Gas wetting agent suitable for compact sandstone reservoir and preparation method of gas wetting agent

Abstract

The invention discloses a gas wetting agent suitable for a compact sandstone reservoir. The gas wetting agent is prepared from a methacrylate monomer, a fluorine-containing monomer, polymer dihydric alcohol, a diisocyanate compound, a sulfonate chain extender, a catalyst, an end-capping monomer and a post-chain extender, the invention also discloses a preparation method of the gas wetting agent. The preparation method specifically comprises the following steps: mixing a methacrylate monomer and a fluorine-containing monomer to obtain a solution A; adding polymer dihydric alcohol, a diisocyanate compound, a sulfonate chain extender and a catalyst into the solution A, and reacting to obtain a solution B; adding an end-capping monomer into the solution B, and then adding an aqueous solution of a post-chain extender to obtain a dispersion C; and adding di-tert-butyl hydroperoxide-ferrous pyrophosphate into the dispersion C, cooling, and adding small molecular alcohols to obtain the gas wetting agent. According to the compact sandstone reservoir gas wetting agent and the preparation method thereof, the prepared gas wetting agent has relatively strong adsorption capacity and good dispersity, the preparation process is simple, and the energy consumption is low.

Description

Technical Field

[0001] The invention belongs to the technical field of tight sandstone gas fracturing production enhancement and transformation, relates to a gas wetting agent suitable for tight sandstone reservoirs, and also relates to a preparation method of the gas wetting agent. Background Art

[0002] The development of tight sandstone gas in my country has developed rapidly and has become the first focus of unconventional oil and gas resources. The source rocks and reservoirs of unconventional oil and gas resources are characterized by low porosity and ultra-low permeability. Changing the wettability of shale layers can effectively increase crude oil recovery.

[0003] Wetting refers to the phenomenon that one fluid is replaced by another fluid on the solid interface. The wettability of reservoir rocks generally includes water-wetting, oil-wetting and neutral wetting. Wettability refers to the tendency of a certain fluid to expand to the solid surface when other immiscible fluids exist. In 2000, some researchers used fluorinated surfactants to treat solids to make their surfaces hydrophobic and oleophobic, and have amphiphobicity, achieving the purpose of gas-wetting. The wettability of the rock surface is reversed from liquid-wetting to gas-wetting. Gas-wetting rocks are neither hydrophilic nor oleophilic, and have good amphiphobicity. Using fluorinated surfactants to treat can reverse the wettability near the wellbore of the condensate gas reservoir from liquid-wetting to gas-wetting, which can improve the fluidity of the liquid phase in the reservoir, increase the relative permeability of the liquid phase, and ultimately increase the production capacity of the gas well. The basic theoretical research on the gas-wetting of reservoir rocks has become a new research field in the petroleum industry and the colloid interface chemistry community, and is expected to become a new means of tertiary oil recovery. The mechanism of gas-wetness enhanced oil recovery is due to the molecular film formed by the adsorption of fluorocarbon surfactants on the rock surface. The surfactant molecules are adsorbed on the core surface, reversing the wettability of the core surface from liquid-wet to gas-wet, enhancing the seepage capacity of the liquid phase, thereby achieving the purpose of improving oil recovery.

[0004] Fluorinated surfactants have the special properties of being both hydrophobic and oleophobic, and can achieve gas wetting. This is because compounds containing a large number of CF bonds have low intermolecular cohesion, which results in a reduction in surface free energy, forming a unique property that is difficult to wet and adhere to various liquids. However, for dense sandstone reservoirs, small-molecule fluorocarbon surfactants have weak adsorption and are easily washed down by the wellbore liquid, and cannot achieve long-term effectiveness; perfluorinated polymer homopolymers have large molecular sizes and cannot enter dense reservoirs, or have poor solubility and dispersibility, poor stability, and cannot be used. Summary of the invention

[0005] The purpose of the invention is to provide a gas wetting agent suitable for tight sandstone reservoirs, which solves the problems of weak adsorption, poor dispersibility and poor stability of existing wetting agents.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned gas wetting agent.

[0007] The technical scheme adopted by the present invention is suitable for a gas wetting agent for tight sandstone reservoirs, and is composed of methacrylate monomers, fluorine-containing monomers, polymer diols, diisocyanate compounds, sulfonate chain extenders, catalysts, end-capping monomers and post-chain extenders, wherein the methacrylate monomers are 7 to 14 parts, the fluorine-containing monomers are 0.7 to 3.5 parts, the polymer diols are 3.3 to 5 parts, the diisocyanate compounds are 10 to 13 parts, the sulfonate chain extenders are 1.1 to 2.7 parts, the catalysts are 0.01 to 0.09 parts, the end-capping monomers are 1.5 to 6 parts and the post-chain extenders are 90 to 150 parts.

[0008] The present invention is also characterized in that:

[0009] The methacrylate monomer is one of hexyl methacrylate, n-octyl methacrylate and 2-ethylhexyl methacrylate, or a mixture of two or more of them in any proportion;

[0010] The fluorine-containing monomer is trifluoroethyl acrylate, hexafluorobutyl acrylate, dodecafluoroheptyl acrylate, perfluorooctyl ethyl acrylate, nonadecafluoro acrylate, perfluorooctyl (N-methyl-N-ethyl acrylate) sulfonamide, perfluorooctyl (N-ethyl-N-ethyl acrylate) sulfonamide, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, nonadecafluoro methacrylate, perfluorooctyl (N-methyl-N-ethyl methacrylate) sulfonamide or perfluorooctyl (N-ethyl-N-ethyl methacrylate) sulfonamide;

[0011] The polymer diol is one or a mixture of any two of poly(hexane adipate), poly(butylene adipate), polycaprolactone diol, polycarbonate diol, and polytetramethylene glycol, and the molecular weight thereof is between 1000 and 2000;

[0012] The diisocyanate compound is dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate or cyclohexane dimethylene diisocyanate;

[0013] The sulfonate chain extender is one or a mixture of any two of 1,2-dihydroxypropanesulfonate sodium, 2-aminoethylaminoethanesulfonate sodium, 2,4-diaminobenzenesulfonate sodium and 1,4-butanediol-2-sulfonate sodium;

[0014] The catalyst is dibutyltin dilaurate, dibutyltin diacetate or stannous octoate;

[0015] The end-capping monomer is one or a mixture of any two of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate and hydroxymethyl acrylamide;

[0016] The post-chain extender is sodium ethylenediamine ethanesulfonate or sodium ethylenediamine di-o-phenylacetate.

[0017] Another technical solution adopted by the present invention is that the preparation method of the above-mentioned gas wetting agent is specifically implemented according to the following steps:

[0018] S1, mixing 7 to 14 parts of methacrylate monomers and 0.7 to 3.5 parts of fluorine-containing monomers to obtain solution A;

[0019] S2, adding 3.3-5 parts of polymer diol, 10-13 parts of diisocyanate compound, 1.1-2.7 parts of sulfonate chain extender and 0.01-0.09 parts of catalyst to solution A for sufficient reaction to obtain polyurethane prepolymer solution B;

[0020] S3, adding 1.5 to 6 parts of end-capping monomer to solution B for end-capping, and then adding 90 to 150 parts of aqueous solution of post-chain extender and stirring for 15 to 30 minutes to obtain polyurethane dispersion C;

[0021] S4. Add di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator to the dispersion C for reaction, cool down, and then add small molecule alcohols to obtain a gas wetting agent suitable for tight sandstone reservoirs.

[0022] Another technical solution of the present invention is also characterized in that:

[0023] The methacrylate monomer in S1 is one of hexyl methacrylate, n-octyl methacrylate and 2-ethylhexyl methacrylate, or a mixture of two or more of them in any ratio;

[0024] The fluorine-containing monomer in S1 is trifluoroethyl acrylate, hexafluorobutyl acrylate, dodecafluoroheptyl acrylate, perfluorooctyl ethyl acrylate, nonadecafluoro acrylate, perfluorooctyl (N-methyl-N-ethyl acrylate) sulfonamide, perfluorooctyl (N-ethyl-N-ethyl acrylate) sulfonamide, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, nonadecafluoro methacrylate, perfluorooctyl (N-methyl-N-ethyl methacrylate) sulfonamide or perfluorooctyl (N-ethyl-N-ethyl methacrylate) sulfonamide.

[0025] The polymer diol in S2 is one or a mixture of any two of poly(hexane adipate), poly(butylene adipate), poly(caprolactone diol), polycarbonate diol, and polytetramethylene glycol, and its molecular weight is between 1000 and 2000;

[0026] The diisocyanate compound in S2 is dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate or cyclohexane dimethylene diisocyanate;

[0027] The sulfonate chain extender in S2 is one or a mixture of any two of 1,2-dihydroxypropanesulfonate, sodium 2-aminoethylaminoethanesulfonate, sodium 2,4-diaminobenzenesulfonate and sodium 1,4-butanediol-2-sulfonate;

[0028] The catalyst in S2 is dibutyltin dilaurate, dibutyltin diacetate or stannous octoate.

[0029] The end-capping monomer in S3 is one or a mixture of any two of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate and hydroxymethyl acrylamide;

[0030] The post-chain extender in S3 is sodium ethylenediamine ethanesulfonate or sodium ethylenediamine di-o-phenylacetate; the mass concentration of the aqueous solution of the post-chain extender is 0.5% to 4%.

[0031] The small molecule alcohols in S4 are one or a mixture of two or more of methanol, ethanol, ethylene glycol, n-propanol and isopropanol in any proportion.

[0032] The temperature for full reaction in S2 is 70-90°C and the time is 2-4.5h.

[0033] The end-capping in S3 is specifically as follows: after sufficient reaction for 0.5 to 2 hours, the system temperature is cooled to 25 to 45°C.

[0034] The mass ratio of dispersion C and di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator in S4 is 100:(0.05-0.5), the reaction temperature is 75-85°C, and the reaction time is 3-5h.

[0035] The beneficial effects of the present invention are:

[0036] (1) The present invention is applicable to a gas wetting agent for tight sandstone reservoirs and a preparation method thereof. In the synthesis process, methacrylate monomers are used as "similar solvents" to replace volatile organic solvents, and sulfonate chain extenders are used to replace traditional carboxyl chain extenders. There is no need to use amine neutralizers. The prepared fluorinated polyurethane emulsion has no irritating ammonia odor and no volatile organic compounds, and is a non-toxic, green and environmentally friendly polymer material.

[0037] (2) The present invention is suitable for a gas wetting agent for a dense sandstone reservoir and a preparation method thereof. Fluorine-containing polyurethane can be solidified on the surface of a core matrix to form a hydrophobic and oleophobic film. The preparation method is simple and has strong operability. The fluorine-containing polyurethane is encapsulated and solidified on the surface of the substrate through immersion and drying. The film has greater compressive strength and strong hydrophobic and oleophobic properties.

[0038] (3) The present invention is applicable to a gas wetting agent for tight sandstone reservoirs and a preparation method thereof. On the one hand, the polar end of the fluorinated polyurethane is adsorbed on the negatively charged core surface, and the non-polar end of the molecular chain is oriented outward. Due to the hydrophobic and oleophobic properties of the fluorine atoms, the rock surface has neutral gas moisture, which is manifested as a larger contact angle between the water phase and the oil phase on the rock surface. On the other hand, since small molecule alcohols are added to the system of the present invention, the alcohol substances are volatile and can play a role in carrying liquid in the reservoir, and the water phase and the alcohol can form a mixed solution, which reduces the surface tension and capillary resistance, facilitates flowback, and relieves water lock damage.

[0039] (4) The present invention is applicable to a gas wetting agent for tight sandstone reservoirs and a preparation method thereof. The chain extender and post-chain extender used are both of the sulfonate type, replacing the traditional carboxylic acid type chain extender. No neutralizer is needed to obtain a fluorine-containing polyurethane emulsion with good dispersibility and stability. Moreover, the emulsion can be added with small molecule alcohols without demulsification, and has very good dispersibility, which is convenient for on-site liquid preparation and use. The gas wetting agent can successfully achieve gas wetting reversal on the surface of tight sandstone, and can effectively transform the surface of the tight sandstone layer from liquid wettability to gas wettability. The preparation method thereof is simple and easy, thereby significantly improving the production of tight sandstone gas wells. DETAILED DESCRIPTION

[0040] The present invention is described in detail below in conjunction with specific implementation modes.

[0041] The invention is suitable for a gas wetting agent for tight sandstone reservoirs, and is composed of methacrylate monomers, fluorine-containing monomers, polymer diols, diisocyanate compounds, sulfonate chain extenders, catalysts, end-capping monomers and post-chain extenders, wherein the methacrylate monomers are 7 to 14 parts, the fluorine-containing monomers are 0.7 to 3.5 parts, the polymer diols are 3.3 to 5 parts, the diisocyanate compounds are 10 to 13 parts, the sulfonate chain extenders are 1.1 to 2.7 parts, the catalysts are 0.01 to 0.09 parts, the end-capping monomers are 1.5 to 6 parts and the post-chain extenders are 90 to 150 parts.

[0042] The methacrylate monomer is one of hexyl methacrylate, n-octyl methacrylate and 2-ethylhexyl methacrylate, or a mixture of two or more of them in any proportion;

[0043] The fluorine-containing monomer is trifluoroethyl acrylate, hexafluorobutyl acrylate, dodecafluoroheptyl acrylate, perfluorooctyl ethyl acrylate, nonadecafluoro acrylate, perfluorooctyl (N-methyl-N-ethyl acrylate) sulfonamide, perfluorooctyl (N-ethyl-N-ethyl acrylate) sulfonamide, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, nonadecafluoro methacrylate, perfluorooctyl (N-methyl-N-ethyl methacrylate) sulfonamide or perfluorooctyl (N-ethyl-N-ethyl methacrylate) sulfonamide;

[0044] The polymer diol is one or a mixture of any two of poly(hexane adipate), poly(butylene adipate), polycaprolactone diol, polycarbonate diol, and polytetramethylene glycol, and the molecular weight thereof is between 1000 and 2000;

[0045] The diisocyanate compound is dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate or cyclohexane dimethylene diisocyanate;

[0046] The sulfonate chain extender is one or a mixture of any two of 1,2-dihydroxypropanesulfonate sodium, 2-aminoethylaminoethanesulfonate sodium, 2,4-diaminobenzenesulfonate sodium and 1,4-butanediol-2-sulfonate sodium;

[0047] The catalyst is dibutyltin dilaurate, dibutyltin diacetate or stannous octoate;

[0048] The end-capping monomer is one or a mixture of any two of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate and hydroxymethyl acrylamide;

[0049] The post-chain extender is sodium ethylenediamine ethanesulfonate or sodium ethylenediamine di-o-phenylacetate.

[0050] The present invention is applicable to the preparation method of a gas wetting agent for a tight sandstone reservoir, and is specifically implemented according to the following steps:

[0051] S1, mixing 7 to 14 parts of methacrylate monomers and 0.7 to 3.5 parts of fluorine-containing monomers to obtain solution A;

[0052] The methacrylate monomer in S1 is one of hexyl methacrylate, n-octyl methacrylate and 2-ethylhexyl methacrylate, or a mixture of two or more of them in any ratio;

[0053] The fluorine-containing monomer in S1 is trifluoroethyl acrylate, hexafluorobutyl acrylate, dodecafluoroheptyl acrylate, perfluorooctyl ethyl acrylate, nonadecafluoro acrylate, perfluorooctyl (N-methyl-N-ethyl acrylate) sulfonamide, perfluorooctyl (N-ethyl-N-ethyl acrylate) sulfonamide, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, nonadecafluoro methacrylate, perfluorooctyl (N-methyl-N-ethyl methacrylate) sulfonamide or perfluorooctyl (N-ethyl-N-ethyl methacrylate) sulfonamide.

[0054] S2, adding 3.3-5 parts of polymer diol, 10-13 parts of diisocyanate compound, 1.1-2.7 parts of sulfonate chain extender and 0.01-0.09 parts of catalyst to solution A for sufficient reaction to obtain polyurethane prepolymer solution B;

[0055] The polymer diol in S2 is one or a mixture of any two of poly(hexane adipate), poly(butylene adipate), poly(caprolactone diol), polycarbonate diol, and polytetramethylene glycol, and its molecular weight is between 1000 and 2000;

[0056] The diisocyanate compound in S2 is dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate or cyclohexane dimethylene diisocyanate;

[0057] The sulfonate chain extender in S2 is one or a mixture of any two of 1,2-dihydroxypropanesulfonate, sodium 2-aminoethylaminoethanesulfonate, sodium 2,4-diaminobenzenesulfonate and sodium 1,4-butanediol-2-sulfonate;

[0058] The catalyst in S2 is dibutyltin dilaurate, dibutyltin diacetate or stannous octoate.

[0059] S3, adding 1.5 to 6 parts of end-capping monomer to solution B for end-capping, and then adding 90 to 150 parts of aqueous solution of post-chain extender and stirring for 15 to 30 minutes to obtain polyurethane dispersion C;

[0060] The end-capping monomer in S3 is one or a mixture of any two of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate and hydroxymethyl acrylamide;

[0061] The post-chain extender in S3 is sodium ethylenediamine ethanesulfonate or sodium ethylenediamine di-o-phenylacetate; the mass concentration of the aqueous solution of the post-chain extender is 0.5% to 4%.

[0062] S4. Add di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator to the dispersion C for reaction, cool down, and then add small molecule alcohols to obtain a gas wetting agent suitable for tight sandstone reservoirs.

[0063] The small molecule alcohols in S4 are one or a mixture of two or more of methanol, ethanol, ethylene glycol, n-propanol and isopropanol in any proportion.

[0064] The temperature for full reaction in S2 is 70-90°C and the time is 2-4.5h.

[0065] The end-capping in S3 is specifically as follows: after sufficient reaction for 0.5 to 2 hours, the system temperature is cooled to 25 to 45°C.

[0066] The mass ratio of dispersion C and di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator in S4 is 100:(0.05-0.5), the reaction temperature is 75-85°C, and the reaction time is 3-5h.

[0067] Example 1

[0068] S1. Mix 7 parts of hexyl methacrylate and 1 part of hexafluorobutyl acrylate to obtain solution A;

[0069] S2, adding 3.5 parts of polytetrahydrofuran diol, 10 parts of dicyclohexylmethane diisocyanate, 1.3 parts of sodium 1,2-dihydroxypropanesulfonate and 0.02 parts of dibutyltin dilaurate to solution A, and fully reacting at 75° C. for 2.5 hours to obtain a polyurethane prepolymer solution B;

[0070] S3, adding 1.5 parts of hydroxyethyl methacrylate to solution B for end-capping, and after fully reacting for 1 hour, the system temperature was cooled to 30°C, 90 parts of a 0.5% sodium ethylenediaminesulfonate aqueous solution was added, and stirred for 21 minutes to disperse evenly, to obtain a polyurethane dispersion C;

[0071] S4. Add di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator to dispersion C, the mass ratio of dispersion C to di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator is 100:0.46, react at 75°C for 5 hours to obtain an environmentally friendly fluorine-containing polyurethane emulsion, cool down, add 10 parts of methanol, and obtain a gas wetting agent suitable for tight sandstone reservoirs.

[0072] Example 2

[0073] S1. Mix 9 parts of n-octyl methacrylate and 1.5 parts of perfluorooctyl (N-methyl-N-ethyl acrylate) sulfonamide to obtain a solution A;

[0074] S2, adding 4.5 parts of polycaprolactone diol, 12 parts of isophorone diisocyanate, 1.8 parts of sodium 2-aminoethylaminoethanesulfonate and 0.018 parts of dibutyltin diacetate to solution A, and fully reacting at 80° C. for 3.5 hours to obtain a polyurethane prepolymer solution B;

[0075] S3, adding 2.6 parts of hydroxypropyl methacrylate to solution B for end-capping, and after fully reacting for 1.2 hours, the system temperature was cooled to 28°C, 120 parts of a 3% mass concentration of sodium ethylenediamine di-o-phenylacetate aqueous solution was added, and stirred for 19 minutes to disperse evenly, to obtain a polyurethane dispersion C;

[0076] S4. Add di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator to dispersion C, the mass ratio of dispersion C to di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator is 100:0.3, react at 80°C for 4.5 hours to obtain an environmentally friendly fluorine-containing polyurethane emulsion, cool down, add 15 parts of ethanol, and obtain a gas wetting agent suitable for tight sandstone reservoirs.

[0077] Example 3

[0078] S1. Mix 11 parts of 2-ethylhexyl methacrylate and 2.5 parts of perfluorooctyl (N-ethyl-N-ethyl acrylate) sulfonamide to obtain a solution A;

[0079] S2, adding 5 parts of poly(hexamethylene adipate), 12.5 parts of hexamethylene diisocyanate, 2.1 parts of sodium 2,4-diaminobenzenesulfonate and 0.021 parts of stannous octoate to solution A, and fully reacting at 85° C. for 2 hours to obtain a polyurethane prepolymer solution B;

[0080] S3, adding 2.9 parts of hydroxypropyl acrylate end-capping monomer to solution B for end-capping, and after fully reacting for 1 hour, the system temperature was cooled to 35° C., 130 parts of 2% mass concentration of sodium ethylenediamine di-o-phenylacetate aqueous solution was added, and stirred for 22 minutes to disperse evenly, to obtain polyurethane dispersion C;

[0081] S4. Add di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator to dispersion C, the mass ratio of dispersion C to di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator is 100:0.5, react at 83°C for 4 hours to obtain an environmentally friendly fluorine-containing polyurethane emulsion, cool down, add 24 parts of ethylene glycol, and obtain a gas wetting agent suitable for tight sandstone reservoirs.

[0082] Example 4

[0083] S1. Mix 12.5 parts of hexyl methacrylate and 3 parts of hexafluorobutyl methacrylate to obtain solution A;

[0084] S2, adding 4.6 parts of polybutylene adipate, 13 parts of dicyclohexylmethane diisocyanate, 2.4 parts of 1,4-butanediol-2-sulfonic acid sodium and 0.039 parts of dibutyltin diacetate to solution A, and fully reacting at 75° C. for 4 hours to obtain a polyurethane prepolymer solution B;

[0085] S3, adding 3 parts of hydroxymethyl acrylamide to solution B for end-capping, and after fully reacting for 1.5 hours, the system temperature was cooled to 30°C, 118 parts of a 0.9% sodium ethylenediamine sulfonate aqueous solution was added, and stirred for 26 minutes to disperse evenly, to obtain a polyurethane dispersion C;

[0086] S4. Add di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator to dispersion C, the mass ratio of dispersion C to di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator is 100:0.09, react at 85°C for 3 hours to obtain an environmentally friendly fluorine-containing polyurethane emulsion, cool down, add 18 parts of n-propanol, and obtain a gas wetting agent suitable for tight sandstone reservoirs.

[0087] Example 5

[0088] S1. Mix 13 parts of n-octyl methacrylate and 2.5 parts of dodecafluoroheptyl methacrylate to obtain solution A;

[0089] S2, adding 4.7 parts of polycarbonate diol, 12.5 parts of 1,4-cyclohexane diisocyanate, 1.7 parts of sodium 2,4-diaminobenzenesulfonate and 0.02 parts of dibutyltin dilaurate to solution A, and fully reacting at 79° C. for 3 hours to obtain a polyurethane prepolymer solution B;

[0090] S3, adding 1.9 parts of hydroxybutyl acrylate end-capping monomer to solution B for end-capping, after fully reacting for 0.5 hours, cooling the system temperature to 45°C, adding 136 parts of 2.5% mass concentration of sodium ethylenediamine di-o-phenylacetate aqueous solution, stirring for 25 minutes to disperse evenly, to obtain polyurethane dispersion C;

[0091] S4. Add di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator to dispersion C, the mass ratio of dispersion C to di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator is 100:0.21, react at 75°C for 3.5 hours to obtain an environmentally friendly fluorine-containing polyurethane emulsion, cool down, add 20 parts of isopropanol, and obtain a gas wetting agent suitable for tight sandstone reservoirs.

[0092] 1. Performance test:

[0093] Contact angle test: Select dense natural sandstone, cut it into slices of uniform size, soak it in the prepared 0.5% gas wetting agent aqueous solution, soak it at 90℃ for 12h, take it out and dry it. Measure the contact angles of brine and kerosene on the surface of the core slices, and the results are shown in Table 1:

[0094] Table 1 Contact angles of water and oil phases in the gas-liquid-solid system

[0095]

[0096] The contact angles of the water phase and the oil phase on the untreated core surface are 25° and 0°, respectively, and the contact angles of the two phases are less than 90°, and the wettability of the core surface is liquid wet. The cores were treated with 0.5% wetting agent solution, and the contact angles of the water phase and the oil phase on the core surface were measured. Compared with the contact angles of the untreated core surface, the contact angles of the water phase and the oil phase on the treated core surface were significantly increased, and the contact angles of the water phase and the oil phase were increased from 25° and 0° when untreated to 121° and 61°, 121° and 63°, 123° and 70°, 134° and 67° and 131° and 62°, indicating that the gas wetting agent of the present invention has a good gas wetting reversal effect. After being treated with the gas wetting agent prepared by the present invention, the hydrophobicity and oleophobicity of the rock surface are significantly increased, the contact area of ​​the water phase on the core surface is smaller, the viscous resistance of its flow is smaller, and it is easier to flow, thereby effectively improving the flow condition of the fluid in the porous medium and solving the water lock effect.

[0097] 2. Gas drive discharge rate test: Fill a certain mass of proppant or a mixture of proppant and core powder in a ratio of 1:1 into a dry vertical chromatography column, weigh and record m1, add water / 0.5% gas well wetting agent to the chromatography column until the chromatography column is saturated, wait for 10 minutes, weigh and record m2. Place the chromatography column horizontally, pass nitrogen on one side at a pressure of 10KPa, and use a constant-weight conical flask on the other side to collect the liquid discharged. Record the mass of the liquid flowing out after 5 minutes as m3, then the discharge rate = m3 / (m2-m1)*100%. The discharge rate test results of Example 2 are shown in Table 2:

[0098] Table 2 Discharge rate test results

[0099]

[0100] In summary, the present invention is suitable for the preparation method of a gas wetting agent for tight sandstone reservoirs, the preparation process is simple, the energy consumption is low, and the stability is strong; the gas wetting agent prepared by the method of the present invention can successfully achieve the gas wetting reversal of the tight sandstone surface, and can effectively transform the surface of the tight sandstone layer from liquid wettability to gas wettability, and its preparation method is simple and easy, thereby significantly improving the production of tight sandstone gas wells.

Claims

1. Suitable for tight sandstone reservoir gas wetting agent, characterized by: The invention is composed of methacrylate monomer, fluorine-containing monomer, polymer diol, diisocyanate compound, sulfonate chain extender, catalyst, end-capping monomer and post-chain extender, including 7-14 parts of methacrylate monomer, 0.7-3.5 parts of fluorine-containing monomer, 3.3-5 parts of polymer diol, 10-13 parts of diisocyanate compound, 1.1-2.7 parts of sulfonate chain extender, 0.01-0.09 parts of catalyst, 1.5-6 parts of end-capping monomer and 90-150 parts of post-chain extender.

2. The gas wetting agent suitable for tight sandstone reservoirs according to claim 1, characterized in that: The methacrylate monomer is one of hexyl methacrylate, n-octyl methacrylate and 2-ethylhexyl methacrylate, or a mixture of two or more of them in any ratio; The fluorine-containing monomer is trifluoroethyl acrylate, hexafluorobutyl acrylate, dodecafluoroheptyl acrylate, perfluorooctyl ethyl acrylate, nonadecafluoro acrylate, perfluorooctyl (N-methyl-N-ethyl acrylate) sulfonamide, perfluorooctyl (N-ethyl-N-ethyl acrylate) sulfonamide, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, nonadecafluoro methacrylate, perfluorooctyl (N-methyl-N-ethyl methacrylate) sulfonamide or perfluorooctyl (N-ethyl-N-ethyl methacrylate) sulfonamide; The polymer diol is one or a mixture of any two of poly(hexane adipate), poly(butylene adipate), polycaprolactone diol, polycarbonate diol, and polytetrahydrofuran diol, and the molecular weight thereof is between 1000 and 2000; The diisocyanate compound is dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate or cyclohexane dimethylene diisocyanate; The sulfonate chain extender is one or a mixture of any two of 1,2-dihydroxypropanesulfonate sodium, 2-aminoethylaminoethanesulfonate sodium, 2,4-diaminobenzenesulfonate sodium and 1,4-butanediol-2-sulfonate sodium; The catalyst is dibutyltin dilaurate, dibutyltin diacetate or stannous octoate; The end-capping monomer is one or a mixture of any two of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate and hydroxymethyl acrylamide; The post-chain extender is sodium ethylenediamine ethanesulfonate or sodium ethylenediamine di-o-phenylacetate.

3. A method for preparing the gas wetting agent according to any one of claims 1 to 2, characterized in that: Follow the steps below to implement it: S1, mixing 7 to 14 parts of methacrylate monomers and 0.7 to 3.5 parts of fluorine-containing monomers to obtain solution A; S2, adding 3.3-5 parts of polymer diol, 10-13 parts of diisocyanate compound, 1.1-2.7 parts of sulfonate chain extender and 0.01-0.09 parts of catalyst to solution A for sufficient reaction to obtain polyurethane prepolymer solution B; S3, adding 1.5 to 6 parts of end-capping monomer to solution B for end-capping, and then adding 90 to 150 parts of aqueous solution of post-chain extender and stirring for 15 to 30 minutes to obtain polyurethane dispersion C; S4. Add di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator to the dispersion C for reaction, cool down, and then add small molecule alcohols to obtain a gas wetting agent suitable for tight sandstone reservoirs.

4. The method for preparing the gas wetting agent according to claim 3, characterized in that: The methacrylate monomer in S1 is one or a mixture of two or more of hexyl methacrylate, n-octyl methacrylate and 2-ethylhexyl methacrylate in any ratio; The fluorine-containing monomer in S1 is trifluoroethyl acrylate, hexafluorobutyl acrylate, dodecafluoroheptyl acrylate, perfluorooctyl ethyl acrylate, nonadecafluoro acrylate, perfluorooctyl (N-methyl-N-ethyl acrylate) sulfonamide, perfluorooctyl (N-ethyl-N-ethyl acrylate) sulfonamide, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, nonadecafluoro methacrylate, perfluorooctyl (N-methyl-N-ethyl methacrylate) sulfonamide or perfluorooctyl (N-ethyl-N-ethyl methacrylate) sulfonamide.

5. The method for preparing the gas wetting agent according to claim 3, characterized in that: The polymer diol in S2 is one or a mixture of any two of poly(hexane adipate), poly(butylene adipate), polycaprolactone diol, polycarbonate diol, and polytetrahydrofuran diol, and its molecular weight is between 1000 and 2000; The diisocyanate compound in S2 is dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate or cyclohexane dimethylene diisocyanate; The sulfonate chain extender in S2 is one or a mixture of any two of 1,2-dihydroxypropanesulfonate, sodium 2-aminoethylaminoethanesulfonate, sodium 2,4-diaminobenzenesulfonate and sodium 1,4-butanediol-2-sulfonate; The catalyst in S2 is dibutyltin dilaurate, dibutyltin diacetate or stannous octoate.

6. The method for preparing the gas wetting agent according to claim 3, characterized in that: The end-capping monomer in S3 is one or a mixture of any two of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate and hydroxymethyl acrylamide; The post-chain extender in S3 is sodium ethylenediamine ethanesulfonate or sodium ethylenediamine di-o-phenylacetate; the mass concentration of the aqueous solution of the post-chain extender is 0.5% to 4%.

7. The method for preparing the gas wetting agent according to claim 3, characterized in that: The small molecule alcohol in S4 is one of methanol, ethanol, ethylene glycol, n-propanol, and isopropanol, or a mixture of two or more in any proportion.

8. The method for preparing the gas wetting agent according to claim 3, characterized in that: The temperature for the full reaction in S2 is 70-90°C and the time is 2-4.5h.

9. The method for preparing the gas wetting agent according to claim 3, characterized in that: The end-capping in S3 is specifically as follows: after sufficient reaction for 0.5 to 2 hours, the system temperature is cooled to 25 to 45°C.

10. The method for preparing the gas wetting agent according to claim 3, characterized in that: The mass ratio of dispersion C to di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator in S4 is 100:(0.05-0.5), the reaction temperature is 75-85° C., and the reaction time is 3-5 h.

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