High-temperature-resistant high-salt-resistant deformable strong-support plugging agent, preparation method thereof and drilling fluid

Abstract

The invention discloses a high-temperature-resistant and high-salt-resistant deformable strong-support plugging agent, a preparation method thereof and a drilling fluid. The high-temperature-resistant and high-salt-resistant deformable strong-support plugging agent is prepared from the following raw material components: 20 to 30 parts of styrene, 10 to 20 parts of maleic anhydride, 5 to 10 parts of diacetone acrylamide, 2 to 6 parts of lauryl methacrylate, 2 to 4 parts of a propping agent, 0.2 to 0.5 part of an emulsifier, 0.05 to 0.2 part of an initiator and 130 to 160 parts of water. The high-temperature-resistant and high-salt-resistant deformable strong-support plugging agent disclosed by the invention can play a good plugging role under high-temperature and high-salt conditions, has the characteristics of deformable self-adaptive crack filling and strong-support plugging, and can be applied to preparation of drilling fluids for deep wells and ultra-deep wells.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling fluids, and in particular relates to a high-temperature and high-salt resistant deformable strong support plugging agent and a preparation method thereof and a drilling fluid. Background Art

[0002] Drilling fluid is called "the blood of drilling". It is an indispensable core engineering technology for oil and gas exploration and development. It is a key technology to ensure safe and smooth drilling and protect oil and gas reservoirs. It is directly related to the success or failure of drilling and the production of oil and gas reservoirs. However, existing drilling fluid plugging agents fail in large numbers in the high temperature and high salt environment of deep formations, resulting in a serious decline in the performance of drilling fluids. Drilling fluids enter deep formations along microcracks and cracks, causing complex underground situations and accidents such as well wall collapse, leakage, drill bit sticking and reservoir damage, causing major economic losses and seriously restricting the progress of gas exploration and development. Generally, flexible organic materials have poor temperature and salt resistance; rigid materials such as silica and calcium carbonate have strong resistance to high temperature and high salt, but cannot effectively match the shape and size of pores and cracks in the formation, and the plugging effect is poor.

[0003] CN113292973A discloses a high temperature resistant silica grafted tertiary amine nano plugging agent, which can improve the plugging performance of drilling fluid at 150°C; CN113355061A discloses a soft outer and hard inner oil-based drilling fluid nano plugging agent, which has the ability to be variable and has a certain skeleton support function, and can adaptively select gaps of different sizes. The plugging agent can effectively improve the plugging performance of drilling fluid at 160°C; CN109439298A discloses a high temperature and calcium resistant water-based drilling fluid plugging agent for protecting oil and gas reservoirs, which can be used at 200°C and 1% CaCl 2 However, the above plugging agents do not show the plugging ability under higher temperature or with the addition of NaCl, and cannot meet the needs of high-temperature and high-salt drilling. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a high temperature and high salt resistant deformable strong support plugging agent, which can play a good plugging role under high temperature and high salt conditions.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a high-temperature, high-salt resistant, deformable, strong support plugging agent. The raw material components of the high-temperature, high-salt resistant, deformable, strong support plugging agent include 20-30 parts of styrene, 10-20 parts of maleic anhydride, 5-10 parts of diacetone acrylamide, 2-6 parts of lauryl methacrylate, 2-4 parts of proppant, 0.2-0.5 parts of emulsifier, 0.05-0.2 parts of initiator, and 130-160 parts of water by weight.

[0006] In some embodiments, the raw material components of the high temperature and high salt resistance deformable strong support plugging agent include 25-30 parts of styrene, 10-15 parts of maleic anhydride, 8-10 parts of diacetone acrylamide, 5-6 parts of lauryl methacrylate, 3-4 parts of proppant, 0.3-0.4 parts of emulsifier, 0.15-0.2 parts of initiator, and 130-160 parts of water.

[0007] In some embodiments, the raw material composition of the high temperature and high salt resistance deformable strong support plugging agent includes 25 parts of styrene, 15 parts of maleic anhydride, 8 parts of diacetone acrylamide, 5 parts of lauryl methacrylate, 3 parts of proppant, 0.3 parts of emulsifier, 0.15 parts of initiator, and 150 parts of water.

[0008] In some embodiments, the proppant is ultrafine silica and / or ultrafine calcium carbonate.

[0009] In some embodiments, the particle size of the proppant is 50-500 nm.

[0010] In some embodiments, the emulsifier is one or a combination of two or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and polyoxyethylene dodecylphenol ether. As a preferred embodiment, the emulsifier is sodium dodecylbenzene sulfonate.

[0011] In some embodiments, the initiator is one or more of potassium persulfate, ammonium persulfate, and sodium persulfate.

[0012] In some embodiments, the high temperature and high salt resistance deformable strong support plugging agent is a core-shell structure, the shell of the core-shell structure is a copolymer of styrene and maleic anhydride, and the core of the core-shell structure is a proppant.

[0013] The second aspect of the present invention provides a method for preparing the high temperature and high salt resistance deformable strong support plugging agent according to the first aspect of the present invention, which comprises:

[0014] 1) mixing maleic anhydride, diacetone acrylamide and water, adding an emulsifier, and stirring to obtain a first mixture;

[0015] 2) adding proppant to the first mixture in 2), stirring and dispersing, and ultrasonically dispersing to obtain a second mixture;

[0016] 3) Weighing styrene and lauryl methacrylate, mixing, adding the second mixture described in 2), and shearing and emulsifying in a shear emulsifier to obtain an emulsified mixed solution;

[0017] 4) stirring the emulsified mixed solution in 3), deoxygenating, heating, adding an initiator, and passing nitrogen gas to react;

[0018] 5) After the reaction is completed, stirring is performed, and heating is stopped. After the temperature drops, the high temperature resistant and high salt resistant deformable strong support plugging agent is obtained.

[0019] In some embodiments, the stirring and dispersing time in step 2) is 10-30 min, and the ultrasonic dispersing time is 20-40 min. As a preferred embodiment, the stirring and dispersing time in step 2) is 10 min, and the ultrasonic dispersing time is 30 min.

[0020] In some embodiments, the shear emulsification conditions are: shear emulsification at 8000-10000 r / min for 10-20 minutes, preferably shear emulsification for 15 minutes.

[0021] In some embodiments, the deoxygenation in step 4) is performed using nitrogen for more than 30 minutes, preferably 30 minutes.

[0022] In some embodiments, the stirring condition in step 4) is 200-500 r / min, preferably 300 r / min.

[0023] In some embodiments, the temperature increase in step 4) is to 65-75°C, preferably 70°C.

[0024] In some embodiments, the nitrogen-passing reaction time in step 4) is 6-8 hours, preferably 7 hours.

[0025] In some embodiments, the temperature drop in step 5) is to 30-40°C.

[0026] The third aspect of the present invention provides the use of the high temperature and high salt resistance deformable strong support plugging agent described in the first aspect of the present invention in the preparation of drilling fluid.

[0027] In some embodiments, the drilling fluid is a deep well water-based drilling fluid.

[0028] In some embodiments, the drilling fluid is a drilling fluid for high temperature and high salt conditions.

[0029] In some embodiments, the high temperature and high salt conditions are: 200° C. and above, and a salt content of more than 10%.

[0030] In some embodiments, the high temperature is 240° C., and the high salt is 15% NaCl.

[0031] In some embodiments, the mass percentage of the high temperature and high salt resistance deformable strong support plugging agent in the drilling fluid is 2%-5%.

[0032] The beneficial effects of the present invention are as follows:

[0033] 1. The high temperature and high salt resistant deformable strong support plugging agent of the present invention is an organic-inorganic composite material microsphere dispersion emulsion made from styrene, maleic anhydride, diacetone acrylamide, lauryl methacrylate, proppant and emulsifier as raw materials. It can be well dispersed in the drilling fluid under ultra-high temperature and high salt conditions and effectively plug the cracks.

[0034] 2. The outer part of the high temperature and high salt resistant deformable strong support plugging agent of the present invention is a flexible polymer soft shell, which can realize adaptive plugging of formation cracks through deformation; the inner core is a temperature and salt resistant inert rigid proppant, which serves as a supporting skeleton to increase the strength of the plugging agent. Under the action of pressure difference, the plugging agent can not only reduce the amount of drilling fluid loss, but also fill and deposit around the well wall to form an effective pressure-bearing plugging layer, thereby preventing pressure transmission and filtrate intrusion, thereby filling cracks and reducing the drilling fluid loss channel.

[0035] 3. The main body of the polymer soft shell of the outer layer of the plugging agent is a copolymer of styrene and maleic anhydride. The reaction is rapid during synthesis, the product structure is dense, the covalent bond energy in the molecule is large, the molecular steric hindrance is large, and the molecular structure determines its good temperature and salt resistance. Therefore, the polymer can play a good plugging role under high temperature and high salt conditions.

[0036] The outer polymer shell can deform into the crack to form an accumulation, and then the rigid core and diacetone acrylamide water are released to provide rigid support, effectively supporting and sealing the crack.

[0037] 4. The introduction of diacetone acrylamide into the polymer makes the plugging agent "water-breathable". At room temperature, the plugging agent can absorb water and swell in the drilling fluid to improve its deformation capacity. After entering the high-temperature and high-pressure cracks, the water absorbed by the plugging agent can be released, thereby improving the rigidity of the plugging agent, supporting and plugging the cracks, and further improving the plugging effect.

[0038] 5. The plugging agent of the present invention is a high temperature and high salt resistant deformable strong support plugging agent, which can play a good plugging role at an ultra-high temperature of 240°C and 15% NaCl, and has the advantages of high strength and strong adaptability, and is expected to provide support for drilling in ultra-high temperature and high salt formations. DETAILED DESCRIPTION

[0039] The specific embodiments of the present invention are further described below. According to the following examples, the present invention can be better understood. However, it is easy for those skilled in the art to understand that the specific material ratios, process conditions and results described in the embodiments are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0040] Preparation Example 1

[0041] This preparation example provides a high temperature and high salt resistance deformable strong support plugging agent, which is prepared by the following steps:

[0042] 1) Weigh 15 parts of maleic anhydride and 8 parts of diacetone acrylamide, add them into a flask containing 150 parts of water, stir until fully dispersed, and then add 0.3 parts of emulsifier sodium dodecylbenzene sulfonate, stir until fully dispersed.

[0043] 2) Add 3 parts of proppant nano-silica (median particle size of 50 nm) to the above liquid, stir and disperse for 10 minutes, and then disperse by ultrasonic for 30 minutes.

[0044] 3) Weigh 25 parts of styrene and 5 parts of lauryl methacrylate, stir until fully mixed, add to the liquid in 2), and shear emulsify for 15 minutes at 8000 r / min in a shear emulsifier.

[0045] 4) Add the above liquid into the flask, keep stirring at 300r / min, and deoxygenate with nitrogen for 30 minutes.

[0046] 5) Raise the temperature to 70°C, add 0.15 parts of initiator potassium persulfate, and react for 7 hours under nitrogen.

[0047] 6) After the reaction is completed, keep stirring and stop heating. After the temperature drops to 30°C, pour the contents out of the flask to obtain the high temperature and high salt resistant deformable strong support plugging agent A1.

[0048] Preparation Example 2

[0049] This preparation example provides a high temperature and high salt resistance deformable strong support plugging agent, which is prepared by the following steps:

[0050] 1) Weigh 10 parts of maleic anhydride and 10 parts of diacetone acrylamide, add them into a flask containing 150 parts of water, stir until fully dispersed, and then add 0.4 parts of emulsifier sodium lauryl sulfate, stir until fully dispersed.

[0051] 2) Add 4 parts of proppant ultrafine calcium carbonate (median particle size of 50 nm) to the above liquid, stir and disperse for 10 minutes, and then disperse by ultrasonic for 30 minutes.

[0052] 3) Weigh 30 parts of styrene and 6 parts of lauryl methacrylate, stir until fully mixed, add to the liquid in 2), and shear emulsify for 15 minutes at 10,000 r / min in a shear emulsifier.

[0053] 4) Add the above liquid into the flask, keep stirring at 300r / min, and deoxygenate with nitrogen for 30 minutes.

[0054] 5) Raise the temperature to 70°C, add 0.2 parts of initiator potassium persulfate, and react for 7 hours under nitrogen.

[0055] 6) After the reaction is completed, keep stirring and stop heating. After the temperature drops to 40°C, pour the contents out of the flask to obtain the high temperature and high salt resistant deformable strong support plugging agent A2.

[0056] Preparation Example 3

[0057] This preparation example provides a high temperature and high salt resistance deformable strong support plugging agent, which is prepared by the following steps:

[0058] 1) Weigh 20 parts of maleic anhydride and 5 parts of diacetone acrylamide, add them into a flask containing 150 parts of water, stir until fully dispersed, and then add 0.2 parts of emulsifier sodium dodecylbenzene sulfonate, stir until fully dispersed.

[0059] 2) Add 2 parts of proppant nano-silica (median particle size 50 nm) to the above liquid, stir and disperse for 10 minutes, and then ultrasonically disperse for 30 minutes.

[0060] 3) Weigh 20 parts of styrene and 2 parts of lauryl methacrylate, stir until fully mixed, add to the liquid in 2), and shear emulsify at 9000 r / min for 15 minutes in a shear emulsifier.

[0061] 4) Add the above liquid into the flask, keep stirring at 300r / min, and deoxygenate with nitrogen for 30 minutes.

[0062] 5) Raise the temperature to 70°C, add 0.05 parts of initiator ammonium persulfate, and react for 8 hours under nitrogen.

[0063] 6) After the reaction is completed, keep stirring and stop heating. After the temperature drops to 40°C, pour the contents out of the flask to obtain the high temperature and high salt resistant deformable strong support plugging agent A3.

[0064] Preparation Example 4

[0065] This preparation example provides a high temperature and high salt resistance deformable strong support plugging agent, which is prepared by the following steps:

[0066] 1) Weigh 18 parts of maleic anhydride and 10 parts of diacetone acrylamide, add them into a flask containing 150 parts of water, stir until fully dispersed, and then add 0.5 parts of emulsifier sodium dodecylbenzene sulfonate, stir until fully dispersed.

[0067] 2) Add 4 parts of proppant ultrafine calcium carbonate (median particle size 50 nm) to the above liquid, stir and disperse for 10 minutes, and then ultrasonically disperse for 30 minutes.

[0068] 3) Weigh 30 parts of styrene and 6 parts of lauryl methacrylate, stir until fully mixed, add to the liquid in 2), and shear emulsify for 15 minutes at 10,000 r / min in a shear emulsifier.

[0069] 4) Add the above liquid into the flask, keep stirring at 300r / min, and deoxygenate with nitrogen for 30 minutes.

[0070] 5) Raise the temperature to 70°C, add 0.2 parts of initiator sodium persulfate, and react for 6 hours under nitrogen.

[0071] 6) After the reaction is completed, keep stirring and stop heating. After the temperature drops to 35° C., pour the contents out of the flask to obtain the high temperature and high salt resistant deformable strong support plugging agent A4.

[0072] Comparative Preparation Example 1

[0073] This comparative preparation example provides a plugging agent, which removes diacetone acrylamide compared to the original formula (Preparation Example 1). The specific synthesis method is as follows:

[0074] 1) Weigh 15 parts of maleic anhydride, add to a flask containing 150 parts of water, stir until fully dispersed, and then add 0.3 parts of emulsifier sodium dodecylbenzene sulfonate, stir until fully dispersed.

[0075] 2) Add 3 parts of proppant nano-silica (median particle size of 50 nm) to the above liquid, stir and disperse for 10 minutes, and then disperse by ultrasonic for 30 minutes.

[0076] 3) Weigh 25 parts of styrene and 5 parts of lauryl methacrylate, stir until fully mixed, add to the liquid in 2), and shear emulsify for 15 minutes at 8000 r / min in a shear emulsifier.

[0077] 4) Add the above liquid into the flask, keep stirring at 300r / min, and deoxygenate with nitrogen for 30 minutes.

[0078] 5) Raise the temperature to 70°C, add 0.15 parts of initiator potassium persulfate, and react for 7 hours under nitrogen.

[0079] 6) After the reaction is completed, keep stirring and stop heating. After the temperature drops to 30°C, pour the contents out of the flask to obtain the plugging agent DA1.

[0080] Comparative Preparation Example 2

[0081] This comparative preparation example provides a plugging agent, which removes the proppant compared to the original formula (Preparation Example 1). The specific synthesis method is as follows:

[0082] 1) Weigh 15 parts of maleic anhydride and 8 parts of diacetone acrylamide, add them into a flask containing 150 parts of water, stir until fully dispersed, and then add 0.3 parts of emulsifier sodium dodecylbenzene sulfonate, stir until fully dispersed.

[0083] 2) Weigh 25 parts of styrene and 5 parts of lauryl methacrylate, stir until fully mixed, add to the liquid in 2), and shear emulsify at 8000 r / min for 15 minutes in a shear emulsifier.

[0084] 3) Add the above liquid into the flask, keep stirring at 300r / min, and deoxygenate with nitrogen for 30 minutes.

[0085] 4) Raise the temperature to 70°C, add 0.15 parts of initiator potassium persulfate, and react for 7 hours under nitrogen.

[0086] 5) After the reaction is completed, keep stirring and stop heating. After the temperature drops to 30°C, pour the contents out of the flask to obtain the plugging agent DA2.

[0087] Comparative Preparation Example 3

[0088] This comparative preparation example provides a plugging agent, which removes maleic anhydride compared to the original formula (Preparation Example 1). The specific synthesis method is as follows:

[0089] 1) Weigh 8 parts of diacetone acrylamide, add it into a flask containing 150 parts of water, stir until fully dispersed, and then add 0.3 parts of emulsifier sodium dodecylbenzene sulfonate, stir until fully dispersed.

[0090] 2) Add 3 parts of proppant nano-silica (median particle size of 50 nm) to the above liquid, stir and disperse for 10 minutes, and then disperse by ultrasonic for 30 minutes.

[0091] 3) Weigh 25 parts of styrene and 5 parts of lauryl methacrylate, stir until fully mixed, add to the liquid in 2), and shear emulsify for 15 minutes at 8000 r / min in a shear emulsifier.

[0092] 4) Add the above liquid into the flask, keep stirring at 300r / min, and deoxygenate with nitrogen for 30 minutes.

[0093] 5) Raise the temperature to 70°C, add 0.15 parts of initiator potassium persulfate, and react for 7 hours under nitrogen.

[0094] 6) After the reaction is completed, keep stirring and stop heating. After the temperature drops to 30°C, pour the contents out of the flask to obtain the plugging agent DA3.

[0095] Comparative Preparation Example 4

[0096] This comparative preparation example provides a plugging agent, which removes lauryl methacrylate compared to the original formula (Preparation Example 1). The specific synthesis method is as follows:

[0097] 1) Weigh 15 parts of maleic anhydride and 8 parts of diacetone acrylamide, add them into a flask containing 150 parts of water, stir until fully dispersed, and then add 0.3 parts of emulsifier sodium dodecylbenzene sulfonate, stir until fully dispersed.

[0098] 2) Add 3 parts of proppant nano-silica (median particle size of 50 nm) to the above liquid, stir and disperse for 10 minutes, and then disperse by ultrasonic for 30 minutes.

[0099] 3) Weigh 25 parts of styrene and add it to the liquid in 2), and shear emulsify it in a shear emulsifier at 8000 r / min for 15 minutes.

[0100] 4) Add the above liquid into the flask, keep stirring at 300r / min, and deoxygenate with nitrogen for 30 minutes.

[0101] 5) Raise the temperature to 70°C, add 0.15 parts of initiator potassium persulfate, and react for 7 hours under nitrogen.

[0102] 6) After the reaction is completed, keep stirring and stop heating. After the temperature drops to 30°C, pour the contents out of the flask to obtain the plugging agent DA4.

[0103] Example 1

[0104] Drilling fluid F1 was prepared as follows: 4 parts by mass (the same below) of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, and 2 parts of A1 were added to obtain drilling fluid F1.

[0105] Example 2

[0106] Drilling fluid F2 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes and 2 parts of A2 were added to obtain drilling fluid F2.

[0107] Example 3

[0108] Drilling fluid F3 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes and 2 parts of A3 were added to obtain drilling fluid F3.

[0109] Example 4

[0110] Drilling fluid F4 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes and 2 parts of A4 were added to obtain drilling fluid F4.

[0111] Example 5

[0112] Drilling fluid F5 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of A1 were added, and then 15% by weight of NaCl was added to obtain drilling fluid F5.

[0113] Example 6

[0114] Drilling fluid F6 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of A2 were added, and then 15% by weight of NaCl was added to obtain drilling fluid F6.

[0115] Example 7

[0116] Drilling fluid F7 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of A3 were added, and then 15% by weight of NaCl was added to obtain drilling fluid F7.

[0117] Example 8

[0118] Drilling fluid F8 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of A4 were added, and then 15% by weight of NaCl was added to obtain drilling fluid F8.

[0119] Comparative Example 1

[0120] Drilling fluid DF1 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes without adding a treatment agent to obtain drilling fluid DF1.

[0121] Comparative Example 2

[0122] Drilling fluid DF2 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, and 15% by weight of NaCl was added to obtain drilling fluid DF2.

[0123] Comparative Example 3

[0124] Drilling fluid DF3 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, and 2 parts of polystyrene microsphere plugging agent were added to obtain drilling fluid DF3.

[0125] Comparative Example 4

[0126] Drilling fluid DF4 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of polystyrene microsphere plugging agent were added, and then 15% by weight of NaCl was added to obtain drilling fluid DF4.

[0127] Comparative Example 5

[0128] Drilling fluid DF5 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, and 2 parts of ultrafine calcium carbonate were added to obtain drilling fluid DF5.

[0129] Comparative Example 6

[0130] Drilling fluid DF6 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of ultrafine calcium carbonate were added, and then 15% by weight of NaCl was added to obtain drilling fluid DF6.

[0131] Comparative Example 7

[0132] Drilling fluid DF7 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, and 2 parts of plugging agent DA1 were added to obtain drilling fluid DF7.

[0133] Comparative Example 8

[0134] Drilling fluid DF8 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of plugging agent DA1 were added, and then 15% by weight of NaCl was added to obtain drilling fluid DF8.

[0135] Comparative Example 9

[0136] Drilling fluid DF9 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, and 2 parts of plugging agent DA2 were added to obtain drilling fluid DF9.

[0137] Comparative Example 10

[0138] Drilling fluid DF10 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of plugging agent DA2 were added, and then 15% by weight of NaCl was added to obtain drilling fluid DF10.

[0139] Comparative Example 11

[0140] Drilling fluid DF11 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, and 2 parts of plugging agent DA3 were added to obtain drilling fluid DF11.

[0141] Comparative Example 12

[0142] Drilling fluid DF12 was prepared as follows: 4 parts by mass of sodium bentonite were added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of plugging agent DA3 were added, and then 15% by weight of NaCl was added to obtain drilling fluid DF12.

[0143] Comparative Example 13

[0144] Drilling fluid DF13 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, and 2 parts of plugging agent DA4 were added to obtain drilling fluid DF13.

[0145] Comparative Example 14

[0146] Drilling fluid DF14 was prepared as follows: 4 parts by mass of sodium bentonite was added to 100 parts of water to obtain bentonite slurry, which was stirred at high speed for 20 minutes and then allowed to stand and cure at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of plugging agent DA4 were added, and then 15% by weight of NaCl was added to obtain drilling fluid DF14.

[0147] The above-mentioned polystyrene microsphere plugging agent is prepared by the following method:

[0148] 1) Weigh 30 parts of styrene and add dropwise into a beaker containing 150 parts of water. Emulsify at 8000 r / min for 15 min. Transfer to a three-necked flask and deoxygenate with nitrogen for 30 minutes.

[0149] 2) Keep stirring and heat to 70°C, add 0.1 parts of initiator potassium persulfate, and react for 7 hours with nitrogen.

[0150] 4) After the reaction is completed, keep stirring and stop heating. After the temperature drops to 30° C., pour the contents out of the flask to obtain the polystyrene microsphere plugging agent.

[0151] Test Example 1

[0152] 400 mL of the drilling fluids F1-F4 and DF1-DF14 were taken respectively, stirred at 5000 rpm for 20 min, put into an aging tank, put into a roller furnace, rolled at 240 ° C for 16 hours, taken out and cooled to room temperature, and stirred at 5000 rpm for 20 min. Then, the apparent viscosity (AV, mPa.s), plastic viscosity (PV, mPa.s), dynamic shear force (YP, Pa), medium pressure API water loss (FL) of the drilling fluids were measured in accordance with GB / T 16783.1-2014 "Field Test of Drilling Fluids in Petroleum and Natural Gas Industry Part 1: Water-based Drilling Fluids". API , mL) and sand bed filtration loss. The results are shown in Table 1.

[0153] Table 1 Drilling fluid performance test

[0154]

[0155]

[0156] It can be seen from the data in Table 1 that when the high temperature and high salt resistant deformable strong support plugging agent of the present invention is added to the drilling fluid, the rheological properties of the drilling fluid do not change much, and 2% of the plugging agent can reduce the API filtration loss of the drilling fluid by 45%, and the invasion depth of the sand bed plugging experiment is reduced by 80%. The drilling fluid can effectively plug the 60-80 mesh sand bed under the conditions of 240°C and 15% NaCl. However, the conventional ultrafine calcium carbonate rigid plugging agent and polystyrene microsphere flexible plugging agent are not effective under the conditions of 240°C and 15% NaCl. When the plugging agent formula of the present invention is changed and the key materials are removed, the plugging agent cannot achieve the optimal effect. The high temperature and high salt resistant deformable strong support plugging agent of the present invention has both the variability of flexible plugging agents and the strong support characteristics of rigid plugging agents, so it can play an excellent plugging role under the conditions of 240°C and 15% NaCl.

[0157] Test Example 2

[0158] The plugging effect of drilling fluids F1-F4 and DF1-DF14 on the core was tested on the core flow tester after aging at 240℃ for 16h. The initial forward standard brine permeability K of the rock sample was measured using the drilling fluid contamination holder. 1 Then the core contamination holder was removed and connected to the drilling fluid high temperature and high pressure dynamic comprehensive tester. The rock sample was positively plugged with the above drilling fluid. The drilling fluid temperature was 80°C, the pressure difference was 3.5MPa, the confining pressure was 5MPa, and the shear rate was 150s. -1 After 30 minutes of damage, the core contamination holder was removed and connected to the core flow tester to measure the core forward standard brine permeability K 2 , the core plugging rate is:

[0159]

[0160] The test results are shown in Table 2.

[0161] Table 2 Drilling fluid plugging performance test

[0162]

[0163]

[0164] It can be seen from the data in Table 2 that the high-temperature and high-salt resistant deformable strong support plugging agent of the present invention can still achieve efficient plugging of the core after high-temperature aging under high-salt conditions, with a plugging rate of 94.9%, which is significantly superior to traditional flexible and rigid plugging agents.

[0165] In summary, the high-temperature and high-salt resistant deformable strong support plugging agent of the present invention can effectively improve the plugging performance of drilling fluid under high-temperature and high-salt conditions and meet the needs of deep and ultra-deep drilling.

[0166] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0167] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0168] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A high temperature and high salt resistant deformable strong support plugging agent. The raw material components of the high temperature and high salt resistant deformable strong support plugging agent include 20-30 parts of styrene, 10-20 parts of maleic anhydride, 5-10 parts of diacetone acrylamide, 2-6 parts of lauryl methacrylate, 2-4 parts of proppant, 0.2-0.5 parts of emulsifier, 0.05-0.2 parts of initiator, and 130-160 parts of water by weight.

2. The high temperature and high salt resistance deformable strong support plugging agent according to claim 1, wherein: The proppant is ultrafine silicon dioxide and / or ultrafine calcium carbonate.

3. The high temperature and high salt resistance deformable strong support plugging agent according to claim 2, wherein: The particle size of the proppant is 50-500nm.

4. The high temperature and high salt resistance deformable strong support plugging agent according to claim 1, wherein: The emulsifier is one or a combination of two or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and dodecylphenol polyoxyethylene ether.

5. The high temperature and high salt resistance deformable strong support plugging agent according to claim 1, wherein: The initiator is one or more of potassium persulfate, ammonium persulfate and sodium persulfate.

6. The high temperature and high salt resistance deformable strong support plugging agent according to any one of claims 1 to 5, wherein: The high temperature and high salt resistance deformable strong support plugging agent is a core-shell structure, the shell of the core-shell structure is a copolymer of styrene and maleic anhydride, and the core of the core-shell structure is a proppant.

7. A method for preparing the high temperature and high salt resistance deformable strong support plugging agent according to any one of claims 1 to 6, comprising: 1) mixing maleic anhydride, diacetone acrylamide and water, adding an emulsifier, and stirring to obtain a first mixture; 2) adding a proppant to the first mixture, stirring and dispersing, and ultrasonically dispersing to obtain a second mixture; 3) Weighing styrene and lauryl methacrylate, mixing them, adding the second mixture, and shearing and emulsifying them in a shear emulsifier to obtain an emulsified mixed solution; 4) stirring the emulsified mixed solution, deoxygenating, heating, adding an initiator, and passing nitrogen gas to react; 5) After the reaction is completed, stirring is performed, and heating is stopped. After the temperature drops, the high temperature resistant and high salt resistant deformable strong support plugging agent is obtained.

8. A drilling fluid comprising the high temperature and high salt resistance deformable strong support plugging agent according to any one of claims 1 to 6.

9. The drilling fluid according to claim 8, wherein: The drilling fluid is a drilling fluid used in high temperature and high salt conditions, wherein the high temperature and high salt conditions are: 200° C. and above, and containing more than 10% salt.

10. The drilling fluid according to claim 9, wherein: The high temperature is 240° C., and the high salt is 15% NaCl.

11. The drilling fluid according to any one of claims 8 to 10, wherein: The mass percentage of the high temperature and high salt resistance deformable strong support plugging agent in the drilling fluid is 2%-5%.

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