Homogeneous microemulsion type permeability-enhancing oil-displacing agent as well as preparation method and application of homogeneous microemulsion type permeability-enhancing oil-displacing agent

Abstract

The invention belongs to the field of oil exploitation, and relates to a homogeneous microemulsion type permeability-enhancing oil-displacing agent as well as a preparation method and application thereof. The homogeneous microemulsion type permeation-enhancing oil-displacing agent provided by the invention comprises an organic solvent, a surfactant, an ion regulator and water. The homogeneous micro-emulsion type permeability-increasing oil displacement agent provided by the invention has nano-scale emulsion particles, has good solubilizing capacity, and can be used for removing blockage of an oil layer, improving the imbibition capacity of displacement fluid and the like. And compared with the conventional surfactant, the adsorption of the homogeneous microemulsion type permeability-enhancing oil displacement agent on the rock surface is smaller, and the effective acting distance in the stratum is longer. The homogeneous microemulsion type permeability-enhancing oil-displacing agent provided by the invention can reduce surface tension, change rock wettability, reduce or eliminate gas fingering, reduce irreducible water saturation and increase oil phase permeability by reducing surface tension.

Description

Technical Field

[0001] The invention belongs to the field of petroleum exploitation and relates to a homogeneous microemulsion type permeation-enhancing oil-displacing agent and a preparation method and application thereof. Background Art

[0002] Heavy oil is mainly produced by thermal methods, including steam huff and puff, steam flooding, and fire burning, etc. The development of deep heavy oil and ordinary heavy oil mainly adopts a combination of cold and thermal recovery and water flooding.

[0003] As the development cycle lengthens, the use of water drive to exploit heavy oil reservoirs will lead to problems such as water production and water flooding. Therefore, for heavy oil reservoirs that can be water-driven, it is not feasible to rely solely on water drive to increase the recovery rate.

[0004] However, in the exploitation of heavy oil reservoirs, when a surfactant is simply used to drive heavy oil for cold recovery of heavy oil, due to the strong heterogeneity of the heavy oil reservoir, the reservoir permeability difference is large, the mobility ratio of heavy oil to water is large, and the viscosity of heavy oil is large and the fluidity is poor. The simple use of surfactants to drive heavy oil will reduce the surface activity because the surfactant is adsorbed by the reservoir, so that the displacement efficiency decreases. At the same time, without the function of "adjustment", a convenient water flow channel will be formed due to the large difference in oil and water mobility, and the purpose of oil displacement cannot be achieved. Therefore, providing a permeability-enhancing oil displacement agent, which has lower surface tension and good solubilization ability at the same time, is a technical problem that needs to be solved by those skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to provide a homogeneous microemulsion type permeation-enhancing oil-displacing agent and a preparation method and application thereof. The homogeneous microemulsion type permeation-enhancing oil-displacing agent provided by the present invention has low surface tension and good solubilization ability.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a homogeneous microemulsion type permeation oil displacement agent, comprising an oil phase and an aqueous phase, wherein the oil phase comprises an organic solvent, and the aqueous phase comprises a surfactant, an ion regulator and water;

[0008] The surfactant includes anionic surfactant, cationic surfactant, nonionic surfactant and zwitterionic surfactant; the nonionic surfactant does not include nonionic polyoxyethylene ether perfluoro surfactant and alkyl glucoside carboxylate.

[0009] Preferably, the organic solvent comprises terpineol and / or terpene;

[0010] The volume ratio of the oil phase to the water phase is 1:4-5.

[0011] Preferably, the anionic surfactant includes one or more of fatty alcohol polyoxyethylene ether carboxylates, sodium α-olefin sulfonates and fatty alcohol polyoxyethylene ether phosphates;

[0012] The cationic surfactant comprises an alkyl glucoside quaternary ammonium salt, wherein the carbon number of the alkyl group in the alkyl glucoside quaternary ammonium salt is 12 to 16;

[0013] The nonionic surfactant is polyoxyethylene isomeric alcohol ether and / or nonionic betaine;

[0014] The zwitterionic surfactant includes zwitterionic betaine;

[0015] The mass ratio of the anionic surfactant, the cationic surfactant, the nonionic surfactant and the zwitterionic surfactant is 5-7:6-10:15-20:8-12.

[0016] Preferably, the ion regulator comprises sodium chloride and / or potassium chloride;

[0017] The mass ratio of the anionic surfactant, the ion regulator and water is 6-8:1-3:42-50.

[0018] Preferably, the aqueous phase further comprises a surface conditioner, and the surface conditioner is a nonionic polyoxyethylene ether perfluoro surfactant; the mass ratio of the anionic surfactant to the surface conditioner is 6 to 8:2.2 to 3.5.

[0019] Preferably, the aqueous phase further comprises a phase transfer agent, and the phase transfer agent is alkyl glucoside carboxylate. The mass ratio of the anionic surfactant to the phase transfer agent is 6-8:8-12.

[0020] The present invention also provides a method for preparing the homogeneous microemulsion type permeation-enhancing oil displacement agent described in the above technical solution, comprising the following steps:

[0021] Mixing anionic surfactant, cationic surfactant and water to obtain an aqueous phase solution;

[0022] The aqueous phase solution is heated to a first temperature, and an ion regulator, an organic solvent and a nonionic surfactant are added and stirred for a first time to obtain a first homogeneous solution;

[0023] The first homogeneous solution is heated to a second temperature, and a zwitterionic surfactant is added thereto and stirred for a second time to obtain the homogeneous microemulsion type permeation-enhancing oil displacement agent.

[0024] Preferably, the first temperature is 60-65°C, and the second temperature is 70-75°C;

[0025] The first stirring time is 1 to 2 hours, and the second stirring time is 2 to 4 hours.

[0026] Preferably, when the aqueous phase further comprises a phase transfer agent, the phase transfer agent is added during the first stirring process;

[0027] When the water phase further includes a surface conditioner, the surface conditioner is added during the second stirring.

[0028] The present invention also provides the use of the homogeneous microemulsion type permeability-enhancing oil-displacing agent described in the above technical solution or the homogeneous microemulsion type permeability-enhancing oil-displacing agent prepared by the preparation method described in the above technical solution in the exploitation of low-permeability heavy oil reservoirs.

[0029] The present invention provides a homogeneous microemulsion type permeation oil-displacing agent, comprising an oil phase and an aqueous phase, wherein the oil phase comprises an organic solvent, and the aqueous phase comprises a surfactant, an ion regulator and water; the surfactant comprises an anionic surfactant, a cationic surfactant, a nonionic surfactant and a zwitterionic surfactant; the nonionic surfactant does not include a nonionic polyoxyethylene ether perfluoro surfactant and an alkyl glucoside carboxylate. The homogeneous microemulsion type permeation oil-displacing agent provided by the present invention comprises an organic solvent, a surfactant, an ion regulator and water. The homogeneous microemulsion type permeation oil-displacing agent provided by the present invention has nano-scale emulsion particles and good solubilizing ability, and can be used to remove oil layer blockage, improve the permeability of displacement fluid, etc. Moreover, the adsorption of the homogeneous microemulsion type permeation oil-displacing agent on the rock surface is smaller than that of conventional surfactants, and the effective action distance in the formation is longer. The homogeneous microemulsion type permeation oil-displacing agent provided by the present invention can reduce or eliminate gas fingering, reduce bound water saturation, and increase oil phase permeability by reducing surface tension and changing rock wettability. The homogeneous microemulsion type permeation oil displacement agent provided by the present invention is a nanometer-level liquid with a spherical structure, and can easily enter and exit micro-nanometer-level pore throats and pores, thereby improving sweep efficiency.

[0030] The present invention also provides the use of the homogeneous microemulsion type permeability oil-displacing agent described in the above technical scheme or the homogeneous microemulsion type permeability oil-displacing agent prepared by the preparation method described in the above technical scheme in the exploitation of low-permeability heavy oil reservoirs. The homogeneous microemulsion type permeability oil-displacing agent provided by the present invention can remove organic blockage in the near-wellbore area and artificial fracture network by solubilizing and dispersing colloidal asphaltene and fracturing fluid residues; the homogeneous microemulsion type permeability oil-displacing agent provided by the present invention can greatly reduce capillary force, starting pressure and adhesion work, and improve water phase permeability and imbibition replacement rate through interface modification. The results of the application example show that by adding 0.3% of the homogeneous microemulsion type permeability oil-displacing agent to the fluid of the injection well, the sandstone formation can restore 75% to 85% of the permeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1is a graph showing the variation of permeability with injection volume in Test Example 3;

[0032] Figure 2 This is a curve diagram showing the injection pressure changing with the injection volume in Test Example 3;

[0033] Figure 3 The NMR T2 spectra at different oil displacement stages in Test Example 4;

[0034] Figure 4 This is the distribution diagram of pore utilization degree in different oil recovery stages in Test Example 4. DETAILED DESCRIPTION

[0035] The present invention provides a homogeneous microemulsion type permeation oil displacement agent, comprising an oil phase and an aqueous phase, wherein the oil phase comprises an organic solvent, and the aqueous phase comprises a surfactant, an ion regulator and water;

[0036] The surfactant includes anionic surfactant, cationic surfactant, nonionic surfactant and zwitterionic surfactant; the nonionic surfactant does not include nonionic polyoxyethylene ether perfluoro surfactant and alkyl glucoside carboxylate.

[0037] In the present invention, unless otherwise specified, all components are commercially available products well known to those skilled in the art.

[0038] In the present invention, the organic solvent preferably includes pinene alcohol and / or terpene; when the organic solvent is pinene alcohol and terpene, the volume ratio of pinene alcohol to terpene is preferably 1:1-2. In the present invention, the volume ratio of the oil phase to the water phase is preferably 1:4-5. In the present invention, the oil phase and the surfactant are both environmentally friendly substances and do not cause any pollution to the environment after biodegradation.

[0039] In the present invention, the anionic surfactant preferably includes one or more of fatty alcohol polyoxyethylene ether carboxylates, sodium α-olefin sulfonates and fatty alcohol polyoxyethylene ether phosphates. In the present invention, the fatty alcohol polyoxyethylene ether phosphates preferably include AEO-7 or AEO-9.

[0040] In the present invention, the cationic surfactant preferably comprises an alkyl glycoside quaternary ammonium salt, and the carbon number of the alkyl group in the alkyl glycoside quaternary ammonium salt is preferably 12-16.

[0041] In the present invention, the nonionic surfactant is preferably polyoxyethylene isomeric alcohol ether and / or nonionic betaine. In the present invention, the polyoxyethylene isomeric alcohol ether specifically preferably includes isomeric undecanol polyoxyethylene ether or isomeric tridecanol polyoxyethylene ether.

[0042] In the present invention, the zwitterionic surfactant preferably includes zwitterionic betaine, and the zwitterionic betaine is preferably one or more of CAB-35, CAB-40, OAB-40 and OAO-40.

[0043] In the present invention, the mass ratio of the anionic surfactant, the cationic surfactant, the nonionic surfactant and the zwitterionic surfactant is preferably 5-7:6-10:15-20:8-12, and more preferably 5-6:7-8:16-18:9-10.

[0044] In the present invention, the ion regulator preferably includes sodium chloride and / or potassium chloride; the mass ratio of the anionic surfactant, the ion regulator and water is preferably 6-8:1-3:42-50, and more preferably 6-7:1-2:45-48.

[0045] In the present invention, the aqueous phase also preferably includes a surface conditioner, and the surface conditioner is preferably a non-ionic polyoxyethylene ether perfluoro surfactant; the non-ionic polyoxyethylene ether perfluoro surfactant preferably includes a 10-carbon fatty alcohol polyoxyethylene ether perfluoro surfactant and / or a 12-carbon fatty alcohol polyoxyethylene ether perfluoro surfactant; the mass ratio of the anionic surfactant to the surface conditioner is preferably 6 to 8:2.2 to 3.5.

[0046] In the present invention, the aqueous phase also preferably includes a phase transfer agent, and the phase transfer agent is preferably an alkyl glucoside carboxylate; the alkyl glucoside carboxylate specifically preferably includes APG0812 or APG0810. In the present invention, the mass ratio of the anionic surfactant to the phase transfer agent is preferably 6-8:8-12.

[0047] The present invention also provides a method for preparing the homogeneous microemulsion-type permeation-enhancing oil-displacing agent described in the above technical scheme, comprising the following steps: mixing an anionic surfactant, a cationic surfactant and water to obtain an aqueous solution; heating the aqueous solution to a first temperature, adding an ion regulator, an organic solvent and a non-ionic surfactant, and subjecting the mixture to a first stirring to obtain a first homogeneous solution; heating the first homogeneous solution to a second temperature, adding a zwitterionic surfactant, and subjecting the mixture to a second stirring to obtain the homogeneous microemulsion-type permeation-enhancing oil-displacing agent.

[0048] In the present invention, an anionic surfactant, a cationic surfactant and water are mixed to obtain an aqueous phase solution. The present invention has no particular limitation on the mixing process, and any method known to those skilled in the art can be used.

[0049] After obtaining the aqueous phase solution, the present invention heats the aqueous phase solution to a first temperature, adds an ion regulator, an organic solvent and a non-ionic surfactant, and obtains a first homogeneous solution through a first stirring.

[0050] In the present invention, it is preferred to first stir the ion regulator until it is dissolved, and then add the organic solvent and the nonionic surfactant.

[0051] In the present invention, the first temperature is preferably 60-65°C, specifically 60°C, 61°C, 62°C, 63°C, 64°C or 65°C; the heating is preferably performed by heating in a water bath; the first stirring time is preferably 1-2h. In the present invention, when the aqueous phase further includes a phase transfer agent, the phase transfer agent is preferably added during the first stirring process.

[0052] After obtaining the first homogeneous solution, the present invention heats the first homogeneous solution to a second temperature, adds a zwitterionic surfactant, and obtains the homogeneous microemulsion type permeation-enhancing oil-displacing agent through a second stirring.

[0053] In the present invention, the second temperature is preferably 70-75°C, specifically 70°C, 71°C, 72°C, 73°C, 74°C or 75°C; the heating is preferably performed by heating in a water bath; the second stirring time is preferably 2-4h. In the present invention, when the aqueous phase further includes a surface conditioner, the surface conditioner is preferably added during the second stirring process.

[0054] In the present invention, the homogeneous microemulsion type permeation oil displacement agent prepared by stirring the reaction at a certain temperature for a certain time is a uniform transparent liquid and does not separate after being left for a long time.

[0055] The present invention also provides the use of the homogeneous microemulsion type permeability-enhancing oil displacement agent described in the above technical solution or the homogeneous microemulsion type permeability-enhancing oil displacement agent prepared by the preparation method described in the above technical solution in the exploitation of low-permeability heavy oil reservoirs. In the present invention, by compounding different types of reagents, different formations and different purposes of use can be met, and it has a wide range of uses.

[0056] In the present invention, the use of the homogeneous microemulsion type permeability-enhancing oil displacement agent in the exploitation of low-permeability heavy oil reservoirs preferably includes adjusting the seepage channel of the heterogeneous heavy oil reservoir, and the adjustment preferably includes the following steps:

[0057] According to the geological characteristics of the reservoir, select the appropriate homogeneous microemulsion type permeability-enhancing oil displacement agent;

[0058] The homogeneous microemulsion type permeation-enhancing oil displacement agent is prepared into a 0.1-0.3 wt % homogeneous microemulsion type permeation-enhancing oil displacement agent aqueous solution;

[0059] Injecting the homogeneous microemulsion type permeability-enhancing oil displacement agent aqueous solution into the reservoir through a water injection well to form a micro-foam fluid;

[0060] Different segments of miscible fluid are injected into the well.

[0061] In the present invention, the homogeneous microemulsion type permeation-enhancing oil-displacing agent is used to form microfoam to adjust the seepage channel of the heterogeneous heavy oil reservoir, and the homogeneous microemulsion formed by the high-efficiency imbibition agent is used to improve the wettability of the reservoir, which can repair the permeability of the reservoir, reduce the viscosity of the heavy oil, and improve its fluidity, so as to achieve the purpose of displacing the heavy oil and improving the recovery.

[0062] In the present invention, by injecting a phase microemulsion type permeability-enhancing oil-displacing agent, the seepage capacity of the deep reservoir of low-permeability heavy oil reservoirs can be improved, and the flowability of heavy oil can be further improved by changing the fluidity of crude oil. The imbibition displacement and micro-nano foam displacement can also be combined by utilizing its own characteristics to achieve permeability-adjustment and displacement integration.

[0063] In order to further illustrate the present invention, a homogeneous microemulsion type permeation oil displacement agent provided by the present invention and its preparation method and application are described in detail below in combination with embodiments and application examples, but they should not be construed as limiting the scope of protection of the present invention.

[0064] Example 1

[0065] Add 6 g of anionic surfactant (fatty alcohol polyoxyethylene ether phosphate AEO-7), 6 g of cationic surfactant (14-carbon alkyl glycoside quaternary ammonium salt) and 42 g of water into a 200 mL beaker and mix to obtain an aqueous phase solution, which is placed in a water bath.

[0066] The aqueous phase solution was heated to 65°C in a water bath, 1 g of an ion regulator (sodium chloride) was added, and after stirring until dissolved, 20 g of an organic solvent (terpene), 15 g of a nonionic surfactant (isomeric undecyl alcohol polyoxyethylene ether), and 8 g of a phase transfer agent (alkyl glucoside carboxylate APG0812) were added, and the first homogeneous solution was obtained after stirring and dissolving for 1 hour.

[0067] The first homogeneous solution was heated to 75°C in a water bath, 8 g of a zwitterionic surfactant (CAB-35) and 2.2 g of a surface conditioner (12-carbon fatty alcohol polyoxyethylene ether perfluoro surfactant) were added, and stirred for 2 h to obtain a uniform light yellow liquid, i.e., a homogeneous microemulsion-type permeation oil-displacing agent.

[0068] Example 2

[0069] Add 6 g of anionic surfactant (fatty alcohol polyoxyethylene ether phosphate AEO-9), 8 g of cationic surfactant (14-carbon alkyl glucoside quaternary ammonium salt) and 45 g of water into a 200 mL beaker and mix to obtain an aqueous phase solution, which is placed in a water bath.

[0070] The aqueous phase solution was heated to 65°C in a water bath, 2 g of an ion regulator (potassium chloride) was added, and after stirring until dissolved, 30 g of an organic solvent (terpene), 18 g of a nonionic surfactant (isomeric undecyl alcohol polyoxyethylene ether), and 10 g of a phase transfer agent (alkyl glucoside carboxylate APEG0812) were added, and the first homogeneous solution was obtained after stirring and dissolving for 1 hour.

[0071] The first homogeneous solution was heated to 75°C in a water bath, 10g of a zwitterionic surfactant (CAB-40) and 3g of a surface conditioner (10-carbon fatty alcohol polyoxyethylene ether perfluoro surfactant) were added, and stirred for 2h to obtain a uniform light yellow liquid, i.e., a homogeneous microemulsion-type permeation oil-displacing agent.

[0072] Example 3

[0073] Add 7 g of anionic surfactant (fatty alcohol polyoxyethylene ether phosphate AEO-7), 10 g of cationic surfactant (16-carbon alkyl glycoside quaternary ammonium salt) and 50 g of water into a 200 mL beaker and mix to obtain an aqueous phase solution, which is placed in a water bath.

[0074] The aqueous phase solution was heated to 65°C in a water bath, 3 g of ion regulator (potassium chloride) was added, and after stirring until dissolved, 30 g of organic solvent (the volume ratio of pine oil and terpene was 1:1), 20 g of non-ionic surfactant (isomeric tridecyl alcohol polyoxyethylene ether), and 12 g of phase transfer agent (alkyl glucoside carboxylate APG0812) were added, and the first homogeneous solution was obtained after stirring and dissolving for 1 hour.

[0075] The first homogeneous solution was heated to 75°C in a water bath, 12 g of a zwitterionic surfactant (CAO-40) and 3.5 g of a surface conditioner (10-carbon fatty alcohol polyoxyethylene ether perfluoro surfactant) were added, and stirred for 2 h to obtain a uniform light yellow liquid, i.e., a homogeneous microemulsion-type permeation oil-displacing agent.

[0076] Performance Testing

[0077] Test Example 1

[0078] The particle sizes of the homogeneous microemulsion type permeation oil-displacing agents prepared in Examples 1 to 3 were tested. The test results showed that the particle sizes of the droplets of the homogeneous microemulsion type permeation oil-displacing agents prepared in Examples 1 to 3 were 14 to 20 nm, 10 to 14 nm, and 9 to 14 nm, respectively.

[0079] Test Example 2

[0080] The homogeneous microemulsion type permeation oil-displacing agent prepared in Examples 1 to 3 was formulated into a 0.3% aqueous solution, i.e., a drainage agent, whose surface tensions were 23.34 mN / m (Example 1), 21.58 mN / m (Example 2), and 23.01 mN / m (Example 3), respectively, and the interfacial tension was less than 0.5 mN / m (kerosene).

[0081] Test Example 3

[0082] Pressure reduction and injection increase experiment:

[0083] (1) Experimental instruments and materials

[0084] Experimental instruments: Multifunctional core displacement device, Huaan Instrument / Jiangsu Huaan Scientific Research Instrument Co., Ltd.;

[0085] Experimental materials: dense sandstone core, porosity 9.36%, air permeability 0.24×10 -3 μm 2 , inject water, dehydrate crude oil;

[0086] (2) Experimental methods

[0087] ① Place the core in the holder and install it. Set the confining pressure to 15 MPa and use filtered injection water at a constant flow rate of 0.01 mL / s to displace it. After the flow rate stabilizes, record the pressure and calculate the initial water flooding permeability.

[0088] ② Set the core confining pressure to 15 MPa, and use unfiltered injection water at a constant flow rate of 0.01 mL / s to displace 2 PV. After the flow rate stabilizes, record the pressure and calculate the permeability after injection water damage;

[0089] The injected water is the wastewater sample after treatment at the joint station, which contains crude oil, mechanical impurities, etc., which is easy to cause particle migration damage and Jamin effect damage, and is the main source of high-pressure underinjection in injection wells. The main components are shown in Table 1;

[0090] Table 1 Injection water quality analysis data table

[0091]

[0092] ③ The core was displaced with 0.3% microemulsion solution (aqueous solution prepared from the homogeneous microemulsion type permeability-enhancing oil-displacing agent obtained in Example 2) for 1 PV, and the displacement pressure and flow rate were recorded after the displacement;

[0093] ④ After the microemulsion displacement is completed, the injected water after filtering (the water after the injected water sample is filtered out through filter paper, which is equivalent to the injected water qualified after further treatment of the sewage at the joint station) is used for displacement, and the pressure and flow rate are recorded every 0.5PV. After the flow rate is stable, the pressure is recorded and the permeability recovery rate is calculated;

[0094] (3) Experimental results

[0095] in Figure 1 is the curve of permeability changing with injected volume, Figure 2 It is a curve diagram of injection pressure changing with injection volume;

[0096] It can be seen that the permeability after water injection is 0.124×10 -3 μm 2 The permeability damage rate is 31.1%. After 0.3% microemulsion is used to remove the plugging, the permeability is 0.173×10 -3 μm 2 , the permeability recovery rate was 96.11%, and the displacement pressure dropped by 22.2%.

[0097] Test Example 4

[0098] Enhanced oil recovery experiment:

[0099] (1) Experimental instruments and materials

[0100] Experimental instruments: Meso-MR060-I nuclear magnetic resonance instrument, Changzhou University. Multifunctional core displacement device, Jiangsu Huaan Scientific Research Instrument Co., Ltd.

[0101] Experimental material: sandstone core, permeability 0.241×10 -3 μm 2 , dehydrated crude oil, 31000 mg / L simulated formation water, and the NMR parameters of the sandstone core are shown in Table 2;

[0102] Table 2 Core parameters of NMR experiment

[0103] Sample No. Length / cm Diameter / cm Porosity / % Permeability / mD L1-1 5.00 2.47 11.60 0.307

[0104] (2) Experimental methods

[0105] The core was evacuated in a vacuum box for 30 min and then saturated with crude oil for 3 d. The core was taken out and the excess crude oil on the surface was wiped off, and a nuclear magnetic resonance test was carried out.

[0106] The core saturated with crude oil was placed in an imbibition bottle, and filtered injection water was added to completely immerse the core. It was then placed in a constant temperature box to maintain an environment of 63°C. The readings were recorded every 1 hour until the degree of recovery no longer increased, and a nuclear magnetic resonance test was carried out.

[0107] The core after water injection and imbibition was placed in an imbibition bottle, and 0.3% microemulsion (aqueous solution prepared from the homogeneous microemulsion type permeation oil displacement agent obtained in Example 3) was added to completely immerse the core, and then placed in a constant temperature box to maintain an environment of 63°C. The readings were recorded every 1 hour until the recovery rate no longer increased, and a nuclear magnetic resonance test was carried out.

[0108] The core after microemulsion infiltration was placed in the clamp of the multifunctional core displacement device and displaced with 0.3% microemulsion, a displacement pressure of 3.5 MPa, and a confining pressure of 15 MPa. Data was recorded every 10 minutes until the water saturation was above 95%, and then a nuclear magnetic resonance test was carried out.

[0109] (3) Experimental results

[0110] The test results obtained Figure 3 , Figure 4 As shown in Table 3, Figure 3 NMR T2 spectra at different oil recovery stages; Figure 4 The distribution diagram of pore utilization degree in different oil recovery stages;

[0111] Table 3 Data table of core pore utilization degree under different conditions

[0112]

[0113] It can be seen that after the core is saturated with oil, the T2 spectrum shows a bimodal distribution, and the oil phase is mainly concentrated in the micropores of 0.1-0.3μm and 0.5-1.0μm. The injected water mainly displaces the crude oil in the pores <0.5μm. As the pore radius increases, the capillary force decreases, and the degree of production gradually decreases. The microemulsion mainly imbibes and displaces the remaining oil in the pores of 0.1-1.0μm, and the degree of production increases by 5.70%-10.11%. Microemulsion flooding further improves the flow capacity of the remaining oil in the pores above 0.1μm, and further increases it by 3.65%-6.25% on the basis of microemulsion imbibition displacement. The spontaneous imbibition and displacement of microemulsions increase the degree of production by 12.06%-13.76%.

[0114] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A homogeneous microemulsion type penetration-enhancing oil displacement agent, characterized in that: It comprises an oil phase and a water phase, wherein the oil phase comprises an organic solvent, and the water phase comprises a surfactant, an ion regulator and water; The surfactant includes anionic surfactant, cationic surfactant, nonionic surfactant and zwitterionic surfactant; the nonionic surfactant does not include nonionic polyoxyethylene ether perfluoro surfactant and alkyl glucoside carboxylate.

2. The homogeneous microemulsion type penetration-enhancing oil-displacing agent according to claim 1, characterized in that: The organic solvent includes terpineol and / or terpene; The volume ratio of the oil phase to the water phase is 1:4-5.

3. The homogeneous microemulsion type penetration-enhancing oil-displacing agent according to claim 1, characterized in that: The anionic surfactant includes one or more of fatty alcohol polyoxyethylene ether carboxylates, sodium α-olefin sulfonates and fatty alcohol polyoxyethylene ether phosphates; The cationic surfactant comprises an alkyl glucoside quaternary ammonium salt, wherein the carbon number of the alkyl group in the alkyl glucoside quaternary ammonium salt is 12 to 16; The nonionic surfactant is polyoxyethylene isomeric alcohol ether and / or nonionic betaine; The zwitterionic surfactant includes zwitterionic betaine; The mass ratio of the anionic surfactant, the cationic surfactant, the nonionic surfactant and the zwitterionic surfactant is 5-7:6-10:15-20:8-12.

4. The homogeneous microemulsion type permeation oil displacement agent according to any one of claims 1 to 3, characterized in that: The ion regulator includes sodium chloride and / or potassium chloride; The mass ratio of the anionic surfactant, the ion regulator and water is 6-8:1-3:42-50.

5. The homogeneous microemulsion type penetration-enhancing oil-displacing agent according to claim 1, characterized in that: The water phase also includes a surface conditioner, which is a nonionic polyoxyethylene ether perfluoro surfactant; the mass ratio of the anionic surfactant to the surface conditioner is 6-8:2.2-3.

5.

6. The homogeneous microemulsion type penetration-enhancing oil displacement agent according to claim 1 or 5, characterized in that: The aqueous phase also includes a phase transfer agent, and the phase transfer agent is an alkyl glucoside carboxylate; The mass ratio of the anionic surfactant to the phase transfer agent is 6-8:8-12.

7. The method for preparing the homogeneous microemulsion type permeation-enhancing oil displacement agent according to any one of claims 1 to 6, characterized in that: The following steps are involved: Mixing anionic surfactant, cationic surfactant and water to obtain an aqueous phase solution; The aqueous phase solution is heated to a first temperature, and an ion regulator, an organic solvent and a nonionic surfactant are added and stirred for a first time to obtain a first homogeneous solution; The first homogeneous solution is heated to a second temperature, and a zwitterionic surfactant is added thereto and stirred for a second time to obtain the homogeneous microemulsion type permeation-enhancing oil displacement agent.

8. The preparation method according to claim 7, characterized in that: The first temperature is 60-65°C, and the second temperature is 70-75°C; The first stirring time is 1 to 2 hours, and the second stirring time is 2 to 4 hours.

9. The preparation method according to claim 7, characterized in that: When the aqueous phase further comprises a phase transfer agent, the phase transfer agent is added during the first stirring process; When the water phase further includes a surface conditioner, the surface conditioner is added during the second stirring.

10. Use of the homogeneous microemulsion type permeation-enhancing oil-displacing agent according to any one of claims 1 to 6 or the homogeneous microemulsion type permeation-enhancing oil-displacing agent prepared by the preparation method according to any one of claims 7 to 9 in the exploitation of low-permeability heavy oil reservoirs.

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