An anti-collapse drilling fluid and its preparation method

Abstract

The present invention discloses an anti-collapse drilling fluid and a preparation method thereof, relating to the technical field of drilling fluids. An anti-collapse drilling fluid comprises raw materials in the following parts by weight: deionized water: 100 parts, bentonite: 3 - 5 parts, filtration reducer: 5 - 8 parts, flow pattern regulator: 0.5 - 2 parts, modified plugging agent: 15 - 20 parts, modified emulsifier: 3 - 5 parts, weighting agent: 25 - 30 parts; in the present invention, modified nano-silica is generated through the reaction of nano-silica, γ-methacryloxypropyltrimethoxysilane, and N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide; the modified nano-silica and N-isopropylacrylamide, N,N'-methylenebisacrylamide are used to generate a modified plugging agent. The drilling fluid prepared by the present invention has good plugging performance.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling fluids, and particularly relates to an anti-collapse drilling fluid and a preparation method thereof. Background Art

[0002] During the drilling process of oil and natural gas, drilling fluids play a crucial role. They can not only carry cuttings, cool the drill bit, but also stabilize the wellbore and prevent accidents such as well collapse. With the continuous development of drilling technologies and the emergence of increasingly complex formations, the performance requirements for drilling fluids are also getting higher and higher, among which the anti-collapse performance is one of the key indicators.

[0003] Currently, there are some problems in the practical application of anti-collapse drilling fluids. Firstly, different formation conditions have different requirements for the anti-collapse performance of drilling fluids. For example, in special formations such as fractured formations and carbonate rock formations, the drilling fluid needs to have stronger inhibition and plugging properties to prevent wellbore collapse. However, the existing anti-collapse drilling fluid formulations often have limitations when adapting to different formations and are difficult to meet the anti-collapse requirements of all complex formations. Secondly, in harsh environments such as high temperature and high pressure, the performance of the drilling fluid is prone to change, resulting in a decline in the anti-collapse effect, which is particularly prominent in deep and ultra-deep drilling. In addition, the increasingly strict environmental requirements also pose new challenges to the composition of anti-collapse drilling fluids. Some traditional anti-collapse agents may contain substances that are not friendly to the environment, and more environmentally friendly alternatives need to be found.

[0004] Chinese Patent No. CN113637464A discloses an anti-collapse drilling fluid, its preparation method and application. The anti-collapse drilling fluid contains the following components in parts by weight: 1000 parts by weight of water, 15 - 40 parts by weight of drilling fluid bentonite, 5 - 35 parts by weight of micro-nano plugging agent, 20 - 70 parts by weight of temperature-sensitive plugging anti-collapse agent, 15 - 30 parts by weight of graphene hydrogel, and 0 - 1600 parts by weight of inert weighting agent. The high-temperature plugging performance of the drilling fluid prepared by this method needs to be further improved. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an anti-collapse drilling fluid and a preparation method thereof.

[0006] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0007] An anti-collapse drilling fluid, comprising the following raw materials in parts by weight:

[0008] Deionized water: 100 parts, bentonite: 3 - 5 parts, filtration reducer: 5 - 8 parts, flow pattern regulator: 0.5 - 2 parts, modified plugging agent: 15 - 20 parts, modified emulsifier: 3 - 5 parts, weighting agent: 25 - 30 parts;

[0009] The modified plugging agent is prepared by the following method:

[0010] S1: Nano-silica, γ-methacryloxypropyltrimethoxysilane, and N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide react to form modified nano-silica;

[0011] S2: The modified nano-silica reacts with N-isopropylacrylamide and N,N'-methylenebisacrylamide under the catalysis of ammonium persulfate to form the modified plugging agent.

[0012] In step S1, the feeding mass ratio of the nano-silica, γ-methacryloxypropyltrimethoxysilane, and N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide is 100:(20 - 25):(30 - 40).

[0013] In step S2, the feeding mass ratio of the modified nano-silica, N-isopropylacrylamide, and N,N'-methylenebisacrylamide is (18 - 20):4:(1 - 2).

[0014] The modified emulsifier is prepared by the following method:

[0015] A1: Nano-silica reacts with γ-glycidoxypropyltrimethoxysilane to form silane-modified nano-silica;

[0016] A2: The silane-modified nano-silica reacts with 3-amino-5-carboxyphenylboronic acid to form boric acid-modified nano-silica;

[0017] A3: The boric acid-modified nano-silica reacts with methoxypolyethylene glycol amine under the action of EDC to form polyethylene glycol-modified nano-silica;

[0018] A4: The polyethylene glycol-modified nano-silica reacts with 1,2-dodecanediol to form the modified emulsifier.

[0019] In step A1, the feeding mass ratio of the nano-silica and γ-glycidoxypropyltrimethoxysilane is (10 - 12):1.

[0020] In step A2, the feeding mass ratio of the silane-modified nano-silica and 3-amino-5-carboxyphenylboronic acid is 10:(0.6 - 1).

[0021] In step A3, the feeding mass ratio of the boric acid-modified nano-silica and methoxypolyethylene glycol amine is 10:(2 - 3).

[0022] In step A4, the feeding mass ratio of the polyethylene glycol-modified nano-silica to 1,2-dodecanediol is 10:(1-1.2).

[0023] The filtrate reducer is carboxymethyl cellulose; the flow pattern regulator is polyacrylamide; the weighting agent is barite powder.

[0024] A preparation method of an anti-collapse drilling fluid includes the following steps:

[0025] (1) Weigh by weight: deionized water: 100 parts, bentonite: 3-5 parts, filtrate reducer: 5-8 parts, flow pattern regulator: 0.5-2 parts, modified plugging agent: 15-20 parts, modified emulsifier: 3-5 parts, weighting agent: 25-30 parts;

[0026] (2) Add deionized water and bentonite to a container in sequence. After stirring for 15-25 min, stop stirring and carry out closed curing for 24 h to obtain pre-hydrated bentonite slurry; add the filtrate reducer, flow pattern regulator, modified plugging agent, and modified emulsifier to the pre-hydrated bentonite slurry in the above proportions in sequence, stir at high speed for 50-70 min, and finally add the weighting agent and stir evenly to obtain the anti-collapse drilling fluid.

[0027] Due to the adoption of the above technical solutions, the beneficial effects of the present invention include:

[0028] (1) In the present invention, the modified nano-silica is obtained by the reaction of the hydroxyl groups on the surface of nano-silica with the siloxy groups in γ-methacryloxypropyltrimethoxysilane and N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide; the modified nano-silica, N-isopropylacrylamide, and N,N'-methylenebisacrylamide generate a modified plugging agent under the catalysis of ammonium persulfate.

[0029] (2) The modified plugging agent prepared by the present invention forms a composite material with a three-dimensional network structure by introducing fluorocarbon chains on the surface of nano-silica and then reacting with N-isopropylacrylamide and N,N'-methylenebisacrylamide, and can form a dense and stable plugging layer in the drilling fluid, significantly improving the plugging performance.

[0030] (3) The modified emulsifier prepared in the present invention reacts through the silanol groups in nano-silica with Si-O- in γ-glycidoxypropyltrimethoxysilane to generate silane-modified nano-silica; then the epoxy groups in the silane-modified nano-silica react with the amino groups in 3-amino-5-carboxyphenylboric acid to generate boric acid-modified nano-silica; the carboxyl groups in the boric acid-modified nano-silica react with the amino groups in methoxypolyethylene glycol amine under the action of EDC to generate polyethylene glycol-modified nano-silica; the boric acid groups in the polyethylene glycol-modified nano-silica react with the hydroxyl groups in 1,2-dodecanediol to generate the modified emulsifier.

[0031] (4) Through the synergistic effect of long-chain borate esters, polyethylene glycol segments and silane-modified nano-silica, the modified emulsifier prepared in the present invention can significantly improve the emulsification stability, rheological properties, filtration control properties and temperature and salt tolerance properties of drilling fluids, thus meeting the high-performance requirements of drilling fluids under complex geological conditions. Specific Embodiments

[0032] The following is further illustrated with reference to embodiments, but the present invention is not limited to these embodiments.

[0033] Example 1 Preparation of Modified Plugging Agent:

[0034] S1: Add 1000 ml of a mixed solution of ethanol and water (ethanol / water (V / V) = 9:1) and 100 g of nano-silica to the reactor, ultrasonically vibrate for 20 min, then add 20 g of γ-methacryloxypropyltrimethoxysilane, 30 g of N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide and 60 ml of triethylamine, react at 70 °C for 6 h, then cool to room temperature, centrifuge and filter, wash successively with 300 ml of absolute ethanol and 300 ml of 50 wt% ethanol aqueous solution, and then vacuum dry at 80 °C for 10 h to obtain modified nano-silica;

[0035] S2: Under nitrogen protection, add 1000 ml of DMF, 180 g of modified nano-silica, 40 g of N-isopropylacrylamide and 10 g of N,N'-methylenebisacrylamide to the reactor, stir and mix evenly, then add 20 ml of 20 wt% ammonium persulfate solution, heat up to 80 °C and react for 15 h, then let it stand for precipitation, centrifuge and filter, then add 500 ml of ether, stir for 10 min, let it stand to precipitate, filter by suction, collect the precipitate, and vacuum dry at 70 °C for 4 h to obtain the modified plugging agent.

[0036] Example 2 Preparation of Modified Plugging Agent:

[0037] S1: Add 1000 ml of a mixed solution of ethanol and water (ethanol / water (V / V) = 9:1) and 100 g of nano-silica into the reactor, ultrasonically vibrate for 20 min, then add 25 g of γ-methacryloxypropyltrimethoxysilane, 35 g of N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide, and 60 ml of triethylamine. After reacting at 70 °C for 6 h, cool to room temperature, centrifuge and filter, wash successively with 300 ml of absolute ethanol and 300 ml of 50 wt% ethanol aqueous solution, and then vacuum dry at 80 °C for 10 h to obtain modified nano-silica;

[0038] S2: Under nitrogen protection, add 1000 ml of DMF, 190 g of modified nano-silica, 40 g of N-isopropylacrylamide, and 15 g of N,N'-methylenebisacrylamide into the reactor, stir and mix evenly, then add 20 ml of 25 wt% ammonium persulfate solution, heat up to 80 °C and react for 15 h. Then, let it stand for precipitation, centrifuge and filter, then add 500 ml of ether, stir for 10 min, let it stand to precipitate, filter by suction, collect the precipitate, and vacuum dry at 70 °C for 4 h to obtain the modified plugging agent.

[0039] Example 3 Preparation of modified plugging agent:

[0040] S1: Add 1000 ml of a mixed solution of ethanol and water (ethanol / water (V / V) = 9:1) and 100 g of nano-silica into the reactor, ultrasonically vibrate for 20 min, then add 25 g of γ-methacryloxypropyltrimethoxysilane, 40 g of N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide, and 60 ml of triethylamine. After reacting at 70 °C for 6 h, cool to room temperature, centrifuge and filter, wash successively with 300 ml of absolute ethanol and 300 ml of 50 wt% ethanol aqueous solution, and then vacuum dry at 80 °C for 10 h to obtain modified nano-silica;

[0041] S2: Under nitrogen protection, add 1000 ml of DMF, 200 g of modified nano-silica, 40 g of N-isopropylacrylamide, and 20 g of N,N'-methylenebisacrylamide into the reactor, stir and mix evenly, then add 20 ml of 25 wt% ammonium persulfate solution, heat up to 80 °C and react for 15 h. Then, let it stand for precipitation, centrifuge and filter, then add 500 ml of ether, stir for 10 min, let it stand to precipitate, filter by suction, collect the precipitate, and vacuum dry at 70 °C for 4 h to obtain the modified plugging agent.

[0042] Example 4 Preparation of modified emulsifier:

[0043] A1: Add 500 ml of a mixed solution of ethanol and water (ethanol / water (V / V) = 9:1) and 100 g of nano-silica into a reactor, ultrasonically vibrate for 20 min, then add 10 g of γ-glycidoxypropyltrimethoxysilane and 20 ml of triethylamine. After reacting at 70 °C for 6 h, cool to room temperature, centrifuge and filter, wash successively with 100 ml of absolute ethanol and 100 ml of 50 wt% ethanol aqueous solution, and then vacuum dry at 80 °C for 10 h to obtain silane-modified nano-silica;

[0044] A2: Under nitrogen protection, add 500 ml of absolute methanol, 100 g of silane-modified nano-silica and 20 ml of triethylamine into a reactor, stir and mix evenly, then add 6 g of 3-amino-5-carboxyphenylboronic acid in batches (2 g per batch, batch interval 5 min). After refluxing for 20 h, cool to room temperature, and carry out vacuum distillation at 50 °C for 1 h to obtain boric acid-modified nano-silica;

[0045] A3: Under ice bath, add 600 ml of deionized water, 100 g of boric acid-modified nano-silica and 15 g of EDC into a reactor, stir and mix evenly, then add 20 g of methoxypolyethylene glycol amine, warm to room temperature, react for 4 h, add 200 ml of ice water, stir for 5 min, filter, wash with 200 ml of ethyl acetate, and vacuum dry at 50 °C for 10 h to obtain polyethylene glycol-modified nano-silica;

[0046] A4: Add 400 g of toluene, 100 g of polyethylene glycol-modified nano-silica, 10 g of 1,2-dodecanediol and 2 g of p-toluenesulfonic acid into a reactor, stir and mix evenly, heat to 100 °C, react for 4 h (remove the generated water with a water separator during the reaction), then carry out vacuum filtration, vacuum distill at 60 °C for 3 h, then add 150 ml of cold ether to precipitate, filter, and vacuum dry at 50 °C for 8 h to obtain a modified emulsifier.

[0047] Example 5 Preparation of the modified emulsifier:

[0048] A1: Add 500 ml of a mixed solution of ethanol and water (ethanol / water (V / V) = 9:1) and 110 g of nano-silica into a reactor, ultrasonically vibrate for 20 min, then add 10 g of γ-glycidoxypropyltrimethoxysilane and 20 ml of triethylamine. After reacting at 70 °C for 6 h, cool to room temperature, centrifuge and filter, wash successively with 100 ml of absolute ethanol and 100 ml of 50 wt% ethanol aqueous solution, and then vacuum dry at 80 °C for 10 h to obtain silane-modified nano-silica;

[0049] A2: Under nitrogen protection, add 500 ml of anhydrous methanol, 100 g of silane-modified nano-silica, and 20 ml of triethylamine into the reactor, stir and mix evenly, then add 8 g of 3-amino-5-carboxylphenylboronic acid in batches (2 g per batch, batch interval 5 min). After refluxing for 20 h, cool to room temperature and carry out vacuum distillation at 50 °C for 1 h to obtain boric acid-modified nano-silica;

[0050] A3: Under ice bath, add 600 ml of deionized water, 100 g of boric acid-modified nano-silica, and 15 g of EDC into the reactor, stir and mix evenly, then add 25 g of methoxypolyethylene glycol amine, raise the temperature to room temperature, react for 5 h, add 200 ml of ice water, stir for 5 min, filter, wash with 200 ml of ethyl acetate, and carry out vacuum drying at 50 °C for 10 h to obtain polyethylene glycol-modified nano-silica;

[0051] A4: Add 400 g of toluene, 100 g of polyethylene glycol-modified nano-silica, 11 g of 1,2-dodecanediol, and 2 g of p-toluenesulfonic acid into the reactor, stir and mix evenly, heat up to 100 °C, react for 4 h (remove the generated water with a water separator during the reaction), then carry out vacuum filtration, carry out vacuum distillation at 60 °C for 3 h, then add 150 ml of cold ether to precipitate, filter, and carry out vacuum drying at 50 °C for 8 h to obtain the modified emulsifier.

[0052] Example 6 Preparation of the modified emulsifier:

[0053] A1: Add a mixture of 500 ml of ethanol and water (ethanol / water (V / V) = 9:1) and 120 g of nano-silica into the reactor, ultrasonically vibrate for 20 min, then add 10 g of γ-glycidoxypropyltrimethoxysilane and 20 ml of triethylamine, react at 70 °C for 6 h, then cool to room temperature, carry out centrifugal filtration, wash successively with 100 ml of anhydrous ethanol and 100 ml of 50 wt% ethanol aqueous solution, and then carry out vacuum drying at 80 °C for 10 h to obtain silane-modified nano-silica;

[0054] A2: Under nitrogen protection, add 500 ml of anhydrous methanol, 100 g of silane-modified nano-silica, and 20 ml of triethylamine into the reactor, stir and mix evenly, then add 10 g of 3-amino-5-carboxylphenylboronic acid in batches (2 g per batch, batch interval 5 min). After refluxing for 20 h, cool to room temperature and carry out vacuum distillation at 50 °C for 1 h to obtain boric acid-modified nano-silica;

[0055] A3: Under an ice bath, add 600 ml of deionized water, 100 g of boric acid-modified nano-silica, and 15 g of EDC into a reactor, stir and mix evenly, then add 30 g of methoxypolyethylene glycol amine, raise the temperature to room temperature, react for 5 h, add 200 ml of ice water, stir for 5 min, filter, wash with 200 ml of ethyl acetate, and dry in vacuum at 50 °C for 10 h to obtain polyethylene glycol-modified nano-silica;

[0056] A4: Add 400 g of toluene, 100 g of polyethylene glycol-modified nano-silica, 12 g of 1,2-dodecanediol, and 2 g of p-toluenesulfonic acid into a reactor, stir and mix evenly, raise the temperature to 100 °C, react for 4 h (remove the generated water with a water separator during the reaction), then filter under reduced pressure, distill under reduced pressure at 60 °C for 3 h, then add 150 ml of cold ether to precipitate, filter, and dry in vacuum at 50 °C for 8 h to obtain a modified emulsifier.

[0057] Example 7 Preparation of anti-collapse drilling fluid:

[0058] (1) Weigh: 1000 g of deionized water, 30 g of bentonite, 50 g of filtration reducer (carboxymethyl cellulose), 5 g of flow pattern regulator (polyacrylamide), 150 g of modified plugging agent (prepared in Example 1), 30 g of modified emulsifier (prepared in Example 4), 250 g of weighting agent (barite powder);

[0059] (2) Add deionized water and bentonite into a container in sequence, stir for 15 min, then stop stirring, and close for curing for 24 h to obtain pre-hydrated bentonite slurry; add the filtration reducer, flow pattern regulator, modified plugging agent, and modified emulsifier into the pre-hydrated bentonite slurry in the above proportions in sequence, stir at a high speed for 50 min, with a rotation speed of 8000 r / min, and finally add the weighting agent, stir evenly to obtain the anti-collapse drilling fluid.

[0060] Example 8 Preparation of anti-collapse drilling fluid:

[0061] (1) Weigh: 1000 g of deionized water, 40 g of bentonite, 60 g of filtration reducer (carboxymethyl cellulose), 10 g of flow pattern regulator (polyacrylamide), 180 g of modified plugging agent (prepared in Example 2), 40 g of modified emulsifier (prepared in Example 5), 280 g of weighting agent (barite powder);

[0062] (2) Add deionized water and bentonite into a container in sequence, stir for 20 min, then stop stirring, and close for curing for 24 h to obtain pre-hydrated bentonite slurry; add the filtration reducer, flow pattern regulator, modified plugging agent, and modified emulsifier into the pre-hydrated bentonite slurry in the above proportions in sequence, stir at a high speed for 60 min, with a rotation speed of 8000 r / min, and finally add the weighting agent, stir evenly to obtain the anti-collapse drilling fluid.

[0063] Example 9 Preparation of anti-collapse drilling fluid:

[0064] (1) Weigh: 1000 g of deionized water, 50 g of bentonite, 80 g of filtrate reducer (carboxymethyl cellulose), 20 g of flow pattern regulator (polyacrylamide), 200 g of modified plugging agent (prepared in Example 3), 50 g of modified emulsifier (prepared in Example 6), and 300 g of weighting agent (barite powder);

[0065] (2) Add deionized water and bentonite to the container in sequence. After stirring for 25 min, stop stirring and carry out airtight curing for 24 h to obtain pre-hydrated bentonite slurry. Add the filtrate reducer, flow pattern regulator, modified plugging agent, and modified emulsifier to the pre-hydrated bentonite slurry in the above proportions in sequence, and stir at a high speed for 70 min with a rotation speed of 8000 r / min. Finally, add the weighting agent and stir evenly to obtain the anti-collapse drilling fluid.

[0066] Comparative Example 1

[0067] A method for preparing an anti-collapse drilling fluid is basically the same as that in Example 8, except that the modified plugging agent is replaced with a modified plugging agent prepared by the following method with the same weight:

[0068] The preparation method of the modified plugging agent in this comparative example is basically the same as that in Example 2, except that the N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide added in step S1 is replaced with 1H,1H,2H,2H-perfluorodecyltriethoxysilane with the same weight.

[0069] Comparative Example 2

[0070] A method for preparing an anti-collapse drilling fluid is basically the same as that in Example 8, except that the modified plugging agent is replaced with a modified plugging agent prepared by the following method with the same weight:

[0071] The preparation method of the modified plugging agent in this comparative example is basically the same as that in Example 2, except that the N,N'-methylenebisacrylamide added in step S2 is replaced with N-(hydroxymethyl)acrylamide with the same weight.

[0072] Comparative Example 3

[0073] A method for preparing an anti-collapse drilling fluid is basically the same as that in Example 8, except that the modified plugging agent is replaced with a modified plugging agent prepared by the following method with the same weight:

[0074] Under nitrogen protection, 1000 ml of DMF, 190 g of γ-methacryloyloxypropyltrimethoxysilane, 40 g of N-isopropylacrylamide, and 15 g of N,N'-methylenebisacrylamide were added to the reactor, stirred and mixed evenly, then 20 ml of 25 wt% ammonium persulfate solution was added, and the temperature was raised to 80 °C. After reacting for 15 h, it was allowed to stand for precipitation, centrifuged and filtered, then 500 ml of ether was added, stirred for 10 min, allowed to stand for precipitation, filtered by suction, the precipitate was collected, and vacuum dried at 70 °C for 4 h to obtain the modified plugging agent.

[0075] Comparative Example 4

[0076] A method for preparing an anti-collapse drilling fluid is basically the same as that in Example 8, except that the modified emulsifier is replaced with a modified emulsifier prepared by the following method with the same weight:

[0077] The preparation method of the modified emulsifier in this comparative example is basically the same as that in Example 5, except that the methoxypolyethylene glycol amine added in step A3 is replaced with dodecylamine with the same weight.

[0078] Comparative Example 5

[0079] A method for preparing an anti-collapse drilling fluid is basically the same as that in Example 8, except that the modified emulsifier is replaced with a modified emulsifier prepared by the following method with the same weight:

[0080] The preparation method of the modified emulsifier in this comparative example is basically the same as that in Example 5, except that the 1,2-dodecanediol added in step A4 is replaced with 1,2-propanediol with the same weight.

[0081] Comparative Example 6

[0082] A method for preparing an anti-collapse drilling fluid is basically the same as that in Example 8, except that the modified emulsifier is replaced with a modified emulsifier prepared by the following method with the same weight:

[0083] The preparation method of the modified emulsifier is basically the same as that in Example 5, except that the 3-amino-5-carboxylphenylboronic acid added in step A2 is replaced with 4-aminobenzoic acid with the same weight.

[0084] Comparative Example 7

[0085] An anti-collapse drilling fluid prepared by using the raw materials and method in Example 3 of the patent with the publication number CN113637464A.

[0086] The raw materials used in the embodiments and comparative examples of this application are as follows: The bentonite model is Bentone 38; the barite powder has a particle size of 400 mesh and is produced by Shijiazhuang Mayue Building Materials Co., Ltd.; the nano-silica used in the embodiments and comparative examples of this application for preparing the modified emulsifier and the modified plugging agent is hydroxyl-modified nano-silica, with the model of As-200, purchased from Shenyang Chemical Industry Co., Ltd.; the M.W. of methoxypolyethylene glycol amine = 2000; the model of carboxymethyl cellulose is CMC-HVT, purchased from Hebei Yeyuan New Materials Co., Ltd.; the polyacrylamide is non-ionic, with a molecular weight of 3 million, purchased from Henan Jinghua New Materials Technology Co., Ltd.

[0087] The high-temperature and high-pressure filtration loss experiment test was carried out on the anti-collapse drilling fluids prepared in the examples and comparative examples. The experiment was carried out in accordance with GB / T 16783.1-2014 "Petroleum and natural gas industries - Drilling fluid field testing - Part 1: Water-based drilling fluids". The experimental conditions were 220 °C × 16 h, and the test results are shown in Table 1.

[0088] Table 1 Performance indicators of drilling fluids

[0089]

[0090] It can be seen from Table 1 that the high-temperature and high-pressure filtration loss of the anti-collapse drilling fluid prepared in this application is relatively low, indicating excellent plugging performance.

[0091] The modified plugging agent prepared by the present invention forms a composite material with a three-dimensional network structure by introducing fluorocarbon chains on the surface of nano-silica and then reacting with N-isopropylacrylamide and N,N'-methylenebisacrylamide. The three-dimensional network structure can effectively fill the micro-fractures and pores in the formation, and achieve multi-level plugging of pores with different sizes through the three-dimensional cross-linked structure formed after curing; compared with traditional rigid materials, this three-dimensional network has both flexibility and rigidity, which combines rigid inorganic particles (silica) with flexible polymers (obtained by polymerizing the double bonds of γ-methacryloxypropyltrimethoxysilane grafted onto the surface of nano-silica with N-isopropylacrylamide and N,N'-methylenebisacrylamide), forming an interpenetrating network structure with both high strength and deformation ability, thereby improving the comprehensive plugging efficiency. The plugging agent prepared in this application improves the temperature resistance of the material through an inorganic / organic composite structure, and can still maintain a stable three-dimensional cross-linked structure at high temperatures, avoiding the possibility of plugging failure caused by temperature changes. The strong hydrophobicity and low surface tension of the fluorinated groups in the modified plugging agent make the plugging agent easy to penetrate into micro-fractures and closely adhere to the rock surface, reducing the interface gap and the filtration loss; and the fluorinated group chain contains sulfonamide groups with strong polarity, which can form multiple interactions with the aqueous phase in the drilling fluid, the hydroxyl groups on the surface of nano-silica, and the polymer through hydrogen bonds or electrostatic interactions, thereby enhancing the interfacial adhesion. However, 1H,1H,2H,2H-perfluorodecyltriethoxysilane only contains perfluorinated chains and silyl groups, lacking polar groups (such as sulfonamide), resulting in a relatively reduced binding ability with nanoparticles or polymers, so the plugging performance of Comparative Example 1 is poor.

[0092] N,N'-methylenebisacrylamide is a bifunctional cross-linking agent, and two acrylamide groups can react with multiple polymer chains (such as N-isopropylacrylamide) simultaneously to form a high-strength three-dimensional cross-linked network; this three-dimensional cross-linked network can resist the compression and shear forces in the downhole high-pressure environment and can better maintain the structural integrity under dynamic stress. While N-(hydroxymethyl)acrylamide is a monofunctional monomer that cannot form intermolecular cross-linking and can only participate in linear polymerization reactions. Therefore, the plugging performance of Comparative Example 2 is poor.

[0093] The long-chain borate molecules and long-chain polyethylene glycol segments in the modified emulsifier prepared by the present invention can form a dense filtration control film on the contact surface between the drilling fluid and the formation. Its long-chain structure can block the tiny pores and fractures in the formation, preventing the water and solid particles in the drilling fluid from entering the formation, thereby reducing the filtration loss. However, 1,2-propanediol and dodecylamine have short molecular chains and are not easily blocked by the tiny pores and fractures in the formation, so their plugging performance is poor.

[0094] 3-Amino-5-carboxylphenylboronic acid contains a boronic acid group that can form dynamic reversible borate ester bonds. The breakage-recombination of the dynamic bonds can repair the microcracks in the sealing layer and maintain long-term sealing performance. 4-Aminobenzoic acid only contains amino and carboxyl groups and cannot form dynamic borate ester bonds, resulting in the loss of environmental responsiveness of the material and the inability to adaptively adjust the filtration behavior.

[0095] As described above, the above are only the preferred embodiments of the present invention and are not used to limit the present invention. However, for those of ordinary skill in the art, without departing from the scope of the technical solution of the present invention, any equivalent changes such as slight modifications, evolutions, and alterations made using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications, and evolutions made to the above embodiments based on the essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An anti-collapse drilling fluid, characterized in that: The invention comprises the following raw materials in parts by weight: Deionized water: 100 parts, bentonite: 3-5 parts, fluid loss reducer: 5-8 parts, flow pattern regulator: 0.5-2 parts, modified plugging agent: 15-20 parts, modified emulsifier: 3-5 parts, weighting agent: 25-30 parts; The modified plugging agent is prepared by the following method: S1: Nano-silica, γ-methacryloxypropyltrimethoxysilane, and N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide are reacted to generate modified nano-silica; S2: Modified nano-silica reacts with N-isopropylacrylamide and N,N'-methylenebisacrylamide under the catalysis of ammonium persulfate to generate modified plugging agent; In step S1, the mass ratio of the nano-silica, γ-methacryloxypropyltrimethoxysilane, and N-ethyl-N-[3-(trimethoxysilyl)propyl]-1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-pentadecafluoro-1-hexanesulfonamide is 100:(20-25):(30-40); In step S2, the mass ratio of the modified nano-silica, N-isopropylacrylamide, and N,N'-methylenebisacrylamide is (18-20):4:(1-2); The modified emulsifier is prepared by the following method: A1: Nano-silica reacts with γ-glycidyloxypropyltrimethoxysilane to generate silane-modified nano-silica; A2: Silane-modified nano-silica reacts with 3-amino-5-carboxyphenylboronic acid to generate boric acid-modified nano-silica; A3: Boric acid-modified nano-silica reacts with methoxypolyethylene glycol amine under the action of EDC to generate polyethylene glycol-modified nano-silica; A4: Polyethylene glycol-modified nano-silica reacts with 1,2-dodecanediol to generate a modified emulsifier; In step A1, the mass ratio of the nano-silica to γ-glycidyloxypropyltrimethoxysilane is (10-12):1; In step A2, the mass ratio of the silane-modified nano-silica to 3-amino-5-carboxyphenylboric acid is 10:(0.6-1); In step A3, the mass ratio of the boric acid-modified nano-silica to the methoxypolyethylene glycolamine is 10:(2-3); In step A4, the mass ratio of the polyethylene glycol-modified nano-silica to 1,2-dodecanediol is 10:(1-1.2); The fluid loss reducer is carboxymethyl cellulose; the flow pattern regulator is polyacrylamide; and the weighting agent is barite powder.

2. A method for preparing the anti-collapse drilling fluid according to claim 1, characterized in that: The following steps are involved: (1) Weigh by weight: deionized water: 100 parts, bentonite: 3-5 parts, fluid loss reducer: 5-8 parts, flow pattern regulator: 0.5-2 parts, modified plugging agent: 15-20 parts, modified emulsifier: 3-5 parts, weighting agent: 25-30 parts; (2) Deionized water and bentonite are added to the container in sequence, and after stirring for 15-25 minutes, stirring is stopped, and the mixture is sealed and cured for 24 hours to obtain a prehydrated bentonite slurry; a filtrate reducer, a flow pattern regulator, a modified plugging agent, and a modified emulsifier are added to the prehydrated bentonite slurry in the above proportions in sequence, and stirred at high speed for 50-70 minutes. Finally, a weighting agent is added, and the mixture is stirred evenly to obtain an anti-collapse drilling fluid.

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