Building method for rebuilding underground gas storage from exhausted oil reservoir

Abstract

The invention discloses a reservoir building method for rebuilding an underground gas storage from a depleted oil reservoir, and relates to the technical field of oil reservoir type gas storage. A first number of injection and production wells are arranged at the high position of an oil layer of the depleted oil reservoir, and all perforations of all oil layers through which underground pipe columns of the injection and production wells pass are communicated; a second number of producing wells are arranged at the lower part of the oil layer above the oil-water interface of the oil reservoir; a third number of optimized old producing wells are arranged at the low position of the oil layer of the oil reservoir; and natural gas is injected into the oil reservoir through the injection-production well, an artificial gas cap is formed at the top of the oil reservoir oil layer, and the oil production well conducts crude oil production along with bottom layer energy recovery. Through improvements in the aspects of an innovative database building method, an optimized mining strategy, cost reduction, safety improvement, monitoring capacity enhancement and the like, the crude oil yield can be greatly increased, the recovery rate of remaining oil can be increased, and the space vacated by crude oil extraction can store natural gas, so that the effects of seasonal peak regulation and strategic reserve are achieved; the obvious beneficial effects are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of oil reservoir type gas storage, and more specifically, to a method for constructing an underground gas storage by converting a depleted oil reservoir into an underground gas storage. Background Art

[0002] At present, depleted oil and gas reservoirs account for an absolute proportion of the world's underground natural gas storage. The traditional method of building a gas storage reservoir for oil and gas reservoirs is to deploy a certain number of injection and production wells in the high part of the gas layer of the oil and gas reservoir for gas injection and production, and at the same time deploy certain monitoring wells to monitor relevant underground parameters. For example, the Chinese patent application with publication number CN111155989A can use the dynamic data of injection and production wells to calculate the cumulative gas injection volume and cumulative gas production corresponding to different times; calculate the area or radius of the reservoir drying range when the injection and production wells have different injection and production volumes.

[0003] After the oil reservoir blocks have been through primary oil recovery (using the energy of the oil layer itself to extract oil) or secondary oil recovery (injecting water and gas into the oil layer to replenish energy for oil recovery) or tertiary oil recovery (using chemicals to improve the properties of oil, gas, water and rocks), there is still about 50%-70% of the remaining crude oil that is difficult to extract, and the blocks are almost exhausted and cannot function. From a large number of oil reservoir blocks, blocks with large reservoir space and good sealing are selected to be converted into gas storage. As natural gas is gradually injected, the pressure of the oil reservoir blocks increases, the formation energy is restored, and the oil wells deployed in the oil layer are likely to resume self-flowing production, which can greatly increase crude oil production and the recovery rate of remaining oil. The space freed up by the extraction of crude oil can also be used to store natural gas, thereby playing a role in seasonal peak regulation and strategic reserve, and the waste blocks are finally turned into treasures.

[0004] The traditional technology for converting depleted oil and gas reservoirs into underground gas storage only deploys injection and production wells and monitoring wells, and does not convert gas storage in depleted oil reservoir blocks, which will have the following shortcomings:

[0005] Insufficient utilization of remaining oil resources in depleted reservoirs: Despite the use of primary, secondary and even tertiary oil recovery technologies, about 50%-70% of the remaining crude oil is still difficult to recover. This means that existing oil recovery technologies are unable to fully recover the resources in the reservoirs, resulting in a large amount of crude oil being left underground and unable to be effectively utilized.

[0006] Limited site selection: In the process of renovating a gas storage facility, if only oil and gas reservoir blocks with large reservoir space and good sealing are selected, while some potential high-quality oil reservoir blocks are excluded, this will limit the construction scale and site selection of the gas storage facility.

[0007] Technical limitations: The traditional method of building gas storage in oil and gas reservoirs mainly relies on deploying injection and production wells and monitoring wells in the high gas layers of oil and gas reservoirs. However, this method may not fully utilize the gas storage and oil production potential of depleted oil reservoir blocks. Summary of the invention

[0008] In order to solve the above-mentioned technical problems existing in the prior art, the present invention provides a method for constructing an underground gas storage reservoir by converting a depleted oil reservoir into a gas storage reservoir. A certain number of injection and production wells (new wells) are deployed in the high part of the oil layer of the oil reservoir to play the basic functions of gas injection and gas production peak regulation. At the same time, a certain number of oil production wells (new wells) are deployed in the low part of the oil layer above the oil-water interface of the oil reservoir to continue to produce crude oil. In order to reduce the initial investment in the construction of the reservoir, the old oil production wells in the low part of the oil layer above the oil-water interface can also be used as oil production wells to continue to produce crude oil. Natural gas from the pipeline network is injected into the high part of the oil layer through the injection and production wells. With the gradual injection of natural gas, an effective artificial gas cap is formed at the top of the oil layer. Driven by the high pressure of natural gas, the oil production wells in the low part of the oil layer gradually restore the self-flowing production capacity, the remaining crude oil is continuously produced, and the storage space of natural gas is gradually expanded. Thereby, the dual effects of rebuilding the gas storage reservoir and improving the crude oil recovery rate are achieved.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A method for constructing an underground gas storage reservoir by converting a depleted oil reservoir into an underground gas storage reservoir has the following steps:

[0011] S1. A first number of injection and production wells (new wells) are arranged at the high oil layer of the depleted oil reservoir, and all the oil layers through which the downhole tubing of the injection and production wells pass are perforated and connected;

[0012] S2. A second number of oil production wells (new wells) are arranged at the lower part of the oil layer above the oil-water interface of the oil reservoir;

[0013] S3. Injecting natural gas into the oil reservoir using the injection and production wells. As the natural gas is gradually injected, the pressure of the oil reservoir block increases and the formation energy is restored, so that the oil production wells can be used to produce crude oil.

[0014] Furthermore, a second number of oil production wells (new wells) are arranged in the lower part of the oil layer above the oil-water interface of the oil reservoir; a third number of old oil production wells are arranged in the lower part of the oil layer of the oil reservoir;

[0015] A third number of the oil production wells are arranged at the lower part of the oil layer of the oil reservoir, wherein the third number is less than or equal to the second number.

[0016] Furthermore, the method further includes the following steps: as the natural gas is gradually injected, the natural gas pressure gradually increases, and an artificial gas cap is formed at the top of the oil layer in the oil reservoir. Driven by the high-pressure natural gas at the artificial gas cap, the oil wells at the lower part of the oil layer resume self-flowing production, the remaining crude oil is continuously produced, and the storage space for natural gas is gradually expanded.

[0017] Furthermore, the method includes the following steps: when the volume ratio of gas to liquid in the crude oil production product is within the range of 500:1 to 1500:1 for the first time, the oil well is temporarily shut down, during which the natural gas flows upward and the crude oil flows downward due to the difference in oil and gas density.

[0018] Furthermore, the method further comprises:

[0019] After the shut-in treatment lasts for a second time, reopening the oil production well to restart the crude oil production at the oil production well;

[0020] If the volume ratio of gas to liquid in the produced product of the crude oil production is less than 500:1, the oil production well continues the crude oil production until the volume ratio of gas to liquid in the produced product is again within the range of 500:1 to 1500:1 for the first time, and the shut-in treatment operation and the resumption of crude oil production operation are repeated;

[0021] When the number of the shut-in treatment operation and / or the crude oil recovery operation exceeds a preset number threshold, the oil production well is finally shut-in treated.

[0022] Furthermore, after the injection-production well and the oil production well are finally shut in, the method further includes: changing the oil production well into the injection-production well.

[0023] Furthermore, the wellbore structure and cementing quality of the oil production well meet the maximum design pressure of the gas storage reservoir;

[0024] Changing the oil production well to the injection production well comprises the following steps: replacing the oil production tree of the oil production well with the injection production tree of the injection production well.

[0025] Furthermore, the method further comprises:

[0026] Using a gas injection simulation experiment, the original old oil production wells in the oil reservoir are tested to obtain the operating condition test results of the original old oil production wells;

[0027] Based on the operating condition test results, the available old oil production wells are determined.

[0028] Furthermore, the gas injection simulation experiment is used to test the original old oil wells in the oil reservoir, including the following steps:

[0029] During the gas injection simulation experiment, different gas injection speeds are set to obtain multiple operating condition test results;

[0030] A weighted average is performed on the multiple operating condition test results to obtain a final test result.

[0031] Furthermore, the method further comprises:

[0032] Obtaining the location of the available old oil production well in the oil reservoir;

[0033] The available old oil production well located at a designated position in the oil reservoir is determined as a monitoring well, wherein the designated position includes a fault position, an oil layer position and a saddle position.

[0034] Furthermore, before injecting natural gas into the oil reservoir using the injection and production well, the method further includes: plugging and scrapping the original old oil production wells that are unusable.

[0035] Beneficial effects of the present invention:

[0036] Compared with the existing gas storage construction technology, the construction method of the depleted oil reservoir to rebuild the underground gas storage described in the present invention has the following technical characteristics or beneficial effects:

[0037] Improve resource utilization: This invention uses the remaining oil resources in the depleted oil reservoirs and combines them with natural gas injection technology to achieve further exploitation of crude oil, significantly improving resource utilization. This helps solve the problem of difficulty in extracting remaining oil in traditional oil production technology and turns waste blocks into treasures.

[0038] Innovative storage construction method: This invention proposes a new storage construction method for converting depleted oil reservoirs into underground gas storage reservoirs. By setting injection and production wells in the high part of the oil layer and oil production wells in the low part of the oil layer, and forming an effective artificial gas cap with the injection of natural gas, the dual utilization of the oil reservoir is achieved - both the remaining oil is exploited and the gas storage reservoir is rebuilt. This method is innovative and provides a new idea for the reuse of depleted oil reservoirs.

[0039] Optimizing production strategy: The present invention optimizes the production strategy by monitoring the volume ratio of gas to liquid in the produced material and performing temporary well shut-in treatment and resuming crude oil production operations accordingly. This helps to reduce the waste of natural gas, improve production efficiency, and ensure the long-term stable operation of the oil well.

[0040] Reduce costs: In the process of rebuilding the gas storage, the present invention makes full use of the original old oil production wells, determines their availability through gas injection simulation experiments, and then blocks and scraps them or converts them into monitoring wells accordingly. This reduces the drilling cost of new monitoring wells and reduces the overall cost of rebuilding the gas storage.

[0041] Improve the safety of gas storage: The present invention imposes strict requirements on the wellbore structure and cementing quality of the oil production well to ensure that it meets the maximum design pressure of the gas storage. This helps to improve the safety of the gas storage and reduce the risk of geological disasters.

[0042] Enhanced monitoring capability: The present invention identifies some of the available old oil production wells as monitoring wells, and pays special attention to key locations such as fault locations, oil layer locations, and saddle locations. This enhances the monitoring capability of the gas storage facility and helps to timely discover and respond to potential risks.

[0043] In summary, the present invention provides a new solution for the reuse of depleted oil reservoirs and the construction of underground gas storage through innovative reservoir construction methods, optimized production strategies, reduced costs, improved safety and enhanced monitoring capabilities, and has significant beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below in combination with the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0045] Figure 1 It is a schematic diagram of the deployment of injection and production wells and oil production wells in the reconstruction of depleted oil reservoirs into gas storage facilities. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Figure 1 The method for constructing an underground gas storage facility for converting a depleted oil reservoir into an underground gas storage facility is further explained, and the technical solutions in the embodiments of the present application are clearly and completely described; obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application without making creative work are within the scope of protection of the present application.

[0047] Example 1

[0048] The present invention solves the dual effects of increasing storage capacity and improving recovery rate by reconstructing a depleted oil reservoir into a gas storage reservoir, and provides a method for constructing an underground gas storage reservoir by reconstructing a depleted oil reservoir. The technical solution adopted is:

[0049] 1. A certain number of injection and production wells (new wells) are deployed in the high oil layer of the reservoir to play the basic functions of gas injection and gas production peak regulation. All oil layers passed by the downhole tubing of the injection and production wells are perforated to connect all oil layers.

[0050] 2. At the same time, a certain number of oil production wells (new wells) are deployed in the lower part of the oil layer above the oil-water interface of the reservoir to produce crude oil. In order to reduce the initial investment in building a reservoir, old oil production wells in the lower part of the oil layer above the oil-water interface can also be selected for oil production.

[0051] 3. Transform other usable old oil wells into monitoring wells, and seal and scrap unusable old oil wells.

[0052] 4. The wellbore structure and cementing quality of new injection and production wells and new oil production wells must meet the relevant requirements such as the maximum design pressure of the gas storage reservoir.

[0053] 5. With the gradual injection of natural gas, an artificial gas cap is formed at the top of the oil layer. As the pressure of injected natural gas continues to increase, driven by the high pressure of natural gas, the injection front edge quickly pushes outward, the oil wells in the lower part of the oil layer gradually restore their self-flowing production capacity, the remaining crude oil is produced, and the storage space of natural gas is gradually expanded.

[0054] 6. When gas channeling occurs in the oil well, and the volume ratio of gas to liquid in the produced product is within the range of 500:1 to 1500:1, the oil well is temporarily shut down. During the temporary shut-in period, due to the difference in oil and gas density, natural gas flows upward and crude oil flows downward, and the oil well is reopened for production. If the volume ratio of gas to liquid in the produced product is within the range of 500:1 to 1500:1, the oil well is temporarily shut down for a period of time. This process continues 3 to 5 times.

[0055] 7. When the last oil well has actual gas breakthrough and crude oil cannot be produced normally, these new oil wells will be converted into injection and production wells after evaluation and demonstration, and they will continue to play the role of gas injection and production, thus enhancing the seasonal peak-shaving capacity of natural gas.

[0056] This will achieve the dual effects of rebuilding the gas storage facility and increasing crude oil recovery.

[0057] A certain number of injection and production wells (new wells) are deployed in the high oil layer of the reservoir to play the basic functions of gas injection and gas production peak regulation. All oil layers passed by the downhole pipe string of the injection and production wells are perforated to connect all oil layers. At the same time, a certain number of production wells (new wells) are deployed in the low oil layer above the oil-water interface of the reservoir to produce crude oil. In order to reduce the initial investment in the construction of the reservoir, the old production wells in the low oil layer above the oil-water interface can also be selected as production wells.

[0058] 1. With the gradual injection of natural gas, the natural gas pressure continues to increase, forming an effective artificial gas cap on the top of the oil layer.

[0059] 2. Driven by the high pressure of natural gas, the gas injection front is rapidly pushed outward, the oil wells in the lower part of the oil layer gradually restore their self-flowing production capacity, the remaining crude oil is continuously produced, and the natural gas storage space is gradually expanded.

[0060] 3. When it is confirmed that actual gas breakthrough occurs in the final oil production wells (new wells), these new oil production wells will be converted into injection and production wells to continue to play the role of gas injection and production, thereby enhancing the seasonal peak-shaving capacity of natural gas.

[0061] This achieves the dual effects of converting depleted oil reservoirs into gas storage facilities and increasing crude oil recovery rates.

[0062] Example 2

[0063] This embodiment provides a method for constructing an underground gas storage reservoir by converting a depleted oil reservoir into an underground gas storage reservoir, and the steps are as follows:

[0064] 1. A certain number of injection and production wells 5 (new wells) are deployed at the high position of the oil layer 2 of the oil reservoir, and all the oil layers through which the downhole pipes of the injection and production wells pass are perforated to connect all the oil layers.

[0065] 2. At the same time, a certain number of oil production wells 6 (new wells) are deployed in the lower part of the oil layer above the oil-water interface 4 of the oil reservoir to produce crude oil. In order to reduce the initial investment in building a reservoir, old oil production wells in the lower part of the oil layer above the oil-water interface can also be selected as oil production wells.

[0066] 3. Transform other usable old oil wells into monitoring wells, and seal and scrap the unusable old gas wells and old oil wells.

[0067] 4. With the gradual injection of natural gas, the natural gas pressure continues to rise, forming an artificial gas cap at the top of the oil layer. Driven by the high pressure of natural gas, the gas injection front quickly pushes outward, the oil wells in the lower part of the oil layer gradually restore their self-flowing production capacity, the remaining crude oil is continuously produced, and the storage space of natural gas is gradually expanded.

[0068] 5. When gas breakthrough occurs in the oil well, the well is temporarily shut down for a period of time, and the natural gas in the reservoir moves upward and the crude oil moves downward. Then the well is reopened for production. The well is opened and shut down for 3 to 5 rounds to allow more crude oil to be produced.

[0069] 6. After the last oil well has actual gas breakthrough, these new oil wells will be converted into injection and production wells after evaluation and demonstration, and they will continue to play the role of gas injection and production, thus enhancing the seasonal peak-shaving capacity of natural gas.

[0070] Example 3

[0071] This embodiment combines the attached Figure 1 Describing an embodiment:

[0072] exist Figure 1 A certain number of injection and production wells 5 (new wells) are deployed in the high part of the oil layer 2 of the middle oil reservoir to play the basic functions of gas injection and gas production peak regulation. All the oil layers passed by the downhole pipe strings of the injection and production wells are perforated to connect all the oil layers.

[0073] In the figure, a certain number of oil production wells 6 (new wells) are deployed in the lower part of the oil layer above the oil-water interface 4 of the oil reservoir for crude oil production. In order to reduce the initial investment in reservoir construction, old oil production wells in the lower part of the oil layer above the oil-water interface can also be selected as oil production wells.

[0074] The wellbore structure and cementing quality of new injection and production wells and new oil production wells must meet relevant requirements such as the maximum design pressure of the gas storage reservoir.

[0075] Other usable old oil wells will be transformed into monitoring wells, and unusable old oil wells will be sealed and scrapped.

[0076] As natural gas is injected and formation pressure increases, an artificial gas cap is formed at the top of the oil layer. Driven by the high pressure of natural gas, the injection front quickly pushes outward, the oil wells in the lower part of the oil layer gradually restore their self-flowing production capacity, the remaining crude oil is continuously produced, and the storage space of natural gas is gradually expanded.

[0077] When gas channeling occurs in an oil well and the volume ratio of gas to liquid in the produced material is within the range of 500:1 to 1500:1, the oil well is temporarily shut down. During the temporary shut-in period, due to the difference in oil and gas density, natural gas flows upward and crude oil flows downward, and the oil well is reopened for production. If the volume ratio of gas to liquid in the produced material is within the range of 500:1 to 1500:1, the oil well is temporarily shut down for a period of time. This process is repeated 3 to 5 times to allow more crude oil to be produced.

[0078] When the last oil well has actual gas breakthrough and crude oil cannot be produced normally, these new oil wells will be converted into injection and production wells after evaluation and demonstration, and they will continue to play the role of gas injection and production, thereby enhancing the seasonal peak-shaving capacity of natural gas.

[0079] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for constructing an underground gas storage facility from a depleted oil reservoir, characterized in that: Here are the steps: S1. A first number of injection and production wells are arranged at the high oil layer of the depleted oil reservoir, and all the oil layers passed by the downhole tubing of the injection and production wells are connected by perforations; S2. A second number of oil production wells are arranged at the lower part of the oil layer above the oil-water interface of the oil reservoir; S3. Injecting natural gas into the oil reservoir using the injection and production wells. As the natural gas is gradually injected, the pressure of the oil reservoir block increases and the formation energy is restored, so that the oil production wells can be used to produce crude oil.

2. The method for constructing an underground gas storage reservoir from a depleted oil reservoir as claimed in claim 1, characterized in that: A second number of oil production wells are arranged at the lower part of the oil layer above the oil-water interface of the oil reservoir; a third number of old oil production wells are arranged at the lower part of the oil layer of the oil reservoir; A third number of the oil production wells are arranged at the lower part of the oil layer of the oil reservoir, wherein the third number is less than or equal to the second number.

3. The method for constructing an underground gas storage reservoir from a depleted oil reservoir as claimed in claim 1, characterized in that: The following steps are also included: As natural gas is gradually injected, the natural gas pressure gradually increases, forming an artificial gas cap on the top of the oil layer in the oil reservoir.

4. The method for constructing an underground gas storage reservoir from a depleted oil reservoir as claimed in claim 1, characterized in that: The following steps are also included: When the volume ratio of gas to liquid in the produced material of crude oil extraction is within the range of 500:1 to 1500:1 for the first time, the oil well is temporarily shut in. During the period of temporary shut-in, natural gas flows upward and crude oil flows downward due to the difference in oil and gas density.

5. The method for constructing an underground gas storage reservoir from a depleted oil reservoir as claimed in claim 4, characterized in that: The method further comprises: After the shut-in treatment lasts for a second time, reopening the oil production well to restart the crude oil production at the oil production well; If the volume ratio of gas to liquid in the produced product of the crude oil production is less than 500:1, the oil production well continues the crude oil production until the volume ratio of gas to liquid in the produced product is again within the range of 500:1 to 1500:1 for the first time, and the shut-in treatment operation and the resumption of crude oil production operation are repeated; When the number of the shut-in treatment operation and / or the crude oil recovery operation exceeds a preset number threshold, the oil production well is finally shut-in treated.

6. The method for constructing an underground gas storage reservoir from a depleted oil reservoir as claimed in claim 5, characterized in that: After the injection-production well and the oil production well are finally shut in, the method further includes: changing the oil production well into the injection-production well.

7. The method for constructing an underground gas storage facility from a depleted oil reservoir as claimed in claim 6, characterized in that: The wellbore structure and cementing quality of the oil production well meet the maximum design pressure of the gas storage reservoir; Changing the oil production well to the injection production well comprises the following steps: replacing the oil production tree of the oil production well with the injection production tree of the injection production well.

8. The method for constructing an underground gas storage facility from a depleted oil reservoir according to any one of claims 1 to 7, characterized in that: The method further comprises: Using a gas injection simulation experiment, the original old oil production wells in the oil reservoir are tested to obtain the operating condition test results of the original old oil production wells; Based on the operating condition test results, the available old oil production wells are determined.

9. The method for constructing an underground gas storage reservoir from a depleted oil reservoir as claimed in claim 8, characterized in that: The gas injection simulation experiment is used to test the original old oil production wells in the oil reservoir, including the following steps: During the gas injection simulation experiment, different gas injection speeds are set to obtain multiple operating condition test results; A weighted average is performed on the multiple operating condition test results to obtain a final test result.

10. The method for constructing an underground gas storage reservoir from a depleted oil reservoir as claimed in claim 7, characterized in that: The method further comprises: Obtaining the location of the available old oil production well in the oil reservoir; The available old oil production well located at a designated position in the oil reservoir is determined as a monitoring well, wherein the designated position includes a fault position, an oil layer position and a saddle position.

11. The method for constructing an underground gas storage facility from a depleted oil reservoir as claimed in claim 8, characterized in that: Before injecting natural gas into the oil reservoir using the injection and production well, the method further comprises: plugging and scrapping the original old oil production wells that are unusable.

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