A deep well polysulfonate drilling fluid and its preparation method

Abstract

The present invention discloses a deep well polysulfonate drilling fluid and a preparation method thereof, relating to the technical field of drilling fluids. A 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 filtration 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; in the present invention, a hyperbranched product is generated by the reaction of 2,2 - dimethylolpropionic acid and 2 - hydroxypropyl methacrylate; then, chlorophenyltriethoxysilane is grafted onto acid hydrolyzed starch to obtain silane - modified acid hydrolyzed starch; the silane - modified acid hydrolyzed starch reacts with the hyperbranched product to generate a silanized hyperbranched product; acrylamide, sodium p - styrenesulfonate, allyloxy polyoxyethylene ether, and the silanized hyperbranched product react to generate a modified filtration reducer. The drilling fluid prepared by the present invention has good filtration reduction performance.

Description

Technical Field

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

[0002] The Tarim Basin is an important area rich in oil and gas resources in China. Its deep formations have geological characteristics such as ultra-deep, ultra-high temperature, ultra-high pressure, complex lithology, diverse fluids, and complex stresses. During the process of deep well drilling, drilling fluid technology faces many challenges. First, a large number of micro-fractured dolomites are developed in the Cambrian formation, and the drilling fluid needs to have good plugging performance to prevent wellbore collapse. Second, thin-layer gypsum is prone to dissolution under the action of the drilling fluid, resulting in wellbore instability, which poses higher requirements for the inhibition and stability of the drilling fluid. In addition, the high-temperature environment (exceeding 200 °C) in the deep wells of the Tarim Basin poses severe tests on the high-temperature stability, rheological properties, and filtration control ability of the drilling fluid. At the same time, the drilling fluid is easily contaminated in high-salt formations, resulting in performance degradation and affecting drilling efficiency. These complex geological conditions pose extremely high requirements for the formulation design and performance optimization of deep well polysulfonate drilling fluids. To solve the above problems, it is particularly important to develop a high-performance deep well polysulfonate drilling fluid system.

[0003] Chinese Patent No. CN102766446A discloses a high-temperature resistant and high-density formate polysulfonate drilling fluid and a preparation method thereof. The high-temperature resistant and high-density formate polysulfonate 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 regulator, and 120 - 270 parts of barite powder; the drilling fluid prepared by this patent has poor filtration reduction performance. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a deep well polysulfonate drilling fluid and a preparation method thereof.

[0005] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0006] A deep well polysulfonate drilling fluid, comprising the following raw materials in parts by weight:

[0007] Deionized water: 100 parts, bentonite: 3 - 5 parts, modified filtration reducer: 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;

[0008] The modified filtration reducer is prepared by the following method:

[0009] S1: Under nitrogen protection, 2,2-bis(hydroxymethyl)propionic acid and 2,3-dihydroxypropyl 2-methylacrylate react to form a hyperbranched product under the catalysis of p-toluenesulfonic acid;

[0010] S2: Corn starch is acidified with dilute hydrochloric acid to obtain acid-hydrolyzed starch, and the acid-hydrolyzed starch reacts with chlorophenyltriethoxysilane to obtain silane-modified acid-hydrolyzed starch;

[0011] S3: The silane-modified acid-hydrolyzed starch and the hyperbranched product react under the action of sodium hydroxide to form a silylated hyperbranched product;

[0012] S4: Acrylamide, sodium p-styrenesulfonate, allyloxy polyoxyethylene ether, and the silylated hyperbranched product react under the action of ammonium persulfate to form a modified filtrate reducer.

[0013] In step S1, the feeding mass ratio of 2,2-bis(hydroxymethyl)propionic acid to 2,3-dihydroxypropyl 2-methylacrylate is 5:(25 - 30).

[0014] In step S2, the feeding mass ratio of the acid-hydrolyzed starch to chlorophenyltriethoxysilane is (12 - 16):10.

[0015] In step S3, the feeding mass ratio of the silane-modified acid-hydrolyzed starch to the hyperbranched product is 20:(3 - 5).

[0016] In step S4, the feeding mass ratio of acrylamide, sodium p-styrenesulfonate, allyloxy polyoxyethylene ether, and the silylated hyperbranched product is (30 - 40):(20 - 25):(2 - 5):2.

[0017] The modified emulsifier is prepared by the following method:

[0018] A1: 3-aminopropyltriethoxysilane is hydrolyzed to form 3-aminopropylsilanetriol, and then it is modified with nano-silica to obtain modified nano-silica;

[0019] A2: The modified nano-silica reacts with stearic acid and octanoic acid to obtain the modified emulsifier.

[0020] In step A1, the feeding mass ratio of 3-aminopropyltriethoxysilane to nano-silica is (0.5 - 2):10.

[0021] In step A2, the feeding mass ratio of the modified nano-silica, stearic acid, and octanoic acid is 20:(6 - 10):(3 - 5).

[0022] The pH regulator is one or a combination of potassium carbonate, potassium hydroxide, and sodium hydroxide; the lubricant is white mineral oil; the plugging agent is sulfonated asphalt.

[0023] A preparation method of a deep well polysulfonate drilling fluid includes the following steps:

[0024] (1) Weigh by parts by weight: deionized water: 100 parts, bentonite: 3 - 5 parts, modified filtration loss reducer: 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;

[0025] (2) Add deionized water to a container, add bentonite while stirring, stop stirring after stirring for 15 - 25 min, and obtain pre - hydrated bentonite slurry after hermetically curing for 24 h; sequentially add the pH regulator, modified filtration loss reducer, modified emulsifier, plugging agent, and lubricant to the pre - hydrated bentonite slurry according to the above ratios, stir at high speed for 50 - 70 min, and finally add barite powder and stir evenly to obtain the deep well polysulfonate drilling fluid.

[0026] Due to the adoption of the above technical solutions, the beneficial effects of the present invention include:

[0027] (1) In the present invention, a hyperbranched product is generated by the reaction of 2,2 - dimethylolpropionic acid and 2 - hydroxypropyl methacrylate; corn starch is acidified to obtain acid - hydrolyzed starch, and the hydroxyl group in the acid - hydrolyzed starch reacts with the siloxy group in chlorophenyltriethoxysilane to obtain silane - modified acid - hydrolyzed starch; the chlorine atom in the silane - modified acid - hydrolyzed starch undergoes a substitution reaction with the hydroxyl group in the hyperbranched product to generate a silylated hyperbranched product; acrylamide, sodium p - styrenesulfonate, allyloxy polyoxyethylene ether, and the silylated hyperbranched product undergo a free - radical polymerization reaction under the action of ammonium persulfate to generate a modified filtration loss reducer.

[0028] (2) 3 - aminopropyltriethoxysilane is hydrolyzed to generate 3 - aminopropylsilanetriol, and then it is modified with nano - silica to obtain modified nano - silica; the modified nano - silica reacts with stearic acid and octanoic acid to obtain a modified emulsifier.

[0029] (3) The modified filtration loss reducer prepared by the present invention exhibits excellent filtration loss reduction performance in the drilling fluid through its unique three - dimensional network structure: the hyperbranched molecules and starch cooperate to construct a dense filter cake, the hydroxyl groups strengthen the bridging plugging of clay particles through hydrogen bonds, the siloxane segments precisely regulate the pore structure of the filter cake through hydrophobic association, realizing nano - scale pore throat plugging; the internal cavity of its molecules and the synergistic effect of hydroxyl - siloxane form a thermally stable complex, enabling the filter cake to maintain low permeability at high temperatures, and at the same time, the hyperbranched structure endows the system with salt pollution resistance through volume exclusion effect and dynamic cross - linked network, significantly reducing the filtration loss of the drilling fluid.

[0030] (4) An organic-inorganic hybrid structure is formed on the surface of nano-silica modified by silane coupling agent, which adsorbs on the oil-water interface through hydrogen bonding and hydrophobic interaction, effectively reducing the interfacial tension and inhibiting droplet aggregation. The long alkyl chain of stearic acid and the short chain of octanoic acid act synergistically to form a dense interfacial film, improving the stability of the emulsion in high-temperature and high-salt environments. Specific Embodiments

[0031] The following is further described in conjunction with embodiments, but the present invention is not limited to these embodiments.

[0032] Example 1 Preparation of Modified Filtration Loss Reducer:

[0033] S1: Under nitrogen protection, 1000 g of toluene, 50 g of 2,2-dimethylolpropionic acid, and 250 g of 2,3-dihydroxypropyl 2-methyl-2-propenoate were added to a reactor, stirred and mixed evenly, heated to reflux, and then 8 g of p-toluenesulfonic acid was added. After reacting for 6 h (using a water separator to remove the generated water during the reaction), the temperature was lowered to room temperature, and 10 wt% sodium bicarbonate solution was slowly added to adjust the pH to neutral (neutral in this application means pH = 7), stirred thoroughly for 30 min, allowed to stand for layer separation, and the organic phase was transferred to a rotary evaporator, distilled under reduced pressure at 55 °C for 3 h, and dried in vacuum at 70 °C for 2 h to obtain a hyperbranched polymer; the reaction equation is shown as follows:

[0034]

[0035] It should be noted that the reaction process of the hyperbranched reaction is relatively complex, and the above structure is only used to understand the reaction site situation of this application.

[0036] S2: 80 g of corn starch and 200 ml of 0.25 mol / L dilute hydrochloric acid were added to a reactor, stirred and mixed evenly, heated to 50 °C, reacted for 4 h, then cooled to room temperature, 5 wt% NaOH solution was slowly added to adjust the pH to 7.0, 200 ml of absolute ethanol was slowly added at 0 °C, stirred for 20 min, filtered by suction, and dried in vacuum at 70 °C for 2 h to obtain acid-hydrolyzed starch; under nitrogen protection, 1000 g of toluene and 120 g of acid-hydrolyzed starch were added to a reactor, stirred and heated to 60 °C, kept warm for 1 h, then 100 g of chlorophenyltriethoxysilane and 6 g of catalyst p-toluenesulfonic acid were added, heated to 80 °C, reacted for 6 h, then cooled to room temperature, 10 wt% sodium bicarbonate solution was added to adjust the pH to 7.0, stirred for 30 min, the reaction solution was poured into 2000 ml of absolute ethanol, allowed to stand for 1 h, centrifuged, washed three times with 300 ml of ethanol-water (ethanol:water (v / v) = 7:3), and dried in vacuum at 50 °C for 4 h to obtain silane-modified acid-hydrolyzed starch;

[0037] S3: Under nitrogen protection, add 1000 g of toluene, 200 g of silane-modified acid-hydrolyzed starch, and 30 g of hyperbranched product into the reactor. Stir to mix evenly, heat up to 80 °C, react for 4 h, then cool down to 60 °C, slowly add 40 g of 42 wt% sodium hydroxide solution dropwise over 10 min. After dropping, continue to react at 80 °C for 2 h, then cool to room temperature, slowly add 1 M dilute hydrochloric acid solution to adjust the pH to neutral; let it stand for layering, separate the aqueous phase, retain the organic phase, carry out vacuum distillation at 70 °C for 2 h, then add 200 ml of saturated sodium chloride solution for washing, repeat three times, and carry out vacuum drying at 70 °C for 3 h to obtain the silylated hyperbranched product;

[0038] S4: Under nitrogen protection, add 2000 g of deionized water, 300 g of acrylamide, 200 g of sodium p-styrenesulfonate, 20 g of allyloxy polyoxyethylene ether, and 20 g of silylated hyperbranched product into the reactor. Stir to mix evenly, heat up to 80 °C, then add 10 g of ammonium persulfate, react for 4 h, add 5000 ml of absolute ethanol, stir for 20 min, let it stand for 1 h, filter by suction, and carry out vacuum drying at 70 °C for 3 h to obtain the modified filtration reducer.

[0039] Example 2 Preparation of modified filtration reducer:

[0040] S1: Under nitrogen protection, add 1000 g of toluene, 50 g of 2,2-dimethylolpropionic acid, and 280 g of 2,3-dihydroxypropyl 2-methylacrylate into the reactor. Stir to mix evenly, heat up to reflux, then add 10 g of p-toluenesulfonic acid, react for 6 h (remove the generated water using a water separator during the reaction), then cool to room temperature, slowly add 10 wt% sodium bicarbonate solution to adjust the pH to neutral, stir well for 30 min, let it stand for layering, transfer the organic phase to a rotary evaporator, carry out vacuum distillation at 60 °C for 2 h, and carry out vacuum drying at 60 °C for 3 h to obtain the hyperbranched polymer;

[0041] S2: Add 80 g of corn starch and 200 ml of 0.25 mol / L dilute hydrochloric acid into the reactor. Stir to mix evenly, heat up to 50 °C, react for 4 h, then cool to room temperature, slowly add 5 wt% NaOH solution to adjust the pH to 7.0, slowly add 200 ml of absolute ethanol at 0 °C, stir for 20 min, filter by suction, and carry out vacuum drying at 70 °C for 2 h to obtain acid-hydrolyzed starch; Under nitrogen protection, add 1000 g of toluene and 140 g of acid-hydrolyzed starch into the reactor, stir and heat up to 60 °C, keep warm for 1 h, then add 100 g of chlorophenyltriethoxysilane and 6 g of catalyst p-toluenesulfonic acid, heat up to 85 °C, react for 5 h, then cool to room temperature, add 10 wt% sodium bicarbonate solution to adjust the pH to 7.0, stir for 30 min, pour the reaction solution into 2000 ml of absolute ethanol, let it stand for 1 h, centrifuge, wash three times with 300 ml of ethanol-water (ethanol:water (v / v)=7:3), and carry out vacuum drying at 60 °C for 3 h to obtain the silane-modified acid-hydrolyzed starch;

[0042] S3: Under nitrogen protection, add 1000 g of toluene, 200 g of silane-modified acid-hydrolyzed starch, and 40 g of hyperbranched product into the reactor, stir to mix evenly, heat up to 85 °C, after reacting for 3 h, cool down to 60 °C, slowly add 45 g of 42 wt% sodium hydroxide solution dropwise, add dropwise for 10 min, after dropping, continue to react at 85 °C for 1.5 h, then cool to room temperature, slowly add 1 M dilute hydrochloric acid solution to adjust the pH to neutral; let it stand for stratification, separate the aqueous phase, retain the organic phase, carry out vacuum distillation at 60 °C for 2.5 h, then add 200 ml of saturated sodium chloride solution for washing, repeat three times, and dry in vacuum at 80 °C for 2 h to obtain the silylated hyperbranched product;

[0043] S4: Under nitrogen protection, add 2000 g of deionized water, 350 g of acrylamide, 220 g of sodium p-styrenesulfonate, 30 g of allyloxy polyoxyethylene ether, and 20 g of silylated hyperbranched product into the reactor, stir to mix evenly, heat up to 85 °C, then add 10 g of ammonium persulfate, after reacting for 3 h, add 5000 ml of absolute ethanol, stir for 20 min, let it stand for 1 h, filter by suction, and dry in vacuum at 60 °C for 4 h to obtain the modified fluid loss reducer.

[0044] Example 3 Preparation of the modified fluid loss reducer:

[0045] S1: Under nitrogen protection, add 1000 g of toluene, 50 g of 2,2-dimethylolpropionic acid, and 300 g of 2-hydroxypropyl methacrylate into the reactor, stir to mix evenly, heat up to reflux, then add 12 g of p-toluenesulfonic acid, after reacting for 6 h (remove the generated water using a water separator during the reaction), cool down to room temperature, slowly add 10 wt% sodium bicarbonate solution to adjust the pH to neutral, stir well for 30 min, let it stand for stratification, transfer the organic phase to a rotary evaporator, carry out vacuum distillation at 60 °C for 2 h, and dry in vacuum at 50 °C for 4 h to obtain the hyperbranched polymer;

[0046] S2: Add 80 g of corn starch and 200 ml of 0.2 mol / L dilute hydrochloric acid into the reactor, stir to mix evenly, heat up to 50 °C, after reacting for 4 h, cool down to room temperature, slowly add 5 wt% NaOH solution to adjust the pH to 7.0, slowly add 200 ml of absolute ethanol at 0 °C, stir for 20 min, filter by suction, and dry in vacuum at 70 °C for 2 h to obtain acidified starch; Under nitrogen protection, add 1000 g of toluene and 160 g of acid-hydrolyzed starch into the reactor, stir and heat up to 60 °C, keep the temperature for 1 h, then add 100 g of chlorophenyltriethoxysilane and 8 g of catalyst p-toluenesulfonic acid, heat up to 85 °C, after reacting for 5 h, cool down to room temperature, add 10 wt% sodium bicarbonate solution to adjust the pH to 7.0, stir for 30 min, pour the reaction solution into 2000 ml of absolute ethanol, let it stand for 1 h, centrifuge, wash three times with 300 ml of ethanol-water (ethanol: water (v / v) = 7:3), and dry in vacuum at 70 °C for 2 h to obtain silane-modified acid-hydrolyzed starch;

[0047] S3: Under nitrogen protection, add 1000 g of toluene, 200 g of silane-modified acid-hydrolyzed starch, and 50 g of hyperbranched product into the reactor, stir to mix evenly, heat up to 90 °C, after reacting for 2 h, cool down to 60 °C, slowly dropwise add 50 g of 42 wt% sodium hydroxide solution, the dropping time is 10 min, after dropping, continue to react at 90 °C for 1 h, then cool down to room temperature, slowly add 1 M dilute hydrochloric acid solution to adjust the pH to neutral; Let it stand for stratification, separate the aqueous phase, retain the organic phase, distill under reduced pressure at 60 °C for 3 h, then add 200 ml of saturated sodium chloride solution for washing, repeat three times, and dry in vacuum at 90 °C for 1 h to obtain silanized hyperbranched product;

[0048] S4: Under nitrogen protection, add 2000 g of deionized water, 400 g of acrylamide, 250 g of sodium p-styrenesulfonate, 50 g of allyloxypolyethylene ether, and 20 g of silanized hyperbranched product into the reactor, stir to mix evenly, heat up to 90 °C, then add 10 g of ammonium persulfate, after reacting for 2 h, add 5000 ml of absolute ethanol, stir for 20 min, let it stand for 1 h, filter by suction, and dry in vacuum at 50 °C for 5 h to obtain the modified fluid loss reducer.

[0049] Example 4 Preparation of modified emulsifier:

[0050] A1: Weigh 5 g of 3-aminopropyltriethoxysilane, add 500 ml of deionized water, and stir at 40 °C for 3 h to obtain 3-aminopropylsilanetriol; 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 min to obtain a nano-silica dispersion; slowly add 3-aminopropylsilanetriol dropwise to the nano-silica dispersion. After 20 min of dropping, stir evenly, raise the temperature to 80 °C, react for 10 h, cool to room temperature, filter by suction, wash with deionized water 3 times (200 ml of deionized water each time), dry in vacuum at 80 °C for 4 h, and sieve through a 80-mesh sieve to obtain modified nano-silica;

[0051] A2: Add 1000 ml of toluene, 200 g of modified nano-silica, 30 g of octanoic acid, and 60 g of stearic acid into a reactor, stir evenly, raise the temperature to reflux and react for 8 h, then cool to room temperature, centrifuge, wash successively with 300 ml of absolute ethanol and 100 ml of acetone, and dry in vacuum at 50 °C for 5 h to obtain a modified emulsifier.

[0052] Example 5 Preparation of modified emulsifier:

[0053] A1: Weigh 10 g of 3-aminopropyltriethoxysilane, add 500 ml of deionized water, and stir at 40 °C for 3 h to obtain 3-aminopropylsilanetriol; 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 min to obtain a nano-silica dispersion; slowly add 3-aminopropylsilanetriol dropwise to the nano-silica dispersion. After 20 min of dropping, stir evenly, raise the temperature to 90 °C, react for 8 h, cool to room temperature, filter by suction, wash with deionized water 3 times (200 ml of deionized water each time), dry in vacuum at 70 °C for 5 h, and sieve through a 80-mesh sieve to obtain modified nano-silica;

[0054] A2: Add 1000 ml of toluene, 200 g of modified nano-silica, 40 g of octanoic acid, and 80 g of stearic acid into a reactor, stir evenly, raise the temperature to reflux and react for 6 h, then cool to room temperature, centrifuge, wash successively with 300 ml of absolute ethanol and 100 ml of acetone, and dry in vacuum at 60 °C for 4 h to obtain a modified emulsifier.

[0055] Example 6 Preparation of modified emulsifier:

[0056] A1: Weigh 20 g of 3-aminopropyltriethoxysilane, add 500 ml of deionized water, and stir at 40 °C for 3 h to obtain 3-aminopropylsilanetriol; 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 min to obtain a nano-silica dispersion; slowly drip 3-aminopropylsilanetriol into the nano-silica dispersion. After dripping for 20 min, stir evenly, heat up to 100 °C, react for 6 h, then cool to room temperature, filter by suction, wash with deionized water 3 times (200 ml of deionized water is used each time), dry in vacuum at 60 °C for 6 h, and sieve through a 80-mesh sieve to obtain modified nano-silica;

[0057] A2: Add 1000 ml of toluene, 200 g of modified nano-silica, 50 g of octanoic acid, and 100 g of stearic acid into a reactor, stir evenly, heat up to reflux and react for 4 h, then cool to room temperature, centrifuge, wash successively with 300 ml of absolute ethanol and 100 ml of acetone, and dry in vacuum at 70 °C for 3 h to obtain a modified emulsifier.

[0058] Example 7 Preparation of deep well polysulfonate drilling fluid:

[0059] (1) Weigh: deionized water: 1000 g, bentonite: 30 g, modified filtrate reducer (prepared in Example 1): 50 g, modified emulsifier (prepared in Example 4): 30 g, pH regulator (potassium carbonate): 5 g, lubricant (white mineral oil): 20 g, plugging agent (sulfonated asphalt): 20 g, barite powder: 2500 g;

[0060] (2) At room temperature, add deionized water into a container, add bentonite while stirring, stop stirring after stirring for 15 min, and seal and cure for 24 h to obtain pre-hydrated bentonite slurry; add the pH regulator, modified filtrate reducer, modified emulsifier, plugging agent, and lubricant into the pre-hydrated bentonite slurry in the above proportions in sequence, stir at a high speed of 8000 r / min for 50 min, and finally add barite powder and stir evenly to obtain deep well polysulfonate drilling fluid.

[0061] Example 8 Preparation of deep well polysulfonate drilling fluid:

[0062] (1) Weigh: deionized water: 1000 g, bentonite: 40 g, modified filtrate reducer (prepared in Example 2): 60 g, modified emulsifier (prepared in Example 5): 40 g, pH regulator (potassium hydroxide): 10 g, lubricant (white mineral oil): 25 g, plugging agent (sulfonated asphalt): 40 g, barite powder: 2800 g;

[0063] (2) At room temperature, add deionized water to the container, add bentonite while stirring, stop stirring after 20 minutes of stirring, and perform airtight curing for 24 hours to obtain pre-hydrated bentonite slurry; add a pH regulator, a modified filtration loss reducer, a modified emulsifier, a plugging agent, and a lubricant to the pre-hydrated bentonite slurry in the above proportions in sequence, stir at a high speed for 60 minutes, with a rotation speed of 8000 r / min, and finally add barite powder and stir evenly to obtain a deep well polysulfonate drilling fluid.

[0064] Example 9 Preparation of deep well polysulfonate drilling fluid:

[0065] (1) Weigh: deionized water: 1000 g, bentonite: 50 g, modified filtration loss reducer (prepared in Example 3): 80 g, modified emulsifier (prepared in Example 6): 50 g, pH regulator (sodium hydroxide): 20 g, lubricant (white mineral oil): 30 g, plugging agent (sulfonated asphalt): 60 g, barite powder: 3000 g;

[0066] (2) At room temperature, add deionized water to the container, add bentonite while stirring, stop stirring after 25 minutes of stirring, and perform airtight curing for 24 hours to obtain pre-hydrated bentonite slurry; add a pH regulator, a modified filtration loss reducer, a modified emulsifier, a plugging agent, and a lubricant to the pre-hydrated bentonite slurry in the above proportions in sequence, stir at a high speed for 70 minutes, with a rotation speed of 8000 r / min, and finally add barite powder and stir evenly to obtain a deep well polysulfonate drilling fluid.

[0067] Comparative Example 1

[0068] A preparation method of a deep well polysulfonate drilling fluid is basically the same as that of Example 8, the difference is that the modified filtration loss reducer is replaced with a commercially available natural polymer filtration loss reducer HFLD-1 of equal weight.

[0069] Comparative Example 2

[0070] A preparation method of a deep well polysulfonate drilling fluid is basically the same as that of Example 8, the difference is that the modified filtration loss reducer is replaced with a modified filtration loss reducer prepared by the following method of equal weight:

[0071] The preparation method of the modified filtration loss reducer in this comparative example is basically the same as that of Example 2, the difference is that 2,2-dimethylolpropionic acid added in step S1 is replaced with 50 g of propionic acid.

[0072] Comparative Example 3

[0073] A preparation method of a deep well polysulfonate drilling fluid is basically the same as that of Example 8, the difference is that the modified filtration loss reducer is replaced with a modified filtration loss reducer prepared by the following method of equal weight:

[0074] S1: Under nitrogen protection, add 1000 g of toluene, 50 g of 2,2 - bis(hydroxymethyl)propionic acid, and 280 g of 2 - hydroxypropyl 2 - methylacrylate into the reactor, stir to mix evenly, heat up to reflux, then add 10 g of p - toluenesulfonic acid, react for 6 h (remove the generated water using a water separator during the reaction), then cool to room temperature, slowly add 10 wt% sodium bicarbonate solution to adjust the pH to neutral, stir well for 30 min, let it stand for phase separation, transfer the organic phase to a rotary evaporator, distill under reduced pressure at 60 °C for 2 h, and dry in vacuum at 60 °C for 3 h to obtain the hyperbranched polymer;

[0075] S2: Under nitrogen protection, add 1000 g of toluene, 200 g of chlorophenyltriethoxysilane, and 40 g of the hyperbranched product into the reactor, stir to mix evenly, heat up to 85 °C, react for 3 h, then cool to 60 °C, slowly dropwise add 45 g of 42 wt% sodium hydroxide solution over 10 min, after dropping, continue to react at 85 °C for 1.5 h, then cool to room temperature, slowly add 1 M dilute hydrochloric acid solution to adjust the pH to neutral; let it stand for phase separation, separate the aqueous phase, retain the organic phase, distill under reduced pressure at 60 °C for 2.5 h, then add 200 ml of saturated sodium chloride solution for washing, repeat three times, and dry in vacuum at 80 °C for 2 h to obtain Intermediate 1;

[0076] S3: Under nitrogen protection, add 2000 g of deionized water, 350 g of acrylamide, 220 g of sodium p - styrenesulfonate, 30 g of allyloxy polyoxyethylene ether, and 20 g of Intermediate 1 into the reactor, stir to mix evenly, heat up to 85 °C, then add 10 g of ammonium persulfate, react for 3 h, add 5000 ml of absolute ethanol, stir for 20 min, let it stand for 1 h, filter by suction, and dry in vacuum at 60 °C for 4 h to obtain the modified fluid loss reducer.

[0077] Comparative Example 4

[0078] A preparation method of a deep - well polysulfonate drilling fluid is basically the same as that of Example 8, the difference is that the modified fluid loss reducer is replaced with a modified fluid loss reducer prepared by the following method with the same weight:

[0079] The preparation method of the modified fluid loss reducer in this comparative example is basically the same as that of Example 2, the difference is that the acid - hydrolyzed starch added in step S2 is replaced with chitosan with the same weight.

[0080] Comparative Example 5

[0081] A preparation method of a deep - well polysulfonate drilling fluid is basically the same as that of Example 8, the difference is that the modified fluid loss reducer is replaced with a hyperbranched polymer fluid loss reducer prepared in Example 1 of CN113527575A.

[0082] Comparative Example 6

[0083] The preparation method of a deep well polysulfonate drilling fluid is basically the same as that of Example 8, except that the modified emulsifier is replaced by a modified emulsifier prepared by the following method:

[0084] A1: Weigh 10 g of 3-aminopropyltriethoxysilane, add 500 ml of deionized water, and stir at 40 °C for 3 h to obtain 3-aminopropylsilanetriol; 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 min to obtain a nano-silica dispersion; slowly drop 3-aminopropylsilanetriol into the nano-silica dispersion. After dropping for 20 min, stir and mix evenly, raise the temperature to 90 °C, react for 8 h, cool to room temperature, filter by suction, wash with deionized water 3 times (using 200 ml of deionized water each time), dry in vacuum at 70 °C for 5 h, and sieve through an 80-mesh sieve to obtain modified nano-silica;

[0085] A2: Add 1000 ml of toluene, 200 g of modified nano-silica, and 80 g of stearic acid into a reactor, stir and mix evenly, raise the temperature to reflux and react for 6 h, then cool to room temperature, centrifuge, wash successively with 300 ml of absolute ethanol and 100 ml of acetone, and dry in vacuum at 60 °C for 4 h to obtain a modified emulsifier.

[0086] Comparative Example 7

[0087] The preparation method of a deep well polysulfonate drilling fluid is basically the same as that of Example 8, except that the modified emulsifier is replaced by a modified emulsifier prepared by the following method:

[0088] A1: Weigh 10 g of 3-aminopropyltriethoxysilane, add 500 ml of deionized water, and stir at 40 °C for 3 h to obtain 3-aminopropylsilanetriol; 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 min to obtain a nano-silica dispersion; slowly drop 3-aminopropylsilanetriol into the nano-silica dispersion. After dropping for 20 min, stir and mix evenly, raise the temperature to 90 °C, react for 8 h, cool to room temperature, filter by suction, wash with deionized water 3 times (using 200 ml of deionized water each time), dry in vacuum at 70 °C for 5 h, and sieve through an 80-mesh sieve to obtain modified nano-silica;

[0089] A2: Add 1000 ml of toluene, 200 g of modified nano-silica, and 40 g of octanoic acid into a reactor, stir and mix evenly, raise the temperature to reflux and react for 6 h, then cool to room temperature, centrifuge, wash successively with 300 ml of absolute ethanol and 100 ml of acetone, and dry in vacuum at 60 °C for 4 h to obtain a modified emulsifier.

[0090] Comparative Example 8

[0091] The preparation method of a deep well polysulfonate drilling fluid is basically the same as that of Example 8, except that the modified emulsifier is replaced with a modified emulsifier prepared by the following method:

[0092] 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 min 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 the reactor, stir and mix evenly, heat up to reflux and react for 6 h, then cool to room temperature, centrifuge, wash successively with 300 ml of absolute ethanol and 100 ml of acetone, and vacuum dry at 60 °C for 4 h to obtain the modified emulsifier.

[0093] Comparative Example 9

[0094] A high-temperature resistant and high-density formate polysulfonate drilling fluid prepared by using the raw materials and method of Example 2 in the publication No. CN102766446A.

[0095] The bentonite model used in the examples and comparative examples of this application is Bentone 38; the particle size of the barite powder used in the examples and comparative examples of this application is 400 mesh, produced by Shijiazhuang Mayue Building Materials Co., Ltd.; the nano-silica used in the examples and comparative examples of this application is hydroxyl-modified nano-silica, with the model of As-200, produced by Shenyang Chemical Industry Co., Ltd.; the sulfonated asphalt model used in the examples and comparative examples of this application is BFT-1, purchased from Tianjin Binpu Technology Development Co., Ltd.; the natural polymer filtration reducer HFLD-1 used in the comparative example is purchased from Zhengzhou Jingyuan Mud Material Co., Ltd.; the 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 absolute ethanol without special instructions.

[0096] Perform experimental tests on the apparent viscosity, plastic viscosity, dynamic shear force, and high-temperature and high-pressure filtration loss volume of the deep well polysulfonate drilling fluids prepared in the examples and comparative examples, and the test results are shown in Table 1.

[0097] The experiment is carried out in accordance with GB / T 16783.1-2014 "Petroleum and natural gas industries - Drilling fluids - Field testing - Part 1: Water-based drilling fluids".

[0098] Table 1

[0099]

[0100] As can be seen from Table 1, the apparent viscosity of the deep well polysulfonate drilling fluid prepared in this 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 being aged at 220 °C for 16 h, indicating that the prepared polysulfonate drilling fluid has excellent high temperature resistance performance.

[0101] Comparative Example 1 is a comparative example different from Example 8. The difference is that the modified fluid loss reducer is replaced with a commercially available natural polymer fluid loss reducer HFLD-1 of equal weight. As can be seen from Table 1, the fluid loss reduction performance is poor, indicating that the performance of the commercially available fluid loss reducer is inferior to that of the modified fluid loss reducer prepared in this application.

[0102] Comparative Example 2 is a comparative example different from Example 8. The difference is that 2,2-dimethylolpropionic acid added in step S1 of the modified fluid loss reducer is replaced with propionic acid. Replacing 2,2-dimethylolpropionic acid with propionic acid cannot form a hyperbranched structure, so the fluid loss reduction performance is poor.

[0103] Comparative Examples 3 and 4 are comparative examples different from Example 8. As can be seen from the data in Table 1, the fluid loss reduction performance is inferior to that of the polysulfonate drilling fluid prepared in this application. This is because the hydroxyl groups in the hyperbranched structure adsorb on the surface of clay particles through hydrogen bonds to form a dense hydration film, reducing the permeability of the filter cake; at the same time, the steric hindrance effect of the hyperbranched molecular chain reduces the curling of the molecular chain at high temperature, maintaining the fluid loss reduction performance; furthermore, the hyperbranched molecules embed into the microfractures of the formation through multi-level branches to form a "physical barrier", reducing the invasion of filtrate and inhibiting shale hydration swelling. The Si-O bond energy of siloxane is high and is not easily broken at high temperature, which can stabilize the filter cake structure and adapt to the high temperature environment of deep wells. Siloxane forms stable chemical bonds with the silanol groups on the surface of clay particles in the drilling fluid, enhancing the adsorption strength; the hydrophobic groups 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 invasion of filtrate into the formation, and at the same time providing biodegradability and reducing the environmental burden.

[0104] Comparative Example 5 is a hyperbranched polymer fluid loss reducer prepared using the raw materials and methods in Example 1 of CN113527575A. As can be seen from the data in Table 1, the fluid loss reduction performance is average.

[0105] Comparative Examples 6, 7, and 8 are comparative examples different from Example 8. The differences are that caprylic acid, stearic acid, and 3-aminopropyltriethoxysilane were not added during the preparation of the modified emulsifier. It can be seen from the data in Table 1 that the filtration reduction performance is inferior to that of the polysulfonate drilling fluid prepared in this application. This is because an organic-inorganic hybrid structure is formed on the surface of the nano-silica modified by the silane coupling agent, which is adsorbed at the oil-water interface through hydrogen bonding and hydrophobic interaction, effectively reducing the interfacial tension and inhibiting droplet aggregation. The long alkyl chain of stearic acid and the short chain of caprylic acid act synergistically to form a dense interfacial film, improving 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 forms a low-permeability filter cake in the pores of the mud cake through physical filling and chemical adsorption, which can reduce the filtration loss at high temperature and high pressure. The hydrophobic chain of stearic acid forms a thermal barrier layer, reducing the damage of high temperature to the thermodynamic equilibrium of the emulsion.

[0106] Comparative Example 9 is a high-temperature-resistant and high-density formate polysulfonate drilling fluid prepared by using the raw materials and methods in Example 2 of the patent with the publication number CN102766446A. It can be seen from the data in Table 1 that the filtration reduction performance is inferior to that of this application.

[0107] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. However, for those of ordinary skill in the art, without departing from the scope of the technical solution of the present invention, any minor changes, modifications, and equivalent variations made by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications, and variations made to the above embodiments based on the essential technology of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A deep well polysulfonate drilling fluid, characterized in that, Comprising raw materials in the following parts by weight: Deionized water: 100 parts, bentonite: 3 - 5 parts, modified filtration loss reducer: 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 filtration loss reducer is prepared by the following method: S1: Under nitrogen protection, 2,2 - dimethylolpropionic acid and 2 - hydroxypropyl methacrylate react to form a hyperbranched product under the catalysis of p - toluenesulfonic acid; S2: Corn starch is acidified under the action of dilute hydrochloric acid to obtain acid - hydrolyzed starch, and the acid - hydrolyzed starch reacts with chlorophenyltriethoxysilane to obtain silane - modified acid - hydrolyzed starch; S3: The silane - modified acid - hydrolyzed starch and the hyperbranched product react under the action of sodium hydroxide to form a silylated hyperbranched product; S4: Acrylamide, sodium p - styrenesulfonate, allyloxy polyoxyethylene ether, and the silylated hyperbranched product react under the action of ammonium persulfate to form a modified filtration loss reducer; In step S1, the feeding mass ratio of 2,2 - dimethylolpropionic acid to 2 - hydroxypropyl methacrylate is 5:(25 - 30); In step S2, the feeding mass ratio of the acid - hydrolyzed starch to chlorophenyltriethoxysilane is (12 - 16):10; In step S3, the feeding mass ratio of the silane - modified acid - hydrolyzed starch to the hyperbranched product is 20:(3 - 5); In step S4, the feeding mass ratio of acrylamide, sodium p - styrenesulfonate, allyloxy polyoxyethylene ether, and the silylated hyperbranched product is (30 - 40):(20 - 25):(2 - 5):2; The modified emulsifier is prepared by the following method: A1: 3 - aminopropyltriethoxysilane is hydrolyzed to form 3 - aminopropylsilanetriol, and then it is modified with nano - silica to obtain modified nano - silica; A2: The modified nano - silica reacts with stearic acid and octanoic acid to obtain a modified emulsifier; In step A1, the feeding mass ratio of 3 - aminopropyltriethoxysilane to nano - silica is (0.5 - 2):10; In step A2, the feeding mass ratio of the modified nano - silica, stearic acid, and octanoic acid is 20:(6 - 10):(3 - 5).

2. The polysulfonate drilling fluid for deep wells according to claim 1, wherein, The pH regulator is a combination of one or more of potassium carbonate, potassium hydroxide, and sodium hydroxide; the lubricant is white mineral oil; the plugging agent is sulfonated asphalt.

3. The preparation method of the deep well polysulfonate drilling fluid according to any one of claims 1-2, characterized in that, Including the following steps: (1) Weigh according to parts by weight: deionized water: 100 parts, bentonite: 3 - 5 parts, modified filtration loss reducer: 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; (2) Add deionized water into the container, and add bentonite while stirring. After stirring for 15 - 25 min, stop stirring and carry out airtight curing for 24 h to obtain pre - hydrated bentonite slurry; successively add a pH regulator, a modified fluid loss reducer, a modified emulsifier, a plugging agent, and a lubricant into the pre - hydrated bentonite slurry in the above - mentioned proportions, stir at high speed for 50 - 70 min, and finally add barite powder and stir evenly to obtain a deep - well polysulfonate drilling fluid.

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