Zwitterionic polymer filtrate reducer and preparation method thereof

Abstract

The invention relates to the technical field of oil-gas field development, in particular to a zwitterionic polymer filtrate reducer and a preparation method thereof.The zwitterionic polymer filtrate reducer is prepared from an acrylamide monomer, a hydrophilic monomer, a rigid monomer, a salt-tolerant monomer, a copolymerization adjusting monomer, starch, aluminum oxide powder, KH560 modified nano-silica, a cationic monomer and an anionic monomer; mixing an acrylamide monomer, a hydrophilic monomer, a rigid monomer, a salt-tolerant monomer, a copolymerization adjusting monomer, a cationic monomer, an anionic monomer and a solvent to obtain a monomer mixed solution; introducing nitrogen to remove oxygen; adding an initiator, heating and carrying out copolymerization reaction; adding starch and continuously stirring to obtain a material flow A; uniformly mixing KH560 modified nano silicon dioxide and aluminum oxide powder, and adding the mixture into the material flow A; and drying, crushing and grinding to obtain zwitterionic polymer filtrate reducer powder. When in contact with a well wall, the filtrate reducer can be spread and adhered to the surface of the well wall to form a low-permeability, flexible, thin and compact filter cake, so that the filter loss of a drilling fluid is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a zwitterionic polymer fluid loss reducer and a preparation method thereof. Background Art

[0002] With the continuous increase in global energy demand and the depletion of conventional oil and gas resources, the target layers for oil and gas resource exploration and development have gradually expanded from medium and shallow layers to deep and ultra-deep layers. Deep layers will be one of the most important development areas for the oil industry in the future. In the deep drilling process, there are generally complex geological conditions with high temperature, high pressure and high mineralization.

[0003] Drilling fluid is the working fluid in the drilling process. Appropriately low filtration loss is one of the important properties of drilling fluid. Drilling fluid filtration reducer is a very important drilling fluid treatment agent. If the drilling fluid filtration loss is too large during the drilling process, it will cause a series of problems. For example, the hydration expansion and collapse of shale will cause the instability of the well wall; the drilling fluid will invade the formation, causing clay to expand, thereby blocking the formation oil and gas flow channels and damaging the production layer, which will seriously affect the normal progress of drilling work.

[0004] Patent document CN104098746 A discloses a hydrophobically associated zwitterionic starch containing adamantyl and a preparation method thereof, wherein the zwitterionic starch is prepared from starch, adamantyl hydrophobic monomer, alkenyl amide, alkenyl carboxylate and alkenyl quaternary ammonium salt as raw materials. The invention introduces adamantyl hydrophobic units into polymer molecules, so that the modified starch has hydrophobic associative properties and improves the viscosity-increasing ability of the modified starch. The introduction of anionic groups and cationic groups into the starch molecular chain at the same time enhances the anti-polyelectrolyte effect of the solution and improves the salt resistance. The present invention improves the salt resistance of the modified starch, but does not evaluate its temperature resistance.

[0005] CN103396515A discloses a high temperature resistant modified starch fluid loss reducer and a preparation method thereof, wherein the modified starch fluid loss reducer is a starch graft copolymer generated by reacting starch, phenolic compounds, alkenyl amides and alkenyl sulfonic acids as raw materials, an oil phase solution as a continuous phase, and a nonionic surfactant as an emulsifier under the catalytic action of a reducing substrate and a hydrogen acceptor substrate. The fluid loss reducer provided by the invention can withstand temperatures up to 175°C and has good salt resistance, but the preparation cost of the reverse emulsion method is relatively high.

[0006] Since the filtration performance of drilling fluid in extreme high-temperature and salty environments is crucial to the success of deep and ultra-deep well drilling, high-temperature and salt-resistant base drilling fluid filtration reducers have always been the focus of research on deep and ultra-deep well drilling fluids at home and abroad. It is of great significance to develop temperature-resistant and salt-resistant drilling fluid filtration reducers. In addition, the functions of existing filtration reducers are relatively single, and inhibitors (anti-collapse) agents are often added at the same time during on-site construction, which increases the cost of drilling fluids. Summary of the invention

[0007] The invention aims to solve the problem in the prior art that the drilling fluid loss reducer has poor temperature and salt resistance.

[0008] The invention provides a zwitterionic polymer fluid loss reducer, which comprises, by mass, 100 parts of acrylamide monomer, 20-30 parts of hydrophilic monomer, 10-20 parts of rigid monomer, 30-50 parts of salt-tolerant monomer, 10-20 parts of copolymerization regulating monomer, 30-50 parts of starch, 3-5 parts of alumina powder, 5-10 parts of KH560 modified nano silicon dioxide, 5-10 parts of cationic monomer and 5-10 parts of anionic monomer; The cationic monomer is one or more of acryloyloxyethyl trimethyl ammonium chloride and allyl trimethyl ammonium chloride.

[0009] The salt-tolerant monomer is one or more of N-phenylacrylamide, dimethylaminopropylacrylamide and N-hydroxymethylacrylamide.

[0010] The copolymerization regulating monomer is one or more of methyl methacrylate, ethyl methacrylate, isopropyl methacrylate and hydroxyethyl methacrylate.

[0011] The rigid monomer is a vinyl monomer having a cyclic group on the side chain, and more preferably one or more of styrene, α-methylstyrene, isobornyl acrylate, isobornyl methacrylate, 1-adamantyl acrylate, 1-adamantyl methacrylate, methacrylate (2-methyl-2-adamantyl ester), and 2-ethyl-2-adamantyl methacrylate.

[0012] The hydrophilic monomer is polyethylene glycol methyl ether methacrylate.

[0013] The starch is one or more of corn starch, cassava starch, sweet potato starch and potato starch.

[0014] The particle size of KH560 modified nano-silica ranges from 100nm to 500nm, and the particle size of alumina ranges from 1-20um.

[0015] The preparation method of zwitterionic polymer fluid loss reducer is as follows: S1. Preparation of KH560 modified nano-silica: Disperse nano-silica in ethanol, add KH560 dispersion, mix evenly, and react at 70°C for 3 hours; after the reaction is completed, filter, wash, and dry to obtain KH560 modified nano-silica; wherein the KH560 dispersion accounts for 1%-3% of the nano-silica; S2, preparing anionic monomers; the specific process is: (a) DETPA, deionized water, water-soluble inhibitor and water-soluble catalyst are added into a reactor, mixed evenly and heated to 80-90°C. The added mass of water-soluble inhibitor is 0.01% to 0.03% of the mass of DETPA, the water-soluble catalyst is triethylamine, and the added amount is 1% to 3% of the mass of DETPA; the water-soluble inhibitor is 2,2,6,6-tetramethyl-4-hydroxypiperidinyl nitroxide free radical (TMHPO); (b) adding a vinyl epoxy monomer into a reaction kettle, wherein the molar ratio of DETPA to the vinyl epoxy monomer is 1:1.01 to 1:1.05, and reacting for 3-4 hours; the vinyl epoxy monomer is one or more of 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexyl methacrylate, and glycidyl methacrylate (GMA); (c) adjusting the pH value to 5.0-6.0 with NaOH to obtain anionic monomers; S3, mixing acrylamide monomer, hydrophilic monomer, rigid monomer, salt-tolerant monomer, copolymerization regulating monomer, cationic monomer, anionic monomer and solvent to obtain a monomer mixed solution; nitrogen is passed to remove oxygen, and the solvent is deionized water; S4, adding an initiator, raising the temperature to 70-80°C for copolymerization, wherein the initiator is one or both of ammonium persulfate and potassium persulfate, and the mass of the initiator accounts for 0.1%-0.2% of the acrylamide monomer; S5, add starch and continue stirring for 1 hour to obtain material flow A; S6. Evenly mix the KH560 modified nano-silica and alumina powder prepared in step S1, add the stream A, and evenly mix; further dry, crush, and grind to obtain zwitterionic polymer fluid loss reducer powder.

[0016] The anionic monomer side chain of the present invention has locally dense carboxylic acid anions, which can capture metal ions on the surface of soil particles through ion exchange, thereby holding on to the surface of soil particles, and the proportion of anionic monomers is small. In the copolymer molecular chain, the anionic monomers are far apart from each other, and it is not easy to cause molecular curling and agglomeration when salt ions invade; starch can form adhesion between soil particles to lock soil particles; KH560 modified nano silicon dioxide and aluminum oxide powder has the characteristics of large surface area, strong adsorption capacity, high temperature resistance and good plugging performance, which can enhance the adsorption performance and temperature resistance of the polymer, and can also enable the polymer to effectively fill the water loss channel inside the mud cake, thereby reducing filtration loss amount; rigid monomers with cyclic side chains can improve the rigidity of the main chain and prevent the main chain from curling; hydrophilic monomers with hydrophilic side chains and hydration groups such as carboxyl groups can improve their hydration ability, allowing the copolymer to be fully hydrated, so that the molecular chain can be fully stretched, and a strong solvated water film can be formed on the polymer chain segments, thereby improving the salt resistance; under the action of the above functional structures, the filtrate reducer can still remain stretched when it contacts the salt ions dissolved in the water; when the filtrate reducer contacts the well wall, it can spread and adhere to the well wall surface to form a low permeability, flexible, thin and dense filter cake, reducing the filtration loss of the drilling fluid to maintain the stability of the well wall, thereby ensuring underground safety.

[0017] In addition, the fluid loss reducer of the present invention can also be adsorbed on the surface of clay particles on the well wall at multiple points to form a crisscross macromolecular film, thereby enhancing the strength of the mudstone on the well wall. The hydration of the hydration group can form a compressible mud cake, thereby preventing water from penetrating into the formation and preventing clay hydration and expansion, thereby also having an anti-collapse effect. This solves the problem of the need to add multiple additives and the cumbersome configuration process during drilling operations. DETAILED DESCRIPTION

[0018] Preparation Example 1: Preparation of KH560 modified nano-silica: Nano-silica (particle size 100 nm) was dispersed in ethanol, and KH560 dispersion was added, mixed evenly, and reacted at 70°C for 3 hours. After the reaction was completed, KH560 modified nano-silica was obtained by filtration, washing, and drying. Among them, KH560 dispersion accounted for 3% of the nano-silica.

[0019] Preparation Example 2: Preparation of anionic monomer 1; the specific process is: (a) DETPA, deionized water, water-soluble inhibitor 2,2,6,6-tetramethyl-4-hydroxypiperidinyl nitroxide free radical (TMHPO), and water-soluble catalyst triethylamine were added into a reactor, mixed evenly, and heated to 85°C. The added mass of the water-soluble inhibitor was 0.03% of the mass of DETPA, the added amount of the water-soluble catalyst was 2% of the mass of DETPA, and the mass of deionized water was 1.5 times that of DETPA; (b) adding 3,4-epoxycyclohexylmethyl methacrylate into a reaction kettle, wherein the molar ratio of DETPA to 3,4-epoxycyclohexylmethyl methacrylate is 1:1.01, and reacting for 3 hours; (c) The pH value was adjusted to 5.5 with NaOH to obtain anionic monomer 1.

[0020] Preparation Example 3: Preparation of anionic monomer 2; the specific process is: (a) DETPA, deionized water, water-soluble inhibitor 2,2,6,6-tetramethyl-4-hydroxypiperidinyl nitroxide (TMHPO), and water-soluble catalyst triethylamine were added into a reactor, mixed evenly, and heated to 90°C. The amount of water-soluble inhibitor added was 0.01% of the mass of DETPA, the amount of water-soluble catalyst added was 3% of the mass of DETPA, and the mass of deionized water was twice that of DETPA; (b) adding 3,4-epoxycyclohexyl methacrylate into a reaction kettle, wherein the molar ratio of DETPA to 3,4-epoxycyclohexyl methyl methacrylate is 1:1.05, and reacting for 4 hours; (c) The pH value was adjusted to 6.0 with NaOH to obtain anionic monomer 2.

[0021] In combination with the above preparation examples, the present invention is implemented. The following is a raw material table of Examples 1-4 (by mass fraction).

[0022]

[0023] Example 1: The preparation method of zwitterionic polymer fluid loss reducer is as follows: (1) mixing acrylamide monomer, hydrophilic monomer, rigid monomer, salt-tolerant monomer, copolymerization regulating monomer, cationic monomer, anionic monomer and solvent to obtain a monomer mixed solution; nitrogen is passed to remove oxygen, and the solvent is deionized water; (2) raising the temperature to 70° C., adding an initiator to carry out a copolymerization reaction, wherein the initiator is ammonium persulfate, and the mass of the initiator accounts for 0.1% of the acrylamide monomer; (3) Add starch and continue stirring for 1 hour to obtain stream A; (4) KH560 modified nano-silica and alumina powder are mixed evenly, added to stream A, and mixed evenly; and further dried, crushed, and ground to obtain zwitterionic polymer filtrate reducer powder.

[0024] Embodiment 2: (1) mixing acrylamide monomer, hydrophilic monomer, rigid monomer, salt-tolerant monomer, copolymerization regulating monomer, cationic monomer, anionic monomer and solvent to obtain a monomer mixed solution; nitrogen is passed to remove oxygen, and the solvent is deionized water; (2) raising the temperature to 80° C., adding an initiator to carry out a copolymerization reaction, wherein the initiator is potassium persulfate, and the mass of the initiator accounts for 0.15% of the acrylamide monomer; (3) Add starch and continue stirring for 1 hour to obtain stream A; (4) KH560 modified nano-silica and alumina powder are mixed evenly, added to stream A, and mixed evenly; and further dried, crushed, and ground to obtain zwitterionic polymer filtrate reducer powder.

[0025] Embodiment 3: (1) mixing acrylamide monomer, hydrophilic monomer, rigid monomer, salt-tolerant monomer, copolymerization regulating monomer, cationic monomer, anionic monomer and solvent to obtain a monomer mixed solution; nitrogen is passed to remove oxygen, and the solvent is deionized water; (2) raising the temperature to 75° C., adding an initiator to carry out a copolymerization reaction, wherein the initiator is ammonium persulfate, and the mass of the initiator accounts for 0.15% of the acrylamide monomer; (3) Add starch and continue stirring for 1 hour to obtain stream A; (4) KH560 modified nano-silica and alumina powder are mixed evenly, added to stream A, and mixed evenly; and further dried, crushed, and ground to obtain zwitterionic polymer filtrate reducer powder.

[0026] Embodiment 4: (1) mixing acrylamide monomer, hydrophilic monomer, rigid monomer, salt-tolerant monomer, copolymerization regulating monomer, cationic monomer, anionic monomer and solvent to obtain a monomer mixed solution; nitrogen is passed to remove oxygen, and the solvent is deionized water; (2) raising the temperature to 80° C., adding an initiator to carry out a copolymerization reaction, wherein the initiator is ammonium persulfate, and the mass of the initiator accounts for 0.15% of the acrylamide monomer; (3) Add starch and continue stirring for 1 hour to obtain stream A; (4) KH560 modified nano-silica and alumina powder are mixed evenly, added to stream A, and mixed evenly; and further dried, crushed, and ground to obtain zwitterionic polymer filtrate reducer powder.

[0027] Comparative Example 1: The difference between this comparative example and Example 1 is that: Anionic monomer 1 was replaced by an equal amount of sodium acrylate.

[0028] Comparative Example 2: The difference between this comparative example and Example 2 is that: The rigid monomer was replaced with an equal amount of acrylamide.

[0029] Comparative Example 3: The difference between this comparative example and Example 3 is that: The salt-tolerant monomer was replaced with an equal amount of acrylamide.

[0030] Comparative Example 4: This comparative example is different from comparative example 1 in that no hydrophilic monomer is used.

[0031] The fluid loss reducers prepared in the examples and comparative examples were added to the saturated brine base slurry at an amount of 2% for performance evaluation. The apparent viscosity AV1 and API (0.69 MPa) fluid loss FLAPI of the saturated brine base slurry before hot rolling, and the apparent viscosity AV2 and high temperature and high pressure fluid loss (3.45 MPa, 220°C) FLHTHP after hot rolling at 220°C for 16 hours were tested.

[0032] Preparation of saturated salt water base slurry: add 0.42g anhydrous sodium carbonate and 7.0g bentonite to 350ml distilled water, stir at high speed for 20min, and keep in a sealed container for 24h. Add 10.5g sulfonated lignite under stirring, stir at high speed for 5min, then add 105g sodium chloride, stir at high speed for 20min, and keep in a sealed container for 2-4h to prepare saturated salt water base slurry.

[0033] The experimental results are shown in the following table.

[0034]

[0035] The product prepared by the preparation method provided by the present invention has good temperature and salt resistance, and can not only significantly reduce the API filtration loss of saturated salt water base slurry, but also significantly reduce its high temperature and high pressure filtration loss. After high temperature hot rolling, the drilling fluid has stable performance, good apparent viscosity control, and can maintain good rheology in a high-density drilling fluid system.

Claims

1. A zwitterionic polymer fluid loss reducer, characterized in that: The components include, by mass: 100 parts of acrylamide monomer, 20-30 parts of hydrophilic monomer, 10-20 parts of rigid monomer, 30-50 parts of salt-tolerant monomer, 10-20 parts of copolymerization regulating monomer, 30-50 parts of starch, 3-5 parts of alumina powder, 5-10 parts of KH560 modified nano-silicon dioxide, 5-10 parts of cationic monomer and 5-10 parts of anionic monomer; The cationic monomer is one or more of acryloyloxyethyl trimethyl ammonium chloride and allyl trimethyl ammonium chloride; The salt-tolerant monomer is one or more of N-phenylacrylamide, dimethylaminopropylacrylamide, and N-hydroxymethylacrylamide; The copolymerization regulating monomer is one or more of methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, and hydroxyethyl methacrylate; The rigid monomer is a vinyl monomer having a cyclic group on the side chain, and more preferably one or more of styrene, α-methylstyrene, isobornyl acrylate, isobornyl methacrylate, 1-adamantyl acrylate, 1-adamantyl methacrylate, methacrylate (2-methyl-2-adamantyl ester), and 2-ethyl-2-adamantyl methacrylate; The hydrophilic monomer is polyethylene glycol methyl ether methacrylate; The starch is one or more of corn starch, tapioca starch, sweet potato starch and potato starch; The particle size of KH560 modified nano-silica ranges from 100nm to 500nm, and the particle size of alumina ranges from 1-20um.

2. The method for preparing a zwitterionic polymer fluid loss reducer according to claim 1, characterized in that: The following steps are included S1. The process of preparing KH560 modified nano-silica is as follows: dispersing nano-silica in ethanol, adding KH560 dispersion, mixing evenly, and reacting at 70° C. for 3 hours; after the reaction is completed, filtering, washing, and drying to obtain KH560 modified nano-silica; wherein the KH560 dispersion accounts for 1%-3% of the nano-silica; S2. The process of preparing anionic monomers is as follows: (a) adding diethylenetriaminepentaacetic acid (DETPA), deionized water, a water-soluble inhibitor and a water-soluble catalyst into a reaction kettle, mixing them evenly, and heating them to 80-90° C., wherein the mass of the water-soluble inhibitor added is 0.01% to 0.03% of the mass of DETPA, and the water-soluble catalyst is triethylamine, and the amount added is 1% to 3% of the mass of DETPA; the water-soluble inhibitor is 2,2,6,6-tetramethyl-4-hydroxypiperidinyl nitroxide free radical (TMHPO); (b) adding a vinyl epoxy monomer into a reaction kettle, wherein the molar ratio of DETPA to the vinyl epoxy monomer is 1:1.01 to 1:1.05, and reacting for 3-4 hours; the vinyl epoxy monomer is one or more of 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexyl methacrylate, and glycidyl methacrylate (GMA); (c) adjusting the pH to 5.0-6.0 with NaOH to obtain anionic monomers; S3, mixing acrylamide monomer, hydrophilic monomer, rigid monomer, salt-tolerant monomer, copolymerization regulating monomer, cationic monomer, anionic monomer and solvent to obtain a monomer mixed solution; nitrogen is passed to remove oxygen, and the solvent is deionized water; S4, adding an initiator, raising the temperature to 70-80°C for copolymerization, wherein the initiator is one or both of ammonium persulfate and potassium persulfate, and the mass of the initiator accounts for 0.1%-0.2% of the acrylamide monomer; S5, add starch and continue stirring for 1 hour to obtain material flow A; S6. Evenly mix the KH560 modified nano-silica and alumina powder prepared in step S1, add the stream A, and evenly mix; further dry, crush, and grind to obtain zwitterionic polymer fluid loss reducer powder.

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