Deep well polysulfonate drilling fluid and preparation method thereof

Abstract

The invention discloses a deep well polysulfonate drilling fluid and a preparation method thereof, and relates to the technical field of drilling fluids. The deep well polysulfonate drilling fluid comprises the following raw materials in parts by weight: 100 parts of deionized water, 3-5 parts of bentonite, 5-8 parts of a modified filtrate reducer, 3-5 parts of a modified emulsifier, 0.5-2 parts of a pH regulator, 2-3 parts of a lubricant, 2-6 parts of a plugging agent and 250-300 parts of barite powder. The preparation method comprises the following steps: reacting 2, 2-dimethylolpropionic acid with 2-methyl-2-acrylic acid-2, 3-dihydroxy propyl ester to generate a hyperbranched product; then, the acidolysis starch is grafted with chlorophenyl triethoxy silane, and silane modified acidolysis starch is obtained; reacting the silane modified acidolysis starch with the hyperbranched product to generate a silanized hyperbranched product; and reacting acrylamide, sodium p-styrenesulfonate, allyloxy polyoxyethylene ether and the silanized hyperbranched product to generate the modified filtrate reducer. The drilling fluid prepared by the invention has good filtrate loss reduction performance.

Description

Technical Field

[0001] The invention relates to the technical field of drilling fluids, and in particular to a deep well polysulfone drilling fluid and a preparation method thereof. Background Art

[0002] The Tarim Basin is an important oil and gas resource-rich area in my country. Its deep strata have ultra-deep, ultra-high temperature, ultra-high pressure, complex lithology, diverse fluids and complex stress. In the process of deep well drilling, drilling fluid technology faces many challenges. First, a large number of micro-fractured and broken dolomites are developed in the Cambrian strata, and the drilling fluid needs to have good plugging performance to prevent wellbore collapse. Secondly, thin layers of gypsum are easily dissolved under the action of drilling fluid, resulting in wellbore instability, which puts higher requirements on the inhibition and stability of drilling fluid. In addition, the high temperature environment (over 200°C) of deep wells in the Tarim Basin puts the high temperature stability, rheological properties and filtration control capabilities of drilling fluids under severe test. At the same time, drilling fluids are easily contaminated in high-salt formations, resulting in performance degradation and affecting drilling efficiency. These complex geological conditions put forward extremely high requirements on the formulation design and performance optimization of deep well polysulfonate drilling fluids. In order to solve the above problems, it is particularly important to develop a high-performance deep well polysulfonate drilling fluid system.

[0003] A Chinese invention patent with publication number CN102766446A discloses a high-temperature resistant high-density formate polysulfone drilling fluid and a preparation method thereof. The high-temperature resistant high-density formate polysulfone drilling fluid comprises the following components in parts by weight: 100 parts of water, 2-5 parts of bentonite, 0.1-10 parts of high-temperature resistant sulfonate polymer, 20-100 parts of formate, 0.6-2.0 parts of potassium hydroxide, 8-20 parts of sulfonated treatment agent, 2-6 parts of plugging agent, 0.5-3.0 parts of emulsifier, 0.2-3.0 parts of pH adjuster, and 120-270 parts of barite powder; the drilling fluid prepared by the patent has poor filtration loss reduction performance. Summary of the invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a deep well polysulfone drilling fluid and a preparation method thereof.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions: A deep well polysulfone drilling fluid comprises the following raw materials in parts by weight: Deionized water: 100 parts, bentonite: 3-5 parts, modified fluid loss agent: 5-8 parts, modified emulsifier: 3-5 parts, pH regulator: 0.5-2 parts, lubricant: 2-3 parts, plugging agent: 2-6 parts, barite powder: 250-300 parts; The modified fluid loss reducer is prepared by the following method: S1: Under nitrogen protection, 2,2-dihydroxymethylpropionic acid and 2-methyl-2-acrylate-2,3-dihydroxypropyl ester are catalyzed by p-toluenesulfonic acid to generate hyperbranched products; S2: corn starch is acidified under the action of dilute hydrochloric acid to obtain acid-hydrolyzed starch, and the acid-hydrolyzed starch is reacted with chlorophenyltriethoxysilane to obtain silane-modified acid-hydrolyzed starch; S3: Silane-modified acid-hydrolyzed starch and hyperbranched product react with sodium hydroxide to generate silanized hyperbranched product; S4: Acrylamide, sodium p-styrene sulfonate, allyloxy polyoxyethylene ether, and silylated hyperbranched products react under the action of ammonium persulfate to generate a modified fluid loss reducer.

[0006] In step S1, the feed mass ratio of 2,2-dihydroxymethylpropionic acid to 2-methyl-2-acrylate-2,3-dihydroxypropyl ester is 5:(25-30).

[0007] In step S2, the mass ratio of the acid-hydrolyzed starch to chlorophenyltriethoxysilane is (12-16):10.

[0008] In step S3, the feed mass ratio of the silane-modified acid-hydrolyzed starch to the hyperbranched product is 20:(3-5).

[0009] In step S4, the feed mass ratio of acrylamide, sodium p-styrene sulfonate, allyloxy polyoxyethylene ether, and silylated hyperbranched product is (30-40):(20-25):(2-5):2.

[0010] The modified emulsifier is prepared by the following method: A1: 3-aminopropyltriethoxysilane is hydrolyzed to generate 3-aminopropylsilanetriol, which is then modified with nano-silica to obtain modified nano-silica; A2: Modified nano-silica reacts with stearic acid and caprylic acid to obtain a modified emulsifier.

[0011] In step A1, the mass ratio of the 3-aminopropyltriethoxysilane to the nano-silicon dioxide is (0.5-2):10.

[0012] In step A2, the mass ratio of the modified nano-silicon dioxide, stearic acid and octanoic acid is 20:(6-10):(3-5).

[0013] The pH regulator is a combination of one or more of potassium carbonate, potassium hydroxide, and sodium hydroxide; the lubricant is white mineral oil; and the plugging agent is sulfonated asphalt.

[0014] A method for preparing a deep well polysulfone drilling fluid comprises the following steps: (1) Weigh by weight: deionized water: 100 parts, bentonite: 3-5 parts, modified fluid loss reducer: 5-8 parts, modified emulsifier: 3-5 parts, pH adjuster: 0.5-2 parts, lubricant: 2-3 parts, plugging agent: 2-6 parts, barite powder: 250-300 parts; (2) Add deionized water to the container, add bentonite while stirring, stop stirring after stirring for 15-25 minutes, and seal and cure for 24 hours to obtain prehydrated bentonite slurry; add pH adjuster, modified filtrate reducer, modified emulsifier, plugging agent, and lubricant to the prehydrated bentonite slurry in the above proportions, stir at high speed for 50-70 minutes, and finally add barite powder and stir evenly to obtain deep well polysulfone drilling fluid.

[0015] Due to the adoption of the above technical solution, the beneficial effects of the present invention include: (1) The present invention generates a hyperbranched product by reacting 2,2-dihydroxymethylpropionic acid with 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester; acidifying corn starch to obtain acid-hydrolyzed starch, reacting the hydroxyl groups in the acid-hydrolyzed starch with the siloxy groups in chlorophenyltriethoxysilane to obtain silane-modified acid-hydrolyzed starch; the chlorine atoms in the silane-modified acid-hydrolyzed starch and the hydroxyl groups in the hyperbranched product undergo a substitution reaction to generate a silylated hyperbranched product; and acrylamide, sodium p-styrene sulfonate, allyloxy polyoxyethylene ether, and the silylated hyperbranched product undergo a free radical polymerization reaction under the action of ammonium persulfate to generate a modified fluid loss reducer.

[0016] (2) 3-aminopropyltriethoxysilane is hydrolyzed to generate 3-aminopropylsilanetriol, which is then modified with nano-silica to obtain modified nano-silica; the modified nano-silica is reacted with stearic acid and caprylic acid to obtain a modified emulsifier.

[0017] (3) The modified fluid loss reducer prepared by the present invention exhibits excellent fluid loss reduction performance in drilling fluid due to its unique three-dimensional network structure: hyperbranched molecules and starch synergistically construct a dense filter cake, hydroxyl groups strengthen the bridging and plugging of clay particles through hydrogen bonds, and siloxane segments precisely regulate the pore structure of the filter cake through hydrophobic association to achieve nanoscale pore throat plugging; the internal cavity of the molecule and the hydroxyl-siloxane synergistic effect form a thermally stable complex, which enables the filter cake to maintain low permeability at high temperatures. At the same time, the hyperbranched structure gives the system salt pollution resistance through volume exclusion effect and dynamic cross-linking network, significantly reducing the fluid loss of drilling fluid.

[0018] (4) The surface of nano-silica modified by silane coupling agent forms an organic-inorganic hybrid structure, which is adsorbed on the oil-water interface through hydrogen bonding and hydrophobic interaction, effectively reducing the interfacial tension and inhibiting the aggregation of droplets. The long alkyl chain of stearic acid and the short chain of octanoic acid work synergistically to form a dense interfacial film, which improves the stability of the emulsion in high temperature and high salt environments. DETAILED DESCRIPTION

[0019] The invention will be further described below in conjunction with the embodiments, but the invention is not limited to these embodiments.

[0020] Example 1 Preparation of modified fluid loss additive: S1: Under nitrogen protection, 1000g toluene, 50g 2,2-dihydroxymethylpropionic acid, and 250g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor, stirred and mixed, heated to reflux, and then 8g p-toluenesulfonic acid was added. After reacting for 6h (a water separator was used to remove the generated water during the reaction), the temperature was cooled to room temperature, and 10wt% sodium bicarbonate solution was slowly added to adjust the pH to neutral (neutral in this application refers to pH=7), stirred thoroughly for 30min, allowed to stand and stratify, the organic phase was transferred to a rotary evaporator, and distilled under reduced pressure at 55°C for 3h, and vacuum dried at 70°C for 2h to obtain a hyperbranched polymer; the reaction equation is shown as follows:

[0021] It should be noted that the reaction process of the hyperbranching reaction is relatively complicated, and the above structure is only used to understand the situation of the reaction site in this application.

[0022] S2: Add 80g corn starch and 200ml 0.25mol / L dilute hydrochloric acid, stir and mix, heat to 50℃, react for 4h, cool to room temperature, slowly add 5wt% NaOH solution, adjust pH to 7.0, slowly add 200ml anhydrous ethanol at 0℃, stir for 20min, filter, and vacuum dry at 70℃ for 2h to obtain acid-decomposed starch; under nitrogen protection, add 1000g toluene and 120g acid-decomposed starch to the reactor, stir and heat to 60℃, keep warm for 1h, then add 100g chlorophenyltriethoxysilane and 6g catalyst p-toluenesulfonic acid, heat to 80℃, react for 6h, cool to room temperature, add 10wt% sodium bicarbonate solution to adjust pH to 7.0, stir for 30min, pour the reaction solution into 2000ml anhydrous ethanol, let stand for 1h, centrifuge, wash three times with 300ml ethanol-water (ethanol: water (v / v) = 7:3), and vacuum dry at 50℃ for 4h to obtain silane-modified acid-decomposed starch; S3: Under nitrogen protection, add 1000g toluene, 200g silane-modified acid-hydrolyzed starch, and 30g hyperbranched product to the reactor, stir and mix, heat to 80°C, react for 4h, cool to 60°C, slowly drop 40g 42wt% sodium hydroxide solution, drop for 10min, continue to react at 80°C for 2h, cool to room temperature, slowly add 1M dilute hydrochloric acid solution to adjust pH to neutral; stand for stratification, separate the water phase, retain the organic phase, distill under reduced pressure at 70°C for 2h, then add 200ml saturated sodium chloride solution for washing, repeat three times, and vacuum dry at 70°C for 3h to obtain the silanized hyperbranched product; S4: Under nitrogen protection, add 2000g of deionized water, 300g of acrylamide, 200g of sodium p-styrene sulfonate, 20g of allyloxypolyoxyethylene ether, and 20g of silylated hyperbranched product into the reactor, stir to mix, heat to 80°C, then add 10g of ammonium persulfate, react for 4h, add 5000ml of anhydrous ethanol, stir for 20min, let stand for 1h, filter, and vacuum dry at 70°C for 3h to obtain a modified filtration reducer.

[0023] Example 2 Preparation of modified fluid loss additive: S1: Under nitrogen protection, 1000 g toluene, 50 g 2,2-dihydroxymethylpropionic acid, and 280 g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor, stirred and mixed, heated to reflux, and then 10 g p-toluenesulfonic acid was added. After reacting for 6 h (a water separator was used to remove the generated water during the reaction), the temperature was cooled to room temperature, and 10 wt % sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred for 30 min, and the mixture was allowed to stand for stratification. The organic phase was transferred to a rotary evaporator, and distilled under reduced pressure at 60 ° C for 2 h, and dried under vacuum at 60 ° C for 3 h to obtain a hyperbranched polymer; S2: Add 80g corn starch and 200ml 0.25mol / L dilute hydrochloric acid, stir and mix, heat to 50℃, react for 4h, cool to room temperature, slowly add 5wt% NaOH solution, adjust pH to 7.0, slowly add 200ml anhydrous ethanol at 0℃, stir for 20min, filter, and vacuum dry at 70℃ for 2h to obtain acid-degraded starch; under nitrogen protection, add 1000g toluene and 140g acid-degraded starch to the reactor, stir and heat to 60℃, keep warm for 1h, then add 100g chlorophenyltriethoxysilane and 6g catalyst p-toluenesulfonic acid, heat to 85℃, react for 5h, cool to room temperature, add 10wt% sodium bicarbonate solution to adjust pH to 7.0, stir for 30min, pour the reaction solution into 2000ml anhydrous ethanol, let stand for 1h, centrifuge, wash three times with 300ml ethanol-water (ethanol: water (v / v) = 7:3), and vacuum dry at 60℃ for 3h to obtain silane-modified acid-degraded starch; S3: Under nitrogen protection, add 1000g toluene, 200g silane-modified acid-hydrolyzed starch, and 40g hyperbranched product to the reactor, stir and mix, heat to 85°C, react for 3h, cool to 60°C, slowly drop 45g 42wt% sodium hydroxide solution, drop for 10min, continue to react at 85°C for 1.5h, cool to room temperature, slowly add 1M dilute hydrochloric acid solution to adjust pH to neutral; stand for stratification, separate the water phase, retain the organic phase, distill under reduced pressure at 60°C for 2.5h, then add 200ml saturated sodium chloride solution for washing, repeat three times, and vacuum dry at 80°C for 2h to obtain the silanized hyperbranched product; S4: Under nitrogen protection, add 2000g of deionized water, 350g of acrylamide, 220g of sodium p-styrene sulfonate, 30g of allyloxypolyoxyethylene ether, and 20g of silylated hyperbranched product into the reactor, stir to mix, heat to 85°C, then add 10g of ammonium persulfate, react for 3h, add 5000ml of anhydrous ethanol, stir for 20min, let stand for 1h, filter, and vacuum dry at 60°C for 4h to obtain a modified filtration reducer.

[0024] Example 3 Preparation of modified fluid loss additive: S1: Under nitrogen protection, 1000 g toluene, 50 g 2,2-dihydroxymethylpropionic acid, and 300 g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor, stirred and mixed, heated to reflux, and then 12 g p-toluenesulfonic acid was added. After reacting for 6 h (a water separator was used to remove the generated water during the reaction), the mixture was cooled to room temperature, and 10 wt % sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred for 30 min, allowed to stand and stratified, and the organic phase was transferred to a rotary evaporator, distilled under reduced pressure at 60 ° C for 2 h, and dried under vacuum at 50 ° C for 4 h to obtain a hyperbranched polymer; S2: Add 80g corn starch and 200ml 0.2mol / L dilute hydrochloric acid, stir and mix, heat to 50℃, react for 4h, cool to room temperature, slowly add 5wt% NaOH solution, adjust pH to 7.0, slowly add 200ml anhydrous ethanol at 0℃, stir for 20min, filter, and vacuum dry at 70℃ for 2h to obtain acidified starch; under nitrogen protection, add 1000g toluene and 160g acid-degraded starch to the reactor, stir and heat to 60℃, keep warm for 1h, then add 100g chlorophenyltriethoxysilane and 8g catalyst p-toluenesulfonic acid, heat to 85℃, react for 5h, cool to room temperature, add 10wt% sodium bicarbonate solution to adjust pH to 7.0, stir for 30min, pour the reaction solution into 2000ml anhydrous ethanol, let stand for 1h, centrifuge, wash three times with 300ml ethanol-water (ethanol: water (v / v) = 7:3), and vacuum dry at 70℃ for 2h to obtain silane-modified acid-degraded starch; S3: Under nitrogen protection, add 1000g toluene, 200g silane-modified acid-hydrolyzed starch, and 50g hyperbranched product to the reactor, stir and mix, heat to 90°C, react for 2h, cool to 60°C, slowly add 50g 42wt% sodium hydroxide solution dropwise for 10min, continue to react at 90°C for 1h, cool to room temperature, slowly add 1M dilute hydrochloric acid solution to adjust the pH to neutral; stand for stratification, separate the water phase, retain the organic phase, distill under reduced pressure at 60°C for 3h, then add 200ml saturated sodium chloride solution for washing, repeat three times, and vacuum dry at 90°C for 1h to obtain the silanized hyperbranched product; S4: Under nitrogen protection, add 2000g of deionized water, 400g of acrylamide, 250g of sodium p-styrene sulfonate, 50g of allyloxypolyoxyethylene ether, and 20g of silylated hyperbranched product into the reactor, stir to mix, heat to 90°C, then add 10g of ammonium persulfate, react for 2h, add 5000ml of anhydrous ethanol, stir for 20min, let stand for 1h, filter, and vacuum dry at 50°C for 5h to obtain a modified filtration reducer.

[0025] Example 4 Preparation of modified emulsifier: A1: Weigh 5g of 3-aminopropyltriethoxysilane, add 500ml of deionized water, and stir at 40℃ for 3h to obtain 3-aminopropylsilane triol; add 100g of nano-silica into 1000ml of ethanol-water mixed solvent (ethanol: water (V:V) = 1:1), and ultrasonically disperse for 15min to obtain nano-silica dispersion; slowly drop 3-aminopropylsilane triol into the nano-silica dispersion, add for 20min, stir and mix, heat to 80℃, react for 10h, cool to room temperature, filter, wash with deionized water 3 times (using 200ml of deionized water each time), vacuum dry at 80℃ for 4h, and pass through 80-mesh sieve to obtain modified nano-silica; A2: Add 1000 ml of toluene, 200 g of modified nano-silica, 30 g of octanoic acid, and 60 g of stearic acid into the reactor, stir and mix well, heat to reflux for 8 hours, cool to room temperature, centrifuge, wash with 300 ml of anhydrous ethanol and 100 ml of acetone in turn, and dry under vacuum at 50°C for 5 hours to obtain a modified emulsifier.

[0026] Example 5 Preparation of modified emulsifier: A1: Weigh 10g of 3-aminopropyltriethoxysilane, add 500ml of deionized water, and stir at 40℃ for 3h to obtain 3-aminopropylsilane triol; add 100g of nano-silica into 1000ml of ethanol-water mixed solvent (ethanol: water (V:V) = 1:1), and ultrasonically disperse for 15min to obtain nano-silica dispersion; slowly drop 3-aminopropylsilane triol into the nano-silica dispersion, add for 20min, stir and mix, heat to 90℃, react for 8h, cool to room temperature, filter, wash with deionized water 3 times (using 200ml of deionized water each time), vacuum dry at 70℃ for 5h, and pass through 80-mesh sieve to obtain modified nano-silica; A2: Add 1000 ml of toluene, 200 g of modified nano-silica, 40 g of octanoic acid, and 80 g of stearic acid into the reactor, stir and mix well, heat to reflux for 6 hours, cool to room temperature, centrifuge, wash with 300 ml of anhydrous ethanol and 100 ml of acetone in turn, and dry under vacuum at 60°C for 4 hours to obtain a modified emulsifier.

[0027] Example 6 Preparation of modified emulsifier: A1: Weigh 20g of 3-aminopropyltriethoxysilane, add 500ml of deionized water, and stir at 40℃ for 3h to obtain 3-aminopropylsilane triol; add 100g of nano-silica into 1000ml of ethanol-water mixed solvent (ethanol: water (V:V) = 1:1), and ultrasonically disperse for 15min to obtain nano-silica dispersion; slowly drop 3-aminopropylsilane triol into the nano-silica dispersion, add for 20min, stir and mix, heat to 100℃, react for 6h, cool to room temperature, filter, wash with deionized water 3 times (using 200ml of deionized water each time), vacuum dry at 60℃ for 6h, and pass through 80-mesh sieve to obtain modified nano-silica; A2: Add 1000 ml of toluene, 200 g of modified nano-silica, 50 g of octanoic acid, and 100 g of stearic acid into the reactor, stir and mix well, heat to reflux for 4 hours, cool to room temperature, centrifuge, wash with 300 ml of anhydrous ethanol and 100 ml of acetone in turn, and dry under vacuum at 70°C for 3 hours to obtain a modified emulsifier.

[0028] Example 7 Preparation of deep well polysulfone drilling fluid: (1) Weigh: deionized water: 1000 g, bentonite: 30 g, modified fluid loss reducer (prepared in Example 1): 50 g, modified emulsifier (prepared in Example 4): 30 g, pH adjuster (potassium carbonate): 5 g, lubricant (white mineral oil): 20 g, plugging agent (sulfonated asphalt): 20 g, barite powder: 2500 g; (2) At room temperature, deionized water was added to the container, and bentonite was added while stirring. After stirring for 15 minutes, stirring was stopped, and the container was sealed and cured for 24 hours to obtain a prehydrated bentonite slurry. A pH adjuster, a modified fluid loss reducer, a modified emulsifier, a plugging agent, and a lubricant were added to the prehydrated bentonite slurry in the above proportions. The slurry was stirred at a high speed of 8000 r / min for 50 minutes. Finally, barite powder was added and stirred evenly to obtain a deep well polysulfone drilling fluid.

[0029] Example 8 Preparation of deep well polysulfone drilling fluid: (1) Weigh: deionized water: 1000 g, bentonite: 40 g, modified fluid loss reducer (prepared in Example 2): 60 g, modified emulsifier (prepared in Example 5): 40 g, pH adjuster (potassium hydroxide): 10 g, lubricant (white mineral oil): 25 g, plugging agent (sulfonated asphalt): 40 g, barite powder: 2800 g; (2) At room temperature, deionized water was added to the container, and bentonite was added while stirring. After stirring for 20 minutes, stirring was stopped, and the container was sealed and cured for 24 hours to obtain a prehydrated bentonite slurry. A pH adjuster, a modified fluid loss reducer, a modified emulsifier, a plugging agent, and a lubricant were added to the prehydrated bentonite slurry in the above proportions. The slurry was stirred at a high speed for 60 minutes at a speed of 8000 r / min. Finally, barite powder was added and stirred evenly to obtain a deep well polysulfone drilling fluid.

[0030] Example 9 Preparation of deep well polysulfone drilling fluid: (1) Weigh: deionized water: 1000 g, bentonite: 50 g, modified fluid loss reducer (prepared in Example 3): 80 g, modified emulsifier (prepared in Example 6): 50 g, pH adjuster (sodium hydroxide): 20 g, lubricant (white mineral oil): 30 g, plugging agent (sulfonated asphalt): 60 g, barite powder: 3000 g; (2) At room temperature, deionized water was added to the container, and bentonite was added while stirring. After stirring for 25 minutes, stirring was stopped, and the container was sealed and cured for 24 hours to obtain a prehydrated bentonite slurry. A pH adjuster, a modified fluid loss reducer, a modified emulsifier, a plugging agent, and a lubricant were added to the prehydrated bentonite slurry in the above proportions. The slurry was stirred at a high speed for 70 minutes at a speed of 8000 r / min. Finally, barite powder was added and stirred evenly to obtain a deep well polysulfone drilling fluid.

[0031] Comparative Example 1 A method for preparing a deep well polysulfone drilling fluid is substantially the same as that of Example 8, except that the modified fluid loss agent is replaced with an equal weight of a commercially available natural polymer fluid loss agent HFLD-1.

[0032] Comparative Example 2 A method for preparing a deep well polysulfone drilling fluid is substantially the same as that of Example 8, except that the modified fluid loss agent is replaced by an equal weight of a modified fluid loss agent prepared by the following method: The preparation method of the modified fluid loss reducer in this comparative example is substantially the same as that in Example 2, except that the 2,2-dihydroxymethylpropionic acid added in step S1 is replaced by 50 g of propionic acid.

[0033] Comparative Example 3 A method for preparing a deep well polysulfone drilling fluid is substantially the same as that of Example 8, except that the modified fluid loss agent is replaced by an equal weight of a modified fluid loss agent prepared by the following method: S1: Under nitrogen protection, 1000 g toluene, 50 g 2,2-dihydroxymethylpropionic acid, and 280 g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor, stirred and mixed, heated to reflux, and then 10 g p-toluenesulfonic acid was added. After reacting for 6 h (a water separator was used to remove the generated water during the reaction), the temperature was cooled to room temperature, and 10 wt % sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred for 30 min, and the mixture was allowed to stand for stratification. The organic phase was transferred to a rotary evaporator, and distilled under reduced pressure at 60 ° C for 2 h, and dried under vacuum at 60 ° C for 3 h to obtain a hyperbranched polymer; S2: Under nitrogen protection, 1000 g toluene, 200 g chlorophenyltriethoxysilane and 40 g hyperbranched product were added to the reactor, stirred and mixed, heated to 85°C, reacted for 3 h, cooled to 60°C, and 45 g 42 wt% sodium hydroxide solution was slowly added dropwise for 10 min. After the addition was completed, the reaction was continued at 85°C for 1.5 h, cooled to room temperature, and 1 M dilute hydrochloric acid solution was slowly added to adjust the pH to neutral; the mixture was allowed to stand for stratification, the water phase was separated, the organic phase was retained, and the mixture was distilled under reduced pressure at 60°C for 2.5 h, and then 200 ml saturated sodium chloride solution was added for washing, which was repeated three times, and the mixture was dried under vacuum at 80°C for 2 h to obtain intermediate 1; S3: Under nitrogen protection, add 2000g of deionized water, 350g of acrylamide, 220g of sodium p-styrene sulfonate, 30g of allyloxypolyoxyethylene ether, and 20g of intermediate 1 into the reactor, stir to mix, heat to 85°C, then add 10g of ammonium persulfate, react for 3h, add 5000ml of anhydrous ethanol, stir for 20min, let stand for 1h, filter, and vacuum dry at 60°C for 4h to obtain a modified filtrate reducer.

[0034] Comparative Example 4 A method for preparing a deep well polysulfone drilling fluid is substantially the same as that of Example 8, except that the modified fluid loss agent is replaced by an equal weight of a modified fluid loss agent prepared by the following method: The preparation method of the modified fluid loss additive in this comparative example is substantially the same as that in Example 2, except that the acid-hydrolyzed starch added in step S2 is replaced by an equal weight of chitosan.

[0035] Comparative Example 5 A method for preparing a deep well polysulfone drilling fluid is substantially the same as that of Example 8, except that the modified fluid loss agent is replaced by a hyperbranched polymer fluid loss agent prepared in Example 1 of Publication No. CN113527575A.

[0036] Comparative Example 6 A method for preparing a deep well polysulfone drilling fluid is substantially the same as that of Example 8, except that the modified emulsifier is replaced with a modified emulsifier prepared by the following method: A1: Weigh 10g of 3-aminopropyltriethoxysilane, add 500ml of deionized water, and stir at 40℃ for 3h to obtain 3-aminopropylsilane triol; add 100g of nano-silica into 1000ml of ethanol-water mixed solvent (ethanol: water (V:V) = 1:1), and ultrasonically disperse for 15min to obtain nano-silica dispersion; slowly drop 3-aminopropylsilane triol into the nano-silica dispersion, add for 20min, stir and mix, heat to 90℃, react for 8h, cool to room temperature, filter, wash with deionized water 3 times (using 200ml of deionized water each time), vacuum dry at 70℃ for 5h, and pass through 80-mesh sieve to obtain modified nano-silica; A2: Add 1000 ml of toluene, 200 g of modified nano-silica, and 80 g of stearic acid into the reactor, stir and mix well, heat to reflux for 6 hours, cool to room temperature, centrifuge, wash with 300 ml of anhydrous ethanol and 100 ml of acetone in turn, and dry under vacuum at 60°C for 4 hours to obtain a modified emulsifier.

[0037] Comparative Example 7 A method for preparing a deep well polysulfone drilling fluid is substantially the same as that of Example 8, except that the modified emulsifier is replaced with a modified emulsifier prepared by the following method: A1: Weigh 10g of 3-aminopropyltriethoxysilane, add 500ml of deionized water, and stir at 40℃ for 3h to obtain 3-aminopropylsilane triol; add 100g of nano-silica into 1000ml of ethanol-water mixed solvent (ethanol: water (V:V) = 1:1), and ultrasonically disperse for 15min to obtain nano-silica dispersion; slowly drop 3-aminopropylsilane triol into the nano-silica dispersion, add for 20min, stir and mix, heat to 90℃, react for 8h, cool to room temperature, filter, wash with deionized water 3 times (using 200ml of deionized water each time), vacuum dry at 70℃ for 5h, and pass through 80-mesh sieve to obtain modified nano-silica; A2: Add 1000 ml of toluene, 200 g of modified nano-silica, and 40 g of octanoic acid into the reactor, stir and mix well, heat to reflux for 6 hours, cool to room temperature, centrifuge, wash with 300 ml of anhydrous ethanol and 100 ml of acetone in turn, and dry under vacuum at 60°C for 4 hours to obtain a modified emulsifier.

[0038] Comparative Example 8 A method for preparing a deep well polysulfone drilling fluid is substantially the same as that of Example 8, except that the modified emulsifier is replaced with a modified emulsifier prepared by the following method: Add 100 g of nano-silica into 1000 ml of ethanol-water mixed solvent (ethanol: water (V:V) = 1:1), and ultrasonically disperse for 15 minutes to obtain a nano-silica dispersion; add 1000 ml of toluene, 200 g of nano-silica dispersion, 40 g of octanoic acid, and 80 g of stearic acid into a reactor, stir and mix evenly, heat to reflux for 6 hours, cool to room temperature, centrifuge, wash with 300 ml of anhydrous ethanol and 100 ml of acetone in turn, and dry under vacuum at 60°C for 4 hours to obtain a modified emulsifier.

[0039] Comparative Example 9 A high-temperature resistant and high-density formate polysulfone drilling fluid is prepared using the raw materials and method of Example 2 in publication number CN102766446A.

[0040] The bentonite model used in the examples and comparative examples of the present application is Bentone 38; the barite powder used in the examples and comparative examples of the present application has a particle size of 400 mesh and is produced by Shijiazhuang Mayue Building Materials Co., Ltd.; the nano-silica used in the examples and comparative examples of the present application is hydroxyl-modified nano-silica, model As-200, produced by Shenyang Chemical Co., Ltd.; the sulfonated asphalt model used in the examples and comparative examples of the present application is BFT-1, purchased from Tianjin Binpu Technology Development Co., Ltd.; the natural polymer filtrate reducer HFLD-1 used in the comparative example was purchased from Zhengzhou Jingyuan Mud Material Co., Ltd.; chitosan is produced by Zhejiang Jinke Pharmaceutical Co., Ltd., with a purity of 99% and an average molecular weight of 25,000 Daltons; the ethanol used in this application refers to anhydrous ethanol unless otherwise specified.

[0041] The deep well polysulfone drilling fluids prepared in the examples and comparative examples were subjected to apparent viscosity, plastic viscosity, dynamic shear force, and high temperature and high pressure fluid loss test tests. The test results are shown in Table 1.

[0042] The experiment was carried out in accordance with GB / T 16783.1-2014 “Field testing of drilling fluids in the petroleum and natural gas industry Part 1: Water-based drilling fluids”.

[0043] Table 1

[0044] It can be seen from Table 1 that the apparent viscosity of the deep well polysulfone drilling fluid prepared in the present application is about 35 mPa·s, the plastic viscosity is about 28 mPa·s, and the fluid loss reducer still has excellent fluid loss reduction performance after high-temperature aging at 220°C for 16 hours, indicating that the prepared polysulfone drilling fluid has excellent high temperature resistance.

[0045] Comparative Example 1 is different from Example 8 in that the modified fluid loss agent is replaced with an equal weight of a commercially available natural polymer fluid loss agent HFLD-1. As can be seen from Table 1, the fluid loss reduction performance is poor, indicating that the performance of the commercially available fluid loss agent is not as good as the modified fluid loss agent prepared in the present application.

[0046] Comparative Example 2 is different from Example 8 in that the 2,2-dihydroxymethylpropionic acid added in the modified fluid loss reducer step S1 is replaced by propionic acid. Replacing 2,2-dihydroxymethylpropionic acid with propionic acid cannot form a hyperbranched structure, so the fluid loss reduction performance is poor.

[0047] Comparative Examples 3 and 4 are different from those of Example 8. It can be seen from the data in Table 1 that the filtration loss reduction performance is not as good as the polysulfonated drilling fluid prepared in this application. This is because the hydroxyl groups in the hyperbranched structure are adsorbed on the surface of clay particles through hydrogen bonds to form a dense hydration film, which reduces the filter cake permeability; at the same time, the steric hindrance effect of the hyperbranched molecular chain reduces the curling of the molecular chain at high temperature and maintains the filtration loss reduction performance; furthermore, the hyperbranched molecules are embedded in the microcracks of the formation through multi-stage branches to form a "physical barrier", which reduces the intrusion of filtrate and inhibits the hydration and expansion of shale. The Si-O bond energy of siloxane is high, and it is not easy to break at high temperature. It can stabilize the filter cake structure and adapt to the high temperature environment of deep wells. Siloxane and the silicon hydroxyl groups on the surface of clay particles in the drilling fluid form stable chemical bonds through condensation reaction to enhance the adsorption strength; the hydrophobic group of siloxane can shield the charge neutralization effect of salt ions on clay particles and inhibit clay flocculation. Starch molecules physically block the pores of the filter cake, reducing the intrusion of filtrate into the formation, while providing biodegradability and reducing environmental burden.

[0048] Comparative Example 5 is a hyperbranched polymer fluid loss reducer prepared using the raw materials and method of Example 1 in Publication No. CN113527575A. As can be seen from the data in Table 1, the fluid loss reduction performance is average.

[0049] Comparative Examples 6, 7, and 8 are different from Example 8, and the difference is that no octanoic acid, stearic acid, or 3-aminopropyltriethoxysilane is added during the preparation of the modified emulsifier; it can be seen from the data in Table 1 that the fluid loss reduction performance is not as good as the polysulfonated drilling fluid prepared in the present application. This is because the surface of the nano-silica modified by the silane coupling agent forms an organic-inorganic hybrid structure, which is adsorbed on the oil-water interface through hydrogen bonding and hydrophobic effects, effectively reducing the interfacial tension and inhibiting the aggregation of droplets. The long alkyl chain of stearic acid and the short chain of octanoic acid synergistically form a dense interfacial film, which improves the stability of the emulsion in high temperature and high salt environments. The Si-O bond in the silane coupling agent has high thermal stability, which can protect the nano-silica from agglomeration at high temperatures and maintain the structural integrity of the emulsifier. The modified nano-silica is physically filled and chemically adsorbed in the pores of the mud cake to form a low-permeability filter cake, which can reduce the high temperature and high pressure fluid loss. The hydrophobic chains of stearic acid form a thermal barrier layer, reducing the damage of high temperature to the thermodynamic equilibrium of the emulsion.

[0050] Comparative Example 9 is a high-temperature resistant and high-density formate polysulfone drilling fluid prepared using the raw materials and method of Example 2 in Publication No. CN102766446A. It can be seen from the data in Table 1 that the filtration loss reduction performance is not as good as that of the present application.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. However, any equivalent changes, modifications and evolutions made by ordinary technicians in the field without departing from the scope of the technical solution of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A deep well polysulfone drilling fluid, characterized in that: The invention comprises the following raw materials in parts by weight: Deionized water: 100 parts, bentonite: 3-5 parts, modified fluid loss agent: 5-8 parts, modified emulsifier: 3-5 parts, pH regulator: 0.5-2 parts, lubricant: 2-3 parts, plugging agent: 2-6 parts, barite powder: 250-300 parts; The modified fluid loss reducer is prepared by the following method: S1: Under nitrogen protection, 2,2-dihydroxymethylpropionic acid and 2-methyl-2-acrylate-2,3-dihydroxypropyl ester are catalyzed by p-toluenesulfonic acid to generate hyperbranched products; S2: corn starch is acidified under the action of dilute hydrochloric acid to obtain acid-hydrolyzed starch, and the acid-hydrolyzed starch is reacted with chlorophenyltriethoxysilane to obtain silane-modified acid-hydrolyzed starch; S3: Silane-modified acid-hydrolyzed starch and hyperbranched product react with sodium hydroxide to generate silanized hyperbranched product; S4: Acrylamide, sodium p-styrene sulfonate, allyloxy polyoxyethylene ether, and silylated hyperbranched products react under the action of ammonium persulfate to generate a modified fluid loss reducer.

2. A deep well polysulfone drilling fluid according to claim 1, characterized in that: In step S1, the feed mass ratio of 2,2-dihydroxymethylpropionic acid to 2-methyl-2-acrylate-2,3-dihydroxypropyl ester is 5:(25-30).

3. The deep well polysulfone drilling fluid according to claim 1, characterized in that: In step S2, the mass ratio of the acid-hydrolyzed starch to chlorophenyltriethoxysilane is (12-16):

10.

4. The deep well polysulfone drilling fluid according to claim 1, characterized in that: In step S3, the feed mass ratio of the silane-modified acid-hydrolyzed starch to the hyperbranched product is 20:(3-5).

5. The deep well polysulfone drilling fluid according to claim 1, characterized in that: In step S4, the feed mass ratio of acrylamide, sodium p-styrene sulfonate, allyloxy polyoxyethylene ether, and silylated hyperbranched product is (30-40):(20-25):(2-5):

2.

6. The deep well polysulfone drilling fluid according to claim 1, characterized in that: The modified emulsifier is prepared by the following method: A1: 3-aminopropyltriethoxysilane is hydrolyzed to generate 3-aminopropylsilanetriol, which is then modified with nano-silica to obtain modified nano-silica; A2: Modified nano-silica reacts with stearic acid and caprylic acid to obtain a modified emulsifier.

7. A deep well polysulfone drilling fluid according to claim 6, characterized in that: In step A1, the mass ratio of the 3-aminopropyltriethoxysilane to the nano-silicon dioxide is (0.5-2):

10.

8. The deep well polysulfone drilling fluid according to claim 6, characterized in that: In step A2, the mass ratio of the modified nano-silicon dioxide, stearic acid and octanoic acid is 20:(6-10):(3-5).

9. The deep well polysulfone drilling fluid according to claim 1, characterized in that: The pH regulator is a combination of one or more of potassium carbonate, potassium hydroxide, and sodium hydroxide; the lubricant is white mineral oil; and the plugging agent is sulfonated asphalt.

10. A method for preparing the deep well polysulfone drilling fluid according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) Weigh by weight: deionized water: 100 parts, bentonite: 3-5 parts, modified fluid loss reducer: 5-8 parts, modified emulsifier: 3-5 parts, pH adjuster: 0.5-2 parts, lubricant: 2-3 parts, plugging agent: 2-6 parts, barite powder: 250-300 parts; (2) Add deionized water to the container, add bentonite while stirring, stop stirring after stirring for 15-25 minutes, and seal and cure for 24 hours to obtain prehydrated bentonite slurry; add pH adjuster, modified filtrate reducer, modified emulsifier, plugging agent, and lubricant to the prehydrated bentonite slurry in the above proportions, stir at high speed for 50-70 minutes, and finally add barite powder and stir evenly to obtain deep well polysulfone drilling fluid.

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