Oil-displacing agent for high-temperature and high-salt adaptive fracturing as well as preparation method and application of oil-displacing agent

Abstract

The invention discloses an oil-displacing agent for high-temperature and high-salt adaptive fracturing as well as a preparation method and application thereof. The oil-displacing agent comprises deionized water, a compound surfactant, nano silicon dioxide particles modified by a silane coupling agent, an AM / AMPS (acrylamide / 2-acrylamido-2-methylpropanesulfonic acid) copolymerized thickener and an inorganic salt aid, the mass ratio of the deionized water to the compound surfactant to the nano silicon dioxide particles modified by the silane coupling agent to the AM / AMPS copolymerized thickening agent to the inorganic salt additive is (57-65): (15-20): (10-15): (10-15): (5-8). According to the invention, the oil-water interfacial tension is reduced to 1 * 10 <-3 > mN / m through the synergistic effect of the surfactant, and the biodegradation rate is improved through the introduction of trehalose lipid; by introducing the AM / AMPS copolymerized thickening agent and the silane coupling agent modified nano silicon dioxide, the oil-displacing agent has good temperature resistance and salt resistance, the rock wettability is improved, the oil-displacing agent is stable at high temperature, and the dual effects of fracturing transformation and oil displacement are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield exploitation, in particular to a high-temperature and high-salt adaptive fracturing oil displacement agent, a preparation method and application thereof, and is especially suitable for improving the oil recovery of low-permeability oil reservoirs. BACKGROUND

[0002] In the middle and later stages of oilfield development, the exploitation of complex oil reservoirs such as low-permeability, high-temperature and high-salt becomes a major challenge. Such oil reservoirs usually have the characteristics of low permeability, high formation temperature and high salinity, and the conventional oil displacement agent faces serious technical bottlenecks. In the prior art, partially hydrolyzed polyacrylamide thickening agents are prone to amide group hydrolysis in high-temperature and high-salt environments, resulting in a viscosity retention rate of less than 50%, which cannot effectively improve the mobility ratio; surfactant-based oil displacement agents can reduce the interfacial tension, but are prone to salting out under high salinity, and the biodegradation rate of traditional chemical surfactants is generally less than 30%, which poses an environmental pollution risk; and nano-particle additives have poor dispersion stability at high temperatures, making it difficult to form a long-acting wettability regulation effect.

[0003] In addition, the oil displacement agents commonly used in oilfields have the problem of single function. For example, surfactant-based oil displacement agents mainly improve oil displacement efficiency by reducing oil-water interfacial tension, but have limited effect on improving the wettability of oil reservoir rocks and increasing the energy of the formation; polymer-based oil displacement agents can increase the viscosity of the injected fluid and improve the mobility ratio, but have poor temperature and salt resistance and are prone to degradation in high-temperature and high-salt reservoirs. In addition, the existing oil displacement agents cannot well synergize with fracturing fluids during fracturing, and cannot fully exert the dual effects of fracturing modification and oil displacement, resulting in unsatisfactory stimulation and injection effects of oil wells after fracturing, and limited improvement in oil recovery. Moreover, layering and precipitation often occur during fracturing operations. Therefore, it is of great practical significance to develop a multifunctional fracturing oil displacement agent with temperature and salt resistance, biodegradability and functional synergy.

[0004] Glossary: AEO: fatty alcohol polyoxyethylene ether.

[0005] AOS: sodium alpha-olefin sulfonate.

[0006] HAS: sodium heavy alkyl benzene sulfonate. SUMMARY

[0007] To solve the above technical problems, the present application provides a high-temperature and high-salt adaptive fracturing oil displacement agent, a preparation method and application thereof.

[0008] The object of the present application is achieved by the following technical solutions: The oil displacement agent for high-temperature and high-salt adaptive fracturing comprises deionized water, a compounded surfactant, nano-silicon dioxide particles modified by a silane coupling agent, AM / AMPS copolymer thickener, and inorganic salt additives; the mass ratio of the deionized water, the compounded surfactant, the nano-silicon dioxide particles modified by the silane coupling agent, the AM / AMPS copolymer thickener, and the inorganic salt additives is 57-65:15-20:10-15:10-15:5-8; The compounded surfactant comprises non-ionic surfactants, anionic surfactants, and biological surfactants; the mass ratio of the non-ionic surfactants, the anionic surfactants, and the biological surfactants is 1.5-2:2:1.5-1.8. The inorganic salt additives comprise sodium chloride, calcium chloride, and sodium citrate; the mass ratio of the sodium chloride, the calcium chloride, and the sodium citrate is 2-3:2:1-1.2.

[0009] Further improvement, the non-ionic surfactant is AEO, the anionic surfactant is AOS or HAS, and the biological surfactant is a trehalose lipid surfactant.

[0010] Further improvement, the AEO is AEO-9, and the anionic surfactant is AOS.

[0011] Further improvement, the pH value of the oil displacement agent is 7.2-7.5.

[0012] Further improvement, the particle size of the nano-silicon dioxide particles modified by the silane coupling agent ranges from 20 nm to 50 nm.

[0013] A preparation method of the oil displacement agent for high-temperature and high-salt adaptive fracturing, comprising the following steps: Step one, adding deionized water in a reaction kettle, starting a stirrer, controlling the temperature at 45 ℃, adding a compounded surfactant, and stirring for the first time; Step two, adding nano-silicon dioxide particles modified by a silane coupling agent, and stirring for the second time; Step three, adding AM / AMPS copolymer thickener with a degree of resolution of 35% and a molecular weight of 12 million and inorganic salt additives, heating to 55 ℃, and stirring for the third time; Step four, adding sodium hydroxide to adjust the pH value to 7.2-7.5, cooling to 30 ℃, stirring for the fourth time, and obtaining the oil displacement agent for high-temperature and high-salt adaptive fracturing.

[0014] Further improvement, the first stirring time is 20 min-25 min; and the second stirring time is 20 min. The third stirring time is 55-60 min; and the fourth stirring time is 15-20 min.

[0015] Further improvement, the preparation method of the silane coupling agent modified nano-silica particles is as follows: Anhydrous ethanol and nano-silica are mixed and uniformly dispersed at a mass ratio of 21.5:1 to obtain a nano-silica / anhydrous ethanol mixed solution; then silane coupling agent is weighed, and the mass ratio of the nano-silica to the silane coupling agent is 6:1; after the silane coupling agent and water are mixed and uniformly stirred at a mass ratio of 1:1.5, they are added to the nano-silica / anhydrous ethanol mixed solution, heated to 70 DEG C, and reacted for 2-3 h; after the reaction is completed, the filter cake is washed with anhydrous ethanol for several times until the filtrate is clear, and the filter cake is vacuum dried at 80-120 DEG C for 6 h; and the silane coupling agent modified nano-silica particles are obtained after crushing.

[0016] The application of the high-temperature and high-salt adaptive fracturing oil displacement agent to the preparation of the fracturing fluid can improve the oil recovery rate.

[0017] The application has the following beneficial effects: 1. The application uses a polymer and a surfactant to form a compound, uses an AM / AMPS copolymer as a thickening agent, and uses a non-ionic surfactant, an anionic surfactant, and a biological surfactant to form a compound. AM / AMPS copolymer: temperature-resistant and salt-resistant copolymer thickening system, which resists salt ion shielding through the steric hindrance effect of sulfonic acid groups, solves the problem of polymer degradation failure under high temperature and high salt, and the viscosity retention rate is increased to more than 82% after aging for 60 days.

[0018] Surfactant synergistic mechanism: innovative compound of polyoxyethylene ether, sulfonate, and trehalose lipid biological surfactant (mass ratio 1.5-2:2:1.5-1.8), which can reduce the oil-water interfacial tension to 1*10-3 mN / m, and increase the biodegradation rate to 61%.

[0019] Silane coupling agent modified nano-silica: forms a hydrogen bond with the copolymer thickening agent, constructs a long-acting adsorption layer, improves the wettability of the rock, changes the oil-wet property of the rock surface to water-wet property, is conducive to the displacement of crude oil, and maintains stability at high temperature.

[0020] 2. The application uses a gradient temperature control preparation process, uses a 45 DEG C pre-dispersion, and uses a stepwise temperature control mode of 55 DEG C crosslinking activation, which protects the activity of the biological surfactant and promotes the uniform dispersion of the nano-silica particles, and solves the problem of inactivation of the components caused by high-temperature preparation.

[0021] 3、The oil displacement agent of the present application can effectively reduce the oil-water interfacial tension, improve the wettability of the oil reservoir rock, improve the formation energy, and has good compatibility with the fracturing fluid, so that the oil recovery can be significantly improved; in addition, the preparation method of the oil displacement agent is provided, the method is simple in operation, low in cost and suitable for industrial production; finally, the application of the oil displacement agent in oil field fracturing exploitation is provided to solve the problems in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0022] The present application is further described with reference to the accompanying drawings, but the content of the drawings does not constitute any limitation on the present application.

[0023] Figure 1 The zeta potential of the oil displacement agent for fracturing prepared for Example 3 versus temperature.

[0024] Figure 2 The interfacial tension of the oil displacement agent for fracturing prepared for Example 3 versus time at different concentrations.

[0025] Figure 3 The oil displacement effect diagram of the oil displacement agent for fracturing prepared for Example 3. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below with reference to the accompanying drawings and examples.

[0027] The preparation method of the nano-silica particles modified by the silane coupling agent in the present application is as follows: anhydrous ethanol and nano-silica are mixed and uniformly dispersed according to a mass ratio of 21.5:1 to obtain a nano-silica / anhydrous ethanol mixed solution; then, the silane coupling agent is weighed, and the mass ratio of the nano-silica to the silane coupling agent is 6:1; the silane coupling agent and water are mixed and uniformly stirred according to a mass ratio of 1:1.5, and then added to the nano-silica / anhydrous ethanol mixed solution, heated to 70℃, and reacted for 2-3h; after the reaction is completed, the filter cake is washed with anhydrous ethanol for several times until the filtrate is clear, and then the filter cake is vacuum dried at 80-120℃ for 6h, and then crushed to obtain the nano-silica particles modified by the silane coupling agent.

[0028] Example 1 A high-temperature and high-salt adaptive oil displacement agent for fracturing is prepared by the method. 65 kg of deionized water is added to a reaction kettle, a stirrer is started to stir at a speed of 300 r / min, and the temperature is controlled at 45℃. 15 kg of AEO-9, AOS and trehalose lipid biosurfactant compound are added according to a mass ratio of 1.5:2:1.5, and stirred for 20 min.

[0029] Add 10 kg of nano-silica particles with a particle size of 20-50 nm and modified by silane coupling agent, stir for 20 min.

[0030] Add 10 kg of AM / AMPS copolymer thickener with a hydrolysis degree of 25% and a molecular weight of 8 million, 5 kg of inorganic salt adjuvant of sodium chloride, calcium chloride and sodium citrate mixed at a mass ratio of 2:2:1, heat to 55 ℃, continue to stir for 60 min.

[0031] (4) Add 2 kg of sodium hydroxide to adjust the pH value to 7.2, cool to 30 ℃, stir for 15 min, and get the oil displacement agent for high temperature and high salt adaptive fracturing.

[0032] Application: The prepared oil displacement agent is added to the fracturing fluid at a mass concentration of 1%, and a fracturing fluid system containing the oil displacement agent is prepared for fracturing construction in another low permeability reservoir. After construction, the oil recovery of the reservoir is increased by 20%.

[0033] Example 2 A high-temperature and high-salt adaptive fracturing oil displacement agent is prepared by the method: (1) Add 57 kg of deionized water to the reaction kettle, start the stirrer, stir at a speed of 300 r / min, and control the temperature at 45 ℃. Add 18 kg of AEO-9, AOS and trehalose lipid biosurfactant at a mass ratio of 2:2:1.5, and stir for 25 min.

[0034] (2) Add 13 kg of nano-silica particles with a particle size of 20-50 nm and modified by silane coupling agent, stir for 20 min.

[0035] (3) Add 15 kg of AM / AMPS copolymer thickener with a hydrolysis degree of 35% and a molecular weight of 120 million, 7 kg of inorganic salt adjuvant of sodium chloride, calcium chloride and sodium citrate mixed at a mass ratio of 3:2:1, heat to 55 ℃, continue to stir for 55 min.

[0036] (4) Add 2 kg of sodium hydroxide to adjust the pH value to 7.5, cool to 30 ℃, stir for 20 min, and get the oil displacement agent for high temperature and high salt adaptive fracturing. Application: The prepared oil displacement agent is added to the fracturing fluid at a mass concentration of 1.5%, and a fracturing fluid system containing the oil displacement agent is prepared for fracturing construction in another low permeability reservoir. After construction, the oil recovery of the reservoir is increased by 21%.

[0037] Example 3 A high-temperature and high-salt adaptive fracturing oil displacement agent is prepared by the method: (1) Add 57 kg of deionized water to the reaction kettle, start the stirrer, stir at a speed of 300 r / min, and control the temperature at 45 ℃. Add 20 kg of AEO-9, AOS and trehalose lipid biosurfactant in a mass ratio of 2:2:1.8, and stir for 25 min.

[0038] (2) Add 15 kg of nano-silicon dioxide particles with a particle size of 20-50 nm and modified by silane coupling agent, and stir for 20 min.

[0039] (3) Add 15 kg of AM / AMPS copolymer thickener with a hydrolysis degree of 35% and a molecular weight of 12 million, 8 kg of sodium chloride, calcium chloride and sodium citrate inorganic salt adjuvant mixed in a mass ratio of 3:2:1.2, heat to 55 ℃, and continue to stir for 55 min.

[0040] (4) Add 2 kg of sodium hydroxide to adjust the pH value to 7.5, cool to 30 ℃, and stir for 20 min to obtain the oil displacement agent for high temperature and high salt adaptability fracturing. Application: The prepared oil displacement agent is added to the fracturing fluid at a mass concentration of 2%, and a fracturing fluid system containing the oil displacement agent is prepared for fracturing operation in another low permeability reservoir. After the operation, the oil recovery of the reservoir is increased by 25%.

[0041] Comparative Example 1 The difference between this comparative example and Example 3 is that this comparative example uses an equal amount of AEO-7 instead of AEO-9.

[0042] Comparative Example 2 The difference between this comparative example and Example 3 is that this comparative example uses an equal amount of HAS instead of AOS.

[0043] The ability of Example 3 and Comparative Examples 1 and 2 to increase the oil recovery is shown in Table 1.

[0044] Table 1 Example 3 Comparative Example 1 Comparative Example 2 Mass concentration of oil displacement agent (%) 2 2 2 Crude oil recovery enhancement ability (%) 25 20 17 Among them, the oil displacement agent prepared by Example 3, Comparative Example 1 and Comparative Example 2 increases the oil recovery by 25%, 20% and 17% respectively.

[0045] Summary: As can be seen from Table 1, the ability of the oil displacement agent prepared by AEO-9, AOS and trehalose lipid biosurfactant in Example 3 to increase the oil recovery is better than that of the oil displacement agent prepared by AEO-7, AOS and trehalose lipid biosurfactant and the oil displacement agent prepared by AEO-9, HAS and trehalose lipid biosurfactant.

[0046] It should be pointed out finally that the above embodiments are only used for illustrating the technical solutions of the present application but not for limiting the protection scope of the present application, and although the present application has been described in detail with reference to the preferred embodiments, it should be appreciated by those skilled in the art that the technical solutions of the present application can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present application.

Claims

1. An oil displacing agent for high temperature high salt adaptive fracturing, characterized by, Deionized water, complex agent surfactant, nano-silica particles modified by silane coupling agent, AM / AMPS copolymer thickening agent and inorganic salt auxiliary agent; the mass ratio of deionized water, complex agent surfactant, nano-silica particles modified by silane coupling agent, AM / AMPS copolymer thickening agent and inorganic salt auxiliary agent is 57-65:15-20:10-15:10-15:5-8; The complex agent surfactant comprises non-ionic surfactant, anionic surfactant and biological surfactant; the mass ratio of non-ionic surfactant, anionic surfactant and biological surfactant is 1.5-2:2:1.5-1.8; The inorganic salt auxiliary agent comprises sodium chloride, calcium chloride and sodium citrate; the mass ratio of sodium chloride, calcium chloride and sodium citrate is 2-3:2:1-1.

2.

2. The oil displacing agent for high-temperature high-salinity adaptive fracturing according to claim 1, wherein, The non-ionic surfactant is AEO, the anionic surfactant is AOS or HAS, and the biological surfactant is trehalose lipid surfactant.

3. The oil displacing agent for high-temperature high-salinity adaptive fracturing according to claim 2, wherein The AEO is AEO-9, and the anionic surfactant is AOS.

4. The oil displacing agent for high-temperature high-salinity adaptive fracturing according to claim 1, wherein The pH value of the oil displacement agent is 7.2-7.

5.

5. The oil displacing agent for high-temperature high-salinity adaptive fracturing according to claim 1, wherein The particle size of the nano-silica particles modified by silane coupling agent ranges from 20 nm to 50 nm.

6. A method of preparing a high-temperature high-salinity adaptive fracturing oil displacement agent as claimed in any one of claims 1 to 5, characterized in that, The method comprises the following steps: Step one, adding deionized water in a reaction kettle, starting the stirrer, controlling the temperature at 45 DEG C, adding complex agent surfactant, and stirring for the first time; Step two, adding nano-silica particles modified by silane coupling agent, and stirring for the second time; Step three, adding AM / AMPS copolymer thickening agent with a degree of resolution of 35% and a molecular weight of 12 million and inorganic salt auxiliary agent, heating to 55 DEG C, and stirring for the third time; Step four, adding sodium hydroxide to adjust the pH value to 7.2-7.5, cooling to 30 DEG C, stirring for the fourth time, and obtaining the oil displacement agent for high-temperature and high-salt adaptability fracturing.

7. The method for preparing an oil displacing agent for high-temperature high-salinity adaptive fracturing according to claim 6, characterized by, The first stirring time is 20 min-25 min; the second stirring time is 20 min; The third stirring time is 55 min-60 min; and the fourth stirring time is 15-20 min.

8. The method for preparing an oil displacing agent for high-temperature high-salinity adaptive fracturing according to claim 6, characterized by, The preparation method of the nano-silica particles modified by silane coupling agent is as follows: Anhydrous ethanol and nano-silica are mixed and uniformly dispersed according to a mass ratio of 21.5:1 to obtain a nano-silica / anhydrous ethanol mixed solution; then, silane coupling agent is weighed, and the mass ratio of the nano-silica to the silane coupling agent is 6:1; the silane coupling agent and water are mixed and uniformly stirred according to a mass ratio of 1:1.5, and then added to the nano-silica / anhydrous ethanol mixed solution, heated to 70 DEG C, reacted for 2-3 h, washed with anhydrous ethanol for multiple times until the filtrate is clear, and the filter cake is vacuum dried at 80-120 DEG C for 6 h, and then crushed to obtain the nano-silica particles modified by silane coupling agent.

9. Use of the oil displacement agent for high-temperature and high-salinity adaptive fracturing according to any one of claims 1-5, characterized in that, The oil displacement agent for high-temperature and high-salt adaptability fracturing is used to be added into a fracturing fluid at a mass concentration of 1%-2% to improve the oil recovery.

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