Surface-active nano polymer oil-displacing agent as well as preparation method and application thereof

Abstract

The invention discloses a surface active nano polymer oil-displacing agent which comprises a water phase substance and an oil phase substance, and the mass ratio of the water phase substance to the oil phase substance is (0.61-0.93): 1. The water-phase substance comprises deionized water, acrylamide, acrylic acid, an active monomer, sodium p-styrenesulfonate, a pH regulator and an initiator A; the water-phase substance comprises 5 # white oil, sorbitan monooleate, a water-soluble active agent, lauryl alcohol polyoxyethylene ether and an initiator B; the invention also discloses a preparation method and application of the surface-active nano-polymer oil displacement agent, the prepared surface-active nano-polymer oil displacement agent is mixed with water to prepare a solution with the mass concentration of 0.1-0.5%, the solution is injected into a stratum, and after the solution enters an oil reservoir, bridging plugging is utilized and the oil washing efficiency is improved, so that the surface-active nano-polymer oil displacement agent is obtained. The purposes of improving the water flooding swept volume and improving the oil washing efficiency are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of tertiary oil recovery agents in oil fields, and specifically relates to a surface active nano polymer oil displacing agent, a preparation method of the surface active nano polymer oil displacing agent, and an application of the surface active nano polymer oil displacing agent. Background Art

[0002] At present, the development of low-permeability oil fields in China has entered the tertiary oil recovery stage. Tertiary oil recovery is based on water injection to maintain reservoir pressure. It relies on injecting a large amount of new oil-displacing agents to change the physical and chemical properties of fluid viscosity, composition and phase state, thereby improving the recovery rate of crude oil. Anionic surfactant oil-displacing agents are widely used in the field of tertiary oil recovery as new oil-displacing agents due to their low cost and easy synthesis. The promotion and application of "tertiary oil recovery" technology based on injection system has greatly improved the crude oil recovery rate of experimental oil fields, with significant benefits. With the continuous deepening of oil field development, in order to better control the natural decline of oil reservoirs and the increase of water content, oil fields have begun deep water plugging and flooding test implementation and large-scale promotion and application.

[0003] In the development of tertiary oil recovery technology, one of the key factors affecting its speed and efficiency is the use of surfactants, which can improve the water drive effect by blocking pores and cracks to change the water absorption profile. By selecting different surfactants for oil recovery, it is found that nano-surfactants generally have a smaller particle size and a stronger ability to reduce interfacial tension, which plays a great role in improving oil recovery. Nano-surfactants have better oil washing effects on low permeability reservoirs, but with the implementation of multiple rounds of various technologies, subsequent water plugging and flooding are difficult to migrate deep, and the effective period of the continuous expansion of the sweep effect is limited, making it difficult to further improve the effect. At present, surfactants cannot effectively strip the remaining crude oil in the reservoir from the rock surface, and cannot achieve the effect of oil washing. Summary of the invention

[0004] One object of the present invention is to provide a surface active nano polymer oil displacing agent, which solves the problem that the existing oil displacing agent cannot effectively strip the remaining oil on the rock surface.

[0005] Another object of the present invention is to provide a method for preparing the surface active nano polymer oil displacing agent.

[0006] Another object of the present invention is to provide the application of the surface active nano polymer oil displacing agent.

[0007] A technical solution adopted by the present invention is that the surface active nano polymer oil displacement agent comprises water phase material and oil phase material, and the mass ratio of the water phase material to the oil phase material is 0.61-0.93:1.

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

[0009] The following raw materials are weighed respectively according to mass percentage for water phase material and oil phase material: the water phase material comprises 17.98%-25.92% of deionized water, 10.79%-14.40% of acrylamide, 2.25%-2.88% of acrylic acid, 2.98%-5.13% of active monomer, 0.63%-1.36% of sodium p-styrene sulfonate, 1.25%-1.76% of pH regulator, and 0.018%-0.021% of initiator A; the oil phase material comprises 39.36%-45.87% of 5# white oil; 7.97%-11.24% of sorbitan monooleate, 3.19%-4.5% of water-soluble active agent, 0.14%-0.62% of lauryl alcohol polyoxyethylene ether, and 0.022%-0.049% of initiator B, and the total content of the above raw materials is 100%.

[0010] The mass ratio of acrylic acid to pH regulator in the water phase material is 1.79:1; the mass ratio of sorbitan monooleate to water-soluble surfactant in the oil phase material is 2.5:1.

[0011] The active monomer is any one of methacryloyloxyethyl dimethyl ammonium bromide, dimethylaminoethyl methacrylate, or ethyl acrylate trimethyl ammonium chloride; the water-soluble active agent is any one of sorbitan monooleate polyoxyethylene ether Tween80 or fatty alcohol polyoxyethylene ether.

[0012] The initiator A is any one of ammonium persulfate or tert-butyl hydroperoxide; the initiator B is any one of sodium bisulfite with a mass fraction of 50% or sodium metabisulfite with a mass fraction of 30%.

[0013] The pH regulator is NaOH or Na 2 CO 3 One of them.

[0014] Another technical solution adopted by the present invention is a method for preparing a surface active nano polymer oil displacing agent. The surface active nano polymer oil displacing agent is prepared by specifically following the steps below:

[0015] Step 1, preparing water phase material and oil phase material respectively;

[0016] Step 2, mixing the water phase material and the oil phase material prepared in step 1 to obtain a surface active nano polymer oil displacement agent.

[0017] The present invention is also characterized in that the specific process of step 1 is:

[0018] Step 1.1, weigh the water phase material and the oil phase material according to the mass percentage and set aside:

[0019] The following raw materials are weighed respectively according to mass percentage for water phase material and oil phase material: the water phase material comprises 17.98%-25.92% of deionized water, 10.79%-14.40% of acrylamide, 2.25%-2.88% of acrylic acid, 2.98%-5.13% of active monomer, 0.63%-1.36% of sodium p-styrene sulfonate, 1.25%-1.76% of pH regulator, 0.018%-0.021% of initiator A; the oil phase material comprises 39.36%-45.87% of 5# white oil; 7.97%-11.24% of sorbitan monooleate, 3.19%-4.5% of water-soluble active agent, 0.14%-0.62% of lauryl alcohol polyoxyethylene ether, 0.022%-0.049% of initiator B, and the total content of the above raw materials is 100%;

[0020] Step 1.2, preparing aqueous phase material;

[0021] Add deionized water, acrylamide, acrylic acid, active monomer, sodium p-styrene sulfonate to a beaker in sequence, stir until completely dissolved, add a pH adjuster, and finally add initiator A;

[0022] Step 1.3, preparing oil phase material;

[0023] Take another beaker, add 5# white oil, sorbitan monooleate, water-soluble surfactant, and lauryl alcohol polyoxyethylene ether into the beaker in sequence, and mix and stir evenly.

[0024] The specific process of step 2 is: put the oil phase material prepared in step 1 into a three-necked flask and stir it at a stirring speed of 150r / min to 250r / min, then slowly add the water phase material prepared in step 1, stir and emulsify for 10 minutes, then continue to introduce nitrogen for 10 minutes, add initiator B to start the reaction, turn off the nitrogen after the temperature reacts to 70°C, and continue aging for 2 hours to obtain a surface active nano polymer oil displacement agent.

[0025] Another technical solution adopted by the present invention is the application of a surfactant nano polymer oil-displacing agent, wherein the prepared surfactant nano polymer oil-displacing agent is mixed with water to form a solution with a mass concentration of 0.1% to 0.5%, which is then injected into the formation. After entering the oil reservoir, bridging and plugging are performed and the oil washing efficiency is improved, thereby achieving the purpose of improving the water drive swept volume and improving the oil washing efficiency.

[0026] The beneficial effects of the present invention are as follows: the surface active nano polymer oil displacement agent of the present invention can achieve the blocking of reservoir micro cracks and large water flow channels by using conventional profile control agents through adsorption retention, bridging plugging and other methods, and at the same time, a molecular chain group with surface active function is grafted on the surface of the profile control agent, which can effectively strip the remaining oil on the surface of the rock while blocking. After being injected into the formation, the nano-scale material can effectively enter the deep part of the reservoir, change the flow direction of the injected water in the throat or pores through adsorption, retention, bridging plugging and other functions, and has a small particle size, can effectively adsorb, bridge and block the advantageous water flow channels. At the same time, surface active monomers are added during the polymerization process, so that the nano polymer oil displacement agent has the function of washing oil. After being injected into the formation at a mass concentration of 0.1% to 0.5%, the bridging plugging and oil washing energy are used to achieve the purpose of improving the water drive swept volume and improving the oil washing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the inverse emulsion synthesis process principle in step 2 of the preparation method of the surface active nano polymer oil displacement agent of the present invention:

[0028] Figure 2 This is a particle size test chart of the surface active nano polymer oil displacement agent prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with specific implementation modes.

[0030] The surface active nano polymer oil displacing agent of the present invention comprises water phase material and oil phase material, wherein the mass ratio of the water phase material to the oil phase material is 0.61-0.93:1.

[0031] The following raw materials are weighed respectively for water phase material and oil phase material according to mass percentage: the water phase material comprises 17.98%-25.92% of deionized water, 10.79%-14.40% of acrylamide, 2.25%-2.88% of acrylic acid, 2.98%-5.13% of active monomer, 0.63%-1.36% of sodium p-styrene sulfonate, 1.25%-1.76% of pH regulator, and 0.018%-0.021% of initiator A; the oil phase material comprises 39.36%-45.87% of 5# white oil; 7.97%-11.24% of sorbitan monooleate, 3.19%-4.5% of water-soluble active agent, 0.14%-0.62% of lauryl alcohol polyoxyethylene ether, and 0.022%-0.049% of initiator B, and the total content of the above raw materials is 100%.

[0032] The mass ratio of acrylic acid to pH regulator in the aqueous phase is 1.79:1; the mass ratio of sorbitan monooleate to water-soluble surfactant in the oil phase is 2.5:1.

[0033] The pH regulator is NaOH or Na 2 CO 3 One of them.

[0034] The active monomer is any one of methacryloyloxyethyl dimethyl ammonium bromide, dimethylaminoethyl methacrylate, and ethyl acrylate trimethyl ammonium chloride.

[0035] Initiator A is one of ammonium persulfate or tert-butyl hydroperoxide.

[0036] The water-soluble active agent is any one of sorbitan monooleate polyoxyethylene ether Tween80 or fatty alcohol polyoxyethylene ether.

[0037] The initiator B is a sodium bisulfite with a mass fraction of 50% or a sodium metabisulfite with a mass fraction of 30%.

[0038] The preparation method of the surface active nano polymer oil displacing agent of the present invention is specifically implemented according to the following steps:

[0039] Step 1, preparing water phase material and oil phase material respectively;

[0040] Step 1.1, weigh the water phase material and the oil phase material according to the mass percentage and set aside:

[0041] The following raw materials are weighed respectively for water phase material and oil phase material according to mass percentage: the water phase material comprises 17.98%-25.92% of deionized water, 10.79%-14.40% of acrylamide, 2.25%-2.88% of acrylic acid, 2.98%-5.13% of active monomer, 0.63%-1.36% of sodium p-styrene sulfonate, 1.25%-1.76% of pH regulator, and 0.018%-0.021% of initiator A; the oil phase material comprises 39.36%-45.87% of 5# white oil; 7.97%-11.24% of sorbitan monooleate, 3.19%-4.5% of water-soluble active agent, 0.14%-0.62% of lauryl alcohol polyoxyethylene ether, and 0.022%-0.049% of initiator B, and the total content of the above raw materials is 100%.

[0042] Step 1.2, preparing aqueous phase material;

[0043] Deionized water, acrylamide, acrylic acid, active monomers, and sodium p-styrene sulfonate were added to a beaker in sequence, and after stirring until they were completely dissolved, a pH adjuster was added, and finally initiator A was added.

[0044] Step 1.3, preparing oil phase material;

[0045] Take another beaker, add 5# white oil, sorbitan monooleate, water-soluble surfactant, and lauryl alcohol polyoxyethylene ether into the beaker in sequence, and mix and stir evenly.

[0046] Step 2, mixing the water phase material and the oil phase material prepared in step 1 to obtain a surface active nano polymer oil displacement agent.

[0047] The oil phase material prepared in step 1 is placed in a three-necked flask and stirred at a stirring speed of 150 r / min to 250 r / min, and then the water phase material prepared in step 1 is slowly added. After stirring and emulsifying for 10 minutes, nitrogen is continuously introduced for 10 minutes, and then initiator B is added to start the reaction. After the temperature reacts to 70°C, the nitrogen is turned off and aging is continued for 2 hours to obtain a surface active nano polymer oil displacement agent.

[0048] The preparation method of the surface active nano polymer oil displacement agent of the present invention introduces a molecular chain with surface activity into the profile control agent, so that after entering the reservoir, on the one hand, the water absorption profile is changed by blocking the pores and cracks, thereby improving the water drive effect, and on the other hand, the crude oil in the oil reservoir can be effectively stripped to achieve the effect of oil washing. The prepared surface active nano polymer oil displacement agent has strong stability, good injectability, and excellent oil washing efficiency, and can greatly improve the recovery rate of low permeability water drive. The preparation method of the surface active nano polymer oil displacement agent of the present invention has a simple preparation process, mild reaction conditions, and is suitable for industrial production.

[0049] The surface active nano polymer oil displacement agent prepared by the present invention is mixed with water to prepare a solution with a mass concentration of 0.1% to 0.5% and injected into the formation. After entering the oil reservoir, bridging and plugging are used to improve the oil washing efficiency, thereby achieving the purpose of improving the water flooding swept volume and improving the oil washing efficiency.

[0050] Example 1

[0051] The preparation method of the surface active nano polymer oil displacing agent of the present invention is specifically implemented according to the following steps:

[0052] Step 1, preparing water phase material and oil phase material respectively;

[0053] Step 1.1, weigh the water phase material and the oil phase material according to the mass percentage and set aside:

[0054] The following raw materials were weighed separately: aqueous phase material including 200g of deionized water, 120g of acrylamide, 25g of acrylic acid, 57g of methacryloyloxyethyl dimethyl ammonium bromide, 7g of sodium p-styrene sulfonate, 13.9g of NaOH, 0.21g of tert-butyl hydroperoxide, oil phase material including 510g of 5# white oil, 125g of sorbitan monooleate, 50g of dehydrated sorbitan monooleate polyoxyethylene ether Tween80, 3.5g of lauryl alcohol polyoxyethylene ether, and 0.25g of 50% sodium bisulfite by mass.

[0055] Step 1.2, preparing aqueous phase material;

[0056] Deionized water, acrylamide, acrylic acid, methacryloyloxyethyl dimethyl ammonium bromide, and sodium p-styrene sulfonate were added to a beaker in sequence, and after stirring until they were completely dissolved, NaOH was added as a pH adjuster, and finally tert-butyl hydroperoxide was added.

[0057] Step 1.3, preparing oil phase material;

[0058] Take another beaker, add 5# white oil, sorbitan monooleate, sorbitan monooleate polyoxyethylene ether Tween80, and lauryl alcohol polyoxyethylene ether into the beaker in sequence, and mix and stir evenly.

[0059] Step 2, mixing the water phase material and the oil phase material prepared in step 1 to obtain a surface active nano polymer oil displacement agent.

[0060] The oil phase material prepared in step 1 is placed in a three-necked flask and stirred at a stirring speed of 150 r / min, and then the water phase material prepared in step 1 is slowly added. After stirring and emulsifying for 10 minutes, nitrogen is continuously introduced for 10 minutes, and then 50% by mass of sodium bisulfite is added to start the reaction. After the temperature reacts to 70°C, the nitrogen is turned off and aging is continued for 2 hours to obtain a surface active nano polymer oil displacement agent.

[0061] The surface active nano polymer oil displacement agent prepared in Example 1 of the present invention was characterized by physical and chemical indicators using a Malvern laser particle size analyzer, such as Figure 2 As shown, nano-particle size: after dispersion in organic solvents such as n-hexane, the particle size measured is 56.23 nm.

[0062] Surface activity: mineralization degree is 1.933×10 4 0.1% to 0.5% oil displacement agent solution was prepared with 1000 mg / L brine. The oil washing efficiency was determined at 50°C according to the oil washing efficiency determination method in Q / SY 1583-2013. The interfacial tension between the aqueous solution and kerosene was determined according to the spinning drop method in SY / T 5370-1999. The results are shown in Table 1:

[0063] Table 1 shows the oil washing efficiency and interfacial tension at different concentrations

[0064] concentration,% 0.1 0.2 0.3 0.4 0.5 Oil washing efficiency, % 8.57 9.21 10.25 12.27 14.25 Interfacial tension, mN / m 0.581 0.351 0.125 0.072 0.051

[0065] Washing oil efficiency test: After washing with anhydrous ethanol and drying at 85°C for 2 hours, the effective content of the polymer was measured to be 19.27%.

[0066] Example 2

[0067] The preparation method of the surface active nano polymer oil displacing agent of the present invention is specifically implemented according to the following steps:

[0068] Step 1, preparing water phase material and oil phase material respectively;

[0069] Step 1.1, weigh the water phase material and the oil phase material according to the mass percentage and set aside:

[0070] The following raw materials were weighed separately: aqueous phase material including 300g deionized water, 150g acrylamide, 35g acrylic acid, 50g dimethylaminoethyl methacrylate, 15g sodium p-styrene sulfonate, 19.4g Na 2 CO 3 , 0.23g of ammonium persulfate, 480g of 5# white oil, 110g of sorbitan monooleate, 44g of fatty alcohol polyoxyethylene ether, 3.5g of lauryl alcohol polyoxyethylene ether, and 0.54g of 30% sodium metabisulfite.

[0071] Step 1.2, preparing aqueous phase material;

[0072] Add deionized water, acrylamide, acrylic acid, dimethylaminoethyl methacrylate, and sodium p-styrene sulfonate to a beaker in sequence, stir until completely dissolved, and then add Na 2 CO 3 As a pH adjuster, ammonium persulfate was added last.

[0073] Step 1.3, preparing oil phase material;

[0074] Take another beaker, add 5# white oil, sorbitan monooleate, water-soluble surfactant, and lauryl alcohol polyoxyethylene ether into the beaker in sequence, and mix and stir evenly.

[0075] Step 2, mixing the water phase material and the oil phase material prepared in step 1 to obtain a surface active nano polymer oil displacement agent.

[0076] The oil phase material prepared in step 1 is placed in a three-necked flask and stirred at a stirring speed of 180 r / min, and then the water phase material prepared in step 1 is slowly added. After stirring and emulsifying for 10 minutes, nitrogen is continuously introduced for 10 minutes, and then 30% sodium metabisulfite is added to start the reaction. After the temperature reacts to 70°C, the nitrogen is turned off and aging is continued for 2 hours to obtain a surface active nano polymer oil displacement agent.

[0077] The following performance tests were performed on the surface active nano polymer oil displacement agent prepared in Example 2 of the present invention, and the test results were as follows:

[0078] Nano-particle size: After dispersion in organic solvents such as n-hexane, the particle size was measured to be 83.42 nm.

[0079] Surface activity: mineralization degree is 1.933×10 4 0.1% to 0.5% oil displacement agent solution was prepared with 100 mg / L brine. The oil washing efficiency was determined at 50°C according to the oil washing efficiency determination method in Q / SY 1583-2013. The interfacial tension between the aqueous solution and kerosene was determined according to the spinning drop method in SY / T 5370-1999. The results are shown in Table 2:

[0080] Table 2 shows the oil washing efficiency and interfacial tension at different concentrations

[0081] concentration,% 0.1 0.2 0.3 0.4 0.5 Oil washing efficiency, % 8.47 8.58 9.78 11.24 12.36 Interfacial tension, mN / m 0.647 0.487 0.217 0.082 0.068

[0082] Effective content: After washing with anhydrous ethanol and drying at 85°C for 2 hours, the effective content of the polymer was measured to be 20.25%.

[0083] Example 3

[0084] The preparation method of the surface active nano polymer oil displacing agent of the present invention is specifically implemented according to the following steps:

[0085] Step 1, preparing water phase material and oil phase material respectively;

[0086] Step 1.1, weigh the water phase material and the oil phase material according to the mass percentage and set aside:

[0087] The following raw materials were weighed respectively: 230 g of deionized water, 140 g of acrylamide, 27 g of acrylic acid, 40 g of ethyl acrylate trimethylammonium chloride, 8 g of sodium p-styrene sulfonate, 15 g of NaOH, 0.22 g of ammonium persulfate, 430 g of 5# white oil, 100 g of sorbitan monooleate, 40 g of dehydrated sorbitan monooleate polyoxyethylene ether Tween80, 1.5 g of lauryl alcohol polyoxyethylene ether, and 0.47 g of sodium bisulfite.

[0088] Step 1.2, preparing aqueous phase material;

[0089] Deionized water, acrylamide, acrylic acid, ethyl acrylate trimethylammonium chloride, and sodium p-styrene sulfonate were added to a beaker in sequence, and after stirring until they were completely dissolved, NaOH was added as a pH adjuster, and finally ammonium persulfate was added.

[0090] Step 1.3, preparing oil phase material;

[0091] Take another beaker, add 5# white oil, sorbitan monooleate, sorbitan monooleate polyoxyethylene ether Tween80, and lauryl alcohol polyoxyethylene ether into the beaker in sequence, and mix and stir evenly.

[0092] Step 2, mixing the water phase material and the oil phase material prepared in step 1 to obtain a surface active nano polymer oil displacement agent.

[0093] The oil phase material prepared in step 1 is placed in a three-necked flask and stirred at a stirring speed of 200 r / min, and then the water phase material prepared in step 1 is slowly added. After stirring and emulsifying for 10 minutes, nitrogen is continuously introduced for 10 minutes, and then sodium bisulfite is added to start the reaction. After the temperature reacts to 70°C, the nitrogen is turned off and aging is continued for 2 hours to obtain a surface active nano polymer oil displacement agent.

[0094] The following performance tests were performed on the surface active nano polymer oil displacement agent prepared in Example 3, and the test results were as follows:

[0095] Nano-particle size: After dispersion in organic solvents such as n-hexane, the particle size was measured to be 125.61 nm.

[0096] Surface activity: mineralization degree is 1.933×10 4 0.1% to 0.5% oil displacement agent solution was prepared with 100 mg / L brine. The oil washing efficiency was determined at 50°C according to the oil washing efficiency determination method in Q / SY 1583-2013. The interfacial tension between the aqueous solution and kerosene was determined according to the spinning drop method in SY / T 5370-1999. The results are shown in Table 3:

[0097] Table 3 shows the oil washing efficiency and interfacial tension at different concentrations

[0098] concentration,% 0.1 0.2 0.3 0.4 0.5 Oil washing efficiency, % 7.25 7.98 8.59 9.75 10.27 Interfacial tension, mN / m 0.824 0.579 0.318 0.107 0.080

[0099] An effective content analysis test was conducted: after washing with anhydrous ethanol and drying at 85°C for 2 hours, the effective content of the polymer was measured to be 20.87%.

[0100] Example 4

[0101] The preparation method of the surface active nano polymer oil displacing agent of the present invention is specifically implemented according to the following steps:

[0102] Step 1, preparing water phase material and oil phase material respectively;

[0103] Step 1.1, weigh the water phase material and the oil phase material according to the mass percentage and set aside:

[0104] Weigh the following raw materials separately: 270g of deionized water, 150g of acrylamide, 30g of acrylic acid, 31g of ethyl acrylate trimethylammonium chloride, 10.7g of sodium p-styrene sulfonate, and stir until they are completely dissolved. Then add 16.67g of Na 2 CO 3 , 0.22g of ammonium persulfate; 410g of 5# white oil; 83g of sorbitan monooleate, 33.2g of fatty alcohol polyoxyethylene ether, 6.5g of lauryl alcohol polyoxyethylene ether, and 1.4g of 30% sodium metabisulfite.

[0105] Step 1.2, preparing aqueous phase material;

[0106] Add deionized water, acrylamide, acrylic acid, ethyl acrylate trimethylammonium chloride, and sodium p-styrene sulfonate to a beaker in sequence, stir until completely dissolved, and then add Na 2 CO 3 As a pH adjuster, ammonium persulfate was added last.

[0107] Step 1.3, preparing oil phase material;

[0108] Take another beaker, add 5# white oil, sorbitan monooleate, fatty alcohol polyoxyethylene ether, and lauryl alcohol polyoxyethylene ether into the beaker in sequence, and mix and stir evenly.

[0109] Step 2, mixing the water phase material and the oil phase material prepared in step 1 to obtain a surface active nano polymer oil displacement agent.

[0110] The oil phase material prepared in step 1 is placed in a three-necked flask and stirred at a stirring speed of 250 r / min, and then the water phase material prepared in step 1 is slowly added. After stirring and emulsifying for 10 minutes, nitrogen is continuously introduced for 10 minutes, and then 30% sodium metabisulfite is added to start the reaction. After the temperature reacts to 70°C, the nitrogen is turned off and aging is continued for 2 hours to obtain a surface active nano polymer oil displacement agent.

[0111] The following performance tests were performed on the surface active nano polymer oil displacement agent prepared in Example 4 of the present invention, and the test results were as follows:

[0112] Nano-particle size: The particle size measured after dispersion in organic solvents such as n-hexane is 235.1 nm.

[0113] Surface activity: mineralization degree is 1.933×10 40.1% to 0.5% oil displacement agent solution was prepared with 100 mg / L brine. The oil washing efficiency was determined at 50°C according to the oil washing efficiency determination method in Q / SY 1583-2013. The interfacial tension between the aqueous solution and kerosene was determined according to the spinning drop method in SY / T 5370-1999. The results are shown in Table 4:

[0114] Table 4 Oil washing efficiency and interfacial tension at different concentrations

[0115] concentration,% 0.1 0.2 0.3 0.4 0.5 Oil washing efficiency, % 5.47 6.21 6.55 6.89 7.35 Interfacial tension, mN / m 0.923 0.725 0.458 0.248 0.125

[0116] Effective content: After washing with anhydrous ethanol and drying at 85°C for 2 hours, the effective content of the polymer was measured to be 21.28%.

[0117] From the above four examples, it can be seen that the oil-displacing agent prepared by the method for low interfacial tension nano polymer oil-displacing agent provided by the present invention is a nano-scale polymer, which has a low interfacial tension at 50°C and 1.933×10 4 mg / L mineralization, the oil-water interfacial tension can be effectively reduced and the oil washing efficiency can be improved. Therefore, a surface-active nano polymer oil-displacing agent provided by the present invention is added with a surface-active monomer during the preparation process, so that the oil-displacing agent has small particle size, low interfacial tension characteristics and oil washing ability, and enters the deep part of the oil reservoir with the injected water, and then deeply bridges and blocks, and enhances the oil-water interface effect, so as to achieve the purpose of improving the recovery rate.

[0118] The preparation method of the surface active nano polymer oil displacement agent of the present invention adds a surface active monomer during the preparation process, so that the oil displacement agent has small particle size, low interfacial tension characteristics and oil washing ability, and enters the deep part of the oil reservoir with the injected water, and then deeply passes through bridging and plugging, and enhances the oil-water interface effect, so as to achieve the purpose of improving the recovery rate. The prepared surface active nano polymer oil displacement agent has strong stability, good injectability, and excellent oil washing efficiency, and can greatly improve the low permeability water drive recovery rate. The preparation process is simple, the reaction conditions are mild, and it is suitable for industrial production.

Claims

1. Surface active nano polymer oil displacement agent, It is characterized in that It includes water phase material and oil phase material, and the mass ratio of the water phase material to the oil phase material is 0.61-0.93:

1.

2. The surface active nano polymer oil displacing agent according to claim 1, It is characterized in that The following raw materials are weighed respectively for water phase material and oil phase material according to mass percentage: the water phase material comprises 17.98%-25.92% of deionized water, 10.79%-14.40% of acrylamide, 2.25%-2.88% of acrylic acid, 2.98%-5.13% of active monomer, 0.63%-1.36% of sodium p-styrene sulfonate, 1.25%-1.76% of pH regulator, and 0.018%-0.021% of initiator A; the oil phase material comprises 39.36%-45.87% of 5# white oil; 7.97%-11.24% of sorbitan monooleate, 3.19%-4.5% of water-soluble active agent, 0.14%-0.62% of lauryl alcohol polyoxyethylene ether, and 0.022%-0.049% of initiator B, and the total content of the above raw materials is 100%.

3. The surface active nano polymer oil displacing agent according to claim 2, It is characterized in that The mass ratio of acrylic acid to pH regulator in the water phase material is 1.79:1; the mass ratio of sorbitan monooleate to water-soluble surfactant in the oil phase material is 2.5:

1.

4. The surface active nano polymer oil displacing agent according to claim 2, It is characterized in that The active monomer is any one of methacryloyloxyethyl dimethyl ammonium bromide, dimethylaminoethyl methacrylate, or ethyl acrylate trimethyl ammonium chloride; the water-soluble active agent is any one of sorbitan monooleate polyoxyethylene ether Tween80 or fatty alcohol polyoxyethylene ether.

5. The surface active nano polymer oil displacing agent according to claim 2, It is characterized in that The initiator A is any one of ammonium persulfate or tert-butyl hydroperoxide; the initiator B is any one of sodium bisulfite with a mass fraction of 50% or sodium metabisulfite with a mass fraction of 30%.

6. The surface active nano polymer oil displacing agent according to claim 2, It is characterized in that The pH regulator is NaOH or Na 2 CO 3 One of them.

7. A method for preparing a surface active nano polymer oil displacing agent, comprising preparing the surface active nano polymer oil displacing agent according to claim 1, It is characterized in that Follow the steps below to implement it: Step 1, preparing water phase material and oil phase material respectively; Step 2, mixing the water phase material and the oil phase material prepared in step 1 to obtain a surface active nano polymer oil displacement agent.

8. The method for preparing the surface active nano polymer oil displacing agent according to claim 7, It is characterized in that The specific process of step 1 is as follows: Step 1.1, weigh the water phase material and the oil phase material according to the mass percentage and set aside: The following raw materials are weighed respectively according to mass percentage for water phase material and oil phase material: the water phase material comprises 17.98%-25.92% of deionized water, 10.79%-14.40% of acrylamide, 2.25%-2.88% of acrylic acid, 2.98%-5.13% of active monomer, 0.63%-1.36% of sodium p-styrene sulfonate, 1.25%-1.76% of pH regulator, and 0.018%-0.021% of initiator A; the oil phase material comprises 39.36%-45.87% of 5# white oil; 7.97%-11.24% of sorbitan monooleate, 3.19%-4.5% of water-soluble active agent, 0.14%-0.62% of lauryl alcohol polyoxyethylene ether, and 0.022%-0.049% of initiator B, and the total content of the above raw materials is 100%; Step 1.2, preparing aqueous phase material; Add deionized water, acrylamide, acrylic acid, active monomer, sodium p-styrene sulfonate to a beaker in sequence, stir until completely dissolved, add a pH adjuster, and finally add initiator A; Step 1.3, preparing oil phase material; Take another beaker, add 5# white oil, sorbitan monooleate, water-soluble surfactant, and lauryl alcohol polyoxyethylene ether into the beaker in sequence, and mix and stir evenly.

9. The method for preparing the surface active nano polymer oil displacing agent according to claim 8, It is characterized in that The specific process of step 2 is: putting the oil phase material prepared in step 1 into a three-necked flask and stirring at a stirring speed of 150 r / min to 250 r / min, then slowly adding the water phase material prepared in step 1, stirring and emulsifying for 10 minutes, and then continuously introducing nitrogen for 10 minutes, adding initiator B to start the reaction, and after the temperature reacts to 70° C., turning off the nitrogen, and continuously aging for 2 hours to obtain a surface active nano polymer oil displacement agent.

10. Application of a surface-active nano polymer oil-displacing agent, comprising mixing the surface-active nano polymer oil-displacing agent prepared according to claim 6 with water to prepare a solution with a mass concentration of 0.1% to 0.5%, injecting the solution into a formation, and after entering an oil reservoir, utilizing bridging to seal and improve the oil washing efficiency, thereby achieving the purpose of improving the water flooding swept volume and improving the oil washing efficiency.

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