Green microcapsule oil-displacing agent based on gelatin / sodium alginate as well as preparation method and application of green microcapsule oil-displacing agent

Abstract

The invention discloses a green microcapsule oil-displacing agent based on gelatin / sodium alginate as well as a preparation method and application of the green microcapsule oil-displacing agent. A wall material of the microcapsule oil-displacing agent consists of gelatin and sodium alginate, and a core material of the microcapsule oil-displacing agent is a hydrophilic surfactant; the preparation method comprises the following steps: (1) dissolving gelatin and sodium alginate in ultrapure water at 40-50 DEG C, stirring until the gelatin and the sodium alginate are dissolved, adjusting the pH value of a system to 3.5-4.7, adding a hydrophilic surfactant solution into the system in a stirring state, and reacting; (2) in a stirring state, adding a tea polyphenol solution into the reaction product in the step (1), reacting at 40-50 DEG C for 0.5-1.5 hours, then adjusting the pH value of the system to 3.9-10, standing and solidifying at 20-30 DEG C, and centrifuging to obtain a solidified liquid reaction product; and (3) drying. The obtained microcapsule has good dispersibility, stability and controllable release performance, and can effectively reduce the oil-water interfacial tension and improve the crude oil recovery rate.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction technology, and specifically relates to a green microcapsule oil displacement agent based on gelatin / sodium alginate, its preparation method and application. Background Technology

[0002] As one of the most important energy sources in modern society, the efficiency of petroleum extraction directly impacts energy supply and economic development. With the gradual depletion of easily recoverable oil and gas resources, oilfields are generally entering a high water-cut development stage, leading to increasingly prominent problems such as enhanced reservoir heterogeneity, dispersed residual oil, and declining recovery rates. Against this backdrop, chemical flooding has become an important technical means to improve oil recovery. Among these, surfactant flooding can significantly reduce oil-water interfacial tension and improve wettability, thereby utilizing difficult-to-recover residual oil, and has promising application prospects.

[0003] However, traditional surfactant flooding has many shortcomings: surfactants are easily adsorbed by rocks or prematurely extracted with water during injection, resulting in insufficient effective concentrations in deep reservoirs and unsatisfactory oil displacement effects. Especially in complex reservoir environments with high temperature, high salinity, and strong heterogeneity, the stability and oil displacement performance of surfactants decrease significantly, limiting oil displacement efficiency.

[0004] To address the aforementioned issues, microencapsulation technology has been introduced into oil displacement systems. By encapsulating surfactants within polymeric wall materials, delayed release and targeted action of the surfactants in the target area can be achieved, thereby improving their utilization and extending the duration of action. In existing microencapsulation systems, the wall material and core material often have different hydrophilic / hydrophobic balances: typically, the wall material is more hydrophilic, while the core material (surfactant or oil-phase active substance) is relatively hydrophobic. Although such designs can form a certain core-shell structure, they are prone to the following problems in oil displacement applications: (1) The large difference between hydrophilic and hydrophobic properties leads to instability of the capsule interface in the aqueous system, which can easily cause premature rupture or leakage of the core material. (2) In high mineralization and high temperature environments, the interfacial compatibility between the wall material and the core material is poor, resulting in low encapsulation rate and uneven release process; (3) During the migration process in the reservoir pores, the capsule is prone to lose its integrity due to phase separation or interface mismatch, which reduces the deep oil displacement effect.

[0005] Therefore, how to design a green microcapsule system with matching hydrophilicity of wall material and core material, and improve its stability and controllable release performance under reservoir conditions, is a key problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a hydrophilic-hydrophilic matched green microcapsule system using a compound of gelatin (GEL) and sodium alginate (SA) as the wall material and a surfactant of similar hydrophilicity as the core material. This overcomes the poor stability of traditional hydrophilic-hydrophobic structures in aqueous environments. By controlling the pH to induce the self-assembly of the wall and core materials, and combining this with organic cross-linking with tea polyphenols to achieve shell solidification, the microcapsules can maintain a relatively long stable migration time under formation conditions and gradually rupture under temperature and environmental influences, releasing high concentrations of surfactant in a directed manner. The resulting microcapsules possess excellent dispersibility, stability, and controllable release performance, effectively reducing oil-water interfacial tension and improving oil recovery.

[0007] A method for preparing a green microcapsule oil displacement agent based on gelatin / sodium alginate, wherein the wall material of the microcapsule oil displacement agent is composed of gelatin and sodium alginate, and the core material is a hydrophilic surfactant. The preparation method includes the following steps: (1) At 40-50℃, gelatin and sodium alginate are dissolved in ultrapure water and stirred until dissolved. The pH of the system is adjusted to 3.5-4.7. A hydrophilic surfactant solution is added to the system while stirring, and the reaction is carried out for 0.5-1.5h. (2) Add tea polyphenol solution to the reaction product of step (1) under stirring, react at 40-50℃ for 0.5-1.5h, then adjust the pH of the system to 3.9-10, let it stand and solidify at 20-30℃ for 2-12h, centrifuge to obtain the solidified liquid reaction product. (3) Drying.

[0008] Preferably, the preparation method includes the following steps: (1) At 45°C, gelatin and sodium alginate were dissolved in ultrapure water and stirred until dissolved. The pH of the system was adjusted to 3.5-4.7. A hydrophilic surfactant solution was added to the system while stirring, and the reaction was carried out for 1 hour. (2) Add tea polyphenol solution to the reaction product of step (1) under stirring, react at 45°C for 1 h, then adjust the pH of the system to 3.9-10, let it stand and solidify at 25°C for 4 h, centrifuge to obtain the solidified liquid reaction product. (3) Drying.

[0009] More preferably, in step (1) the pH of the system is adjusted to 3.9, and in step (2) the pH of the system is adjusted to 7.0.

[0010] Preferably, the hydrophilic surfactant is a mixture of sodium dodecylbenzenesulfonate and sodium dodecyl polypropoxysulfate.

[0011] Preferably, the total mass ratio of the gelatin and sodium alginate to the hydrophilic surfactant is (1-4):1; in step (1), the final concentration of the hydrophilic surfactant after adding the hydrophilic surfactant solution is 0.5-2wt%; and the mass of the tea polyphenols is 2.5%-20% of the mass of the gelatin.

[0012] Preferably, the mass ratio of gelatin to sodium alginate is 5:5-9:1; and the mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl polypropoxysulfate is (0.5-2):1.

[0013] More preferably, the total mass ratio of the gelatin and sodium alginate to the hydrophilic surfactant is 2:1; in step (1), the final concentration of the hydrophilic surfactant after adding the hydrophilic surfactant solution is 1 wt%.

[0014] More preferably, the mass ratio of gelatin to sodium alginate is 6:4; and the mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl polypropoxysulfate is 1:1.

[0015] Preferably, the drying is freeze drying.

[0016] More preferably, the freeze-drying conditions are: freezing temperature -15 to -25°C, cold trap temperature -40 to -50°C, and vacuum pressure 10 to 100 Pa.

[0017] Preferably, the gelatin is type B gelatin with a molecular weight of 50-100 kDa; and the sodium alginate has a viscosity of 500-1000 mPa·s.

[0018] A green microcapsule oil displacement agent based on gelatin / sodium alginate is prepared by the above-described preparation method.

[0019] The application of the gelatin / sodium alginate-based green microcapsule oil displacement agent in oil displacement.

[0020] The green microcapsule oil displacement agent of the present invention exhibits the following controllable release behavior during the oil displacement process: Stable migration: In the initial stage of injection, the microcapsule shell remains intact, and the particles are uniformly dispersed in the formation pores, avoiding premature loss of surfactants. Response rupture: When the microcapsules reach the deep oil layer, under the action of a certain temperature for a long time, the shell gradually ruptures, releasing the internal surfactant solution; Oil displacement and enhancement: The released surfactants can significantly reduce the interfacial tension between oil and water, improve wettability, and increase the utilization rate of residual oil; at the same time, the ruptured shell natural polymers can enhance the viscosity of the aqueous phase and block high-permeability channels, thereby achieving profile control and water shut-off effects.

[0021] The organic crosslinking agent described in this invention is tea polyphenol, which can interact with the amino and hydroxyl groups on gelatin molecules to enhance the stability of microcapsules.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) Green and environmentally friendly: This invention uses natural biodegradable materials such as gelatin and sodium alginate as wall materials, which avoids the environmental pollution problems that may be caused by traditional petrochemical-based synthetic polymer microcapsules in the preparation and application process, and has good environmental friendliness and sustainability; (2) High efficiency of surfactant loading: High encapsulation rate, which realizes efficient encapsulation and stable fixation of surfactant, and significantly improves the content of effective ingredients per unit volume of microcapsules; (3) Controllable release and high efficiency of oil displacement: The microcapsules prepared by this invention have good structural stability in the formation environment, can remain intact and migrate in the reservoir channel, and can break down rapidly under specific conditions to release high concentrations of surfactants, effectively reduce the oil-water interfacial tension and improve the oil displacement efficiency. (4) Adaptable to complex reservoir conditions: The microcapsules prepared have excellent dispersibility and flowability, and can enter the deep reservoir with the injected water, avoiding the defects of traditional microcapsules that are prone to premature rupture and rapid decline in oil displacement effect during injection and seepage. (5) The method of the present invention has a simple production process, mild reaction conditions, low energy consumption and low preparation cost, which is conducive to industrial production and practical application. Attached Figure Description

[0023] Figure 1 This is a graph showing the relationship between the encapsulation efficiency of the microcapsule oil displacement agents S1-S4 obtained in Examples 1-4 and the reaction pH. Figure 2 It is an optical microscope for the liquid reaction products after solidification at different pH values; Figure 3 These are optical microscope images of the liquid reaction products after curing at different curing times; Figure 4 These are optical microscope images of the liquid reaction products after solidification when different amounts of tea polyphenols are added. Figure 5 This is a graph showing the relationship between the release rate of the microcapsule oil displacement agent S2 obtained in Example 2 and the release temperature. Figure 6 This is a graph showing the relationship between the interfacial tension value of the microcapsule oil displacement agent S2 obtained in Example 2 and the simulated crude oil as a function of dilution ratio. Figure 7 These are microscope images of water-driven oil recovery using a micro-glass etching model; Figure 8 This is a microscope image of the oil displacement agent S2 obtained in Example 2 under the micro-glass etching model; Figure 9 This is a magnified microscopic photograph of the oil displacement agent S2 obtained in Example 2 under the microglass etching model. Detailed Implementation

[0024] Example 1 A method for preparing a green microcapsule oil displacement agent based on gelatin / sodium alginate, wherein the wall material of the microcapsule oil displacement agent is composed of gelatin and sodium alginate, and the core material is a hydrophilic surfactant. The preparation method includes the following steps: (1) At 45°C, 2.4 g of gelatin (GEL) and 1.6 g of sodium alginate (SA) were dissolved in 176 mL of ultrapure water and stirred until dissolved to obtain a GEL / SA solution; 1.0 g each of sodium dodecylbenzenesulfonate (SDBS) and sodium dodecyl polypropoxysulfate (APS) were dissolved together in 18 mL of ultrapure water to obtain a hydrophilic surfactant mixed solution; 10 wt% glacial acetic acid solution was slowly added dropwise to the GEL / SA solution to adjust the pH of the system to 3.5 in order to enhance the charge effect of gelatin and promote its complexation with surfactant; then the hydrophilic surfactant solution was added to it under stirring and reacted for 1 h to obtain an uncured microcapsule oil displacement agent; (2) Under stirring, add tea polyphenol solution (the mass of tea polyphenol is 10% of gelatin) to the reaction product of step (1), react at 45°C for 1 hour, then adjust the pH of the system to 7.0 with sodium hydroxide solution, let it stand and solidify at 25°C for 4 hours, centrifuge to obtain the solidified liquid reaction product. (3) The microcapsule oil displacement agent, abbreviated as S1, was obtained by freeze drying under the conditions of freezing temperature of −15℃, cold trap temperature of −50℃ and vacuum pressure of 100Pa. The gelatin is type B gelatin with a molecular weight of 50-100 kDa; the sodium alginate is of high viscosity-average molecular weight grade with a viscosity of 500-1000 mPa·s.

[0025] Example 2 In step (1), the pH was adjusted to 3.9, and the rest was the same as in Example 1, to obtain the microcapsule oil displacement agent, abbreviated as S2.

[0026] Example 3 In step (1), the pH was adjusted to 4.3, and the rest was the same as in Example 1, to obtain the microcapsule oil displacement agent, abbreviated as S3.

[0027] Example 4 In step (1), the pH was adjusted to 4.7, and the rest was the same as in Example 1, to obtain the microcapsule oil displacement agent, abbreviated as S4.

[0028] Example 5 In step (2), the pH was adjusted to 3.9 using glacial acetic acid solution. The rest was the same as in Example 2, and the microcapsule oil displacement agent was obtained, referred to as S5.

[0029] Example 6 In step (2), the pH was adjusted to 10.0 using sodium hydroxide solution. The rest was the same as in Example 2, and the microcapsule oil displacement agent was obtained, abbreviated as S6.

[0030] Example 7 In step (2), the mixture is left to stand and solidify for 2 hours. The rest is the same as in Example 2, and the microcapsule oil displacement agent is abbreviated as S7.

[0031] Example 8 In step (2), the mixture is left to stand and solidify for 3 hours. The rest of the steps are the same as in Example 2, and the microcapsule oil displacement agent is abbreviated as S8.

[0032] Example 9 In step (2), the mixture is left to stand and solidify for 12 hours. The rest of the process is the same as in Example 2, and the microcapsule oil displacement agent is abbreviated as S9.

[0033] Example 10 The mass of tea polyphenols was 5% of that of gelatin, and the rest was the same as in Example 2, resulting in a microcapsule oil-displacing agent abbreviated as S10.

[0034] Example 11 The mass of tea polyphenols was 3.3% of that of gelatin, and the rest was the same as in Example 2, resulting in a microcapsule oil-displacing agent abbreviated as S11.

[0035] Example 12 The mass of tea polyphenols was 2.5% of that of gelatin, and the rest was the same as in Example 2, resulting in a microcapsule oil-displacing agent abbreviated as S12.

[0036] Example 13 A method for preparing a green microcapsule oil displacement agent based on gelatin / sodium alginate, wherein the wall material of the microcapsule oil displacement agent is composed of gelatin and sodium alginate, and the core material is a hydrophilic surfactant. The preparation method includes the following steps: (1) At 40°C, 2.0 g of gelatin (GEL) and 2.0 g of sodium alginate (SA) were dissolved in 176 mL of ultrapure water and stirred until dissolved to obtain a GEL / SA solution; 1.4 g of sodium dodecylbenzenesulfonate (SDBS) and 2.6 g of sodium dodecyl polypropoxysulfate (APS) were dissolved together in 16 mL of ultrapure water to obtain a hydrophilic surfactant mixed solution; 10 wt% glacial acetic acid solution was slowly added dropwise to the GEL / SA solution to adjust the pH of the system to 3.9 in order to enhance the charge effect of gelatin and promote its complexation with surfactant; then the hydrophilic surfactant solution was added to it under stirring and reacted for 1.5 h to obtain an uncured microcapsule oil displacement agent; (2) Under stirring, add tea polyphenol solution (the mass of tea polyphenol is 10% of gelatin) to the reaction product of step (1), react at 40°C for 1.5h, then adjust the pH of the system to 7.0 with sodium hydroxide solution, let it stand and solidify at 20°C for 4h, centrifuge to obtain the solidified liquid reaction product. (3) The microcapsule oil displacement agent, abbreviated as S13, was obtained by freeze drying under the conditions of freezing temperature of −15℃, cold trap temperature of −50℃ and vacuum pressure of 100 Pa. The gelatin is type B gelatin with a molecular weight of 50-100 kDa; the sodium alginate is of high viscosity-average molecular weight grade with a viscosity of 500-1000 mPa·s.

[0037] Example 14 A method for preparing a green microcapsule oil displacement agent based on gelatin / sodium alginate, wherein the wall material of the microcapsule oil displacement agent is composed of gelatin and sodium alginate, and the core material is a hydrophilic surfactant. The preparation method includes the following steps: (1) At 50°C, 3.6 g of gelatin (GEL) and 0.4 g of sodium alginate (SA) were dissolved in 176 mL of ultrapure water and stirred until dissolved to obtain a GEL / SA solution; 0.66 g of sodium dodecylbenzenesulfonate (SDBS) and 0.34 g of sodium dodecyl polypropoxysulfate (APS) were dissolved together in 19 mL of ultrapure water to obtain a hydrophilic surfactant mixed solution; 10 wt% glacial acetic acid solution was slowly added dropwise to the GEL / SA solution to adjust the pH of the system to 3.9 in order to enhance the charge effect of gelatin and promote its complexation with surfactants; then the hydrophilic surfactant solution was added to it under stirring and reacted for 0.5 h to obtain an uncured microcapsule oil displacement agent; (2) Under stirring, add tea polyphenol solution (the mass of tea polyphenol is 20% of gelatin) to the reaction product of step (1), react at 50°C for 0.5h, then adjust the pH of the system to 7.0 with sodium hydroxide solution, let it stand and solidify at 30°C for 4h, centrifuge to obtain the solidified liquid reaction product. (3) The microcapsule oil displacement agent, abbreviated as S14, was obtained by freeze drying at a freezing temperature of -25℃, a cold trap temperature of -40℃ and a vacuum pressure of 10 Pa. The gelatin is type B gelatin with a molecular weight of 50-100 kDa; the sodium alginate is of high viscosity-average molecular weight grade with a viscosity of 500-1000 mPa·s.

[0038] I. Encapsulation efficiency testing Take a sample of the uncured microcapsule oil displacement agent obtained in step (1), centrifuge it, take the supernatant, and measure its absorbance value at a wavelength of 265 nm using a UV-Vis absorption spectrometer. A 1). Using a mixed solution of SDBS / APS of the same concentration as a standard, its absorbance at 265 nm was measured. A 0). Calculate the encapsulation efficiency of the microcapsules using the following formula: ; Calculations showed that the encapsulation efficiencies of microcapsules S1-S4 in Examples 1-4 were 50.4%, 85.3%, 44.3%, and 28.3%, respectively. (See attached figures.) Figure 1 .

[0039] II. Morphological Inspection 1. Optical microscopic morphology of the solidified liquid reaction products in step (2) of Examples 2, 5, and 6 is as follows: Figure 2 .Depend on Figure 2 It can be seen that microcapsules are generated in all cases. Microcapsules S2 have a uniform spherical structure and high size consistency. In Example 5, when the pH in step (2) is adjusted to 3.9, the number of spherical microcapsules is greatly reduced, and there is collapse and the microcapsules stick together. In Example 6, when the pH in step (2) is adjusted to 10.0, some microcapsules swell, the size consistency is not high, and the number of microcapsules is relatively small. High pH solidification may lead to microcapsule degradation. 2. Optical microscopic morphology analysis of the solidified liquid reaction products in step (2) of Examples 2, 7, 8, and 9 is as follows: Figure 3 .Depend on Figure 3 The results show that microcapsules were formed in all samples, but the microcapsules of S7 and S8 were not uniform in size and were not fully solidified; while the number of microcapsules in S10 was reduced, and prolonged solidification would lead to microcapsule degradation. Microcapsules S2 had a uniform spherical structure and high size consistency, and a large number of microcapsules. 3. Observe the products of step (2) in Examples 2 and 10-12. See the optical photographs below. Figure 4 It can be seen that when the mass of tea polyphenols in Example 2 is 10% of gelatin, the product is uniformly distributed and there is no sedimentation, indicating that the curing is complete; while when the mass of tea polyphenols in Examples 10-12 is 5%, 3.3%, and 2.5% of gelatin, respectively, the liquid product shows obvious sedimentation and adhesion to the wall, indicating that the microcapsule solution is not completely cured.

[0040] IV. Simulated Release Experiment The microcapsules prepared in Example 2 were used to conduct a simulated release experiment. Specifically, the solidified liquid product from step (2) was heated in a water bath at different temperatures (30, 40, 50, and 60°C) for different durations. Samples were taken, and the supernatant was collected by centrifugation. The absorbance intensity of the supernatant was recorded by scanning at 265 nm using a UV-Vis absorption spectrometer. A 3), by comparing the initial absorbance of the SDBS / APS mixed solution in the supernatant of the microcapsule oil displacement agent before release (i.e., the supernatant obtained by centrifugation in step (2)). A 2) In comparison, the release rate of the microcapsules was calculated according to the following cumulative release rate formula: , in, A The determination of 0 was as follows: using a mixed solution of SDBS / APS of the same concentration as a standard, the absorbance at 265 nm was measured. A 0; The results of the cumulative release rate are shown in Figure 5 The results showed that the release rate of the green microcapsule oil displacement agent of the present invention gradually increased with the increase of temperature and time: at 30℃, the release rate could reach 20% after 100 h; at 60℃, the release rate could reach 90% after 100 h.

[0041] V. Interface Tension Test The interfacial tension reduction capability of the microcapsule oil displacement agent S2 prepared in Example 2 was tested. Specifically, crude oil was diluted with kerosene at a mass ratio of 5:4, resulting in simulated crude oil with a viscosity of approximately 16 mPa·s. The microcapsule oil displacement agent S2 was diluted to different concentrations according to volume fractions and placed at 60°C for 100 h to allow the core material surfactant to be fully released. The interfacial tension between the oil displacement agent and the simulated crude oil was measured using a rotating drop interfacial tensiometer at 40°C. (See [link to relevant documentation]). Figure 6 Wherein S / A is the hydrophilic surfactant mixture solution. Results show that after complete release, the interfacial tension between the green microcapsule oil displacement agent of this invention and the model oil is within 10. −3 ~10 −2 It has a capacity in the mN / m range and a significant oil-washing ability.

[0042] VI. Simulated Oil Displacement Experiment The microcapsule oil displacement agent S2 prepared in Example 2 was used to conduct simulated oil displacement experiments on a micro-glass etching model. S2 was diluted to 60 vol% of the original solution by volume, as the apparent viscosity at this point was closest to 16 mPa·s, which is close to the viscosity of the prepared simulated crude oil, and the two have good comparability in terms of flow resistance. Specifically, a microchannel model prepared by etching glass was used to simulate the capillary structure of the oil reservoir. After connecting the inlet and outlet pipes of the glass etching model, it was fixed on a 40°C hot stage to simulate the reservoir conditions. First, a high injection rate (2 µL·min) was used... -1 Pump oil phase into the model to ensure the channels are saturated with oil. After saturation, pump at a rate of 2 µL / min. -1 Aqueous phase is injected into the channel at a rate of ( Figure 7 ) or microcapsule oil displacement agent system ( Figure 8 , Figure 9 Displacement was carried out, and the displacement process was recorded using a high-resolution optical microscope; The results showed that after 96 hours, the microcapsule-assisted oil displacement method had less residual oil compared to water-assisted oil displacement, and oil droplets generated by the interaction between the microcapsules and the oil could be clearly observed.

Claims

1. A method for preparing a green microcapsule oil-displacing agent based on gelatin / sodium alginate, characterized in that: The wall material of the microcapsule oil displacement agent is composed of gelatin and sodium alginate, and the core material is a hydrophilic surfactant. The preparation method includes the following steps: (1) At 40-50℃, gelatin and sodium alginate are dissolved in ultrapure water and stirred until dissolved. The pH of the system is adjusted to 3.5-4.

7. A hydrophilic surfactant solution is added to the system while stirring, and the reaction is carried out for 0.5-1.5h. (2) Add tea polyphenol solution to the reaction product of step (1) under stirring, react at 40-50℃ for 0.5-1.5h, then adjust the pH of the system to 3.9-10, let it stand and solidify at 20-30℃ for 2-12h, centrifuge to obtain the solidified liquid reaction product. (3) Drying.

2. The preparation method of the green microcapsule oil-displacing agent based on gelatin / sodium alginate according to claim 1, characterized in that: The hydrophilic surfactant is a mixture of sodium dodecylbenzenesulfonate and sodium dodecyl polypropoxysulfate.

3. The preparation method of the green microcapsule oil-displacing agent based on gelatin / sodium alginate according to claim 2, characterized in that: The total mass ratio of the gelatin and sodium alginate to the hydrophilic surfactant is (1-4):1; in step (1), the final concentration of the hydrophilic surfactant after adding the hydrophilic surfactant solution is 0.5-2wt%; the mass of the tea polyphenols is 2.5%-20% of the mass of the gelatin.

4. The preparation method of the green microcapsule oil-displacing agent based on gelatin / sodium alginate according to claim 3, characterized in that: The mass ratio of gelatin to sodium alginate is 5:5-9:1; the mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl polypropoxysulfate is (0.5-2):

1.

5. The preparation method of the green microcapsule oil-displacing agent based on gelatin / sodium alginate according to claim 4, characterized in that: The total mass ratio of the gelatin and sodium alginate to the hydrophilic surfactant is 2:1; in step (1), the final concentration of the hydrophilic surfactant after adding the hydrophilic surfactant solution is 1 wt%.

6. The preparation method of the green microcapsule oil displacement agent based on gelatin / sodium alginate according to claim 5, characterized in that: The mass ratio of gelatin to sodium alginate is 6:4; the mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl polypropoxysulfate is 1:

1.

7. The preparation method of the green microcapsule oil-displacing agent based on gelatin / sodium alginate according to claim 1, characterized in that: The drying process is freeze-drying.

8. The method for preparing the green microcapsule oil-displacing agent based on gelatin / sodium alginate according to claim 1, characterized in that: The gelatin is type B gelatin with a molecular weight of 50-100 kDa; the sodium alginate has a viscosity of 500-1000 mPa·s.

9. A green microcapsule oil displacement agent based on gelatin / sodium alginate, characterized in that: It is prepared by the preparation method described in any one of claims 1-8.

10. The application of the gelatin / sodium alginate-based green microcapsule oil displacement agent according to claim 9 in oil displacement.

Images