Desulfonated multifunctional humic acid-based drilling fluid filtrate reducer and preparation method thereof

Abstract

This invention relates to the field of oilfield chemical technology, specifically a desulfonated multifunctional humic acid-based drilling fluid filtration reducer and its preparation method. The method includes: mixing lignite, caustic soda, and water and reacting them to obtain a lignite-alkali solution; adding a calcium ion slow-release agent, subjecting the reaction to light irradiation, stirring and allowing it to stand after reaction, separating the reaction product into a solid phase and a liquid phase; adding acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, and dimethyldiallylammonium chloride monomer to the liquid phase product and performing a polymerization reaction to obtain a humic acid-modified polymer; adding the solid phase product to the humic acid-modified polymer and mixing to obtain the humic acid-based filtration reducer. This invention combines the synergistic effect of nanomaterials and multifunctional modified polymers, achieving high-temperature resistance and salt resistance above 180℃ without the need for sulfonation agents; the product is free of sulfonate groups, formaldehyde, and heavy metals, is bio-non-toxic, biodegradable, and non-corrosive, meeting the green drilling requirements of deep and ultra-deep wells.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to a desulfonated multifunctional humic acid-based drilling fluid filtration reducer and its preparation method. Background Technology

[0002] During drilling, due to pressure differentials, water in the drilling fluid inevitably leaks through the wellbore into the formation, causing fluid loss. As water enters the formation, clay particles in the drilling fluid adhere to the wellbore, forming a "filter cake," or filter cake wellbore. Because the filter cake wellbore is much denser than the original wellbore, it both prevents further fluid loss and protects the wellbore. However, excessive fluid loss, an overly thick filter cake, and fine clay particles entering the formation with the water during filter cake formation can all affect normal drilling and damage the formation. Therefore, appropriately controlling fluid loss is one of the important performance characteristics of drilling fluid.

[0003] CN102433107A discloses a low molecular weight polymer-type filtration loss reducer and its preparation method. The filtration loss reducer of this invention is obtained by copolymerization of acrylamide, 2-acrylamidododecanesulfonate, and alkenylsulfonate; the relative molecular mass of the copolymer is 100,000 to 300,000, and the molar ratio of acrylamide, 2-acrylamidododecanesulfonate, and alkenylsulfonate components in the copolymer is (10-50):1:(5-60). However, this polymer's molecular chains are prone to breakage above 150°C, resulting in a significant decrease in filtration loss reduction efficiency, making it unsuitable for high-temperature conditions in ultra-deep wells.

[0004] CN119613980A discloses a high-temperature, high-pressure filtration loss reducer for drilling fluids, sulfonated asphalt, and its preparation method. A comb-like side chain is introduced into the SEBS benzene ring, giving it a comb-like structure. This structure strongly interacts with the sulfonated asphalt, optimizing asphalt dispersion and preventing agglomeration. The introduction of 5-(2-hydroxyethyl)uracil balances the lipophilic and hydrophilic properties, reduces the interparticle forces in asphalt, and improves the reaction efficiency and uniformity of asphalt with fuming sulfuric acid. As a dispersant, it promotes uniform asphalt dispersion, accelerates the sulfonation reaction, and improves the quality of the sulfonated asphalt. However, using fuming sulfuric acid as the sulfonating agent, the product contains residual sulfate and polycyclic aromatic hydrocarbons, exhibiting strong corrosiveness to drilling tools and moderate biotoxicity, posing certain environmental safety risks.

[0005] In summary, existing drilling fluid filtration reduction agents have two major drawbacks: First, conventional polymer-based small molecule filtration reduction agents can withstand temperatures up to 120°C to 150°C, but this is still insufficient to meet the requirements for high-temperature resistance; second, sulfonated agents that are resistant to salt and 180°C are not only highly corrosive, but also still fall short of the requirements for green drilling. Summary of the Invention

[0006] This invention provides a desulfonated multifunctional humic acid-based drilling fluid filtration reducer, which overcomes the shortcomings of the prior art and can effectively solve the problems of insufficient temperature resistance, strong corrosiveness, and high biological toxicity of existing drilling fluid filtration reducers.

[0007] One of the technical solutions of this invention is achieved through the following measures: a method for preparing a desulfonated multifunctional humic acid-based drilling fluid filtration reducer, comprising the following steps: Step 1: Mix the required amount of lignite, caustic soda, and water, then heat and react to obtain lignite alkali solution; Step 2: Add calcium ion slow-release agent to lignite alkali solution, irradiate with light to react, stir and let stand after reaction, and separate the reaction product into solid and liquid phases to obtain solid phase product (containing nanomaterials and calcium humate colloidal precipitate) and liquid phase product. Step 3: Add acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer and dimethyl diallyl ammonium chloride monomer to the liquid phase product, add initiator and chain transfer agent, and carry out polymerization reaction to obtain humic acid modified polymer. Step four: Add solid products to the humic acid modified polymer, and after mixing, obtain humic acid-based filtration loss reducer.

[0008] The following are further optimizations and / or improvements to the above-mentioned technical solution: The mass ratio of the above-mentioned lignite, caustic soda and water is 15:(1 to 3):100.

[0009] The aforementioned calcium ion slow-release agent uses polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles as the calcium source and CNF / TiO2@ZIF-8 as the carrier; the mass ratio of calcium ion slow-release agent to lignite is (0.8 to 1.2):5. In CNF / TiO2@ZIF-8, CNF is an abbreviation for cellulose nanofiber, and ZIF-8 is an abbreviation for zeolite imidazole ester framework-8, which is a metal-organic framework (MOF) material formed by the self-assembly of zinc ions and 2-methylimidazolium ligands.

[0010] The mass ratio of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, dimethyl diallyl ammonium chloride monomer, and lignite is (15 to 25):(20 to 30):(5 to 10):(3 to 6):100. Optimally, the mass ratio of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, dimethyl diallyl ammonium chloride monomer, and lignite is 20:25:8:5:100.

[0011] The initiator mentioned above is ammonium persulfate, azobisisobutyronitrile, or azobisisoheptanenitrile, and the amount of initiator added is 3% to 5% of the total mass of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, and dimethyl diallyl ammonium chloride monomer. Optimally, the initiator is ammonium persulfate.

[0012] The chain transfer agent mentioned above is isopropanol or tert-dodecyl mercaptan, added in an amount of 0.8% to 1.2% of the total mass of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer and dimethyl diallyl ammonium chloride monomer. Optimally, isopropanol is used as the chain transfer agent.

[0013] In step one above, the reaction temperature is 80℃ to 90℃ and the reaction time is 1.5 to 3 hours.

[0014] In step two above, the light wavelength for the photoreaction is ultraviolet light, and the light exposure time is 1 to 2 hours.

[0015] In step two above, stirring and settling involves stirring for 1.5 to 2.5 hours and then settling for 40 to 70 minutes.

[0016] In step three above, the polymerization reaction is carried out under weakly acidic conditions. The specific steps are as follows: adjust the liquid phase product to weakly acidic (pH 5.5 to 7.0), raise the temperature to 55°C to 65°C, stir at a constant temperature, add acrylic monomer and initiator and stir evenly, then slowly add a mixture of acrylamide monomer and N-vinylpyrrolidone monomer, with an addition time of 20 min to 25 min, then add dimethyl diallyl ammonium chloride monomer and chain transfer agent, stir evenly and continue to keep the reaction at the temperature for 1.5 h to 2.5 h to obtain humic acid modified polymer.

[0017] In step four above, the stirring temperature is 30℃ to 45℃.

[0018] The second technical solution of the present invention is achieved through the following measures: a desulfonated multifunctional humic acid-based drilling fluid filtration reducer prepared by a method of preparing a desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to one of the technical solutions.

[0019] This invention provides a process for preparing a desulfonated multifunctional humic acid-based drilling fluid filtration reducer: using natural lignite as raw material, calcium humate colloidal precipitate is generated controllably through calcium ion slow-release technology. Combined with the synergistic effect of nanomaterials and multifunctional modified polymers, it can achieve high temperature resistance and salt resistance above 180℃ without sulfonating agents. The product is free of sulfonic acid groups, formaldehyde and heavy metals, is biologically non-toxic, biodegradable and non-corrosive, meeting the green drilling requirements of deep and ultra-deep wells. Detailed Implementation

[0020] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0021] The present invention will be further described below with reference to embodiments: Example 1: A method for preparing a desulfonated multifunctional humic acid-based drilling fluid filtration reducer, comprising the following steps: Step 1: Mix the required amount of lignite, caustic soda, and water, then heat and react to obtain lignite alkali solution; Step 2: Add calcium ion slow-release agent to lignite alkali solution, irradiate with light to react, stir and let stand after reaction, and separate the reaction product into solid and liquid phases to obtain solid phase product (containing nanomaterials and calcium humate colloidal precipitate) and liquid phase product. Step 3: Add acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer and dimethyl diallyl ammonium chloride monomer to the liquid phase product, add initiator and chain transfer agent, and carry out polymerization reaction to obtain humic acid modified polymer. Step four: Add solid products to the humic acid modified polymer, and after mixing, obtain humic acid-based filtration loss reducer.

[0022] Example 2: As an optimization of the above example, the mass ratio of lignite, caustic soda and water is 15:(1 to 3):100.

[0023] Example 3: As an optimization of the above examples, the calcium ion slow-release agent uses polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles as the calcium source and CNF / TiO2@ZIF-8 as the carrier; the mass ratio of calcium ion slow-release agent to lignite is (0.8 to 1.2):5.

[0024] The calcium ion slow-release agent of this invention uses a nanomaterial as a carrier, wherein calcium ions are released through photocatalysis under alkaline conditions. The specific preparation process is as follows: polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles and CNF / TiO2@ZIF-8 are added to a 5% (w / w) tetrahydrofuran aqueous solution. After stirring thoroughly at room temperature for 3 to 4 hours, the mixture is filtered and dried to obtain the calcium ion slow-release agent. Optimally, the mass ratio of the PLA / nano-calcium carbonate composite nanoparticles to CNF / TiO2@ZIF-8 is 1:3.

[0025] Example 4: As an optimization of the above example, the mass ratio of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, dimethyl diallyl ammonium chloride monomer, and lignite is (15 to 25):(20 to 30):(5 to 10):(3 to 6):100. Optimally, the mass ratio of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, dimethyl diallyl ammonium chloride monomer, and lignite is 20:25:8:5:100.

[0026] Example 5: As an optimization of the above examples, the initiator is ammonium persulfate, azobisisobutyronitrile, or azobisisoheptanenitrile, and the amount of initiator added is 3% to 5% of the total mass of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, and dimethyl diallyl ammonium chloride monomer. Optimally, the initiator is ammonium persulfate.

[0027] Example 6: As an optimization of the above examples, the chain transfer agent is isopropanol or tert-dodecyl mercaptan, and the amount added is 0.8% to 1.2% of the total mass of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer and dimethyl diallyl ammonium chloride monomer. Optimally, the chain transfer agent is isopropanol.

[0028] Example 7: As an optimization of the above example, in step one, the reaction temperature is 80°C to 90°C and the reaction time is 1.5 to 3 hours.

[0029] Example 8: As an optimization of the above example, in step two, the light band of the photoreaction is ultraviolet light, and the light duration is 1 to 2 hours.

[0030] Example 9: As an optimization of the above example, in step two, the stirring and settling is carried out for 1.5h to 2.5h and then settling for 40min to 70min.

[0031] Example 10: As an optimization of the above example, in step three, the polymerization reaction is carried out under weak acid conditions. The specific steps are as follows: adjust the liquid phase product to weak acidity, raise the temperature to 55°C to 65°C, stir at a constant temperature, add acrylic monomer and initiator and stir evenly, then slowly add a mixture of acrylamide monomer and N-vinylpyrrolidone monomer, the feeding time is 20 min to 25 min, then add dimethyl diallyl ammonium chloride monomer and chain transfer agent, stir evenly and continue to keep the reaction at a constant temperature for 1.5 h to 2.5 h to obtain humic acid modified polymer.

[0032] Example 11: As an optimization of the above example, in step four, the stirring temperature is 30°C to 45°C.

[0033] Humic acid, as a natural organic material, contains active groups such as carboxyl and phenolic hydroxyl groups in its molecules, possessing good temperature resistance (180℃) and environmentally friendly properties. Humic acid is mainly derived from lignite; therefore, this invention primarily uses lignite as the main raw material to prepare lignite alkali solution. Based on this lignite alkali solution, the high-temperature resistance of humic acid is utilized to replace sulfonating agents as a high-temperature treatment agent. When drilling fluid prepared with lignite alkali solution encounters significant calcium intrusion, sodium humate reacts with calcium ions to form insoluble calcium humate precipitate, rendering the fluid ineffective. However, if an appropriate amount of calcium ions is added to the drilling fluid treated with lignite alkali solution, a small amount of colloidal calcium humate precipitate is generated, making the mud cake thinner and tougher, and correspondingly reducing filtration loss. Therefore, this invention adds a calcium ion slow-release agent to the lignite alkali solution to control the formation of the colloidal calcium humate precipitate, preventing the failure of the filtration loss reduction effect due to excessive calcium humate precipitation.

[0034] This invention utilizes the colloidal precipitation of calcium humate to enhance the filtration loss reduction performance of humic acid. It also utilizes the nanomaterials remaining after the slow release of calcium ions as a sludge cake filler and a humic acid-modified polymer (introduction of multifunctional groups). While improving filtration loss reduction performance and ensuring stable dispersion of the entire system, it also has good salt and high temperature resistance. It can replace existing sulfonation treatment agents to achieve desulfonation filtration loss reduction treatment.

[0035] Example 12: The preparation process of this desulfonated multifunctional humic acid-based drilling fluid filtration reducer is as follows: (1) Preparation of lignite alkali solution: Take 60g of lignite, mix lignite, caustic soda and water in a mass ratio of 15:2:100, heat to 90℃ and react for 2 hours to obtain lignite alkali solution.

[0036] (2) Preparation of calcium ion sustained-release agent: Polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles and CNF / TiO2@ZIF-8 were added to a 5% tetrahydrofuran aqueous solution. After stirring thoroughly at room temperature for 4 hours, the mixture was filtered and dried to obtain the calcium ion sustained-release agent. The mass ratio of polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles to CNF / TiO2@ZIF-8 was 1:3.

[0037] (3) Preparation of solid and liquid products: Calcium ion slow release agent was added to lignite alkali solution. The mass ratio of calcium ion slow release agent to lignite was 1:5. After stirring evenly at room temperature, the reaction was carried out by ultraviolet light at a distance of 13 cm. After 1.5 hours of light reaction, the light was stopped. After stirring for another 2 hours, the mixture was allowed to stand for 1 hour. Then, solid-liquid separation was carried out to obtain solid and liquid products. The solid product was a colloidal precipitate containing nanomaterials and calcium humate. The nanomaterials were polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles-CNF / TiO2@ZIF-8 composite nanomaterials.

[0038] (4) Preparation of humic acid modified polymer: Dilute nitric acid was added to the liquid product to lower the pH value to 6.5 and then the temperature was raised to 60°C. After stirring at a constant temperature for 30 minutes, acrylic acid monomer and initiator were added. After stirring evenly, a mixture of acrylamide monomer and N-vinylpyrrolidone monomer was slowly added over a period of 25 minutes. Then, dimethyl diallyl ammonium chloride monomer and chain transfer agent were added. After stirring evenly, the reaction was continued at a constant temperature for 2 hours to obtain humic acid modified polymer. The initiator was ammonium persulfate, and the amount of initiator added was 4% of the total monomer mass. The chain transfer agent was isopropanol, and the amount added was 1.0% of the total monomer mass. The mass ratio of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, dimethyl diallyl ammonium chloride monomer and lignite was 15:20:5:3:100.

[0039] (5) At 40°C, the solid phase separated in step (3) is added to the humic acid modified polymer and stirred evenly to obtain the desulfonated multifunctional humic acid-based drilling fluid filtration reducer, denoted as S1.

[0040] Example 13: The difference from Example 12 is that the mass ratio of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, dimethyl diallyl ammonium chloride monomer, and lignite is 20:25:8:5:100; the resulting desulfonated multifunctional humic acid-based drilling fluid filtration reducer is denoted as S2.

[0041] Example 14: The difference from Example 12 is that the mass ratio of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, dimethyl diallyl ammonium chloride monomer, and lignite is 25:30:10:6:100; the resulting desulfonated multifunctional humic acid-based drilling fluid filtration reducer is designated as S3.

[0042] Example 15: The difference from Example 13 is that the mass ratio of lignite, caustic soda, and water is 15:1:100; the resulting desulfonated multifunctional humic acid-based drilling fluid filtration reducer is designated as S4.

[0043] Example 16: The difference from Example 13 is that the mass ratio of lignite, caustic soda, and water is 15:3:100; the resulting desulfonated multifunctional humic acid-based drilling fluid filtration reducer is designated as S5.

[0044] Comparative Example 1: The difference from Example 13 is that: no calcium ion slow-release agent is added (i.e. steps (2) and (3) of Example 2 are not performed), dilute nitric acid is directly added to lignite alkali solution to adjust the pH, and then each monomer and initiator chain transfer agent are added to carry out the polymerization reaction. The humic acid modified polymer obtained is used as the filtration loss reducer and is denoted as D1.

[0045] Comparative Example 2: The difference from Example 13 is that the humic acid-based filtration reducer prepared in this comparative example does not contain calcium humate colloidal precipitate, and is prepared by the following method: (1) Taking 60g of lignite as an example, lignite, caustic soda and water in a mass ratio of 15:2:100 are used as raw materials and heated to 90℃ for 2 hours to obtain lignite alkali solution; (2) Preparation of calcium ion sustained-release agent with nanomaterial as carrier, wherein the calcium ion sustained-release agent uses polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles as calcium source and CNF / TiO2@ZIF-8 as carrier, and is prepared by the following method: polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles and CNF / TiO2@ZIF-8 are added to a 5% (w / w) tetrahydrofuran aqueous solution, stirred thoroughly at room temperature for 4 hours, filtered and dried to obtain calcium ion sustained-release agent; wherein the mass ratio of polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles to CNF / TiO2@ZIF-8 is 1:3; (3) Dilute nitric acid is added to the lignite alkali solution. After the pH value drops to 6.5, the temperature is raised to 60°C and stirred for 30 minutes. Then, acrylic acid monomer and initiator are added and stirred evenly. Then, a mixture of acrylamide monomer and N-vinylpyrrolidone monomer is slowly added over a period of 25 minutes. Then, dimethyl diallyl ammonium chloride monomer and chain transfer agent are added and stirred evenly. The reaction is continued for 2 hours to obtain humic acid modified polymer. The initiator is preferably ammonium persulfate, and the amount of initiator added is 4% of the total monomer mass. The chain transfer agent is preferably isopropanol, and the amount added is 1.0% of the total monomer mass. (4) At 40°C, the calcium ion slow-release agent in step (2) is directly added to the humic acid modified polymer. The mass ratio of the calcium ion slow-release agent to lignite is 1:5. After stirring evenly, the filtration loss reducer is obtained and is denoted as D2.

[0046] Comparative Example 3: The difference from Example 13 is that the humic acid-based filtration reducer prepared in this comparative example does not contain nanomaterials. It is prepared by the following method: (1) Taking 60g of lignite as an example, lignite, caustic soda and water in a mass ratio of 15:2:100 are used as raw materials and heated to 90℃ for 2 hours to obtain lignite alkali solution; (2) Preparation of calcium ion sustained-release agent with nanomaterial as carrier, wherein the calcium ion sustained-release agent uses polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles as calcium source and CNF / TiO2@ZIF-8 as carrier, and is prepared by the following method: polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles and CNF / TiO2@ZIF-8 are added to a 5% (w / w) tetrahydrofuran aqueous solution, stirred thoroughly at room temperature for 4 hours, filtered and dried to obtain calcium ion sustained-release agent; wherein the mass ratio of polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles to CNF / TiO2@ZIF-8 is 1:3; (3) Add calcium ion slow-release agent to lignite alkali solution. The mass ratio of calcium ion slow-release agent to lignite is 1:5. After stirring evenly at room temperature, use ultraviolet lamp for photoreaction. The irradiation distance is 13cm. After 1.5 hours of photoreaction, stop the photoreaction. Continue stirring for 2 hours and let stand for 1 hour. Then perform solid-liquid separation to obtain solid phase and liquid phase. The solid phase contains nanomaterials and calcium humate colloidal precipitate. Remove the nanomaterials in the solid phase (the particle size is different, and the calcium humate colloidal precipitate and nanomaterials are different in macroscopic size and particle size). Retain the calcium humate colloidal precipitate. The solid phase is calcium humate colloidal precipitate. (4) Dilute nitric acid is added to the liquid phase. After the pH value drops to 6.5, the temperature is raised to 60°C and stirred for 30 minutes. Then, acrylic acid monomer and initiator are added and stirred evenly. Then, a mixture of acrylamide monomer and N-vinylpyrrolidone monomer is slowly added over a period of 25 minutes. Then, dimethyl diallyl ammonium chloride monomer and chain transfer agent are added and stirred evenly. The reaction is continued for 2 hours to obtain humic acid modified polymer. The initiator is preferably ammonium persulfate, and the amount of initiator added is 4% of the total monomer mass. The chain transfer agent is preferably isopropanol, and the amount added is 1.0% of the total monomer mass. (5) At 40°C, the solid phase separated in step (3) is added to the humic acid modified polymer and stirred evenly to obtain the filtration loss reducer, denoted as D3.

[0047] Comparative Example 4: The difference from Example 13 is that steps (4) and (5) are omitted, and the humic acid-based filtration reducer obtained from the calcium ion slow-release agent and lignite alkali solution in step (3) does not contain polymers. It is prepared by the following method: (1) Taking 60g of lignite as an example, lignite, caustic soda and water in a mass ratio of 15:2:100 are used as raw materials and heated to 90℃ for 2 hours to obtain lignite alkali solution; (2) Preparation of calcium ion sustained-release agent with nanomaterial as carrier, wherein the calcium ion sustained-release agent uses polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles as calcium source and CNF / TiO2@ZIF-8 as carrier, and is prepared by the following method: polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles and CNF / TiO2@ZIF-8 are added to a 5% (w / w) tetrahydrofuran aqueous solution, stirred thoroughly at room temperature for 4 hours, filtered and dried to obtain calcium ion sustained-release agent; wherein the mass ratio of polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles to CNF / TiO2@ZIF-8 is 1:3; (3) Add calcium ion slow-release agent to lignite alkali solution. The mass ratio of calcium ion slow-release agent to lignite is 1:5. After stirring evenly at room temperature, use ultraviolet lamp for photoreaction. The irradiation distance is 13cm. After 1.5 hours of photoreaction, stop the photoreaction. Continue stirring for 2 hours and let stand for 1 hour to obtain the filtration loss reducer, which is denoted as D4.

[0048] Comparative Example 5: The difference from Example 13 is that the humic acid modified polymer does not contain acrylic acid monomers, and the resulting filtration loss reducer is denoted as D5.

[0049] Comparative Example 6: The difference from Example 13 is that the humic acid modified polymer does not contain acrylamide monomer, and the resulting filtration loss reducer is denoted as D6.

[0050] Comparative Example 7: The difference from Example 13 is that the humic acid modified polymer does not include N-vinylpyrrolidone monomer, and the resulting filtration loss reducer is denoted as D7.

[0051] Comparative Example 8: The difference from Example 13 is that the humic acid modified polymer does not contain dimethyl diallyl ammonium chloride monomer, and the resulting filtration loss reducer is denoted as D8.

[0052] Comparative Example 9: The difference from Example 13 is that no chain transfer agent is added during the preparation of the humic acid modified polymer, and the resulting filtration loss reducer is denoted as D9.

[0053] Blank Group 1: Take 60g of lignite, mix lignite, caustic soda and water in a mass ratio of 15:2:100, heat to 90℃ and react for 2 hours to obtain lignite alkali solution, denoted as K1.

[0054] Test Example 1: The rheological properties and water loss wall-building performance of the above-mentioned filtration loss reducing agents S1 to S5, D1 to D9 and K1 were tested.

[0055] The drilling fluid was prepared with the following formula: 100 parts by weight of water + 3 parts by weight of bentonite + 0.2 parts by weight of anhydrous sodium carbonate + 0.02 parts by weight of coating agent (FA367) + 6 parts by weight of filtration loss reducer to be tested + 4 parts by weight of anti-collapse agent (polyol stearic acid copolymer BZ-YFT) + 4 parts by weight of anti-sticking lubricant (vegetable oil liquid lubricant HY-202) + 0.4 parts by weight of sodium chloride + 1 part by weight of shielding and temporary plugging agent (nano silica NS-1).

[0056] Preparation method: Add bentonite to water at 70℃, stir evenly at room temperature, add anhydrous NaCO3, stir thoroughly for 30 minutes, seal and let stand for 24 hours to hydrate, and obtain prehydrated bentonite slurry; add coating agent, filtration loss reducer, anti-collapse agent, anti-sticking lubricant, sodium chloride, and shielding temporary plugging agent to the prehydrated bentonite slurry in sequence, stirring for 20 minutes after each addition; after stirring evenly, drilling fluid is obtained.

[0057] Drilling fluids were prepared using filtration loss reducers S1 to S5, D1 to D9, and K1 according to the above proportions and methods. Two blank groups were also prepared: blank group 2 (K2) used sulfonated phenolic resin as the filtration loss reducer, and the corresponding drilling fluid was prepared according to the above proportions and methods; blank group 3 (K3) was a drilling fluid prepared according to the above formula and method without the addition of 6 parts by weight of the filtration loss reducer.

[0058] According to standard GB / T 16783.1-2014 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids", the filtration loss of drilling fluids corresponding to the above-mentioned filtration loss reducers was tested after aging. The results are shown in Table 1 (in Table 1, API is the filtration loss at room temperature and medium pressure, and the test conditions are room temperature, 690 kPa pressure difference, 30 minutes, and the unit is mL).

[0059] Table 1 .

[0060] The test results show that the desulfonated multifunctional humic acid-based drilling fluid filtration reducer of the present invention has a significant filtration reduction effect on drilling fluid, and can achieve the same or even better effect as the sulfonation additive; in addition, the mud cake thickness of the present invention is about 2 mm, and the mud cake is thin and dense.

[0061] Test Example 2: The HTHP (180℃, 3.5MPa) of the desulfonated multifunctional humic acid-based drilling fluid filtration reducers S1 to S5 before drilling fluid aging was tested, and the results are shown in Table 2.

[0062] Table 2 .

[0063] This invention provides a desulfonated multifunctional humic acid-based drilling fluid filtration reducer and its preparation method. Utilizing calcium ion slow-release technology, the filtration reduction performance of humic acid is effectively improved by introducing a controllable amount of calcium humate colloidal precipitate. While ensuring excellent filtration reduction performance, the synergistic effect of nanomaterials and multi-functional humic acid-modified polymers is utilized, giving the desulfonated multifunctional humic acid-based drilling fluid filtration reducer good high-temperature and salt resistance, enabling it to replace sulfonation treatment agents. Furthermore, this invention uses a CNF / TiO2@ZIF-8 composite carrier, which not only supports the calcium source but also possesses good stability and high-temperature resistance. Using polylactic acid (PLA) / nano-calcium carbonate composite nanoparticles as the calcium source, the slow release of calcium ions is achieved by utilizing the hydrogen ion enrichment generated from the hydrolysis of PLA under alkaline solution and light irradiation, making it environmentally friendly and safe.

[0064] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method for preparing desulfonated multifunctional humic acid based filtrate reducer for drilling fluids, characterized by Includes the following steps: Step 1: Mix the required amount of lignite, caustic soda, and water, then heat and react to obtain lignite alkali solution; Step 2: Add calcium ion slow-release agent to lignite alkali solution, irradiate with light to react, stir and let stand after reaction, and separate the reaction product into solid and liquid phase products to obtain solid phase product and liquid phase product. Step 3: Add acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer and dimethyl diallyl ammonium chloride monomer to the liquid phase product, add initiator and chain transfer agent, and carry out polymerization reaction to obtain humic acid modified polymer. Step four: Add solid products to the humic acid modified polymer, and after mixing, obtain humic acid-based filtration loss reducer.

2. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1, characterized in that... The mass ratio of lignite, caustic soda, and water is 15:(1 to 3):

100.

3. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1 or 2, characterized in that... The calcium ion slow-release agent uses polylactic acid / nano-calcium carbonate composite nanoparticles as the calcium source and CNF / TiO2@ZIF-8 as the carrier; the mass ratio of calcium ion slow-release agent to lignite is (0.8 to 1.2):

5.

4. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1 or 2, characterized in that... The mass ratio of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, dimethyl diallyl ammonium chloride monomer, and lignite is (15 to 25): (20 to 30): (5 to 10): (3 to 6):

100.

5. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1 or 2, characterized in that... The initiator is ammonium persulfate, azobisisobutyronitrile, or azobisisoheptanenitrile, and the amount of initiator added is 3% to 5% of the total mass of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer, and dimethyl diallyl ammonium chloride monomer.

6. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1 or 2, characterized in that... The chain transfer agent is isopropanol or tert-dodecyl mercaptan, and the amount added is 0.8% to 1.2% of the total mass of acrylic acid monomer, acrylamide monomer, N-vinylpyrrolidone monomer and dimethyl diallyl ammonium chloride monomer.

7. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1, characterized in that... In step one, the reaction temperature is 80℃ to 90℃ and the reaction time is 1.5 to 3 hours.

8. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1 or 7, characterized in that... In step two, the light wavelength for the photoreaction is ultraviolet light, and the light exposure time is 1 to 2 hours.

9. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1 or 7, characterized in that... In step two, the stirring and settling process involves stirring for 1.5 to 2.5 hours and then letting it stand for 40 to 70 minutes.

10. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1 or 7, characterized in that... In step three, the polymerization reaction is carried out under weakly acidic conditions. The specific steps are as follows: adjust the liquid phase product to weakly acidic, raise the temperature to 55℃ to 65℃, stir at a constant temperature, add acrylic monomer and initiator and stir evenly, then slowly add a mixture of acrylamide monomer and N-vinylpyrrolidone monomer, the feeding time is 20 min to 25 min, then add dimethyl diallyl ammonium chloride monomer and chain transfer agent, stir evenly and continue to keep the reaction at the temperature for 1.5 h to 2.5 h to obtain humic acid modified polymer.

11. The preparation method of the desulfonated multifunctional humic acid-based drilling fluid filtration reducer according to claim 1 or 7, characterized in that... In step four, the stirring temperature is 30°C to 45°C.

12. A desulfonated multifunctional humic acid-based drilling fluid filtration reducer prepared by a method according to any one of claims 1 to 11.