A high-temperature, high-salt, deformable, strong-support plugging agent, its preparation method, and drilling fluid

Abstract

The present invention discloses a high-temperature, high-salt-resistant, deformable, strong-support plugging agent, a preparation method thereof, and a drilling fluid. The raw material components of the high-temperature, high-salt-resistant, deformable, strong-support plugging agent include, by weight, 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. The high-temperature, high-salt-resistant, deformable, strong-support plugging agent can effectively block cracks under high-temperature and high-salt conditions, and has the characteristics of both deformable and adaptive crack filling and strong support and plugging. It can be used to prepare deep and ultra-deep well drilling fluids.

Description

Technical Field

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

[0002] Drilling fluid, known as the "blood of drilling," 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, and 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 drilling fluid performance. Drilling fluid enters deep into the formation along micro-cracks and fissures, causing complex downhole situations and accidents such as well wall collapse, leakage, pipe sticking, and reservoir damage, resulting in significant 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 temperatures and high salts, but they cannot effectively match the shape and size of pores and cracks in the formation, resulting in poor sealing effects.

[0003] CN113292973A discloses a high-temperature-resistant silica-grafted tertiary amine nano-plugging agent, which can improve the plugging performance of drilling fluids at 150°C. CN113355061A discloses a flexible-on-the-outer-and-rigid-on-the-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. This plugging agent can effectively improve the plugging performance of drilling fluids at 160°C. CN109439298A discloses a high-temperature and calcium-resistant water-based drilling fluid plugging agent for protecting oil and gas reservoirs. This plugging agent can demonstrate good plugging performance at 200°C and 1% CaCl2. However, none of the above plugging agents demonstrate plugging capabilities at higher temperatures or when NaCl is added, 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 objectives, 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, by weight, 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.

[0006] In some embodiments, the raw material components of the high-temperature, high-salt resistant, 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 resistant 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 proppant has a particle size of 50-500 nm.

[0010] In some embodiments, the emulsifier is one or a combination of two or more of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, and dodecylphenol polyoxyethylene 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, high-salt, deformable, strong-support plugging agent described in the first aspect of the present invention, comprising:

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

[0015] 2) adding a proppant to the first mixture in 2), stirring and dispersing the mixture, and ultrasonically dispersing the mixture 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 mixture in 3), deoxygenating, heating, adding an initiator, and passing nitrogen gas through the mixture to react;

[0018] 5) After the reaction is completed, stirring is performed, and heating is stopped. After the temperature drops, the high-temperature-resistant, high-salt-resistant, deformable, and 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 is lowered in step 5) 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 salinity 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-resistant, high-salt-resistant, 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, high-salt resistant, deformable, and strongly supported 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. It can be well dispersed in drilling fluid under ultra-high temperature and high-salt conditions and effectively plug cracks.

[0034] 2. This high-temperature, high-salt-resistant, deformable, and strong-support plugging agent features a flexible, resilient polymer shell that adaptively plugs formation fractures through deformation. Its core is a heat- and salt-resistant, inert, rigid proppant, which acts as a support framework and enhances the agent's strength. Under differential pressure, the plugging agent reduces drilling fluid loss and forms a filling and deposited layer around the wellbore, forming an effective pressure-bearing plugging layer. This prevents pressure transmission and filtrate intrusion, thereby filling fractures and reducing drilling fluid loss pathways.

[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, and the molecular steric hindrance is large. The molecular structure determines its good temperature and salt resistance, so 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 and 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-breathing." At room temperature, the plugging agent can absorb water in the drilling fluid and expand, improving its deformation capacity. After entering the high-temperature and high-pressure cracks, the plugging agent releases the absorbed water, thereby increasing the rigidity of the plugging agent, supporting and sealing the cracks, and further improving the plugging effect.

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

[0039] The specific embodiments of the present invention are further described below. The present invention can be better understood based on the following examples. However, it is readily understood by those skilled in the art that the specific material ratios, process conditions, and results described in the examples are merely illustrative of 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, high-salt resistant, 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 to a flask containing 150 parts of water, stir until fully dispersed, and then add 0.3 parts of emulsifier sodium dodecylbenzene sulfonate and 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 ultrasonically disperse for 30 minutes.

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

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

[0046] 5) The temperature was raised to 70° C., 0.15 parts of potassium persulfate as an initiator was added, and nitrogen was passed through to react for 7 hours.

[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, high-salt resistant, 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 to a flask containing 150 parts of water, stir until fully dispersed, and then add 0.4 parts of emulsifier sodium lauryl sulfate and 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 ultrasonically disperse for 30 minutes.

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

[0053] 4) Add the above liquid into the flask, keep stirring at 300 r / 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 allow to 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, high-salt resistant, 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 to a flask containing 150 parts of water, stir until fully dispersed, and then add 0.2 parts of emulsifier sodium dodecylbenzene sulfonate and 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 described in 2), and shear emulsify in a shear emulsifier at 9000 r / min for 15 minutes.

[0061] 4) Add the above liquid into the flask, keep stirring at 300 r / 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 allow to 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, high-salt resistant, 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 to a flask containing 150 parts of water, stir until fully dispersed, and then add 0.5 parts of emulsifier sodium dodecylbenzene sulfonate and 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 them to the liquid described in 2), and shear emulsify them in a shear emulsifier at 10,000 r / min for 15 minutes.

[0069] 4) Add the above liquid into the flask, keep stirring at 300 r / 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 allow to 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 and add it to a flask containing 150 parts of water. Stir until fully dispersed. Then add 0.3 parts of emulsifier sodium dodecylbenzenesulfonate and 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 ultrasonically disperse for 30 minutes.

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

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

[0078] 5) The temperature was raised to 70° C., 0.15 parts of potassium persulfate as an initiator was added, and nitrogen was passed through to react for 7 hours.

[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 to a flask containing 150 parts of water, stir until fully dispersed, and then add 0.3 parts of emulsifier sodium dodecylbenzene sulfonate and stir until fully dispersed.

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

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

[0085] 4) Raise the temperature to 70° C., add 0.15 parts of potassium persulfate as an initiator, and allow to 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 and add them to a flask containing 150 parts of water. Stir until fully dispersed. Then add 0.3 parts of emulsifier sodium dodecylbenzene sulfonate and 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 ultrasonically disperse for 30 minutes.

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

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

[0093] 5) The temperature was raised to 70° C., 0.15 parts of potassium persulfate as an initiator was added, and nitrogen was passed through to react for 7 hours.

[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 to a flask containing 150 parts of water, stir until fully dispersed, and then add 0.3 parts of emulsifier sodium dodecylbenzene sulfonate and 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 ultrasonically disperse for 30 minutes.

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

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

[0101] 5) The temperature was raised to 70° C., 0.15 parts of potassium persulfate as an initiator was added, and nitrogen was passed through to react for 7 hours.

[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 a bentonite slurry. The slurry was stirred at high speed for 20 minutes and then cured 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 a bentonite slurry. The slurry 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 a bentonite slurry. The slurry 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 a bentonite slurry. The slurry 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 a bentonite slurry. The mixture was stirred at high speed for 20 minutes and then cured at room temperature for 24 hours. The bentonite slurry was stirred for another 20 minutes, 2 parts of A1 was 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 a bentonite slurry. The mixture was stirred at high speed for 20 minutes and then cured at room temperature for 24 hours. The bentonite slurry was stirred for an additional 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 a bentonite slurry. The mixture was stirred at high speed for 20 minutes and then cured at room temperature for 24 hours. The bentonite slurry was stirred for an additional 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 a bentonite slurry. The slurry was stirred at high speed for 20 minutes and then cured at room temperature for 24 hours. The bentonite slurry was stirred for an additional 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. The mixture was stirred at high speed for 20 minutes and then allowed to stand 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. The mixture 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. The mixture 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. The slurry 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. The slurry 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. The mixture 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. The slurry 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 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 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. The slurry 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 to a beaker containing 150 parts of water. Emulsify at 8000 rpm for 15 minutes. Transfer the mixture to a three-necked flask and deoxygenate with nitrogen for 30 minutes.

[0149] 2) Heat the mixture to 70°C while stirring, add 0.1 parts of initiator potassium persulfate, and allow to react for 7 hours under 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, placed in a roller furnace, and rolled at a constant temperature of 240 ° C for 16 hours. After that, the mixture was 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 the provisions of GB / T 16783.1-2014 "Field testing of drilling fluids in the 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. 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, conventional ultrafine calcium carbonate rigid plugging agents and polystyrene microsphere flexible plugging agents 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 a core flow tester after aging at 240°C for 16 hours. The initial forward standard brine permeability K1 of the rock sample was measured using a drilling fluid contamination holder. The core contamination holder was then removed and connected to a drilling fluid high-temperature and high-pressure dynamic comprehensive tester. The rock sample was positively plugged using the drilling fluids at a drilling fluid temperature of 80°C, a pressure differential of 3.5 MPa, a confining pressure of 5 MPa, and a shear rate of 150 s. -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 K2. 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, meeting 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, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection 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 appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0168] In addition, the 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, 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, by weight, 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.

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 50-500 nm.

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 lauryl sulfate, sodium dodecylbenzenesulfonate 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-resistant, high-salt-resistant, deformable, and strongly supporting 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, high-salt, 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 the mixture, and ultrasonically dispersing the mixture to obtain a second mixture; 3) Weighing styrene and lauryl methacrylate, mixing, adding the second mixture, and shearing and emulsifying in a shear emulsifier to obtain an emulsified mixed solution; 4) stirring the emulsified mixed solution, deoxygenating it, heating it, adding an initiator, and passing nitrogen through it to react; 5) After the reaction is completed, stirring is performed, and heating is stopped. After the temperature drops, the high-temperature-resistant, high-salt-resistant, deformable, and 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 used in high-temperature and high-salt conditions, wherein the high-temperature and high-salt conditions are: 200° C. and above, and a salt content of more than 10%.

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-resistant, high-salt-resistant, deformable, strong-support plugging agent in the drilling fluid is 2%-5%.

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