Drilling and displacement integrated pipe column and multi-stage gas injection and brine displacement method for salt cavern gas storage

Abstract

The application discloses a kind of drilling and draining integrated pipe column and salt cavern gas storage multi-stage gas injection and brine discharge method.The drilling and draining integrated pipe column includes drill bit, drilling tool, first brine discharge device, second brine discharge device and brine discharge pipe column arranged in sequence from bottom to top.The pipe wall of first brine discharge device is provided with first bypass hole, and the bypass hole is blocked by patch, and the dissolution time of patch in brine is greater than the set time threshold value.The second brine discharge device includes at least one brine discharge short section, and the brine discharge short section is provided with switch and second bypass hole on the pipe wall, and the second bypass hole is connected with the outside or not by opening or closing of the switch.The drilling of residue in salt cavern gas storage and the effective discharge of brine above residue surface, brine in residue and small residue particles can be realized, and the effective storage volume and comprehensive economic benefit of gas storage are improved.

Description

Technical Field

[0001] This invention relates to the field of gas storage well completion technology, and in particular to an integrated drilling and tubing string and a multi-stage gas injection and brine removal method for salt cavern gas storage. Background Technology

[0002] Many countries around the world are developing salt cavern gas storage facilities. The history of using salt caverns as gas storage facilities can be traced back to World War II in the 20th century. Due to the high purity of salt layers abroad, the accumulation of insoluble matter in salt rock gas storage facilities is often relatively small. Research has mainly focused on salt rock storage site selection technology, salt layer drilling and completion technology, salt rock cavity filtration technology, salt rock cavity shape control technology, and salt rock cavity stability technology. Currently, there are no related technologies for drilling holes inside the residue, multi-stage brine removal to expand the gas storage space, and brine removal tubing to prevent residue blockage.

[0003] The abundance of muddy interlayers and high content of insoluble impurities in my country's salt rock often results in large accumulations of insoluble matter, with some areas containing over 50% insoluble matter. These accumulations not only waste a significant portion of reservoir capacity but also pose safety hazards for subsequent gas injection, brine removal, and downhole operations. Therefore, some domestic scholars have conducted research on the formation mechanism of insoluble salt residues, the void volume of these accumulations, the settling behavior of insoluble residue particles in brine, the treatment of residual brine in salt cavities, and pore formation of residue accumulations. However, drilling techniques within the non-lithogenic residue at the bottom of the cavity and brine removal techniques within the residue are still in the exploratory stage. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide an integrated drilling and drilling string and a multi-stage gas injection and brine removal method for salt cavern gas storage to overcome or at least partially solve the above problems. This method realizes the drilling of residues in salt cavern gas storage and the effective removal of brine above the residue surface, brine in the residue, and small residue particles, thereby improving the effective storage volume and overall economic benefits of the gas storage.

[0005] In a first aspect, embodiments of the present invention provide an integrated drilling and stringing system, comprising a drill bit, a drill string, a first brine discharge device, a second brine discharge device, and a brine discharge string arranged sequentially from bottom to top;

[0006] The first bypass hole is provided on the pipe wall of the first brine discharge device. The first bypass hole is blocked by a patch. The patch can dissolve in the brine, and the dissolution time is greater than a set time threshold.

[0007] The second brine discharge device includes at least one brine discharge section. The brine discharge section is equipped with a switch. When the switch is open, a second bypass hole on the wall of the brine discharge section is connected to the outside. When the switch is closed, the second bypass hole is not connected to the outside.

[0008] Secondly, embodiments of the present invention provide a multi-stage gas injection and brine removal method for a salt cavern gas storage facility, comprising performing the following steps using the aforementioned integrated drilling and drilling string:

[0009] The integrated drilling and drilling string is lowered into the production string to drill into the residue at the bottom of the salt cavern gas storage tank.

[0010] The brine discharge section of the integrated drilling and lining string located in the area from the first set depth below the brine surface to the residue surface is identified as the effective brine discharge section. The switch of the effective brine discharge section is opened, and the gas injection and brine discharge operation is carried out until the distance between the uppermost effective brine discharge section and the brine surface reaches the first set distance. The gas injection and brine discharge operation is then paused, and the switch of the effective brine discharge section is closed.

[0011] If there is more than one effective brining drain section, resume the aeration and brining draining operation until the distance between another effective brining drain section and the brine surface reaches the first set distance, then return to the pause aeration and brining draining operation until all effective brining drain sections are turned off.

[0012] Continue the gas injection and brine discharge operation, and discharge some of the particles and brine from the residue to the ground through the first brine discharge device.

[0013] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0014] (1) The integrated drilling and drilling string provided in this embodiment of the invention includes a drill bit, a drill string, a first brine discharge device, a second brine discharge device and a brine discharge string arranged sequentially from bottom to top. The drill bit and drilling tools are configured to allow drilling into the residue in the salt cavern gas storage tank. A first bypass hole is provided on the pipe wall of the first brine discharge device. This first bypass hole is sealed with a patch that dissolves in the brine. The dissolution time exceeds a set time threshold, ensuring that the first brine discharge device is not connected to the outside during residue drilling. When discharging brine from within the residue, the patch completely dissolves, and the first bypass hole becomes an effective channel for the discharge of brine and small residue particles. The second brine discharge device includes at least one short discharge section equipped with a switch. When the switch is open, the second bypass hole on the pipe wall of the discharge section connects to the outside. When the switch is closed, the second bypass hole is not connected to the outside, ensuring that the second brine discharge device is not connected to the outside during residue drilling. When discharging brine above the residue surface, the switch is opened, making the second bypass hole an effective channel for brine discharge.

[0015] (2) The multi-stage gas injection and brine discharge method for salt cavern gas storage provided in this embodiment of the invention can not only discharge the brine above the residue surface, but also discharge some of the brine and small particles inside the residue. Compared with the conventional gas injection and brine discharge process, the salt cavern gas storage can expand the effective gas storage space by 14% to 18%, thereby significantly increasing the working gas volume and economic benefits of the salt cavity. When the old cavity of the high residue brine well in the salt mine is renovated and utilized, the effective space volume of the cavity can be increased by 25% to 33%, which can not only significantly shorten the time for brine dissolution and cavity construction, but also save a lot of construction costs. This can promote the renovation and utilization of the old cavity of the high residue brine well in the salt mine, promote the development and construction of salt cavern gas storage, and bring great economic and social benefits.

[0016] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 This is a schematic diagram of the integrated drilling and sprue string in Embodiment 1 of the present invention;

[0020] Figure 2 This is a flowchart of the brine injection and discharge method for a salt cavern gas storage tank in Embodiment 2 of the present invention;

[0021] Figure 3 This is a schematic diagram of the air-driven brine discharge operation using a three-stage brine discharge section in Embodiment 2 of the present invention;

[0022] Figure 4 This is a schematic diagram of the air-driven brine removal operation using the second and third stage brine removal sections in Embodiment 2 of the present invention;

[0023] Figure 5 This is a schematic diagram of the air-driven brine discharge operation using the third-stage brine discharge section in Embodiment 2 of the present invention;

[0024] Figure 6 This is a schematic diagram of the gas-driven brine discharge operation using the first-stage brine discharge device in Embodiment 2 of the present invention;

[0025] Figure 7 This is a schematic diagram of a conventional gas injection and brine discharge process. Detailed Implementation

[0026] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] In the description of this invention, it should be noted that the terms "comprising," "including," "having," "containing," etc., are all open-ended terms, meaning that they include but are not limited to. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] To address the limitations of existing technologies in effectively drilling into salt cavern gas storage facilities and effectively removing brine above the residue surface, brine within the residue, and small residue particles, this invention provides an integrated drilling and drilling string and a multi-stage gas injection and brine removal method for salt cavern gas storage facilities. This method enables effective drilling into the residue surface and effective removal of brine above the residue surface, brine within the residue, and small residue particles, thereby increasing the effective storage volume and overall economic benefits of the gas storage facility.

[0031] Example 1

[0032] Embodiment 1 of the present invention provides an integrated drilling and blasting string, the structure of which is as follows: Figure 1 As shown, it includes, from bottom to top, a drill bit 1, a drill string 2, a first brine discharge device 3, a second brine discharge device, and a brine discharge pipe string 5.

[0033] The first bypass hole is provided on the pipe wall of the first brine discharge device 3. The first bypass hole is blocked by a patch that can dissolve in the brine. The dissolution time of the patch in the brine is longer than a set time threshold, so that the patch will not be dissolved prematurely during the drilling process. The set time threshold can be reasonably set according to factors such as the expected drilling time, safety time, and brine discharge time above the residue surface. A soluble patch with matching material can be selected according to the set time threshold.

[0034] The soluble patch possesses sufficient compressive, tensile, and shear strength to ensure no leakage occurs when the integrated drill string drills along the residue, and that the first brine discharge device does not break or detach when the drill bit encounters jamming, thus not affecting the implementation of the integrated drill string drilling process along the residue. The patch completely self-dissolves in the brine after a certain period. After self-dissolution, the first bypass hole on the wall of the first brine discharge device remains unobstructed, providing an inlet channel for the discharge of brine and small residue particles from the residue.

[0035] The second brine discharge device includes at least one brine discharge section ( Figure 1 Taking the three-stage brine draining section as an example, namely the first-stage brine draining section 41, the second-stage brine draining section 42, and the third-stage brine draining section 43, the brine draining section is equipped with a switch. When the switch is open, the second bypass hole on the tube wall of the brine draining section is connected to the outside. When the switch is closed, the second bypass hole is not connected to the outside.

[0036] The brine draining section is a brine draining device that can be repeatedly opened and closed. Any brine draining section can be closed or opened as needed. At the same time, the repeated opening and closing of the brine draining section can reduce the probability of the second bypass hole being blocked by crystals after being immersed in brine for a long time.

[0037] The brine draining short section that can be repeatedly opened and closed is usually set with 3 to 4 stages (segments). This is because there is uncertainty in the drilling depth of the integrated drilling and sprue string along the bottom of the cavity residue. By optimizing the installation position of the multiple brine draining short sections on the integrated drilling and sprue string, it can be ensured that at least one brine draining short section can approach the residue surface, so that the brine above the residue surface can be discharged to the ground through the brine draining short section that is close to the residue surface.

[0038] In some embodiments, the brine draining section includes an inner cylinder and an outer cylinder, with a ball-type switch connected to the upper part of the inner cylinder. When the switch is open, the second bypass hole on the inner cylinder wall overlaps with the second bypass hole on the outer cylinder wall, meaning the brine draining section communicates with the outside through the second bypass hole. When the switch is closed, the second bypass hole on the inner cylinder wall does not overlap with the second bypass hole on the outer cylinder wall, meaning the brine draining section is not communicated with the outside.

[0039] Preferably, the position, shape, and size of the second bypass hole on the inner tube wall and the second bypass hole on the outer tube wall are matched, and when the switch is open, the second bypass hole on the inner tube wall and the second bypass hole on the outer tube wall can completely overlap.

[0040] Furthermore, the ball-type switch includes a spring, a reset mechanism, and a ball seat arranged sequentially from bottom to top.

[0041] The ball seat can be a hollow hemisphere. A repeated ball-throwing and pressing method is used, with the outer diameter of the ball matching the inner diameter of the ball seat, so that the ball presses precisely on the base. The pressure of the ball, plus the pressure of the overlying fluid generated by the ball blockage, compresses the spring, thus pressing down the reset mechanism and the inner cylinder until the reset mechanism is jammed. At this point, the switch is in the open state, and the second bypass hole on the inner cylinder wall overlaps with the second bypass hole on the outer cylinder wall. When the switch needs to be closed, a ball with an outer diameter matching the inner diameter of the ball seat is thrown in, so that the ball presses precisely on the base. The pressure of the ball, plus the pressure of the overlying fluid generated by the ball blockage, causes the spring to gradually reset. The inner cylinder moves upward under the action of the reset mechanism, and the switch is in the closed state. The second bypass hole on the inner cylinder wall no longer overlaps with the second bypass hole on the outer cylinder wall.

[0042] If the second brine discharge device includes multiple brine discharge sections, from bottom to top, the inner diameter of the ball seat of each brine discharge section decreases from large to small, and the difference in the inner diameter of the ball seat of two adjacent brine discharge sections is greater than the set inner diameter difference threshold.

[0043] The brine drain section can be repeatedly opened and closed. Depending on the construction or operation requirements, the second bypass hole on the brine drain section can be repeatedly opened and closed by repeatedly throwing balls to pressurize it.

[0044] Preferably, the inserted balls can completely self-dissolve within a certain period of time without affecting subsequent operations.

[0045] In some embodiments, at least one layer of sand-proof screen is provided on the outer wall of the first brine discharge device and the outer wall of the brine discharge short section of the second brine discharge device.

[0046] During the brine discharge process, a sand-proof screen can effectively prevent large-diameter impurities in the brine from clogging the tubing.

[0047] Preferably, the area of ​​the sand-proof screen is larger than the area of ​​the bypass hole distribution area.

[0048] The integrated drilling and drilling string provided in Embodiment 1 of the present invention includes a drill bit, a drill string, a first brine discharge device, a second brine discharge device, and a brine discharge string arranged sequentially from bottom to top. The drill bit and drilling tools are configured to allow drilling into the residue in the salt cavern gas storage tank. A first bypass hole is provided on the pipe wall of the first brine discharge device. This first bypass hole is blocked by a patch that dissolves in the brine. The dissolution time exceeds a set time threshold, ensuring that the first brine discharge device is not connected to the outside during residue drilling. When discharging brine from within the residue, the patch completely dissolves, and the first bypass hole becomes an effective channel for the discharge of brine and small residue particles. The second brine discharge device includes at least one short discharge section equipped with a switch. When the switch is open, the second bypass hole on the pipe wall of the discharge section connects to the outside. When the switch is closed, the second bypass hole is not connected to the outside, ensuring that the second brine discharge device is not connected to the outside during residue drilling. When discharging brine above the residue surface, the switch is opened, making the second bypass hole an effective channel for brine discharge.

[0049] In some embodiments, the integrated drill string further includes a release handle 6 disposed at the upper end of the second brine removal device; the release handle 6 is used to remove the portion of the integrated drill string including the release handle and above the release handle when the release handle fails to be used to remove the integrated drill string.

[0050] The multi-functional release lever is installed at the top of the uppermost brine discharge section of the integrated tubing string and is hydraulically operated. When abnormal or complex situations occur downhole requiring the abandonment of all tubing below the multi-functional release lever, or when tubing needs to be retrieved from the cavity after gas injection and brine discharge operations, pressure is applied by engaging the control rod, causing the sliding sleeve to descend and open the locking block of the multi-functional release lever, thus releasing the tubing string. During the lifting and retrieval of the upper tubing string, the control rod and sliding sleeve are locked, maintaining a disconnect between the inside and outside of the integrated tubing string, thereby enabling pressurized tubing string retrieval operations.

[0051] In some embodiments, the integrated drilling and queuing string further includes a weighted queuing string 7 disposed at the upper end of the first queuing device; the weight per unit length of the weighted queuing string 7 is greater than the weight per unit length of the queuing string.

[0052] The weighted brine discharge string provides additional power for the drill bit to drill through the residue, which can assist the drill bit in effective drilling within the residue.

[0053] In some embodiments, the drill bit is a four-wing stepped scraper drill bit; the drilling tool is a screw drill tool.

[0054] Through repeated experiments, it was found that the four-wing stepped scraper drill bit and screw drill string are more suitable for drilling into the residue. The appropriate drill bit and drill string, as well as the setting of the weighted brine removal string, all ensure the effective drilling of the integrated string into the residue.

[0055] The aforementioned brine discharge tubing can be a regular tubing string, and the integrated tubing string is equivalent to a regular tubing string when drilling along the residue.

[0056] A brine discharge pipe section connects the first brine discharge device and the second brine discharge device; if the second brine discharge device includes multiple brine discharge short sections, a brine discharge pipe section connects two adjacent brine discharge short sections.

[0057] Furthermore, a safety valve 8 is installed at the top of the brine discharge column.

[0058] The integrated drilling and lining tubing provided in Embodiment 1 of this invention integrates multiple functions such as "efficient drilling along the residue, multi-stage brine drainage deep into the residue, and prevention of residue blockage in the tubing". Based on the current gas injection and brine drainage process, it further discharges some brine and residue particles from the salt chamber and the bottom of the chamber.

[0059] Example 2

[0060] Embodiment 2 of the present invention provides a multi-stage gas injection and brine discharge method for a salt cavern gas storage facility, the process of which is as follows: Figure 2 As shown, the following steps are performed using any of the drill-and-run integrated tubing strings in Example 1:

[0061] Step S21: Insert the integrated drilling and drilling string into the production string and drill into the residue at the bottom of the salt cavern gas storage tank.

[0062] After the brine dissolution and cavity creation in the salt cavern is completed, the depth of the residual surface is accurately probed using a conventional tubing string. Based on factors such as the depth of the residual surface, the optimal installation position of the brine discharge short section of the second brine discharge device in the integrated drilling and tubing string is determined, as well as whether a weighted brine discharge tubing string needs to be installed on the upper end of the first brine discharge device.

[0063] The first bypass hole on the first brine discharge device of the integrated drilling and sluice string is normally blocked by a soluble patch, and the second bypass hole on the brine discharge short section of the second brine discharge device is also normally closed. Therefore, the integrated drilling and sluice string is equivalent to an oil tubing string when drilling along the slag.

[0064] The assembled drill string is lowered into the salt cavity. After the drill bit of the drill string reaches the residue surface, the drill string is lifted until the drill bit is at the second set distance from the residue surface. The drill string is then drilled into the residue using a low-pressure, suspended drilling method to form a hole. Drilling continues until the set condition is reached, at which point drilling is stopped.

[0065] The second set distance mentioned above can be approximately 0.5m.

[0066] Specifically, the integrated tubing is lowered into the salt cavity, and the lowering speed is controlled when it is close to the depth of the residue surface. The integrated tubing is slowly lowered, and after reaching the residue surface, it is raised by about 0.5m. The pump is slowly started on the ground, and the "small drilling pressure hoisting" drilling method is adopted. The screw drill on the integrated tubing drives the scraper drill bit to slowly drill a hole in the residue surface. After the integrated tubing has drilled a hole in the residue at the bottom of the cavity, the scraper drill bit is pushed to slowly drill along the residue until the predetermined depth is reached or the scraper drill bit can no longer drill in the residue.

[0067] After drilling along the residue at the bottom of the cavity is completed, the brine in the salt cavity is discharged to the ground in stages using the multi-section reusable brine discharge section of the second brine discharge device and the first brine discharge device. The specific steps include the following:

[0068] Step S22: Determine the brine discharge short section of the integrated drilling and lining string located in the area from the first set depth below the brine surface to the residue surface, and designate it as the effective brine discharge short section.

[0069] The initial depth can be 2 to 3 meters. If the short drain section is too close to the brine surface and used as a drain channel, there is a safety hazard such as gas leakage.

[0070] Step S23: Open the switch of the effective brine draining section and perform air injection and brine draining operation until the distance between the uppermost effective brine draining section and the brine surface reaches the first set distance.

[0071] In order from bottom to top, insert soluble balls with diameters matching the inner diameter of the ball seat of the current effective brine discharge section, and turn on the switch of the current effective brine discharge section.

[0072] Specifically, first insert a soluble ball with a diameter matching the inner diameter of the ball seat of the lowest effective brine discharge section, and turn on the switch of the lowest effective brine discharge section; then insert a soluble ball with a diameter matching the inner diameter of the ball seat of the previous effective brine discharge section... until all the switches of the effective brine discharge sections are turned on.

[0073] Gas is injected into the salt cavern gas storage facility through the annulus between the production tubing and the integrated drilling and blasting tubing, and brine is discharged through the integrated drilling and blasting tubing.

[0074] Step S24: Pause the gas injection and brine discharge operation, and turn off the switch of the effective brine discharge section that has reached the first set distance from the brine surface.

[0075] Insert a soluble ball with a diameter matching the inner diameter of the ball seat of the effective brine discharge section, and close the switch of the effective brine discharge section when the distance between the effective brine discharge section and the brine surface reaches the first set distance.

[0076] Step S25: Resume the aeration and bleaching operation until the distance between the other effective bleaching section and the brine surface reaches the first set distance.

[0077] Return to step S24 until all valid brine drain sections are closed.

[0078] Step S26: Determine that all effective brine drain sections are closed.

[0079] At this point, the process of draining the brine from the surface of the residue is complete.

[0080] Step S27: Continue the aeration and brine discharge operation, and discharge the remaining brine above the residue surface, some particles inside the residue, and brine to the ground through the first brine discharge device.

[0081] The gas injection and brine removal operation also includes adjusting the surface gas injection parameters based on the wellhead fluid return situation of the integrated drilling and tubing string. The gas injection parameters mainly include the gas injection volume and injection rate.

[0082] Specifically, taking the integrated tubing string with a three-stage repeatable bleaching sub as an example, during gas injection and bleaching operations, the brine and small particle residue in the brine cavity can be discharged to the surface through the three-stage repeatable bleaching sub and the first bleaching device. The implementation steps are as follows: Step 1, determine the well depth of each component on the integrated tubing string based on data such as the actual drilling depth along the bottom of the cavity; Step 2, sequentially open the three-stage repeatable bleaching sub by ball-dropping and pressurizing, using the second bypass hole of the three-stage repeatable bleaching sub as a drainage channel, inject high-pressure natural gas into the brine cavity through the annulus between the production tubing (injection and production tubing) and the integrated tubing string, pushing the brine through the drainage channel into the inner cavity of the integrated tubing string and discharging it to the surface (see Appendix). Figure 3 (As shown); Step 3, during the gas injection and brine drainage process, when the dynamic fluid level of the brine is close to the first-stage repeatable brine drainage sub, suspend the gas injection and brine drainage operation, and close the first-stage repeatable brine drainage sub by dropping a ball and pressurizing it; Step 4, after waiting for the dropped ball to dissolve on its own, slowly open the well and resume the gas injection and brine drainage operation, using the fluid inlet channels of the second-stage and third-stage repeatable brine drainage subs installed on the integrated tubing string for brine drainage (see attached). Figure 4 (As shown); Step 5, when the brine level is close to the second-stage repeatable brine discharge section, repeat Step 3, close the second-stage repeatable brine discharge section, and discharge the brine using the inlet channel of the third-stage repeatable brine discharge section (see Appendix). Figure 5 (As shown); Step 6: When the depth of the brine fluid is close to the third-stage repeatable brine discharge section, the gas injection and brine discharge operation is also suspended, and the third-stage repeatable brine discharge section is closed by throwing a ball to pressurize.

[0083] After the sphere inside the third-stage reusable brine discharge sub completely dissolves, the well can be opened slowly without moving the tubing, and gas injection can be continued. The next stage of gas injection and brine discharge operation can be started using the first brine discharge device at the bottom of the integrated tubing, which can discharge the remaining brine above the residue surface, some of the brine inside the residue, and residue particles to the surface.

[0084] During the brine discharge process above the residue surface, the soluble patches on the wall of the first brine discharge device completely self-dissolve, and the first bypass hole becomes open, providing an inlet channel for the discharge of brine and residue particles from the residue. Through continuous gas injection, some of the brine and small-diameter residue particles within the residue are driven through the inlet channel into the integrated tubing and discharged to the ground (see attached diagram). Figure 6 (As shown).

[0085] After the brine gas drive discharge operation in the salt cavity and residue is completed, the integrated tubing string is pulled out under pressure for well completion. When the integrated tubing string is buried by residue at the bottom of the cavity and the lifting resistance is too high, the control rod is inserted into the integrated tubing string to pressurize it, pushing the sliding sleeve downward to open the locking block of the multi-functional release mechanism, thereby releasing the tubing string under pressure.

[0086] Appendix Figure 7 This is a schematic diagram of a conventional aeration and brine discharge process. Most of the brine above the residue surface can be discharged through the brine discharge pipe column. However, during the aeration and brine discharge process, due to the bending of the brine discharge pipe column or for safety reasons (such as preventing gas leakage), a certain depth of brine will still remain above the residue surface.

[0087] The brine injection and drainage method for salt cavern gas storage provided in Embodiment 2 of this invention can not only drain the brine above the residue surface, but also drain some of the brine and small particles within the residue. Compared with conventional injection and drainage processes, the salt cavern gas storage can expand the effective gas storage space by more than 14%, thereby significantly increasing the working gas volume and economic benefits of the salt cavity. When renovating and utilizing old cavities in high-residue brine wells in salt mines, it can increase the effective space volume of the cavity by more than 25%, which can significantly shorten the time for brine dissolution and cavity construction, and also save a lot of construction costs. This can promote the renovation and utilization of old cavities in high-residue brine wells in salt mines, promote the development and construction of salt cavern gas storage, and bring significant economic and social benefits.

[0088] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0089] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0090] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments; however, those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims.

Claims

1. An integrated drilling and casing string, characterized in that, It includes, from bottom to top, a drill bit, a drill string, a first brine discharge device, a second brine discharge device, and a brine discharge tubing; The first bypass hole is provided on the pipe wall of the first brine discharge device. The first bypass hole is blocked by a patch. The dissolution time of the patch in the brine is greater than a set time threshold. The second brine discharge device includes multiple brine discharge sections, from bottom to top, the inner diameter of the ball seat of each brine discharge section decreases from large to small, and the difference in the inner diameter of the ball seat of two adjacent brine discharge sections is greater than a set inner diameter difference threshold; the brine discharge section is equipped with a switch, in the state where the switch is open, the second bypass hole provided on the tube wall of the brine discharge section is connected to the outside, in the state where the switch is closed, the second bypass hole is not connected to the outside; The brine discharge section includes an inner cylinder and an outer cylinder. A ball-type switch is connected to the upper part of the inner cylinder. When the switch is open, the second bypass hole on the inner cylinder wall overlaps with the second bypass hole on the outer cylinder wall. When the switch is closed, the second bypass hole on the inner cylinder wall does not overlap with the second bypass hole on the outer cylinder wall. The ball-throwing switch includes a spring, a reset mechanism, and a ball seat arranged sequentially from bottom to top; A brine discharge pipe section is connected between the first brine discharge device and the second brine discharge device; if the second brine discharge device includes multiple brine discharge short sections, a brine discharge pipe section is connected between two adjacent brine discharge short sections.

2. The integrated drill string as described in claim 1, characterized in that, It also includes a release mechanism located at the top of the second brine drain device; The "drop handle" is used to retrieve the integrated drill string when the attempt to retrieve it fails, and to retrieve the portion of the integrated drill string including the drop handle and above the drop handle.

3. The integrated drill string as described in claim 1, characterized in that, It also includes a weighted brine discharge column installed at the upper end of the first brine discharge device; The weight per unit length of the weighted brine discharge column is greater than that of the brine discharge column.

4. The integrated drill string as described in claim 1, characterized in that, The drill bit is a four-wing stepped scraper drill bit; The drilling tool is a screw drill.

5. The integrated drill string as described in any one of claims 1 to 4, characterized in that, At least one layer of sand-proof screen is provided on the outer wall of the first brine discharge device and the outer wall of the brine discharge section of the second brine discharge device.

6. A multi-stage gas injection and brine discharge method for a salt cavern gas storage facility, characterized in that, This includes performing the following steps using the integrated drill string as described in any one of claims 1 to 5: The integrated drilling and drilling string is lowered into the production string to drill into the residue at the bottom of the salt cavern gas storage tank. The brine discharge section of the integrated drilling and sprue string located in the area from the first set distance below the brine surface to the above the residue surface is identified as the effective brine discharge section. The switch of the effective brine discharge section is turned on, and the gas injection and brine discharge operation is carried out until the distance between the uppermost effective brine discharge section and the brine surface reaches the first set distance. The gas injection and brine discharge operation is then paused, and the switch of the effective brine discharge section is turned off. If there is more than one effective brining drain section, resume the aeration and brining draining operation until the distance between another effective brining drain section and the brine surface reaches the first set distance, then return to the pause aeration and brining draining operation until all effective brining drain sections are turned off. Continue the gas injection and brine discharge operation, and discharge the brine above the residue surface, some particles inside the residue, and brine to the ground through the first brine discharge device.

7. The method as described in claim 6, characterized in that, The switch for opening the effective brine drainage section specifically includes: In order from bottom to top, insert soluble balls with diameters matching the inner diameter of the ball seat of the current effective brine discharge section, and turn on the switch of the current effective brine discharge section.

8. The method as described in claim 6, characterized in that, The residue drilled into the bottom of the salt cavern gas storage facility specifically includes: After the drill bit of the integrated drilling and row string reaches the residue surface, the integrated drilling and row string is lifted until the drill bit is at a second predetermined distance from the residue surface. The drilling method of low drilling pressure and lifting is adopted to drill into the residue and form a hole; Continue drilling until the set condition is reached, then stop drilling.

9. The method according to any one of claims 6 to 8, characterized in that, The gas injection and brine discharge operation also includes: Adjust the surface gas injection parameters based on the wellhead fluid return situation of the integrated drilling and tubing string.

10. The method according to any one of claims 6 to 8, characterized in that, The gas injection and brine discharge operation specifically includes: Gas is injected into the salt cavern gas storage tank through the annulus between the production tubing and the integrated drilling and blasting tubing, and brine is discharged through the integrated drilling and blasting tubing.

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