Micro-emulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability reservoir and preparation method of micro-emulsion viscoelastic self-regulating oil displacement agent

Abstract

The invention discloses an ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent and a preparation method thereof, the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent comprises the following components by weight: 10-15% of a micellar agent, 15-20% of an emulsifier, 4-6% of a cosurfactant, 10-15% of a regulating agent, 15-20% of a solubilizer, 3-5% of a reinforcing agent, and the balance of deionized water. The problems that the starting pressure gradient of the ultra-low permeability reservoir is high, the water drive efficiency is low, the oil drive efficiency is poor, the pressure space of a ground water injection system is limited, and the plane and longitudinal contradiction of the ultra-low permeability reservoir is intensified due to partial reservoir development microcracks are solved, and integrated operation of pressure reduction and injection increase, profile control, oil drive and extraction of the low permeability reservoir is achieved; and the formation energy of a well group is maintained, the natural declining rate of the oil reservoir is reduced, and a favorable way is provided for efficient utilization, rapid development and long-acting treatment of the ultra-low permeability oil reservoir.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield development, relates to the technical field of self-regulated oil displacement, production increase and stable production in ultra-low permeability reservoirs, and specifically relates to an ultra-low permeability reservoir microemulsion viscoelastic self-regulated oil displacement agent and a preparation method thereof. Background Art

[0003] Although good production results have been achieved in the water flooding development of ultra-low permeability reservoirs, it is difficult to establish an effective pressure displacement system in some ultra-low permeability reservoir well groups due to the tight geological conditions. There are many water wells with high pressure underinjection, and the formation pressure of oil wells is kept below 90%. The initial annual decline is large, reaching 25-50%. Some ultra-low permeability reservoir well groups have poor fracture network matching, rapid water rise, and low overall water flooding efficiency. The production and development of ultra-low permeability reservoirs show a low degree of water flooding in the oil field. In order to improve the degree of water flooding in ultra-low permeability reservoirs, the main domestic methods include surfactant flooding, polymer microsphere flooding, air foam flooding and carbon dioxide flooding. Surfactant flooding mainly uses sulfonate and sulfate surfactants to reduce the oil-water interfacial tension and improve the water flooding recovery rate. However, the permeability of the tight reservoir of ultra-low permeability reservoirs is large, and the lateral residual oil utilization is limited. Air foam flooding and carbon dioxide flooding mainly use gas media to increase the formation energy of the well group. Affected by the previous fracturing transformation channel, gas channeling is serious after a certain period of gas drive production, affecting the production capacity of the well group. Polymer microsphere flooding uses large doses and low concentrations of nano- or micron-sized polymer materials to plug the front micro-fractures in the water drive channel of ultra-low permeability reservoirs, and through multiple rounds of plugging and pressure increase, it forces the later water injection to bypass and expand the water drive affected area, which plays a key role in improving the recovery rate of ultra-low permeability reservoirs. However, the polymer microsphere flooding working fluid has increased water injection pressure and limited flooding pressure space in ultra-low permeability reservoirs after multiple rounds of flooding, and has weak lateral residual oil absorption, permeation, and oil washing capabilities, and the recovery rate is decreasing year by year. Therefore, for the purpose of improving the recovery rate of ultra-low permeability oilfields through water flooding, an oil displacement agent with strong absorption, permeation, and oil washing capabilities, and the ability to self-regulate fluid viscosity and particle size changes, can solve the above problems in a targeted manner, realize the integration of pressure reduction and injection, profile adjustment, oil displacement, and production enhancement in ultra-low permeability reservoirs, and provide a favorable method for efficient use, rapid development, and long-term management of ultra-low permeability reservoirs.

[0004] China Patent Publication (Announcement) No. CN113604209A, November 5, 2021, discloses an online-produced nano-composite viscoelastic oil-displacing agent, relates to the technical field of viscoelastic oil-displacing agents, and provides an online-produced nano-composite oil-displacing agent, which comprises, by weight percentage: 0.05% to 0.8% of a surfactant, and a balance of water; wherein the surfactant comprises erucic acid amidopropyl hydroxysulfobetaine, or erucic acid amidopropyl betaine, hexadecyl amidopropyl hydroxypropyl sulfobetaine, and tetradecyl propyl sulfobetaine. The composite oil-displacing agent of the present invention may also include at least one of tetradecyl amidopropyl hydroxypropyl sulfobetaine and hexadecyl propyl sulfobetaine, and / or, nano-silicon dioxide having a content not exceeding 0.05%, and / or, sodium dodecylbenzene sulfonate having a content not exceeding 0.03%, and / or, 0.05% to 0.1% of polyether diamine and 0.05% to 0.1% of salicylic acid. For oil reservoirs with different mineralization and permeability, the viscosity and interfacial tension of the nanocomposite viscoelastic oil displacement agent of the present invention are controllable in the oil layer; the inorganic ions in the water injected into the formation are fully utilized while ensuring online injection. China Patent Publication (Announcement) No. CN115926204A, April 7, 2023, discloses a thermosensitive spherical shell permeability self-regulating polymer microsphere and preparation method, which relates to the technical field of polymer microspheres and preparation methods, and discloses a thermosensitive spherical shell permeability self-regulating polymer microsphere and preparation method, specifically, thermosensitive bidirectional shape memory nanoparticles are compounded in the spherical shell to act as a "micro switch", and the shrinkage / recovery effect generated by the response to temperature rise / fall is used to increase / decrease the pore size in the spherical shell, thereby regulating the permeability of the spherical shell. In this way, the pore size of the spherical shell can be increased without destroying the spherical shell structure to improve the water vapor permeability during high-temperature drying and accelerate the escape rate of water in the microsphere kernel; the pore size of the spherical shell is reduced under normal temperature after drying, ensuring the mechanical properties and optical properties required for the application of core-shell polymer microspheres. The present invention can significantly improve the drying efficiency of water-containing core-shell polymer microspheres and assist in the high-throughput manufacturing of polymer hollow microspheres. China Patent Publication (Announcement) No. CN115340857A, November 15, 2022, discloses an in-situ self-emulsifying nano oil-displacing agent and its preparation method and application, which relates to the technical field of nano oil-displacing agents and their preparation methods and applications, and discloses an in-situ self-emulsifying nano oil-displacing agent and its preparation method and application. It includes hyperbranched nanomaterials, polymerized AOS and anionic surfactants; wherein the mass fraction of hyperbranched nanomaterials is 7-10wt%; the mass fraction of polymerized AOS is 20-30wt%; the mass fraction of anionic surfactants is 10-20wt%; the rest is water.The in-situ emulsified nano oil-displacing agent of the present application has low concentration, good emulsification effect, and interfacial tension can reach 10-2mN / m; it has a wide temperature resistance range, and can be applied to the temperature range of 30-120℃, has good stability, no stratification, no precipitation, and good salt resistance; after aging at 120℃ for 8h, the emulsification solubilization rate and interfacial tension do not change significantly, and the temperature resistance is good. No demulsifier is required, and dehydration can be achieved by standing, achieving the good effect of "emulsification at touch and dehydration at stop".

[0005] Represented by the above patents, viscoelastic oil displacement agents and emulsified nano oil displacement agents use surfactants to emulsify crude oil and injected water to reduce the oil-water interfacial tension, introduce nano-silica or hyperbranched nanomaterials to form nanofluids from their liquids, and expand the contact surface and adsorption capacity of the oil displacement agent on the rock surface to extend the effective period of oil displacement. Self-regulating polymer microsphere displacement materials mainly use nano- or micron-sized polymer molecular clusters to slowly expand in the formation to block the water drive channels of the early old fractures. According to different expansion multiples, they self-regulate and block fractures of different widths, forcing the water drive flow direction to change and improving the recovery rate of the remaining oil in the reservoir. This type of invention patent products and technologies play an important role in improving the recovery rate of water drive and maintaining the efficient development of low-permeability oil fields. In ultra-low permeability reservoirs, the rock matrix has low permeability and is denser, and the median radius of the reservoir pores is only 200-300nm. Although the particle size of solid-phase nanomaterial oil-displacing agents is as small as 20-50nm, the adsorption specific surface efficiency of nanomaterials is a double-edged sword. It is difficult to achieve single-layer adsorption of high-efficiency nanomaterials in rock pores. Long-term injection of such oil-displacing agents at low concentrations is prone to adsorption, aggregation, and clogging of pore throats, causing high-pressure under-injection in deep water wells, which brings great difficulties to the next step of injection measures. The water flooding start-up pressure gradient of ultra-low permeability reservoirs is high, and it is very difficult to displace the injected water in the matrix alone. It is difficult for 50nm or 100nm polymer microsphere flooding materials to circulate in the matrix in the injected water. When the polymer microsphere flooding materials swell when exposed to water, they can hardly enter the pore throats of the ultra-low permeability reservoir rocks, and their ability to displace the remaining oil in the lateral matrix of the well group is limited. This material only expands from low permeability reservoirs to ultra-low permeability reservoirs. The ability of simple polymers and injected water to wash oil from rocks is weak. This is one of the reasons why the rate of increase in the recovery rate of polymer microsphere flooding in ultra-low permeability reservoirs has decreased year by year in the early stage. In order to improve the recovery rate of denser ultra-low permeability reservoirs, it is necessary to solve the problems of high starting pressure gradient, low water drive efficiency, poor oil recovery efficiency, and limited pressure space of the ground water injection system in denser ultra-low permeability reservoirs. In addition, some reservoirs develop microcracks, which lead to aggravated horizontal and vertical contradictions in ultra-low permeability reservoirs. Therefore, it is necessary to develop an oil recovery working fluid that can better solve the above problems, realize the integration of pressure reduction and injection increase, profile adjustment, oil recovery, and production enhancement in ultra-low permeability reservoirs, maintain the formation energy of the well group, and facilitate the efficient development of ultra-low permeability reservoirs. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of high starting pressure gradient, low water drive efficiency, poor oil recovery efficiency, limited pressure space of surface water injection system, and aggravated plane and vertical contradictions of ultra-low permeability reservoirs caused by microcracks in some reservoirs, so as to realize the integrated operation of pressure reduction and injection, profile adjustment, oil recovery, and oil recovery in low permeability reservoirs, maintain the formation energy of the well group, reduce the natural decline rate of the reservoir, and provide a favorable way for efficient use, rapid development, and long-term management of ultra-low permeability reservoirs. The present invention provides a formula and preparation method of a microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability reservoirs.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability oil reservoirs, comprising the following components by weight percentage: Micellar agent 10-15%, Emulsifier 15-20%, Co-surfactant 4-6%, Regulator 10-15%, Solubilizer 15-20%, Enhancer 3-5%, The balance was deionized water.

[0008] Furthermore, the micellar agent is composed of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and oleamidopropyl dimethylamine, wherein the weight percentage content of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate is 55-77%, and the weight percentage content of oleamidopropyl dimethylamine is 23-45%.

[0009] Furthermore, the emulsifier is composed of styrylphenol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether and styrylphenol polyoxyethylene ether, wherein the weight percentage content of styrylphenol polyoxyethylene ether is 52-70%, the weight percentage content of isomeric tridecanol polyoxyethylene ether is 25-35%, and the weight percentage content of isomeric decanol polyoxyethylene polyoxypropylene ether is 5-13%.

[0010] Furthermore, the co-surfactant is didodecyl methyl hydroxypropyl sulfobetaine.

[0011] Furthermore, the regulating agent is one or more components of α-pyrene or β-pyrene.

[0012] Furthermore, the solubilizing agent is N'N-dimethylacetamide or N'N-dimethylformamide, or a mixture of the two.

[0013] Furthermore, the enhancer is composed of potassium chloride and potassium hydroxide, wherein the weight percentage of potassium chloride is 50-75%, and the weight percentage of potassium hydroxide is 25-50%.

[0014] A method for preparing a microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability oil reservoirs comprises the following steps: First, add 15-20% by weight of a solubilizer into a reactor, heat the reactor to 40-50°C, and start stirring at a stirring speed of 50-60r / min; then add 15-20% by weight of an emulsifier, stir until all solids are completely dissolved; then add 10-15% by weight of a regulator, and control the drop-adding time to be 40-60min; then mix 3-5% by weight of an enhancer and 21-41% by weight of deionized water to obtain an enhancer solution, add the enhancer solution into the reactor under stirring conditions, and control the drop-adding time to be 40-60min; then add 10-15% by weight of a micellar agent, and stir for 10-20min; finally add 4-6% by weight of a co-surfactant, stir for 20-30min, cool to room temperature and discharge, and obtain an ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent product.

[0015] Further, the micellar agent is composed of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and oleamidopropyl dimethylamine; The emulsifier is composed of styrylphenol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether and; The co-surfactant is didodecyl methyl hydroxypropyl sulfobetaine; The regulating agent is α-peneline or β-peneline; The solubilizing agent is one of N'N-dimethylacetamide or N'N-dimethylformamide or a mixture of the two; The enhancer consists of potassium chloride and potassium hydroxide.

[0016] Furthermore, the method for preparing the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent comprises the following steps: S1, firstly, add 15-20% by weight of N'N-dimethylacetamide or N'N-dimethylformamide or a mixture of the two into a reaction kettle, heat the reaction kettle to 40-50° C., and start stirring at a stirring speed of 50-60 r / min; S2, then add 9-12% by weight of styrylphenol polyoxyethylene ether, 5-6% by weight of isotridecyl alcohol polyoxyethylene ether and 1-2% by weight of isodecyl alcohol polyoxyethylene polyoxypropylene ether, and stir at a stirring speed of 100-120 r / min for 10-20 min until all the solids are completely dissolved; S3, then add 10-15% by weight of α-pyrene or β-pyrene or a mixture thereof, and control the dropping time to be 40-60 min; S4, 2-3% by weight of potassium chloride, 1-2% by weight of potassium hydroxide and 21-41% by weight of deionized water are uniformly mixed to obtain an enhancer solution, and the enhancer solution is added to the reactor under stirring conditions of 100-120 r / min, and the dropping time is controlled to be 40-60 min; S5, under stirring condition of 50-60r / min, add 7-10 weight percent of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and 3-5 weight percent of oleamidopropyl dimethylamine, and stir for 10-20min; S6, finally add 4-6% by weight of didodecyl methyl hydroxypropyl sulfobetaine, stir for 20-30 minutes, cool to room temperature and discharge to obtain the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent product.

[0017] Compared with the prior art, the advantages of the present invention are as follows: 1. The microemulsion viscoelastic self-regulating oil displacement agent in ultra-low permeability reservoirs uses the viscoelastic characteristics of surfactants to automatically adjust and displace in the water drive channel, forcing the oil displacement agent to enter the high oil saturation or residual oil enriched area to improve the oil displacement efficiency of the oil displacement agent. Octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate, oleamidopropyl dimethylamine and didodecyl methyl hydroxypropyl sulfobetaine in the microemulsion viscoelastic self-regulating oil displacement agent will form large and small energy-replenishing micelles in the potassium chloride solution, which have good viscoelasticity. When encountering high-mineralization formation water in the formation (preliminary water drive dominant channel), the viscosity will increase accordingly, and the water drive flow resistance will increase, forcing the oil displacement agent solution to flow in other directions. When the microemulsion viscoelastic self-regulating oil displacement agent encounters a high oil saturation or residual oil enriched area, the formation water crude oil causes the oil displacement agent viscoelastic micelles to reduce viscosity and break the gel, the viscosity decreases, and the water drive flow resistance decreases, expanding the swept area and oil displacement efficiency of the oil displacement agent in the high oil saturation or residual oil enriched area.

[0018] 2. The microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability reservoirs nanosizes the injected water molecules, further improving the penetration of the oil displacement agent in the low-pore fine throat of the ultra-low permeability reservoir, and promoting the pressure reduction and injection of water wells. The microemulsion viscoelastic self-regulating oil displacement agent does not contain any solid-phase nanomaterials. It is mainly composed of styrylphenol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether and isomeric decanol polyoxyethylene polyoxypropylene ether and α-piperene (β-piperene) under the action of N'N-dimethylformamide to form a nano-scale microemulsion, which improves the permeability and penetration of the injected water. When mixed with the injected water, it will not block the pore throat of the ultra-low permeability reservoir due to the multi-layer adsorption of solid-phase nanomaterials, resulting in high-pressure under-injection of the water well. Instead, it can use the small particle size effect of the microemulsion to reduce the capillary resistance of the fine throat of the water drive channel in the ultra-low permeability reservoir matrix, thereby reducing the injection pressure and realizing the integrated function of oil displacement-pressure reduction and injection.

[0019] 3. The microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability reservoirs nanosizes the injected water molecules, so that the injected water containing the oil displacement agent has an improved oil-water permeation and replacement capacity in the ultra-low permeability reservoir matrix, promotes the aggregation and replacement of the remaining oil, and is conducive to improving the overall crude oil recovery rate in the matrix. Emulsifiers such as styrylphenol polyoxyethylene ether and pyrene form nano-scale microemulsions under the action of N'N-dimethylformamide. Under the support of potassium chloride and potassium hydroxide salts and surfactants, the heavy organic components on the pore walls of the matrix are mutually dissolved and cleaned, so that the nano-scale microemulsion has an enhanced ability to replace crude oil, and part of the oil in the small pores is replaced and displaced. The imbibed and displaced crude oil is aggregated into a mass through nano-emulsification. With the increase of time, the oil droplets inside the core of the ultra-low permeability reservoir gradually increase and become dense. The denser the oil, the more obvious the oil production, forming displaceable crude oil droplets. This is more efficient than conventional surfactants in the recovery and utilization of crude oil in the small pores of the ultra-low permeability reservoir matrix, which is conducive to the further use of the remaining oil.

[0020] 4. The microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability reservoirs has the integrated functions of pressure reduction, injection enhancement, profile control, oil displacement, and production enhancement. The microemulsion viscoelastic self-regulating oil displacement agent uses the small particle size, multi-scale and high specific surface area of ​​the microemulsion to penetrate and absorb in the small pores of the matrix. The micelle agent forms a viscoelastic surfactant to control the flow direction of water drive. The regulator and solubilizer dissolve the high-carbon chain organic matter. The auxiliary surfactant improves the oil displacement capacity under the action of potassium hydroxide and micelle agent. It can achieve multi-functional integration under the water drive pressure of the well group, combining water well injection enhancement, production enhancement with profile control and oil displacement to achieve a multi-effect function of one agent, maintain the formation energy of the well group, reduce the natural decline rate of the reservoir, and maintain the efficient use and rapid development of ultra-low permeability reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0022] Figure 1 This is a test result diagram of the imbibition time and imbibition volume of ultra-low permeability reservoirs in different media; Figure 2 Schematic diagram of the test results of viscoelastic indicators of microemulsion viscoelastic self-regulating oil displacement agent in ultra-low permeability reservoirs. DETAILED DESCRIPTION

[0023] The content of the present invention can be further understood by combining the following detailed description of the preferred implementation method of the present invention and the embodiments included. Unless otherwise stated, all technical and scientific terms used in this article have the same meaning as those of ordinary skill in the art to which the present invention belongs. If the definition of a specific term disclosed in the prior art is inconsistent with any definition provided in the present invention, the definition of the term provided in the present invention shall prevail.

[0024] The present invention relates to an ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent, which comprises the following components by weight percentage: Micellar agent 10-15%, Emulsifier 15-20%, Co-surfactant 4-6%, Regulator 10-15%, Solubilizer 15-20%, Enhancer 3-5%, The balance was deionized water.

[0025] Furthermore, the micellar agent is composed of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and oleamidopropyl dimethylamine, wherein the weight percentage content of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate is 55-77%, and the weight percentage content of oleamidopropyl dimethylamine is 23-45%.

[0026] Furthermore, the emulsifier is composed of styrylphenol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether and styrylphenol polyoxyethylene ether, wherein the weight percentage content of styrylphenol polyoxyethylene ether is 52-70%, the weight percentage content of isomeric tridecanol polyoxyethylene ether is 25-35%, and the weight percentage content of isomeric decanol polyoxyethylene polyoxypropylene ether is 5-13%.

[0027] Furthermore, the co-surfactant is didodecyl methyl hydroxypropyl sulfobetaine.

[0028] Furthermore, the regulating agent is one or more components of α-pyrene or β-pyrene.

[0029] Furthermore, the solubilizing agent is N'N-dimethylacetamide or N'N-dimethylformamide, or a mixture of the two.

[0030] Furthermore, the enhancer is composed of potassium chloride and potassium hydroxide, wherein the weight percentage of potassium chloride is 50-75%, and the weight percentage of potassium hydroxide is 25-50%.

[0031] The present invention also provides a method for preparing a microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability oil reservoirs, comprising the following steps: First, add 15-20% by weight of a solubilizer into a reactor, heat the reactor to 40-50°C, and start stirring at a stirring speed of 50-60r / min; then add 15-20% by weight of an emulsifier, stir until all solids are completely dissolved; then add 10-15% by weight of a regulator, and control the drop-adding time to be 40-60min; then mix 3-5% by weight of an enhancer and 21-41% by weight of deionized water to obtain an enhancer solution, add the enhancer solution into the reactor under stirring conditions, and control the drop-adding time to be 40-60min; then add 10-15% by weight of a micellar agent, and stir for 10-20min; finally add 4-6% by weight of a co-surfactant, stir for 20-30min, cool to room temperature and discharge, and obtain an ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent product.

[0032] Preferably, the micellar agent is composed of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and oleamidopropyl dimethylamine; the emulsifier is composed of styrylphenol polyoxyethylene ether, isomeric tridecyl alcohol polyoxyethylene ether and; the co-surfactant is didodecyl methyl hydroxypropyl sulfobetaine; the regulating agent is one of α-peneline or β-peneline or a mixture thereof; the solubilizer is one of N'N-dimethylacetamide or N'N-dimethylformamide or a mixture of the two; the enhancer is composed of potassium chloride and potassium hydroxide.

[0033] Furthermore, the method for preparing the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent comprises the following steps: S1, firstly, add 15-20% by weight of N'N-dimethylacetamide or N'N-dimethylformamide or a mixture of the two into a reaction kettle, heat the reaction kettle to 40-50° C., and start stirring at a stirring speed of 50-60 r / min; S2, then add 9-12% by weight of styrylphenol polyoxyethylene ether, 5-6% by weight of isotridecyl alcohol polyoxyethylene ether and 1-2% by weight of isodecyl alcohol polyoxyethylene polyoxypropylene ether, and stir at a stirring speed of 100-120 r / min for 10-20 min until all the solids are completely dissolved; S3, then add 10-15% by weight of α-pyrene or β-pyrene or a mixture thereof, and control the dropping time to be 40-60 min; S4, 2-3% by weight of potassium chloride, 1-2% by weight of potassium hydroxide and 21-41% by weight of deionized water are uniformly mixed to obtain an enhancer solution, and the enhancer solution is added to the reactor under stirring conditions of 100-120 r / min, and the dropping time is controlled to be 40-60 min; S5, under stirring condition of 50-60r / min, add 7-10 weight percent of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and 3-5 weight percent of oleamidopropyl dimethylamine, and stir for 10-20min; S6, finally add 4-6% by weight of didodecyl methyl hydroxypropyl sulfobetaine, stir for 20-30 minutes, cool to room temperature and discharge to obtain the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent product.

[0034] Embodiment 1: The present invention discloses a microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability oil reservoirs, which comprises, by weight percentage: 10% octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate, 5% oleamidopropyl dimethylamine, 9% styrylphenol polyoxyethylene ether, 5% isomeric tridecyl alcohol polyoxyethylene ether, 1% isomeric decanol polyoxyethylene polyoxypropylene ether, 15% N'N-dimethylacetamide, 4% didodecyl methyl hydroxypropyl sulfobetaine, 15% α-pyrene, 3% potassium chloride, 2% potassium hydroxide and 31% deionized water.

[0035] The preparation method of the above-mentioned ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent is as follows: First, add 15% N'N-dimethylacetamide to the reactor, heat the reactor to 50°C, and start stirring at a stirring speed of 50r / min; then add 9% styrylphenol polyoxyethylene ether, 5% isotridecyl alcohol polyoxyethylene ether and 1% isotridecyl alcohol polyoxyethylene polyoxypropylene ether, and stir for 10 minutes until all the solids are completely dissolved; adjust the stirring speed to 120r / min, slowly and evenly add 15% α-pyrene, control the addition time to 40min, and continue stirring for 30min; dissolve 3% potassium chloride and 2% potassium hydroxide in 31 % deionized water, stir until all the solids are completely dissolved to obtain an enhancer solution, slowly and evenly add the enhancer solution into the reactor, the dropping time is controlled at 40min, and the stirring speed is 100r / min; adjust the stirring speed to 50r / min again, add 10% octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and 5% oleamidopropyl dimethylamine, and stir for 10min; add 4% didodecyl methyl hydroxypropyl sulfobetaine, stir for 30min, cool to room temperature and discharge, thus producing a microemulsion viscoelastic self-regulating oil displacement agent product for ultra-low permeability reservoirs.

[0036] Embodiment 2: The invention discloses a microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability oil reservoirs. The microemulsion viscoelastic self-regulating oil displacement agent comprises, by weight percentage: 10% of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate, 5% of oleamidopropyl dimethylamine, 12% of styrylphenol polyoxyethylene ether, 6% of isomeric tridecanol polyoxyethylene ether, 2% of isomeric decanol polyoxyethylene polyoxypropylene ether; 20% of solubilizer N'N-dimethylacetamide; 4% of auxiliary surfactant didodecyl methyl hydroxypropyl sulfobetaine; 10% of regulating agent α-pyrene; 3% of potassium chloride, 2% of potassium hydroxide and 26% of deionized water.

[0037] The preparation method of the above-mentioned ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent is as follows: First, add 20% N'N-dimethylacetamide to the reactor, heat the reactor to 40°C, and start stirring at a stirring speed of 60r / min; then add 12% styrylphenol polyoxyethylene ether, 6% isotridecyl alcohol polyoxyethylene ether and 2% isotridecyl alcohol polyoxyethylene polyoxypropylene ether, and stir for 20 minutes until all the solids are completely dissolved; adjust the stirring speed to 100r / min, slowly and evenly add 10% α-pyrene, control the addition time to 60min, and continue stirring for 40min; dissolve 2% potassium chloride and 1% potassium hydroxide in 3 1% deionized water, stir until all the solids are completely dissolved to obtain an enhancer solution, slowly and evenly add the enhancer solution into the reactor, the addition time is controlled at 60min, and the stirring speed is 120r / mi; adjust the stirring speed to 60r / min again, add 7% octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and 3% oleamidopropyl dimethylamine, and stir for 20min; add 6% didodecyl methyl hydroxypropyl sulfobetaine, stir for 30min, cool to room temperature and discharge, thus producing a microemulsion viscoelastic self-regulating oil displacement agent product for ultra-low permeability reservoirs.

[0038] Embodiment 3: The present invention discloses a method for preparing a microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability oil reservoirs, which is specifically: First, add 9% N'N-dimethylacetamide and 8% N'N-dimethylformamide to the reactor, heat the reactor to 45°C, and start stirring at a stirring speed of 55r / min; then add 10% styrylphenol polyoxyethylene ether, 5.5% isomeric tridecanol polyoxyethylene ether and 1.5% isomeric decanol polyoxyethylene polyoxypropylene ether, and stir for 15 minutes until all the solids are completely dissolved; adjust the stirring speed to 110r / min, slowly and evenly add 12% α-pyrene, and control the addition time to 50min. Add 2.5% potassium chloride and 1.5% hydroxide Potassium is dissolved in 32% deionized water, and the solution is stirred evenly after the solid is completely dissolved to obtain an enhancer solution. The enhancer solution is slowly and evenly added into the reactor, and the dropping time is controlled at 50 minutes and the stirring speed is 110r / min. The stirring speed is adjusted to 55r / min again, and 9% octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and 4% oleamidopropyl dimethylamine are added, and the mixture is stirred for 15 minutes. 5% didodecyl methyl hydroxypropyl sulfobetaine is added, and the mixture is stirred for 30 minutes. The mixture is cooled to room temperature and discharged, and the ultra-low permeability reservoir microemulsion viscoelastic self-regulated oil displacement agent product is produced.

[0039] The following related tests were conducted on the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent prepared in the above embodiment: 1. First, use the gas permeability device to measure the permeability of the core, and then measure the dry weight of the core; use the vacuum device to vacuum the core for 6 hours, and then saturate it with kerosene for about 10 hours, and then measure its wet weight; install the core with the dialysis experimental device, and then pour the liquid (the comparison experiment sample is distilled water or standard brine) into the dialysis experimental device, observe the oil seeping around the core and take pictures, and record the daily oil output.

[0040] Figure 1 The imbibition amount of the microemulsion viscoelastic self-regulating oil displacement agent in ultra-low permeability reservoirs to ultra-low permeability natural core (0.19mD) at different imbibition times. Figure 1 As shown in the figure, the oil output of natural core in ultra-low permeability reservoir is small at the beginning. As time goes by, the oil droplets on the core surface gradually increase and become dense. The self-imbibition of microemulsion viscoelastic self-regulating oil displacement agent in ultra-low permeability reservoir reaches saturation at 0.42ml in 96h, which is much faster than the time (500h) for distilled water and standard brine to reach saturation.

[0041] 2. The changes in the median particle size of the microemulsion viscoelastic self-regulating oil displacement agent in ultra-low permeability reservoirs in aqueous solution at different salinities were tested. The test results are shown in Table 1.

[0042] The standard brine is prepared according to SY / T5107-2021 "Performance Evaluation Method of Water-Based Fracturing Fluid" 7.7.1.1 Standard brine in flowing medium.

[0043] Table 1 Test results of median particle size of microemulsion viscoelastic self-regulating oil displacement agent in ultra-low permeability reservoirs in different media As shown in Table 1, the median particle size of the microemulsion viscoelastic self-regulating oil displacement agent in ultra-low permeability reservoirs in distilled water increases from 6.2nm to 11.6nm as the concentration decreases, and the median particle size increases by about one time as the salinity increases.

[0044] 3. Referring to the viscoelastic test method in Chapter 7.5 of SY / T5107-2016 "Performance Evaluation Method of Water-Based Fracturing Fluid", the viscoelastic index parameters of the microemulsion viscoelastic self-regulating oil displacement agent in ultra-low permeability reservoirs were tested at different frequencies.

[0045] The test results are as follows Figure 2 As shown, the storage modulus G' is greater than 6Pa and the loss modulus G" is greater than 0.35Pa. The storage modulus G' increases with the increase of shear frequency, and the loss modulus G" shows a decreasing trend within the shear frequency of 0.6Hz. When the shear frequency exceeds 0.6Hz, the loss modulus gradually increases.

[0046] 4. With reference to the test method in Chapter 9 of YT 6424-2014 “Composite Oil Displacement System Performance Test Method”, the oil displacement efficiency of the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent on ultra-low permeability natural core was tested. The test results are shown in Table 2.

[0047] Table 2 Oil displacement efficiency test of microemulsion viscoelastic self-regulating oil displacement agent in ultra-low permeability reservoir As shown in Table 2, the oil displacement efficiency of 0.5% microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability natural core (0.21mD) reaches 37.45%, which is 25.42% higher than that of standard brine.

[0048] The preferred embodiments of the present invention are specifically described above, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability reservoirs, characterized in that: The self-regulating oil displacement agent comprises the following components by weight percentage: Micellar agent 10-15%, Emulsifier 15-20%, Co-surfactant 4-6%, Regulator 10-15%, Solubilizer 15-20%, Enhancer 3-5%, The balance was deionized water.

2. The ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent according to claim 1, characterized in that: The micellar agent is composed of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and oleamidopropyl dimethylamine, wherein the weight percentage content of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate is 55-77%, and the weight percentage content of oleamidopropyl dimethylamine is 23-45%.

3. The ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent according to claim 1, characterized in that: The emulsifier is composed of styrylphenol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether and styrylphenol polyoxyethylene ether, wherein the weight percentage content of styrylphenol polyoxyethylene ether is 52-70%, the weight percentage content of isomeric tridecanol polyoxyethylene ether is 25-35%, and the weight percentage content of isomeric decanol polyoxyethylene polyoxypropylene ether is 5-13%.

4. The ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent according to claim 1, characterized in that: The co-surfactant is didodecyl methyl hydroxypropyl sulfobetaine.

5. The ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent according to claim 1, characterized in that: The regulating agent is one or more components of α-peneline or β-peneline.

6. The ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent according to claim 1, characterized in that: The solubilizer is N'N-dimethylacetamide or N'N-dimethylformamide or a mixture of the two.

7. The ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent according to claim 1, characterized in that: The enhancer consists of potassium chloride and potassium hydroxide, wherein the weight percentage of potassium chloride is 50-75%, and the weight percentage of potassium hydroxide is 25-50%.

8. A method for preparing a microemulsion viscoelastic self-regulating oil displacement agent for ultra-low permeability reservoirs, characterized in that: The following steps are involved: First, add 15-20% by weight of a solubilizer into a reactor, heat the reactor to 40-50°C, and start stirring at a stirring speed of 50-60r / min; then add 15-20% by weight of an emulsifier, stir until all solids are completely dissolved; then add 10-15% by weight of a regulator, and control the drop-adding time to be 40-60min; then mix 3-5% by weight of an enhancer and 21-41% by weight of deionized water to obtain an enhancer solution, add the enhancer solution into the reactor under stirring conditions, and control the drop-adding time to be 40-60min; then add 10-15% by weight of a micellar agent, and stir for 10-20min; finally add 4-6% by weight of a co-surfactant, stir for 20-30min, cool to room temperature and discharge, and obtain an ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent product.

9. The method for preparing the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent according to claim 8, characterized in that: The micellar agent is composed of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and oleamidopropyl dimethylamine; The emulsifier is composed of styrylphenol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether and; The co-surfactant is didodecyl methyl hydroxypropyl sulfobetaine; The regulating agent is α-peneline or β-peneline; The solubilizing agent is one of N'N-dimethylacetamide or N'N-dimethylformamide or a mixture of the two; The enhancer consists of potassium chloride and potassium hydroxide.

10. The method for preparing the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent according to claim 9, characterized in that: The following steps are involved: S1, firstly, add 15-20% by weight of N'N-dimethylacetamide or N'N-dimethylformamide or a mixture of the two into a reaction kettle, heat the reaction kettle to 40-50° C., and start stirring at a stirring speed of 50-60 r / min; S2, then add 9-12% by weight of styrylphenol polyoxyethylene ether, 5-6% by weight of isotridecyl alcohol polyoxyethylene ether and 1-2% by weight of isodecyl alcohol polyoxyethylene polyoxypropylene ether, and stir at a stirring speed of 100-120 r / min for 10-20 min until all the solids are completely dissolved; S3, then add 10-15% by weight of α-pyrene or β-pyrene or a mixture thereof, and control the dropping time to be 40-60 min; S4, 2-3% by weight of potassium chloride, 1-2% by weight of potassium hydroxide and 21-41% by weight of deionized water are uniformly mixed to obtain an enhancer solution, and the enhancer solution is added to the reactor under stirring conditions of 100-120 r / min, and the dropping time is controlled to be 40-60 min; S5, under stirring condition of 50-60r / min, add 7-10 weight percent of octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate and 3-5 weight percent of oleamidopropyl dimethylamine, and stir for 10-20min; S6, finally add 4-6% by weight of didodecyl methyl hydroxypropyl sulfobetaine, stir for 20-30 minutes, cool to room temperature and discharge to obtain the ultra-low permeability reservoir microemulsion viscoelastic self-regulating oil displacement agent product.

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