An anti-220 deg. c saturated salt environment-friendly water-based drilling fluid and a preparation method and application thereof

Abstract

The application provides an anti-220 DEG C saturated salt environment-friendly water-based drilling fluid and a preparation method and application thereof.The anti-220 DEG C saturated salt environment-friendly water-based drilling fluid comprises the following raw materials in parts by weight: 100 parts of water, 1-4 parts of a composite soil cutting agent, 0.2-0.6 parts of sodium hydroxide, 3-6 parts of an anti-high-temperature and anti-salt zwitterionic polymer, 2-4 parts of an anti-high-temperature and anti-salt anionic polymer, 3-5 parts of an alcohol amine inhibitor, 6-10 parts of organic-inorganic hybrid microsphere plugging agent, 2-4 parts of a strong adsorption anti-sloughing plugging agent, 3-4 parts of a composite oil lubricant, and 0.5-1 parts of a system stabilizer.The water-based drilling fluid can maintain good rheological properties, filtration loss, plugging and anti-sloughing properties under the condition of 220 DEG C or above, saturated sodium chloride and 3% calcium chloride.The drilling fluid system does not contain sulfonated materials, the treatment agent used has strong high-temperature and high-salt resistance, is not decomposed under high-temperature and high-salt conditions, and has good environmental protection performance.

Description

TECHNICAL FIELD

[0001] The application relates to an anti-220 DEG C saturated salt environment-friendly water-based drilling fluid and a preparation method and application thereof, and belongs to the technical field of drilling fluids. BACKGROUND

[0002] The deepest deep reservoirs in China (Tarim, Sichuan, Bohai Bay, etc.) are over 9000 m, and the bottom hole temperature is 180-260 DEG C. Ultra-deep wells have the characteristics of high temperature and pressure, complex geological conditions (most of which exist in salt and gypsum layers), and multiple pressure layer systems in the same open hole section. At present, the temperature resistance of the drilling fluid system is generally lower than 220 DEG C, and salt can greatly reduce the performance of the drilling fluid. In the drilling process, major safety accidents such as well collapse, sticking, well leakage, and blowout are often caused by drilling fluid failure, leading to high drilling costs and easy reservoir damage, which has a significant impact on deep oil and gas exploration and development. The development of an ultra-high temperature and high salt drilling fluid technology can improve drilling speed, reduce downhole complications, maintain the smooth progress of China's deep and ultra-deep oil and gas exploration and development strategic tasks, and lay a technical foundation for future deep drilling projects, which has important economic and social significance.

[0003] Oil-based drilling fluid has good performance in high-temperature stability, filtration reduction, and lubricity, but the fundamental defects of oil-based drilling fluid are the difficulty in obtaining raw materials, high economic cost, and serious environmental pollution. The common anti-high-temperature and high-salt water-based drilling fluid systems such as the three-sulfur system and the poly-sulfur system have toxic and poorly biodegradable treatment agents such as sulfonated lignite and sulfonated phenolic aldehyde resin, and the treatment agents decompose at high temperatures, releasing toxic and foul-smelling gases, which seriously pollute the environment and are difficult to use in areas with strict environmental requirements. It is an issue that cannot be ignored to improve the temperature and salt resistance of drilling fluid while maintaining environmental protection.

[0004] Chinese patent document CN104559968A discloses an anti-high-temperature water-based drilling fluid and a preparation method thereof. The system is composed of base slurry and high-softening-point asphalt liquid, and can only withstand 150 DEG C. Chinese patent document CN108641683A discloses an anti-high-temperature and high-salinity high-density water-based drilling fluid and its application, but the high-temperature and high-pressure filtration loss of the system under 220 DEG C saturated salt conditions is 21.6 mL, and the performance of the drilling fluid needs to be improved. A large amount of sulfonated materials are added to the system, and the environmental protection performance is poor. Chinese patent document CN114891489A discloses a non-sulfonated high-temperature-resistant water-based drilling fluid. The drilling fluid system does not contain sulfonated materials, is safe and environmentally friendly, and can withstand temperatures above 200 DEG C, but does not have salt resistance. The above drilling fluids cannot meet the requirements of temperature and salt resistance and environmental protection at the same time, and are difficult to support deep oil and gas drilling. SUMMARY

[0005] In view of the deficiencies of the prior art, especially in view of the fact that the temperature resistance and high salinity resistance of the water-based drilling fluid for deep formation is poor, and the environmental protection performance is poor, the present application provides an anti-220 DEG C saturated salt environmental protection type water-based drilling fluid and a preparation method and application thereof.The water-based drilling fluid of the present application can maintain good rheological, filtration, plugging and anti-sloughing performance under the condition of 220 DEG C or above, saturated sodium chloride and 3% calcium chloride.The drilling fluid system does not contain sulfonated materials, the treating agent used has strong high temperature and high salt resistance, does not decompose under high temperature and high salt conditions, and has good environmental protection performance.

[0006] The present application is realized by the following technical solutions:

[0007] An anti-220 DEG C saturated salt environmental protection type water-based drilling fluid, comprising the following raw material components by weight: water 100 parts, composite clay cutting agent 1-4 parts, sodium hydroxide 0.2-0.6 parts, high temperature and salt resistant zwitterionic polymer 3-6 parts, high temperature and salt resistant anionic polymer 2-4 parts, alcohol amine inhibitor 3-5 parts, organic-inorganic hybrid microsphere plugging agent 6-10 parts, strong adsorption anti-sloughing plugging agent 2-4 parts, composite oil lubricant 3-4 parts, and system stabilizer 0.5-1 part.

[0008] According to the present application, the composite clay cutting agent is obtained by mixing bentonite, attapulgite clay, diatomite, volcanic stone powder and sepiolite. Preferably, the mass ratio of bentonite, attapulgite clay, diatomite, volcanic stone powder and sepiolite is 1-3:1:0.1-1:0.1-1:0.1-1, preferably 2:1:0.5:0.5:0.5.

[0009] According to the present application, the high temperature and salt resistant zwitterionic polymer is prepared from the following raw materials by weight: N,N-dimethyl acrylamide 15-25 parts, 2-acrylamido-2-methylpropanesulfonic acid 5-15 parts, water 120-140 parts, methyl acryloyloxyethyl trimethyl ammonium chloride 10-20 parts, TPEG-2400 (methyl allyl polyoxyethylene ether-2400) 10-20 parts, 1-vinylimidazole 5-10 parts, N,N,N',N'-tetramethyl ethylenediamine 0.1-1 part, ammonium persulfate 0.1-0.5 part, and sodium bisulfite 0.01-0.1 part.

[0010] Preferably, the high temperature and salt resistant zwitterionic polymer comprises the following raw material components by weight: N,N-dimethyl acrylamide 20 parts, 2-acrylamido-2-methylpropanesulfonic acid 10 parts, water 130 parts, methyl acryloyloxyethyl trimethyl ammonium chloride 15 parts, TPEG-2400 15 parts, 1-vinylimidazole 8 parts, N,N,N',N'-tetramethyl ethylenediamine 0.5 part, ammonium persulfate 0.25 part, and sodium bisulfite 0.05 part.

[0011] Preferably, the preparation method of the anti-high-temperature and anti-salt amphoteric ion polymer comprises the following steps:

[0012] N,N-dimethyl acrylamide and 2-acrylamido-2-methylpropanesulfonic acid are fully dispersed in water, and the pH is adjusted to 7-8 by using 40-60 wt% NaOH aqueous solution; methacryloyloxyethyl trimethyl ammonium chloride, TPEG-2400, 1-vinylimidazole and N,N,N',N'-tetramethyl ethylenediamine are added and fully dispersed; a mixed initiator of ammonium persulfate and sodium bisulfite is added, and then stirring reaction is performed, followed by washing, drying and crushing to obtain the anti-high-temperature and anti-salt amphoteric ion polymer.

[0013] Preferably, the stirring reaction temperature is 60-70℃, and the stirring reaction time is 3-8h, and the stirring reaction is performed under nitrogen or argon protection.

[0014] According to the present application, preferably, the preparation method of the anti-high-temperature and anti-salt anionic polymer comprises the following steps:

[0015] (1) formaldehyde sodium sulfite is dissolved in deionized water, and a 30-50 wt% dimethylamine aqueous solution is added, and then stirring reaction is performed, and the precipitate is obtained by centrifugation and dried to obtain sodium (N,N-dimethylamino) methylene sulfonate;

[0016] (2) sodium (N,N-dimethylamino) methylene sulfonate is dissolved in an ethanol aqueous solution to obtain a sodium (N,N-dimethylamino) methylene sulfonate solution; 4-chloromethylstyrene is dissolved in anhydrous ethanol to obtain a 4-chloromethylstyrene solution; the sodium (N,N-dimethylamino) methylene sulfonate solution is added dropwise into the 4-chloromethylstyrene solution, stirring reaction is performed, and then filtration, washing, drying and crushing are performed to obtain a betaine monomer;

[0017] (3) N,N-dimethyl acrylamide, the betaine monomer and 2-acrylamido-2-methylpropanesulfonic acid are fully dispersed in deionized water, and a potassium persulfate initiator is added, and then free radical polymerization reaction is performed, followed by washing, drying and crushing to obtain the anti-high-temperature and anti-salt anionic polymer.

[0018] Preferably, in step (1), the mass ratio of formaldehyde sodium sulfite, deionized water and dimethylamine aqueous solution is 1:3-5:1-3, and preferably 1:4:2.

[0019] Preferably, in step (1), the stirring reaction temperature is 25-35℃, and the stirring reaction time is 70-75h.

[0020] Preferably, in step (2), the mass ratio of ethanol to water in the ethanol aqueous solution is 1:1.

[0021] Preferably, in step (2), the mass ratio of sodium (N,N-dimethylamino)methylenesulfonate, aqueous ethanol solution, 4-chloromethylstyrene, anhydrous ethanol is 6-8:90-110:3-8:30-50, preferably 7:100:5:40.

[0022] Preferably, in step (2), the dropping time is 5-10 min; the stirring reaction temperature is 40-50℃, and the stirring reaction time is 20-30h.

[0023] According to the present application, in step (2), the preparation route of the betaine monomer is as follows:

[0024]

[0025] Preferably, in step (3), the mass ratio of N,N-dimethylacrylamide, betaine monomer, 2-acrylamido-2-methylpropanesulfonic acid, deionized water and potassium persulfate is 18-25:6-10:6-10:90-110:0.1-0.3, preferably 21:8:8:100:0.15.

[0026] Preferably, in step (3), the free radical polymerization reaction temperature is 50-70℃, and the free radical polymerization reaction time is 4-8 hours.

[0027] According to the present application, preferably, the alcohol amine inhibitor is obtained by mixing polyether amine D230, polyether amine D400, polyethylene glycol 400, triethanolamine and pentaethylene hexamine.

[0028] Preferably, the mass ratio of polyether amine D230, polyether amine D400, polyethylene glycol 400, triethanolamine and pentaethylene hexamine is 1-3:1:1:0.1-0.5:0.1-0.3, preferably 2:1:1:0.3:0.2.

[0029] According to the present application, preferably, the organic-inorganic hybrid microsphere plugging agent is prepared from the following raw materials:

[0030] Sodium p-styrenesulfonate 5-15 parts, 2-acrylamido-2-methylpropanesulfonic acid 1-10 parts, water 100 parts, sodium dodecylbenzenesulfonate 0.1-0.5 parts, KH-570 modified nano-silica 1-3 parts, styrene 15-25 parts, initiator potassium persulfate 0.1-0.3 parts, crosslinking agent N,N'-methylene bisacrylamide 0.01-0.05 parts.

[0031] Preferably, the organic-inorganic hybrid microsphere plugging agent is prepared from the following raw materials:

[0032] Sodium p-styrenesulfonate 10 parts, 2-acrylamido-2-methylpropanesulfonic acid 5 parts, water 100 parts, sodium dodecyl benzene sulfonate 0.3 parts, KH-570 modified nano-silica 2 parts, styrene 20 parts, initiator potassium persulfate 0.2 parts, crosslinking agent N,N'-methylene bisacrylamide 0.02 parts.

[0033] According to the present application, the KH-570 modified nano-silica can be commercially available or prepared by the prior method.

[0034] Preferably, the preparation method of the organic-inorganic hybrid microsphere plugging agent comprises the following steps:

[0035] 1) fully disperse sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, sodium dodecyl benzene sulfonate and KH-570 modified nano-silica in water to obtain solution a;

[0036] 2) under stirring, dropwise add styrene into solution a, stir at room temperature for 20-40 minutes to form an emulsion; under stirring, add initiator potassium persulfate and crosslinking agent N,N'-methylene bisacrylamide, and then carry out stirring reaction to obtain the organic-inorganic hybrid microsphere plugging agent.

[0037] Further preferably, in step 2), the styrene further comprises the step of washing off MEHQ polymerization inhibitor by using NaOH aqueous solution with mass concentration of 40-60% before use.

[0038] Further preferably, in step 2), the stirring reaction temperature is 65-75°C, the stirring reaction time is 5-8h, and the stirring reaction is carried out under nitrogen or argon protection.

[0039] According to the present application, the strong adsorption anti-sloughing plugging agent is prepared by using the following raw materials in parts by weight: methyl methacrylate 5-15 parts, water 100-140 parts, N-vinyl pyrrolidone 1-10 parts, methyl methacrylate 10-30 parts, lauryl methacrylate 1-10 parts, divinyl benzene 1-5 parts, and initiator potassium persulfate 0.05-0.5 parts.

[0040] Preferably, the strong adsorption anti-sloughing plugging agent is prepared by using the following raw materials in parts by weight: methyl methacrylate 10 parts, water 120 parts, N-vinyl pyrrolidone 5 parts, methyl methacrylate 20 parts, lauryl methacrylate 5 parts, divinyl benzene 3 parts, and initiator potassium persulfate 0.1 parts.

[0041] Preferably, the preparation method of the strong adsorption anti-sloughing plugging agent comprises the following steps:

[0042] 1) fully disperse methyl methacrylate and N-vinyl pyrrolidone in water to obtain mixture 1;

[0043] 2) Methyl methacrylate, lauryl methacrylate and divinylbenzene are mixed thoroughly, and the polymerization inhibitor MEHQ is washed away using a 40-60% mass concentration NaOH aqueous solution to obtain a mixed solution 2;

[0044] 3) The mixed solution 2 is added dropwise into the mixed solution 1 under stirring, and a potassium persulfate initiator is added, and a strong adsorption anti-sloughing plugging agent is obtained through stirring reaction.

[0045] Further preferably, in step 3), the stirring reaction temperature is 60-70°C, the stirring reaction time is 4-6h, and the stirring reaction is carried out under nitrogen or argon protection.

[0046] According to the present application, preferably, the composite grease lubricant is obtained by mixing glyceryl oleate material, castor oil and SP-60. Preferably, the mass ratio of the glyceryl oleate material, castor oil and SP-60 is 1:1:0.1-1, preferably 1:1:0.5.

[0047] Preferably, the glyceryl oleate material is selected from one or a combination of two or more of glyceryl monooleate, glyceryl dioleate or glyceryl trioleate.

[0048] According to the present application, preferably, the system stabilizer is obtained by mixing Span-80, Tween-80 and OP-10. Preferably, the mass ratio of Span-80, Tween-80 and OP-10 is 1-3:1:1, preferably 2:1:1.

[0049] The above-mentioned preparation method of the 220°C saturated salt-resistant environment-friendly water-based drilling fluid comprises the following steps:

[0050] The composite soil cutting agent and sodium hydroxide are fully dispersed in water, and then the high-temperature-resistant and salt-resistant zwitterionic polymer, the high-temperature-resistant and salt-resistant anionic polymer, the alcohol amine inhibitor, the organic-inorganic hybrid microsphere plugging agent, the strong adsorption anti-sloughing plugging agent, the composite grease lubricant and the system stabilizer are sequentially added and fully dispersed to obtain the 220°C saturated salt-resistant environment-friendly water-based drilling fluid.

[0051] According to the present application, preferably, the preparation method of the 220°C saturated salt-resistant environment-friendly water-based drilling fluid comprises the following steps:

[0052] Water is added into a high-speed stirring cup, the composite soil cutting agent and sodium hydroxide are added under low-speed stirring, and the mixture is stirred at low speed for 24-48h; the high-temperature and salt-resistant zwitterionic polymer is added, and the mixture is stirred at high speed for 20min; the high-temperature and salt-resistant anionic polymer is added, and the mixture is stirred at high speed for 20min; the alcohol amine inhibitor is added, and the mixture is stirred at high speed for 20min; the organic-inorganic hybrid microsphere plugging agent is added, and the mixture is stirred at high speed for 20min; the strong adsorption anti-collapse plugging agent is added, and the mixture is stirred at high speed for 20min; the composite oil and fat lubricant is added, and the mixture is stirred at high speed for 20min; the system stabilizer is added, and the mixture is stirred at high speed for 20min, to obtain the 220 DEG C saturated salt-resistant environment-friendly water-based drilling fluid.

[0053] Preferably, the rotation speed of the low-speed stirring is 1000-3000r / min, and the rotation speed of the high-speed stirring is 8000-10000r / min.

[0054] The application of the above-mentioned 220 DEG C saturated salt-resistant environment-friendly water-based drilling fluid is applied in the drilling process of deep or super-deep layers, and plays the roles of balancing the formation pressure, plugging the formation cracks, lubricating the drill bit, carrying the rock cuttings, inhibiting the expansion of clay minerals, and stabilizing the well wall.

[0055] The technical features and beneficial effects of the present application are as follows:

[0056] (1) The 220 DEG C saturated salt-resistant environment-friendly water-based drilling fluid of the present application is composed of a composite soil cutting agent, a high-temperature and salt-resistant zwitterionic polymer, a high-temperature and salt-resistant anionic polymer, an alcohol amine inhibitor, an organic-inorganic hybrid microsphere plugging agent, a strong adsorption anti-collapse plugging agent, and a composite oil and fat lubricant. The composite soil cutting agent, the high-temperature and salt-resistant zwitterionic polymer, and the high-temperature and salt-resistant anionic polymer can synergistically enhance the effects of reducing the filtration loss and maintaining the good rheological properties of the drilling fluid under super-high temperature and high salinity conditions. The organic-inorganic hybrid microsphere plugging agent and the strong adsorption anti-collapse plugging agent further fill the formation cracks and pores, reduce the filtration loss, prevent the filtration liquid from invading the formation, and maintain the stability of the well wall. The alcohol amine inhibitor enhances the ability of the drilling fluid to inhibit the expansion of clay minerals, and the composite oil and fat lubricant improves the drilling speed of the drill bit and prevents the drill pipe from being stuck. Under the synergistic action of the various treatment agents, the drilling fluid can still maintain good rheological and filtration properties under high temperature and high salinity conditions, can effectively plug the formation cracks, inhibit the expansion of clay minerals, maintain the stability of the well wall, and prevent the occurrence of drilling accidents such as well wall collapse, necking, and drill pipe sticking.

[0057] (2) The composite soil cutting agent of the present application is prepared by compounding bentonite, attapulgite, diatomite, volcanic stone powder and sepiolite in a specific ratio. On the basis of the traditional high-temperature resistant well fluid cutting agent bentonite, attapulgite and sepiolite, volcanic stone powder which is resistant to high temperature and diatomite which is not sensitive to salt are added to further enhance the temperature and salt resistance of the cutting agent. The specific material ratio enables the composite soil to maintain good hydration and expansion under high temperature and high salt conditions, effectively adsorb the polymers in the drilling fluid, and enable the drilling fluid to maintain good rheological properties.

[0058] (3) The high-temperature and salt-resistant zwitterionic polymer in the drilling fluid system of the present application is a branched zwitterionic copolymer prepared by using N,N-dimethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyl trimethyl ammonium chloride, TPEG-2400, 1-vinylimidazole and N,N,N',N'-tetramethyl ethylenediamine as synthetic monomers. The cationic groups in the molecular chain can electrostatically adsorb clay particles with negative charges, and combine with the hydration of anionic groups to strengthen the hydration layer around the clay, thereby weakening the coalescence between clay particles, increasing the proportion of small clay particles, and enhancing the compactness of the mud cake, thereby reducing the filtration loss. There are many adsorption sites on it, and it can rotate in three-dimensional space, connecting with multiple clay particles or polymer chains in different directions, forming a firm three-dimensional network structure in the drilling fluid, improving the shear force of the drilling fluid and enhancing its carrying capacity. The three-dimensional network enables the drilling fluid clay to maintain good dispersion, and the drilling fluid still has good rheological properties and filtration properties after long-term high-temperature aging. The specific raw material composition of the present application enables the preparation of the high-temperature and salt-resistant zwitterionic polymer with the above-mentioned excellent properties. The absence or replacement of any monomer and the change of the ratio will reduce the performance.

[0059] (4) The high-temperature and salt-resistant anionic polymer of the present application is an anionic polymer prepared by free radical polymerization of N,N-dimethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and betaine monomer. The high-temperature and salt-resistant anionic polymer of the present application contains a specific amount and type of betaine monomer, which has both quaternary ammonium cationic groups and sulfonate groups, can make the polymer tightly adsorbed on the clay surface at high temperature, maintain the colloidal stability of the clay at high temperature and high salt, effectively plug the filtration channels in the mud cake, and reduce the filtration loss. The specific structure and amount of betaine monomer in the present application, combined with other raw materials, work together to prepare the high-temperature and salt-resistant anionic polymer with excellent performance of the present application. The absence or replacement of any monomer and the change of the ratio will reduce the performance.

[0060] (5) The organic-inorganic hybrid microsphere plugging agent in the drilling fluid of this invention has a flexible polymer soft shell with high elasticity and toughness, which can adapt to the size and shape of fractures in the formation and achieve efficient and dense filling. The sulfonic acid groups in the polymer soft shell molecular chain have strong hydration characteristics, and the benzene ring improves the molecule's resistance to high temperature and salt. The core is a rigid nano-silica that is resistant to temperature and salt, which serves as a supporting skeleton and increases the strength of the plugging agent. Under pressure differential, this plugging agent can reduce drilling fluid filtrate loss and fill and deposit around the well wall, forming a solid pressure-bearing plugging layer in conjunction with the rigid plugging agent, thereby preventing pressure transmission and filtrate intrusion. The plugging agent with the above-mentioned excellent performance of this invention is prepared from raw materials with a specific composition. Any absence or substitution of raw materials or changes in the ratio will reduce its performance.

[0061] (6) The main chain of the strong adsorption anti-collapse plugging agent in the drilling fluid of this invention is a long carbon chain composed of high bond energy C-C covalent bonds, which is not easily broken at high temperatures and not easily twisted at high salt conditions; moreover, the steric hindrance between the chains is large, and it can form a hydrophobic association structure in water, which improves the temperature and salt resistance of the plugging agent. The plugging agent molecular chain contains a large number of hydrophilic strong adsorption groups such as amide groups, which is beneficial to the dispersion of the plugging agent in the drilling fluid and its adsorption in the formation. The polymer microspheres (organic-inorganic hybrid microsphere plugging agent, strong adsorption anti-collapse plugging agent) can be well dispersed in the drilling fluid, can enter the leakage channel, automatically fill it, and form an anti-collapse plugging layer with anti-scouring and anti-penetration capabilities, enhancing the plugging performance of the drilling fluid under high temperature and high salt conditions and maintaining wellbore stability. The plugging agent with the above-mentioned excellent properties of this invention is prepared from the raw materials with the specific composition of this invention. Any absence or substitution of raw materials or changes in the ratio will reduce its performance.

[0062] (7) The drilling fluid of this invention incorporates an environmentally friendly composite grease lubricant that is resistant to high temperatures and insensitive to salinity, and a system stabilizer is added to enhance the stability of the drilling fluid in high-temperature and high-salinity environments, enabling the drilling fluid to maintain good performance even under these conditions. The superior effects of this invention can only be achieved through the specific composition of the composite grease lubricant and system stabilizer. Any deficiency or substitution of raw materials, or changes in the proportions, will reduce its performance.

[0063] (8) The polymer in the drilling fluid of the present invention has a unique molecular structure, which can form a strong three-dimensional network structure that is resistant to temperature and salt inside the drilling fluid. The drilling fluid clay can maintain good dispersion. After long-term high-temperature aging, the drilling fluid still has good rheological properties and filtration performance. The drilling fluid of the present invention can achieve adaptive sealing of the formation, forming a collapse-resistant sealing layer with anti-scouring and anti-penetration capabilities, reducing filtrate intrusion, and further reducing filtration loss. The drilling fluid of the present invention forms a microemulsion structure, which enhances the suspension of solid particles, maintains the stability of the drilling fluid, and enables the drilling fluid to be weighted to a higher density.

[0064] (9) The water-based drilling fluid of the present application can maintain good rheological properties, filtration loss, and plugging and anti-sloughing properties under the condition of 220℃ or above, saturated sodium chloride, and 3% calcium chloride. The components of the present application work together and synergistically to meet the needs of safe and efficient drilling in deep oil and gas formations, and are simple to configure, safe and environmentally friendly, and easy to maintain. The drilling fluid system of the present application can be applied in various drilling and production, and can achieve good results. The drilling fluid system does not contain sulfonated materials, and the treatment agent used has strong high-temperature and salt resistance, does not decompose under high-temperature and high-salt conditions, has good environmental protection performance, and can be widely used in areas with strict environmental protection requirements. The drilling fluid of the present application lays a technical foundation for the smooth progress of the strategic task of deep and ultra-deep oil and gas exploration and development in China, and for the future implementation of deep drilling engineering, and has important economic and social significance. DETAILED DESCRIPTION

[0065] The specific embodiments of the present application are further described below. According to the following examples, the present application can be better understood. However, it will be readily apparent to one of ordinary skill in the art that the specific materials, conditions and results described in the examples are illustrative only and are not intended to limit the present application as described in the claims. At the same time, in the following examples and comparative examples, unless otherwise specified, the materials used are commercially available, and the methods used are conventional methods in the art.

[0066] In the following preparation examples and examples, "parts" are all weight parts, unless otherwise specified.

[0067] Preparation Example 1

[0068] The preparation method of the high-temperature and salt-resistant zwitterionic polymer is as follows:

[0069] 1) 20 parts of N,N-dimethylacrylamide and 10 parts of 2-acrylamido-2-methylpropanesulfonic acid were added to 130 parts of water, and stirred at 300 rpm under magnetic stirring until fully dispersed, and the pH was adjusted to 7.5 using 50 wt% NaOH aqueous solution;

[0070] 2) 15 parts of methacryloyloxyethyl trimethylammonium chloride and 15 parts of TPEG-2400 were added in sequence, and stirred at 300 rpm under magnetic stirring until fully dispersed, and the liquid was transferred to a three-necked flask;

[0071] 3) The temperature was raised to 65℃, 8 parts of 1-vinylimidazole and 0.5 parts of N,N,N',N'-tetramethyl ethylenediamine were added, and fully stirred at 300 rpm under magnetic stirring until dispersed;

[0072] 4) After nitrogen for 20 min, add 0.25 parts of ammonium persulfate and 0.05 parts of sodium bisulfite mixed initiator to initiate the reaction, keep 300 rpm magnetic stirring at 65℃ constant temperature for 5h;

[0073] 3) After the reaction, the reaction product was washed with acetone 3 times, dried in an oven at 90℃ for 10h, then crushed, the obtained light yellow powder was the high temperature resistant and salt resistant zwitterionic polymer.

[0074] Preparation Example 2

[0075] The preparation method of the high temperature resistant and salt resistant anionic polymer is as follows:

[0076] 1) 5 parts of sodium formaldehyde sulfoxylate was dissolved in 20 parts of deionized water, 10 parts of dimethylamine aqueous solution (concentration of 40wt%) was added, and the reaction was stirred at 30℃ for 72h. After the reaction, the upper clear liquid was removed by centrifugation, and the light yellow precipitate was taken out and dried at 45℃ under vacuum for 12h to obtain sodium (N,N-dimethylamino) methylene sulfonate.

[0077] 2) 7 parts of sodium (N,N-dimethylamino) methylene sulfonate was dissolved in 100 parts of ethanol aqueous solution (ethanol and water in the ethanol aqueous solution were in a mass ratio of 1:1) to obtain solution 1. 5 parts of 4-chloromethylstyrene was dissolved in 40 parts of anhydrous ethanol to obtain solution 2; solution 1 was added dropwise into solution 2, the dropwise time was 8min, after the dropwise addition was completed, the reaction was carried out at 45℃ under 300rpm magnetic stirring for 24h, after the reaction was completed, the obtained solid was washed with acetonitrile 3 times, dried under vacuum at 60℃ for 12h, crushed to obtain betaine monomer.

[0078] 3) 21 parts of N,N-dimethylacrylamide, 8 parts of betaine monomer, and 8 parts of 2-acrylamido-2-methylpropanesulfonic acid were added to 100 parts of deionized water, stirred for 5min until fully dispersed, heated to 60℃, then 0.15 parts of initiator potassium persulfate was added, and free radical polymerization was carried out for 6h to obtain a viscous polymer crude product;

[0079] 4) The polymer crude product was washed with acetone 2 times, dried at 100℃ for 24h, crushed to obtain white powder, which was the high temperature resistant and salt resistant anionic polymer.

[0080] Preparation Example 3

[0081] The preparation method of the organic-inorganic hybrid microsphere plugging agent is as follows:

[0082] 1) 10 parts of sodium p-styrenesulfonate and 5 parts of 2-acrylamido-2-methylpropanesulfonic acid were weighed and added to 100 parts of water, stirred at 300rpm until fully dispersed, then 0.3 parts of sodium dodecylbenzenesulfonate was added and stirred until fully dispersed,

[0083] 2) To the liquid obtained in step 1), 2 parts of KH-570 modified nano-silica were added, after dispersion under stirring at 300 rpm, ultrasonic dispersion was carried out for 30 minutes, the ultrasonic temperature was controlled below 40℃, to obtain solution a;

[0084] 3) 20 parts of styrene were weighed, the MEHQ polymerization inhibitor was washed away using 50% NaOH aqueous solution, to obtain solution b; under high speed stirring at 500 rpm or above, solution b was added dropwise into solution a, room temperature stirring was maintained for 30 minutes to form an emulsion;

[0085] 4) The emulsion obtained in 3) was transferred into a three-necked flask, stirring was maintained, and oxygen was removed using nitrogen for 30 minutes; the temperature was increased to 70℃, 0.2 parts of initiator potassium persulfate and 0.02 parts of crosslinking agent N,N'-methylene bisacrylamide were added, nitrogen was bubbled for stirring reaction for 7h; after the reaction was completed, stirring was maintained, heating was stopped, and when the temperature dropped to 20-30℃, the organic-inorganic hybrid microspheres plugging agent was obtained.

[0086] Preparation Example 4

[0087] The preparation method of the strong adsorption anti-collapse plugging agent is as follows:

[0088] 1) 10 parts of methacrylic acid were weighed and added into 120 parts of water, stirring was carried out until it was fully dispersed, then 5 parts of N-vinyl pyrrolidone were added, stirring was carried out until it was fully dispersed at 300 rpm; stirring was maintained, and oxygen was removed using nitrogen for 30 minutes, to obtain mixture 1;

[0089] 2) 20 parts of methyl methacrylate, 5 parts of lauryl methacrylate and 3 parts of divinylbenzene were weighed, stirring was carried out until they were mixed well, then the polymerization inhibitor MEHQ was washed away using 50% NaOH aqueous solution, to obtain mixture 2;

[0090] 4) Under stirring, mixture 2 was added dropwise into mixture 1, stirring was maintained at 500 rpm, and the temperature was increased to 65℃, 0.1 parts of initiator potassium persulfate was added, nitrogen was bubbled for stirring reaction for 5h;

[0091] 5) After the reaction was completed, stirring was maintained, heating was stopped, and when the temperature dropped to 30-40℃, the strong adsorption anti-collapse plugging agent was obtained.

[0092] Preparation Comparative Example 1

[0093] The preparation method of the high temperature resistant and salt resistant zwitterionic polymer was the same as that in Preparation Example 1, except that TPEG-2400 was not added; the other steps and conditions were the same as those in Preparation Example 1.

[0094] Preparation Comparative Example 2

[0095] The preparation method of the high-temperature resistant and salt resistant zwitterionic polymer is the same as that in Preparation Example 1, except that TPEG-2400 is replaced by HPEG-2400; and other steps and conditions are the same as those in Preparation Example 1.

[0096] Preparation of Comparative Example 3

[0097] The preparation method of the high-temperature resistant and salt resistant anionic polymer is the same as that in Preparation Example 2, except that the betaine monomer is replaced by methacryloyl ethyl sulfobetaine; and other steps and conditions are the same as those in Preparation Example 2.

[0098] Preparation of Comparative Example 4

[0099] The preparation method of the high-temperature resistant and salt resistant anionic polymer is the same as that in Preparation Example 2, except that, in step (2), 4-chloromethylstyrene is replaced by 2-chloromethylstyrene; and other steps and conditions are the same as those in Preparation Example 2.

[0100] Preparation of Comparative Example 5

[0101] The preparation method of the organic-inorganic hybrid microsphere plugging agent is the same as that in Preparation Example 3, except that, in step 1), 2-acrylamido-2-methylpropanesulfonic acid is not added; and other steps and conditions are the same as those in Preparation Example 3.

[0102] Preparation of Comparative Example 6

[0103] The preparation method of the organic-inorganic hybrid microsphere plugging agent is the same as that in Preparation Example 3, except that, in step 1), 2-acrylamido-2-methylpropanesulfonic acid is replaced by acrylamide; and other steps and conditions are the same as those in Preparation Example 3.

[0104] Example 1

[0105] An environmentally friendly water-based drilling fluid resistant to 220°C saturated salt, comprising the following raw materials in parts by weight: water 100 parts, composite clay cutting agent 2 parts, sodium hydroxide 0.4 parts, high-temperature resistant and salt resistant zwitterionic polymer obtained in Preparation Example 1 4 parts, high-temperature resistant and salt resistant anionic polymer obtained in Preparation Example 2 2 parts, alcohol amine inhibitor 3 parts, organic-inorganic hybrid microsphere plugging agent obtained in Preparation Example 3 8 parts, strong adsorption anti-sloughing plugging agent obtained in Preparation Example 4 2 parts, composite oil lubricant 3 parts, and system stabilizer 0.5 parts.

[0106] The composite soil cutting agent is obtained by mixing bentonite, attapulgite, diatomite, volcanic rock powder and sepiolite in a mass ratio of 2:1:0.5:0.5:0.5. The alcohol amine inhibitor is obtained by mixing polyetheramine D230, polyetheramine D400, polyethylene glycol 400, triethanolamine and pentaethylene hexamine in a mass ratio of 2:1:1:0.3:0.2. The composite oil and fat lubricant is obtained by mixing glycerol monooleate, castor oil and SP-60 in a mass ratio of 1:1:0.5. The system stabilizer is obtained by mixing Span-80, Tween-80 and OP-10 in a mass ratio of 2:1:1.

[0107] The preparation method of the above-mentioned 220℃-resistant saturated salt-resistant environment-friendly water-based drilling fluid comprises the following steps:

[0108] According to the above-mentioned proportion, water is added to a high-speed stirring cup, and the composite soil cutting agent and sodium hydroxide are added under low-speed stirring for 24 hours. The high-temperature-resistant and salt-resistant zwitterionic polymer is added and stirred at high speed for 20 minutes. The high-temperature-resistant and salt-resistant anionic polymer is added and stirred at high speed for 20 minutes. The alcohol amine inhibitor is added and stirred at high speed for 20 minutes. The organic-inorganic hybrid microsphere plugging agent is added and stirred at high speed for 20 minutes. The strong adsorption anti-sloughing plugging agent is added and stirred at high speed for 20 minutes. The composite oil and fat lubricant is added and stirred at high speed for 20 minutes. The system stabilizer is added and stirred at high speed for 20 minutes, thereby obtaining the 220℃-resistant saturated salt-resistant environment-friendly water-based drilling fluid F1.

[0109] The rotation speed of the low-speed stirring is 2000r / min, and the rotation speed of the high-speed stirring is 10000r / min.

[0110] Example 2

[0111] A 220℃-resistant saturated salt-resistant environment-friendly water-based drilling fluid comprises the following raw materials by weight: water 100 parts, composite soil cutting agent 4 parts, sodium hydroxide 0.6 parts, high-temperature-resistant and salt-resistant zwitterionic polymer obtained in preparation example 1 6 parts, high-temperature-resistant and salt-resistant anionic polymer obtained in preparation example 2 4 parts, alcohol amine inhibitor 5 parts, organic-inorganic hybrid microsphere plugging agent obtained in preparation example 3 10 parts, strong adsorption anti-sloughing plugging agent obtained in preparation example 4 4 parts, composite oil and fat lubricant 4 parts, and system stabilizer 1 part.

[0112] The other raw material types and the preparation method of the drilling fluid are the same as those in example 1. A 220℃-resistant saturated salt-resistant environment-friendly water-based drilling fluid F2 is prepared.

[0113] Example 3

[0114] An environmental-friendly water-based drilling fluid resistant to 220℃ saturated salt, comprising the following raw materials by weight: water 100 parts, composite clay cutting agent 1 part, sodium hydroxide 0.2 part, high-temperature and salt-resistant amphoteric ionic polymer obtained in Preparation Example 1 3 parts, high-temperature and salt-resistant anionic polymer obtained in Preparation Example 2 3 parts, alcohol amine inhibitor 4 parts, organic-inorganic hybrid microsphere blocking agent obtained in Preparation Example 3 6 parts, strong adsorption anti-sloughing blocking agent obtained in Preparation Example 4 3 parts, composite oil and fat lubricant 4 parts, and system stabilizer 0.8 part.

[0115] Other raw material types and the preparation method of the drilling fluid are the same as in Example 1. An environmental-friendly water-based drilling fluid resistant to 220℃ saturated salt F3 is prepared.

[0116] Example 4

[0117] An environmental-friendly water-based drilling fluid resistant to 220℃ saturated salt, as described in Example 1, except that the composite clay cutting agent is obtained by mixing bentonite, attapulgite, diatomite, volcanic stone powder and sepiolite in a mass ratio of 1:1:0.5:1:1; and other raw material compositions are the same as in Example 1.

[0118] The preparation method of the above water-based drilling fluid is as described in Example 1, and a water-based drilling fluid F4 is prepared.

[0119] Example 5

[0120] An environmental-friendly water-based drilling fluid resistant to 220℃ saturated salt, as described in Example 1, except that the composite oil and fat lubricant is obtained by mixing glycerol monooleate, castor oil and SP-60 in a mass ratio of 1:1:1; and other raw material compositions are the same as in Example 1.

[0121] The preparation method of the above water-based drilling fluid is as described in Example 1, and a water-based drilling fluid F5 is prepared.

[0122] Example 6

[0123] An environmental-friendly water-based drilling fluid resistant to 220℃ saturated salt, as described in Example 1, except that the glycerol monooleate in the composite oil and fat lubricant is replaced by glycerol dioleate; and other raw material compositions are the same as in Example 1.

[0124] The preparation method of the above water-based drilling fluid is as described in Example 1, and a water-based drilling fluid F6 is prepared.

[0125] Example 7

[0126] An environmental-friendly water-based drilling fluid resistant to 220℃ saturated salt, as described in Example 1, except that the system stabilizer is obtained by mixing Span-80, Tween-80 and OP-10 in a mass ratio of 1:1:1; and other raw material compositions are the same as in Example 1.

[0127] The water-based drilling fluid is prepared according to the method of Example 1, except that the step of adding the high-temperature-resistant and salt-resistant zwitterionic polymer is omitted, to obtain a water-based drilling fluid DF1.

[0128] Comparative Example 1

[0129] A water-based drilling fluid is prepared according to the method of Example 1, except that the high-temperature-resistant and salt-resistant zwitterionic polymer is not added, and the other raw materials are the same as in Example 1.

[0130] The water-based drilling fluid is prepared according to the method of Example 1, except that the step of adding the high-temperature-resistant and salt-resistant zwitterionic polymer is omitted, to obtain a water-based drilling fluid DF1.

[0131] Comparative Example 2

[0132] A water-based drilling fluid is prepared according to the method of Example 1, except that the high-temperature-resistant and salt-resistant anionic polymer is not added, and the other raw materials are the same as in Example 1.

[0133] The water-based drilling fluid is prepared according to the method of Example 1, except that the step of adding the high-temperature-resistant and salt-resistant anionic polymer is omitted, to obtain a water-based drilling fluid DF2.

[0134] Comparative Example 3

[0135] A water-based drilling fluid is prepared according to the method of Example 1, except that the organic-inorganic hybrid microsphere plugging agent is not added, and the other raw materials are the same as in Example 1.

[0136] The water-based drilling fluid is prepared according to the method of Example 1, except that the step of adding the organic-inorganic hybrid microsphere plugging agent is omitted, to obtain a water-based drilling fluid DF3.

[0137] Comparative Example 4

[0138] A water-based drilling fluid is prepared according to the method of Example 1, except that the strong adsorption anti-sloughing plugging agent is not added, and the other raw materials are the same as in Example 1.

[0139] The water-based drilling fluid is prepared according to the method of Example 1, except that the step of adding the strong adsorption anti-sloughing plugging agent is omitted, to obtain a water-based drilling fluid DF4.

[0140] Comparative Example 5

[0141] A water-based drilling fluid is prepared according to the method of Example 1, except that the composite grease lubricant and system stabilizer are not added, and the other raw materials are the same as in Example 1.

[0142] The water-based drilling fluid is prepared according to the method of Example 1, except that the step of adding the composite grease lubricant and system stabilizer is omitted, to obtain a water-based drilling fluid DF5.

[0143] Comparative Example 6

[0144] A water-based drilling fluid as described in Example 1, except that the high-temperature and salt-resistant zwitterionic polymer and the high-temperature and salt-resistant anionic polymer are replaced by 6 parts of a sulfonate copolymer fluid loss additive DSP-1; and the other raw material compositions are the same as in Example 1.

[0145] The preparation method of the water-based drilling fluid described above comprises the steps of:

[0146] Water is added into a high-speed stirring cup, the composite clay cutting agent and sodium hydroxide are added under low-speed stirring, and the low-speed stirring is performed for 24 hours; the sulfonate copolymer fluid loss additive DSP-1 is added, and high-speed stirring is performed for 20 minutes; the alcohol amine inhibitor is added, and high-speed stirring is performed for 20 minutes; the organic-inorganic hybrid microsphere plugging agent is added, and high-speed stirring is performed for 20 minutes; the strong adsorption anti-sloughing plugging agent is added, and high-speed stirring is performed for 20 minutes; the composite oil lubricant is added, and high-speed stirring is performed for 20 minutes; and the system stabilizer is added, and high-speed stirring is performed for 20 minutes, so as to obtain the water-based drilling fluid DF6.

[0147] The rotation speed of the low-speed stirring is 2000 r / min, and the rotation speed of the high-speed stirring is 10000 r / min.

[0148] Comparative Example 7

[0149] A water-based drilling fluid as described in Example 1, except that the high-temperature and salt-resistant zwitterionic polymer obtained in Preparation Example 1 is replaced by the high-temperature and salt-resistant zwitterionic polymer obtained in Comparative Preparation Example 1; and the other raw material compositions are the same as in Example 1.

[0150] The preparation method of the water-based drilling fluid is the same as in Example 1, and the water-based drilling fluid DF7 is obtained.

[0151] Comparative Example 8

[0152] A water-based drilling fluid as described in Example 1, except that the high-temperature and salt-resistant zwitterionic polymer obtained in Preparation Example 1 is replaced by the high-temperature and salt-resistant zwitterionic polymer obtained in Comparative Preparation Example 2; and the other raw material compositions are the same as in Example 1.

[0153] The preparation method of the water-based drilling fluid is the same as in Example 1, and the water-based drilling fluid DF8 is obtained.

[0154] Comparative Example 9

[0155] A water-based drilling fluid as described in Example 1, except that the high-temperature and salt-resistant anionic polymer obtained in Preparation Example 2 is replaced by the high-temperature and salt-resistant anionic polymer obtained in Comparative Preparation Example 3; and the other raw material compositions are the same as in Example 1.

[0156] The preparation method of the water-based drilling fluid is the same as in Example 1, and the water-based drilling fluid DF9 is obtained.

[0157] Comparative Example 10

[0158] A water-based drilling fluid was prepared according to the method of Example 1, except that the high-temperature and salt-resistant anionic polymer obtained in Preparation Example 2 was replaced by the high-temperature and salt-resistant anionic polymer obtained in Comparative Preparation Example 4, and the other raw materials were the same as in Example 1.

[0159] A water-based drilling fluid was prepared according to the method of Example 1, and a water-based drilling fluid DF10 was obtained.

[0160] Comparative Example 11

[0161] A water-based drilling fluid was prepared according to the method of Example 1, except that the organic-inorganic hybrid microspheres plugging agent obtained in Preparation Example 3 was replaced by the organic-inorganic hybrid microspheres plugging agent obtained in Comparative Preparation Example 5, and the other raw materials were the same as in Example 1.

[0162] A water-based drilling fluid was prepared according to the method of Example 1, and a water-based drilling fluid DF11 was obtained.

[0163] Comparative Example 12

[0164] A water-based drilling fluid was prepared according to the method of Example 1, except that the organic-inorganic hybrid microspheres plugging agent obtained in Preparation Example 3 was replaced by the organic-inorganic hybrid microspheres plugging agent obtained in Comparative Preparation Example 6, and the other raw materials were the same as in Example 1.

[0165] A water-based drilling fluid was prepared according to the method of Example 1, and a water-based drilling fluid DF12 was obtained.

[0166] Comparative Example 13

[0167] A water-based drilling fluid was prepared according to the method of Example 1, except that the composite clay drilling fluid was obtained by mixing bentonite, attapulgite, and diatomite at a mass ratio of 3:1:0.5, and the other raw materials were the same as in Example 1.

[0168] A water-based drilling fluid was prepared according to the method of Example 1, and a water-based drilling fluid DF13 was obtained.

[0169] Test Example 1

[0170] 400 mL of each of the drilling fluids F1-F3 and DF1-DF6 described above were taken, and barite was added to a weight of 1.6 g / cm3. 3, after adding 36wt% NaCl and 3wt% CaCl2, stirring at 5000r / min for 20min, loading into the aging tank, putting into the roller oven, after constant temperature rolling at 220℃ for 16h, taking out and cooling to room temperature, stirring at 5000rpm for 20min, then determining the apparent viscosity (AV, mPa.s), plastic viscosity (PV, mPa.s), dynamic shear (YP, Pa), API filtration loss FL API , high temperature and high pressure filtration loss FL HTHP (220℃), and the results are shown in Table 1.

[0171] Table 1: Drilling fluid performance test

[0172] Drilling fluid AV, mPa.s PV, mPa.s YP, Pa FL API mL FL HTHP220 °C, mL Fl 42 34.5 7.5 0.8 9.2 F2 48.5 38 10.5 0.4 8.4 F3 38.5 32.5 6 1.2 11.4 F4 41 34 7 1.0 10.2 F5 43 35 8 1.0 10.8 F6 41.5 34 7.5 0.8 10.0 F7 42 34 8 1.2 10.8 DF1 36 31 5 3.2 38.6 DF2 37 32.5 4.5 2.6 29.8 DF3 42 35 7 1.6 22.1 DF4 42.5 35 7.5 1.4 15.8 DF5 40 33 7 1.4 16.4 DF6 56 45 11 3.6 48.6 DF7 38 32 6 3.2 28.6 DF8 37 31.5 5.5 2.8 26.4 DF9 36 29.5 6.5 3.0 32.8 DF10 41.5 32 9.5 2.6 29.4 DF11 42 35 7 1.6 20.6 DF12 43 35.5 7.5 1.8 21.8 DF13 38 34 4 3.4 30.4

[0173] As can be seen from the data in Table 1, the anti-220℃ saturated salt environment-friendly water-based drilling fluid has good rheological property, low API filtration loss and HTHP filtration loss, and can effectively control the filtration into the formation; the anti-high temperature and salt amphoteric ionic polymer and the anti-high temperature and salt anionic polymer used in the drilling fluid have better performance than DSP-1, and the addition of the organic-inorganic hybrid microsphere plugging agent and the strong adsorption anti-sloughing plugging agent can significantly reduce the HTHP filtration loss, and the various treating agents can synergistically enhance the performance of the drilling fluid. The system stabilizer can improve the stability of the drilling fluid under high temperature and high salinity, and assist the core treating agent to maintain the performance of the drilling fluid.

[0174] Test Example 2

[0175] The drilling fluids F1-F3 and DF1-DF6 were subjected to sand bed plugging and core plugging performance tests.

[0176] 400mL of drilling fluids F1-F3 and DF1-DF6 were taken respectively, and barite was added to weigh 1.6g / cm 3 , after adding 36wt% NaCl and 3wt% CaCl2, stirring at 5000rpm for 20min, loading into the aging tank, putting into the roller oven, after constant temperature rolling at 220℃ for 16h, taking out and cooling to room temperature, stirring at 5000rpm for 20min, and then obtaining the drilling fluid to be tested.

[0177] The instrument used for the sand bed filtration experiment was a visual medium-pressure sand bed plugging instrument, and the sand particle size used was 80-100 mesh, and the specific steps were as follows:

[0178] Put 350 mL of sand into the sand filter tube and fill it evenly; add 200 mL of the drilling fluid to be tested on top of the sand, cover the cover tightly, and seal the cover opening with a sealing ring; place a graduated cylinder of a certain size under the sand filter tube to measure the filtration loss. First, open the total gas valve of the nitrogen cylinder to provide a gas source. When the value of the pressure gauge connected to the upper end of the pressure cover increases to 100 psi and stabilizes, open the valve between the pressure gauge and the pressure cover to ventilate. After 30 minutes, record the filtration loss in the graduated cylinder (the filtration loss is the depth of sand bed penetration or the filtration volume). The results are shown in Table 2.

[0179] The core plugging rate was tested according to the following method:

[0180] On the core flow tester, the initial positive standard saline permeability K1 of the rock sample was determined by using the drilling fluid pollution holder. Then the core pollution holder was removed and connected to the drilling fluid high temperature and high pressure dynamic comprehensive tester. The rock sample was plugged in the positive direction by using the drilling fluid, the drilling fluid temperature was 80℃, the pressure difference was 3.5 MPa, the confining pressure was 5 MPa, and the shear rate was 150 s -1 After 30 min of damage, the core pollution holder was removed and connected to the core flow tester, and the positive standard saline permeability K2 of the core was determined. The core plugging rate was:

[0181]

[0182] The test results are shown in Table 2.

[0183] Table 2 Drilling fluid plugging performance test

[0184]

[0185]

[0186] As can be seen from Table 2, the anti-220℃ saturated salt environment-friendly water-based drilling fluid of the present application has good plugging performance, and the sand bed invasion depth is as low as 0.5 cm, and the core plugging rate reaches 98.6%.

[0187] Test Example 3

[0188] The drilling fluids F1-F7 were subjected to environmental performance evaluation according to SY / T 6788-2020 “Environmental Protection Technology Evaluation Requirements for Water-soluble Oilfield Chemicals”, and the biotoxicity EC50 of the luminous bacteria method was tested. The test results are shown in Table 3.

[0189] Table 3 Biotoxicity EC50 of luminous bacteria method

[0190] Drilling fluid EC50 / mg / L Fl 69000 F2 64000 F3 75000 F4 71000 F5 70000 F6 69000 F7 68000

[0191] As can be seen from Table 3, the anti-220℃ saturated salt environment-friendly water-based drilling fluid of the present application has good biocompatibility and meets the environmental protection requirements.

[0192] In summary, the anti-220 DEG C saturated salt environment-friendly water-based drilling fluid can exhibit good performance under high temperature and high salt conditions, and meet the needs of deep oil and gas formation drilling.

[0193] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0194] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0195] In addition, various different embodiments of the present application can also be combined in any manner, as long as they do not deviate from the idea of the present application, and they should also be considered as disclosed by the present application.

Claims

1. An environmentally friendly water-based drilling fluid resistant to 220 °C saturated salt, characterized in that, The raw material composition comprises the following components by weight: water 100 parts, composite soil cutting agent 1-4 parts, sodium hydroxide 0.2-0.6 parts, high-temperature-resistant and salt-resistant amphoteric ionic polymer 3-6 parts, high-temperature-resistant and salt-resistant anionic polymer 2-4 parts, alcohol amine inhibitor 3-5 parts, organic-inorganic hybrid microsphere plugging agent 6-10 parts, strong adsorption anti-collapse plugging agent 2-4 parts, composite oil and fat lubricant 3-4 parts, and system stabilizer 0.5-1 part; The composite soil cutting agent is obtained by mixing bentonite, attapulgite, diatomite, volcanic stone powder and sepiolite; The high-temperature-resistant and salt-resistant amphoteric ionic polymer is prepared from the following raw materials by weight: N,N-dimethylacrylamide 15-25 parts, 2-acrylamido-2-methylpropanesulfonic acid 5-15 parts, water 120-140 parts, methacryloyloxyethyltrimethylammonium chloride 10-20 parts, TPEG-2400 (methyl allyl polyoxyethylene ether-2400) 10-20 parts, 1-vinylimidazole 5-10 parts, N,N,N',N'-tetramethyl ethylenediamine 0.1-1 part, ammonium persulfate 0.1-0.5 part, and sodium bisulfite 0.01-0.1 part; The preparation method of the high-temperature-resistant and salt-resistant anionic polymer comprises the following steps: (1) Dissolve sodium formaldehyde sulfoxylate in deionized water, add a 30-50 wt% dimethylamine aqueous solution, stir and react, centrifuge and take the precipitate, and dry to obtain sodium (N,N-dimethylamino) methylene sulfonate; (2) Dissolve sodium (N,N-dimethylamino) methylene sulfonate in an ethanol aqueous solution to obtain a sodium (N,N-dimethylamino) methylene sulfonate solution; dissolve 4-chloromethylstyrene in anhydrous ethanol to obtain a 4-chloromethylstyrene solution; drop the sodium (N,N-dimethylamino) methylene sulfonate solution into the 4-chloromethylstyrene solution, stir and react, filter, wash, dry, and crush to obtain betaine monomer; (3) Disperse N,N-dimethylacrylamide, betaine monomer, and 2-acrylamido-2-methylpropanesulfonic acid in deionized water, add an initiator potassium persulfate, and perform free radical polymerization, then wash, dry, and crush to obtain the high-temperature-resistant and salt-resistant anionic polymer; The organic-inorganic hybrid microsphere plugging agent is prepared from the following raw materials by weight: Sodium p-styrenesulfonate 5-15 parts, 2-acrylamido-2-methylpropanesulfonic acid 1-10 parts, water 100 parts, sodium dodecylbenzenesulfonate 0.1-0.5 parts, KH-570 modified nano silicon dioxide 1-3 parts, styrene 15-25 parts, initiator potassium persulfate 0.1-0.3 parts, and crosslinking agent N,N'-methylene bisacrylamide 0.01-0.05 parts; The strong adsorption anti-collapse plugging agent is prepared from the following raw materials by weight: methacrylic acid 5-15 parts, water 100-140 parts, N-vinylpyrrolidone 1-10 parts, methyl methacrylate 10-30 parts, lauryl methacrylate 1-10 parts, divinylbenzene 1-5 parts, and initiator potassium persulfate 0.05-0.5 parts.

2. The environmentally friendly water-based drilling fluid of claim 1, wherein, One or more of the following conditions are included: i. The mass ratio of bentonite, attapulgite, diatomite, volcanic stone powder and sepiolite is 1-3:1:0.1-1:0.1-1:0.1-1; ii. The alcohol amine inhibitor is obtained by mixing polyether amine D230, polyether amine D400, polyethylene glycol 400, triethanolamine and pentaethylene hexamine; the mass ratio of polyether amine D230, polyether amine D400, polyethylene glycol 400, triethanolamine and pentaethylene hexamine is 1-3:1:1:0.1-0.5:0.1-0.3; iii. The composite grease lubricant is obtained by mixing glycerol oleate material, castor oil and SP-60; the mass ratio of glycerol oleate material, castor oil and SP-60 is 1:1:0.1-1; the glycerol oleate material is selected from one or a combination of two or more of glycerol monooleate, glycerol dioleate or glycerol trioleate; iv. The system stabilizer is obtained by mixing Span-80, Tween-80 and OP-10; the mass ratio of Span-80, Tween-80 and OP-10 is 1-3:1:

1.

3. The environmentally friendly water-based drilling fluid according to claim 1, wherein the saturated salt at 220°C is sodium chloride. The preparation method of the anti-high-temperature and anti-salt zwitterionic polymer comprises the following steps: N,N-dimethyl acrylamide and 2-acrylamido-2-methylpropanesulfonic acid are fully dispersed in water, 40-60wt% NaOH aqueous solution is used to adjust the pH to 7-8; methyl acryloyloxyethyl trimethyl ammonium chloride, TPEG-2400, 1-vinylimidazole and N,N,N',N'-tetramethyl ethylenediamine are added and fully dispersed; ammonium persulfate and sodium bisulfite mixed initiator is added, and then stirring reaction, washing, drying and crushing are carried out to obtain the anti-high-temperature and anti-salt zwitterionic polymer.

4. The environmentally friendly water-based drilling fluid of claim 1, wherein the saturated salt at 220°C is selected from the group consisting of NaCI, KCI, and combinations thereof. In the preparation method of the anti-high-temperature and anti-salt anionic polymer, one or more of the following conditions is included: i. In step (1), the mass ratio of formaldehyde sodium bisulfite, deionized water and dimethylamine aqueous solution is 1:3-5:1-3; ii. In step (1), the stirring reaction temperature is 25-35℃, and the stirring reaction time is 70-75h; iii. In step (2), the mass ratio of ethanol to water in the ethanol aqueous solution is 1:1; iv. In step (2), the mass ratio of (N,N-dimethylamino)methylene sulfonic acid sodium, ethanol aqueous solution, 4-chloromethylstyrene and anhydrous ethanol is 6-8:90-110:3-8:30-50; v. In step (2), the dropping time is 5-10min; the stirring reaction temperature is 40-50℃, and the stirring reaction time is 20-30h; vi. In step (3), the mass ratio of N,N-dimethyl acrylamide, betaine monomer, 2-acrylamido-2-methylpropanesulfonic acid, deionized water and potassium persulfate is 18-25:6-10:6-10:90-110:0.1-0.3; vii. In step (3), the free radical polymerization reaction temperature is 50-70℃, and the free radical polymerization reaction time is 4-8 hours.

5. The environmentally friendly water-based drilling fluid according to claim 1, wherein the saturated salt at 220°C is sodium chloride. The preparation method of the organic-inorganic hybrid microsphere plugging agent comprises the following steps: 1) sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, sodium dodecylbenzenesulfonate, KH-570 modified nano-silica are fully dispersed in water to obtain solution a; 2) under stirring, styrene is added dropwise into solution a, and the mixture is stirred at room temperature for 20-40 minutes to form an emulsion; under stirring, initiator potassium persulfate and crosslinking agent N,N'-methylenebisacrylamide are added, and the mixture is stirred to obtain the organic-inorganic hybrid microsphere plugging agent.

6. The environmentally friendly water-based drilling fluid of claim 1, wherein the saturated salt at 220°C is selected from the group consisting of NaCI, KCI, and combinations thereof. The preparation method of the strong adsorption anti-collapse plugging agent comprises the following steps: 1) methyl methacrylate, N-vinylpyrrolidone are fully dispersed in water to obtain mixed solution 1; 2) methyl methacrylate, lauryl methacrylate and divinylbenzene are fully mixed, and the polymerization inhibitor MEHQ is washed away using 40-60% NaOH aqueous solution to obtain mixed solution 2; 3) under stirring, mixed solution 2 is added dropwise into mixed solution 1, and initiator potassium persulfate is added, and the mixture is stirred to obtain the strong adsorption anti-collapse plugging agent.

7. The preparation method of the 220℃ saturated salt-resistant environment-friendly water-based drilling fluid according to any one of claims 1-6, comprising the following steps: The composite soil cutting agent and sodium hydroxide are fully dispersed in water, and then the high-temperature and salt-resistant zwitterionic polymer, the high-temperature and salt-resistant anionic polymer, the alcohol amine inhibitor, the organic-inorganic hybrid microsphere plugging agent, the strong adsorption anti-collapse plugging agent, the composite grease lubricant and the system stabilizer are sequentially added and fully dispersed to obtain the 220℃ saturated salt-resistant environment-friendly water-based drilling fluid.

8. The method for preparing the 220 °C saturated salt environment-friendly water-based drilling fluid according to claim 7, characterized in that, The preparation method of the 220℃ saturated salt-resistant environment-friendly water-based drilling fluid comprises the following steps: Water is added to a high-speed stirring cup, and the composite soil cutting agent and sodium hydroxide are added under low-speed stirring for 24-48 hours; the high-temperature and salt-resistant zwitterionic polymer is added and stirred at high speed for 20 minutes; the high-temperature and salt-resistant anionic polymer is added and stirred at high speed for 20 minutes; the alcohol amine inhibitor is added and stirred at high speed for 20 minutes; the organic-inorganic hybrid microsphere plugging agent is added and stirred at high speed for 20 minutes; The strong adsorption anti-collapse plugging agent is added and stirred at high speed for 20 minutes; the composite grease lubricant is added and stirred at high speed for 20 minutes; the system stabilizer is added and stirred at high speed for 20 minutes to obtain the 220℃ saturated salt-resistant environment-friendly water-based drilling fluid; the low-speed stirring speed is 1000-3000 r / min, and the high-speed stirring speed is 8000-10000 r / min.

9. The application of the 220℃ saturated salt-resistant environment-friendly water-based drilling fluid according to any one of claims 1-6, which is applied in the drilling process of deep or ultra-deep layers.

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