reaction is carried out in anhydrous and anaerobic environment; and / or

[0019] The temperature of the first reaction is 70 to 100°C (preferably 70°C); and / or the time length is 3 to 4h (preferably 3h).

[0020] According to an embodiment of the present application, the foam stabilizing and viscosity increasing agent is a polycondensation product of apricot kernel gum and polyaspartic acid.

[0021] According to an embodiment of the present application, the foam stabilizing and viscosity increasing agent is prepared by the following method:

[0022] reacting the apricot kernel gum and polyaspartic acid under the action of an initiator to obtain the foam stabilizing and viscosity increasing agent;

[0023] Preferably, the mass ratio of the apricot kernel gum to polyaspartic acid is 1 :4.1; and / or

[0024] The total mass of the apricot kernel gum and polyaspartic acid is 100%, and the amount of the initiator is 1 to 1.3wt% (preferably 1.18wt%);

[0025] Preferably, the initiator is a persulfate salt (preferably ammonium persulfate).

[0026] Preferably, the apricot kernel gum and water are mixed first, then the polyaspartic acid and initiator are added, and then the second reaction is carried out; and / or

[0027] purifying the reaction product obtained from the second reaction to obtain the foam stabilizing tackifier;

[0028] Preferably, the apricot kernel gum and water are mixed at 70 to 100°C (preferably 85°C); and / or

[0029] The second reaction is carried out at 70 to 100°C (preferably 90°C) for 4h; and / or

[0030] The reaction product obtained from the second reaction is purified by ethanol precipitation;

[0031] Preferably, the reaction product obtained from the second reaction is mixed with ethanol to produce a precipitate, the precipitate is collected by filtration, and dried to obtain the purified foam stabilizing tackifier.

[0032] According to one specific embodiment of the present application, the polyaspartic acid has a weight average molecular weight of 1000 to 5000 (preferably 2000 to 3000).

[0033] In the present application, the apricot kernel gum is a resin collected from the trunk of apricot trees, and is a gum-like substance mixed into apricot kernel processing.

[0034] According to one specific embodiment of the present application, the plant oil is modified white oil.

[0035] According to one specific embodiment of the present application, the modified white oil is palmitate-modified white oil.

[0036] According to one specific embodiment of the present application, the modified nano-silica is nano-silica modified by a silane coupling agent;

[0037] Preferably, the modified nano-silica has a particle size of 40 to 50 nm.

[0038] According to one specific embodiment of the present application, the modified nano-silica is prepared by the following method:

[0039] The nano-silica and the silane coupling agent are subjected to a third reaction to obtain the modified nano-silica;

[0040] Preferably, the liquid to solid ratio of the silane coupling agent to the nano-silica is 5 mL: 1 g;

[0041] Preferably, the nano-silica is a nano-silica dispersion liquid; and / or

[0042] The silane coupling agent is a silane coupling agent aqueous solution;

[0043] Preferably, in the nano-silica dispersion liquid, the dispersant is anhydrous ethanol;

[0044] Preferably, the third reaction is carried out under stirring condition.

[0045] Preferably, the third reaction is carried out under the condition of condensation reflux at 70 DEG C for 3h.

[0046] Preferably, the reaction product obtained from the third reaction is purified by anhydrous ethanol precipitation method.

[0047] Preferably, the reaction product obtained from the third reaction is washed by anhydrous ethanol, and the filter residue is collected and dried to obtain the modified nano-silica.

[0048] Preferably, the drying temperature is 70 DEG C.

[0049] According to one specific embodiment of the present application, the silane coupling agent is KH-550.

[0050] The application provides an application of the drilling composition as an oil-based drilling fluid.

[0051] The present application has the following advantages:

[0052] In view of the problems of high aromatic hydrocarbon content, high toxicity, poor environmental protection, difficult disposal of drilling waste and failure to meet environmental protection requirements of the conventional oil-based drilling fluid in the prior art, the present application provides a drilling composition and an application thereof, wherein the drilling composition comprises a surfactant, a foam stabilizing and viscosity increasing agent, vegetable oil and modified nano-silica, and is a degradable and environmentally friendly oil-based drilling fluid.

[0053] (1) Good stability, temperature resistance and salt resistance: without adding KCl aqueous solution, the half-life of the drilling composition provided by the present application is more than 115 min at normal temperature, and the half-life after aging at 180 DEG C is not less than 110 min, and the half-life is long; the addition of KCl aqueous solution does not cause the half-life of the drilling composition at normal temperature and after aging at 180 DEG C to decrease greatly, and after adding KCl aqueous solution with a KCl mass fraction of 2% to 8%, the half-life maintenance rate of the drilling composition at normal temperature is 95.9% to 103.8%, and the half-life maintenance rate of the drilling composition after aging at 180 DEG C is 92.1% to 105.5%; under the condition of adding or not adding KCl aqueous solution, the half-life of the drilling composition with the same formula after aging at 180 DEG C is more than 90% of the half-life at normal temperature; the half-life of the drilling composition with the same formula and adding the same KCl mass fraction of KCl aqueous solution after aging at 180 DEG C is also more than 90% of the half-life at normal temperature, which proves that the drilling composition provided by the present application has good stability and salt resistance, and can resist high temperature of not less than 180 DEG C;

[0054] (2) Small reservoir damage: the reservoir permeability recovery value Rd of the drilling composition provided by the present application is more than 85%, which has good protection performance for reservoirs, and overcomes the shortcomings of the conventional oil-based drilling fluid in damaging reservoirs in the prior art;

[0055] (3) Good biodegradability: the BOD5 value of the drilling composition provided by the present application is 84% to 89% of the standard BOD5 value, which has good biodegradability and is a degradable oil-based drilling fluid, and is more friendly to the environment. DETAILED DESCRIPTION

[0056] The present application will be further described in conjunction with the examples, but the examples of the present application are only exemplary descriptions, and the implementation manner does not constitute a limitation on the present application in any case.

[0057] The room temperature or normal temperature below refers to 25 DEG C.

[0058] Preparation of surfactant

[0059] Example 1

[0060] 1.841g of octadecanol and 1.5g of ethylene oxide are added to a dry reaction kettle, oxygen is removed by nitrogen, then 0.5g of sodium hydroxide is added as a catalyst, and the reaction is carried out in anhydrous and oxygen-free environment at a temperature of 70 DEG C for 3h, to obtain a surfactant with a structural formula as shown in formula I, which can be directly used without purification; according to the raw materials used and the amount ratio of the raw materials, in formula I, R is C18 alkyl, n has a value of 3.

[0061] Preparation of foam stabilizing viscosity enhancer

[0062] The apricot gum used in this example is a resin collected from the trunk of apricot trees, mixed with a gelatinous substance processed from apricot pulp, purchased from Zhengzhou Hengduobao Chemical Co., Ltd.

[0063] The weight average molecular weight of the polyaspartic acid used in this example is 2000 to 3000.

[0064] Example 2

[0065] 1) Mix 50 ml of distilled water and 1 g of apricot gum, heat to 85°C, and stir until a paste is formed;

[0066] 2) Then add 4.1 g of polyaspartic acid and 0.06 g of ammonium persulfate, heat to 90°C and react for 4 h;

[0067] 3) Finally, the product obtained after step 2) is purified by ethanol precipitation: add ethanol to produce a white precipitate, filter, dry, and dry to constant weight to obtain a grayish white powder, which is the purified foam stabilizing viscosity enhancer.

[0068] Preparation of modified nanosilica

[0069] Example 3

[0070] 1) Weigh 1 g of nanosilica with an average particle size of 50 nm using a balance, and measure 30 mL of absolute ethanol using a graduated cylinder. Mix and add to a three-necked flask. Stir at room temperature to disperse the nanosilica evenly in the absolute ethanol to obtain a nanosilica dispersion;

[0071] 2) Measure 5 mL of silane coupling agent KH-550 using a graduated cylinder, then mix with water at a volume ratio of 1:2, stir to hydrolyze the silane coupling agent completely, and stop stirring when cooled to room temperature to obtain a silane coupling agent aqueous solution;

[0072] 3) Mix the silane coupling agent aqueous solution and the nanosilica dispersion, and stir thoroughly until well mixed. In a constant-temperature magnetic stirrer, react at 70°C for 3 h under condensation reflux;

[0073] 4) After the reaction is complete, wash and filter the reaction product repeatedly with absolute ethanol until the filtrate is clear and transparent. Dry the filter cake in a vacuum drying oven at 70°C, grind, and obtain modified nanosilica particles with a particle size of 40 to 50 nm.

[0074] Formulation of drilling composition

[0075] The modified white oil used in Examples 4 to 6: a palmitate modified white oil, purchased from Hebei Xianzheng New Material Co., Ltd.

[0076] Example 4

[0077] The components and amounts of the drilling composition provided in this example: the mass of the modified white oil is 100%, the amount of the surfactant prepared in Example 1 is 0.15 wt%, the amount of the foam stabilizing thickening agent prepared in Example 2 is 0.25 wt%, and the amount of the modified nanosilica prepared in Example 3 is 0.35 wt%.

[0078] (1) The modified white oil was added to a stirrer, the speed was adjusted to 12000 r / min, and the modified white oil was stirred at high speed for 15 min;

[0079] (2) The foam stabilizing thickening agent prepared in Example 2 and the modified nanosilica prepared in Example 3 were added, and stirring was continued at 12000 r / min for 15 min to fully mix the components with the modified white oil. Finally, the surfactant prepared in Example 1 was added, and stirring was performed at 12000 r / min for 2 min to prepare the drilling composition 1.

[0080] Example 5

[0081] The components and amounts of the drilling composition provided in this example: the mass of the modified white oil is 100%, the amount of the surfactant prepared in Example 1 is 0.4 wt%, the amount of the foam stabilizing thickening agent prepared in Example 2 is 0.45 wt%, and the amount of the modified nanosilica prepared in Example 3 is 0.65 wt%.

[0082] (1) The modified white oil was added to a stirrer, the speed was adjusted to 12000 r / min, and the modified white oil was stirred at high speed for 15 min;

[0083] (2) The foam stabilizing thickening agent prepared in Example 2 and the modified nanosilica prepared in Example 3 were added, and stirring was continued at 12000 r / min for 15 min to fully mix the components with the modified white oil. Finally, the surfactant prepared in Example 1 was added, and stirring was performed at 12000 r / min for 2 min to prepare the drilling composition 2.

[0084] Example 6

[0085] The components and amounts of the drilling composition provided in this example: the mass of the modified white oil is 100%, the amount of the surfactant prepared in Example 1 is 0.3 wt%, the amount of the foam stabilizing thickening agent prepared in Example 2 is 0.35 wt%, and the amount of the modified nanosilica prepared in Example 3 is 0.5 wt%.

[0086] (1) Add the modified white oil into a stirrer, adjust the speed to 12000 r / min, and stir the modified white oil at high speed for 15 min;

[0087] (2) Add the foam stabilizing and viscosity increasing agent prepared in Example 2 and the modified nano-silicon dioxide prepared in Example 3, continue to stir at 12000 r / min for 15 min to fully mix the components with the modified white oil, finally add the surfactant prepared in Example 1, stir at 12000 r / min for 2 min, and prepare the drilling composition 3.

[0088] Test Example 1 - Determination of liquid yield half-life of drilling composition

[0089] The half-life t1 / 2 of the drilling compositions 1 to 3 prepared in Examples 4 to 6 under different conditions was determined according to the following steps to evaluate the foam stabilizing performance of the drilling compositions.

[0090] i. Determination of liquid yield half-life t1 / 2 at normal temperature and different KCl addition amounts

[0091] A. Take 1000 ml of the just prepared drilling composition 1, pour it into a clean and dry 1000 ml graduated cylinder, start the stopwatch after pouring, and observe the liquid level of the drilling composition 1 in the graduated cylinder. When the drilling composition 1 separates out 500 ml of liquid, stop the stopwatch and record the liquid yield half-life t1 / 2 of the drilling composition 1 without adding KCl;

[0092] The liquid yield half-life t1 / 2 of the drilling compositions 2 and 3 without adding KCl was determined in the same way;

[0093] B. Take 1000 ml of the just prepared drilling composition 1, a total of 4 portions, and pour them into 4 clean and dry 1500 ml graduated cylinders, respectively. Add 200 ml of KCl aqueous solution with KCl mass fraction of 2%, 4%, 6%, and 8% to the 4 graduated cylinders, respectively. Determine the liquid yield half-life t1 / 2 of the drilling composition 1 with the addition of KCl aqueous solution with KCl mass fraction of 2%, 4%, 6%, and 8% according to the determination method in step A;

[0094] Then, the liquid yield half-life t1 / 2 of the drilling compositions 2 and 3 with the addition of KCl aqueous solution with KCl mass fraction of 2%, 4%, 6%, and 8% was determined according to the determination method in step B;

[0095] The above determination results are shown in Table 1.

[0096] Table 1. Liquid yield half-life of drilling composition at normal temperature

[0097]

[0098] As shown in Table 1, without adding KCl aqueous solution, the fluid yield half-lives of the drilling compositions 1 to 3 are all above 115 min, specifically 119 to 145 min, and the fluid yield half-lives are relatively long, and the drilling compositions 1 to 3 have good stability at room temperature. Further, the addition of KCl aqueous solution does not cause a substantial decrease in the fluid yield half-lives of the drilling compositions 1 to 3, and instead, the fluid yield half-lives of some of the drilling compositions 1 to 3 increase. Specifically, compared with the fluid yield half-lives without adding KCl aqueous solution, the fluid yield half-lives of the drilling compositions 1 to 3 with 2% KCl aqueous solution added have a fluid yield half-life maintenance rate of 103.4%, 97.9% and 103.8% in sequence; the fluid yield half-lives of the drilling compositions 1 to 3 with 4% KCl aqueous solution added have a fluid yield half-life maintenance rate of 100.8%, 98.6% and 101.5% in sequence; the fluid yield half-lives of the drilling compositions 1 to 3 with 6% KCl aqueous solution added have a fluid yield half-life maintenance rate of 101.7%, 98.6% and 102.3% in sequence; and the fluid yield half-lives of the drilling compositions 1 to 3 with 8% KCl aqueous solution added have a fluid yield half-life maintenance rate of 96.6%, 95.9% and 97.7% in sequence. This shows that the drilling compositions 1 to 3 have good salt resistance.

[0099] ⅱ180℃ aging fluid yield half-life t1 / 2determination under different KCl addition conditions

[0100] C Take 1500 ml of the just prepared drilling composition 1 and pour it into an aging kettle, seal the kettle, and then put it into a high-temperature roller oven. After rolling at 180℃ for 16 to 24 h, take it out, naturally cool it to room temperature, pour it into a stirrer, and stir it at a speed of 12000 r / min for 2 min. Then, according to the determination method in step A, the fluid yield half-life t1 / 2of the drilling composition 1 without adding KCl aqueous solution after aging at 180℃ is determined.

[0101] Then, according to the determination method in step C, the fluid yield half-lives t1 / 2of the drilling compositions 2 and 3 after aging at 180℃ are determined.

[0102] D. Take 1500 mL of each of the four portions of freshly prepared drilling composition 1, and age them at 180 °C for 16 to 24 h according to the method in step C, cool to room temperature to obtain four portions of aged drilling composition 1; then pour each of the four portions of aged drilling composition 1 (1000 mL in volume) into a clean and dry 1500 ml graduated cylinder, respectively add 200 ml of KCl aqueous solution with a KCl mass fraction of 2%, 4%, 6%, 8%, and determine the liquid production half-life t1 / 2 of the 180 °C aged drilling composition 1 added with KCl aqueous solution with a KCl mass fraction of 2%, 4%, 6%, 8% according to the determination method in step A;

[0103] Then determine the liquid production half-life t1 / 2 of the 180 °C aged drilling composition 2, 3 added with KCl aqueous solution with a KCl mass fraction of 2%, 4%, 6%, 8% according to the determination method in step D;

[0104] The determination results are shown in Table 2.

[0105] Table 2. Liquid production half-life of drilling composition after aging at 180 °C

[0106]

[0107] As can be seen from Table 2, without adding KCl aqueous solution, the liquid production half-life of drilling compositions 1 to 3 after aging at 180 °C is not less than 110 min, specifically 110 to 140 min, and the liquid production half-life is relatively long, and the drilling compositions have good stability at high temperature of 180 °C. Further, the addition of KCl aqueous solution does not cause a substantial decrease in the liquid production half-life of drilling compositions 1 to 3 after aging at 180 °C, but on the contrary, the liquid production half-life of some of them increases. Specifically, after aging at 180 °C: the liquid production half-life of drilling compositions 1 to 3 added with 2% KCl aqueous solution compared with that without adding KCl aqueous solution has a liquid production half-life maintenance rate of 101.8%, 96.4% and 101.6%, respectively; the liquid production half-life of drilling compositions 1 to 3 added with 4% KCl aqueous solution compared with that without adding KCl aqueous solution has a liquid production half-life maintenance rate of 102.7%, 96.4% and 103.2%, respectively; the liquid production half-life of drilling compositions 1 to 3 added with 6% KCl aqueous solution compared with that without adding KCl aqueous solution has a liquid production half-life maintenance rate of 105.5%, 92.9% and 102.4%, respectively; the liquid production half-life of drilling compositions 1 to 3 added with 8% KCl aqueous solution compared with that without adding KCl aqueous solution has a liquid production half-life maintenance rate of 103.6%, 92.1% and 100%, respectively. This shows that drilling compositions 1 to 3 also have good salt resistance at high temperature of 180 °C.

[0108] In addition, in combination with the experimental conditions of i and ii, and by comparing the data in Table 1 and Table 2, it can be seen that for any drilling composition, under the condition of adding or not adding KCl aqueous solution: the liquid production half-life of the drilling composition without adding KCl aqueous solution after aging at 180℃ is maintained at more than 90% compared with the liquid production half-life at room temperature; the liquid production half-life of the drilling composition with the same formula and adding the same mass fraction of KCl aqueous solution after aging at 180℃ is also maintained at more than 90% compared with the liquid production half-life at room temperature, which also proves that the drilling composition provided by the present application has good stability and salt resistance at high temperature of 180℃.

[0109] Test Example 2 - Evaluation of reservoir protection performance of drilling composition

[0110] The reservoir protection performance of the drilling composition was evaluated according to the provisions of SY / T 6540-2002 "Laboratory Evaluation Method for Damage to Oil Reservoirs by Drilling Fluids and Completion Fluids". The average permeability Ko before the core was damaged by the drilling composition and the average permeability Kod after the damage were determined, and the recovery value Rd was calculated according to Formula 1.

[0111] Rd = Kod / Ko x 100% Formula 1

[0112] The evaluation results of the reservoir protection performance are shown in Table 3.

[0113] Table 3. Reservoir protection performance of drilling composition

[0114] Composition for drilling well Recovery value Rd / % Composition for drilling well 1 93 Composition for drilling well 2 88 Composition for drilling well 2 95

[0115] As can be seen from Table 3, the average permeability recovery value Rd of the core corresponding to the drilling compositions 1 to 3 is more than 85%, which has good reservoir protection performance when used as oil-based drilling fluid, and overcomes the shortcomings of the conventional oil-based drilling fluid in damaging the reservoir in the prior art.

[0116] Test Example 3 - Determination of biodegradability of drilling composition

[0117] The biodegradability of the drilling compositions 1 to 3 was determined by using an active biological sensor method.

[0118] Specifically, the drilling composition and air are introduced into the flow tank at a certain flow rate to contact the microbial sensor, when the diffusion rate of the dissolved sublimation-degradable organic matter in the drilling composition reaches a constant value by the bacterial membrane, the oxygen mass diffused onto the surface of the oxygen electrode also reaches a constant value and a constant current is generated, since the difference between the current and the biodegradable organic matter in the drilling composition has a quantitative relationship with the reduction of oxygen, the biochemical oxygen demand of the drilling composition can be calculated. Usually, the BOD5 standard sample (BOD5 value is 5.0 mg / L) is used for comparison to convert the BOD5 value of the drilling composition, which represents the biodegradability of the drilling composition.

[0119] The biodegradability determination results are shown in Table 4.

[0120] Table 4. Biodegradability of the drilling composition

[0121] Composition for drilling well BOD5 value Composition for drilling well 1 84％ Composition for drilling well 2 89％ Composition for drilling well 3 86％

[0122] Table 4 shows that the BOD5 value of the drilling composition is 84% to 89% of the BOD5 value of the BOD5 standard sample, the degree of biodegradability is high, and the drilling composition has good biodegradability and belongs to the degradable oil-based drilling fluid, which is more friendly to the environment.

[0123] Although the present application has been described with reference to specific embodiments, it is understood that various changes can be made without departing from the true spirit and scope of the application. In addition, various changes can be made to the subject matter, spirit and scope of the application to adapt it to specific situations, materials, compositions of matter and methods. All such changes are intended to be included within the scope of the claims of the present application.

Claims

1. A drilling composition comprising a surfactant, a foam stabilizing viscosifier, a vegetable oil and modified nano-silica; the surfactant is used in an amount of 0.15 to 0.4 wt%, the foam stabilizing viscosifier is used in an amount of 0.25 to 0.45 wt%, and the modified nano-silica is used in an amount of 0.35 to 0.65 wt%, based on 100% by mass of the vegetable oil; the foam stabilizing viscosifier is a polycondensation product of apricot kernel gum and polyaspartic acid; the mass ratio of the apricot kernel gum to the polyaspartic acid is 1:4.1; the weight average molecular weight of the polyaspartic acid is 1000 to 5000.

2. The drilling composition of claim 1, wherein, the surfactant has a structural formula as shown in Formula I: Formula I; wherein n is 1 to 5, R is a C5to C 18 alkyl group.

3. The drilling composition of claim 1, wherein, the vegetable oil is modified white oil.

4. The drilling composition of claim 3, wherein, the modified white oil is palmitate-modified white oil.

5. The drilling composition of any one of claims 1 to 4, wherein, the modified nano-silica is nano-silica modified by a silane coupling agent.

6. The drilling composition of claim 5, wherein, the silane coupling agent is KH-550. 7.Use of the drilling composition according to any one of claims 1 to 6 as an oil-based drilling fluid.

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