Honeycomb salt cavern gas storage and its cavity making and gas injection and production method

Abstract

The application discloses a honeycomb type salt cavern gas storage and a cavity forming and gas injection and production method thereof, comprising a center well field and a satellite well field, characterized in that: the center well field is provided with a center well, the satellite well field is provided with at least three satellite wells, the satellite wells are on the same circumference and surround the center well, a cavity is formed at the bottom of the satellite well and the center well, the bottom of the satellite well is communicated two by two through first horizontal wells to form a communication channel, the center well is communicated with any satellite well through a second horizontal well, and a plurality of inclined wells are further included. Compared with the prior art, the satellite well and the center well form a topological network, and the inclined well system is used to realize multi-cavity linkage. Compared with a four-square distribution, a six-square distribution significantly improves the space utilization rate. For example, when seven salt cavities are constructed, only seven gas injection and production wells and three brine discharge wells are needed, the land range required for wellhead arrangement is small, only one large well field and six small well fields are needed, and the ground land range is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of salt cavern gas storage technology, and in particular to a honeycomb salt cavern gas storage facility and its cavity construction and gas injection and extraction method. Background Technology

[0002] Currently, most domestic salt cavern gas storage facilities adopt single-well single-cavity or double-well single-cavity models. A single gas storage facility requires 3,300 mu of land to build surface storage tanks, while a salt cavern storage facility of the same capacity only requires 400 mu. However, the existing well layout method still has significant drawbacks: on the one hand, the single-well single-cavity model requires separate configuration of injection and production gas wells and brine discharge wells, resulting in a scattered distribution of surface well sites and low integration between mines and the land; on the other hand, the traditional four-sided well layout method has a space utilization rate of less than 40%, and the distance between the caverns in the underground salt layer needs to maintain a safe distance of 2 times the cavity diameter, resulting in about 60% of salt mine resources being unable to be effectively developed.

[0003] Furthermore, in existing technologies, salt cavern creation often employs natural dissolution processes. Although the operation is simple, the shape of the cavity is uncontrollable, easily forming a columnar cavity with a diameter of 70m and a height of 150m. This results in excessive redundancy in the safety distance between adjacent cavities. At the same time, the single-cavity gas injection and extraction process requires an independent brine discharge system, leading to low brine treatment efficiency and making it difficult to achieve multi-cavity linkage peak regulation.

[0004] These technical bottlenecks severely restrict the application of salt cavern gas storage in actual production. Therefore, there is an urgent need for a honeycomb salt cavern gas storage system and its cavity construction and gas injection and extraction methods to solve the above problems. Summary of the Invention

[0005] The main objective of this invention is to provide a honeycomb salt cavern gas storage facility and its cavity construction and gas injection / production method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A honeycomb-type salt cavern gas storage facility includes a central well field and satellite well fields. The central well field has one central well, and the satellite well fields have at least three satellite wells. The satellite wells are arranged on the same circumference and surround the central well. The bottoms of the satellite wells and the central well form cavities. The bottoms of the satellite wells are connected to each other through a first horizontal well to form a connecting channel. The central well is connected to any of the satellite wells through a second horizontal well. The facility also includes several inclined wells, each of which extends to the bottom open-hole section of a non-adjacent satellite well.

[0008] Furthermore, the distance between adjacent satellite wells is ≥250m.

[0009] Furthermore, the horizontal distance between the inclined well trajectory and the central well cavity is ≥50m, and the endpoint is located ≥200m below the top of the satellite well cavity.

[0010] This invention also discloses a cavity-building method for a honeycomb salt cavern gas storage facility, comprising the following steps:

[0011] Step 1: Drill satellite wells to the bottom of the salt layer, and then drill the first horizontal wells so that the satellite wells are connected to each other through the first horizontal wells to form a connecting channel;

[0012] Step 2: Drill a center well and a second horizontal well, and connect the center well to any satellite well through the second horizontal well;

[0013] Step 3: Drill an inclined well, extending it to the bottom of the open hole section of the satellite well vertical shaft, so that the inclined well connects with the first horizontal well;

[0014] Step 4: Simultaneously inject fresh water into the satellite well and the central well, and dynamically adjust the brine discharge rate through the inclined well to control the diameter of the connecting cavity dissolved from the first horizontal well and the second horizontal well to 10-15m.

[0015] Step 5: Based on the central well and satellite wells, water-soluble cavity creation is carried out. Through ultrasonic logging feedback, nitrogen gas anti-dissolution technology is used to regulate cavity growth. The height difference between the satellite well and the central well cavity is ≤20m.

[0016] Furthermore, in step three, when the depth of the inclined well is at a distance from the designed top height of the salt cavity, the inclination is calculated using the following formula:

[0017] When H-x2≤y≤H+H1, the drilling slope formula is:

[0018]

[0019] In the formula: x is the horizontal distance between the pipeline and the wellhead of the inclined shaft; y is the vertical distance between the pipeline and the wellhead of the inclined shaft; H is the distance between the top of the cavity and the wellhead; H1 is the distance between the top of the designed salt cavity and the bottom of the initial solution cavity; x1 is the distance between the wellhead of the inclined shaft and the wellhead of the central well, 10≤x1≤15; x2 is the vertical distance between the starting point and the top of the designed salt cavity, x2≥200; D is the diameter of the designed salt cavity; d is the horizontal distance between the end point of the inclined shaft and the center of the bottom of the initial solution cavity of the central well, 250≤d≤350.

[0020] Furthermore, in step one, an acoustic signal transmitter and receiver are used to directionally control the connection between the first horizontal well and the adjacent satellite well, retaining a 200-250m naked-eye section.

[0021] This invention also discloses a gas injection and extraction method for a honeycomb salt cavern gas storage facility, comprising:

[0022] Gas injection and brine removal stage:

[0023] Step 1: Inject natural gas into the connecting cavity through the central well, and discharge brine through the inclined well;

[0024] Step 2: Based on the difference in cavity burial depth, gas is injected first into the cavity with the deepest burial depth, and then gas is injected into the cavity with the shallowest burial depth.

[0025] Step 3: During the synchronous gas injection process, adjust the gas injection rate of each chamber in real time to ensure that the height difference between the gas and liquid interfaces between the chambers is ≤10m.

[0026] Step 4: When terminating gas injection, ensure that the final gas-liquid interface height is not lower than the safe height threshold of the shallowest cavity.

[0027] Gas extraction stage:

[0028] Step 5: Gas is extracted through the central injection well, and brine is selectively replenished through the inclined well;

[0029] Step 6: Based on the differences in cavity burial depth, gas is first extracted from the cavity with the shallowest burial depth, and then from the cavity with a deeper burial depth.

[0030] Step 7: During the synchronous gas sampling process, adjust the gas sampling rate of each chamber in real time to ensure that the height difference between the gas and liquid interfaces between the chambers is ≤10m.

[0031] Step 8: When terminating gas extraction, ensure that the final gas-liquid interface height does not exceed the safe height threshold of the deepest cavity.

[0032] Furthermore, in step two, based on the difference in the number of connecting channels between cavities, air is preferentially injected into the cavity with more connecting channels, and then into the cavity with fewer connecting channels.

[0033] Furthermore, in step six, based on the difference in the number of connecting channels between cavities, gas is preferentially drawn from the cavity with fewer connecting channels, and then gas is drawn from the cavity with more connecting channels.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention forms a topological network through satellite wells and central wells, and realizes multi-cavity linkage in conjunction with the inclined well system. Compared with the four-sided distribution, the six-sided distribution significantly improves the space utilization rate. For example, while constructing 7 salt cavities, only 7 injection and production gas wells and 3 brine discharge wells are needed. Moreover, the land area required for wellhead layout is small, requiring only 1 large well site and 6 small well sites, effectively reducing the ground land area.

[0036] 2. The honeycomb well layout of the present invention reduces the total length of horizontal wells, thereby significantly reducing construction costs. Furthermore, the shared inclined well setup can reduce the energy consumption required for brine collection and improve economic efficiency. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a honeycomb-type salt cavern gas storage structure according to the present invention.

[0038] In the diagram: 1. Cavity; 2. Satellite well; 3. Central well; 4. Inclined well; 5. Connecting passage. Detailed Implementation

[0039] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0040] Example 1:

[0041] A honeycomb-type salt cavern gas storage facility includes a central well field and satellite well fields. The central well field has one central well, and the satellite well fields have at least three satellite wells. The satellite wells are arranged on the same circumference and surround the central well. The bottoms of the satellite wells and the central well form cavities. The bottoms of the satellite wells are connected to each other through a first horizontal well to form a connecting channel. The central well is connected to any of the satellite wells through a second horizontal well. The facility also includes several inclined wells, each of which extends to the bottom open-hole section of a non-adjacent satellite well.

[0042] The distance between adjacent satellite wells is ≥250m.

[0043] The horizontal distance between the inclined well trajectory and the central well cavity is ≥50m, and the endpoint is located ≥200m below the top of the satellite well cavity.

[0044] This invention also discloses a cavity-building method for a honeycomb salt cavern gas storage facility, comprising the following steps:

[0045] Step 1: Drill satellite wells to the bottom of the salt layer, and then drill the first horizontal wells so that the satellite wells are connected to each other through the first horizontal wells to form a connecting channel;

[0046] Step 2: Drill a center well and a second horizontal well, and connect the center well to any satellite well through the second horizontal well;

[0047] Step 3: Drill an inclined well, extending it to the bottom of the open hole section of the satellite well vertical shaft, so that the inclined well connects with the first horizontal well;

[0048] Step 4: Simultaneously inject fresh water into the satellite well and the central well, and dynamically adjust the brine discharge rate through the inclined well to control the diameter of the connecting cavity dissolved from the first horizontal well and the second horizontal well to 10-15m.

[0049] Step 5: Based on the central well and satellite wells, water-soluble cavity creation is carried out. Through ultrasonic logging feedback, nitrogen gas anti-dissolution technology is used to regulate cavity growth. The height difference between the satellite well and the central well cavity is ≤20m.

[0050] Furthermore, in step three, when the depth of the inclined well is at a distance from the designed top height of the salt cavity, the inclination is calculated using the following formula:

[0051] When H-x2≤y≤H+H1, the drilling slope formula is:

[0052]

[0053] In the formula: x is the horizontal distance between the pipeline and the wellhead of the inclined shaft; y is the vertical distance between the pipeline and the wellhead of the inclined shaft; H is the distance between the top of the cavity and the wellhead; H1 is the distance between the top of the designed salt cavity and the bottom of the initial solution cavity; x1 is the distance between the wellhead of the inclined shaft and the wellhead of the central well, 10≤x1≤15; x2 is the vertical distance between the starting point and the top of the designed salt cavity, x2≥200; D is the diameter of the designed salt cavity; d is the horizontal distance between the end point of the inclined shaft and the center of the bottom of the initial solution cavity of the central well, 250≤d≤350. All units are meters.

[0054] In step one, an acoustic signal transmitter and receiver are used to directionally control the connection between the first horizontal well and the adjacent satellite well, while retaining a 200-250m naked-eye section.

[0055] This invention also discloses a gas injection and extraction method for a honeycomb salt cavern gas storage facility; comprising:

[0056] Gas injection and brine removal stage:

[0057] Step 1: Inject natural gas into the connecting cavity through the central well, and discharge brine through the inclined well;

[0058] Step 2: Based on the difference in cavity burial depth, gas is injected first into the cavity with the deepest burial depth, and then gas is injected into the cavity with the shallowest burial depth.

[0059] Step 3: During the synchronous gas injection process, adjust the gas injection rate of each chamber in real time to ensure that the height difference between the gas and liquid interfaces between the chambers is ≤10m.

[0060] Step 4: When terminating gas injection, ensure that the final gas-liquid interface height is not lower than the safe height threshold of the shallowest cavity.

[0061] Gas extraction stage:

[0062] Step 5: Gas is extracted through the central injection well, and brine is selectively replenished through the inclined well;

[0063] Step 6: Based on the differences in cavity burial depth, gas is first extracted from the cavity with the shallowest burial depth, and then from the cavity with a deeper burial depth.

[0064] Step 7: During the synchronous gas sampling process, adjust the gas sampling rate of each chamber in real time to ensure that the height difference between the gas and liquid interfaces between the chambers is ≤10m.

[0065] Step 8: When terminating gas extraction, ensure that the final gas-liquid interface height does not exceed the safe height threshold of the deepest cavity.

[0066] In step two, based on the difference in the number of connecting channels between cavities, air is injected first into the cavity with more connecting channels, and then into the cavity with fewer connecting channels.

[0067] In step six, based on the difference in the number of connecting channels between cavities, gas is preferentially drawn from the cavity with fewer connecting channels, and then gas is drawn from the cavity with more connecting channels.

[0068] Example 2:

[0069] This embodiment describes a method with 6 satellite wells and one central well.

[0070] Specifically:

[0071] The wells are arranged in a honeycomb pattern, with a central well in the middle of the well group and six satellite wells evenly distributed around it. Both the central well and the satellite wells are vertical shafts. The central cavity is connected to one satellite cavity, and adjacent satellite cavities are connected to each other. Three brine discharge wells are evenly distributed around the central well. The brine discharge wells are inclined shafts that extend to the bottom of the vertical section of the satellite wells and are used to discharge brine from the seven wells.

[0072] A second horizontal well is drilled below the central shaft, extending to the vicinity of the lower part of the vertical shaft of one satellite well. A first horizontal well is drilled below the vertical shafts of six satellite wells, extending to the vicinity of the lower part of the vertical shafts of adjacent satellite wells. Three brine discharge wells are evenly spaced near the central well, connected to the three satellite wells via inclined shafts, staggered from the satellite wells connecting to the central well. A connecting channel is created through the cavitation chambers of the first and second horizontal wells, forming a common cavitation chamber near the ends of the horizontal wells and the lower part of the vertical shafts. After connecting the bottoms of the intermediate well and the six wells, the horizontal well cavitation is stopped, and the cavitation chambers of the intermediate shaft and the six vertical shafts form a cavity, ultimately forming one intermediate cavity and six satellite cavities. The six satellite cavities are sequentially connected, and the intermediate cavity is connected to one of the satellite cavities. After the cavitation chambers are completed, the well group consists of 7 gas injection / production wells, 3 brine discharge wells, 1 intermediate well site, and 6 satellite well sites.

[0073] The distance between adjacent satellite wellheads shall not be less than 250m, and the distance from a satellite well to the central well shall not be less than 250m. The calculation of the distance between adjacent wells shall be based on a comprehensive determination of factors such as the geological characteristics and mechanical properties of the salt layer. Among them, the burial depth of the 7 cavity is 1500m-1600m, and the horizontal height difference between the cavities shall not exceed 20m to avoid the gas-liquid interface of some cavities being too high or too low due to different cavity heights. The cavity diameter is 80-100m.

[0074] The location of the inclined shaft needs to avoid the central well cavity to prevent the central well cavity from dissolving into the inclined shaft pipe.

[0075] The construction methods for the aforementioned six satellite wells and one central well are as follows:

[0076] S1: First, drill the vertical shaft (i.e., satellite well) from Gas 2 to Gas 7 to the designed depth; then drill the horizontal shaft of Gas 2 to the bottom of the designed vertical shaft section of Gas 7, retaining the open hole section; then drill the horizontal shaft of Gas 3 to connect with the bottom of the vertical shaft of Gas 2, retaining the open hole section; then drill the horizontal shaft of Gas 4 to connect with the bottom of the vertical shaft of Gas 3, retaining the open hole section; then drill the horizontal shaft of Gas 5 to connect with the bottom of the vertical shaft of Gas 4, retaining the open hole section; then drill the horizontal shaft of Gas 6 to connect with the bottom of the vertical shaft of Gas 5, retaining the open hole section; then drill the vertical shaft and horizontal shaft of Gas 7, drilling the vertical shaft of Gas 7 to connect with the end of the horizontal shaft of Gas 2, and drilling the horizontal shaft to connect with the bottom of the vertical shaft of Gas 6 (the horizontal shaft mentioned above in this section is the first horizontal shaft).

[0077] Then, drill the vertical shaft (i.e., the central shaft) of Gas 1 and the second horizontal shaft. The second horizontal shaft connects the bottom of Gas 1 and Gas 2, leaving the open hole section intact. Then, drill the Halogen 1, Halogen 2 and Halogen 3 shafts simultaneously next to the central shaft until they connect with the bottom of the vertical shaft sections of Gas 3, Gas 5 and Gas 7. Use the vertical shaft water injection and inclined shaft brine discharge mode to form a circulating cavity with 7 wells for water injection and 3 wells for brine discharge. When drilling the horizontal shafts, it is necessary to control the elevation difference between the starting point and the ending point of the 7 horizontal shafts to not exceed 5m.

[0078] S2: Fresh water or saline solution is simultaneously injected into wells 1 through 7 to dissolve the salt rock in the horizontal well section, and high-concentration brine is simultaneously discharged through wells 1 through 3 to form a horizontal channel and gradually expand the channel volume; water is injected into the central well channel and the satellite well channel to build the channel at the same time, reducing the channel construction time and ensuring that the diameter of each channel is close, with the diameter of the horizontal section channel controlled at 10-15m; during the construction of the horizontal section channel, the water injection flow rate of different wells is controlled according to the dissolution rate of different channels to ensure that the channel size meets the design requirements.

[0079] S3: After the horizontal channel is dissolved to the target diameter, cavity design is carried out with a single cavity volume of 800,000-1,000,000 cubic meters as the target. The cavity diameter is 80-100m, and a top plate of more than 50m is retained. Vertical well section water dissolution cavity is carried out according to the principle of bottom to top. The first dissolution layer is located at the bottom of the salt layer. The shape, diameter, height and top plate thickness of the cavity are monitored in real time using equipment such as ultrasonic logging and gyro inclinometer. According to the difference in cavity construction speed caused by the different number of cavity connecting channels in the central well and different satellite wells, nitrogen gas dissolution inhibition and other methods are flexibly used to control the cavity shape to ensure that the height difference between the 7 cavity bodies does not exceed 20m, and to avoid the gas-liquid interface of some cavities being too high or too low due to different cavity heights. When the cavity height and cavity diameter reach the design value, the cavity construction is completed.

[0080] The specific methods for gas injection and production in the aforementioned six satellite wells and one central well are as follows:

[0081] S1: After the cavity is constructed, natural gas is injected through the injection well, and brine is discharged through the deviated well. Due to the different number of connecting channels between the central well and different satellite wells, as well as the differences in the shape and burial depth of different cavities, it is necessary to flexibly control the gas injection rate between different gas wells. The general principle is to inject gas into the cavities with deeper burial depth first, and then into the cavities with shallower burial depth, and to inject gas into the cavities with more connecting channels first, and then into the cavities with fewer connecting channels, while maintaining simultaneous gas injection and brine discharge. During the gas injection process, it is necessary to control the gas injection rate of different wells, and always ensure that the height difference of the gas-liquid interface between each cavity is controlled within 10m. Finally, the height of the gas-liquid interface must not be lower than the safe height of the gas-liquid interface in the shallowest cavity.

[0082] S2: During the gas production stage, gas is produced from the injection well, and brine is selectively replenished from the inclined well according to the cavity conditions. Due to the different number of connecting channels between the central well and different satellite wells, as well as the differences in the shape and burial depth of different cavities, it is necessary to flexibly control the gas production rate between different gas wells. The general principle is to produce gas from the shallower cavities first, followed by the deeper cavities, and to produce gas from the cavities with fewer connecting channels first, followed by the cavities with more connecting channels, and then maintain simultaneous gas production. During the gas production process, it is necessary to control the gas production rate to ensure that the height difference of the gas-liquid interface between each cavity is controlled within 10m, and the final gas-liquid interface height must not exceed the safe height of the gas-liquid interface in the deepest cavity.

[0083] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A cavity-building method for a honeycomb salt cavern gas storage facility, the honeycomb salt cavern gas storage facility comprising a central well field and satellite well fields, wherein the central well field is provided with a central well, and the satellite well fields are provided with at least three satellite wells, the satellite wells being on the same circumference and surrounding the central well, the bottoms of the satellite wells and the central well forming cavities, the bottoms of the satellite wells being connected to each other through a first horizontal well to form a connecting channel, the central well being connected to any of the satellite wells through a second horizontal well, and further comprising a plurality of inclined wells, the plurality of inclined wells extending to the bottom open hole section of non-adjacent satellite wells; The cavity-building method for honeycomb salt cavern gas storage includes the following steps: Step 1: Drill satellite wells to the bottom of the salt layer, and then drill the first horizontal wells so that the satellite wells are connected to each other through the first horizontal wells to form a connecting channel; Step 2: Drill a center well and a second horizontal well, and connect the center well to any satellite well through the second horizontal well; Step 3: Drill an inclined well, extending it to the bottom of the open hole section of the satellite well vertical shaft, so that the inclined well connects with the first horizontal well; Step 4: Simultaneously inject fresh water into the satellite well and the central well, and dynamically adjust the brine discharge rate through the inclined well to control the diameter of the connecting cavity dissolved from the first horizontal well and the second horizontal well to 10-15m. Step 5: Based on the central well and satellite wells, water-soluble cavity creation is carried out. Through ultrasonic logging feedback, nitrogen gas anti-dissolution technology is used to regulate cavity growth. The height difference between the satellite well and the central well cavity is ≤20m.

2. The cavity-building method for a honeycomb salt cavern gas storage facility according to claim 1, characterized in that: The distance between adjacent satellite wells is ≥250m.

3. The cavity-building method for a honeycomb salt cavern gas storage facility according to claim 1, characterized in that: The horizontal distance between the inclined well trajectory and the central well cavity is ≥50m, and the endpoint is located ≥200m below the top of the satellite well cavity.

4. The method for creating a honeycomb-type salt cavern gas storage chamber according to claim 1, characterized in that: In step one, an acoustic signal transmitter and receiver are used to directionally control the connection between the first horizontal well and the adjacent satellite well, while retaining a 200-250m naked-eye section.

5. A gas injection and extraction method for a honeycomb salt cavern gas storage facility, wherein the gas storage facility is constructed using the cavity-building method of the honeycomb salt cavern gas storage facility as described in any one of claims 1-4. The gas injection and extraction method for honeycomb salt cavern gas storage facilities includes the following stages: Gas injection and brine removal stage: Step 1: Inject natural gas into the connecting cavity through the central well, and discharge brine through the inclined well; Step 2: Based on the difference in cavity burial depth, gas is injected first into the cavity with the deepest burial depth, and then gas is injected into the cavity with the shallowest burial depth. Step 3: During the synchronous gas injection process, adjust the gas injection rate of each chamber in real time to ensure that the height difference between the gas and liquid interfaces between the chambers is ≤10m. Step 4: When terminating gas injection, ensure that the final gas-liquid interface height is not lower than the safe height threshold of the shallowest cavity. Gas extraction stage: Step 5: Gas is extracted through the central injection well, and brine is selectively replenished through the inclined well; Step 6: Based on the differences in cavity burial depth, gas is first extracted from the cavity with the shallowest burial depth, and then from the cavity with a deeper burial depth. Step 7: During the synchronous gas sampling process, adjust the gas sampling rate of each chamber in real time to ensure that the height difference between the gas and liquid interfaces between the chambers is ≤10m. Step 8: When terminating gas extraction, ensure that the final gas-liquid interface height does not exceed the safe height threshold of the deepest cavity.

6. The gas injection and extraction method for a honeycomb salt cavern gas storage facility according to claim 5, characterized in that: In step two, based on the difference in the number of connecting channels between cavities, air is injected first into the cavity with more connecting channels, and then into the cavity with fewer connecting channels.

7. The gas injection and extraction method for a honeycomb salt cavern gas storage facility according to claim 5, characterized in that: In step six, based on the difference in the number of connecting channels between cavities, gas is preferentially drawn from the cavity with fewer connecting channels, and then gas is drawn from the cavity with more connecting channels.

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