Method for improving recovery ratio through multi-stage diffusion CO2 huff and puff based on variable gas injection speed

Abstract

The invention provides a method for improving the recovery ratio through multi-stage diffusion CO2 huff and puff based on variable gas injection speed. The method comprises the steps that a target injection speed set for CO2 injection of a target well is obtained, wherein the target injection speed set comprises a plurality of gas injection speeds; according to the target injection speed set, CO2 is injected into the core of the target well at the variable gas injection speed; performing soaking treatment on the rock core; and oil recovery of the core of the target well is carried out after soaking treatment. According to the method, CO2 is injected into the core of the target well at the variable gas injection speed through the target injection speed set, and the recovery efficiency can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas reservoir development, and in particular to a method for improving oil recovery rate based on multi-stage pressure-expanding CO2 throughput with variable gas injection rate. Background Art

[0002] As an unconventional oil reservoir, shale oil reservoirs are rich in resources, but their development faces many challenges. The low porosity, low permeability and strong heterogeneity of shale oil reservoirs make it difficult for traditional development technologies to achieve efficient exploitation. Although hydraulic fracturing technology has been widely used in the development of shale oil reservoirs, as the development progresses, problems such as the rapid decline in single well production and high development costs have gradually emerged.

[0003] Due to the complex geological characteristics of shale oil reservoirs, traditional mining methods face many challenges in actual operations, resulting in low recovery rates. Summary of the invention

[0004] The present application provides a method for improving oil recovery by multi-stage pressure-expanding CO2 throughput based on variable gas injection rate, so as to improve the oil recovery rate of oil reservoirs.

[0005] In a first aspect, the present application provides a method for improving oil recovery by multi-stage pressure-expanding CO2 huff-and-puff based on variable gas injection rate, comprising:

[0006] Obtain a target injection rate set for injecting CO2 into a target well, wherein the target injection rate set includes multiple gas injection rates;

[0007] According to the target injection rate set, CO2 is injected into the core of the target well with a variable gas injection rate;

[0008] Carry out well soaking treatment on the core;

[0009] Oil recovery from the core of the target well is performed after the soaking treatment.

[0010] Among them, in this application, the target injection speed set is obtained by the following method:

[0011] Obtaining an experimental core of a target well; wherein the experimental core is saturated with formation crude oil;

[0012] Determine a target injection rate interval, wherein when CO2 is injected at an injection rate in the target injection rate interval, the recovery factor is a value that satisfies the condition, and the recovery factor represents the ratio of the amount of oil extracted from the core to the original total amount of oil in the core;

[0013] Select any number of values ​​in the target injection speed range as the target injection speed set for this round.

[0014] Among them, in this application, determining the target injection speed range includes:

[0015] Determine multiple candidate CO2 injection rates;

[0016] According to each selected CO2 injection rate, a first preset volume of CO2 is uniformly injected into the experimental core;

[0017] The experimental cores of each candidate CO2 injection rate are soaked to obtain the recovery factor of each candidate CO2 injection rate;

[0018] The target injection rate range is determined according to the recovery factors of each candidate CO2 injection rate and the candidate CO2 injection rate corresponding to the recovery factors of each candidate CO2 injection rate.

[0019] Among them, in this application, according to the recovery factor of each candidate CO2 injection rate, and the candidate CO2 injection rate corresponding to the recovery factor of each candidate CO2 injection rate, includes:

[0020] The recovery factor of each candidate CO2 injection rate is used as the ordinate, and the candidate CO2 injection rate corresponding to the recovery factor of each candidate CO2 injection rate is used as the abscissa to obtain a curve graph;

[0021] Determine the recovery factor with the largest value on the vertical axis of the curve graph as the target recovery factor; wherein the target recovery factor includes multiple recovery factors;

[0022] Determine a candidate CO2 injection rate corresponding to a target recovery factor as a target candidate CO2 injection rate; wherein the target candidate CO2 injection rate CO2 injection rate includes a plurality of candidate CO2 injection rates;

[0023] According to the target candidate CO2 injection rate, a target injection rate range is obtained.

[0024] Among them, in this application, according to the target injection rate set, CO2 is injected into the core of the target well with a variable gas injection rate, including:

[0025] Sorting the speeds in the target injection speed set according to a preset order to obtain an ordered target injection speed set; wherein the preset order may be one of an order from small to large and an order from large to small;

[0026] According to the ordered target injection rate set, the preset volume of CO2 for this round is injected into the experimental core.

[0027] Among them, in this application, according to the target injection rate set, CO2 is injected into the core of the target well with a variable gas injection rate, including:

[0028] Obtaining a second preset volume of CO2 injected in each round;

[0029] Add the second preset volumes of each round to obtain the injection volume;

[0030] Obtaining a total volume; wherein the total volume represents the total volume of CO2 to be injected;

[0031] If the injected volume is less than the total volume, the step of injecting CO2 at a variable gas injection rate into the core of the target well according to the target injection rate set is performed until the injected volume is equal to the total volume.

[0032] Among them, in the present application, after the oil recovery of the core of the target well after the well soaking treatment, the method further comprises:

[0033] Obtain the total oil volume produced from the core and the initial total oil volume of the core;

[0034] The total oil volume produced from the core is divided by the initial total oil volume of the core to obtain the recovery factor after this round of soaking treatment.

[0035] In a second aspect, the present application provides a multi-stage pressure-expanding CO2 huff-and-puff enhanced oil recovery device based on variable gas injection rate, comprising:

[0036] An acquisition module is used to acquire a target injection rate set for injecting CO2 into a target well, wherein the target injection rate set includes multiple gas injection rates;

[0037] The injection module is used to inject CO2 with a variable gas injection rate into the core of the target well according to the target injection rate set;

[0038] Well soaking treatment module, used for well soaking treatment of cores;

[0039] The recovery module is used to recover oil from the core of the target well after the soaking treatment.

[0040] In a third aspect, the present application provides an electronic device, comprising: a processor, and a memory communicatively connected to the processor;

[0041] Memory stores computer-executable instructions;

[0042] The processor executes the computer-executable instructions stored in the memory to implement the method in the present application.

[0043] 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.

[0044] 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.

[0045] The present application provides a method, device, equipment and storage medium for improving oil recovery by multi-stage expansion CO2 throughput based on variable gas injection rate. The method comprises obtaining a target injection rate set for injecting CO2 into a target well, wherein the target injection rate set includes multiple injection rates. The target injection rate set can be used to confirm a reasonable variable gas injection rate of CO2, and according to the target injection rate set, CO2 with a variable gas injection rate is injected into the core of the target well. By injecting CO2 into the core of the target well at a variable speed according to the target injection rate set, the contact area between CO2 and the core of the target well can be effectively increased, thereby improving oil recovery. The core is subjected to well soaking treatment. After the well soaking treatment, oil is recovered from the core of the target well. The effect of improving oil recovery is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] 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.

[0047] Figure 1 A schematic flow chart of a multi-stage pressure-expanding CO2 huff-and-puff method for improving oil recovery based on variable gas injection rate provided in an embodiment of the present application;

[0048] Figure 2 A graph provided for an embodiment of the present application;

[0049] Figure 3 Graph B provided for the embodiment of the present application;

[0050] Figure 4 A schematic diagram of a multi-stage expansion CO2 throughput experimental device with variable gas injection rate provided in an embodiment of the present application;

[0051] Figure 5 A schematic flow chart of another method for improving oil recovery by multi-stage pressure-expanding CO2 huff-and-puff based on variable gas injection rate provided in an embodiment of the present application;

[0052] Figure 6 A schematic diagram of the structure of a multi-stage pressure-expanding CO2 huff-and-puff device for improving oil recovery based on variable gas injection rate provided in an embodiment of the present application;

[0053] Figure 7 A schematic diagram of the structure of a multi-stage pressure-expanding CO2 huff-and-puff device for improving oil recovery based on variable gas injection rate provided in an embodiment of the present application;

[0054] Figure 8 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application.

[0055] 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

[0056] 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.

[0057] At present, after the "horizontal well + volume fracturing" is carried out in the shale oil reservoir in the field development practice, a large amount of fracturing fluid enters the micropores of the matrix due to the imbibition effect, thereby blocking the remaining shale oil inside the micropores of the matrix from the flowable fluid in the macropores. This water layer that is imbibed into the micropores not only blocks the entry of fluids in the macropores, but also blocks the discharge of the remaining shale oil therein, which is similar to the role of a "shield". Therefore, this water layer with a double shielding effect that enters the matrix pores under the action of imbibition is called "imbibition water shield". The existence of "imbibition water shield" not only limits the contact between CO2 and crude oil, but also hinders the diffusion of pressure. Due to the low permeability of shale oil reservoirs and the existence of the "dialysis water shield" phenomenon, the diffusion rate of CO2 in the formation is slow, resulting in a limited range of pressure diffusion and the inability to fully cover the entire reservoir. This makes the contact between CO2 and crude oil uneven, especially in horizontal wells, where the contact between CO2 and crude oil in the remote area is insufficient, resulting in unsatisfactory CO2 huff and puff effect to enhance oil recovery.

[0058] The present application provides a method for improving oil recovery by multi-stage pressure-expanded CO2 throughput based on variable gas injection rate. Multi-stage pressure-expanded CO2 throughput refers to a method of adopting a phased injection strategy during the CO2 injection process. Specifically, by setting different gas injection rates during a throughput process, CO2 is gradually injected in stages to optimize the diffusion of CO2 in the reservoir, which can effectively increase the contact area between CO2 and the crude oil of the target well, expand the pressure propagation range, and thus improve CO2 throughput to improve oil recovery.

[0059] Figure 1 A schematic flow chart of a method for improving oil recovery by multi-stage expansion CO2 huff-and-puff based on variable gas injection rate provided in an embodiment of the present application. 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:

[0060] S101, obtaining a target injection rate set for injecting CO2 into a target well, wherein the target injection rate set includes a plurality of gas injection rates.

[0061] The target well is an oil well of an oil reservoir to be studied. The target injection rate set includes multiple different gas injection rates, and the gas injection rate is the rate at which CO2 is injected into the core of the target well. For example, the gas injection rates included in the target injection rate set may be: 0.5 ml / min, 1 ml / min, and 1.5 ml / min.

[0062] Optionally, the multiple injection rates of the target injection rate set are determined by determining the injection rate corresponding to a higher recovery factor among the recovery factors of different injection rates obtained by experimental simulation of the target well, so that when CO2 is injected at the injection rate of the target injection rate set, the recovery factor is greater.

[0063] The number of speeds of the target injection speed concentrated gas injection speed may be any number.

[0064] Generally, for different target wells, their corresponding target injection rate sets are also different. It can be understood that in the target injection rate sets corresponding to different target wells, there are different gas injection rates. In other words, the gas injection rates included in the target injection rate sets corresponding to different target wells may not be completely the same.

[0065] For example, the target injection rate set corresponding to target well a includes injection rates of v1, v2, v3 and v4, among which v1, v2, v3 and v4 are not equal; the target injection rate set corresponding to target well b includes injection rates of v1, v2, v5 and v6, among which v1, v2, v5 and v6 are not equal, and v3, v4, v5 and v6 are not equal.

[0066] For another example, the target injection rate set corresponding to target well a includes injection rates of v1, v2, v3 and v4, among which v1, v2, v3 and v4 are not equal; the target injection rate set corresponding to target well b includes injection rates of v5, v6, v7 and v8, among which v5, v6, v7 and v8 are not equal.

[0067] It should be noted that the above example only takes the target injection rate set containing 4 gas injection rates as an example for illustration, but the embodiments of the present application are not limited to this. The number of gas injection rates included in the target injection rate set is not limited to 4. For example, the number of gas injection rates included in the target injection rate set corresponding to the target well a package is 5, the number of gas injection rates included in the target injection rate set corresponding to the target well b package is 6, and so on.

[0068] S102. Inject CO2 at a variable gas injection rate into the core of the target well according to the target injection rate set.

[0069] In this step, by injecting CO2 into the core of the target well at different gas injection rates included in the target injection rate set, the diffusion of CO2 in the reservoir can be optimized, the contact area between CO2 and the crude oil of the target well can be effectively increased, and the pressure propagation range can be expanded.

[0070] in, Figure 4 A schematic diagram of a multi-stage expansion CO2 throughput experimental device with a variable gas injection rate provided in an embodiment of the present application, in which: 1-an intermediate container filled with crude oil, used to inject the crude oil into the core. Note that CO2 is injected into the core injected with crude oil only after the crude oil is injected into the core, 2-a CO2 intermediate container, filled with CO2, 3, 9-a constant speed and pressure pump, 4, 5, 6-a control valve, used to control the injection of crude oil and CO2, 7-a two-way valve, 8-a pressure monitoring system, used to detect the pressure change at the mouth of the core clamping tube in real time, 10-a core clamp, used to place the core, 2, 11-a back pressure valve, used to release excess pressure, 12-a liquid metering device, used to measure the amount of crude oil extracted from the core, 13-a gas metering system, used to measure the gas coming out of 10, 14-a temperature controller, used to control the temperature when injecting CO2.

[0071] The injection of CO2 with variable gas injection rate refers to injecting CO2 into the core at a variable speed. The target injection rate set includes multiple different gas injections, and CO2 is injected into the core at different speeds in the target injection rate set. For example, the target injection rate set can be: 0.5 ml / min, 1 ml / min, 1.5 ml / min, then CO2 can be injected into the core at a variable speed in the order of 0.5 ml / min→1 ml / min→1.5 ml / min.

[0072] According to the injection speed of the target injection speed concentration, the CO2 with variable gas injection speed is injected into the core of the target well. The injection can be gradually accelerated according to the injection speed of the target injection speed concentration, or the injection can be gradually decelerated according to the injection speed of the target injection speed concentration, as long as the CO2 with variable gas injection speed is injected into the core of the target well according to the injection speed of the target injection speed concentration.

[0073] Optionally, according to the target injection rate set, injecting CO2 with a variable gas injection rate into the core of the target well includes:

[0074] Sorting the speeds in the target injection speed set according to a preset order to obtain an ordered target injection speed set; wherein the preset order may be one of an order from small to large and an order from large to small;

[0075] According to the ordered target injection rate set, the preset volume of CO2 for this round is injected into the experimental core.

[0076] For example, the preset order may refer to injection from small to large, injection from large to small, or injection in any other injection order. For example: when the target injection rate set is 0.25 ml -0.35 ml / min, when the target injection rate set contains 3 rates, the injection may be performed according to the injection rate from small to large, for example: when the ordered target injection rate set is 0.25 ml / min→0.3 ml / min→0.35 ml / min, the injection of CO2 with variable injection rate is performed in the order of 0.25 ml / min→0.3 ml / min→0.35 ml / min. When the ordered target injection rate set is 0.35 ml / min→0.3 ml / min→0.25 ml / min, the injection is performed according to the injection rate from large to small, for example: the injection of CO2 with variable injection rate is performed in the order of 0.35 ml / min→0.3 ml / min→0.25 ml / min. The injection may also be performed in any other injection order. For example, when the target injection rate set is 0.35 ml / min→0.25 ml / min→0.3 ml / min, the injection may be performed in the order of 0.35 ml / min→0.25 ml / min→0.3 ml / min.

[0077] For example: when the target injection rate set contains 4 rates, the injection can be performed according to the injection rate from small to large. For example: when the ordered target injection rate set is 0.2 ml / min→0.25 ml / min→0.3 ml / min→0.35 ml / min, the injection of CO2 with variable injection rate is performed in the order of 0.2 ml / min→0.25 ml / min→0.3 ml / min→0.35 ml / min. When the ordered target injection rate set is 0.35 ml / min→0.3 ml / min→0.25 ml / min→0.2 ml / min, the injection can be performed according to the injection rate from large to small. For example: the injection of CO2 with variable injection rate is performed in the order of 0.35 ml / min→0.3 ml / min→0.25 ml / min→0.2 ml / min. The injection may also be performed in any other injection order. For example, when the target injection rate set is 0.35 ml / min→0.3 ml / min→0.2 ml / min→0.25 ml / min, the injection is performed in the order of 0.35 ml / min→0.3 ml / min→0.2 ml / min→0.25 ml / min.

[0078] The advantage of this setting is that through fine control and optimization of the injection speed, the scientificity and practicality of the experiment can be significantly improved, providing a more effective technical means for research in related fields.

[0079] S103, performing well soaking treatment on the core.

[0080] Well soaking is a technology used in the development of oil and gas fields, mainly used to improve oil and gas recovery. After CO2 is injected, the activity of the well is temporarily stopped, allowing the fluid in the well to naturally balance and react in a static state for a period of time.

[0081] After CO2 is injected into the core, the core is subjected to well soaking treatment.

[0082] S104, recovering oil from the core of the target well after the well soaking treatment.

[0083] Among them, after the well soaking treatment, the total amount of oil produced from the core of the target well can be obtained. According to the total amount of oil produced from the core, the recovery rate can be obtained.

[0084] An embodiment of the present application provides a method for improving oil recovery by using multi-stage pressure-expanded CO2 throughput based on variable gas injection rate, which can effectively determine a target injection rate set for injecting CO2 into a target well. The target injection rate set includes multiple gas injection rates. By injecting CO2 with variable gas injection rates into the core of the target well, the corresponding pressures are different at different gas injection rates, thereby achieving improving oil recovery by using multi-stage pressure-expanded CO2 throughput based on variable gas injection rate during oil extraction.

[0085] In the above embodiment of the present application, the target injection speed set is obtained by:

[0086] Obtaining an experimental core of a target well; wherein the experimental core is saturated with formation crude oil;

[0087] Determine a target injection rate interval, wherein when CO2 is injected at an injection rate in the target injection rate interval, the recovery factor is a value that satisfies the condition, and the recovery factor represents the ratio of the amount of oil extracted from the core to the original total amount of oil in the core;

[0088] Select any number of values ​​in the target injection speed range as the target injection speed set for this round.

[0089] The experimental core is obtained from the target well, and can be a shale core, a dense rock core, or any other core.

[0090] The experimental core is saturated with formation crude oil, indicating that the pores in the experimental core are filled with oil.

[0091] The target injection rate interval represents an injection interval. When injection is performed at the injection rate in the target injection rate interval, the recovery rate obtained is relatively high. The target injection rate interval can be obtained by obtaining the experimental injection rate through the actual injection rate on site, and the target injection rate interval can be obtained based on the experimental injection rate. It is also possible to inject CO2 at different injection rates by designing experiments to obtain the recovery rate at each injection rate, and inject CO2 at the injection rate corresponding to the section with the largest recovery rate as the target injection rate interval.

[0092] Each round requires variable speed injection of CO2 into the experimental core, so it is necessary to select several values ​​in the target injection speed range as the target injection speed set for each round. The gas injection speed in the target injection speed set can be any number, for example: 2, 3.

[0093] The core was obtained from the target well of the reservoir, and the permeability and porosity of the core were measured. The core was cleaned and weighed, and the length and diameter of the core were measured. The core was evacuated and pressurized to saturate the formation crude oil. The saturated core was weighed to obtain the experimental core. The target injection rate range corresponding to the experimental core was determined to be 0.5 ml / min-3 ml / min. Three values ​​of 0.5 ml / min, 1 ml / min, and 1.5 ml / min were selected from the target injection rate range to obtain the target injection rate set for this round.

[0094] The advantage of this setting is that the target injection rate set of this round is determined from the target injection rate range corresponding to a higher recovery factor, so that CO2 can be injected into the core at a variable speed according to the target injection rate set, thereby improving the recovery factor.

[0095] As a possible implementation of the present application, determining a target injection speed range includes:

[0096] Determine multiple candidate CO2 injection rates;

[0097] According to each selected CO2 injection rate, a first preset volume of CO2 is uniformly injected into the experimental core;

[0098] The experimental cores of each candidate CO2 injection rate are soaked to obtain the recovery factor of each candidate CO2 injection rate;

[0099] The target injection rate range is determined according to the recovery factors of each candidate CO2 injection rate and the candidate CO2 injection rate corresponding to the recovery factors of each candidate CO2 injection rate.

[0100] The first preset volume can be any volume, which represents the total injection amount of CO2 injected into the core during the experiment.

[0101] The range of gas injection rate can be preliminarily determined based on the core volume. For example, the core volume is approximately 24.5 cm 3 During the injection process, according to the literature, the injection rate will not be particularly large, and it is confirmed that the injection rate is approximately between 0.5-3ml / min. According to the preliminary judgment of the range of the injection rate, the experimental injection rate is set to multiple candidate CO2 injection rates. For example, the injection rate is between 0.5ml / min-3ml / min, and 0.5 ml / min, 1 ml / min, 1.5 ml / min, 2 ml / min, 2.5 ml / min, and 3 ml / min are set as the experimental injection rates, that is, multiple candidate CO2 injection rates. According to each injection rate, 1ml of CO2 is uniformly injected into the experimental core, and then each injection rate group is soaked, and the recovery rate of each injection rate is recorded. According to the size of the recovery rate of each injection rate, the corresponding injection rate is determined, and the target injection rate range is obtained according to the corresponding injection rate.

[0102] The advantage of this setting is that it provides a scientific method to determine the optimal CO2 injection rate range through systematic experiments and analysis, thereby improving the recovery rate.

[0103] On the basis of the above-mentioned embodiment of the present application, according to the recovery factor of each candidate CO2 injection rate and the candidate CO2 injection rate corresponding to the recovery factor of each candidate CO2 injection rate, it can further include:

[0104] The recovery factor of each candidate CO2 injection rate is used as the ordinate, and the candidate CO2 injection rate corresponding to the recovery factor of each candidate CO2 injection rate is used as the abscissa to obtain a curve graph;

[0105] Determine the recovery factor with the largest value on the vertical axis of the curve graph as the target recovery factor; wherein the target recovery factor includes multiple recovery factors;

[0106] Determine a candidate CO2 injection rate corresponding to a target recovery factor as a target candidate CO2 injection rate; wherein the target candidate CO2 injection rate includes a plurality of candidate CO2 injection rates;

[0107] According to the target candidate CO2 injection rate, a target injection rate range is obtained.

[0108] The recovery rate of each candidate CO2 injection rate is used as the ordinate, and the candidate CO2 injection rate corresponding to the recovery rate of each candidate CO2 injection rate is used as the abscissa to obtain a curve graph. The curve represents the degree of recovery (i.e., recovery rate) at different gas injection rates. In one embodiment, the curve graph is a curve graph A. The curve graph A is as shown in FIG. Figure 2As shown in the figure, when the gas injection rate is between 0.2ml / min-0.35ml / min, the corresponding recovery factor (i.e. the corresponding recovery degree) is relatively large. Therefore, the target recovery factor is greater than 80%, the target candidate CO2 injection rate is 0.2 ml / min, 0.25 ml / min, 0.3 ml / min, 0.35ml / min, and the target injection rate range is 0.2ml / min-0.35ml / min.

[0109] In one embodiment, the curve graph is a curve graph B, and the curve graph B is as follows: Figure 3 As shown in the figure, when the gas injection rate is between 0.25ml / min-0.35ml / min, the corresponding recovery factor is relatively large. Therefore, the target recovery factor is greater than 68%, the target CO2 injection rate is 0.2 ml / min, 0.25 ml / min, 0.3 ml / min, 0.35 ml / min, and the target injection rate range is 0.2ml / min-0.35ml / min.

[0110] The advantage of this setting is that the change curve of recovery rate and injection rate can be obtained through the curve graph, and the corresponding CO2 injection rate when the recovery rate is higher can be found accurately and quickly.

[0111] As an example, the injection of CO2 with a variable gas injection rate into the core of the target well according to the target injection rate set may include:

[0112] Obtaining a second preset volume of CO2 injected in each round;

[0113] Add the second preset volumes of each round to obtain the injection volume;

[0114] Obtaining a total volume; wherein the total volume represents the total volume of CO2 to be injected;

[0115] If the injected volume is less than the total volume, the step of injecting CO2 at a variable gas injection rate into the core of the target well according to the target injection rate set is performed until the injected volume is equal to the total volume.

[0116] The second preset volume can be any volume, representing the total amount of CO2 injected into the core in each round. The second preset volume is 0.1 ml, but the second preset volume of each round needs to be consistent. The injection volume is the total volume of the experimental core injected so far in the current round. The total volume represents the total volume of CO2 that needs to be injected, which can be 1 ml, representing the total amount of CO2 injected into the core.

[0117] When the second preset volume is 0.1ml and the total volume is 1ml, the first round: 0.1ml of CO2 is injected into the experimental core at a variable speed, and then the experimental core is soaked to obtain the recovery rate of the first round. The first round: 0.1ml of CO2 is injected into the experimental core at a variable speed, and then the experimental core is soaked to obtain the recovery rate of the first round. At this time, the injection volume of 0.1ml is less than the total volume, so continue to inject 0.1ml of CO2 into the experimental core at a variable speed, and then soak the experimental core to obtain the recovery rate of the second round. Until all 1ml of CO2 is injected into the experimental core.

[0118] The embodiments of the present application provide an effective means to improve the recovery rate and efficiency of CO2 injection into the core, while reducing operational risks, through precise injection control and flexible speed adjustment.

[0119] Further, after oil recovery from the core of the target well after the soaking treatment, the method further comprises:

[0120] Obtain the total oil volume produced from the core and the initial total oil volume of the core;

[0121] The total oil volume produced from the core is divided by the initial total oil volume of the core to obtain the recovery factor after this round of soaking treatment.

[0122] The initial total oil content of the core refers to the original oil content contained in the core before any injection or recovery experiments are carried out.

[0123] The initial total oil volume of the core refers to the original oil volume contained in the core before any injection or recovery experiment is carried out. The total oil volume extracted from the core is divided by the initial total oil volume of the core to obtain the recovery factor after this round of soaking treatment. The recovery factor after the last round of soaking treatment is the final recovery factor.

[0124] A flow chart of another method for improving oil recovery by multi-stage pressure-expanding CO2 huff-and-puff based on variable gas injection rate provided in an embodiment of the present application. Figure 5 As shown, the execution subject of the method can be a server or other servers, and this embodiment is not particularly limited here. Figure 5 As shown, the method includes:

[0125] S501. Core sample preparation.

[0126] (1) Determine the core permeability and porosity, clean the core and weigh it, and measure the core length and diameter.

[0127] (2) The core is vacuumed and pressurized to saturate the formation crude oil. After saturation, the core is weighed.

[0128] (3) Place the core sample in a high-pressure core holder to ensure good sealing and airtightness. The system is connected to a high-pressure CO2 injection device to ensure stable control of temperature, pressure and other conditions during the experiment.

[0129] S502: gas injection velocity interval optimization experiment.

[0130] In order to determine the most suitable injection rate range, multiple groups of CO2 injection rate experiments were first conducted.

[0131] (1) Initial injection rate setting: Select multiple different initial CO2 injection rates and conduct experiments separately to ensure that the injection rate range can cover the injection requirements under different reservoir conditions.

[0132] (2) In each set of experiments, CO2 was slowly injected into the core at a constant injection rate, followed by well soaking, and the pressure changes and crude oil production were recorded.

[0133] (3) By comparing the CO2 core recovery factors under different gas injection rates, the optimal gas injection rate range was determined, which served as a reference for the subsequent variable gas injection rate multi-stage pressure expansion experiment.

[0134] S503, multi-stage pressure expansion experiment with variable gas injection velocity.

[0135] In the optimal gas injection rate range, a multi-stage pressure diffusion experiment with variable gas injection rate was carried out by gradually adjusting the gas injection rate to optimize the diffusion and displacement effect of CO2 in the core.

[0136] (1) Initial gas injection stage: Based on the gas injection rate optimization experiment, the initial gas injection rate is determined, CO2 is slowly injected, and the pressure changes at both ends of the core are recorded.

[0137] (2) Multi-stage pressure expansion gas injection stage: According to the optimal gas injection speed range, the gas injection speed is flexibly adjusted to control the diffusion range of CO2 in the core and improve the sweep efficiency of CO2 inside the core. The core is full of oil. The oil output is different in different stages. In the same stage, the oil output increases, which proves that the diffusion range is larger.

[0138] (3) Dynamically adjust gas injection parameters: According to the monitored CO2 diffusion range, pressure changes at both ends of the core and crude oil production, dynamically adjust the gas injection rate and duration to ensure the best injection effect. Increasing the CO2 injection rate can increase the pressure at both ends of the core.

[0139] (4) Data analysis: Collect data such as pressure changes and produced crude oil volume at each stage, calculate the crude oil recovery factor under multi-stage pressure-expansion gas injection, compare the results with those of conventional constant gas injection rate, and evaluate the improvement effect of the variable gas injection rate multi-stage pressure-expansion method on CO2 throughput development.

[0140] Another multi-stage expansion CO2 throughput method based on variable gas injection rate to improve oil recovery provided by the embodiment of the present application can effectively determine the optimal gas injection rate range in the CO2 throughput development process of shale oil reservoirs, and combined with the multi-stage expansion mode with variable gas injection rate, improve the problem of insufficient contact between CO2 and crude oil due to long well shut-in time in the traditional CO2 throughput process, improve the contact efficiency between CO2 and crude oil in the core, increase the CO2 sweep range, and improve the problem of uneven pressure diffusion. This method not only improves the CO2 throughput to improve oil recovery, but also provides a feasible technical solution for the development of shale oil reservoirs under different complex geological conditions.

[0141] The following is an embodiment of the device of the present application, which can be used to execute the embodiment of the method of the present application. For details not disclosed in the embodiment of the device of the present application, please refer to the embodiment of the method of the present application.

[0142] Figure 6 This is a structural example diagram of a multi-stage pressure-expanding CO2 injection enhancement device based on variable gas injection rate provided in an embodiment of the present application. Figure 6 As shown, the multi-stage expansion CO2 huff-and-puff enhanced oil recovery device 60 based on variable gas injection rate includes: an acquisition module 601, an injection module 602, a well soaking treatment module 603, and a recovery module 604. Among them:

[0143] An acquisition module 601 is used to acquire a target injection rate set for injecting CO2 into a target well, wherein the target injection rate set includes multiple gas injection rates;

[0144] Injection module 602, used to inject CO2 with variable gas injection rate into the core of the target well according to the target injection rate set;

[0145] Well soaking treatment module 603, used for well soaking treatment of cores;

[0146] The recovery module 604 is used to recover oil from the core of the target well after the soaking treatment.

[0147] Figure 7 This is a structural example diagram of a multi-stage pressure-expanding CO2 injection enhancement device based on variable gas injection rate provided in an embodiment of the present application. Figure 7 As shown, the multi-stage expansion CO2 huff-and-puff enhanced oil recovery method based on variable gas injection rate 70 includes: an acquisition module 701, an injection module 702, a well soaking treatment module 703, and a recovery module 704. The acquisition module 701 includes an acquisition unit 7011, a determination unit 7012, and an optional unit 7013, wherein:

[0148] In one example, the acquisition module 701 includes:

[0149] An acquisition unit 7011 is used to acquire an experimental core of a target well; wherein the experimental core is saturated with formation crude oil;

[0150] A determination unit 7012 is used to determine a target injection rate interval, wherein when CO2 is injected at an injection rate in the target injection rate interval, the recovery factor is a value that satisfies the condition, and the recovery factor represents the ratio of the amount of oil extracted from the core to the original total amount of oil in the core;

[0151] The optional unit 7013 is used to select several values ​​in the target injection speed interval as the target injection speed set for this round.

[0152] In a possible implementation, the first obtaining module 7011 is specifically used for:

[0153] Determine multiple candidate CO2 injection rates;

[0154] According to each of the selected CO2 injection rates, a first preset volume of CO2 is uniformly injected into the experimental core;

[0155] The experimental cores of each candidate CO2 injection rate are soaked to obtain the recovery factor of each candidate CO2 injection rate;

[0156] The target injection rate range is determined based on the recovery factors of each candidate CO2 injection rate and the candidate CO2 injection rate corresponding to the recovery factors of each candidate CO2 injection rate.

[0157] In a possible implementation, the first obtaining module 7011 is specifically used for:

[0158] The recovery rate of each candidate CO2 injection rate is used as the ordinate, and the candidate CO2 injection rate corresponding to the recovery rate of each candidate CO2 injection rate is used as the abscissa to obtain a curve graph;

[0159] Determine the recovery factor with the largest value on the vertical axis of the curve graph as the target recovery factor; wherein the target recovery factor includes multiple recovery factors;

[0160] Determine a candidate CO2 injection rate corresponding to a target recovery factor as a target candidate CO2 injection rate; wherein the target candidate CO2 injection rate includes a plurality of candidate CO2 injection rates;

[0161] According to the target candidate CO2 injection rate, a target injection rate range is obtained.

[0162] In a possible implementation, the first obtaining module 7011 is specifically used for:

[0163] Sorting the speeds in the target injection speed set according to a preset order to obtain an ordered target injection speed set; wherein the preset order may be one of an order from small to large and an order from large to small;

[0164] According to the ordered target injection rate set, the preset volume of CO2 for this round is injected into the experimental core.

[0165] In a possible implementation, the first obtaining module 7011 is specifically used for:

[0166] Obtaining a second preset volume of CO2 injected in each round;

[0167] Add the second preset volumes of each round to obtain the injection volume;

[0168] Obtaining a total volume; wherein the total volume represents the total volume of CO2 to be injected;

[0169] If the injected volume is less than the total volume, the step of injecting CO2 at a variable gas injection rate into the core of the target well according to the target injection rate set is performed until the injected volume is equal to the total volume.

[0170] In a possible implementation, the first obtaining module 7011 is specifically used for:

[0171] Obtain the total oil volume produced from the core and the initial total oil volume of the core;

[0172] The total oil volume produced from the core is divided by the initial total oil volume of the core to obtain the recovery factor after this round of soaking treatment.

[0173] The device provided in the embodiment of the present application can execute the technical solution shown in the above method embodiment, and its implementation principle and beneficial effects are similar, which will not be repeated here.

[0174] It should be noted that it should be understood that the division of the various modules of the above device is only a division of logical functions. In actual implementation, they can be fully or partially integrated into one physical entity, or they can be physically separated. And these modules can all be implemented in the form of software called by processing elements; they can also be all implemented in the form of hardware; some modules can also be implemented in the form of software called by processing elements, and some modules can be implemented in the form of hardware. For example, the processing module can be a separately established processing element, or it can be integrated in a chip of the above device. In addition, it can also be stored in the memory of the above device in the form of program code, and called and executed by a processing element of the above device. The implementation of other modules is similar. In addition, these modules can be fully or partially integrated together, or they can be implemented independently. The processing element here can be an integrated circuit with signal processing capabilities. In the implementation process, each step of the above method or each module above can be completed by an integrated logic circuit of hardware in the processor element or instructions in the form of software.

[0175] For example, the above modules may be one or more integrated circuits configured to implement the above methods, such as one or more application specific integrated circuits (ASIC), or one or more microprocessors (DSP), or one or more field programmable gate arrays (FPGA). For another example, when a module above is implemented in the form of a processing element scheduling program code, the processing element may be a general-purpose processor, such as a central processing unit (CPU) or other processor that can call program code. For another example, these modules may be integrated together and implemented in the form of a system-on-a-chip (SOC).

[0176] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loading and executing computer instructions on a computer, a process or function according to an embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from a website site, a computer, a server or a data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (Digital Subscriber Line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or a data center that includes one or more available media integrations. The available media may be magnetic media (eg, floppy disk, hard disk, magnetic tape), optical media (eg, Digital Video Disc (DVD)), or semiconductor media (eg, solid state disk (SSD)).

[0177] Figure 8 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. Figure 8 As shown, the electronic device 80 includes:

[0178] The electronic device 80 may include a processor 801 with one or more processing cores, a memory 802 with one or more computer-readable storage media, a communication component 803 and other components. The processor 801, the memory 802 and the communication component 803 are connected via a bus 808.

[0179] In the specific implementation process, at least one processor 801 executes the computer execution instructions stored in the memory 802, so that at least one processor 801 executes the above-mentioned method for improving oil recovery by multi-stage diffusion CO2 throughput based on variable gas injection rate.

[0180] The specific implementation process of the processor 801 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.

[0181] In the above Figure 8In 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. The general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc. The steps of the method disclosed in the invention may be directly embodied as being executed by a hardware processor, or may be executed by a combination of hardware and software modules in the processor.

[0182] The memory may include a high-speed memory (Random Access Memory, RAM), and may also include a non-volatile memory (NVM), such as at least one disk storage.

[0183] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus in the drawings of this application is not limited to only one bus or one type of bus.

[0184] In some embodiments, a computer program product is also proposed, including a computer program or instructions, which, when executed by a processor, implements the steps in any of the above-mentioned methods for improving oil recovery by multi-stage diffusion CO2 throughput based on variable gas injection rate.

[0185] The specific implementation of the above operations can be found in the previous embodiments, which will not be described in detail here.

[0186] 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.

[0187] To this end, an embodiment of the present application provides a computer-readable storage medium storing a plurality of instructions, which can be loaded by a processor to execute the steps in any one of the methods for improving oil recovery by multi-stage diffusion CO2 throughput based on variable gas injection rate provided in the embodiments of the present application.

[0188] The storage medium may include: a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0189] 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.

[0190] Since the instructions stored in the storage medium can execute the steps of any method for improving oil recovery by using multi-stage pressure-diffusion CO2 throughput based on variable gas injection rate provided in the embodiments of the present application, the beneficial effects that can be achieved by any method for improving oil recovery by using multi-stage pressure-diffusion CO2 throughput based on variable gas injection rate provided in the embodiments of the present application can be achieved. For details, please refer to the previous embodiments and will not be repeated here.

[0191] 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.

[0192] 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 oil recovery by multi-stage expansion CO2 huff-and-puff based on variable gas injection rate, characterized in that: The method comprises: Acquire a target injection rate set for injecting CO2 into a target well, wherein the target injection rate set includes multiple gas injection rates; Injecting CO2 at a variable gas injection rate into the core of the target well according to the target injection rate set; Performing well soaking treatment on the core; After the well soaking treatment, oil recovery is carried out from the core of the target well.

2. The method according to claim 1, characterized in that The target injection rate set is obtained by: Obtaining an experimental core of the target well; wherein the experimental core is saturated with formation crude oil; Determine a target injection rate interval, wherein when CO2 is injected at an injection rate in the target injection rate interval, the recovery factor is a value that satisfies a condition, and the recovery factor represents the ratio of the amount of oil extracted from the core to the original total amount of oil in the core; Several values ​​in the target injection speed interval are selected as the target injection speed set for this round.

3. The method according to claim 2, characterized in that Determining the target injection speed interval includes: Determine multiple candidate CO2 injection rates; According to each CO2 to be selected, a first preset volume of CO2 is uniformly injected into the experimental core; Performing well soaking treatment on the experimental cores at each candidate CO2 injection rate to obtain the recovery factor of each candidate CO2 injection rate; The target injection rate range is determined according to the recovery factors of the candidate CO2 injection rates and the candidate CO2 injection rates corresponding to the recovery factors of the candidate CO2 injection rates.

4. The method according to claim 3, characterized in that The recovery factors according to the CO2 injection rates to be selected, and the CO2 injection rates to be selected corresponding to the recovery factors of the CO2 injection rates to be selected, include: Taking the recovery rate of each selected CO2 injection rate as the ordinate and the selected CO2 injection rate corresponding to each selected recovery rate as the abscissa, a curve graph is obtained; Determine the recovery factor with the largest value on the vertical axis of the curve graph as the target recovery factor; wherein the target recovery factor includes a plurality of the recovery factors; Determine the candidate CO2 injection rate corresponding to the target recovery factor as the target candidate CO2 injection rate; wherein the target candidate CO2 injection rate includes the multiple candidate CO2 injection rates; The target injection rate range is obtained according to the target candidate CO2 injection rate.

5. The method according to any one of claims 1 to 4, characterized in that The step of injecting CO2 with a variable gas injection rate into the core of the target well according to the target injection rate set includes: Sorting the speeds in the target injection speed set according to a preset order to obtain an ordered target injection speed set; wherein the preset order may be one of an order from small to large and an order from large to small; According to the ordered target injection rate set, a preset volume of CO2 is injected into the experimental core.

6. The method according to any one of claims 1 to 4, characterized in that The step of injecting CO2 with a variable gas injection rate into the core of the target well according to the target injection rate set includes: Obtaining a second preset volume of CO2 injected in each round; Add the second preset volumes of each round to obtain the injection volume; Obtaining a total volume; wherein the total volume represents the total volume of CO2 to be injected; If the injection volume is smaller than the total volume, the step of injecting CO2 at a variable gas injection rate into the core of the target well according to the target injection rate set is performed until the injection volume is equal to the total volume.

7. The method according to any one of claims 1 to 4, characterized in that After the oil recovery from the core of the target well after the well soaking treatment, the method further comprises: Obtain the total oil volume produced from the core and the initial total oil volume of the core; The total oil volume produced from the core is divided by the initial total oil volume of the core to obtain the recovery factor after this round of soaking treatment.

8. A multi-stage expansion CO2 huff-and-puff enhanced oil recovery device based on variable gas injection velocity, characterized in that: include: An acquisition module, used to acquire a target injection rate set for injecting CO2 into a target well, wherein the target injection rate set includes a plurality of gas injection rates; An injection module, used for injecting CO2 with a variable gas injection rate into the core of the target well according to the target injection rate set; A well-insertion processing module, used for performing well-insertion processing on the core; The recovery module is used to recover oil from the core of the target well after soaking treatment.

9. An electronic device, characterized in that: include: Processor and memory; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory, so that the electronic device performs the method of 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.

Images