A water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters, its preparation method and application

Abstract

This invention provides a water-based drilling fluid for solidifying the wellbore in deep oil and gas wells at depths of 10,000 meters, along with its preparation method and application, belonging to the field of drilling fluid technology. The water-based drilling fluid for solidifying the wellbore in deep oil and gas wells at 10,000 meters comprises the following raw materials in parts by weight: 100 parts water, 1-5 parts modified clay shearing agent, 2-4 parts hydrophobic associating polymer flow modifier, 3-8 parts plugging agent, 2-5 parts hyperbranched polymer filtration reducer, and 1-3 parts cemented plugging wall-solidifying agent. This invention also provides a method for preparing the above-mentioned drilling fluid. In this invention, the flow modifier, plugging agent, filtration reducer, and wall-solidifying agent work synergistically to enable the drilling fluid to maintain good rheological, filtration, plugging, and inhibition properties for a long time under 240°C and saturated salt conditions, achieving a strong wall-solidifying effect. This effectively maintains the stability of the wellbore in deep oil and gas wells at 10,000 meters, preventing well collapse, lost circulation, blowouts, and other drilling complications, and can be used in drilling deep oil and gas wells at 10,000 meters.

Description

Technical Field

[0001] This invention relates to a water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters, its preparation method and application, and belongs to the field of drilling fluid technology. Background Technology

[0002] Drilling fluid, known as the "blood of drilling," has functions such as stabilizing the wellbore, carrying cuttings, and balancing formation pressure. It is an indispensable core engineering technology for oil and gas exploration and development, and is directly related to the success or failure of drilling and the production of oil and gas reservoirs. During the drilling of deep-earth oil and gas wells at depths of 10,000 meters, the harsh conditions of "four extremes"—extremely high temperature (>200℃), extremely high pressure (>140MPa), extremely high salinity (formation fluid salinity >200,000mg / L), and extremely high stress (>160MPa)—cause the drilling fluid rheological properties to decrease or even be lost, and the filtration loss to increase sharply. In addition, due to the complex formation conditions and the coexistence of multiple rock types (mudstone, sandstone, dolomite, etc.), the wellbore instability mechanism is complex. Existing water-based drilling fluids are difficult to stabilize the wellbore, and the wellbore is prone to collapse, spalling, and other phenomena, resulting in huge drilling risks. Accidents such as well collapse, well leakage, and well blowout occur frequently, which seriously hinders the exploration and development of oil and gas at depths of 10,000 meters. There is an urgent need to develop a strong-wall-stabilizing water-based drilling fluid that can stabilize the wellbore of oil and gas wells at depths of 10,000 meters.

[0003] Chinese patent documents CN117736707A and CN117946640A disclose a 230℃-resistant, high-salt, high-density water-based drilling fluid and its preparation method and application, and a 230℃-resistant, high-mineralization environmentally friendly water-based drilling fluid and its preparation method and application, respectively. These two drilling fluids exhibit good rheological and filtration properties under 230℃ high-salt conditions, and also have certain plugging and inhibition properties, but they do not show effective performance retention at higher temperatures. Chinese patent document CN115466603A discloses a 240℃-resistant, salt-resistant, plugging water-based drilling fluid and its preparation method and application. This system, through the synergistic effect of plugging agent and anti-collapse agent, effectively plugs and maintains wellbore stability under ultra-high temperature conditions of 240℃. However, the polyacrylamide potassium salt inhibitor in this system is prone to failure under high temperature and high salt conditions, and the mudstone and shale formations encountered during drilling may lead to hydration expansion and wellbore instability.

[0004] Existing water-based drilling fluids generally suffer from severe performance degradation under the ultra-high temperature and high salinity conditions of oil and gas wells at depths of 10,000 meters, and cannot meet the wellbore stability requirements of various complex lithological formations, thus failing to meet the needs of oil and gas drilling at depths of 10,000 meters. Therefore, there is an urgent need to develop a water-based drilling fluid for oil and gas well wall stabilization at depths of 10,000 meters, to effectively prevent drilling complications such as well collapse, lost circulation, and blowouts, and to provide technical support for oil and gas drilling at depths of 10,000 meters. Summary of the Invention

[0005] To address the shortcomings of existing technologies, particularly the insufficient wall-stabilizing ability of current deep formation water-based drilling fluids, which makes it difficult to maintain wellbore stability in oil and gas wells with different lithologies at depths of 10,000 meters, this invention provides a wall-stabilizing water-based drilling fluid for oil and gas wells at depths of 10,000 meters, along with its preparation method and applications. This invention constructs a wall-stabilizing water-based drilling fluid for oil and gas wells at depths of 10,000 meters using modified clay shearing agent, hydrophobic associating polymer flow pattern modifier, plugging agent, hyperbranched polymer filtration reduction agent, and cemented plugging wall-stabilizing agent as core components. This drilling fluid maintains excellent rheological, filtration, plugging, and inhibition properties for extended periods under 240°C and saturated salt conditions, effectively maintaining wellbore stability in oil and gas wells at depths of 10,000 meters and effectively preventing drilling complexities such as well collapse, lost circulation, and blowouts, providing technical support for oil and gas drilling at depths of 10,000 meters.

[0006] This invention is achieved through the following technical solution:

[0007] A water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters comprises the following raw materials in parts by weight: 100 parts water, 1-5 parts modified clay shearing agent, 2-4 parts hydrophobic associating polymer flow modifier, 3-8 parts plugging agent, 2-5 parts hyperbranched polymer filtration reducer, and 1-3 parts cemented plugging wall-solidifying agent.

[0008] According to a preferred embodiment of the present invention, the modified clay shearing agent is prepared by the following method:

[0009] (1) Mix magnesium aluminum hydrotalcite and 1:1 type clay minerals, add them to an ethanol aqueous solution to obtain a dispersion;

[0010] (2) Add hexadecyltrimethylammonium bromide and dimethylaminopropylmethacrylamide to the dispersion obtained in step (1), stir evenly, heat to the reaction temperature under nitrogen protection, add initiator, and carry out constant temperature reaction under nitrogen protection; after the reaction is completed, centrifuge, wash, dry and crush to obtain modified clay cutting agent.

[0011] Preferably, the magnesium aluminum hydrotalcite in step (1) is a carbonate-type magnesium aluminum hydrotalcite; more preferably, the chemical composition of the magnesium aluminum hydrotalcite is Mg6Al2(OH). 16 (CO3)·4H2O.

[0012] Preferably, the 1:1 type clay mineral in step (1) is a clay mineral composed of two different crystal sheets in a 1:1 ratio. The composition of the crystal sheets includes, but is not limited to, silicon-oxygen tetrahedrons, aluminum-oxygen octahedrons, dioctahedral mica, and dioctahedral montmorillonite. The mass ratio of the magnesium-aluminum hydrotalcite to the 1:1 type clay mineral is 0.1-0.3:1.

[0013] Preferably, the volume ratio of deionized water to anhydrous ethanol in the ethanol aqueous solution in step (1) is 1-3:1.

[0014] Preferably, the total mass concentration of magnesium aluminum hydrotalcite and 1:1 type clay minerals in the dispersion in step (1) is 5-10%.

[0015] Preferably, in step (2), the mass of hexadecyltrimethylammonium bromide is 0.3-0.8% of the mass of the dispersion; and the mass of dimethylaminopropylmethacrylamide is 0.5-1.5% of the mass of the dispersion.

[0016] Preferably, the initiator in step (2) is ammonium persulfate or potassium persulfate, and the mass of the initiator is 0.001-0.01% of the mass of the dispersion.

[0017] Preferably, the reaction temperature in step (2) is 55-65℃, and the isothermal reaction time is 6-8h.

[0018] Preferably, the washing in step (2) involves washing the solid obtained by centrifugation with deionized water 3-5 times; the drying involves drying at 80-100℃ for 8-12 hours.

[0019] According to a preferred embodiment of the present invention, the hydrophobic associating polymer flow modifier is prepared by the following method:

[0020] (I) Add alkyl-substituted acrylamide, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, long-chain alkyl dimethylallyl ammonium chloride and 2-methyl-1-vinylimidazolium to water and stir until uniformly dispersed to obtain a monomer solution;

[0021] (II) Nitrogen gas is introduced into the monomer solution obtained in step (I), the temperature is raised to the first temperature, phenyltriethoxysilane is added, and after stirring until dissolved, the temperature is raised to the second temperature, azobisisobutylamidine hydrochloride and sodium bisulfite are added to initiate the reaction, and nitrogen gas is introduced to carry out the reaction at a constant temperature; after the reaction is completed, the hydrophobic associative polymer flow modifier is obtained by washing and drying.

[0022] Preferably, the alkyl-substituted acrylamide in step (I) is one or a combination of two or more of N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, and N-hydroxymethylacrylamide.

[0023] Preferably, the long-chain alkyl dimethyl allyl ammonium chloride in step (I) is a quaternary ammonium chloride compound, wherein the three substituents are two methyl groups and an allyl group, and the fourth substituent is an alkyl group of C10 to C18; more preferably, the long-chain alkyl dimethyl allyl ammonium chloride is hexadecyl dimethyl allyl ammonium chloride or octadecyl dimethyl allyl ammonium chloride.

[0024] Preferably, the molar ratio of the alkyl-substituted acrylamide, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, long-chain alkyl dimethyl allyl ammonium chloride, and 2-methyl-1-vinylimidazolium in step (I) is 1:0.2-0.4:0.05-0.15:0.05-0.15.

[0025] Preferably, the concentration of the monomer solution in step (I) is 20-40 wt%; the monomer is alkyl-substituted acrylamide, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, long-chain alkyl dimethyl allyl ammonium chloride, and 2-methyl-1-vinylimidazolium.

[0026] Preferably, the first temperature in step (II) is 40-50°C; the mass of the phenyltriethoxysilane is 0.05-0.15% of the total mass of the monomer.

[0027] Preferably, the mass of the azobisisobutylamidine hydrochloride in step (II) is 0.1-1% of the total mass of the monomers; and the mass of the sodium bisulfite is 0.05-0.15% of the total mass of the monomers.

[0028] According to the present invention, in step (II), the total mass of monomers refers to the total mass of alkyl-substituted acrylamide, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, long-chain alkyl dimethylallyl ammonium chloride and 2-methyl-1-vinylimidazolium.

[0029] Preferably, the second temperature in step (II) is 70-80℃; the isothermal reaction time is 4-6h.

[0030] Preferably, the washing in step (II) involves washing the product obtained from the reaction with acetone 3-5 times, and the drying involves drying at 80-100°C for 8-12 hours.

[0031] According to the present invention, the sealing agent is prepared according to the method of Chinese patent document CN115160513A.

[0032] According to a preferred embodiment of the present invention, the hyperbranched polymer filtration loss reducer is prepared by the following method:

[0033] (i) Trimethylolpropane was heated and melted under nitrogen protection; then a methanol solution of potassium methoxide was added to carry out the reaction; after the reaction was completed, excess methanol was removed, the temperature was raised to 90-100°C, glycidyl was added, and the reaction was carried out at an isothermal temperature to obtain hyperbranched glycidyl.

[0034] (ii) N,N-dimethylacrylamide, (3-acrylamidopropyl)trimethylammonium chloride, methyl allyl alcohol polyoxyethylene ether and the hyperbranched glycidyl obtained in step (ii) are added to water and stirred at 40-45°C under nitrogen protection until completely dissolved. Then, an aqueous solution of cerium ammonium nitrate is added to carry out the reaction. After the reaction is completed, ethanol is added to the reaction solution for precipitation. After centrifugation, the lower layer product is purified to obtain the hyperbranched polymer filtration loss reducer.

[0035] Preferably, the heating in step (i) is heating to 70-80°C.

[0036] Preferably, the potassium methoxide methanol solution in step (i) is obtained by dissolving potassium methoxide in methanol, wherein the mass ratio of potassium methoxide to methanol is 0.5-0.7:1; and the mass ratio of potassium methoxide to trimethylolpropane is 0.1-0.2:1.

[0037] Preferably, in step (i), the temperature for reacting the potassium methoxide in methanol solution is 70-80°C, and the reaction time is 20-40 min; after the reaction is completed, excess methanol in the reaction system is removed by vacuuming.

[0038] Preferably, the mass ratio of glycidol to trimethylolpropane in step (i) is 20-30:1; and the glycidol is added at a rate of 0.1-0.2 mL / min.

[0039] Preferably, in step (i), the time for adding glycidyl glycerin and reacting at a constant temperature is 4-6 hours.

[0040] Preferably, in step (ii), the mass ratio of N,N-dimethylacrylamide, (3-acrylamidopropyl)trimethylammonium chloride, methyl allyl alcohol polyoxyethylene ether, and hyperbranched glycidyl is 10:4-6:1-3:0.05-0.15; the mass ratio of N,N-dimethylacrylamide to water is 1:10-20; the structural formula of the methyl allyl alcohol polyoxyethylene ether is shown below, and the average molecular weight of the methyl allyl alcohol polyoxyethylene ether is 1000-4000.

[0041]

[0042] Methyl allyl alcohol polyoxyethylene ether

[0043] Preferably, the concentration of the cerium ammonium nitrate aqueous solution in step (ii) is 0.1-0.3 wt%, and the mass ratio of the cerium ammonium nitrate aqueous solution to N,N-dimethylacrylamide is 4-6:10.

[0044] Preferably, the temperature of the reaction in step (ii) is 60-70°C and the reaction time is 1-3 hours.

[0045] Preferably, the purification step in step (ii) is as follows: after dissolving the lower layer product obtained by centrifugation in water, ethanol is added for precipitation, followed by centrifugation. The above steps are repeated 2-3 times, and then the product is freeze-dried and pulverized to obtain a hyperbranched polymer filtration loss reducer. There are no specific requirements for the amount of ethanol used for precipitation and the amount of water used for dissolution, as long as the precipitation and dissolution processes can be completed. This is a commonly used method for purifying polymers in the field.

[0046] According to the present invention, the cementing and sealing wall-fixing agent is prepared according to the method of Chinese patent document CN114716984A.

[0047] According to the present invention, the preparation method of the above-mentioned water-based drilling fluid for solidifying the wall of oil and gas at a depth of 10,000 meters includes the following steps:

[0048] Add the modified clay cutting agent to water and stir for more than 24 hours. Then add the hydrophobic associating polymer flow modifier, plugging agent, hyperbranched polymer filtration reducer and cementing plugging wall solidifying agent, and stir evenly to obtain the wall solidifying water-based drilling fluid for oil and gas at a depth of 10,000 meters.

[0049] According to a preferred embodiment of the present invention, the specific preparation method includes the following steps:

[0050] Water is added to a high-speed mixing cup, and modified clay shearing agent is added under low-speed stirring for more than 24 hours; hydrophobic associating polymer flow modifier is added, and high-speed stirring is carried out for 20 minutes; plugging agent is added, and high-speed stirring is carried out for 20 minutes; hyperbranched polymer filtration reducer is added, and high-speed stirring is carried out for 20 minutes; cemented plugging wall-stabilizing agent is added, and high-speed stirring is carried out for 20 minutes to obtain a wall-stabilizing water-based drilling fluid for deep-ground oil and gas at a depth of 10,000 meters; the low-speed stirring speed is 1000-3000 r / min, and the high-speed stirring speed is 8000-10000 r / min.

[0051] According to the present invention, the application of the above-mentioned water-based drilling fluid for solidifying the well wall in deep and ultra-deep oil and gas formations is used to maintain the stability of the well wall, prevent well collapse, blowout, stuck pipe and other drilling complications, and ensure the smooth progress of deep and ultra-deep oil and gas drilling; the deep and ultra-deep oil and gas formations include but are not limited to formations at depths of 10,000 meters.

[0052] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0053] The technical features and beneficial effects of this invention are as follows:

[0054] 1. The solid-wall type water-based drilling fluid of the present invention incorporates a specific modified clay cutting agent. The modified clay cutting agent of the present invention is a composite material that combines polymer and clay. The preferred type of 1:1 intercalating clay mineral (such as attapulgite) of the present invention is easier to intercalate and modify than the commonly used 2:1 type clay mineral (such as bentonite), forming a strongly electron-deficient and strongly charged structure. It has better dispersibility, thixotropy, suspension and high temperature stability, effectively ensuring the suspension of weighting materials and drill cuttings in the drilling fluid under ultra-high temperature saturated salt conditions.

[0055] 2. The solid-wall type water-based drilling fluid of this invention incorporates a hydrophobic associating polymer flow modifier. This hydrophobic associating polymer flow modifier is an amphoteric copolymer with a hydrophobic associating structure, which has the functions of regulating the rheological properties of the drilling fluid and reducing filtration loss. Alkyl-substituted acrylamide provides a high-bond-energy CC backbone, increasing the overall temperature resistance of the polymer; the five-membered imidazole heterocycle increases the rigidity of the molecular chain, significantly improving the resistance of the molecular chain to hydrolysis under ultra-high temperature and high salt conditions; the amphoteric structure of the betaine monomer enables the polymer to be tightly adsorbed with the hydrotalcite and clay in the modified clay shearing agent, improving the efficiency of action; the sulfonic acid group provides a thicker hydration film, which is stable under ultra-high temperature and ultra-high pressure saturated salt conditions, effectively reducing filtration loss; the hydrophobic long chain of the long-chain alkyl dimethyl allyl ammonium chloride enables the polymer to form intramolecular association, enhancing the polymer's thickening effect, and as a cationic monomer, it enables the polymer to have salt responsiveness, maintaining stable rheological properties even under high salt conditions.

[0056] 3. The solid-wall type water-based drilling fluid of this invention incorporates a hyperbranched polymer filtration reducer. This hyperbranched polymer filtration reducer exhibits a three-dimensional dendritic structure with numerous branching points, preventing molecular chain entanglement and resulting in excellent molecular chain adsorption capacity. Furthermore, it possesses high rigidity and significant steric hindrance, ensuring long-term structural stability of the polymer under ultra-high temperature conditions and effectively resisting the strong double-layer compression effect of salt ions on the molecular chains. This allows the polymer to efficiently maintain the spatial extension of its molecular chains under ultra-high temperature and saturated salt conditions, resulting in a thicker hydration film. This ensures stable performance under ultra-high temperature and ultra-high pressure saturated salt conditions, effectively reducing filtration loss. The abundant terminal cationic groups can form multi-point links with clay minerals in the formation, creating a polymer network on the wellbore, while effectively preventing shale expansion and maintaining wellbore stability. Moreover, the viscosity of the hyperbranched polymer does not change with increasing molecular weight, making the hyperbranched polymer filtration reducer of this invention less viscous than traditional linear macromolecular filtration reducers, facilitating drilling fluid formulation and rheological property control.

[0057] 4. The solid-wall type water-based drilling fluid of this invention incorporates a specific plugging agent. Its outer layer is a flexible polymer film with numerous heterocyclic and benzene ring structures. The molecular chains are highly rigid and have significant steric hindrance, maintaining high elasticity and toughness under ultra-high temperature saturated salt conditions. This allows it to adapt to the size and shape of the mud cake and formation pores, achieving efficient and dense filling. The internal rigid nano-silica serves as a supporting framework, significantly increasing the strength of the plugging agent after sealing. This effectively reduces drilling fluid loss, prevents pressure transmission, and maintains wellbore stability under ultra-high temperature saturated salt conditions.

[0058] 5. The wall-solidifying water-based drilling fluid of the present invention incorporates a cementing and sealing wall-solidifying agent, which is an organic / inorganic composite material. Firstly, it can effectively adhere to the wellbore pores in water, bridging and sealing the formation pores through rigid silica, and then cementing and solidifying. Secondly, the wall-solidifying agent, cemented and solidified on the wellbore surface, can effectively inhibit shale hydration dispersion. Thirdly, the wall-solidifying agent can cement and solidify during the drilling fluid filtration process to form mud cake, improving the density of the mud cake, effectively reducing drilling fluid filtration loss, and thus helping to maintain or even enhance rock strength, playing a role in stabilizing the wellbore in fractured formations.

[0059] 6. In the solidified wall type water-based drilling fluid of the present invention, the modified clay cutting agent, hydrophobic associating polymer flow pattern regulator, and hyperbranched polymer filtration reducer synergistically form a robust network structure in the drilling fluid that resists ultra-high temperature and high mineralization. Under ultra-high temperature, high mineralization, and high density conditions, it plays a good role in reducing filtration loss, maintaining good rheology, suspending and weighting materials and drill cuttings for a long time. The plugging agent and cemented plugging solidified wall agent seal the mud cake and the pores and fractures in the formation, reduce filtration loss, strengthen the fractured formation well wall, prevent pressure transmission, and make the well wall more robust. At the same time, the hyperbranched polymer filtration reducer forms a polymer film on the well wall, inhibits the hydration and expansion of formation clay minerals, and further ensures the stability of the well wall. With the synergistic effect of various treatment agents, the drilling fluid can maintain good rheological, filtration, plugging and inhibition properties for a long time under 240℃ and saturated salt conditions, which can play a strong wall-strengthening role, effectively maintain the well wall stability of oil and gas wells at a depth of 10,000 meters, and effectively prevent drilling complexities such as well collapse, well leakage, and well blowout. It can be used in drilling of 10,000-meter deep wells.

[0060] 7. The solid-wall type water-based drilling fluid system of the present invention does not contain sulfonated materials, has a simple preparation process, and does not release toxic or odorous gases under high temperature and high salinity conditions. It has good environmental performance and can be promoted and used in areas with strict environmental protection requirements. It can provide technical support for maintaining my country's strategic mission of drilling oil and gas at depths of 10,000 meters. Detailed Implementation

[0061] The specific embodiments of the present invention will be further described below. The present invention can be better understood from the following examples. However, those skilled in the art will readily understand that the specific material ratios, process conditions, and results described in the examples are for illustrative purposes only and should not, and will not, limit the present invention as described in detail in the claims. Furthermore, unless otherwise specified, all materials used in the following examples and comparative examples are commercially available, and all methods used are conventional methods in the art.

[0062] Unless otherwise specified, all “parts” in the following preparation examples and embodiments refer to parts by weight.

[0063] Preparation Example 1

[0064] The preparation method of modified clay cutting agent includes the following steps:

[0065] 1) Mix magnesium aluminum hydrotalcite and 1:1 type clay minerals at a mass ratio of 0.2:1, weigh 16g, and disperse it in 200g of ethanol aqueous solution (deionized water: anhydrous ethanol = 2:1, v / v) by ultrasonic stirring to prepare a dispersion.

[0066] The chemical composition of the magnesium aluminum hydrotalcite is Mg6Al2(OH). 16 (CO3)·4H2O; The 1:1 type clay mineral is rettosite composed of dioctahedral mica and dioctahedral montmorillonite in a regular 1:1 interlayered manner.

[0067] 2) Add 1.08 g cetyltrimethylammonium bromide and 2.16 g dimethylaminopropylmethacrylamide to the above dispersion, stir and disperse thoroughly, then transfer to a three-necked flask, purge with nitrogen and heat to 60 °C, add 0.011 g ammonium persulfate to initiate the reaction, keep stirring, and react at a constant temperature of 60 °C for 7 h under nitrogen protection.

[0068] 3) After the reaction is complete, the reaction product is centrifuged. The resulting solid is washed 5 times with deionized water by centrifugation. The lower precipitate is dried in a 90℃ oven for 12 hours and then crushed. The resulting solid is the modified clay cutting agent.

[0069] Preparation Example 2

[0070] The preparation method of the hydrophobic associating polymer flow modifier includes the following steps:

[0071] 1) Mix N,N-diethylacrylamide, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt (CAS No.: 3637-26-1), octadecyl dimethyl allyl ammonium chloride and 2-methyl-1-vinylimidazolium in a molar ratio of 1:0.3:0.1:0.1, weigh 30g of the monomer, add it to 70g of water, and stir until fully dispersed to obtain a monomer solution.

[0072] 2) Transfer the above monomer solution to a three-necked flask, purge with nitrogen and heat to 45°C, add 0.03g of phenyltriethoxysilane, stir thoroughly until dissolved, heat to 75°C, add 0.15g of azobisisobutylamidine hydrochloride and 0.03g of sodium bisulfite to initiate the reaction, and react at a constant temperature of 75°C for 5h under nitrogen protection.

[0073] 3) After the reaction is complete, the product obtained is washed with acetone 5 times, dried in an oven at 90°C for 12 hours and then pulverized. The resulting light yellow powder is the hydrophobic associating polymer flow modifier.

[0074] Preparation Example 3

[0075] The preparation method of the hyperbranched polymer filtration loss reducer includes the following steps:

[0076] 1) Add 2g of trimethylolpropane to a three-necked flask, purge with nitrogen for protection, and stir to melt in an oil bath at 75°C.

[0077] 2) Weigh 0.3g of potassium methoxide and dissolve it in 0.5g of methanol. Add the resulting potassium methoxide methanol solution to a three-necked flask using a syringe. React at 75°C for 30 minutes, then remove excess methanol from the reaction system by vacuuming.

[0078] 3) Heat the reaction system to 95°C, and add 50g of glycidyl ether dropwise at a rate of 0.1mL / min using a syringe pump. After the addition is complete, continue the reaction at 95°C for 5 hours to obtain hyperbranched glycidyl ether.

[0079] 4) Add 150g water, 10g N,N-dimethylacrylamide, 5g (3-acrylamidopropyl)trimethylammonium chloride, 2g methyl allyl alcohol polyoxyethylene ether (average molecular weight 2000) and 0.1g hyperbranched glycidyl ether to another three-necked flask, purge with nitrogen and stir at 40°C until completely dissolved. Add 5g of 0.2wt% cerium ammonium nitrate aqueous solution using a syringe, and heat to 65°C and react for 2 hours.

[0080] 5) Add 50 mL of ethanol to the reaction solution to precipitate the product, then centrifuge. The lower layer product obtained by centrifugation is purified to obtain the hyperbranched polymer filtration loss reducer. The purification steps are as follows: dissolve the lower layer product obtained by centrifugation in 200 mL of deionized water, add 50 mL of ethanol to precipitate the product, then centrifuge. Repeat the above steps 3 times, freeze-dry (-35℃, 48 h) to obtain a white solid, and pulverize it to obtain the hyperbranched polymer filtration loss reducer.

[0081] Comparative Preparation Example 1

[0082] A method for preparing modified clay is described in Preparation Example 1, except that in step 1), the 1:1 type clay mineral is replaced with bentonite to obtain modified clay.

[0083] Comparative Preparation Example 2

[0084] A method for preparing a polymer flow modifier is as described in Preparation Example 2, except that octadecyldimethylallylammonium chloride is not added in step 1), thus obtaining the polymer flow modifier.

[0085] Comparative preparation example 3

[0086] A method for preparing a linear polymer filtration loss reducer is as described in Preparation Example 3, except that:

[0087] Add 150 parts water, 10 parts N,N-dimethylacrylamide, 5 parts (3-acrylamidopropyl)trimethylammonium chloride and 2 parts methyl allyl alcohol polyoxyethylene ether (average molecular weight 2000) to a three-necked flask, stir until completely dissolved, add 0.1 parts ammonium persulfate, heat to 65°C and react with nitrogen gas for 2 hours; other conditions are the same as in Preparation Example 3, to obtain a linear polymer filtration loss reducer.

[0088] The modified clay shearing agent, hydrophobic associating polymer flow pattern modifier, and hyperbranched polymer filtration loss reducer used in the examples were prepared according to Preparation Examples 1-3, respectively.

[0089] The blocking agents used in the examples and comparative examples were prepared according to the method of Example 1 in Chinese patent document CN115160513A.

[0090] The cementitious sealing agents used in the examples and comparative examples were prepared according to the method of Example 1 in Chinese Patent Document CN114716984A.

[0091] Example 1

[0092] A water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters comprises the following raw materials in parts by weight: 100 parts water, 2 parts modified clay shearing agent, 3 parts hydrophobic associating polymer flow modifier, 5 parts plugging agent, 4 parts hyperbranched polymer filtration reducer, and 2 parts cemented plugging wall-solidifying agent.

[0093] The preparation method of the above-mentioned water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters includes the following steps:

[0094] Water was added to a high-speed mixing cup, and modified clay shearing agent was added under low-speed stirring for 30 hours. A hydrophobic associating polymer flow modifier was added, and the mixture was stirred at high speed for 20 minutes. A plugging agent was added, and the mixture was stirred at high speed for 20 minutes. A hyperbranched polymer filtration reducer was added, and the mixture was stirred at high speed for 20 minutes. A cemented plugging wall-stabilizing agent was added, and the mixture was stirred at high speed for 20 minutes to prepare a 10,000-meter deep-ground oil and gas wall-stabilizing water-based drilling fluid F1. The low-speed stirring speed was 2000 r / min, and the high-speed stirring speed was 10000 r / min.

[0095] Example 2

[0096] A water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters comprises the following raw materials in parts by weight: 100 parts water, 5 parts modified clay shearing agent, 4 parts hydrophobic associating polymer flow modifier, 3 parts plugging agent, 2 parts hyperbranched polymer filtration loss reducer, and 1 part cemented plugging wall-solidifying agent.

[0097] Other raw materials and drilling fluid preparation methods are the same as in Example 1, and F2, a water-based drilling fluid for solidifying the wall of oil and gas at a depth of 10,000 meters, is obtained.

[0098] Example 3

[0099] A water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters comprises the following raw materials in parts by weight: 100 parts water, 1 part modified clay shearing agent, 2 parts hydrophobic associating polymer flow modifier, 8 parts plugging agent, 5 parts hyperbranched polymer filtration loss reducer, and 3 parts cemented plugging wall-solidifying agent.

[0100] Other raw materials and drilling fluid preparation methods are the same as in Example 1, and F3, a water-based drilling fluid for solidifying the wall of oil and gas at a depth of 10,000 meters, is obtained.

[0101] Comparative Example 1

[0102] A water-based drilling fluid is described in Example 1, except that no hydrophobic associative polymer flow modifier is added; the other raw material composition is the same as in Example 1.

[0103] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the step of adding hydrophobic associative polymer flow modifier is omitted; water-based drilling fluid DF1 is obtained.

[0104] Comparative Example 2

[0105] A water-based drilling fluid is described in Example 1, except that: no hyperbranched polymer filtration loss reducer is added; the other raw material composition is the same as in Example 1.

[0106] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the step of adding hyperbranched polymer filtration loss reducer is omitted; water-based drilling fluid DF2 is obtained.

[0107] Comparative Example 3

[0108] A water-based drilling fluid is described in Example 1, except that no plugging agent is added; the other raw material composition is the same as in Example 1.

[0109] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the step of adding a plugging agent is omitted; water-based drilling fluid DF3 is obtained.

[0110] Comparative Example 4

[0111] A water-based drilling fluid is described in Example 1, except that no cementing and plugging wall-stabilizing agent is added; the other raw material composition is the same as in Example 1.

[0112] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the step of adding a cementing and plugging wall-stabilizing agent is omitted; water-based drilling fluid DF4 is obtained.

[0113] Comparative Example 5

[0114] A water-based drilling fluid is prepared as described in Example 1, except that the modified clay shearing agent is replaced with the modified clay prepared in Comparative Preparation Example 1; the water-based drilling fluid DF5 is thus prepared.

[0115] Comparative Example 6

[0116] A water-based drilling fluid was prepared as described in Example 1, except that the hydrophobic associative polymer flow modifier was replaced with the polymer flow modifier prepared in Comparative Preparation Example 2; the water-based drilling fluid DF6 was thus prepared.

[0117] Comparative Example 7

[0118] A water-based drilling fluid was prepared as described in Example 1, except that the hyperbranched polymer filtration reducer was replaced with the linear polymer filtration reducer prepared in Comparative Preparation Example 3; the water-based drilling fluid DF7 was thus prepared.

[0119] Experimental Example 1

[0120] Take 400 mL of each of the above drilling fluids F1-F3 and DF1-DF7, and weigh them with barite to a density of 1.5 g / cm³. 3After adding saturated salt (36% NaCl) and stirring at 5000 rpm for 20 minutes, the mixture was poured into an aging tank and placed in a roller furnace. It was then rolled at 240℃ for 16 hours. After cooling to room temperature, it was stirred at 5000 rpm for another 20 minutes. The apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), dynamic shear force (YP, Pa), and API filtration loss (FL) of the drilling fluid were determined according to the petroleum and natural gas industry standard GB / T 16783.1-2014 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids". API High temperature and high pressure filtration loss FL HTHP (240℃), the results are shown in Table 1.

[0121] Table 1 Drilling Fluid Performance Tests

[0122]

[0123] The above data shows that the deep-sea oil and gas wall-solidifying water-based drilling fluid of this invention has good rheological and filtration properties, with a high-temperature and high-pressure filtration loss of only 10.2 mL under 240℃ high-temperature and saturated salt conditions. The lack of key components or incorrect preparation methods for key materials can lead to a significant decrease in drilling fluid performance, proving that only drilling fluid prepared according to the raw materials, proportions, and preparation methods disclosed in the patent can exhibit excellent performance.

[0124] Experimental Example 2

[0125] Drilling fluids F1-F3 and DF1-DF7 were tested for their sand bed plugging and core plugging performance.

[0126] Take 400 mL of drilling fluids F1-F3 and DF1-DF7 respectively, and weigh them with barite to a density of 1.5 g / cm³. 3 Add saturated salt (36% NaCl), stir at 5000 rpm for 20 min, then pour into an aging tank, place in a roller furnace, and roll at 240℃ for 16 h. After cooling to room temperature, stir at 5000 rpm for 20 min to obtain the drilling fluid to be tested.

[0127] The instrument used for the sand bed filtration loss experiment was a visual medium-pressure sand bed plugging instrument. The sand used had a particle size of 80-100 mesh. The specific steps were as follows: 350 mL of sand was loaded into the sand filter tube and filled evenly; 200 mL of the drilling fluid to be tested was added to the top of the sand, and the cap was tightened and sealed with a sealing ring; a graduated cylinder of a certain specification was placed below the sand filter tube to measure the filtration loss. First, the main gas valve of the nitrogen cylinder was opened to provide a gas source. When the value of the pressure gauge connected to the upper end of the cap increased to 100 psi and stabilized, the valve between the pressure gauge and the cap was opened to allow air to pass through. After a stopwatch timed for 30 minutes, the filtration loss in the graduated cylinder was recorded (the filtration loss is the sand bed penetration depth or filtration volume). The results are shown in Table 2.

[0128] The core plugging rate was tested as follows: Using a core flow tester, the initial positive standard brine permeability K1 of the rock sample was determined using a drilling fluid contamination holder. Then, the core contamination holder was removed and connected to a drilling fluid high-temperature, high-pressure dynamic integrated tester. The rock sample was plugged with the aforementioned drilling fluid at a temperature of 80℃, a pressure differential of 3.5 MPa, a confining pressure of 5 MPa, and a shear rate of 150 s⁻¹. -1 After 30 minutes of damage, the core contamination holder was removed and connected to a core flow tester to measure the core's forward standard brine permeability K2. The core plugging rate was:

[0129]

[0130] The test results are shown in Table 2.

[0131] Table 2 Drilling Fluid Pouring Performance Test

[0132]

[0133] As can be seen from Table 2, the water-based drilling fluid for solidifying the wall of deep-sea oil and gas wells of the present invention has good plugging performance, with a sand bed invasion depth as low as 0.7 cm and a core plugging rate of 96.9%.

[0134] Experimental Example 3

[0135] The inhibition and wall-stabilizing properties of drilling fluids F1-F3 and DF1-DF7 were tested.

[0136] Sichuan pine forest red mudstone and shale were selected as the test rocks.

[0137] Take 30 grams of 10-mesh shale cuttings and put them into a molding press (D=15mm). Add 3 mL of distilled water and press for 5 minutes under 2 Pa conditions. Take out the core and soak it in different drilling fluids for 24 hours. Observe the integrity of the core. The results are shown in Table 3.

[0138] Shale was crushed, and shale particles of 6-10 mesh were screened. The particles were dried at 80°C for 6 hours in a 202-0A type electric thermostatic drying oven. After cooling in the desiccator for 2 hours, rolling recovery rate experiments were conducted in 400 mL of the above drilling fluids F1-F3 and DF1-DF7 (hot rolling at 240°C for 16 hours). The experimental results are shown in Table 3.

[0139] Table 3 Drilling fluid inhibition and wall-stabilizing performance tests

[0140]

[0141] As can be seen, the water-based drilling fluid for oil and gas solidification at depths of 10,000 meters of the present invention has good inhibition and solidification properties, can effectively maintain the stability of artificial shale core molds, and achieves a shale recovery rate of up to 97.1%.

[0142] Test Example 4

[0143] Long-term aging tests were conducted on drilling fluids F1-F3.

[0144] Take 400 mL of drilling fluid F1-F3 respectively and add barite to make the weight up to 1.5 g / cm³. 3 Saturated salt (36% NaCl) was added, and the mixture was stirred at 5000 rpm for 20 minutes. It was then transferred to an aging tank and placed in a roller furnace. After constant temperature rolling at 240℃ for 3, 5, and 7 days, the mixture was removed, cooled to room temperature, and stirred again at 5000 rpm for 20 minutes to obtain the drilling fluid to be tested. Then, according to the petroleum and natural gas industry standard GB / T 16783.1-2014 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids", the apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), dynamic shear force (YP, Pa), and API filtration loss (FL) of the above-mentioned drilling fluid were determined. API High temperature and high pressure filtration loss FL HTHP (240℃), the results are shown in Table 4.

[0145] Table 4. Long-term aging test of drilling fluid

[0146]

[0147] As shown in Table 4, the viscosity of the drilling fluid system decreased with increasing aging time, but it still maintained good shear strength, indicating that the drilling fluid still possesses good network structure strength. Moreover, the drilling fluid consistently maintained a low filtration loss; the high-temperature and high-pressure filtration loss after aging at 240℃ for 7 days was only 17.0 mL, indicating that the drilling fluid has long-term stability.

[0148] In summary, the water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters of this invention can maintain good rheological, filtration, plugging and inhibition properties for a long time under high temperature and high salinity conditions, thus achieving a strong wall-solidifying effect and meeting the needs of oil and gas drilling at depths of 10,000 meters.

[0149] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of 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 protection scope of the present invention.

[0150] 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 describe the various possible combinations separately.

[0151] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters, characterized in that, The raw materials contain the following parts by weight: 100 parts water, 1-5 parts modified clay cutting agent, 2-4 parts hydrophobic associating polymer flow modifier, 3-8 parts plugging agent, 2-5 parts hyperbranched polymer filtration loss reducer, and 1-3 parts cementing and plugging wall-stabilizing agent. The modified clay shearing agent was prepared according to the following method: (1) Mix magnesium aluminum hydrotalcite and 1:1 type clay minerals, add to an ethanol aqueous solution to obtain a dispersion; the magnesium aluminum hydrotalcite is carbonate-type magnesium aluminum hydrotalcite; the 1:1 type clay mineral is attapulgite composed of dioctahedral mica and dioctahedral montmorillonite in a 1:1 regular interlayer; the mass ratio of the magnesium aluminum hydrotalcite to the 1:1 type clay mineral is 0.1-0.3:1; (2) Add hexadecyltrimethylammonium bromide and dimethylaminopropylmethacrylamide to the dispersion obtained in step (1), stir evenly, heat to the reaction temperature under nitrogen protection, add initiator, and carry out constant temperature reaction under nitrogen protection; after the reaction is completed, centrifuge, wash, dry, and pulverize to obtain modified clay cutting agent; the mass of hexadecyltrimethylammonium bromide is 0.3-0.8% of the mass of the dispersion; the mass of dimethylaminopropylmethacrylamide is 0.5-1.5% of the mass of the dispersion; the reaction temperature is 55-65℃, and the constant temperature reaction time is 6-8h; the initiator is ammonium persulfate or potassium persulfate, and the mass of the initiator is 0.001-0.01% of the mass of the dispersion; The hydrophobic associative polymer flow modifier was prepared according to the following method: (I) An alkyl-substituted acrylamide, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, long-chain alkyl dimethyl allyl ammonium chloride, and 2-methyl-1-vinylimidazole are added to water and stirred until uniformly dispersed to obtain a monomer solution; wherein the alkyl-substituted acrylamide is N,N-diethylacrylamide; wherein the long-chain alkyl dimethyl allyl ammonium chloride is octadecyl dimethyl allyl ammonium chloride; wherein the molar ratio of the alkyl-substituted acrylamide, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, long-chain alkyl dimethyl allyl ammonium chloride, and 2-methyl-1-vinylimidazole is 1:0.2-0.4:0.05-0.15:0.05-0.15; (II) Nitrogen gas is introduced into the monomer solution obtained in step (I), the temperature is raised to a first temperature, phenyltriethoxysilane is added, and the mixture is stirred until dissolved. The temperature is then raised to a second temperature, and azobisisobutylamidine hydrochloride and sodium bisulfite are added to initiate the reaction. The reaction is carried out under constant temperature with nitrogen gas. After the reaction is completed, the mixture is washed and dried to obtain a hydrophobic associative polymer flow modifier. The first temperature is 40-50℃; the mass of the phenyltriethoxysilane is 0.05-0.15% of the total mass of the monomer; the second temperature is 70-80℃; and the constant temperature reaction time is 4-6 hours. The hyperbranched polymer filtration loss reducer was prepared according to the following method: (i) Under nitrogen protection, trimethylolpropane is heated and melted; then a methanol solution of potassium methoxide is added to carry out the reaction; after the reaction is completed, excess methanol is removed, the temperature is raised to 90-100℃, glycidyl ether is added, and the reaction is carried out at an isothermal temperature to obtain hyperbranched glycidyl ether; the mass ratio of potassium methoxide to trimethylolpropane is 0.1-0.2:1; the mass ratio of glycidyl ether to trimethylolpropane is 20-30:

1. (ii) N,N-dimethylacrylamide, (3-acrylamidopropyl)trimethylammonium chloride, methyl allyl alcohol polyoxyethylene ether, and the hyperbranched glycidyl ether obtained in step (ii) are added to water and stirred at 40-45°C under nitrogen protection until completely dissolved. Then, an aqueous solution of cerium ammonium nitrate is added to carry out the reaction. After the reaction is completed, ethanol is added to the reaction solution for precipitation. After centrifugation, the lower layer product is purified to obtain a hyperbranched polymer filtration loss reducer. The mass ratio of N,N-dimethylacrylamide, (3-acrylamidopropyl)trimethylammonium chloride, methyl allyl alcohol polyoxyethylene ether, and hyperbranched glycidyl ether is 10:4-6:1-3:0.05-0.

15. The concentration of the aqueous solution of cerium ammonium nitrate is 0.1-0.3 wt%, and the mass ratio of the aqueous solution of cerium ammonium nitrate to N,N-dimethylacrylamide is 4-6:

10. The reaction temperature is 60-70°C, and the reaction time is 1-3 h. The blocking agent was prepared according to the following method: 1) Weigh 5 parts of 2-acrylamide-2-methylpropanesulfonic acid, add it to a flask containing 130 parts of water, stir until fully dispersed, adjust the pH to 7-8, then add 0.3 parts of sodium dodecylbenzenesulfonate, and stir until fully dispersed; 2) Add 1 part of KH570 modified nano silica to the liquid in step 1), stir for 10 minutes, and then ultrasonically disperse for 30 minutes to obtain solution a; 3) Weigh 15 parts of styrene and 2 parts of divinylbenzene, stir until fully mixed, and then wash away the polymerization inhibitor with NaOH solution to obtain solution b; 4) Under high-speed stirring, add solution b dropwise to solution a, and then add 0.01 parts of RAFT reagent N,N'-diethyldi... 5) Add the liquid from step 4) to the flask, keep stirring, and deoxygenate with nitrogen for 30 minutes; 6) Heat to 70℃, add 0.15 parts of initiator potassium persulfate, and react with nitrogen for 6 hours; 7) After the reaction is complete, keep stirring, stop heating, and after the temperature drops to 30-40℃, pour the contents out of the flask. The resulting product is the sealing agent; KH570 modified nano silica is prepared by the following method: 1) Take 0.3g of sodium dodecyl sulfate, add it to 100g of water and stir for 15 minutes, add 10g of nano silica under mechanical stirring, and ultrasonically disperse for 30 minutes; 2) Transfer the above liquid to a three-necked flask, add 1.8g of KH570 dropwise under stirring, heat to 70℃, and stir for 7 hours; 3) After the reaction is complete, cool down, filter the above liquid, wash the filtered solid with anhydrous ethanol, and dry it to obtain KH570 modified nano silica; The cementing and sealing wall-fixing agent was prepared according to the following method: 2.5g of modified silica, 15g of acrylamide, 3.5g of acrylic acid, 1.5g of sodium p-styrene sulfonate, 2.5g of dimethyldiallyl ammonium chloride, 0.2g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 5g of dopamine hydrochloride were added to a flask containing 150g of water and stirred until fully dispersed; the flask was heated in a water bath to 60℃, and the mixture was kept stirred and heated, and oxygen was removed with nitrogen for 30 minutes; 0.35g of V50 was added to the flask, and the reaction was maintained for 4 hours; after the reaction was completed, the viscous product was taken out, washed three times with acetone, dried and pulverized to obtain the wall-fixing agent; the modified silica was prepared according to the following method: 1) 15g of nano silica was weighed and added to 100g of anhydrous ethanol, and the nano silica was fully dispersed by magnetic stirring to obtain dispersion system A; 2) 1.5g of... KH570 was added to 100g of a water / anhydrous ethanol system and magnetically stirred to fully disperse KH570, resulting in dispersion system B. The water / anhydrous ethanol dispersion system was prepared by uniformly mixing water and anhydrous ethanol at a volume ratio of 1:

9. 3) Dispersion system A and dispersion system B were poured into a flask, the pH was adjusted to 8.5 with triethylamine, 0.2 parts by weight of phenothiazine was added, and the mixture was refluxed at 60°C for 4 hours. 4) After the reaction was completed, the reaction product was removed and filtered. The powdered product was washed with ethanol and filtered again. The washing was repeated 2-3 times. The product was then vacuum dried at room temperature or air-dried at room temperature to obtain modified silica.

2. The water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters as described in claim 1, characterized in that, The chemical composition of the magnesium aluminum hydrotalcite mentioned in step (1) is Mg6Al2(OH). 16 (CO3)·4H2O; the volume ratio of deionized water to anhydrous ethanol in the ethanol aqueous solution is 1-3:1; the total mass concentration of magnesium aluminum hydrotalcite and 1:1 type clay minerals in the dispersion is 5-10%.

3. The water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters as described in claim 1, characterized in that, The washing in step (2) involves washing the solid obtained by centrifugation with deionized water 3-5 times; the drying involves drying at 80-100℃ for 8-12 hours.

4. The water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters as described in claim 1, characterized in that, The concentration of the monomer solution in step (I) is 20-40 wt%.

5. The water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters as described in claim 1, characterized in that, In step (II), the mass of azobisisobutylamidine hydrochloride is 0.1-1% of the total mass of the monomers; the mass of sodium bisulfite is 0.05-0.15% of the total mass of the monomers; the washing step involves washing the product obtained from the reaction with acetone 3-5 times; and the drying step involves drying at 80-100℃ for 8-12 hours.

6. The water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters as described in claim 1, characterized in that, The heating mentioned in step (i) is heating to 70-80°C; the potassium methoxide methanol solution is obtained by dissolving potassium methoxide in methanol, and the mass ratio of potassium methoxide to methanol is 0.5-0.7:1; In step (i), the temperature for adding potassium methoxide to the methanol solution is 70-80℃, and the reaction time is 20-40 min; after the reaction is completed, excess methanol in the reaction system is removed by vacuuming. The glycidol addition rate in step (i) is 0.1-0.2 mL / min; the isothermal reaction time after adding glycidol is 4-6 h.

7. The water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters as described in claim 1, characterized in that, The mass ratio of N,N-dimethylacrylamide to water in step (ii) is 1:10-20; the average molecular weight of the methyl allyl alcohol polyoxyethylene ether is 1000-4000. The purification step described in step (ii) is as follows: after dissolving the lower layer product obtained by centrifugation in water, ethanol is added for precipitation, followed by centrifugation. The above steps are repeated 2-3 times, and then the product is freeze-dried and pulverized to obtain the hyperbranched polymer filtration loss reducer.

8. The method for preparing the water-based drilling fluid for solidifying the wall of oil and gas wells at depths of 10,000 meters as described in claim 1, characterized in that, The steps include the following: Add the modified clay cutting agent to water and stir for more than 24 hours. Then add the hydrophobic associating polymer flow modifier, plugging agent, hyperbranched polymer filtration reducer and cementing plugging wall solidifying agent, and stir evenly to obtain the wall solidifying water-based drilling fluid for oil and gas at a depth of 10,000 meters.

9. The method for preparing the 10,000-meter deep-ground oil and gas wall-solidifying water-based drilling fluid according to claim 8, characterized in that, The specific preparation method includes the following steps: Water was added to a high-speed mixing cup, and modified clay shearing agent was added under low-speed stirring for more than 24 hours. A hydrophobic associating polymer flow modifier was added, and the mixture was stirred at high speed for 20 minutes. A plugging agent was added, and the mixture was stirred at high speed for 20 minutes. A hyperbranched polymer filtration reducer was added, and the mixture was stirred at high speed for 20 minutes. A cementing and plugging wall-stabilizing agent was added, and the mixture was stirred at high speed for 20 minutes to prepare a water-based drilling fluid for solidifying the wall of oil and gas wells at a depth of 10,000 meters. The low-speed stirring speed was 1000-3000 r / min, and the high-speed stirring speed was 8000-10000 r / min.

10. The application of the water-based drilling fluid with wall-stabilizing properties for deep-sea oil and gas formations as described in claim 1 in the drilling process of deep and ultra-deep oil and gas formations, characterized in that... Used to maintain the stability of the wellbore of oil and gas wells, the deep and ultra-deep oil and gas formations are formations tens of thousands of meters deep.

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