Medium-phase microemulsion oil-displacing agent for low-permeability reservoir and application of medium-phase microemulsion oil-displacing agent

Abstract

The invention relates to a medium-phase microemulsion oil-displacing agent for a low-permeability reservoir and application of the medium-phase microemulsion oil-displacing agent, and the medium-phase microemulsion oil-displacing agent for the low-permeability reservoir is prepared from the following components in percentage by mass: 0.05 wt%-0.3 wt% of an anionic surfactant, 0.05 wt%-0.2 wt% of an anionic-nonionic surfactant and 95 wt%-99.9 wt% of water, the anionic-nonionic surfactant comprises alcohol ether sulfonate and / or alcohol ether carboxylate. The medium-phase microemulsion oil-displacing agent for the low-permeability reservoir can form a stable medium-phase microemulsion under the conditions of low dosage and low permeability, has high oil-displacing efficiency, can greatly improve the recovery degree of the reservoir, and solves the problem that a medium phase is difficult to form in the low-permeability reservoir; and the system is easy to dissolve, does not generate phase separation precipitation, and is easy to prepare and use.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field exploitation, and in particular relates to a low-permeability reservoir middle-phase microemulsion oil displacement agent and application thereof. Background Art

[0002] my country's low-permeability oil reservoirs are rich in reserves and have become the main battlefield for oil development. Compared with medium and high permeability oil reservoirs, low-permeability oil reservoirs have more complex reservoir properties and more prominent development contradictions. The rock properties are poor, the pore throats are small, and there is a serious Jamin effect. These problems all lead to low water injection recovery rates in low-permeability oil fields, low initial production capacity, and rapid production decline. After water flooding, a large amount of crude oil is still retained underground and cannot be effectively developed. The overall development level of low-permeability oil reservoirs is low, and the calibrated recovery rate is below 20%.

[0003] At present, a considerable number of low permeability reservoirs have entered the high water content or even ultra-high water content stage at low recovery, with serious invalid circulation, and it is urgent to develop replacement technologies to significantly improve the recovery rate. Low permeability reservoirs usually have strong microscopic heterogeneity and uneven pore distribution, which affects the oil recovery efficiency and sweep efficiency of the oil recovery system. At present, the main technologies for improving the recovery rate of low permeability reservoirs include: molecular membrane technology, imbibition oil recovery technology, nano-injection technology, surfactant flooding technology, foam flooding technology, microsphere flooding and other technologies.

[0004] CN112126009A discloses a polyacrylamide microsphere, a nanoemulsion for low permeability oil reservoir adjustment and flooding, and a preparation method and application thereof. The microsphere is a copolymer of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and N,N-methylenebisacrylamide, and the average particle size of the microsphere is 40-120nm. The emulsion comprises the polyacrylamide microsphere and white oil. The polyacrylamide microsphere is a nano-scale microsphere with good expansion performance and can be used for low permeability oil reservoir adjustment and flooding. The emulsion uses white oil as the oil phase and adds tetrasodium ethylenediaminetetraacetic acid as a dispersant to improve the dispersion uniformity of the polyacrylamide emulsion. The obtained nanoemulsion has a small particle size, good fluidity, and good expansion performance. It can continuously migrate and block the pores in the low permeability oil reservoir, thereby increasing the volume of injected water swept and improving the recovery rate of the low permeability oil reservoir.

[0005] CN107603582A discloses a high-efficiency foaming agent for air foam flooding, which is mixed by the following components by mass percentage: polyether segment-containing betaine amphoteric surfactant, alkylamide propyl dimethyl amine oxide, cationic alkyl polysaccharide, thickening foam stabilizer, sodium chloride, alkyl sodium sulfate, N-(2-pyridyl) alcohol ether methylene amide, and the balance is water. The foaming agent of the invention has strong comprehensive foam performance, corrosion resistance, high mineralization resistance and oil resistance. In the field of oil field production, it can meet the performance requirements of foam flooding of low permeability reservoirs.

[0006] However, although the above-mentioned technologies have improved the injection capacity and development effect of low permeability reservoirs to a certain extent, and have a certain ability to reduce water and increase oil production, they cannot fundamentally solve the problems of expanding the swept volume and improving the oil recovery efficiency of low permeability reservoirs. Therefore, it is urgent to develop a new technology for improving the recovery rate suitable for low permeability reservoirs. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a low permeability reservoir intermediate phase microemulsion oil displacement agent and its application, which can form a stable intermediate phase microemulsion under low permeability conditions, greatly improve the recovery rate, and is of great significance to the efficient development of low permeability reservoirs.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a low permeability reservoir middle phase microemulsion oil displacement agent, wherein the components of the low permeability reservoir middle phase microemulsion oil displacement agent include, by mass percentage:

[0010] Anionic surfactant 0.05wt%-0.3wt%, anionic-nonionic surfactant 0.05wt%-0.2wt%, water 95wt%-99.9wt%;

[0011] The anionic nonionic surfactant includes alcohol ether sulfonates and / or alcohol ether carboxylates.

[0012] The low-permeability reservoir intermediate phase microemulsion oil displacement of the present invention can form a stable intermediate phase microemulsion through the coordination of the above-mentioned surfactant, and there is almost no capillary resistance in the oil displacement process, and it can enter the low-permeability matrix under a small pressure gradient condition, and has a strong ability to mobilize crude oil in tiny low-permeability pores, greatly reducing the mobilization limit of the injection system, and thus can greatly improve the oil displacement efficiency and sweep efficiency of the low-permeability reservoir. In addition, the oil displacement agent of the present invention selects alcohol ether sulfonate and / or alcohol ether carboxylate to be used in combination with anionic surfactants, so that the system is not easy to be adsorbed and retained, and the stability is better.

[0013] The amount of the anionic surfactant in the low-permeability reservoir middle phase microemulsion oil displacement agent of the present invention can be 0.06wt%, 0.08wt%, 0.1wt%, 0.12wt%, 0.14wt%, 0.16wt%, 0.18wt%, 0.2wt%, 0.22wt%, 0.24wt%, 0.26wt% or 0.28wt%, etc.;

[0014] The amount of the anionic nonionic surfactant can be 0.06wt%, 0.08wt%, 0.1wt%, 0.12wt%, 0.14wt%, 0.16wt% or 0.18wt%, etc.;

[0015] The amount of water used can be 95.5wt%, 96wt%, 97wt%, 98wt%, 99wt%, 99.2wt%, 99.5wt% or 99.8wt%, etc.

[0016] Preferably, the anionic surfactant is a carboxylate surfactant and / or a sulfonate surfactant.

[0017] Preferably, the anionic surfactant is a combination of a carboxylate surfactant and a sulfonate surfactant.

[0018] Preferably, the carboxylate surfactant includes any one of oleate, stearate or ricinoleate, or a combination of at least two of them.

[0019] Preferably, the carboxylate surfactant includes any one of sodium oleate, potassium oleate, sodium stearate, sodium ricinoleate, or a combination of at least two thereof.

[0020] Preferably, the sulfonate surfactant comprises alkylbenzenesulfonate and / or alkylnaphthalenesulfonate.

[0021] Preferably, the sulfonate surfactant includes any one of sodium dodecylbenzenesulfonate, sodium hexadecylbenzenesulfonate, sodium octadecylbenzenesulfonate, sodium dodecylnaphthalenesulfonate, sodium hexadecylnaphthalenesulfonate or sodium octadecylnaphthalenesulfonate, or a combination of at least two thereof.

[0022] Preferably, the anionic surfactant is a combination of sodium hexadecylbenzene sulfonate, sodium oleate and sodium stearate.

[0023] Preferably, the mass ratio of sodium hexadecylbenzene sulfonate, sodium oleate and sodium stearate is (1-2):(0.5-1.5):(0.1-0.5).

[0024] Wherein "1-2" can be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9, etc.;

[0025] “0.5-1.5” can mean 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or 1.4, etc.;

[0026] “0.1-0.5” can mean 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 or 0.45, etc.

[0027] Preferably, the alcohol ether sulfonate has the following structure:

[0028] R-(EO) i -(PO) j -SO3Na;

[0029] Wherein, i and j are independently integers of 20-40 (for example, 21, 23, 25, 28, 30, 32, 35, 37 or 39, etc.); R is selected from C6-C24 alkyl alcohol (for example, C8, C10, C12, C14, C16, C18, C20 or C22, etc.).

[0030] Preferably, the alcohol ether carboxylate has the following structure:

[0031] R-(EO) i -(PO) j -CO2Na;

[0032] Wherein, i and j are independently integers of 20-40 (for example, 21, 23, 25, 28, 30, 32, 35, 37 or 39, etc.); R is selected from C6-C24 alkyl alcohol (for example, C8, C10, C12, C14, C16, C18, C20 or C22, etc.).

[0033] Preferably, the low permeability reservoir middle phase microemulsion oil displacement agent further comprises 0.05wt%-0.1wt% of polyelectrolyte, for example, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt% or 0.1wt%, etc., in terms of mass percentage.

[0034] The low-permeability reservoir mid-phase microemulsion oil-displacing agent of the present invention adds polyelectrolyte, which interacts with two surfactants to reduce the interfacial tension of the system, thereby achieving the effect of improving the recovery rate of the low-permeability reservoir.

[0035] Preferably, the polyelectrolyte is a low molecular weight polyelectrolyte with a molecular weight of 3000-100000, for example, the molecular weight may be 5000, 10000, 30000, 50000, 70000 or 90000, etc.

[0036] Preferably, the polyelectrolyte comprises any one or a combination of at least two of sodium polyacrylate, sodium polymethacrylate, sodium polystyrene sulfonate, sodium polyethylene sulfonate, polyethyleneimine, polyethyleneamine or polyvinylpyridine;

[0037] Preferably, the polyelectrolyte is a combination of sodium polyacrylate and sodium polystyrene sulfonate;

[0038] Preferably, the mass ratio of the sodium polyacrylate to sodium polystyrene sulfonate is 1:(0.5-2), for example, it can be 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.6 or 1:1.8, etc.

[0039] Preferably, the water is any one of reinjection water or produced water.

[0040] Any specific point value within the above numerical range can be selected, and will not be described in detail here.

[0041] In a second aspect, the present invention provides a method for preparing a low-permeability reservoir intermediate phase microemulsion oil displacement agent as described in the first aspect, the method comprising sequentially adding anionic surfactants and anionic-nonionic surfactants to water, and mixing them uniformly to obtain the oil displacement agent.

[0042] Preferably, the mixing further comprises adding a polyelectrolyte;

[0043] Preferably, the mixing is performed in a stirring manner, and the stirring speed is 200-300 r / min, for example, 210 r / min, 230 r / min, 250 r / min, 270 r / min or 290 r / min.

[0044] Any specific point value within the above numerical range can be selected, and will not be described in detail here.

[0045] In a third aspect, the present invention provides a use of the low-permeability reservoir intermediate-phase microemulsion oil displacement agent as described in the first aspect in oil production.

[0046] The low-permeability reservoir medium-phase microemulsion flooding of the present invention is used for oil production and belongs to the medium-phase microemulsion flooding technology. It polymerizes and displaces crude oil through the solubilization effect of surfactants. There is almost no capillary resistance in the oil flooding process, and the oil displacement efficiency and sweep efficiency are greatly improved. Compared with traditional chemical flooding technology, the medium-phase microemulsion system can enter the low-permeability matrix under a smaller pressure gradient condition, has a strong ability to mobilize crude oil in tiny low-permeability pores, and greatly reduces the mobilization limit of the injection system. Therefore, it has broad application prospects in low-permeability reservoirs.

[0047] Preferably, inorganic salts are added to the low-permeability reservoir middle-phase microemulsion oil-displacing agent during use.

[0048] Preferably, the amount of the inorganic salt is 0.1-2% of the total amount of the microemulsion oil displacement agent in the low permeability reservoir, for example, it can be 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5% or 1.8%.

[0049] Preferably, the inorganic salt is any one of sodium hydroxide, sodium hydroxide, potassium hydroxide, sodium pyrophosphate, sodium metaphosphate, sodium chloride, potassium chloride, calcium chloride or magnesium chloride, or a combination of at least two thereof.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) The middle phase microemulsion oil displacement agent provided by the present invention can form a stable middle phase microemulsion under low dosage and low permeability conditions, solving the problem that it is difficult to form a middle phase in low permeability oil reservoirs;

[0052] (2) The medium-phase microemulsion oil-displacing agent provided by the present invention is easily soluble, does not undergo phase separation and precipitation, and is easy to prepare and use;

[0053] (3) The low-osmotic medium-phase microemulsion oil-displacing agent provided by the present invention has high oil displacement efficiency and can greatly improve the recovery rate of oil reservoirs;

[0054] (4) The low-permeability middle-phase microemulsion oil-displacing agent provided by the present invention has a simple preparation process and is easy to realize large-scale industrial production of the product, thereby promoting the popularization and application of middle-phase microemulsion oil-displacing technology in the field of oil production. DETAILED DESCRIPTION

[0055] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If the manufacturers of the instruments used are not specified, they are all conventional products that can be purchased through regular channels.

[0056] The source information of some materials involved in the following examples and comparative examples is as follows:

[0057] The C12 Guerbet alcohol ether sulfonate sodium (i=25, j=30) and C12 Guerbet alcohol ether sulfonate sodium (i=15, j=45) are both homemade in the laboratory. The preparation methods refer to the literature "Preparation of C_(16) Guerbet alcohol polyoxyalkylene ether sulfate and study on its interfacial properties", Chen Qi et al., "Daily Chemical Industry (Chinese and English)", Vol. 52, No. 10, 2022, pp. 1055-1061, and the patent "CN201210058204.1, published on 20120801".

[0058] The sodium hexadecyl alcohol ether sulfonate (i=20, j=25) and sodium octadecyl alcohol ether sulfonate (i=30, j=30) are both homemade in the laboratory. The preparation method refers to "Research on the Synthesis of High-Purity Sodium Dodecylbenzene Sulfonate", Cui Lianfu, Shi Lixin, Zhan Manli, Liu Cao, etc., Journal of Shenyang Chemical University, Issue 02, 1990.

[0059] The remaining raw materials in the embodiments of the present invention can be used as long as they are purchased from regular dealers.

[0060] Example 1

[0061] The present embodiment provides a low permeability reservoir middle phase microemulsion oil displacement agent, which includes, by mass percentage, 0.1% sodium hexadecylbenzene sulfonate, 0.075% sodium oleate, 0.025% sodium stearate, 0.16% sodium C12 Guerbet alcohol ether sulfonate (i=25, j=30), 0.04% sodium polyacrylate, 0.04% sodium polystyrene sulfonate, and the balance is formation water.

[0062] The preparation method of the low-permeability reservoir middle-phase microemulsion oil-displacing agent comprises: adding sodium hexadecylbenzene sulfonate, sodium oleate, sodium stearate, sodium C12 Guerbet alcohol ether sulfonate, sodium polyacrylate and sodium polystyrene sulfonate into formation water in sequence according to mass percentage, and stirring at a rotation speed of 250 r / min for 1 hour to obtain the low-permeability reservoir middle-phase microemulsion oil-displacing agent.

[0063] Example 2

[0064] The present embodiment provides a low permeability reservoir middle phase microemulsion oil displacement agent, which includes, by mass percentage, 0.08% sodium hexadecylbenzene sulfonate, 0.02% sodium oleate, 0.02% sodium stearate, 0.2% sodium octadecyl alcohol ether sulfonate (i=30, j=30), 0.06% sodium polyacrylate, 0.03% sodium polystyrene sulfonate, and the balance is formation water.

[0065] The preparation method of the low-permeability reservoir middle-phase microemulsion oil-displacing agent comprises: adding sodium hexadecylbenzene sulfonate, sodium oleate, sodium stearate, sodium octadecyl alcohol ether sulfonate, sodium polyacrylate and sodium polystyrene sulfonate to formation water in sequence according to mass percentage, and stirring at a rotation speed of 250 r / min for 1 hour to obtain the low-permeability reservoir middle-phase microemulsion oil-displacing agent.

[0066] Example 3

[0067] The present embodiment provides a low permeability reservoir middle phase microemulsion oil displacement agent, which includes, by mass percentage, 0.15% sodium hexadecylbenzene sulfonate, 0.14% sodium oleate, 0.01% sodium stearate, 0.1% sodium hexadecyl alcohol ether sulfonate (i=20, j=25), 0.02% sodium polyacrylate, 0.04% sodium polystyrene sulfonate, and the balance is formation water.

[0068] The preparation method of the low-permeability reservoir middle-phase microemulsion oil-displacing agent comprises: adding sodium hexadecylbenzene sulfonate, sodium oleate, sodium stearate, sodium hexadecyl alcohol ether sulfonate, sodium polyacrylate and sodium polystyrene sulfonate into formation water in order by mass percentage, and stirring at a speed of 250 r / min for 1 hour to obtain the low-permeability reservoir middle-phase microemulsion oil-displacing agent.

[0069] Example 4

[0070] This embodiment provides a low-permeability reservoir mid-phase microemulsion oil-displacing agent. The only difference between the oil-displacing agent and Example 1 is that the anionic surfactant in the oil-displacing agent does not include sodium stearate, and the reduced amount is distributed to sodium hexadecylbenzene sulfonate and sodium oleate according to the original ratio. The remaining components are consistent with Example 1, and the preparation method refers to Example 1.

[0071] Example 5

[0072] This embodiment provides a low-permeability reservoir mid-phase microemulsion oil-displacing agent. The only difference between the oil-displacing agent and Example 1 is that the anionic surfactant in the oil-displacing agent does not include sodium oleate, and the reduced amount thereof is distributed to sodium hexadecylbenzene sulfonate and sodium stearate according to the original ratio. The remaining components are consistent with those in Example 1, and the preparation method refers to Example 1.

[0073] Example 6

[0074] This embodiment provides a low permeability reservoir middle phase microemulsion oil displacing agent, the oil displacing agent is different from Example 1 only in that the anionic surfactant in the oil displacing agent does not include sodium hexadecylbenzene sulfonate, and the reduced amount thereof is distributed to sodium oleate and sodium stearate according to the original ratio, and the remaining components are consistent with Example 1, and the preparation method refers to Example 1.

[0075] Example 7

[0076] This embodiment provides a low permeability reservoir middle phase microemulsion oil displacement agent, the oil displacement agent is different from Example 1 only in that the C12 Guerbet alcohol ether sulfonate sodium (i = 25, j = 30) is replaced by C12 Guerbet alcohol ether sulfonate sodium (i = 15, j = 45) in equal amounts, and the other components are consistent with Example 1, and the preparation method is consistent with Example 1.

[0077] Example 8

[0078] This embodiment provides a low permeability reservoir middle phase microemulsion oil displacement agent, the oil displacement agent is different from the embodiment 1 only in that it does not include polyelectrolyte, the reduced amount of which is supplemented by formation water, and the other components are consistent with the embodiment 1. The preparation method refers to the embodiment 1.

[0079] Example 9

[0080] This embodiment provides a low permeability reservoir middle phase microemulsion oil displacement agent. The oil displacement agent is different from that of Example 1 only in that the polyelectrolyte is 0.08% sodium polyacrylate, and the other components are consistent with those of Example 1. The preparation method is similar to that of Example 1.

[0081] Example 10

[0082] This embodiment provides a low permeability reservoir middle phase microemulsion oil displacement agent. The oil displacement agent is different from that of Example 1 only in that the polyelectrolyte is 0.08% sodium polystyrene sulfonate, and the other components are consistent with those of Example 1. The preparation method is similar to that of Example 1.

[0083] Comparative Example 1

[0084] This comparative example provides a low permeability reservoir mid-phase microemulsion oil displacement agent, which differs from Example 1 only in that it does not include anionic surfactant, and its reduced amount is supplemented by anionic-nonionic surfactant. The remaining components are consistent with Example 1, and the preparation method refers to Example 1.

[0085] Comparative Example 2

[0086] This comparative example provides a low-permeability reservoir mid-phase microemulsion oil-displacing agent, which differs from Example 1 only in that it does not include an anionic non-ionic surfactant, the reduced amount of which is supplemented by an anionic surfactant, and the ratio of sodium hexadecylbenzene sulfonate, sodium oleate, and sodium stearate is kept unchanged, and the remaining components are consistent with Example 1. The preparation method refers to Example 1.

[0087] Test Example 1

[0088] The interfacial tension of the low permeability reservoir mid-phase microemulsion oil displacement agent of Examples 1-10 and Comparative Examples 1-2 was tested by TX500C. The oil and water used in the test were oil and water from an oil field in Changqing. The test temperature was 55°C and the test time was 2 hours. The results are shown in Table 1.

[0089] Test Example 2

[0090] The low permeability reservoir intermediate phase microemulsion oil displacement agents of Examples 1-10 and Comparative Examples 1-2 were mixed with Changqing crude oil at a volume ratio of 1:1 and placed in a beaker, stirred, and the stirred mixture was poured into a graduated tube, and then placed in a 55°C thermostat to observe whether the oil displacement agent can form an intermediate phase microemulsion. The results are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] Test Example 3

[0095] The low permeability reservoir medium phase microemulsion oil displacement agent of Examples 1-10 and Comparative Examples 1-2 was used to evaluate the effect of improving the recovery rate through oil displacement experiments. The test method refers to the petroleum industry standard SY / T 6424-2014 to carry out core oil displacement experiment evaluation. The oil displacement experiment procedure is: core vacuum saturated with formation water - determination of water phase permeability - saturation of crude oil to produce bound water - water displacement to 98% water content - injection of medium phase microemulsion oil displacement agent segment plug - subsequent conversion to formation water displacement to 98% water content.

[0096] The results are shown in Table 2.

[0097] Table 2

[0098]

[0099]

[0100] From the data in Tables 1 and 2, it can be seen that the low permeability reservoir intermediate phase microemulsion oil displacement agent obtained in Example 1-3 can form an intermediate phase microemulsion, and the interfacial tension of the oil displacement agent is smaller, which is only 8.16×10 -4 -2.55×10 -3 After the oil-displacing agent is used in the oil-displacing experiment, the water-side permeability is above 4.0 mD, the oil saturation is above 65%, and the recovery rate is further increased by more than 15% on the basis of the water-displacing recovery rate of 35% to 40%. This shows that the medium-phase microemulsion oil-displacing agent in the low-permeability oil reservoir of the present invention will not undergo phase separation and precipitation, and is easy to prepare and use; and the oil-displacing efficiency is high, which can greatly improve the recovery degree of the oil reservoir.

[0101] The applicant declares that the present invention illustrates a low permeability reservoir medium phase microemulsion oil displacement agent and its application through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process flow to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A low permeability reservoir mid-phase microemulsion oil displacement agent, characterized in that: In terms of mass percentage, the components of the low permeability reservoir middle phase microemulsion oil displacement agent include: Anionic surfactant 0.05wt%-0.3wt%, anionic-nonionic surfactant 0.05wt%-0.2wt%, water 95wt%-99.9wt%; The anionic nonionic surfactant includes alcohol ether sulfonates and / or alcohol ether carboxylates.

2. The low permeability reservoir mid-phase microemulsion oil displacement agent according to claim 1, characterized in that: The anionic surfactant is a carboxylate surfactant and / or a sulfonate surfactant; Preferably, the anionic surfactant is a combination of a carboxylate surfactant and a sulfonate surfactant; Preferably, the carboxylate surfactant comprises any one or a combination of at least two of oleate, stearate or ricinoleate; Preferably, the carboxylate surfactant includes any one of sodium oleate, potassium oleate, sodium stearate, sodium ricinoleate, or a combination of at least two thereof; Preferably, the sulfonate surfactant comprises alkylbenzene sulfonate and / or alkylnaphthalene sulfonate; Preferably, the sulfonate surfactant includes any one or a combination of at least two of sodium dodecylbenzenesulfonate, sodium hexadecylbenzenesulfonate, sodium octadecylbenzenesulfonate, sodium dodecylnaphthalenesulfonate, sodium hexadecylnaphthalenesulfonate or sodium octadecylnaphthalenesulfonate; Preferably, the anionic surfactant is a combination of sodium hexadecylbenzene sulfonate, sodium oleate and sodium stearate; Preferably, the mass ratio of sodium hexadecylbenzene sulfonate, sodium oleate and sodium stearate is (1-2):(0.5-1.5)(0.1-0.5).

3. The low permeability reservoir intermediate phase microemulsion oil displacement agent according to claim 1 or 2, characterized in that: The alcohol ether sulfonate has the following structure: R-(EO) i -(PO) j -SO3Na; Wherein, i and j are independently integers of 20-40; and R is selected from C6-C24 alkyl alcohol.

4. The low permeability reservoir mid-phase microemulsion oil displacement agent according to claim 1 or 2, characterized in that: The alcohol ether carboxylate has the following structure: R-(EO) i -(NIGHT) j -CO2Na; Wherein, i and j are independently integers of 20-40; and R is selected from C6-C24 alkyl alcohol.

5. The low permeability reservoir mid-phase microemulsion oil displacement agent according to any one of claims 1 to 4, characterized in that: In terms of mass percentage, the low permeability reservoir middle phase microemulsion oil displacement agent further comprises 0.05wt%-0.1wt% of polyelectrolyte; Preferably, the polyelectrolyte is a low molecular weight polyelectrolyte with a molecular weight of 3000-100000.

6. The low permeability reservoir middle phase microemulsion oil displacement agent according to claim 5, characterized in that: The polyelectrolyte comprises any one or a combination of at least two of sodium polyacrylate, sodium polymethacrylate, sodium polystyrene sulfonate, sodium polyethylene sulfonate, polyethyleneimine, polyvinylamine or polyvinylpyridine; Preferably, the polyelectrolyte is a combination of sodium polyacrylate and sodium polystyrene sulfonate; Preferably, the mass ratio of the sodium polyacrylate to sodium polystyrene sulfonate is 1:(0.5-2).

7. The low permeability reservoir mid-phase microemulsion oil displacement agent according to any one of claims 1 to 6, characterized in that: The water is any one of reinjection water or produced water.

8. Use of the low permeability reservoir intermediate phase microemulsion oil displacement agent according to any one of claims 1 to 7 in oil production.

9. The use according to claim 8, characterized in that: The low permeability reservoir middle phase microemulsion oil displacement agent is added with inorganic salts during use; Preferably, the amount of the inorganic salt is 0.1-2% of the total amount of the microemulsion oil displacement agent in the low permeability reservoir.

10. The use according to claim 9, characterized in that: The inorganic salt is any one of sodium hydroxide, sodium hydroxide, potassium hydroxide, sodium pyrophosphate, sodium metaphosphate, sodium chloride, potassium chloride, calcium chloride or magnesium chloride, or a combination of at least two thereof.

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