Method for exploiting low-permeability and high-viscosity oil reservoir in oil field

Abstract

The invention discloses a method for extracting crude oil from a low-permeability and high-viscosity oil reservoir, which comprises the following steps of: when the viscosity of the crude oil is higher than a preset value, fracturing according to a preset volume fracturing type, injecting supercritical fluid according to a preset injection type after fracturing is finished, and synchronously heating and soaking; after the average oil layer pressure explained by well testing is reduced to a preset value, supercritical fluid is injected into an oil layer according to a preset injection type for huff and puff production, and when the viscosity of crude oil is lower than a preset value, a foaming agent is added into the injected supercritical fluid for soaking; and opening the well for production, shutting the well and repeating the process after the oil yield of the day is reduced to a preset value. The mixed-phase pressure can be obviously reduced, the injection capacity can be improved, energy is accumulated for huff and puff production, the huff and puff cycle exploitation time is prolonged, the huff and puff action range is expanded, the huff and puff recovery efficiency is improved, and effective development of the oil reservoir is achieved.

Description

Technical Field

[0001] The invention relates to a method for exploiting low-permeability and high-viscosity oil reservoirs in an oil field, and in particular to a method for exploiting crude oil by adopting fracturing and injecting supercritical fluid, and belongs to the field of petroleum exploitation. Background Art

[0002] my country has a large number of deep-layer low-physical-property high-viscosity oil reservoir resources. The burial depth of such high-viscosity oil reservoirs is usually 1,600 meters, which has exceeded the lower limit of the depth of conventional steam injection technology. In addition, the oil layer permeability of such high-viscosity oil reservoirs is only below 500mD. Since the burial depth is greater than 1,600 meters, the corresponding overlying formation pressure is relatively high, and the permeability of the reservoir is low, which makes injection extremely difficult. The injection pressure of conventional steam is difficult to make steam enter the oil layer to drive oil. In addition, this type of reservoir is also water-sensitive to a certain extent, and conventional water injection and steam injection will cause the permeability of the reservoir to further decrease.

[0003] In order to achieve the development of this type of high-viscosity reservoir, supercritical steam injection was used to drive oil in the past. The temperature and pressure of water were raised to above the critical point (Tc = 374.3 ° C, Pc = 22.1 MPa), and the properties of water changed greatly, with extremely high permeability, solubility and reactivity. This type of supercritical steam injection provides a new technology to solve the problem of effective development of this type of reservoir. However, during the conventional supercritical steam injection process, due to the influence of reservoir water sensitivity, clay minerals expand, so the injection pressure remains high, and it is difficult to effectively reduce the injection pressure through multiple rounds of gas injection.

[0004] In addition, due to the limitation of injection capacity, the injection volume of each round is limited, and the energy provided to the formation is also limited. During the huff-and-puff production process, the energy is rapidly depleted, resulting in a short effective production time, a small huff-and-puff range, and low production. It is predicted that the recovery rate will be less than 20% if a simple supercritical steam huff-and-puff method is used.

[0005] At the same time, there is a large amount of CO injection in my country 2 Fluid development of low permeability reservoirs, injected CO 2 It is usually difficult to achieve a supercritical miscible state, the miscibility with reservoir crude oil is limited, the degassing rate is fast during the production process, and the output and pressure decrease rapidly, thus affecting the development effect to a certain extent. Summary of the invention

[0006] In view of the technical defects and technical drawbacks existing in the prior art, in order to significantly increase the range of action of the throughput injection medium of such oil reservoirs, improve the energy replenishment effect of the injection medium, and improve the throughput recovery rate, an embodiment of the present invention provides a method for exploiting low-permeability and high-viscosity oil reservoirs in oil fields that overcomes the above problems or at least partially solves the above problems.

[0007] An embodiment of the present invention provides a method for producing crude oil from a low-permeability and high-viscosity oil reservoir, comprising:

[0008] When the crude oil viscosity is higher than a predetermined value, fracturing is performed according to a predetermined volume fracturing type. After fracturing is completed, supercritical fluid is injected according to a predetermined injection type, and synchronous heating is performed to soak the well.

[0009] When the average reservoir pressure interpreted by the well test drops to a predetermined value, supercritical fluid is injected into the reservoir for huff and puff production according to the predetermined injection type. When the crude oil viscosity is lower than the predetermined value, a foaming agent is added to the injected supercritical fluid to soak the well.

[0010] Start production, and when the daily oil production drops to a predetermined value, shut down the well and repeat the above process;

[0011] The volume fracturing type is determined according to the production stage and the permeability difference; the injection type of the supercritical fluid is determined according to the crude oil viscosity and asphaltene content.

[0012] The method of the embodiment of the present invention can significantly reduce the miscible pressure, improve the injection capacity, accumulate energy for throughput production, extend the cycle production time of throughput, expand the scope of throughput, improve the recovery rate of throughput, and realize the effective development of such oil reservoirs.

[0013] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structure described in the written description, claims, and drawings.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0016] Figure 1 A flow chart of a method for producing crude oil from a low-permeability and high-viscosity oil reservoir provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0018] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0019] First, the technical terms mentioned in each embodiment of the present invention are briefly described as follows:

[0020] Supercritical fluid: When the temperature and pressure injected into the reservoir exceed the critical pressure and temperature of a certain fluid, the fluid becomes a supercritical fluid.

[0021] Supercritical steam: The critical temperature of water is 374°C and the critical pressure is 22.1MPa. When the temperature and pressure are greater than the critical point of water, a high-temperature and high-pressure fluid is formed, which becomes supercritical steam.

[0022] Steam huff and puff: a type of thermal oil recovery technology, also known as cyclic steam injection method, refers to the periodic injection of steam into the formation to heat and reduce the viscosity of underground crude oil, improve the flowability of crude oil, and then produce it. It is usually divided into three stages: steam injection, well soaking and recovery.

[0023] PV: controlled reservoir volume of a single well.

[0024] In view of the problems existing in the prior art, an embodiment of the present invention provides a method for exploiting a low-permeability and high-viscosity oil reservoir in an oil field: Figure 1 As shown, the following steps are included:

[0025] Step 100, determine the volume fracturing type according to the production stage and the permeability difference. The specific corresponding relationship is shown in the following Table 1:

[0026] Table 1

[0027] Mining stage Permeability difference Fracturing Type Original oil reservoir >10 <![CDATA[CO 2 Energy storage volume fracturing]]> Original oil reservoir ≤10 <![CDATA[Capacity expansion + CO 2 Energy storage volume fracturing]]> Developed oil reservoirs >10 <![CDATA[Temporary plugging + CO 2 Energy storage volume fracturing]]> Developed oil reservoirs ≤10 <![CDATA[Capacity expansion + CO 2 Energy storage volume fracturing]]>

[0028] The expansion process may include: injecting a solvent plug containing 80-100°C warm water into the oil well until the oil layer pressure reaches 0.5 MPa above the formation fracture pressure; the mass ratio of the solvent to the warm water is 1:1-1:10; the solvent plug is one or more of alkanes, aromatics, naphtha, petroleum ether, diesel, dimethyl ether, and ethanol with a carbon number of 3-15.

[0029] The injection volume for temporary plugging can be 0.05-0.1 PV.

[0030] Step 200, determine the injection type of supercritical fluid according to the crude oil viscosity and asphaltene content. The specific corresponding relationship is shown in the following Table 2:

[0031] Table 2

[0032]

[0033] The supercritical aromatic pre-solvent slug solvent may be one or more of xylene, naphtha, toluene, and condensate oil; the supercritical alkane pre-solvent slug may be one or more of C1-C10 light alkane solvents, preferably one or more of saturated and unsaturated hydrocarbons with a carbon number of 3-15; the CO 2 The solubilizer preferably occupies the CO 2 0.1% to 0.5% of the system; the CO 2 The solubilizing agent is, for example, one or more of ethanol, urea, acetone, ethane, ethylene glycol, and dimethyl ether; the non-condensable gas is, for example, N 2 , natural gas, methane, flue gas and combinations thereof.

[0034] Step 300, when the crude oil viscosity is higher than a predetermined value (eg, 1000 mPa.s), fracturing is performed according to a predetermined volume fracturing type. After fracturing is completed, supercritical fluid is injected according to a predetermined injection type, and synchronous heating is performed to shut down the well, for example, shutting down the well for 40 to 60 days.

[0035] Wherein, the displacement fluid of the volume fracturing can be supercritical CO 2 The composition of the thickening solution has a volume ratio of 0:1 to 1:1; the thickening agent in the thickening solution is, for example, one or more of xanthan gum, cellulose, and polymers; the molecular weight of the thickening agent is, for example, 1 million to 25 million, and the concentration in the aqueous solution is 400 to 1500 PPM.

[0036] The synchronous heating process specifically includes, for example, inserting a resistance heater into the well for synchronous heating at the same time as the supercritical liquid is injected, wherein the surface temperature of the resistance heater is 150-200°C and the heating power density is 1000-2000W / m. The electric heating is used to synergistically improve the gas injection development effect, thereby achieving the purpose of increasing production and recovery.

[0037] Specifically, when the crude oil viscosity is higher than 1000mPa.s (ground temperature 50°C), the front non-condensable gas and CO can be injected every 3 to 5 rounds. 2 A composition of a foaming agent + a solubilizing agent and water vapor. 2 The underground volume ratio of CO to water vapor is 1:1:10 to 1:5:5; 2 The foaming agent occupies the liquid CO2 0.5% to 2%; the water vapor is sub-supercritical water vapor.

[0038] Step 400, when the average reservoir pressure interpreted by the well test drops to a predetermined value (such as 4Mpa), supercritical fluid is injected into the reservoir for throughput production according to a predetermined injection type. When the crude oil viscosity is lower than a predetermined value (such as 1000mPa.s), a foaming agent is added to the injected supercritical fluid, and the well is shut down and kept warm for a certain period of time.

[0039] The foaming agent includes, for example, sulfates, sulfonates, phosphates and carboxylates. Specific examples of anionic foaming agents include ammonium dodecyl sulfate, sodium dodecyl sulfate or sodium dodecyl sulfate, sodium lauryl ether sulfate or sodium lauryl ether sulfate, sodium lauryl ether sulfate, dioctyl sodium sulfosuccinate, perfluorooctane sulfonic acid, perfluorobutane sulfonic acid, alkyl aryl ether phosphate and alkyl ether phosphate.

[0040] Step 500, start the well for production. When the daily oil production drops to a predetermined value (eg, 0.2-0.5 t / d), shut down the well and return to step 300.

[0041] The method described in this embodiment adopts different modes of unconventional volume fracturing + supercritical CO according to the development stage of different oil reservoirs and permeability heterogeneity (permeability gradient). 2 +Supercritical steam huff-and-puff method can create fractures in the formation for different development stages and heterogeneous reservoirs, expand the injection capacity of water vapor, and reduce the pressure of steam injection; in addition, this method adopts the method of increasing CO 2 Effect of CO 2 additive system, which can significantly increase CO 2 Solubility in oil reservoirs increases CO 2 injection capacity, and at the same time, can generate CO 2 Foam, suppressing CO 2 The release of gases such as CO 2 The residence time in crude oil greatly improves the flowability of crude oil, playing a role similar to foam oil, thereby increasing production.

[0042] In addition, underground electric heating and CO 2 Fluid coordination can significantly increase the reservoir temperature and avoid CO 2 The phenomenon of oil layer deasphalting blocking the oil layer during the injection and production process increases the CO 2 effect.

[0043] In summary, it has the following advantages and effects:

[0044] (1) This method uses different methods of unconventional volume fracturing + supercritical CO according to the development stage and permeability heterogeneity (permeability difference) of different reservoirs. 2 +Supercritical steam huff-and-puff method can create fractures in the formation, expand the water vapor injection capacity and reduce the steam injection pressure for different development stages and heterogeneous reservoirs;

[0045] (2) This method injects a pre-solvent plug before fracturing, which can significantly reduce viscosity and provide a basis for subsequent CO 2 and the injection of non-condensable gas to provide a flow channel; subsequently, CO 2 The main pre-gas slug can provide continuous energy by relying on the expansion of gas during the subsequent mining and pressure relief process, greatly extending the effective mining time of the throughput cycle;

[0046] (3) This method is effective in CO 2 Adding non-condensable gas can avoid CO 2 Under high pressure, the liquid cannot release elastic energy, and relies on the high compressibility of N2 to provide energy, playing the role of energy storage in throughput;

[0047] (4) This method further illustrates the improvement of CO 2 Effect of CO 2 Solventizing system, which can significantly increase the CO 2 Solubility in oil reservoirs increases CO 2 injection capacity, and at the same time, can generate CO 2 Foam, suppressing CO 2 The release of gases such as CO 2 The residence time in crude oil greatly improves the flowability of crude oil, playing a role similar to foam oil, thereby increasing production.

[0048] In order to further verify the above technical effects, the following experimental data are provided:

[0049] Example 1

[0050] The present embodiment provides a method for exploiting crude oil in a low-permeability and high-viscosity oil reservoir, which is an original undeveloped oil reservoir with a burial depth of 1,200 meters, an average permeability gradient of 6, a permeability of 2-12 mD, a surface 50°C crude oil viscosity of 188 mPa.s, and an asphaltene content of 2.5% by weight. It is a low-permeability and high-viscosity oil reservoir with a high viscosity and a low permeability.

[0051] This embodiment provides a method for cooperating with fracturing and supercritical fluid injection to produce crude oil, including the following specific steps:

[0052] 1) Use a multi-segment and multi-cluster approach to CO the oil layer 2 Energy storage volume fracturing; adding CO to fracturing fluid2 The solubilizing agent dimethyl ether is added in an amount of 0.1% of the volume of the fracturing fluid; after fracturing, the well is shut down for 40 days and then the well is opened for production;

[0053] 2) When the average reservoir pressure in the well test dropped to 4 MPa, CO was injected into the reservoir. 2 +CO 2 Solubilizer; the solubilizer is dimethyl ether, CO 2 The solubilizer occupies CO 2 0.1%-0.5% of the system;

[0054] 3) Shut down the well and keep it in a well for 40 days;

[0055] 4) Start production. When the daily oil production drops to 0.2t / d, repeat steps 2-4.

[0056] The composite fluid injection method for crude oil production in this embodiment achieves efficient development of the reservoir, which is different from the conventional CO injection method in adjacent well groups. 2 In comparison, the oil production per cycle reached 560 tons (the adjacent conventional CO 2 Throughput: 280 tons), the final steam throughput recovery rate reached 19% (adjacent conventional steam throughput: 11%).

[0057] Example 2

[0058] This embodiment provides a method for exploiting crude oil in a low-permeability and high-viscosity oil reservoir. The oil reservoir is an original undeveloped oil reservoir with a burial depth of 1,150 meters, an average permeability gradient of 8, a permeability of 10-80 mD, a crude oil viscosity of 578 mPa.s at 50°C on the ground, and an asphaltene content of 1.1% by weight. It is a low-permeability and high-viscosity oil reservoir.

[0059] This embodiment provides a method for cooperating with fracturing and supercritical fluid injection to produce crude oil, including the following specific steps:

[0060] 1) Expand capacity + CO 2 Energy storage volume fracturing; the expansion segment plug is to inject dimethyl ether solvent + 100℃ warm water segment plug into the oil well until the oil layer pressure reaches 0.5MPa above the formation fracture pressure; then, CO is used in a multi-stage and multi-cluster manner to 2 Energy storage volume fracturing; adding CO to fracturing fluid 2 The solubilizing agent dimethyl ether is added in an amount of 0.1% of the volume of the fracturing fluid; after fracturing, the well is shut down for 40 days and then the well is opened for production;

[0061] 2) When the average reservoir pressure in the well test dropped to 5 MPa, CO was injected into the reservoir. 2 + non-condensable gas + CO 2 wherein the non-condensable gas is nitrogen, the solubilizing agent is ethylene glycol, CO 2The solubilizer occupies CO 2 In addition, a foaming agent was added to the gas, the foaming agent was sodium dodecyl sulfate, the underground volume ratio of foam liquid to gas was 1:2, and the foaming agent concentration was 0.3% of the foam liquid concentration; the injection volume of the above fluid was 0.1PV, and the injection pressure reached CO 2 Above the critical pressure, specifically 25MPa;

[0062] 3) Shut down the well and keep it in a well for 30 days;

[0063] 4) Start production. When the daily oil production drops to 0.2t / d, repeat steps 2-4.

[0064] The supercritical fluid injection method for crude oil production in this embodiment achieves efficient development of the oil reservoir. Compared with the injection of conventional supercritical steam into adjacent well groups, the cycle oil production reaches 1190 tons (the adjacent conventional CO 2 : 450 tons), the final throughput recovery rate reached 39% (the adjacent conventional CO 2 Throughput: 20%).

[0065] Example 3

[0066] The present embodiment provides a method for exploiting crude oil in a low-permeability, high-viscosity oil reservoir, which is an oil reservoir that has been developed by steam injection in the early stage, with a burial depth of 1450 meters, an average permeability gradient of 15, a permeability of 10-150mD, a surface 50°C crude oil viscosity of 1378mPa.s, and an asphaltene content of 2.5% by weight, which is a low-permeability, high-viscosity, and highly heterogeneous oil reservoir.

[0067] This embodiment provides a method for cooperating with fracturing and supercritical fluid injection to produce crude oil, including the following specific steps:

[0068] 1) Carry out temporary blocking + CO 2 Energy storage volume fracturing; the temporary plugging plug is a temperature-sensitive temporary plugging chemical agent with a molecular weight of 10 million to 25 million; the concentration in the aqueous solution is 1400-2500 PPM; the injection volume of the temporary plugging construction is 0.05 PV; after the temporary plugging chemical agent is injected, a 150°C warm water plug is injected into the oil well to achieve high-temperature curing of the chemical agent and block large pores and high permeability channels; then CO 2 Energy storage volume fracturing; using a multi-stage and multi-cluster approach to CO 2 Energy storage volume fracturing;

[0069] 2) After the fracturing is completed, the well is shut down for 40 days and then opened for production. When the reservoir pressure drops below 5MPa according to the well test interpretation, supercritical fluid injection and huff-and-puff are started. At the same time, a resistance heater is lowered into the well for synchronous heating. The surface temperature of the heater is 150°C and the heating power density is 1000W / m;

[0070] 3) Inject supercritical aromatic hydrocarbon pre-solvent slug solvent + CO into the oil layer 2 +CO 2 Solubilizer + water vapor; wherein the supercritical aromatic pre-solvent slug solvent is naphtha; CO 2 The solubilizer occupies CO 2 0.5% of the system is acetone; CO 2 The underground ratio with water vapor is 1:5;

[0071] 4) Shut down the well and keep it in a well for 7 days;

[0072] 5) Start production. When the daily oil production drops to 0.2t / d, repeat steps 3-5.

[0073] The method for producing crude oil by injecting supercritical fluid in this embodiment realizes efficient development of the oil reservoir. Compared with the injection of conventional supercritical steam in the adjacent well group, the cycle oil production reaches 690 tons (adjacent conventional steam: 250 tons), and the final throughput recovery rate reaches 31% (adjacent conventional steam throughput: 11%).

[0074] Example 4

[0075] The present embodiment provides a method for exploiting crude oil in a low-permeability, high-viscosity oil reservoir, which is a previously developed oil reservoir with steam injection, a burial depth of 1,650 meters, an average permeability gradient of 8, a permeability of 20-160 mD, a surface 50° C. crude oil viscosity of 4,378 mPa.s, an asphaltene content of 2.5% by weight, and a low-permeability, high-viscosity, highly heterogeneous oil reservoir.

[0076] This embodiment provides a method for cooperating with fracturing and supercritical fluid injection to produce crude oil, including the following specific steps:

[0077] 1) Expand capacity + CO 2 Energy storage volume fracturing; the expansion segment plug is to inject naphtha solvent + 80℃ warm water segment plug into the oil well until the oil layer pressure reaches 0.5MPa above the formation fracture pressure; then CO is used in a multi-stage and multi-cluster manner to 2 Energy storage volume fracturing;

[0078] 2) After the fracturing is completed, the well is shut down for 40 days and then opened for production. When the reservoir pressure drops below 5MPa according to the well test interpretation, supercritical fluid injection and huff-and-puff are started. At the same time, a resistance heater is lowered into the well for synchronous heating. The surface temperature of the heater is 200°C and the heating power density is 2000W / m;

[0079] 3) Inject supercritical aromatic hydrocarbon pre-solvent slug solvent + CO into the oil layer 2 +CO 2 Solubilizer + water vapor; among them, the supercritical aromatic pre-solvent slug solvent is condensate oil; CO 2The solubilizer occupies CO 2 0.5% of the system is ethylene glycol; CO 2 The underground ratio with water vapor is 1:5;

[0080] 4) Shut down the well and keep it in a well for 7 days;

[0081] 5) Start production. When the daily oil production drops to 0.2t / d, repeat steps 3-5.

[0082] The method for extracting crude oil by injecting supercritical fluid in this embodiment realizes the efficient development of the oil reservoir. Compared with the injection of conventional supercritical steam in the adjacent well group, the cycle oil production reaches 890 tons (adjacent conventional steam: 130 tons), and the final throughput recovery rate reaches 28% (adjacent conventional steam throughput: 10%).

[0083] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing crude oil from a low-permeability and high-viscosity oil reservoir, characterized in that: include: When the crude oil viscosity is higher than a predetermined value, fracturing is performed according to a predetermined volume fracturing type. After fracturing is completed, supercritical fluid is injected according to a predetermined injection type, and synchronous heating is performed to soak the well. When the average reservoir pressure interpreted by the well test drops to a predetermined value, supercritical fluid is injected into the reservoir for huff and puff production according to the predetermined injection type. When the crude oil viscosity is lower than the predetermined value, a foaming agent is added to the injected supercritical fluid to soak the well. Start production, and when the daily oil production drops to a predetermined value, shut down the well and repeat the above process; The volume fracturing type is determined according to the production stage and the permeability difference; the injection type of the supercritical fluid is determined according to the crude oil viscosity and asphaltene content.

2. The method according to claim 1, characterized in that Determining the volume fracturing type according to the production stage and the permeability difference includes: When the exploitation stage is the original reservoir and the permeability difference is greater than 10, the volume fracturing type is determined to be: CO2 energy storage volume fracturing; When the exploitation stage is the original reservoir and the permeability difference is less than or equal to 10, the volume fracturing type is determined to be: expansion + CO2 energy storage volume fracturing; When the exploitation stage is a developed reservoir and the permeability difference is greater than 10, the volume fracturing type is determined to be: temporary plugging + CO2 energy storage volume fracturing; When the exploitation stage is a developed reservoir and the permeability difference is less than or equal to 10, the volume fracturing type is determined to be: capacity expansion + CO2 energy storage volume fracturing.

3. The method according to claim 2, characterized in that The expansion comprises: injecting a solvent plug containing 80-100°C warm water into the oil well until the oil layer pressure reaches 0.5 MPa above the formation fracture pressure; The mass ratio of the solvent to the warm water is 1:1 to 1:10; The solvent slug is one or more of alkanes with carbon numbers between 3 and 15, aromatic hydrocarbons, naphtha, petroleum ether, diesel, dimethyl ether, and ethanol.

4. The method according to claim 2, characterized in that: The injection volume for temporary plugging is 0.05-0.1 PV.

5. The method according to claim 1, characterized in that The types of supercritical fluid injection determined by crude oil viscosity and asphaltene content include: In the case where the crude oil viscosity is greater than 1000 mPa.s and the asphaltene content is greater than 2 wt%, the injection type is determined to be: supercritical aromatic pre-solvent slug solvent + CO2 + CO2 solubilizer + water vapor; In the case where the crude oil viscosity is greater than 1000 mPa.s and the asphaltene content is less than or equal to 2 wt%, the injection type is determined to be: supercritical alkane pre-solvent slug + CO2 + CO2 solubilizer + water vapor; When the crude oil viscosity is less than or equal to 1000 mPa.s and the asphaltene content is greater than 2 wt%, the injection type is determined to be: CO2+CO2 solubilizer; When the crude oil viscosity is less than or equal to 1000 mPa.s and the asphaltene content is less than or equal to 2 wt %, the injection type is determined to be: CO2+non-condensable gas+CO2 solubilizing agent.

6. The method according to claim 5, characterized in that: The supercritical aromatic hydrocarbon pre-solvent slug solvent is one or more of xylene, naphtha, toluene and condensate oil.

7. The method according to claim 5, characterized in that: The supercritical alkane pre-solvent slug is one or more of C1-C10 light alkane solvents.

8. The method according to claim 7, characterized in that: The supercritical alkane pre-solvent slug is one or more of saturated hydrocarbons and unsaturated hydrocarbons with carbon numbers ranging from 3 to 15.

9. The method according to claim 5, characterized in that: The CO2 solubilizer occupies 0.1% to 0.5% of the CO2 system; the CO2 solubilizer is one or more of ethanol, urea, acetone, ethane, ethylene glycol, and dimethyl ether.

10. The method according to claim 5, characterized in that: The non-condensable gas is N2, natural gas, methane, flue gas and a combination thereof.

11. The method according to claim 1, characterized in that: The displacement fluid used in the fracturing is a combination of supercritical CO2 and a viscosified solution, with a volume ratio of 0:1 to 1:1; The thickening agent in the thickened solution is one or more of xanthan gum, cellulose, and polymer; The molecular weight of the thickener is 1 million to 25 million, and the concentration in the aqueous solution is 400 to 1500 PPM.

12. The method according to claim 1, characterized in that: The synchronous heating comprises: while starting to inject the supercritical liquid, lowering a resistance heater into the well for synchronous heating, the surface temperature of the resistance heater is 150-200° C., and the heating power density is 1000-2000 W / m.

13. The method according to claim 1, characterized in that: The foaming agents include sulfates, sulfonates, phosphates and carboxylates.

14. The method according to claim 1, characterized in that The process of injecting the supercritical fluid when the viscosity of the crude oil is higher than a predetermined value includes: injecting a combination of pre-condensable gas, CO2 foaming agent + solubilizing agent and water vapor every 3 to 5 rounds; Among them, the underground volume ratio of the non-condensable gas to CO2 and water vapor is: 1:1:10 to 1:5:5; the CO2 foaming agent occupies 0.5% to 2% of the liquid CO2; and the water vapor is sub-supercritical water vapor.

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