Cavity-forming device and method for salt cavern gas storage

Abstract

The present invention relates to a cavity forming device and method for a salt cavern gas storage reservoir. The cavity forming device includes an inner tube, and the inner tube includes: a middle perforated section which is configured to be hollow, and one or more inner tube flow holes are provided on the side wall of the middle perforated section and radially penetrate through the side wall of the middle perforated section; and a lower fixed section which is configured to be inserted into a salt rock pit for supporting the cavity forming device.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas storage caverns, and particularly to a cavity forming device for salt cavern gas storage caverns. The present invention also relates to a cavity forming method for salt cavern gas storage caverns. Background Art

[0002] The cavity forming project of salt cavern gas storage caverns is a key project for building salt cavern gas storage caverns. The cavity forming project is usually carried out through a cavity forming string. The cavity forming string includes an outer pipe and an inner pipe sleeved inside the outer pipe. Corresponding flow ports are formed at the lowermost ends of the inner pipe and the outer pipe. On the one hand, a first fluid channel is formed between the outer pipe and the inner pipe. On the other hand, a second fluid channel is formed inside the inner pipe. One of the first fluid channel and the second fluid channel is used for supplying liquid from the wellhead, and the other is used for discharging liquid to the wellhead, so as to form a cycle.

[0003] During the cavity forming process, the string is lowered into the gas storage cavern, and the height positions of the flow ports on the inner pipe and / or the outer pipe are adjusted by lifting and lowering the inner pipe and / or the outer pipe, and the position and shape of the cavity forming are changed by changing the distribution of the brine concentration field in the cavity. For a salt cavern gas storage cavern with multiple interlayers, it is necessary to lift the inner pipe of the cavity forming and / or the outer pipe multiple times according to the distribution of the interlayers, change the height of the water outlet of the inner and outer pipes of the cavity forming, and specifically dissolve and collapse the interlayers to control the shape of the cavity.

[0004] However, during the process of forming a cavity by solution mining in a salt cavern gas storage cavern, the cavity forming string needs to be in a suspended state, and accidents of bending and damage of the cavity forming string (especially the inner pipe) often occur. The bending and damage of the cavity forming string are very unfavorable for the construction of the gas storage cavern, which will not only greatly increase the construction cost of the gas storage cavern, but also lead to frequent well repairs, thus prolonging the construction period.

[0005] CN109139110A discloses a string system. This system forms a screen pipe structure through the outer pipe and the inner pipe and is used to prevent the inner pipe from bending. In this patent, a prolongation section is arranged below the outer pipe and a centralizer is arranged between the prolongation section and the inner pipe to prevent the string from bending. However, this structure will seriously reduce the adjustable range of the height positions of the flow ports between the outer pipe and the inner pipe. It is difficult to meet the requirements for controlling the collapse of the interlayers and the shape of the cavity in a salt cavern gas storage cavern with multiple interlayers, and the cavity forming efficiency is also relatively low. In addition, setting a plurality of screen holes on the outer pipe will reduce the strength and structural stability of the outer pipe. Summary of the Invention

[0006] In view of the above problems, the present invention provides a cavity forming device and method for salt cavern gas storage caverns. By using this device and method, at least one of the above problems can be eliminated or at least weakened.

[0007] According to a first aspect of the present invention, a cavity making device for a salt cavern gas storage is proposed, comprising an inner tube, wherein the inner tube comprises: a middle perforated section, wherein the middle perforated section is hollow, and a side wall of the middle perforated section is provided with one or more inner tube flow holes radially penetrating the side wall of the middle perforated section; and a lower fixed section, wherein the lower fixed section is configured to be inserted into a salt rock pit to support the cavity making device.

[0008] Through this cavity making device, the lower end of the inner tube can be fixed and supported by the salt rock pit. In this state, even if there is liquid-solid coupling instability in the well, the inner tube is not easy to bend or damage. This is conducive to improving the structural stability of the entire cavity making device and improving its adaptability to the well environment. The cost of this cavity making device is also relatively low and the service life is long.

[0009] Preferably, the lower fastening section is solid in design.

[0010] Preferably, the lower end of the lower fixing section is configured to be conical.

[0011] Preferably, the cavity-making device also includes a covering tube, which extends along the middle perforated section and is wrapped around the middle perforated section, and the covering tube is sealingly matched with the middle perforated section so that the inner tube flow holes on the middle perforated section covered by the covering tube are closed, and the inner tube flow holes on the middle perforated section staggered with the covering tube are opened; wherein the covering tube can move in the longitudinal direction relative to the middle perforated section.

[0012] Preferably, the cavity creation device further comprises a control mechanism configured to control the longitudinal movement of the covering tube relative to the middle perforated section.

[0013] Preferably, the control mechanism is a hydraulically driven control mechanism, and the control mechanism is arranged on the ground.

[0014] Preferably, the cavity-making device further comprises an outer tube, which is sleeved outside the inner tube at a distance from the inner tube and extends in the longitudinal direction, forming an annular channel between the outer tube and the inner tube, and forming an inter-tube flow opening at the lower end of the outer tube that communicates with the annular space.

[0015] According to a second aspect of the present invention, a cavity making method for a salt cavern gas storage is proposed, comprising the following steps: lowering a cavity making device into a well until a lower fixed section of an inner tube in the cavity making device is inserted into a salt rock pit for support.

[0016] Preferably, the cavity making method also includes the following steps: after the cavity making device is lowered into the well, lifting or lowering the outer tube to adjust the height position of the inter-tube flow opening formed at the lower end of the outer tube, and the inter-tube flow opening is connected to the annular space formed between the outer tube and the inner tube.

[0017] Preferably, the cavity making method also includes the following steps: after the cavity making device is lowered into the well, the covering tube wrapped around the middle perforated section of the inner tube is moved longitudinally relative to the inner tube, and when one or more inner tube flow holes on the middle perforated section that are connected to the internal space of the inner tube are covered by the covering tube, the inner tube flow holes are closed, and when the inner tube flow holes are staggered with the covering tube, the inner tube flow holes are opened; wherein the height position of the opened inner tube flow holes is adjusted by moving the covering tube longitudinally.

[0018] Preferably, the longitudinal movement of the cladding tube is driven by hydraulic drive or electric control.

[0019] Preferably, the cavity creating method can be implemented by the above-mentioned cavity creating device of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be described in more detail below with reference to the accompanying drawings, wherein:

[0021] Figure 1 A schematic structural diagram of a cavity making device for a salt cavern gas storage according to one embodiment of the present invention is shown;

[0022] Figure 2 Shows Figure 1 A working state of the cavity-forming device in.

[0023] In the drawings, the same reference numerals are used for the same components. The drawings are not drawn to scale. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 The figure schematically shows a schematic diagram of a cavity making device 100 for a salt cavern gas storage according to an embodiment of the present invention.

[0026] The cavity making device 100 includes an inner tube 4 extending in the longitudinal direction. The inner tube 4 includes a hollow upper connecting section 41, a hollow middle section with holes 42, and a lower fixing section 43 connected in sequence from top to bottom. The upper connecting section 41 is used to extend to the wellhead. The side wall of the middle section with holes 42 is provided with one or more inner tube flow holes 42A extending radially therethrough, which are used to connect the inner space of the inner tube 4 with the external environment of the cavity making device. The lower fixing section 43 can be as shown in FIG.Figure 1 Inserted into the salt rock pit 7 in the salt cavern as shown, for fixing and supporting the inner tube 4 in the salt cavern. The lower fixing section 43 can have a relatively large weight to facilitate fixing. Here, the lower fixing section 43 can be made of metal materials such as steel or copper, for example. The lower fixing section 43 is solid, for example, which is beneficial to increasing the weight of the lower fixing section 43 on the one hand and ensuring that the inner tube 4 is only communicated with the external environment through the inner tube flow hole 42A on the other hand.

[0027] As Figure 1 shown, the lower end of the lower fixing section 43 is configured to be conical. The lower fixing section 43 with this shape has good insertability and is easy to insert into salt rock or salt rock debris.

[0028] Here, the lower fixing section 43 is not provided with the inner tube flow hole 42A like the middle perforated section 42. Therefore, when injecting fluid into the salt cavern through the inner tube 4 to dissolve the salt rock, the salt rock near the lower fixing section 43 is not easily dissolved. Thus, the lower fixing section 43 can be stably fixed in the above-mentioned salt rock pit 7. In this case, the gravity of the lower fixing section 43 and the fixing effect of the salt rock can effectively keep the lower end of the inner tube 4 fixed. In this case, the inner tube and the cavity-forming device 100 including it are not easily bent and damaged.

[0029] Also as Figure 1 shown, the cavity-forming device 100 further includes an outer tube 3 sleeved outside the inner tube 4 and extending in the longitudinal direction. The outer tube 3 is spaced apart from the inner tube 4, thereby forming an annular space between the outer tube 3 and the inner tube 4. The lower end of the outer tube 3 is configured to be open, and thus a tube-interval flow opening 3A is formed for communicating the annular space inside the outer tube 3 with the external environment of the cavity-forming device 100. The outer tube 3 can move longitudinally relative to the inner tube 4, for example, by a pipe hoisting machine. It should be noted that the lower end of the outer tube 3 is always higher than the lower end of the inner tube 4, and preferably higher than the lower end of the middle perforated section 42 of the inner tube 4, or higher than the lowermost inner tube flow hole 42A on the middle perforated section 42.

[0030] In addition, the cavity forming device 100 further includes a cladding tube 5 sleeved between the inner tube 4 and the outer tube 3. The cladding tube 5 extends along the middle perforated section 42 of the inner tube 4 and wraps around the outside of the middle perforated section 42. The cladding tube 5 is in sealing cooperation with the inner tube 4. For example, sealing rings for sealing cooperation with the inner tube 4 can be provided on the inner sides of the upper and lower ends of the cladding tube 5. Thus, when the side wall of the cladding tube 5 covers the inner tube flow holes 42A on the middle perforated section 42, the cladding tube 5 can close the inner tube flow holes 42A to prevent the communication between the inner space of the inner tube 4 and the external environment through the closed inner tube flow holes 42A. When the side wall of the cladding tube 5 is offset from the inner tube flow holes 42A on the middle perforated section 42, the inner tube flow holes 42A are opened, allowing the communication between the inner space of the inner tube 4 and the external environment through the opened inner tube flow holes 42A.

[0031] It should be understood that the lower end of the outer tube 3 is always higher than the lower end of the cladding tube 5 so that the opened inner tube flow holes 42A are always below the inter-tube flow opening 3A.

[0032] As Figure 1 shown, the length of the cladding tube 5 is designed to only allow the cladding tube to cover a part of the inner tube flow holes 42A. For example, when the upper end of the cladding tube 5 exactly covers and closes the uppermost inner tube flow hole 42A on the middle perforated section 42, a part of the lowermost inner tube flow holes 42A will be below the lower end of the cladding tube 5 (i.e., not covered and closed by the cladding tube 5) and thus be in an opened state. This is advantageous for the case where it is always not desired to close all the inner tube flow holes 42A on the inner tube. For example, during the process of lowering the cavity forming device 100, through this structure, a part of the inner tube flow holes 42A (such as the lowermost ones) can be kept open to overcome the buoyancy of the cavity forming device 100 and facilitate its faster lowering. Moreover, this structure enables the state of keeping a part of the inner tube flow holes 42A open to be achieved without additional operations.

[0033] In the present invention, as Figure 1As shown, the cavity forming device 100 further includes a control mechanism 1 disposed on the ground. The control mechanism 1 is cooperatively connected with the cladding tube 5. The control mechanism 1 can be, for example, a hydraulically driven control mechanism to be hydraulically connected to the cladding tube 5. Alternatively, the control mechanism 1 can also be electrically controlled and electrically connected to the cladding tube 5, such as by wired or radio connection. The control mechanism 1 can control the up and down movement of the cladding tube 5 along the middle perforated section 42 so that at least a part of the inner tube flow holes 42A on the middle perforated section 42 is closed by the cladding tube 5 or opened due to being offset from the cladding tube 5. That is to say, in the present invention, in order to adjust the height position of the opened inner tube flow holes 42A, the cladding tube 5 can be driven to move by the control mechanism 1 without lifting and lowering the inner tube 4 (such as by a pipe hoist). Compared with lifting and lowering the inner tube 4, the movement of the cladding tube 5 driven by the control mechanism 1 consumes much less time and cost. And this control is relatively flexible and has higher precision.

[0034] It should be understood that, as needed, the control mechanism 1 can also be lowered into the well together with the inner tube 4.

[0035] It should be understood that, as an alternative or in addition, an additional opening can also be provided in the middle of the cladding tube 5 for opening the inner tube flow holes 42A aligned with the through holes. The inner tube flow holes 42A covered by the part of the cladding tube 5 below the opening can still be in a closed state. This is beneficial to more precisely control the height position of the opened inner tube flow holes 42A.

[0036] Next, reference will be made to Figure 1 and Figure 2 to describe the cavity forming method of the present invention in detail. The cavity forming method can be carried out by the cavity forming device 100 described above.

[0037] First, the entire cavity forming device 100 is lowered into the well. As Figure 1 shown, it can be lowered into the casing 2 in the well until the lower fixed section 43 of the inner tube 4 is inserted into the salt rock pit 7 and fixed. During this process, the cladding tube 5 can be offset from at least a part of the inner tube flow holes 42A at the bottom to open these inner tube flow holes 42A. Thus, the lowering process can be accelerated.

[0038] After the entire cavity-making device 100 is lowered into the casing 2, the height positions of the outer tube 3 and the covering tube 5 can be changed while keeping the lower fixed section 43 of the inner tube 4 fixed in the salt rock pit 7. For example, the height of the outer tube 3 can be raised or lowered by a pipe lifting machine, thereby raising or lowering the height position of the inter-tube flow opening 3A. In addition, the covering tube 5 can be driven to move upward or downward by the control mechanism 1, thereby exposing more or less inner tube flow holes 42A below the covering tube 5. Exposing more inner tube flow holes 42A means that the height position of the opened inner tube flow holes 42A (at the top) is higher. Exposing fewer inner tube flow holes 42A means that the height position of the opened inner tube flow holes 42A (at the top) is lower.

[0039] For example, Figure 2 In the state shown, the cladding tube 5 and the outer tube 3 move upward to a position offset from the interlayer 62 of the salt cavern, but still opposite to the interlayer 61. At this time, the inner tube flow hole 42A opposite to the interlayer 62 is opened, and the interlayer 62 can be dissolved in a targeted manner. Thereafter, the cladding tube 5 and the outer tube 3 can continue to move upward to be offset from the interlayer 61, so that the inner tube flow hole 42A opposite to the interlayer 61 is opened, so that the interlayer 61 can be dissolved in a targeted manner.

[0040] In addition, the distance between the opened inner tube flow hole 42A and the inter-tube flow opening 3A can be changed by changing the distance between the lower end of the cladding tube 5 and the lower end of the outer tube 3. This can change the path of fluid circulation (for example, wider or narrower). This is also conducive to adjusting the shape of the formed cavity.

[0041] The above-mentioned cavity making device 100 can keep the lower end of the inner tube 4 inserted into the salt rock pit 7 stable and motionless, thereby avoiding bending and damage of the pipe column. In addition, when the lower end of the inner tube 4 is stably fixed, the corresponding inner tube flow holes 42A on the middle perforated section 42 of the inner tube 4 can be exposed or covered by lifting or lowering the covering tube 5. In this way, the position of the opened inner tube flow holes 42A can be effectively controlled. This is conducive to improving the efficiency of cavity making. In addition, the height adjustable range of the opened inner tube flow holes 42A and the inter-tube flow openings 3A can be large enough to meet various cavity shapes.

[0042] After the cavity is created, the cavity creation device 100 can be taken out and another gas injection and brine removal pipe string can be lowered to perform gas injection and brine removal operations. Since the salt rock pit 7 can be retained in the salt cavern, the gas injection and brine removal pipe string can be lowered into the salt rock pit 7. This is conducive to discharging more brine during the gas injection and brine removal process, thereby improving the cavity utilization rate of the salt cavern.

[0043] Although the present invention has been described with reference to the preferred embodiments, various modifications can be made thereto and components thereof can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any manner. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A cavity-forming device for a salt cavern gas storage reservoir, comprising an inner pipe, and the inner pipe includes: A middle perforated section, which is configured to be hollow, and one or more inner pipe flow holes radially penetrating the side wall of the middle perforated section are provided on the side wall of the middle perforated section; and A lower fixed section, which is configured to be inserted into a salt rock pit for supporting the cavity-forming device, and the lower fixed section is configured to be solid; The cavity-forming device further includes a cladding pipe, which extends along the middle perforated section and wraps outside the middle perforated section. The cladding pipe is in sealing cooperation with the middle perforated section to close the inner pipe flow holes on the middle perforated section covered by the cladding pipe and open the inner pipe flow holes on the middle perforated section staggered from the cladding pipe; wherein, the cladding pipe can move longitudinally relative to the middle perforated section so as to expose more or fewer of the inner pipe flow holes below the cladding pipe; The cavity-forming device further includes an outer pipe, which is sleeved outside the inner pipe at an interval and extends in the longitudinal direction. An annular space is formed between the outer pipe and the inner pipe, and a pipe-interval flow opening communicating with the annular space is formed at the lower end of the outer pipe. The outer pipe can move longitudinally relative to the inner pipe so as to change the distance between the opened inner pipe flow holes and the pipe-interval flow opening by changing the distance between the lower end of the outer pipe and the lower end of the cladding pipe, The cladding pipe and the outer pipe are configured to be able to move upward to make the opened inner pipe flow holes face a specific interlayer, so as to dissolve the specific interlayer specifically.

2. The cavity-forming device for a salt cavern gas storage reservoir according to claim 1, characterized in that, The lower end of the lower fixed section is configured to be conical.

3. The cavity-forming device for a salt cavern gas storage reservoir according to claim 1, wherein The cavity-forming device further includes a control mechanism, which is configured to longitudinally move the cladding pipe relative to the middle perforated section.

4. The cavity forming device for a salt cavern gas storage reservoir according to claim 3, characterized in that, The control mechanism is a hydraulically driven control mechanism, and the control mechanism is arranged on the ground.

5. A method for creating a cavity in a salt cavern gas storage reservoir, characterized in that, The cavity-forming method is realized by the cavity-forming device according to any one of claims 1 to 4, and includes the following steps: Lower the cavity-forming device into the well until the lower fixed section of the inner pipe in the cavity-forming device is inserted into the salt rock pit to achieve support.

6. The method for creating a cavity for a salt cavern gas storage reservoir according to claim 5, wherein, It further includes the following steps: After the cavity-forming device is lowered into the well, lift or lower the outer pipe to adjust the height position of the pipe-interval flow opening formed at the lower end of the outer pipe, and the pipe-interval flow opening communicates with the annular space formed between the outer pipe and the inner pipe.

7. The method for creating a cavity for a salt cavern gas storage reservoir according to claim 5, characterized in that, It further includes the following steps: After the cavity-forming device is lowered into the well, move the cladding pipe wrapped outside the middle perforated section of the inner pipe longitudinally relative to the inner pipe. When one or more inner pipe flow holes communicating with the inner space of the inner pipe on the middle perforated section are covered by the cladding pipe, the inner pipe flow holes are closed. When the inner pipe flow holes are staggered from the cladding pipe, the inner pipe flow holes are opened; Wherein, the height position of the opened inner pipe flow holes is adjusted by longitudinally moving the cladding pipe.

8. The method for creating a cavity for a salt cavern gas storage reservoir according to claim 7, wherein The longitudinal movement of the cladding pipe is driven by a hydraulic drive or an electric control method.

Images