Injection method for controlling gas channeling in carbon dioxide oil displacement process

Abstract

The invention relates to the technical field of oil and gas field development and adjustment, and particularly discloses an injection method for controlling gas channeling in a carbon dioxide oil displacement process, which comprises the following steps of: S1, judging a gas channeling well based on production characteristics of an oil producing well in a target block; s2, determining a dominant direction and a vulnerable direction of gas flooding displacement of the gas injection well in the target block; s3, setting an injection mode according to the dominant direction and the vulnerable direction; and S4, executing the injection mode until the gas channeling well in the target block is converted into a normal well. For the problem that gas channeling is prone to occurring in the mine field carbon dioxide oil displacement process, the injection mode is adjusted according to dynamic data of the mine field, the carbon dioxide flooding dominant direction and the corresponding injection mode are determined based on the actual situation of the mine field, injection is adjusted, and therefore gas channeling is effectively controlled.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development and adjustment technology, specifically to an injection method for controlling gas channeling during carbon dioxide flooding. Background Technology

[0002] To effectively advance the implementation of the "dual carbon" goals, carbon capture, utilization, and storage (CVC) is a key pathway for the clean and low-carbon application of fossil energy, and undoubtedly a practical measure to buy time for large-scale energy conservation, emission reduction, and green and low-carbon transformation. China began exploring carbon dioxide enhanced oil recovery (CEM) technology as early as the 1960s. However, due to limitations in gas sources, mechanisms, and equipment, related experiments essentially ceased in the 1970s, with only some minimum miscibility pressure measurements and mixing mechanism studies conducted indoors. Entering the 21st century, with the discovery of carbon dioxide-bearing natural gas reservoirs in the Songliao Basin, CEM research and experimentation rapidly commenced, significantly accelerating the pace of technological development and application, achieving major breakthroughs in theoretical innovation, technological breakthroughs, and pilot tests.

[0003] Currently, this technology is at a critical stage of transitioning from pilot testing to industrial-scale testing. However, due to the complex geological formations in oil and gas fields, characterized by prominent planar and inter-layer conflicts, gas channeling frequently occurs during carbon dioxide flooding. Gas channeling refers to the sudden increase in gas production in production wells after carbon dioxide is injected into injection wells, reaching a certain limit. This can be identified as gas channeling in conjunction with changes in casing pressure. To address the gas channeling problem during carbon dioxide flooding and ensure field productivity, most fields currently reduce the amount of carbon dioxide injected at the injection end or shut down production wells, resulting in a decrease in the swept volume and oil displacement efficiency of carbon dioxide flooding.

[0004] In conclusion, how to effectively control gas channeling while ensuring oilfield production capacity, thereby increasing the swept volume and oil displacement efficiency of carbon dioxide flooding and improving oil and gas field recovery, has become an urgent problem to be solved. Summary of the Invention

[0005] To address existing technical problems, this invention proposes an injection method for controlling gas channeling during carbon dioxide flooding. This method overcomes the limitations and simplistic approaches currently used in mines to handle the unavoidable gas channeling problem during carbon dioxide flooding. By adjusting the injection method based on dynamic data from the mining area and identifying the advantageous direction and injection method for carbon dioxide flooding based on the actual conditions of the mine, the method aims to increase the swept volume of injected underground carbon dioxide and improve oil recovery efficiency.

[0006] According to one aspect of the present invention, an injection method for controlling gas channeling during carbon dioxide flooding is provided, comprising the following steps: S1. Based on the production characteristics of oil wells in the target block, identify gas channeling wells; S2. Determine the dominant and weak directions of gas drive displacement in the gas injection wells within the target block; S3. Set the injection method according to the advantageous and disadvantageous directions; S4. Execute the injection method until the gas channeling well in the target block is transformed into a normal well.

[0007] According to one embodiment of the present invention, the production characteristics of an oil well include the daily gas production and casing pressure of the oil well.

[0008] According to one embodiment of the present invention, determining gas channeling wells based on the production characteristics of oil wells within a target block includes: Based on the daily gas production and casing pressure of multiple oil wells in the target block area, the criteria for judging gas channeling wells in the target block are determined. Based on the criteria for identifying gas-channeling wells within the target block, gas-channeling wells are determined.

[0009] According to one embodiment of the present invention, the criterion for determining gas channeling wells within the target block is: daily gas production ≥ 2000 m³ / s for 30 consecutive days. 3 The pressure of the casing is ≥10 MPa for 30 consecutive days.

[0010] According to one embodiment of the present invention, determining the dominant and weak directions of gas drive displacement of gas injection wells within a target block includes: determining the dominant and weak directions of gas drive displacement of gas injection wells within the target block based on the time and concentration of the tracer in different directions of the gas injection wells.

[0011] According to one embodiment of the present invention, in step S3, the injection method includes alternating injection and production between multiple rows of wells along the dominant direction using a rotation injection method, wherein a large-segment plug-type water-gas alternating injection is used during the rotation injection process.

[0012] According to one embodiment of the present invention, in step S3, the injection method includes injection and extraction along the dominant direction, and in the alternating injection process, a small-segment plug-type water-gas alternating injection is adopted.

[0013] According to one embodiment of the present invention, in step S3, the injection method includes injection and extraction along the weak direction, and in the alternating injection process, a large-segment plug-type water-gas alternating injection is adopted.

[0014] According to one embodiment of the present invention, in step S3, the injection method includes injection and extraction along the weak direction, and in the alternating injection process, a small-segment plug-type water-gas alternating injection is adopted.

[0015] According to one embodiment of the present invention, step S4 further includes dynamically analyzing the daily gas production and casing pressure of the gas-channeling well until the gas-channeling well in the target block is transformed into a normal well.

[0016] By adopting the above technical solutions, this invention has the following advantages compared with the prior art: Based on the advantages of carbon dioxide flooding and displacement, combined with actual field data and various dynamic and static data, a well / drainage rotation injection combined with water-gas alternating injection method is scientifically and systematically proposed, which further improves the development effect of carbon dioxide flooding, fills the gap in field regulation of carbon dioxide flooding, and to a certain extent solves the problem of insufficient experience in using carbon dioxide as a new high-temperature oil displacement medium, providing a new idea for the subsequent application of carbon dioxide oil displacement in various fields. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some implementation examples of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A process flow diagram of an injection method for controlling gas channeling during carbon dioxide flooding according to an embodiment of the present invention is shown. Figure 2 The oil production curve of well H79-6-6 in the H125 area is shown in the injection method for controlling gas channeling during carbon dioxide flooding according to an embodiment of the present invention. Figure 3 The oil production curves of a large gas well and a gas channeling well are shown in the injection method for controlling gas channeling during carbon dioxide flooding according to an embodiment of the present invention. Figure 4 The inoculation time and concentration of the tracer in a carbon dioxide flooding process for controlling gas channeling are shown according to an embodiment of the present invention. Figure 5 A distribution diagram showing the advantageous orientation of the injection method for controlling gas channeling during carbon dioxide flooding according to an embodiment of the present invention is shown. Figure 6 An injection method for controlling gas channeling during carbon dioxide flooding according to an embodiment of the present invention is shown, which adjusts the oil recovery curve after injection. Detailed Implementation

[0019] The following detailed description of the embodiments is intended to exemplify the principles of the present invention, but should not be construed as limiting the scope of the invention. The present invention can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0020] These embodiments are provided to make this disclosure thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0021] It should be noted that, in the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] It should also be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0023] All terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0024] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0025] This invention provides an injection method for controlling gas channeling during carbon dioxide flooding. Figure 1 A process flow diagram of an exemplary injection method for controlling gas channeling in a carbon dioxide flooding process according to the present invention is shown, which specifically includes the following steps: S1. Based on the production characteristics of oil wells in the target block, identify gas channeling wells; S2. Determine the dominant and weak directions of gas drive displacement in the gas injection wells within the target block; S3. Set the injection method according to the advantageous and disadvantageous directions; S4. Execute the injection method until the gas channeling well in the target block is transformed into a normal well.

[0026] In step S4, after selecting different injection methods, the production dynamics of the CO2 flooding oilfield are tracked throughout the entire process. When a certain injection method is implemented, the field dynamics show a significant decrease in daily gas production, a reduction in casing pressure that remains at a low level, and a certain increase in daily oil production. This corresponds to the optimal well / row rotation injection and the corresponding WAG injection scheme.

[0027] Water-alternating-gas injection (WAG) is a technology for enhancing oil recovery that combines two traditional processes: water drive and gas drive.

[0028] In some embodiments, determining gas-channeling wells based on the production characteristics of oil wells within the target block includes: determining the criteria for judging gas-channeling wells within the target block based on the daily gas production and casing pressure of multiple oil wells in the region where the target block is located; and judging gas-channeling wells based on the criteria for judging gas-channeling wells within the target block.

[0029] In some embodiments, the criterion for determining gas channeling wells within the target block is: daily gas production ≥ 2000 m³ / s for 30 consecutive days. 3 The casing pressure must be ≥10 MPa for 30 consecutive days. In practice, the measurement of the daily gas production continuity can be performed over a longer or shorter period.

[0030] When an oil well is identified as a gas-channeling well or a high-gas-volume well, the injection will be adjusted according to the steps outlined in this application, thereby transforming the gas-channeling well or high-gas-volume well into a normal well. This can greatly reduce the occurrence of gas channeling, making production management simpler and more efficient, thus significantly improving the recovery rate and bringing higher economic benefits to the oilfield.

[0031] Based on the above embodiments, determining the dominant and weak directions of gas drive displacement in gas injection wells within the target block includes: utilizing inter-well tracer monitoring technology to determine the dominant and weak directions of gas drive displacement in gas injection wells within the target block. Specifically, by injecting tracers into gas injection wells, sampling from surrounding monitoring wells, and analyzing the tracer concentration in the samples, the infiltration time and concentration of the tracer in different directions of the gas injection wells are determined. Then, based on the infiltration time and concentration of the tracer in different directions of the gas injection wells, the dominant and weak directions of gas drive displacement in gas injection wells within the target block are determined.

[0032] The initiation time refers to the time interval from when the tracer is injected into the monitoring system to when it is first detected at the monitoring point. The initiation concentration refers to the concentration of the tracer in the monitoring medium (such as water, soil, gas, etc.) when it is first detected at the monitoring point. Determining the dominant and weak directions of gas drive displacement in the target block based on the initiation time and / or concentration of the tracer in different directions of the injection well involves injecting tracers into the injection wells and monitoring their production in production or observation wells to reveal the flow characteristics and distribution patterns of gas in the underground reservoir. The dominant direction indicates the direction in which the tracer flows most smoothly and fastest in the underground reservoir. In the dominant direction, the initiation time is early and the concentration is high. The dominant and weak directions can be determined by initiation time or concentration alone, or by a combination of both.

[0033] By monitoring the arrival time and peak concentration of tracers in different directions, the movement path and velocity of fluids in the reservoir can be intuitively understood. The region where tracers first appear often corresponds to the main flow direction or dominant channel of the fluid, thus providing important information for determining the fluid flow direction in the reservoir.

[0034] In the embodiments of this application, before injection, the dominant direction of gas displacement is determined, and injection is carried out only after the dominant direction is obtained. Alternating water-gas injection creates a three-phase flow of oil, gas, and water in the oil and gas reservoir. By adjusting the injection method and parameters according to the dominant direction of the reservoir, the distribution of fluids in the reservoir can be improved more effectively. This optimization enables the effective extraction of residual oil that was originally difficult to be displaced by water, thereby improving the recovery rate.

[0035] In some embodiments, step S3 involves injection methods including alternating injection along the dominant direction with large-slug WAG injection. This means that multiple rows of wells along the dominant direction are injected and produced alternately using an alternating injection method, with large-slug water-gas alternating injection during the alternating injection process. This alternating water-gas injection method helps prevent water or gas channeling that may occur during single-fluid injection, thereby maintaining reservoir stability and extending well production life. Through alternating injection and large-slug injection, the injection volume of water and gas can be better controlled, improving water injection utilization, reducing ineffective water or gas injection, and lowering production costs. The alternating injection method and large-slug injection allow for flexible adjustments to the injection scheme during development based on actual conditions to adapt to dynamic reservoir changes and ensure maximum development effectiveness.

[0036] In some embodiments, step S3 includes injection via a dominant direction with a small-segment WAG injection, i.e., injection and extraction along the dominant direction, with alternating small-segment water-gas injection during the alternating injection process. Large-segment injection may create a stronger shielding effect, allowing gas to penetrate deeper into the low-permeability layer; while small-segment injection may enhance the sweeping effect through more frequent alternation.

[0037] In some embodiments, step S3 includes injection along the weaker direction with a large-slug WAG injection, i.e., injection and production are carried out along the weaker direction, and large-slug water-gas alternating injection is used during the injection cycle. Injection along the weaker direction helps to balance the pressure field within the reservoir and reduce production fluctuations caused by uneven pressure. This helps to maintain the relative stability of well production and improve the continuity and stability of production.

[0038] In some embodiments, step S3 includes injection along the weaker direction with a small-slug WAG injection, i.e., injection and production are carried out along the weaker direction, and small-slug water-gas alternating injection is used during the alternating injection process. Injection along the weaker direction can improve the fluid flow state within the oil layer, allowing the injected fluid to be more evenly distributed to each oil layer, thereby improving oil displacement efficiency. At the same time, it also helps to reduce production problems caused by poor fluid flow.

[0039] In some embodiments, step S3 further includes inter-well rotation injection with large-slug WAG injection or inter-well rotation injection with small-slug WAG injection, that is, injection and production are carried out between different layers of multiple multi-layered wells. During the rotation injection process, large-slug or small-slug water-gas injection is used alternately. Because the geological characteristics, oil saturation, pressure, etc., of each oil layer differ, stratified injection can be targeted according to the specific needs of each oil layer, thereby ensuring the maximization of injection effect. This method avoids the injection ineffectiveness that may occur in traditional injection methods and improves oil displacement efficiency.

[0040] In some embodiments, step S4, performing the injection method until the gas-channeling well in the target block is transformed into a normal well, also includes dynamically analyzing the daily gas production and casing pressure of the gas-channeling well until it is transformed into a normal well. The presence of gas-channeling wells often leads to unstable fluctuations in oil well production. By dynamically analyzing and taking measures to transform gas-channeling wells into normal wells, such fluctuations can be significantly reduced, maintaining relatively stable oil well production. Gas channeling accelerates oil well wear and shortens its service life. Timely intervention and remediation can protect the integrity of oil wells and extend their production life.

[0041] In some embodiments, step S4, dynamic analysis includes analyzing the dynamic changes in daily gas production and casing pressure. This allows for real-time monitoring of the gas well's production status, timely detection of anomalies during production, such as decreased production or increased casing pressure, and prompt implementation of countermeasures to prevent production losses. Timely dynamic analysis of casing pressure helps protect the reservoir from over-exploitation or pressure fluctuations. Through dynamic analysis of casing pressure, injection methods can be rationally adjusted to ensure sustainable reservoir production.

[0042] By conducting real-time statistical analysis and dynamic monitoring of data from all oil wells within the block, anomalies in the production process can be detected promptly, such as increases or decreases in daily production or abnormal casing pressure. This allows for swift adjustments to ensure stable production. Dynamic analysis provides rich data support, enabling more scientific and rational formulation of block development strategies and providing a basis for adjusting these strategies.

[0043] In some embodiments, obtaining the daily gas production and casing pressure of an oil well also includes plotting oil production curves for the daily gas production and casing pressure. Oil production curves can reflect the real-time changes in the daily gas production and casing pressure of an oil well, facilitating production management personnel to understand production dynamics and grasp the production status in a timely manner. Abnormal fluctuations on the oil production curve may indicate abnormal conditions within the well, such as blockage, leakage, or gas breakthrough. Timely detection and handling of these abnormal conditions can prevent production accidents and ensure production safety. Based on the shape and characteristics of the oil production curve, the type and characteristics of gas wells can be classified, such as normal wells, gas channeling wells, and high-gas wells, providing a basis for targeted adjustments to the injection method.

[0044] Building upon the above embodiments, obtaining the daily gas production and casing pressure of oil wells also includes obtaining the daily gas production and casing pressure of all oil wells within the carbon dioxide flooding block. By periodically collecting the daily gas production and casing pressure data of all oil wells, real-time monitoring of oil and gas production within the block can be achieved, allowing for timely understanding of production dynamics. By comparing the production data of different oil wells, wells with excessive gas flow, normal wells, and wells with abnormal production or problems can be identified, providing precise location information for production management.

[0045] Determining whether an oil well is a gas-channeling well also involves establishing criteria for gas channeling within the block based on the actual daily gas production and casing pressure, and then determining whether all oil wells within the block are gas-channeling wells. By obtaining gas channeling criteria based on actual daily gas production and casing pressure, it is possible to more accurately identify which oil wells within the block exhibit gas channeling, avoiding the subjectivity and uncertainty of traditional methods. For wells identified as gas-channeling wells, they can be classified and managed according to their degree and characteristics of gas channeling, and targeted adjustments to injection methods can be made to improve management efficiency.

[0046] Building upon the above embodiments, this also includes establishing a mathematical model of dynamic analysis data within the block, and using this model to adjust the oilfield within the block. Through this mathematical model, the production status of each oil well within the block can be accurately analyzed, including key indicators such as daily production, water cut, and casing pressure changes. This data provides a scientific basis for formulating and adjusting injection strategies, helping to achieve precise decision-making and improve extraction efficiency.

[0047] The following explanation, using a specific example of a gas channeling well in the H125 block of an oilfield, further illustrates the method steps of this invention. This oilfield block began carbon dioxide flooding development in August 2020, employing a five-point infill well network and multi-layer development. Due to the complexity of the development layers and prominent inter-layer and planar conflicts, gas channeling occurred in some wells. To address the gas channeling problem, the specific implementation steps include: S1. Obtain daily gas production and casing pressure data from the oil well to determine whether the oil well is a gas channeling well: An oilfield conducted a detailed analysis and summary of all mining areas developed using carbon dioxide flooding, and clarified that the characteristics of gas channeling wells are large continuous daily gas production and high casing pressure. Based on the characteristics of the gas channeling wells mentioned above, production curves including casing pressure and daily gas production were generated for all oil wells in the H125 area, and the specific gas channeling standards for gas channeling wells in this block were summarized.

[0048] like Figure 2 The figure shows the oil production curve of well H79-6-6 in the H125 area.

[0049] A comparison of over 40 wells across the entire block ultimately determined the standard for gas channeling wells in area H125: Generally, if the daily gas production continuously exceeds 2000 m³ / h... 3 If the well is considered to be a high-gas well, and the casing pressure is also as high as 10 MPa, then the well is considered to be a gas-channeling well. Based on the aforementioned criteria for gas channeling wells, Well No. 5 in the H125 area, compared to other oil wells, has a daily gas production consistently exceeding 2000 m³ / s. 3 However, the casing pressure fluctuates around 1.5 MPa, therefore well H125 in the H125 area is determined to be a high-gas well; while well H79-8-6 in the H125 area has a daily gas production exceeding 2000 m³ / h. 3 Furthermore, the casing pressure fluctuates around 10MPa, which is significantly different from other oil wells in the H125 area. Therefore, well H79-8-6 is determined to be a gas channeling well.

[0050] like Figure 3 The figure shows the oil production curves of the large gas well and the gas channeling well in the H125 area. Figure 3 (a) shows the oil production curve of the H125 gas well. Figure 3 (b) shows the oil production curve of the gas channeling well H79-8-6.

[0051] S2. Determine the dominant direction of gas drive displacement based on the data of the gas injection well tracer; Obtain tracer data from all gas injection wells in the H125 area to determine the dominant displacement direction of carbon dioxide flooding. For example... Figure 4 The figure shows the time and concentration of the tracer in different directions in region H125. Figure 4 (a) Effective concentrations of oil produced from wells in different directions within the same well group; Figure 4(b) shows the effective time and peak concentration of oil wells in different directions within the same well group.

[0052] Depend on Figure 4 (a) It can be seen that after injection through the same injection well H+79-2-4, the oil production well H79-2-6, which runs east-west, reaches its target concentration fastest; combined with Figure 4 (b) Well H79-2-6 achieved flux in 38 days after injection, with a peak concentration of approximately 50 mg / L. Both the flux initiation time and concentration significantly exceeded those of other wells in the same well group. Based on the above analysis, the dominant displacement direction of carbon dioxide flooding in the H125 area is determined to be east-west.

[0053] S3. Based on the determined dominant direction, design six injection schemes for inter-row injection and inter-well injection in the dominant and weak directions, and combine them with large / small slug water-gas alternating injection (WAG).

[0054] Based on the dominant displacement direction of carbon dioxide flooding obtained in S2, the following injection methods are designed: First injection method: inter-well rotation injection with large-segment WAG injection in the dominant direction; Second injection method: WAG injection with small-segment WAG injection in the dominant direction; Third injection method: WAG injection with large-segment WAG injection in the weak direction; Fourth injection method: WAG injection with small-segment WAG injection in the weak direction; Fifth injection method: inter-well rotation injection with large-segment WAG injection; Sixth injection method: inter-well rotation injection with small-segment WAG injection.

[0055] like Figure 5 As shown, from August 2021 to May 2023, the H125 area adopted the first injection method, namely the dominant direction inter-row injection with large-segment WAG injection method.

[0056] Specifically, injection wells are deployed along the direction closest to the dominant displacement direction of carbon dioxide flooding. Large-segment WAG injection involves injecting gas into one row of injection wells, while the adjacent row of wells injects water, with a rotation cycle of 30 days. Figure 5 In the process, if the blue well is a water injection well, then the orange well is a gas injection well. After 30 days of injection, the blue well becomes a gas injection well and the orange well becomes a water injection well, and this cycle repeats after 30 days.

[0057] S4. After adjusting the injection method, the entire process is dynamically analyzed to select the optimal well / row injection cycle and the corresponding WAG scheme.

[0058] After selecting the injection method in S3, the production dynamics of the mining area were tracked throughout the entire process, with particular attention paid to changes in daily gas production and casing pressure. Ultimately, the optimal well / row rotation injection and matching WAG injection scheme were selected.

[0059] In the H125 area, the first injection method is applied, which is to inject WAG with large-segment plugs in the advantageous direction, and then focus on the dynamic changes of gas-producing wells and gas-channeling wells.

[0060] like Figure 6 The figure shows the oil production curves of the gas well H125 and the gas channeling well H79-8-6 in the H125 area after applying the first injection method, namely, the dominant direction inter-row injection with large-segment plug WAG injection.

[0061] like Figure 6 As shown in (a), after applying the first injection method, namely, the dominant directional inter-row injection with large-slug WAG injection, the casing pressure of the gas well H125 decreased from approximately 2 MPa to 0.8 MPa, a decrease of 1.2 MPa; the daily gas production increased from a continuous 2000 m³ / day. 3 Descending to 1000m 3 It was transformed from a high-gas well into a normal well.

[0062] like Figure 6 As shown in (b), after applying the first injection method, namely the dominant direction inter-row injection with large-segment plug WAG injection, the casing pressure of the gas-channeling well H79-8-6 decreased from 13MPa to 2.5MPa, a decrease of 80.8%. The daily gas production changed little, but showed a downward trend, requiring a longer evaluation time. Based on the change in casing pressure, well H79-8-6 changed from a gas-channeling well to a large-gas well.

[0063] In Block H125, the first injection method was applied, namely, sequential injection in the dominant direction with large-segment WAG injection. This resulted in the transformation of high-gas wells into normal wells and gas-channeling wells into high-gas wells. The above field practice demonstrates that the gas-channeling control injection method achieved excellent field test results during carbon dioxide flooding. It not only eliminated the previous approach of simply controlling the injection volume of carbon dioxide and shutting down production wells to address gas channeling issues in carbon dioxide flooding operations, but also increased the swept volume of injected underground carbon dioxide, improved oil displacement efficiency, and ultimately enhanced oil recovery.

[0064] Based on the advantageous displacement direction of carbon dioxide flooding, and combined with actual field data and various dynamic and static data, this invention scientifically and systematically proposes a well / drainage rotation injection combined with WAG injection method, which further improves the development effect of carbon dioxide flooding, fills the gap in field regulation of carbon dioxide flooding, and to a certain extent solves the problem of insufficient experience in using carbon dioxide as a new high-temperature oil displacement medium, providing a new approach for the subsequent application of carbon dioxide flooding in various fields.

[0065] Compared with the prior art, the present invention has the following advantages: 1. In response to the unavoidable gas channeling phenomenon during carbon dioxide flooding, compared with the existing methods of simply controlling the amount of carbon dioxide injected into the injection well and shutting down the production well, this invention adjusts the injection method based on dynamic data of the mining area, finds the advantageous direction of carbon dioxide flooding based on the actual situation of the mining area, and proposes a total of 6 injection methods. Finally, the optimal injection method is determined by the dynamic data after adjusting the injection method, so as to effectively control gas channeling.

[0066] 2. Carbon dioxide flooding is a type of gas-driven technology within tertiary oil recovery, and it has rapidly developed as a displacement medium since the "dual carbon" target was proposed. However, our understanding of its oil displacement mechanism and its practical control in oilfield operations is still far from sufficient. This invention innovatively proposes a well / drainage rotation injection combined with WAG injection method based on the advantages of carbon dioxide flooding, which undoubtedly provides a new approach for the control of carbon dioxide flooding oilfields.

[0067] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. An injection method for controlling gas channeling in a carbon dioxide flooding process, characterized by, The method comprises the following steps: S1, determining a gas channeling well based on production characteristics of a production well in a target block; S2, determining a dominant direction and a weak direction of gas displacement by a gas injection well in the target block; S3, setting an injection mode according to the dominant direction and the weak direction; S4, executing the injection mode until the gas channeling well in the target block becomes a normal well.

2. The method of claim 1, wherein the injection is performed in a carbon dioxide flooding process. In step S1, the production characteristics of the production well include daily gas production and casing pressure of the production well.

3. The method of claim 2, wherein the injection is performed in a carbon dioxide flooding process. Determining a gas channeling well based on production characteristics of a production well in a target block comprises: Determining a judgment standard of a gas channeling well in the target block based on daily gas production and casing pressure of a plurality of production wells in a region where the target block is located; Determining a gas channeling well according to the judgment standard of the gas channeling well in the target block.

4. The method of claim 3, wherein the injection is performed in a carbon dioxide flooding process. The judgment standard of the gas channeling well in the target block is that the daily gas production is greater than or equal to 2000 m 3 for 30 days in succession, and the casing pressure is greater than or equal to 10 MPa for 30 days in succession.

5. The method of claim 1, wherein the injection is performed in a carbon dioxide flooding process. The determining of the dominant direction and the weak direction of gas displacement by a gas injection well in the target block comprises: determining the dominant direction and the weak direction of gas displacement by a gas injection well in the target block according to tracer arrival time and tracer concentration in different directions of the gas injection well.

6. The method for injection for controlling gas channeling in a carbon dioxide flooding process according to claim 1, wherein, In step S3, the injection mode comprises alternating injection and production between multiple rows of wells along the dominant direction, and large slug water-gas alternating injection is used in the alternating injection process.

7. The method of claim 1, wherein the injection is performed in a carbon dioxide flooding process. In step S3, the injection mode comprises injection and production along the dominant direction, and small slug water-gas alternating injection is used in the alternating injection process.

8. The method of claim 1, wherein the injection is performed in a carbon dioxide flooding process. In step S3, the injection mode comprises injection and production along the weak direction, and large slug water-gas alternating injection is used in the alternating injection process.

9. The method for injection for controlling gas channeling in a carbon dioxide flooding process as claimed in claim 1, wherein, In step S3, the injection mode comprises injection and production along the weak direction, and small slug water-gas alternating injection is used in the alternating injection process.

10. The method of claim 3, wherein the injection is performed in a carbon dioxide flooding process. In step S4, the execution of the injection mode until the gas channeling well in the target block becomes a normal well further comprises dynamic analysis of daily gas production and casing pressure of the gas channeling well until the gas channeling well in the target block becomes a normal well.

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