Method for improving recovery efficiency and burying rate of variable-stage CO2 injection and reverse pressure driving

Abstract

The invention provides a method for improving the recovery efficiency and the burying rate of variable-stage CO2 injection and reverse pressure driving. Comprising the following steps: scanning an experimental rock core injected with crude oil to obtain a first nuclear magnetic resonance curve, and injecting fracturing fluid with a preset volume into the experimental rock core from a preset first port; wherein the experimental rock core is located in the preset container, and the preset container is provided with a preset first port and a preset second port; on the basis of a preset environmental condition, performing soaking treatment on the experimental rock core in the preset container; on the basis of preset CO2 injection stage configuration information, CO2 is injected into the experimental rock core from a preset second port, and a second nuclear magnetic resonance curve is obtained; according to the curve area of the first nuclear magnetic resonance curve and the curve area of the second nuclear magnetic resonance curve, the recovery rate of the experimental rock core is determined, and according to the volume of the injected CO2, the embedding rate of the experimental rock core is determined. CO2 is injected from the second port through preset CO2 injection stage configuration information, and the storage rate and the recovery rate are improved.

Description

Technical Field

[0001] The present application relates to the technical field of shale / tight oil reservoir exploitation, and in particular to a method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive. Background Art

[0002] The pore structure of shale / tight oil reservoirs is complex, characterized by low porosity and low permeability, and the fluidity of oil and gas in the reservoir is poor.

[0003] Traditional volume fracturing and conventional water injection development are difficult to achieve ideal development results. Although fracturing technology can effectively increase the conductivity of the reservoir, the connectivity of the pores between the fractures in shale / tight oil reservoirs is poor, resulting in limited utilization. Therefore, it is urgent to propose a method to improve the recovery rate of shale / tight oil reservoirs. Summary of the invention

[0004] The present application provides a method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive, which is used to solve the technical problem of low recovery rate of shale / tight oil reservoirs.

[0005] In a first aspect, the present application provides a method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive, comprising:

[0006] The experimental core injected with crude oil is scanned to obtain a first nuclear magnetic resonance curve, and a preset volume of fracturing fluid is injected into the experimental core from a preset first port; wherein the experimental core is located in a preset container, and a preset first port and a preset second port are provided on the preset container, and the first nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core;

[0007] Based on the preset environmental conditions, the experimental core in the preset container is soaked;

[0008] Based on the preset CO2 injection phase configuration information, CO2 is injected into the experimental core from the preset second port to obtain a second nuclear magnetic resonance curve; wherein the second nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core;

[0009] The recovery rate of the experimental core is determined according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, and the burial rate of the experimental core is determined according to the volume of injected CO2; wherein the recovery rate represents the ratio of the amount of oil obtained from the experimental core to the total amount of oil in the experimental core, and the burial rate represents the ratio of CO2 sealed in the core.

[0010] Among them, in the present application, the preset CO2 injection stage configuration information includes the initial velocity and velocity change rate of the CO2 injection. Based on the preset CO2 injection stage configuration information, CO2 is injected into the experimental core from the preset second port to obtain a second nuclear magnetic resonance curve, including:

[0011] According to the initial velocity and the velocity change rate, CO2 is injected into the experimental core from the preset second port to obtain the saturation of the experimental core; wherein the saturation represents the distribution of CO2 in the experimental core;

[0012] If the saturation of the experimental core does not change within the preset time period, the second nuclear magnetic resonance curve at the current moment is obtained.

[0013] Wherein, in the present application, the velocity change rate represents the increase in the velocity of injecting CO2; according to the initial velocity and the velocity change rate, injecting CO2 into the experimental core from the preset second port to obtain the saturation of the experimental core includes:

[0014] According to the initial velocity, CO2 is injected into the experimental core from the preset second port;

[0015] If it is determined that the injection time reaches a preset time threshold, CO2 is injected into the experimental core from a preset second port according to the velocity change rate, and the saturation of the experimental core is obtained in real time.

[0016] Among them, in the present application, the recovery factor of the experimental core is determined according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, including:

[0017] determining an area difference between a curve area of ​​the first nuclear magnetic resonance curve and a curve area of ​​the second nuclear magnetic resonance curve;

[0018] The first recovery factor of the experimental core is obtained according to the area difference and the curve area of ​​the second nuclear magnetic resonance curve; wherein the first recovery factor represents the recovery factor of the experimental core after CO2 is injected.

[0019] Among them, in this application, it also includes:

[0020] Obtaining the imbibition distance, core length, initial water saturation of the core, and water saturation of the preset second port of the experimental core after well soaking treatment; wherein the imbibition distance represents the distance of the fracturing fluid imbibing in the experimental core;

[0021] The second recovery factor of the experimental core is determined according to the imbibition distance, the core length, the initial water saturation of the core, and the water saturation of the second port; wherein the second recovery factor represents the recovery factor of the experimental core after the fracturing fluid is injected.

[0022] Among them, in this application, the burial rate of the experimental core is determined according to the volume of injected CO2, including:

[0023] Determining the volume of CO2 released from the preset first port;

[0024] The burial rate of the experimental core is determined based on the volume of CO2 injected and the volume of CO2 released.

[0025] Among them, in this application, it also includes:

[0026] Obtain the initial oil content information of the experimental core and the oil content information of the experimental core before CO2 injection; the oil content information represents the oil saturation of the experimental core;

[0027] According to the initial oil content information of the experimental core and the oil content information of the experimental core before CO2 injection, the third recovery factor of the experimental core is obtained; wherein the third recovery factor represents the recovery factor of the experimental core before the CO2 injection process.

[0028] In a second aspect, the present application provides a device for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive, comprising:

[0029] A first obtaining unit is used to scan and process the experimental core injected with crude oil to obtain a first nuclear magnetic resonance curve, and inject a preset volume of fracturing fluid into the experimental core from a preset first port; wherein the experimental core is located in a preset container, and a preset first port and a preset second port are provided on the preset container, and the first nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core;

[0030] A processing unit, used for performing well soaking treatment on the experimental core in the preset container based on preset environmental conditions;

[0031] A second obtaining unit is used to inject CO2 into the experimental core from a preset second port based on preset CO2 injection phase configuration information to obtain a second nuclear magnetic resonance curve; wherein the second nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core;

[0032] A determination unit is used to determine the recovery rate of the experimental core according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, and to determine the burial rate of the experimental core according to the volume of injected CO2; wherein the recovery rate represents the ratio of the amount of oil obtained from the experimental core to the total amount of oil in the experimental core, and the burial rate represents the ratio of CO2 sealed in the core.

[0033] In a third aspect, the present application provides an electronic device, comprising: a processor, and a memory communicatively connected to the processor;

[0034] Memory stores computer-executable instructions;

[0035] The processor executes the computer-executable instructions stored in the memory to implement the method in the present application.

[0036] In a fourth aspect, the present application provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the method of the present application.

[0037] In a fifth aspect, the present application provides a computer program product, comprising: a computer program, which, when executed by a processor, implements the above first aspect and / or various possible implementations of the first aspect.

[0038] The present application provides a method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive, by scanning and processing the experimental core injected with crude oil, obtaining a first nuclear magnetic resonance curve, and injecting a preset volume of fracturing fluid into the experimental core from a preset first port; wherein the experimental core is located in a preset container, and a preset first port and a second port are provided on the preset container, and the first nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core. Based on the preset environmental conditions, the experimental core in the preset container is subjected to well soaking treatment. Based on the preset CO2 injection stage configuration information, CO2 is injected into the experimental core from the preset second port to obtain a second nuclear magnetic resonance curve; wherein the second nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core. By injecting CO2 and fracturing fluid from different preset ports respectively, it is more in line with the characteristics of the experimental core, thereby improving the recovery rate. The recovery rate of the experimental core is determined according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, and the burial rate of the experimental core is determined according to the volume of injected CO2; wherein the recovery rate represents the ratio of the amount of oil obtained from the experimental core to the total amount of oil in the experimental core, and the burial rate represents the ratio of CO2 sealed in the core. Based on the preset CO2 injection stage configuration information, the injection of CO2 is more suitable for the characteristics of the experimental core, thereby improving the recovery rate and the burial rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0040] Figure 1 A schematic flow chart of a method for improving the recovery rate and storage rate of a variable-stage CO2 injection and reverse pressure drive provided in an embodiment of the present application;

[0041] Figure 2A schematic diagram of a preset container provided in an embodiment of the present application;

[0042] Figure 3 A schematic flow chart of another method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in an embodiment of the present application;

[0043] Figure 4 A schematic diagram of the structure of the experimental device provided in the embodiment of the present application;

[0044] Figure 5 A schematic diagram of the evolution law of the imbibition distance and saturation provided in an embodiment of the present application;

[0045] Figure 6 A schematic diagram of the recovery rate and pore utilization law of a variable-stage CO2 reverse pressure drive provided in an embodiment of the present application;

[0046] Figure 7 A schematic diagram of the structure of a device for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in an embodiment of the present application;

[0047] Figure 8 A schematic diagram of the structure of a device for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in an embodiment of the present application;

[0048] Fig. 9 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application.

[0049] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0050] 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 implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0051] At present, in shale / tight oil reservoirs, the connectivity of pores between fractures is poor, resulting in limited utilization. Water injection development cannot displace residual oil in the reservoir due to the low sweep coefficient of fluid in micropores. In addition, the application of conventional reverse pressure drive technology in shale and tight reservoirs also faces many challenges. Due to the ultra-low permeability of the reservoir, the injected fluid during the reverse pressure drive process is difficult to enter the deep reservoir, resulting in limited sweep volume, reduced oil displacement efficiency, and affecting the final recovery rate. For conventional CO2 displacement technology, although it has the advantages of reducing interfacial tension, promoting miscibility, reducing viscosity, and changing wettability, in shale / tight oil reservoirs, CO2 has poor fluidity in the reservoir, and the injected CO2 is easy to quickly break through the high permeability channel, with an effective sweep range, and cannot effectively displace the residual oil in the reservoir, resulting in poor development of shale / tight oil reservoirs. In addition, no relevant research has been conducted on the quantitative characterization of the reverse pressure drive burial rate enhanced by CO2 injection in the variable stage of shale / tight oil reservoirs. In summary, the application effect of conventional reverse pressure drive and CO2 flooding technology in shale / tight oil reservoirs is limited and their potential recovery rate cannot be fully utilized.

[0052] The present application provides a method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive, which obtains a first nuclear magnetic resonance curve by scanning an experimental core injected with crude oil, and injects a preset volume of fracturing fluid into the experimental core from a preset first port; wherein the experimental core is located in a preset container, and a preset first port and a second port are provided on the preset container, and the first nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core; based on preset environmental conditions, the experimental core in the preset container is subjected to well soaking treatment; based on preset CO2 injection stage configuration information, CO2 is injected into the experimental core from a preset second port to obtain a second nuclear magnetic resonance curve; wherein the second nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core; by respectively injecting CO2 and fracturing fluid from different preset ports, it is more in line with the characteristics of the experimental core, thereby improving the recovery rate. The recovery rate of the experimental core is determined according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, and the burial rate of the experimental core is determined according to the volume of injected CO2; wherein the recovery rate represents the ratio of the amount of oil obtained from the experimental core to the total amount of oil in the experimental core, and the burial rate represents the ratio of CO2 sealed in the core. Based on the preset CO2 injection stage configuration information, the injection of CO2 is more suitable for the characteristics of the experimental core, thereby improving the recovery rate and the burial rate.

[0053] Among them, the relaxation time in nuclear magnetic resonance (MRI) refers to the time required for the nucleus to recover from the excited state to the equilibrium state. This process involves two main relaxation times: T1 (longitudinal relaxation time) and T2 (transverse relaxation time). T1 (longitudinal relaxation time) refers to the time required for the magnetization vector of the nucleus to recover from the direction perpendicular to the magnetic field to the direction parallel to the magnetic field in the magnetic field. T1 relaxation time describes how fast the spin system recovers from the excited state to the thermal equilibrium state. In MRI, T1-weighted imaging mainly reflects the difference in T1 values ​​between tissues, such as fat, melanin, and protein present bright high signals, while cerebrospinal fluid (CSF) presents low signals. T2 (transverse relaxation time): This refers to the decay and disappearance time of the magnetization vector of the nucleus in the plane perpendicular to the magnetic field in the magnetic field. T2 relaxation time reflects the decay rate of the transverse magnetization component, which is caused by mutual interference between nuclei and the inhomogeneity of the magnetic field. On T2-weighted images, cerebrospinal fluid (CSF) has a long relaxation time and appears as a bright high signal.

[0054] Recovery factor refers to the oil recovery rate, which is the ratio between the amount of oil actually extracted from the reservoir and the original geological reserves (total amount of crude oil) in the reservoir.

[0055] In petroleum engineering, saturation usually refers to the volume fraction of a certain fluid (such as water, oil or gas) in the pores of the reservoir rock. For example, oil saturation refers to the proportion of oil in the pore space. Saturation is an important parameter for evaluating the reservoir properties and predicting the recovery rate.

[0056] The storage efficiency refers to the efficiency with which captured CO2 can be safely stored in geological reservoirs over the long term. This concept has become particularly important in the context of addressing climate change and reducing greenhouse gas emissions.

[0057] Figure 1 The present invention provides a flow chart of a method for improving the recovery rate and storage rate of a variable-stage CO2 injection and reverse pressure drive. Figure 1 As shown, the execution subject of the method can be a server or other servers, and this embodiment is not particularly limited here. Figure 1 As shown, the method includes:

[0058] S101, scanning and processing the experimental core injected with crude oil to obtain a first nuclear magnetic resonance curve, and injecting a preset volume of fracturing fluid into the experimental core from a preset first port; wherein the experimental core is located in a preset container, and a preset first port and a preset second port are provided on the preset container, and the first nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core;

[0059] Among them, the experimental core refers to a core whose porosity and permeability are consistent with those of the actual reservoir, but whose size is reduced, for example: any one of a shale core and a tight oil reservoir core. The first, second, and third in this application do not represent the order of execution, but are only used to distinguish different technical features. Crude oil can be injected into the experimental core through the first port, or through the second port. In most cases, crude oil is injected into the experimental core through the second port. The entire experimental process is online CT and offline nuclear magnetic resonance, so the nuclear magnetic resonance curve can be obtained except at the beginning (i.e. after the injection of crude oil) and the end (after the injection of CO2), and it cannot be obtained at other times.

[0060] Figure 2 A schematic diagram of a preset container provided in an embodiment of the present application, Figure 2 In the embodiment, the experimental core is placed in the preset container 12, the preset container is a core holder, and two ports are arranged on the preset container, namely the first port 11 and the second port 16, both of which can be used to inject substances. In this embodiment, the preset first port is the outlet port, which is used to inject fracturing fluid. When the fracturing fluid is injected, the outlet port is consistent with the formation pressure. When the CO2 injection is completed, the outlet port will be connected to the atmospheric pressure. At this time, the temperature of the outlet port is 25°C, 0MPa. The preset second port is the inlet port, which is used to inject CO2. The inlet port is the formation temperature and formation pressure. The specific values ​​need to be determined in combination with the actual formation block.

[0061] The first port and the second port are provided for reverse pressure driving operation, wherein the reverse pressure driving means: injecting CO2 through the inlet port and injecting fracturing fluid through the outlet port.

[0062] The nuclear magnetic resonance curve is a curve obtained by a nuclear magnetic resonance device, wherein the horizontal axis is the relaxation time and the vertical axis is the signal intensity.

[0063] Crude oil refers to experimental crude oil, which refers to the crude oil prepared in the laboratory under experimental conditions based on actual formation crude oil.

[0064] The experimental core is pre-injected with crude oil, which means: the experimental core is cut and washed with oil, dried, weighed, and the porosity and permeability of the core are measured. After the experimental core is determined to be any one of a shale core and a tight oil reservoir core, the experimental core is vacuumed using a vacuum experimental device, and crude oil is injected into the experimental core through the inlet end so that the outlet end can stably discharge liquid.

[0065] The preset volume of fracturing fluid meets:

[0066]

[0067] Among them, v lab It refers to converting the displacement on site into the displacement for indoor experiments. It generally refers to the displacement of fracturing fluid injected in indoor experiments.field is the displacement of on-site construction, B p is the area of ​​a single hole in the reverse pressure drive on site, N p The number of holes drilled on site.

[0068] The experimental core is placed in a preset container (i.e., core holder), and crude oil is injected into the core from the inlet end until the outlet end is stable. Then, the injection of crude oil is stopped, and the experimental core injected with crude oil is scanned to obtain the first NMR curve. V is injected from the outlet end. lab volume of fracturing fluid.

[0069] S102, based on preset environmental conditions, performing well soaking treatment on the experimental core in the preset container;

[0070] The preset environmental conditions refer to the formation temperature and formation pressure, and the soaking time meets the preset values. The specific values ​​of the formation temperature and formation pressure need to be determined in combination with the actual formation block.

[0071] Well soaking treatment refers to a technology that uses multiple mechanisms such as fracturing fluid and imbibition to increase shale oil production.

[0072] Well stewing time meets:

[0073]

[0074] Among them, t lab refers to the soaking time, C is the core property parameter, that is, the Young's modulus of the experimental rock sample, μ m is the viscosity of the fluid used in the experimental core, i.e., the viscosity of the fracturing fluid, r is the core radius, Q lab is the experimental core flow rate, that is, the speed of the fluid (the fluid is the fracturing fluid) passing through a certain section of the core, cosθ is the contact angle after the experiment, that is, the contact angle between the experimental crude oil and the experimental core surface, t field This is the time for the well to be stewed on site.

[0075] The temperature in the preset container (i.e. core holder) is adjusted to the formation temperature and formation pressure, and t lab Duration of stewing treatment.

[0076] S103, based on the preset CO2 injection phase configuration information, inject CO2 into the experimental core from the preset second port to obtain a second nuclear magnetic resonance curve; wherein the second nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core;

[0077] Among them, the preset CO2 injection stage configuration information includes the initial CO2 injection speed and the rate of change of CO2 injection. The uniform CO2 injection speed at the oil field site is obtained as the conventional speed. Reduce the conventional speed as the initial CO2 injection speed. For example: the conventional injection speed is 0.1mL / min, so the initial CO2 injection speed is 0.05mL / min. The rate of change of CO2 injection refers to the gradual increase of CO2 injection speed over time. The rate of change of CO2 injection can also refer to the gradual increase of CO2 injection speed according to the change of recovery rate. The rate of change of CO2 injection can also refer to the gradual increase of CO2 injection speed by comprehensively considering the change of recovery rate and time.

[0078] Inject CO2 through the inlet at the initial rate and gradually increase the CO2 injection rate until the core saturation no longer changes, then stop injecting CO2. 2， Acquire a second NMR curve.

[0079] In the embodiment of the present application, the preset CO2 injection stage configuration information includes the initial velocity and velocity change rate of the CO2 injection. Based on the preset CO2 injection stage configuration information, CO2 is injected into the experimental core from the preset second port to obtain a second nuclear magnetic resonance curve, including:

[0080] According to the initial velocity and the velocity change rate, CO2 is injected into the experimental core from the preset second port to obtain the saturation of the experimental core; wherein the saturation represents the distribution of CO2 in the experimental core;

[0081] If the saturation of the experimental core does not change within the preset time period, the second nuclear magnetic resonance curve at the current moment is obtained.

[0082] The uniform injection speed of CO2 at the oil field is obtained as the normal speed. The normal speed is reduced to serve as the initial injection speed of CO2. For example, if the normal injection speed is 0.1 mL (millilite, milliliters) / min, the initial injection speed of CO2 is 0.05 mL / min.

[0083] The rate of change of injected CO2 can refer to adjusting the CO2 injection rate according to the rate of change of recovery factor (i.e. the increase in recovery factor). For example, the recovery factor at each moment when CO2 is injected is obtained. When CO2 is injected at the initial CO2 injection rate, there is no obvious change in recovery factor as CO2 is injected. In this case, the CO2 injection rate needs to be increased. The rate of change of injected CO2 can also refer to gradually increasing the CO2 injection rate over time.

[0084] In the early stage of CO2 injection, CO2 is injected at the initial injection rate so that CO2 can enter all parts of the reservoir more evenly and promote the miscibility of CO2 and crude oil. Miscibility refers to the formation of a single phase between CO2 and crude oil. In the middle stage of CO2 injection, the injection rate is gradually increased. After CO2 begins to be distributed more evenly, the injection rate is appropriately increased to push more experimental crude oil to the production end and prevent CO2 from being retained. In the later stage, the injection rate is increased. In the late stage of CO2 injection, the remaining oil is often distributed in low permeability areas. At this time, a higher driving force is required to push this part of the remaining oil to the production end. When the saturation of each section of the experimental core remains unchanged, the injection of CO2 is terminated, and the second nuclear magnetic resonance curve at the current moment is obtained, wherein the initial injection rate of CO2 can be 0.05mL / min, the injection rate of CO2 can be 0.1mL / min in the middle stage of CO2 injection, and the injection rate of CO2 can be 0.15mL / min in the late stage of CO2 injection.

[0085] The advantage of this setting is that by combining the nuclear magnetic resonance curve and variable-speed CO2 injection, precise management of the CO2 oil recovery process is achieved, which can significantly improve the recovery rate of the experimental core and the CO2 storage rate.

[0086] In the embodiment of the present application, the velocity change rate represents the increase in the velocity of injecting CO2; according to the initial velocity and the velocity change rate, CO2 is injected into the experimental core from the preset second port to obtain the saturation of the experimental core, including:

[0087] According to the initial velocity, CO2 is injected into the experimental core from the preset second port;

[0088] If it is determined that the injection time reaches a preset time threshold, CO2 is injected into the experimental core from a preset second port according to the velocity change rate, and the saturation of the experimental core is obtained in real time.

[0089] The preset time threshold refers to the time when the CO2 injection rate changes, including: the time when the CO2 injection rate changes from the initial stage to the middle stage, and the time when the CO2 injection rate changes from the middle stage to the late stage.

[0090] The saturation of the experimental core is obtained in real time, and whether to continue injecting CO2 is determined based on the saturation of the experimental core. When the saturation of each section of the experimental core is changing, CO2 injection needs to continue. When the saturation of each section of the experimental core remains unchanged, CO2 injection is stopped.

[0091] The initial rate can be 0.05mL / min. In the early stage of CO2 injection, CO2 is injected at the initial CO2 injection rate so that CO2 can enter various parts of the reservoir more evenly and promote the miscibility of CO2 and crude oil. Miscibility refers to the formation of a single phase between CO2 and crude oil. In the middle stage of CO2 injection, the injection rate is gradually increased. After CO2 begins to be distributed more evenly, the injection rate is appropriately increased to push more experimental crude oil to the production end and prevent CO2 from being retained. In the later stage, the injection rate is increased. In the later stage of CO2 injection, the remaining oil is often distributed in low permeability areas. At this time, a higher driving force is required to push this part of the remaining oil to the production end. When the saturation of each section of the experimental core remains unchanged, stop injecting CO2.

[0092] The advantage of this setting is that by combining the control of time threshold and velocity change rate, as well as real-time saturation monitoring, refined management of the CO2 injection process can be achieved, which can significantly improve the recovery rate and CO2 storage rate.

[0093] S104. Determine the recovery rate of the experimental core according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, and determine the burial rate of the experimental core according to the volume of injected CO2; wherein the recovery rate represents the ratio of the amount of oil obtained from the experimental core to the total amount of oil in the experimental core, and the burial rate represents the ratio of CO2 sealed in the core.

[0094] The recovery rate of the experimental core can be obtained by substituting the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve into a preset formula for calculating the recovery rate. The CO2 burial rate in the experimental core can be obtained by substituting the injected CO2 volume into another preset formula for calculating the burial rate.

[0095] In the embodiment of the present application, the recovery factor of the experimental core is determined according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, including:

[0096] determining an area difference between a curve area of ​​the first nuclear magnetic resonance curve and a curve area of ​​the second nuclear magnetic resonance curve;

[0097] The first recovery factor of the experimental core is obtained according to the area difference and the curve area of ​​the second nuclear magnetic resonance curve; wherein the first recovery factor represents the recovery factor of the experimental core after CO2 is injected.

[0098] Among them, based on the change in the signal value of the nuclear magnetic resonance curve before and after the injection of CO2 (that is, the area difference between the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve), the recovery rate of the injected CO2 can be obtained.

[0099] The method to obtain the first recovery factor is:

[0100]

[0101] Wherein, R1 is the first recovery factor, A1 is the curve area of ​​the first nuclear magnetic resonance curve, A2 is the curve area of ​​the second nuclear magnetic resonance curve, and A1-A2 represents the area difference.

[0102] The advantage of this setting is that based on the changes in the signal value of the nuclear magnetic resonance curve before and after the injection of CO2 and through the analysis of the area of ​​the nuclear magnetic resonance curve, the recovery factor after CO2 flooding can be accurately evaluated and optimized, thereby improving the technical effects and economic benefits in experiments and practical applications.

[0103] In the embodiment of the present application, it also includes:

[0104] Obtaining the imbibition distance, core length, initial water saturation of the core, and water saturation of the preset second port of the experimental core after well soaking treatment; wherein the imbibition distance represents the distance of the fracturing fluid imbibing in the experimental core;

[0105] The second recovery factor of the experimental core is determined according to the imbibition distance, the core length, the initial water saturation of the core, and the water saturation of the second port; wherein the second recovery factor represents the recovery factor of the experimental core after the fracturing fluid is injected.

[0106] Among them, the imbibition distance is the reverse imbibition distance of the fracturing fluid, which can be obtained through the experimental core saturation change curve over time, that is, the saturation change at a predetermined time is the reverse imbibition distance of the fracturing fluid.

[0107] Substituting the imbibition distance, core length, initial water saturation of the core, and water saturation of the second port into the second recovery formula, the recovery of the experimental core after injection of fracturing fluid and before soaking treatment can be obtained.

[0108] The second recovery factor formula is:

[0109]

[0110] Among them, R o is the recovery factor without considering the soaking treatment, X f is the reverse imbibition distance of the fracturing fluid, S winj is the water saturation at the inlet (i.e., the second port), x max is the core length.

[0111] The benefit of this setup is that by calculating and analyzing the second recovery factor (i.e., the recovery factor after wellbore treatment and before CO2 injection), it can provide important evaluation and optimization opportunities for wellbore treatment. This method not only improves the accuracy and reliability of the experiment, can improve the recovery factor, but also provides valuable guidance for actual oilfield development.

[0112] In the embodiment of the present application, the burial rate of the experimental core is determined according to the volume of injected CO2, including:

[0113] Determining the volume of CO2 released from the preset first port;

[0114] The burial rate of the experimental core is determined based on the volume of CO2 injected and the volume of CO2 released.

[0115] Among them, the volume of CO2 released from the outlet end (i.e., the first port) is obtained, and the volume of CO2 injected from the inlet end (i.e., the second port) is obtained. The volume of CO2 released from the outlet end and the volume of CO2 injected from the inlet end are substituted into the preset formula for obtaining the burial rate of the experimental core, and the burial rate of CO2 in the experimental core can be obtained.

[0116] The preset burial rate formula for obtaining experimental cores is:

[0117]

[0118] Among them, V IE is the volume of CO2 injected under injection conditions, cm 3 , that is, the volume of CO2 injected through the injection end under the conditions of formation temperature and formation pressure; P E is the injection pressure, MPa, i.e., the formation pressure; Z E is the CO2 deviation factor at injection temperature and pressure, that is, the CO2 deviation factor at formation temperature and formation pressure; Z O is the CO2 deviation factor at the outlet temperature and pressure, that is, the CO2 deviation factor at atmospheric pressure and room temperature (25°C); P O is the outlet pressure, i.e. atmospheric pressure, MPa; V R It is the volume of CO2 released under the outlet conditions, cm3, that is, the volume of CO2 released at the outlet under atmospheric pressure and room temperature.

[0119] The benefit of this setup is that by determining the volume of injected and released CO2 to calculate the storage rate, it can provide important technical support and optimization opportunities for CO2 geological storage and oil recovery processes. This method not only improves the accuracy and reliability of the experiment, but also provides valuable guidance for practical applications.

[0120] In the embodiment of the present application, it also includes:

[0121] Obtain the initial oil content information of the experimental core and the oil content information of the experimental core before CO2 injection; the oil content information represents the oil saturation of the experimental core;

[0122] According to the initial oil content information of the experimental core and the oil content information of the experimental core before CO2 injection, the third recovery factor of the experimental core is obtained; wherein the third recovery factor represents the recovery factor of the experimental core before the CO2 injection process.

[0123] The initial oil content information of the experimental core refers to the initial oil saturation of the experimental core.

[0124] The oil content information of the experimental core before CO2 injection refers to the oil saturation of the experimental core before CO2 injection.

[0125] Substituting the initial oil content information of the experimental core and the oil content information of the experimental core before CO2 injection into the formula for obtaining the third recovery factor, the third recovery factor of the experimental core before the CO2 injection process can be obtained. Substituting the initial oil content information of the experimental core and the oil content information of the experimental core after CO2 injection into the formula for obtaining the third recovery factor can obtain the second recovery factor of the experimental core after the CO2 injection process.

[0126] The formula for obtaining the third recovery factor is:

[0127]

[0128] Where: R on Characterizes the recovery rate after CO2 injection and the recovery rate before CO2 injection, V im is the displacement volume, V o is the initial oil-containing volume, S oi is the initial oil content information of the experimental core, x max is the core length,

[0129] S o (x) is the oil saturation distribution function, which includes the oil saturation of the experimental core before CO2 injection and the oil saturation of the experimental core before and after CO2 injection.

[0130] The advantage of this setting is that in the CO2 flooding experiment, the third recovery factor can be calculated by obtaining and analyzing the initial oil content information of the experimental core and the oil content information before CO2 injection. This process helps to comprehensively evaluate the recovery of the reservoir and provide a basis for optimizing the flooding strategy.

[0131] The embodiment of the present application provides a method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive, which improves the recovery rate and storage rate by injecting fracturing fluid into the outlet end, accelerating the injection of CO2 into the inlet end, and injecting the fracturing fluid and CO2 from different ends to better fit the characteristics of low porosity and low permeability of the experimental core.

[0132] Figure 3A schematic flow chart of another method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in an embodiment of the present application. Figure 3 As shown, the execution subject of the method can be a server or other servers, and this embodiment is not particularly limited here. Figure 3 As shown, the method includes:

[0133] S301, obtaining experimental materials of reservoir characteristics of the target block, wherein the experimental materials include shale / tight oil reservoir core, simulated formation water, fracturing fluid, experimental crude oil, and simulated formation water configured according to reservoir fluid characteristic parameters.

[0134] Among them, the target area reservoir is the research block reservoir.

[0135] The method for obtaining experimental materials of reservoir characteristics in the target block is as follows:

[0136] (1) Obtain cores, cut and wash the cores, dry and weigh them, and measure the porosity and permeability of the cores. According to the porosity and permeability, determine that the cores are shale / tight oil reservoir cores.

[0137] (2) Prepare formation water and fracturing fluid according to the reservoir fluid characteristic parameters in the study area.

[0138] (3) Using a vacuum test device, the experimental core is vacuumed to obtain a dry core.

[0139] S302, measuring and obtaining the dry core CT value, the experimental crude oil CT value, the oil-saturated core CT value, and the formation water CT value, and obtaining the signal value of the initial oil-saturated core using a nuclear magnetic resonance experimental device.

[0140] The method for obtaining the CT value of oil-saturated core is:

[0141] The experimental crude oil is used to displace the saturated shale / tight core. After the outlet end is stably discharged, the saturation process is completed, and the CT value of the core saturation section is obtained as the CT value of the saturated oil core. The signal value of the initial saturated oil of the core is obtained using a nuclear magnetic resonance experimental device.

[0142] The dry core CT value, experimental crude oil CT value, oil-saturated core CT value, and formation water CT value are measured, and the signal value of the initial saturated oil in the core is obtained by using the nuclear magnetic resonance experimental device:

[0143] (1) Connect the CT scanning experimental device instruments and pipelines according to the experimental device diagram and check the airtightness of the experimental device. Figure 4 This is a schematic diagram of the structure of the experimental device provided in the embodiment of the present application. Figure 4As shown: 1 is a constant speed and constant pressure pump, 5 is a CO2 intermediate container, 6 is a fracturing fluid intermediate container control valve, 7 is a crude oil intermediate container, 12 is a core holder for placing cores, 13 is a confining pressure pump, 14 is a back pressure liquid, 15 is a back pressure pump, 17 is a CT information collector, 18 is a back pressure valve, 19 is a gas-liquid separator, 20 is a gas flow meter, 2, 3, 4, 5, 8, 9, 10, 11, 16 are experimental device instrument control valves.

[0144] (2) placing the core into the core holder of the CT scanning device, and measuring the CT value of the crude oil, the CT value of the simulated formation, the CT value of the formation water, and the CT value of the fracturing fluid under the experimental temperature and pressure, wherein the fracturing fluid is prepared according to the formation water, wherein the experimental temperature refers to the temperature of the reservoir in the study block, and the experimental pressure refers to the pressure of the reservoir in the study block.

[0145] (3) According to the formation pressure in the study area, the experimental core was saturated using the displacement method to obtain the CT value of the saturated oil core.

[0146] (4) Turn on the nuclear magnetic resonance experimental device, set relevant parameters, scan the core saturated core, and obtain the initial nuclear magnetic resonance curve of the oil saturated core.

[0147] S303. Experimental conditions are set according to the on-site pressure-drive construction parameters of shale / tight oil reservoirs to simulate the reverse pressure-drive (fracture fluid) injection process. After the experimental conditions are met, experimental well-insulation simulation is performed at the reservoir temperature and pressure of the study block according to the well-insulation time, and the CT value of the core after well-insulation is measured.

[0148] Among them, the experimental conditions refer to: the temperature and pressure of the reservoir in the study area.

[0149] The experimental conditions were set according to the on-site pressure drive construction parameters of shale / tight oil reservoirs to simulate the reverse pressure drive (fracturing fluid) injection process. After reaching the experimental conditions, the high temperature and high pressure soaking well imbibition simulation was started. The method for measuring the CT value of the core after soaking well imbibition was as follows:

[0150] (1) Place the core after NMR scanning into the CT scanning experimental device, open valve 13, and adjust the pressure to the experimental pressure.

[0151] (2) The prepared fracturing fluid is placed in the intermediate container 2, and the fracturing fluid is injected into the core production end using a constant speed and pressure pump to simulate the reverse pressure drive process.

[0152] (3) Based on the principle of similarity criterion, the displacement of the fracturing fluid injected by reverse pressure drive at the outlet is determined:

[0153]

[0154] Among them, v labIt refers to converting the displacement on site into the displacement for indoor experiments. It generally refers to the displacement of fracturing fluid injected in indoor experiments. field is the displacement of on-site construction, B p is the area of ​​a single hole in the reverse pressure drive on site, N p The number of holes drilled on site.

[0155] (4) Determine the indoor experimental core soaking time tlab.

[0156]

[0157] Among them, t lab refers to the experimental core soaking time, C is the core property parameter, that is, the Young's modulus of the experimental rock sample, μ m is the viscosity of the fluid used in the experimental core, i.e., the viscosity of the fracturing fluid, r is the core radius, Q lab is the experimental core flow rate, that is, the speed of the fluid (the fluid is the fracturing fluid) passing through a certain section of the core, cosθ is the contact angle after the experiment, that is, the contact angle between the experimental crude oil and the experimental core surface, t field This is the time for the well to be stewed on site.

[0158] (5) The core after pressure drive at the production end was scanned using an online CT scanning experimental device to obtain the reverse imbibition distance of the fracturing fluid under pressure drive, the CT value of the core after well soaking and imbibition, and the recovery factor.

[0159] S304. According to the conventional CO2 flooding injection parameters of the shale / tight oil reservoir on site, the variable-stage CO2 injection amount and injection rate are designed to simulate the variable-stage CO2 flooding process. When the saturation of each cross section of the core remains unchanged, the CO2 displacement experiment is terminated, and the CT value and nuclear magnetic resonance signal value of the core after the variable-stage CO2 flooding are measured.

[0160] According to the conventional CO2 flooding injection parameters of shale / tight oil reservoirs on site, the variable-stage CO2 injection amount and injection rate are designed to simulate the variable-stage CO2 flooding process. When the saturation of each cross section of the core remains unchanged, the CO2 displacement experiment is ended, and the CT value and NMR signal value of the core after variable-stage CO2 flooding are measured as follows:

[0161] (1) Determine the indoor core displacement rate and total injection volume. According to the field CO2 flooding field injection volume parameters, combined with the oil field field control range, oil field porosity, experimental core radius, experimental core length, and experimental core porosity, determine the injection volume of the variable stage CO2 injection reverse pressure drive.

[0162] (2) Based on the linear velocity principle, the on-site CO2 injection rate is converted into the indoor core injection rate. Combining the CO2 flooding mechanism with the heterogeneity of the reservoir, the injection rate is reduced in the early stage so that CO2 can enter all parts of the reservoir more evenly, promoting the miscibility of CO2 and crude oil.

[0163] (3) Gradually increase the injection rate in the medium term. After CO2 begins to be distributed more evenly, increase the injection rate appropriately to push more crude oil to the production end and prevent CO2 from being retained.

[0164] (4) In the later stage of pressure drive, increase the injection rate. In the later stage, the remaining oil is often distributed in the low permeability area. At this time, a higher driving force is required to push this part of the remaining oil to the production end.

[0165] (5) After the pressure drive at the production end is completed, valves 3, 8, and 9 are closed, and valves 2 and 10 are opened to conduct a variable-stage CO2 injection experiment. During the experiment, the recovery factor, pressure, and fluid production characteristics are comprehensively considered to determine the recovery factor at different injection rates.

[0166] (6) After the CO2 flooding experiment, the 17 information acquisition instrument was turned on, and the saturation of the core cross section under different PV (Pore Volume) during the CO2 flooding process was obtained through an online CT scanning experiment to determine the evolution law of the imbibition distance and saturation. Figure 5 A schematic diagram of the evolution law of the imbibition distance and saturation provided in this application, such as Figure 5 As shown in the figure, the horizontal axis represents the imbibition distance, the vertical axis represents the water saturation, and the time of 1h, 3h, etc. in the upper right corner represents the imbibition time (i.e., the experimental core soaking time). The experimental core soaking time here is based on the field soaking time t field Get, different on-site well soaking time t field Corresponding to different experimental core soaking times, the 1.25 cm indicated by the arrow represents the reverse imbibition distance of the fracturing fluid under pressure drive.

[0167] (7) Turn off the confining pressure pump, unload the pressure of the constant pressure and constant speed pump to atmospheric pressure, take out the experimental core for nuclear magnetic resonance scanning, obtain the nuclear magnetic resonance curve of the core after CO2 injection, and determine the recovery factor and pore utilization law. The pore utilization law refers to the process and law of the gradual utilization and replacement of the pore space in the reservoir by fluids such as oil, gas, and water during the development of oil and gas fields.

[0168] S305. Based on the experimental data, combined with the nuclear magnetic resonance and CT scanning experimental equipment, the fracturing fluid well recovery rate before and after the variable-stage CO2 injection enhanced reverse pressure drive, the fracturing fluid well reverse imbibition distance and saturation distribution law, the CO2 oil recovery efficiency and the recovery rate before and after the variable-stage CO2 injection pressure drive.

[0169] The CT experimental device was used to measure the CT values ​​of different sections at different injection rates during the CO2 flooding experiment, and the saturation change law and recovery factor of each section at different injection rates were determined.

[0170] (1) According to the CT values ​​before and after the experiment, the water saturation at the production end is calculated, and the evolution law diagram of the imbibition distance and saturation is obtained according to the water saturation (the evolution law diagram of the imbibition distance and saturation is shown in Figure 2). Figure 5 As shown in Figure 2), the reverse imbibition distance of the reverse pressure-driven fracturing fluid is obtained ( Figure 5 The 1.25 cm indicated by the arrow in the figure is the reverse imbibition distance of the reverse pressure-driven fracturing fluid), and the calculation formula is as follows:

[0171]

[0172] Among them, CT dry is the CT value of dry core, CT rock is the CT value of rock particles, CT imbibition is the CT value of the core after soaking and imbibition, CT air is the CT value of air, that is, the CT value of carbon dioxide, CT oil is the CT value of the experimental crude oil, CT water .

[0173] CT saturated =(1-φ)CT rock +φCT oil ,

[0174] Among them, CT rock is the CT value of rock particles, CT saturated is, φ is the core porosity.

[0175] CT oil It is the CT value of the oil-saturated core after reverse pressure drive (fracturing fluid).

[0176] (2) Based on the changes in the signal values ​​of the nuclear magnetic resonance curves before and after the variable-stage CO2 injection pressure drive, and the recovery rate after the variable-stage CO2 injection pressure drive, the variable-stage CO2 reverse pressure drive recovery rate and pore utilization law are calculated.

[0177]

[0178] Among them, R1 is the recovery factor after variable stage CO2 injection and pressure driving, A1 is the initial nuclear magnetic resonance curve area of ​​the core (that is, the nuclear magnetic resonance curve area obtained after the experimental crude oil displaces the saturated shale / tight core), and A2 is the nuclear magnetic resonance curve area after variable stage CO2 injection and pressure driving.

[0179] Figure 6 A schematic diagram of the recovery rate and pore utilization law of a variable-stage CO2 reverse pressure drive provided in an embodiment of the present application is shown in FIG. Figure 6 As shown, the abscissa represents the relaxation time, the ordinate represents the signal intensity, and different curves represent CO2 injected with different PV (Pore volume).

[0180] (3) According to the change of CT value during the variable-stage CO2 injection process, the recovery factor at different stages of CO2 flooding is calculated.

[0181]

[0182] Where: R on Characterizes the recovery factor after the variable-stage CO2 injection process and the recovery factor before the variable-stage CO2 injection process, V im is the displacement volume, V o is the initial oil-containing volume, S oi is the initial oil-bearing volume of the experimental core, x max is the core length, S o (x) is the oil saturation distribution function, including the oil saturation before CO2 injection in the core transformation stage and the oil saturation before CO2 injection in the experimental core. o (x) is the oil saturation of the core before CO2 injection, then R on Characterizes the recovery rate before CO2 injection. o (x) is the oil saturation after CO2 injection in the core transformation stage, then R on Characterize the recovery factor after variable-stage CO2 injection process.

[0183] (4) Calculate the pressure-driven recovery factor based on the changes in imbibition volume and saturation before and after reverse pressure-driven operation at the outlet.

[0184]

[0185] Among them, R o is the recovery factor before core soaking and imbibition, X f is the reverse imbibition distance of the fracturing fluid, S winj is the water saturation at the inlet, x max is the core length.

[0186] S206. According to the experiment of reverse pressure drive enhanced by variable-stage injection of CO2, the CO2 storage rate after reverse pressure drive by variable-stage injection of CO2 is determined by measuring the injection volume under the same temperature and pressure conditions.

[0187] By experimentally measuring the CO2 injection volume under the injection end temperature and pressure conditions, and the CO2 production volume (VR) under the outlet temperature and pressure, and combining the gas state equation with the CO2 storage rate calculation formula, the CO2 storage rate calculation formula that takes into account the influence of the gas deviation factor is obtained.

[0188]

[0189] Among them, V IE is the volume of CO2 injected under injection conditions, cm3 , that is, the volume of CO2 injected through the injection end under the conditions of formation temperature and formation pressure; P E is the injection pressure, MPa, i.e., the formation pressure; Z E is the CO2 deviation factor at injection temperature and pressure, that is, the CO2 deviation factor at formation temperature and formation pressure; Z O is the CO2 deviation factor at the outlet temperature and pressure, that is, the CO2 deviation factor at atmospheric pressure and room temperature (25°C); P O is the outlet pressure, i.e. atmospheric pressure, MPa; V R is the volume of CO2 released under outlet conditions, cm 3 , that is, the volume of CO2 released at the outlet under atmospheric pressure and room temperature.

[0190] Another method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in an embodiment of the present application can fully utilize the crude oil in shale / tight oil reservoir formations and combine variable-stage CO2 injection to enhance reverse pressure drive, thereby improving the storage rate and recovery rate.

[0191] Figure 7 This is a structural example diagram of a device for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in an embodiment of the present application. Figure 7 As shown, the device 70 for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive includes: a first obtaining unit 701, a processing unit 702, a second obtaining unit 703, and a determining unit 704. Among them:

[0192] The first obtaining unit 701 is used to scan and process the experimental core injected with crude oil to obtain a first nuclear magnetic resonance curve, and inject a preset volume of fracturing fluid into the experimental core from a preset first port; wherein the experimental core is located in a preset container, and a preset first port and a preset second port are provided on the preset container, and the first nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core;

[0193] The processing unit 702 is used to perform soaking treatment on the experimental core in the preset container based on the preset environmental conditions;

[0194] The second obtaining unit 703 is used to inject CO2 into the experimental core from a preset second port based on the preset CO2 injection stage configuration information to obtain a second nuclear magnetic resonance curve; wherein the second nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core;

[0195] The determination unit 704 is used to determine the recovery rate of the experimental core according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, and to determine the burial rate of the experimental core according to the volume of injected CO2; wherein the recovery rate represents the ratio of the amount of oil obtained from the experimental core to the total amount of oil in the experimental core, and the burial rate represents the ratio of CO2 sealed in the core.

[0196] Figure 8 This is a structural example diagram of a device for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in an embodiment of the present application. Figure 8 As shown, the device 80 for improving the recovery rate and storage rate of variable stage injection of CO2 and reverse pressure drive includes: a first obtaining unit 801, a processing unit 802, a second obtaining unit 803, and a determining unit 804. The second obtaining unit 803 includes a first obtaining module 8031 ​​and an acquisition module 8032, and the determining unit 804 includes a determining module 8041 and a second obtaining module 8042, wherein:

[0197] In one example, the second obtaining unit 803 includes:

[0198] The first obtaining module 8031 ​​is used to inject CO2 into the experimental core from the preset second port according to the initial velocity and the velocity change rate to obtain the saturation of the experimental core; wherein the saturation represents the distribution of CO2 in the experimental core;

[0199] The acquisition module 8032 is used to acquire the second nuclear magnetic resonance curve at the current moment if the saturation of the experimental core does not change within a preset time period.

[0200] In a possible implementation, the first obtaining module 8031 ​​is specifically used to:

[0201] According to the initial velocity, CO2 is injected into the experimental core from the preset second port;

[0202] If it is determined that the injection time reaches a preset time threshold, CO2 is injected into the experimental core from a preset second port according to the velocity change rate, and the saturation of the experimental core is obtained in real time.

[0203] In one example, the determining unit 804 includes:

[0204] A first determination module 8041 is used to determine the area difference between the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve;

[0205] Obtaining module 8042 is used to obtain the first recovery factor of the experimental core according to the area difference and the curve area of ​​the second nuclear magnetic resonance curve; wherein the first recovery factor represents the recovery factor of the experimental core after CO2 is injected.

[0206] In one example, the determining unit 804 is further configured to:

[0207] Obtaining the imbibition distance, core length, initial water saturation of the core, and water saturation of the preset second port of the experimental core after well soaking treatment; wherein the imbibition distance represents the distance of the fracturing fluid imbibing in the experimental core;

[0208] The second recovery factor of the experimental core is determined according to the imbibition distance, the core length, the initial water saturation of the core, and the water saturation of the second port; wherein the second recovery factor represents the recovery factor of the experimental core after the fracturing fluid is injected.

[0209] In one example, the determining unit 804 is further configured to:

[0210] Determining the volume of CO2 released from the preset first port;

[0211] The burial rate of the experimental core is determined based on the volume of CO2 injected and the volume of CO2 released.

[0212] In one example, the determining unit 804 is further configured to:

[0213] Obtain the initial oil content information of the experimental core and the oil content information of the experimental core before CO2 injection; the oil content information represents the oil saturation of the experimental core;

[0214] According to the initial oil content information of the experimental core and the oil content information of the experimental core before CO2 injection, the third recovery factor of the experimental core is obtained; wherein the third recovery factor represents the recovery factor of the experimental core before the CO2 injection process.

[0215] Fig. 9 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. Fig. 9 As shown, the electronic device 90 includes:

[0216] The electronic device 90 may include a processor 901 with one or more processing cores, a memory 902 with one or more computer-readable storage media, a communication component 903 and other components. The processor 901 , the memory 902 and the communication component 903 are connected via a bus 904 .

[0217] In the specific implementation process, at least one processor 901 executes the computer execution instructions stored in the memory 902, so that at least one processor 901 performs the above-mentioned method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive.

[0218] The specific implementation process of the processor 901 can be found in the above method embodiment, and its implementation principle and technical effect are similar, so this embodiment will not be repeated here.

[0219] In the above Fig. 9 In the illustrated embodiment, it should be understood that the processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), etc. A general-purpose processor may be a microprocessor or any conventional processor. The steps of the method disclosed in the invention may be directly implemented as being executed by a hardware processor, or may be executed by a combination of hardware and software modules in the processor.

[0220] The memory may include a high-speed memory (Random Access Memory, RAM), and may also include a non-volatile memory (Non-volatile Memory, NVM), such as at least one disk memory.

[0221] The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus in the drawings of the present application is not limited to only one bus or one type of bus.

[0222] In some embodiments, a computer program product is also proposed, including a computer program or instructions, which, when executed by a processor, implement the steps in any of the above-mentioned methods for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive.

[0223] The specific implementation of the above operations can be found in the previous embodiments, which will not be described in detail here.

[0224] A person of ordinary skill in the art will appreciate that all or part of the steps in the various methods of the above embodiments may be completed by instructions, or by controlling related hardware through instructions. The instructions may be stored in a computer-readable storage medium and loaded and executed by a processor.

[0225] To this end, an embodiment of the present application provides a computer-readable storage medium, which stores multiple instructions that can be loaded by a processor to execute the steps in any method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in the embodiment of the present application.

[0226] The storage medium may include: a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0227] According to one aspect of the present application, a computer program product or a computer program is provided. The computer program product or the computer program comprises computer instructions stored in a computer-readable storage medium.

[0228] Since the instructions stored in the storage medium can execute the steps in any of the methods for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in the embodiments of the present application, the beneficial effects that can be achieved by any of the methods for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive provided in the embodiments of the present application can be achieved. For details, please see the previous embodiments and will not be repeated here.

[0229] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0230] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily required by the present application.

[0231] It should be further noted that, although the various steps in the flowchart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowchart may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0232] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A method for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive, characterized in that: The method comprises: The experimental core injected with crude oil is scanned to obtain a first nuclear magnetic resonance curve, and a preset volume of fracturing fluid is injected into the experimental core from a preset first port; wherein the experimental core is located in a preset container, and a preset first port and a preset second port are provided on the preset container, and the first nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core; Based on preset environmental conditions, performing soaking treatment on the experimental core in the preset container; Based on the preset CO2 injection phase configuration information, CO2 is injected into the experimental core from a preset second port to obtain a second nuclear magnetic resonance curve; wherein the second nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core; The recovery rate of the experimental core is determined based on the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, and the burial rate of the experimental core is determined based on the volume of injected CO2; wherein the recovery rate represents the ratio of the amount of oil obtained from the experimental core to the total amount of oil in the experimental core, and the burial rate represents the ratio of CO2 sealed in the core.

2. The method according to claim 1, characterized in that The preset CO2 injection phase configuration information includes an initial velocity and a velocity change rate of injecting CO2. Based on the preset CO2 injection phase configuration information, injecting CO2 into the experimental core from a preset second port to obtain a second nuclear magnetic resonance curve includes: According to the initial velocity and the velocity change rate, injecting CO2 into the experimental core from a preset second port to obtain the saturation of the experimental core; wherein the saturation represents the distribution of CO2 in the experimental core; If the saturation of the experimental core does not change within a preset time period, a second nuclear magnetic resonance curve at the current moment is obtained.

3. The method according to claim 2, characterized in that The velocity change rate represents the increase in the velocity of injecting CO2; injecting CO2 into the experimental core from a preset second port according to the initial velocity and the velocity change rate to obtain the saturation of the experimental core, including: Injecting CO2 into the experimental core from a preset second port according to the initial velocity; If it is determined that the injection time reaches a preset time threshold, CO2 is injected into the experimental core from a preset second port according to the velocity change rate, and the saturation of the experimental core is obtained in real time.

4. The method according to claim 1, characterized in that: Determining the recovery factor of the experimental core according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve comprises: determining an area difference between a curve area of ​​the first nuclear magnetic resonance curve and a curve area of ​​the second nuclear magnetic resonance curve; The first recovery factor of the experimental core is obtained according to the area difference and the curve area of ​​the second nuclear magnetic resonance curve; wherein the first recovery factor represents the recovery factor of the experimental core after CO2 is injected.

5. The method according to claim 1, characterized in that: Also includes: Obtaining the imbibition distance, core length, initial water saturation of the core, and water saturation of the preset second port of the experimental core after soaking treatment; wherein the imbibition distance represents the distance of the fracturing fluid imbibing in the experimental core; The second recovery factor of the experimental core is determined according to the imbibition distance, the core length, the initial water saturation of the core, and the water saturation of the second port; wherein the second recovery factor represents the recovery factor of the experimental core after the fracturing fluid is injected.

6. The method according to claim 1, characterized in that Determining the burial rate of the experimental core according to the volume of injected CO2 includes: Determining the volume of CO2 released from the preset first port; The burial rate of the experimental core is determined based on the volume of CO2 injected and the volume of CO2 released.

7. The method according to claim 1, characterized in that Also includes: Obtaining initial oil content information of the experimental core and oil content information of the experimental core before CO2 injection; The oil content information represents the oil saturation of the experimental core; According to the initial oil content information of the experimental core and the oil content information of the experimental core before CO2 injection, the third recovery factor of the experimental core is obtained; wherein the third recovery factor represents the recovery factor of the experimental core before the CO2 injection process.

8. A device for improving the recovery rate and storage rate of variable-stage CO2 injection and reverse pressure drive, characterized in that: include: A first obtaining unit is used to scan and process the experimental core injected with crude oil to obtain a first nuclear magnetic resonance curve, and inject a preset volume of fracturing fluid into the experimental core from a preset first port; wherein the experimental core is located in a preset container, and a preset first port and a preset second port are provided on the preset container, and the first nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core; A processing unit, used for performing soaking treatment on the experimental core in the preset container based on preset environmental conditions; A second obtaining unit is used to inject CO2 into the experimental core from a preset second port based on preset CO2 injection phase configuration information to obtain a second nuclear magnetic resonance curve; wherein the second nuclear magnetic resonance curve represents the relationship between the relaxation time and the signal intensity detected from the radio frequency signal of the experimental core; A determination unit is used to determine the recovery rate of the experimental core according to the curve area of ​​the first nuclear magnetic resonance curve and the curve area of ​​the second nuclear magnetic resonance curve, and to determine the burial rate of the experimental core according to the volume of injected CO2; wherein the recovery rate represents the ratio of the amount of oil obtained from the experimental core to the total amount of oil in the experimental core, and the burial rate represents the ratio of CO2 sealed in the core.

9. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 7 when executed by a processor.

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