In-layer CO2 authigenic system composition for oil reservoir, CO2 authigenic system and application of CO2 authigenic system

Abstract

The invention belongs to the technical field of oil extraction, and relates to an in-layer CO2 authigenic system composition for an oil reservoir, a CO2 authigenic system and application of the CO2 authigenic system composition and the CO2 authigenic system. The in-layer CO2 self-generation system composition for the oil reservoir is composed of a composition A and a composition B, the composition A comprises a blowing agent and a foaming agent, the composition B comprises an initiator, the blowing agent is a salt compound which reacts with the initiator to generate CO2, the composition A or the composition B further comprises a foam stabilizer, and the foam stabilizer is composed of a foaming agent and a foaming agent. The foam stabilizer is a biological polysaccharide polymer. By using the biological polysaccharide polymer as the foam stabilizer and utilizing the characteristics of good tackifying performance and foam stabilizing performance, high temperature resistance and high salinity resistance of the biological polysaccharide polymer, the foaming volume and the drainage half-life period of the autogenous CO2 system under the conditions of high temperature and high salinity can be improved, and the foam viscosity can be maintained for a relatively long time; the foam stability of an autogenous CO2 system under the high-temperature and high-salinity stratum condition is improved, and the oil displacement efficiency is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil production, and in particular to an intra-layer self-generated CO2 system composition for oil reservoirs, a self-generated CO2 system and applications thereof. Background Art

[0002] During the waterflooding process of oil reservoir development, due to the strong heterogeneity between and within reservoir layers and the large difference in viscosity between the injected water and crude oil, the sweep coefficient and oil recovery efficiency of most oil reservoirs after one water flooding are low. Realizing the efficient development of oil reservoirs after water flooding has always been a technical problem that has not been fully solved, and there is huge potential for improving recovery rate.

[0003] In-reservoir CO2 generation relies on the self-decomposition of chemical agents at formation temperatures (single-liquid method) or the thermochemical reaction of multiple agents (two-liquid method). This generates large amounts of CO2 gas, which reacts with surfactants to form foam. The contact of CO2 with the crude oil at the displacement front causes oil expansion and viscosity reduction, lowering the oil-water interfacial tension. Combined with a high-stability system such as a foaming agent and stabilizer, this system can simultaneously achieve profile control and oil displacement, improving oil recovery efficiency. In-reservoir self-generated, highly stable CO2 foam systems combine the advantages of polymers, foams, and surfactants, offering significant advantages over single foam systems and polymers, achieving a synergistic effect. The single-liquid method is limited in its application due to its narrow temperature range and low gas generation efficiency. The two-liquid method involves a gas-generating agent (GF, such as NaCO3, NaHCO3, or NH4HCO3) and a gas-releasing agent (GY, such as HCl or CH3COOH). These two agents are injected into the reservoir in stages. Upon contact with the formation, the two agents react exothermically to generate CO2 in situ, thereby enhancing oil recovery.

[0004] However, the existing intra-layer self-generated CO2 system has poor foam stabilization effect under the acidic and alkaline conditions formed by the intra-layer self-generated foam base fluid. The system performance is general and requires the addition of foam stabilizers to improve foam stability. However, the foam stabilization effect is relatively poor under high temperature and high mineralization formation conditions, resulting in poor application effect and no obvious effect on improving oil recovery rate. Summary of the Invention

[0005] The present invention provides an intra-layer self-generated CO2 system composition for oil reservoirs, which solves the problem of poor foam stability of the prior art self-generated CO2 system in high-temperature and high-mineralization formations.

[0006] The second purpose of the present invention is to provide an intra-layer self-generated CO2 system for oil reservoirs, so as to solve the problem of poor foam stability of the prior art self-generated CO2 system in high-temperature and high-mineralization formations.

[0007] The third purpose of the present invention is to provide an application of an autogenous CO2 system in an oil reservoir layer to solve the problem of poor foam stability of the autogenous CO2 system in high-temperature and high-mineralization formations in the prior art.

[0008] In order to solve the above technical problems, the technical solution of the self-generated CO2 system composition for oil reservoirs of the present invention is as follows: A composition for an autogenous CO2 system in an oil reservoir layer, comprising a composition A and a composition B. Composition A comprises an aeration agent and a foaming agent, and composition B comprises an initiator. The aeration agent is a salt compound that reacts with the initiator to generate CO2. Composition A or composition B also comprises a foam stabilizer, which is a biopolysaccharide polymer.

[0009] The present invention improves the existing technology and provides a self-generated CO2 system composition for oil reservoirs. The gas generating agent in composition A and the initiator in composition B undergo a thermochemical reaction to generate CO2 and react with a foaming agent to form foam. By using a biopolysaccharide polymer as a foam stabilizer and utilizing the characteristics of the biopolysaccharide polymer such as good viscosity increasing and foam stabilizing properties and high temperature resistance and high mineralization, the foaming volume and liquid separation half-life of the self-generated CO2 system under high temperature and high mineralization conditions can be increased, and the foam viscosity can be maintained for a long time, thereby improving the foam stability of the self-generated CO2 system under high temperature and high mineralization formation conditions and further improving the oil recovery efficiency.

[0010] In order to further improve the CO2 foam generation efficiency, preferably, the mass ratio of the foam stabilizer, the gas generating agent, the foaming agent and the initiator is (0.3~0.5):(10~12):(0.8~1.0):(10~12).

[0011] In order to further improve the foam stability under high temperature and high mineralization conditions, preferably, the foam stabilizer is selected from one or both of wenglun gum and xanthan gum.

[0012] In order to further improve the gas release efficiency, preferably, the initiator is selected from one or more of oxalic acid, hydrochloric acid, acetic acid and hypochlorous acid.

[0013] In order to further increase the CO2 generation rate, preferably, the gasifying agent is a carbonate or an ammonium salt that hydrolyzes in water to form a carbonate. When the ammonium salt is ammonium carbamate, it hydrolyzes in water to form ammonium carbonate.

[0014] In order to further improve the foaming performance, preferably, the foaming agent is selected from one or more of cocamidopropyl betaine, lauramidopropyl betaine, sodium fatty alcohol ether sulfate, and sodium lauryl sulfate.

[0015] The technical solution of the in-layer self-generated CO2 system for oil reservoirs of the present invention is as follows: A self-generated CO2 system for oil reservoirs is provided. The self-generated CO2 system composition for oil reservoirs and water are respectively prepared into an aqueous solution of composition A and an aqueous solution of composition B.

[0016] The present invention provides an intra-layer self-generated CO2 system for oil reservoirs. By adopting the self-generated CO2 system composition, the aqueous solution of composition A and the aqueous solution of composition B undergo a thermochemical reaction to generate CO2 gas, which reacts with a foaming agent to form foam. The biopolysaccharide polymer is used to increase the foaming volume and liquid separation half-life of the self-generated CO2 system under high temperature and high salinity conditions, and can maintain the foam viscosity for a long time, thereby improving the foam stability of the self-generated CO2 system under high temperature and high salinity formation conditions, achieving crude oil expansion and viscosity reduction, reducing oil-water interfacial tension, and further improving oil recovery efficiency.

[0017] In order to further improve the CO2 foam generation efficiency and increase the oil recovery rate, preferably, the mass fractions of the foam stabilizer, gas generating agent, foaming agent and initiator in the system are 0.3%~0.5%, 10%~12%, 0.8%~1.0% and 10%~12% respectively.

[0018] The technical solution for the application of the self-generated CO2 system in the oil reservoir of the present invention is as follows: The invention discloses an application of an intra-layer self-generated CO2 system for oil reservoirs, wherein an aqueous solution of composition A and an aqueous solution of composition B are injected into the reservoir in sections.

[0019] The present invention provides an application of a self-generated CO2 system in an oil reservoir layer. By using the self-generated CO2 system, an aqueous solution of composition A and an aqueous solution of composition B are injected into the reservoir in sections. The aqueous solution of composition A and the aqueous solution of composition B come into contact with each other, a thermochemical reaction occurs to generate a large amount of carbon dioxide gas, and the foam reacts with a foaming agent to form foam. Under the action of a biopolysaccharide polymer foam stabilizer, the foaming volume and the liquid separation half-life are increased, and the foam viscosity can be maintained for a long time. Good foam stability can be maintained under high temperature and high salinity conditions, thereby achieving crude oil expansion and viscosity reduction, reducing oil-water interfacial tension, and further improving oil recovery efficiency.

[0020] In order to further achieve foam stability under different reservoir conditions, preferably, the temperature of the reservoir is 80-120°C, the salinity of the reservoir is (1-2.5)×10 5 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing the foam morphology formed by the intra-stratum self-generated CO2 system composition of Example 1 in simulated formation water with a salinity of 150,000 mg / L; Figure 2 This is a diagram showing the oil displacement effect of continuous water flooding with simulated formation water under high salinity formation conditions; Figure 3 This is a diagram showing the oil displacement effect of the self-generated CO2 system in the layer of Comparative Example 1 under high salinity formation conditions; Figure 4 This is a diagram showing the oil displacement effect of the intra-layer self-generated CO2 system of Example 1 under high-salinity formation conditions. DETAILED DESCRIPTION

[0022] The technical concept of the self-generated CO2 system composition for oil reservoirs provided by the present invention is as follows: A composition for an autogenous CO2 system in an oil reservoir layer, comprising a composition A and a composition B. Composition A comprises an aeration agent and a foaming agent, and composition B comprises an initiator. The aeration agent is a salt compound that reacts with the initiator to generate CO2. Composition A or composition B also comprises a foam stabilizer, which is a biopolysaccharide polymer.

[0023] The present invention provides a self-generated CO2 system composition for oil reservoirs. By using a biopolysaccharide polymer as a foam stabilizer, the gas generating agent in composition A and the initiator in composition B undergo a thermochemical reaction to generate CO2, which reacts with the foaming agent to form foam. By utilizing the good viscosity-increasing and foam-stabilizing properties, and the high-temperature and high-mineralization resistance of the biopolysaccharide polymer, the foaming volume and liquid separation half-life of the self-generated CO2 system under high-temperature and high-mineralization conditions can be increased, and the foam viscosity can be maintained for a long time, thereby improving the foam stability of the self-generated CO2 system under high-temperature and high-mineralization formation conditions and further improving the oil recovery efficiency.

[0024] Compared to conventional CO2 flooding, the self-generating CO2 foam system, due to its unique gas production mechanism, has a superior deblocking effect on formation pores. When injected into the formation, the system undergoes an exothermic reaction deep within the reservoir, rapidly increasing the local temperature. The organic colloids and asphaltenes in the crude oil decrease in viscosity upon heating, thereby increasing the oil's fluidity and achieving a thermal deblocking effect. Furthermore, CO2, when dissolved in water, is weakly acidic, which can partially remove inorganic scale blockages and restore a certain level of well productivity.

[0025] The self-generated CO2 system in the layer with poor foam stabilization performance is prone to serious gas channeling and gravity overburden phenomena in oil displacement. The self-generated CO2 foam system in the layer provided by the present invention can achieve "blocking large areas but not small areas" and "controlling water but not oil" during displacement. The foam can selectively block high permeability (or high water channeling) layers, allowing the displacement fluid to enter unaffected areas (such as low permeability and high oil saturation areas). The surfactant used to make the foam can be adsorbed on the interface (such as gas-water, oil-water, and solid-water), thereby reducing the oil-water interfacial tension, while changing the wettability, improving the foam stability and oil displacement efficiency.

[0026] After the autogenous CO2 system produces a large amount of CO2 under formation conditions, it will quickly dissolve in crude oil under high temperature and high pressure. On the one hand, it can reduce the viscosity of crude oil and increase its flow properties; on the other hand, it can cause the crude oil to expand, making it easier for the remaining oil to break away from the constraints of formation water and rock surface, thereby improving oil recovery efficiency.

[0027] When CO2 dissolves in crude oil and water, it can reduce the interfacial tension between oil and water molecules and change the relative permeability of oil and water; it can also improve the oil-water mobility ratio and prevent viscous fingering. Under the combined action of the two mechanisms, the affected area of water drive is increased, the oil displacement efficiency is improved, and thus the recovery rate is increased.

[0028] It is understood that the foam stabilizer can be in composition A, in which case composition A consists of an aerator, a foam stabilizer, and a foaming agent, while composition B is the initiator. Alternatively, the foam stabilizer can be in composition B, in which case composition A consists of an aerator and a foaming agent, while composition B consists of an initiator and a foam stabilizer. The preferred formulation is one in which the foam stabilizer is in composition A.

[0029] A self-generated CO2 system for oil reservoirs is provided. The self-generated CO2 system composition for oil reservoirs and water are respectively prepared into an aqueous solution of composition A and an aqueous solution of composition B.

[0030] In a specific embodiment, when preparing the self-generated CO2 system, a foam stabilizer is slowly added to water at a stirring speed of 200 r / min-500 r / min and then allowed to stand for 2 to 4 hours to form a uniform solution. An aeration agent and a foaming agent are added to the uniform solution at room temperature and slowly stirred to form an aqueous solution of composition A; an initiator is slowly added to water and slowly stirred to form an aqueous solution of composition B.

[0031] The invention discloses an application of an intra-layer self-generated CO2 system for oil reservoirs, wherein an aqueous solution of composition A and an aqueous solution of composition B are injected into the reservoir in sections.

[0032] It is understandable that, during the injection of the segmented plug, the aqueous solution of composition A may be injected first, or the aqueous solution of composition B may be injected first; the aqueous solution of composition A and the aqueous solution of composition B may be injected alternately once, or may be injected alternately in batches multiple times.

[0033] The embodiments of the present invention are further described below with reference to specific examples. Unless otherwise specified, the chemical reagents involved in the following examples are all commercially available conventional products.

[0034] 1. Specific embodiments of the in-layer self-generated CO2 system composition for oil reservoirs of the present invention Example 1 The present embodiment provides an intra-layer autogenous CO2 system composition for oil reservoirs, which consists of composition A and composition B. Composition A consists of Weinlun rubber, ammonium carbamate and cocamidopropyl betaine, and composition B is hydrochloric acid. The mass ratio of Weinlun rubber, ammonium carbamate, cocamidopropyl betaine and hydrochloric acid is 0.3:10:0.8:10.

[0035] Example 2 The present embodiment provides an intra-layer self-generated CO2 system composition for oil reservoirs, which consists of composition A and composition B. Composition A consists of Weinlun rubber, ammonium carbamate and cocamidopropyl betaine, and composition B is hydrochloric acid. The mass ratio of Weinlun rubber, ammonium carbamate, cocamidopropyl betaine and hydrochloric acid is 0.5:10:0.8:10.

[0036] Example 3 The composition for the self-generated CO2 system for oil reservoirs provided in this embodiment is different from that in Example 1 in that the Wenlun gum in composition A is replaced with xanthan gum, and the rest is the same as in Example 1.

[0037] 2. Specific embodiments of the in-layer self-generated CO2 system for oil reservoirs of the present invention Example 4 The self-generated CO2 system for oil reservoirs provided in this embodiment is prepared using the self-generated CO2 system composition of Example 1 and water. At a stirring speed of 200 r / min, warm wheel glue is slowly added to the water and the mixture is allowed to stand for 2 hours to form a uniform solution. Ammonium carbamate and cocamidopropyl betaine are added to the uniform solution at room temperature and slowly stirred to form an aqueous solution of 50 g of composition A; commercially available hydrochloric acid is slowly added to the water and slowly stirred to form an aqueous solution of 50 g of composition B. The mass fractions of warm wheel glue, ammonium carbamate, cocamidopropyl betaine and hydrochloric acid in the self-generated CO2 system are 0.3%, 10%, 0.8% and 10%, respectively.

[0038] Example 5 The self-generated CO2 system for oil reservoirs provided in this embodiment is prepared using the self-generated CO2 system composition of Example 2 and water. At a stirring speed of 500 r / min, warm wheel glue is slowly added to the water and the mixture is allowed to stand for 4 hours to form a uniform solution. Ammonium carbamate and cocamidopropyl betaine are added to the uniform solution at room temperature and slowly stirred to form an aqueous solution of 50 g of composition A; hydrochloric acid is slowly added to water and slowly stirred to form an aqueous solution of 50 g of composition B. The mass fractions of warm wheel glue, ammonium carbamate, cocamidopropyl betaine and hydrochloric acid in the self-generated CO2 system are 0.5%, 10%, 0.8% and 10%, respectively.

[0039] Example 6 The self-generated CO2 system for oil reservoirs provided in this embodiment is different from that in Example 4 in that the self-generated CO2 system composition of Example 3 and water are used for preparation, and the rest is the same as that in Example 4.

[0040] 3. Specific Examples of Applications of the In-layer Self-generated CO2 System for Oil Reservoirs of the Present Invention Example 7 Based on the high temperature, high salinity, and highly heterogeneous formation conditions, a formation model and original oil saturation were established and aged for more than 24 hours. After water flooding to a high water content, the aqueous solution of composition A and the aqueous solution of composition B in the autogenous CO2 system in the reservoir described in Example 4 were injected into the reservoir in stages. The parameters of the formation model are shown in Table 1.

[0041] Table 1 Formation model parameters

[0042] 4. Comparative Examples Comparative Example 1 The composition for the self-generated CO2 system for oil reservoirs provided in this comparative example is different from that in Example 1 in that the composition does not include a foam stabilizer.

[0043] Comparative Example 2 The composition for the self-generated CO2 system for oil reservoirs provided in this comparative example is different from that in Example 1 in that the foam stabilizer in the composition is partially hydrolyzed polyacrylamide (HPAM), Tianrun 134 purchased from Henan Tianrun Chemical Co., Ltd.

[0044] 5. Experimental Examples Experimental Example 1 This experimental example uses the conventional foam Waring Blender evaluation method to test the foam performance of the self-generated CO2 system composition. The specific test method is as follows: simulated formation water with a salinity of 100,000 mg / L, 150,000 mg / L, 200,000 mg / L, and 250,000 mg / L are respectively prepared, and the self-generated CO2 system composition in Example 1 is used. A stirring speed of 200 r / min is adopted in the simulated formation water. A foam stabilizer is slowly added and allowed to stand for 2 hours to form a uniform solution. An air-generating agent and a foaming agent are added to the uniform solution at room temperature to prepare 50 g of a mixed solution A. An air-entraining agent is added to the uniform solution at room temperature to prepare 50 g of a mixed solution. Liquid B, wherein the contents of each component are: foam stabilizer 0.3%, initiator 10%, gasifier 10%, foaming agent: 0.8%. The prepared mixed solution A and mixed solution B are poured into a constant speed stirrer and stirred at a speed of 6000 r / min for 1 min, and then the generated foam is poured into a heated measuring cylinder, the foam liquid level is read, and the foaming volume is recorded; after reading, the system is placed in a high-temperature and high-pressure foam observation kettle and allowed to stand to ensure that the temperature of the foaming system is maintained at 120°C and the pressure is 30 MPa, and the liquid precipitation half-life of the foam system under different salinities is recorded; the foam performance test of the self-generated CO2 system composition of the comparative example refers to the above test method.

[0045] Foam morphology photos Figure 1 As shown, the left figure is a macroscopic photo of the composition after foaming, and the right figure is an optical microscope photo of the foam. The foaming volume, half-life and comprehensive index under different salinity conditions are shown in Table 2, wherein the comprehensive index = foaming volume * half-life * 0.75. It can be seen from Table 2 that the intra-layer self-generated high-stability CO2 foam system of the present invention has good resistance to salinity and can still maintain good foam performance under higher formation salinity; and compared with not adding a foam stabilizer (Comparative Example 1) and adding a non-polysaccharide polymer as a foam stabilizer (Comparative Example 2), the intra-layer self-generated CO2 foam system provided by the present invention has higher foaming volume, half-life and comprehensive index, indicating that the foam stabilizer in the CO2 foam system of the present invention can effectively improve the stability of the foam.

[0046] Table 2 Foaming volume, half-life and comprehensive index under different salinity conditions

[0047] The foam was subjected to a foaming test at a salinity of 150,000 mg / L and a temperature of 120°C, and its viscosity performance was measured at aging times of 5d, 10d, 15d, and 20d. The test results are shown in Table 3. As can be seen from Table 3, the intra-layer self-generated high-stability foam system of the present invention has good viscosity-increasing performance, can maintain a high foam viscosity for a long time at a higher formation salinity, and has good long-term stability; and compared with Comparative Examples 1 and 2, the foam formed by the intra-layer self-generated CO2 system composition provided by the present invention also exhibits good viscosity-increasing properties.

[0048] Table 3 Viscosity properties at different aging times

[0049] Experimental Example 2 This experimental example tests the oil recovery performance of the intra-layer self-generated CO2 system provided by the present invention in the model oil recovery established in Example 7. During the experiment, the produced fluid was collected, the inlet and outlet pressures were recorded, and the key parameters of the oil recovery such as instantaneous oil recovery efficiency, instantaneous water content, instantaneous oil production, along-the-line pressure, and total recovery rate were collected and analyzed. The oil recovery performance was compared with that of the self-generated CO2 system in which only simulated formation water was injected for continuous water recovery, and the control examples 1 and 2.

[0050] The oil displacement effects of different oil displacement methods are shown in the figure below. Figure 2-4 As shown, from Figure 2 As can be seen, a total of 4.4 PV of water was injected. In the early stages of water flooding, the water cut and oil recovery efficiency increased with the increase in injected volume. In the later stages of water flooding, the instantaneous oil recovery efficiency decreased, and the water cut fluctuated slightly, showing an overall increasing trend, indicating that the water flooding effect gradually weakened. At 3.6 PV, the water flooding effect reached its limit, with an oil recovery efficiency of 59%.

[0051] from Figure 3 As can be seen, a total of 8.6 PV of water flooding was injected. Initially, the instantaneous oil recovery efficiency reached 8%, with the water cut dropping below 40%. During the continuous water flooding phase, the water flooding effect gradually weakened. A CO2 foam system without a foam stabilizer was then injected, and water flooding continued after the foam injection. Initially, the instantaneous oil recovery efficiency significantly improved, and the foam slug had a certain effect on improving oil recovery. The final oil recovery efficiency was 88%, approximately 40% higher than the initial water flooding phase.

[0052] from Figure 4As can be seen, a total of 5 PV of water flooding was injected. Initially, the instantaneous oil displacement efficiency reached 10%, with the water cut dropping below 50%. At 1.1 PV, the water flooding efficiency reached its limit. The CO2 foam system provided by the present invention was then injected, and water flooding continued after the foam injection. The enhanced foam slugs of the CO2 foam system provided by the present invention significantly enhanced oil recovery, resulting in a final oil displacement efficiency of 92%, an increase of approximately 60% compared to the single water flooding stage. This system also significantly improved oil displacement compared to a self-generated foam system without a foam stabilizer layer.

[0053] This invention utilizes biopolysaccharide polymers as foam stabilizers based on traditional autogenous foams, addressing the current system's problems of poor foaming performance, short liquid separation half-life, poor stability, and low viscosity in high-temperature, high-salinity formations. Leveraging the excellent viscosity-increasing and foam-stabilizing properties of biopolysaccharides, as well as their resistance to high temperatures and high salinity, this invention further enhances the performance of in-layer autogenous CO2 foam systems, maintaining stable performance even in high-salinity formations (above 100,000 mg / L). This is of great significance for enhancing oil recovery in heterogeneous, high-salinity reservoirs.

[0054] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A self-generated CO2 system composition for oil reservoirs, characterized in that: The composition consists of composition A and composition B, wherein composition A includes an aerating agent and a foaming agent, and composition B includes an initiator, wherein the aerating agent is a salt compound that reacts with the initiator to generate CO2. Composition A or composition B also includes a foam stabilizer, which is a biopolysaccharide polymer.

2. The self-generated CO2 system composition for oil reservoirs according to claim 1, characterized in that: The mass ratio of the foam stabilizer, the sparging agent, the foaming agent and the initiator is (0.3-0.5): (10-12): (0.8-1.0): (10-12).

3. The self-generated CO2 system composition for oil reservoirs according to claim 1 or 2, characterized in that: The foam stabilizer is selected from one or both of gum Glucoside and xanthan gum.

4. The self-generated CO2 system composition for oil reservoirs according to claim 1 or 2, characterized in that: The initiator is selected from one or more of oxalic acid, hydrochloric acid, acetic acid and hypochlorous acid.

5. The self-generated CO2 system composition for oil reservoirs according to claim 1 or 2, characterized in that: The gasifying agent is a carbonate or an ammonium salt that is hydrolyzed in water to form a carbonate.

6. The self-generated CO2 system composition for oil reservoirs according to claim 1 or 2, characterized in that: The foaming agent is selected from one or more of cocamidopropyl betaine, lauryl amide propyl betaine, sodium fatty alcohol ether sulfate, and sodium lauryl sulfate.

7. An in-layer self-generated CO2 system for oil reservoirs, characterized in that: The self-generated CO2 system composition for oil reservoirs according to any one of claims 1 to 6 and water are respectively prepared into an aqueous solution of composition A and an aqueous solution of composition B.

8. The in-layer self-generated CO2 system for oil reservoirs according to claim 7, characterized in that: The mass fractions of the foam stabilizer, the gasifier, the foaming agent and the initiator in the system are 0.3%-0.5%, 10%-12%, 0.8%-1.0% and 10%-12% respectively.

9. Use of the in-layer self-generated CO2 system for oil reservoirs as claimed in claim 7 or 8, characterized in that: An aqueous solution of composition A and an aqueous solution of composition B were injected into the reservoir in sections.

10. The use of the in-layer self-generated CO2 system for oil reservoirs according to claim 9, characterized in that: The temperature of the reservoir is 80-120°C, and the salinity of the reservoir is (1-2.5)×10 5 mg / L.

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