Dense sandstone reservoir gas-wetting agent and preparation method thereof

Abstract

This invention discloses a gas wetting agent suitable for tight sandstone reservoirs, comprising methacrylate monomers, fluorinated monomers, polymeric diols, diisocyanate compounds, sulfonate chain extenders, catalysts, end-capping monomers, and post-chain extenders. It also discloses a method for preparing the above-mentioned gas wetting agent, specifically: mixing methacrylate monomers and fluorinated monomers to obtain solution A; adding polymeric diols, diisocyanate compounds, sulfonate chain extenders, and catalysts to solution A and reacting to obtain solution B; adding end-capping monomers to solution B, followed by adding an aqueous solution of the post-chain extender to obtain dispersion C; adding di-tert-butylhydrogen peroxide-ferrous pyrophosphate to dispersion C, cooling, and then adding small-molecule alcohols to obtain the gas wetting agent. This invention is applicable to gas wetting agents for tight sandstone reservoirs and their preparation method. The prepared gas wetting agent has strong adsorption capacity and good dispersibility, and the preparation process is simple and energy-efficient.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of compact sandstone gas fracturing stimulation, and relates to a gas-wetting agent suitable for compact sandstone reservoirs, and also relates to a preparation method of the gas-wetting agent. BACKGROUND

[0002] The development of compact sandstone gas in China is developing rapidly, and has become the first focus of unconventional oil and gas resources. The source rock and reservoir of unconventional oil and gas resources both have the characteristics of low porosity and ultra-low permeability. Changing the wettability of shale layers can effectively improve the oil recovery.

[0003] Wetting phenomenon refers to the phenomenon that one fluid on the solid interface is replaced by another fluid. The wettability of oil reservoir rocks generally includes water-wetting, oil-wetting and neutral-wetting. Wettability refers to the tendency of a certain fluid to spread on the surface of a solid in the presence of other non-miscible fluids. In 2000, some researchers treated the solid with fluorine-containing surfactants to make the surface of the solid hydrophobic and oleophobic, and have amphiphobicity, so as to achieve the purpose of gas-wetting. The wettability of the rock surface is reversed from liquid-wetting to gas-wetting. The gas-wetting rock is neither water-wetting nor oil-wetting, and has good amphiphobicity. The treatment with fluorine-containing surfactants can reverse the wettability near the wellbore of the condensate gas reservoir from liquid-wetting to gas-wetting, can improve the flowability of the liquid phase in the reservoir, improve the relative permeability of the liquid phase, and ultimately improve the productivity of the gas well. The basic theoretical research on the gas-wetting of oil reservoir rocks has become a new research field in the petroleum industry and the colloid interface chemistry field, and is expected to become a new means of tertiary oil recovery. The mechanism of gas-wetting enhanced oil recovery is that the molecular film formed by the adsorption of fluorocarbon surfactants on the rock surface plays a role. The surfactant molecules are adsorbed on the surface of the core, the wettability of the core surface is reversed from liquid-wetting to gas-wetting, the seepage capacity of the liquid phase is enhanced, and the purpose of improving the recovery is achieved.

[0004] The fluorine-containing surfactant has the special performance of being both hydrophobic and oleophobic, and can realize gas-wetting. This is because the intermolecular condensation of the compound containing a large number of C-F bonds is small, so that the surface free energy is also reduced, forming a unique property that it is difficult for various liquids to wet and adhere. However, for compact sandstone reservoirs, the adsorption force of small molecule fluorocarbon surfactants is weak, and they are easily washed down by the liquid into the well, and cannot realize long-term effect. The perfluoro high molecular weight homopolymer has the problems of large molecular size, unable to enter the compact reservoir, or poor solubility and dispersibility, and poor stability, and cannot be used. SUMMARY

[0005] The purpose of the present application is to provide a gas-wetting agent suitable for compact sandstone reservoirs, which solves the problems of weak adsorption force, poor dispersibility and poor stability of the existing wetting agent.

[0006] Another purpose of the present application is to provide a preparation method of the gas-wetting agent.

[0007] The technical scheme adopted by the present application is that the gas wetting agent suitable for the compact sandstone reservoir is composed of a methacrylate monomer, a fluorine-containing monomer, a polymer diol, a diisocyanate compound, a sulfonate chain extender, a catalyst, an end-capping monomer and a post chain extender, the methacrylate monomer is 7-14 parts, the fluorine-containing monomer is 0.7-3.5 parts, the polymer diol is 3.3-5 parts, the diisocyanate compound is 10-13 parts, the sulfonate chain extender is 1.1-2.7 parts, the catalyst is 0.01-0.09 parts, the end-capping monomer is 1.5-6 parts and the post chain extender is 90-150 parts.

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

[0009] The methacrylate monomer is one, two or two or more kinds of arbitrary mixtures of hexyl methacrylate, n-octyl methacrylate and 2-ethylhexyl methacrylate;

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

[0011] The polymer diol is one or two kinds of arbitrary mixtures of polyhexamethylene adipate, polybutylene adipate, polycaprolactone diol, polycarbonate diol, polytetrahydrofuran diol, and the molecular weight is 1000-2000;

[0012] The diisocyanate compound is one or two kinds of arbitrary mixtures of dicyclohexyl methane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexyl methane diisocyanate, 1,4-cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate or cyclohexane dimethylene diisocyanate;

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

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

[0015] The end-capping monomer is one or two kinds of arbitrary mixtures 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-phenylacetic acid.

[0017] Another technical solution adopted by the present application is the preparation method of the gas wetting agent, which is implemented according to the following steps:

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

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

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

[0021] S4, adding a di-tert-butyl peroxide-ferrous pyrophosphate initiator into dispersion C to react and then to cool down, and then adding a small molecule alcohol to obtain a gas wetting agent suitable for a tight sandstone reservoir.

[0022] Another technical solution adopted by the present application is characterized in that:

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

[0024] The fluorine-containing monomer in S1 is one or a mixture of any ratio of two of trifluoroethyl acrylate, hexafluorobutyl acrylate, dodecafluoroheptyl acrylate, perfluorooctyl ethyl acrylate, nonadecafluoro acrylate, perfluorooctyl (N-methyl-N-acrylate ethyl) sulfonamide, perfluorooctyl (N-ethyl-N-acrylate ethyl) sulfonamide, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, nonadecafluoro acrylate, perfluorooctyl (N-methyl-N-methacrylate ethyl) sulfonamide or perfluorooctyl (N-ethyl-N-methacrylate ethyl) sulfonamide.

[0025] The polymer diol in S2 is one or a mixture of any ratio of two of polyhexamethylene adipate, polybutylene adipate, polycaprolactone diol, polycarbonate diol, polytetrahydrofuran diol, and the 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 a mixture of 1,2-dihydroxypropane sulfonic acid sodium, 2-aminoethyl amino ethyl sulfonic acid sodium, 2,4-diaminobenzenesulfonic acid sodium and 1,4-butanediol-2-sulfonic acid sodium in any proportion.

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

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

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

[0031] The small molecule alcohol in S4 is one or more of methanol, ethanol, ethylene glycol, n-propanol and isopropanol in any proportion.

[0032] The temperature for sufficient reaction in S2 is 70 to 90 DEG C, and the time is 2 to 4.5 hours.

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

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

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

[0036] (1) The present application is suitable for a dense sandstone reservoir gas-wetting agent and a preparation method thereof. In the synthesis process, a methacrylate monomer is used as a "similar solvent" to replace volatile organic solvents, and a sulfonate chain extender is used to replace traditional carboxyl-containing chain extenders, without using an amine neutralizer. The prepared fluorine-containing polyurethane emulsion does not release irritating ammonia odor and does not contain volatile organic compounds, and is a non-toxic, green and environmentally friendly polymer material.

[0037] (2) The present application is suitable for a gas-wetting agent for a tight sandstone reservoir and a preparation method thereof, and a fluorine-containing polyurethane can be solidified on the surface of a core base to form a hydrophobic and oleophobic film, the preparation method is simple, and operability is strong, the fluorine-containing polyurethane is solidified on the surface of the base material through immersion and drying, and has great compressive strength and strong hydrophobic and oleophobic properties.

[0038] (3) The present application is suitable for a gas-wetting agent for a tight sandstone reservoir and a preparation method thereof, on one hand, the polar end of the fluorine-containing polyurethane is adsorbed on the surface of a core with negative electricity, and the non-polar end of the molecular chain is oriented outward, due to the hydrophobic and oleophobic properties of fluorine atoms, the rock surface has neutral gas wetting, and the contact angle of water and oil phases on the rock surface is large; on the other hand, small molecule alcohols are added in the system, the alcohol is volatile, can carry liquid in the reservoir, and can form a mixed solution with water, thereby reducing the surface tension and capillary resistance, facilitating flowback, and relieving water lock damage.

[0039] (4) The present application is suitable for a gas-wetting agent for a tight sandstone reservoir and a preparation method thereof, the chain extender and the post-chain extender used are both sulfonate types, instead of traditional carboxylic acid type chain extenders, a neutralizing agent is not needed, and a fluorine-containing polyurethane emulsion with good dispersibility and stability can be obtained, the emulsion can be added with small molecule alcohols without breaking emulsion, has very good dispersibility, is beneficial to on-site liquid preparation and use, and the gas-wetting agent can successfully realize gas-wetting reverse of the surface of the tight sandstone, can effectively change the surface of the tight sandstone layer from liquid wetting to gas wetting, the preparation method is simple and easy to implement, and the yield of the tight sandstone gas well is significantly improved. DETAILED DESCRIPTION

[0040] The present application will be described in detail below in combination with specific embodiments.

[0041] The present application is suitable for a gas-wetting agent for a tight sandstone reservoir, which is composed of a methacrylate monomer, a fluorine-containing monomer, a polymer diol, a diisocyanate compound, a sulfonate chain extender, a catalyst, a capping monomer and a post-chain extender, the methacrylate monomer is 7-14 parts, the fluorine-containing monomer is 0.7-3.5 parts, the polymer diol is 3.3-5 parts, the diisocyanate compound is 10-13 parts, the sulfonate chain extender is 1.1-2.7 parts, the catalyst is 0.01-0.09 parts, the capping monomer is 1.5-6 parts, and the post-chain extender is 90-150 parts.

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

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

[0044] The polymeric diol is one of polyhexamethylene adipate, polybutylene adipate, polycaprolactone diol, polycarbonate diol, polytetrahydrofuran diol, or a mixture of any ratio of two of them, and the molecular weight is 1000-2000;

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

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

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

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

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

[0050] The application is suitable for the preparation method of the dense sandstone reservoir gas-wetting agent, and is specifically implemented according to the following steps:

[0051] S1, mixing 7-14 parts of a methacrylate monomer and 0.7-3.5 parts of a fluorine-containing monomer 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 any ratio of two or more of them;

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

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

[0055] The polymeric diol in S2 is one of polyhexamethylene adipate, polybutylene adipate, polycaprolactone diol, polycarbonate diol, polytetrahydrofuran diol, or a mixture of any ratio of two of them, and the molecular weight is 1000-2000;

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

[0057] The sulfonate chain extender in S2 is one of sodium 1,2-dihydroxypropane sulfonate, sodium 2-aminoethyl ethanesulfonate, sodium 2,4-diaminobenzenesulfonate, and sodium 1,4-butanediol-2-sulfonate, or a mixture of any ratio of two of them;

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

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

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

[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%-4%.

[0062] S4, adding a small molecule alcohol in the dispersion C after the reaction of the di-tert-butyl hydrogen peroxide-ferrous pyrophosphate initiator, then cooling, to obtain a gas-wetting agent suitable for tight sandstone reservoirs.

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

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

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

[0066] The mass ratio of the dispersion C and the di-tert-butyl hydrogen peroxide-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 hours.

[0067] Example 1

[0068] S1, mixing 7 parts of hexyl methacrylate and 1 part of hexafluorobutyl acrylate uniformly to obtain solution A;

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

[0070] S3, adding 1.5 parts of hydroxyethyl methacrylate in solution B for capping, after the sufficient reaction for 1 hour, cooling the temperature of the system to 30°C, adding 90 parts of a 0.5% mass concentration sodium ethylenediamine ethanesulfonate aqueous solution, and stirring for 21 minutes to disperse uniformly to obtain polyurethane dispersion C;

[0071] S4, adding a di-tert-butyl hydrogen peroxide-ferrous pyrophosphate initiator in the dispersion C, the mass ratio of the dispersion C and the di-tert-butyl hydrogen peroxide-ferrous pyrophosphate initiator is 100:0.46, and the reaction is carried out at 75°C for 5 hours to obtain an environmentally friendly fluorine-containing polyurethane emulsion, cooling, and adding 10 parts of methanol to obtain a gas-wetting agent suitable for tight sandstone reservoirs.

[0072] Example 2

[0073] S1, mixing 9 parts of n-octyl methacrylate and 1.5 parts of perfluoroalkyl (N-methyl-N-acrylate ethyl) sulfonamide uniformly to obtain solution A;

[0074] S2, 4.5 parts of polycaprolactone diol, 12 parts of isophorone diisocyanate, 1.8 parts of 2-aminoethyl amino ethanesulfonic acid sodium and 0.018 parts of dibutyl tin diacetate were added into solution A and reacted at 80℃ for 3.5 hours to obtain a polyurethane prepolymer solution B;

[0075] S3, 2.6 parts of hydroxypropyl methacrylate were added into solution B for capping, and after reacting for 1.2 hours, the system temperature was cooled to 28℃, 120 parts of 3% ethylenediamine sodium o-phenylacetate aqueous solution was added, and stirred for 19 minutes to disperse uniformly to obtain a polyurethane dispersion C;

[0076] S4, a di-tert-butyl peroxide-ferrous pyrophosphate initiator was added into dispersion C, the mass ratio of dispersion C and di-tert-butyl peroxide-ferrous pyrophosphate initiator was 100:0.3, and reacted at 80℃ for 4.5 hours to obtain an environmentally friendly fluorine-containing polyurethane emulsion, and then cooled, and 15 parts of ethanol was added to obtain a gas-wetting agent suitable for tight sandstone reservoirs.

[0077] Example 3

[0078] S1, 11 parts of 2-ethylhexyl methacrylate and 2.5 parts of perfluoro octyl (N-ethyl-N-acrylate ethyl) sulfonamide were uniformly mixed to obtain solution A;

[0079] S2, 5 parts of polyhexanediol adipate, 12.5 parts of hexamethylene diisocyanate, 2.1 parts of 2,4-diamino benzene sulfonic acid sodium and 0.021 parts of stannous octoate were added into solution A and reacted at 85℃ for 2 hours to obtain a polyurethane prepolymer solution B;

[0080] S3, 2.9 parts of hydroxypropyl acrylate capping monomer were added into solution B for capping, and after reacting for 1 hour, the system temperature was cooled to 35℃, 130 parts of 2% ethylenediamine sodium o-phenylacetate aqueous solution was added, and stirred for 22 minutes to disperse uniformly to obtain a polyurethane dispersion C;

[0081] S4, a di-tert-butyl peroxide-ferrous pyrophosphate initiator was added into dispersion C, the mass ratio of dispersion C and di-tert-butyl peroxide-ferrous pyrophosphate initiator was 100:0.5, and reacted at 83℃ for 4 hours to obtain an environmentally friendly fluorine-containing polyurethane emulsion, and then cooled, and 24 parts of ethylene glycol was added to obtain a gas-wetting agent suitable for tight sandstone reservoirs.

[0082] Example 4

[0083] S1, 12.5 parts of hexyl methacrylate and 3 parts of hexafluorobutyl methacrylate were uniformly mixed to obtain solution A;

[0084] S2, 4.6 parts of polybutylene adipate, 13 parts of dicyclohexyl methane diisocyanate, 2.4 parts of 1,4-butanediol-2-sulfonic acid sodium and 0.039 parts of dibutyl tin diacetate were added into solution A and reacted at 75℃ for 4 hours to obtain polyurethane prepolymer solution B;

[0085] S3, 3 parts of hydroxymethyl acrylamide were added into solution B for end-capping, and after reacting for 1.5 hours, the system was cooled to 30℃, 118 parts of 0.9% mass concentration of ethylenediamine ethanesulfonic acid sodium aqueous solution was added and stirred for 26 minutes to disperse uniformly to obtain polyurethane dispersion C;

[0086] S4, a di-tert-butyl peroxide-ferrous pyrophosphate initiator was added into dispersion C, the mass ratio of dispersion C and di-tert-butyl peroxide-ferrous pyrophosphate initiator was 100:0.09, and the reaction was carried out at 85℃ for 3 hours to obtain the environmentally friendly fluorine-containing polyurethane emulsion, and then 18 parts of n-propanol was added to obtain the gas-wetting agent suitable for tight sandstone reservoirs.

[0087] Example 5

[0088] S1, 13 parts of n-octyl methacrylate and 2.5 parts of dodecafluoroheptyl methacrylate were uniformly mixed to obtain solution A;

[0089] S2, 4.7 parts of polycarbonate diol, 12.5 parts of 1,4-cyclohexane diisocyanate, 1.7 parts of 2,4-diaminobenzenesulfonic acid sodium and 0.02 parts of dibutyl tin dilaurate were added into solution A and reacted at 79℃ for 3 hours to obtain polyurethane prepolymer solution B;

[0090] S3, 1.9 parts of hydroxybutyl acrylate end-capping monomer was added into solution B for end-capping, and after reacting for 0.5 hours, the system was cooled to 45℃, 136 parts of 2.5% mass concentration of ethylenediamine di-o-phenylacetic acid sodium aqueous solution was added and stirred for 25 minutes to disperse uniformly to obtain polyurethane dispersion C;

[0091] S4, a di-tert-butyl peroxide-ferrous pyrophosphate initiator was added into dispersion C, the mass ratio of dispersion C and di-tert-butyl peroxide-ferrous pyrophosphate initiator was 100:0.21, and the reaction was carried out at 75℃ for 3.5 hours to obtain the environmentally friendly fluorine-containing polyurethane emulsion, and then 20 parts of isopropanol was added to obtain the gas-wetting agent suitable for tight sandstone reservoirs.

[0092] 1. Performance test:

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

[0094] Table 1 Contact angle of water phase and oil phase in gas-liquid-solid system

[0095]

[0096] The contact angles of water phase and oil phase on the untreated core surface are 25 DEG and 0 DEG respectively, and the contact angles of the two phases are less than 90 DEG, and the wettability of the core surface is liquid wet. The core is treated with 0.5% wetting agent solution respectively, and the contact angles of water phase and oil phase on the core surface are measured. Compared with the contact angles of the untreated core surface, the contact angles of water phase and oil phase on the treated core surface are obviously increased, and the contact angles of water phase and oil phase are increased from 25 DEG and 0 DEG of the untreated core to 121 DEG and 61 DEG, 121 DEG and 63 DEG, 123 DEG and 70 DEG, 134 DEG and 67 DEG and 131 DEG and 62 DEG, which shows that the gas-wetting agent has good gas-wetting reverse effect. After being treated with the gas-wetting agent prepared by the application, the hydrophobicity and oleophobicity of the rock surface are obviously increased, the contact area of water phase on the core surface is smaller, the viscous resistance of flow is smaller, and the flow is easier, so that the flow condition of fluid in porous medium is effectively improved, and the water lock effect is solved.

[0097] 2, gas displacement rate test: a certain mass of proppant or mixture of proppant and core powder 1:1 is filled into a dry vertical chromatographic column, weighed and recorded as m1, water / 0.5% gas well wetting improver is added to the chromatographic column until the chromatographic column is saturated, and then 10min is waited, weighed and recorded as m2. The chromatographic column is placed horizontally, one side is connected with nitrogen gas with a pressure of 10KPa, and the other side is connected with a constant weight conical flask to collect the displaced liquid, and the mass of the outflow liquid is recorded as m3 after 5min, then the displacement rate=m3 / (m2-m1)*100%. The displacement rate test results of example 2 are shown in Table 2:

[0098] Table 2 Displacement rate test results

[0099]

[0100] In summary, the application is suitable for the preparation method of the gas-wetting agent for dense sandstone reservoir, the preparation process is simple, the energy consumption is small, and the stability is strong. The gas-wetting agent prepared by the method can successfully realize the gas-wetting reverse of the surface of the dense sandstone, can effectively change the surface of the dense sandstone layer from liquid wettability to gas wettability, the preparation method is simple and easy to operate, and the yield of the dense sandstone gas well is significantly improved.

Claims

1. A method for preparing an air wetting agent suitable for tight sandstone reservoirs, characterized in that, The specific steps are as follows: S1. Mix 7-14 parts of methacrylate monomers and 0.7-3.5 parts of fluorine-containing monomers to obtain solution A; S2. Add 3.3-5 parts of polymeric 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 and react fully to obtain polyurethane prepolymer solution B; S3. Add 1.5 to 6 parts of the end-capping monomer to solution B for end-capping, then add 90 to 150 parts of the aqueous solution of the chain extender and stir for 15 to 30 minutes to obtain polyurethane dispersion C. S4. After adding di-tert-butyl hydrogen peroxide-ferrous pyrophosphate initiator to dispersion C and reacting, the mixture is cooled and then small molecule alcohols are added to obtain an air wetting agent suitable for tight sandstone reservoirs. The fluorinated monomer in S1 is trifluoroethyl acrylate, hexafluorobutyl acrylate, dodecylfluoroheptyl acrylate, perfluorooctyl ethyl acrylate, nonadecanofluoro acrylate, perfluorooctyl (N-methyl-N-ethyl acrylate) sulfonamide, perfluorooctyl (N-ethyl-N-ethyl acrylate) sulfonamide, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecylfluoroheptyl methacrylate, nonadecanofluoro methacrylate, perfluorooctyl (N-methyl-N-ethyl methacrylate) sulfonamide, or perfluorooctyl (N-ethyl-N-ethyl methacrylate) sulfonamide; The end-capping monomer in S3 is one or a mixture of two of the following in any proportion: hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, and hydroxymethylacrylamide. The chain extender in S3 is sodium ethylenediamine ethanesulfonate or sodium ethylenediamine di-o-phenylacetate. The polymer diol mentioned in S2 is one or a mixture of two of the following in any proportion: polyhexanediol adipate, polybutylene adipate, polycaprolactone diol, polycarbonate diol, and polytetrahydrofuran diol.

2. The method for preparing the gas wetting agent suitable for tight sandstone reservoirs according to claim 1, characterized in that, The methacrylate monomer in S1 is one, two, or a mixture of two or more of the following in any proportion: hexyl methacrylate, n-octyl methacrylate, and 2-ethylhexyl methacrylate.

3. The method for preparing the gas wetting agent suitable for tight sandstone reservoirs according to claim 1, characterized in that, The molecular weight of the polymer diol in S2 is between 1000 and 2000. The diisocyanate compound in S2 is dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 1,4-cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, or cyclohexane diisocyanate. The sulfonate chain extender in S2 is one or a mixture of two of the following in any proportion: sodium 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.

4. The method for preparing the gas wetting agent suitable for tight sandstone reservoirs according to claim 1, characterized in that, The mass concentration of the aqueous solution of the post-chain extender is 0.5% to 4%.

5. The method for preparing the gas wetting agent suitable for tight sandstone reservoirs according to claim 1, characterized in that, 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.

6. The method for preparing the gas wetting agent suitable for tight sandstone reservoirs according to claim 1, characterized in that, The temperature for a complete reaction in S2 is 70~90℃, and the time is 2~4.5h.

7. The method for preparing the gas wetting agent suitable for tight sandstone reservoirs according to claim 1, characterized in that, The end-capping process in S3 specifically involves cooling the system temperature to 25-45°C after a full reaction of 0.5-2 hours.

8. The method for preparing the gas wetting agent suitable for tight sandstone reservoirs according to claim 1, characterized in that, In the S4 reaction, the mass ratio of dispersion C to di-tert-butyl hydroperoxide-ferrous pyrophosphate initiator is 100:(0.05~0.5), the reaction temperature is 75~85℃, and the reaction time is 3~5h.

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