Salt cavern energy storage well completion method without injection and production tubing

Abstract

This invention discloses a method for completing salt cavern energy storage wells without injection and production tubing, used for multi-stage completion operations. The method includes: during the final completion operation, setting an initial cemented annulus along the well wall inside the wellbore; after the final completion, sequentially running multiple cemented casings into the wellbore to a predetermined depth along the initial cemented annulus; injecting cement slurry into the annulus between the cemented casings and the initial cemented annulus to perform cementing operations; and after the cementing operations are completed, retrieving all cemented casings one by one to form a smooth and robust initial cemented annulus. This invention solves the technical problem of casing corrosion during salt cavern construction, leading to reduced casing strength and decreased salt cavern stability.

Description

Technical Field

[0001] This invention relates to the field of underground storage and construction engineering technology, and in particular to a method for completing salt cavern energy storage wells without injection and production tubing. Background Technology

[0002] Salt cavern gas storage facilities are underground caverns formed by injecting fresh water into thick underground salt layers or salt domes using a water-dissolving extraction method to dissolve the salt, and then draining the saturated or near-saturated brine. Due to the dense structure, low porosity, low permeability, high plastic deformation capacity, and self-healing properties of salt rock, it can serve as the best medium for storing oil, natural gas, and related products.

[0003] Against the backdrop of rapid development in carbon sequestration and hydrogen energy, the storage and utilization of CO2 and H2 have created a huge demand for large-scale underground storage space. my country possesses abundant salt rock resources, with an annual output of nearly 50 million tons of well-mined salt. Even based on current production levels, the annual increase in old salt deposits reaches 20 million cubic meters. 3 Utilizing underground salt caverns can effectively solve the problem of storing energy such as CO2 and H2. However, in salt cavern construction projects, conventional well completion methods require the use of casing to establish a flow channel between the surface and the salt cavern. The casing material (steel) is easily corroded by brine, CO2, H2, etc., which can damage its strength and is not conducive to the long-term stable operation of the salt cavern storage.

[0004] There is currently no effective solution to the problem that the casing is corroded during the salt cavern construction process, resulting in reduced casing strength and decreased salt cavern stability.

[0005] Therefore, based on years of experience and practice in related industries, the inventor proposes a method for completing salt cavern energy storage wells without injection and production tubing to overcome the shortcomings of existing technologies. Summary of the Invention

[0006] The purpose of this invention is to provide a method for completing salt cavern energy storage wells without injection and production tubing. In the final completion process, cement sheaths are used for completion, which avoids direct contact between the casing and the stored fluid during salt cavern construction and operation. It also avoids casing damage caused by corrosion and hydrogen embrittlement that are prone to occur when using casing, effectively preventing damage to the wellbore integrity.

[0007] The objective of this invention can be achieved through the following methods:

[0008] This invention provides a method for completing salt cavern energy storage wells without injection and production tubing, for performing multiple well completion operations. The method includes the following steps:

[0009] During the final well completion operation, an initial cement annulus is installed along the well wall inside the wellbore.

[0010] After the last drilling operation is completed, multiple cementing casings are sequentially run into the wellbore to a predetermined depth along the initial cement sheath wall.

[0011] Cement slurry is injected into the annulus within the wellbore and between the cementing casing and the initial cement sheath wall to perform cementing operations.

[0012] After the cementing operation is completed, all the cementing casings are pulled out one by one to form a smooth and strong cement sheath well wall.

[0013] In a preferred embodiment of the present invention, before sequentially running multiple cementing casings into the wellbore and along the initial cement sheath to a predetermined depth within the wellbore, a lubricating layer is applied to the outer wall of each cementing casing to reduce frictional resistance.

[0014] In a preferred embodiment of the present invention, the lubricating layer is formed by spraying a lubricating release agent, which is a mixture of concrete release agent and lubricant, onto the outer wall of the cementing casing.

[0015] In a preferred embodiment of the present invention, before sequentially lowering multiple cement casings into the wellbore and along the initial cement sheath to a preset depth within the wellbore, a centralizer with an upward self-unlocking function is provided on the cement casing. The centralizer is used to position the cement casing in the center of the wellbore as it is lowered into the wellbore.

[0016] In a preferred embodiment of the present invention, at least one of the three cementing casings connected in sequence is provided with the centralizer.

[0017] In a preferred embodiment of the present invention, the straightener includes at least two annular sleeve clamping members and a plurality of springs, wherein the plurality of springs are arranged at intervals along the circumference of the sleeve clamping members, and the two ends of the springs are respectively connected to the two sleeve clamping members.

[0018] The inner wall of the casing clamp is provided with a plurality of toothed plates along its circumference. The toothed plates have a plurality of protruding teeth arranged in an array on the plate surface facing the axis of the centralizer. The casing clamp is sleeved on the outside of the cementing casing, and the ends of the protruding teeth abut against the outer wall of the cementing casing.

[0019] In a preferred embodiment of the present invention, when the cementing casing is in a stabilizing state, the two casing clamps move toward each other to compress the spring plate and bend it away from the axis of the stabilizer, at least the outer wall of the middle portion of the spring plate abuts against the inner wall of the wellbore.

[0020] In a preferred embodiment of the present invention, the casing clamp is provided with a snap-fit ​​structure that automatically releases the toothed plate from locking the cementing casing when the cementing casing is lifted out.

[0021] The snap-fit ​​structure includes a receiving groove on the inner wall of the sleeve clamp and an extension plate on the top of the toothed plate. The bottom of the receiving groove is open, and a barb-shaped anti-retraction step is formed at the opening. The extension plate has an anti-retraction boss. The lower part of the anti-retraction step has a first guide surface that is inclined from bottom to top away from the axis of the stabilizer. The upper part of the anti-retraction boss has a second guide surface that is inclined from bottom to top away from the axis of the stabilizer.

[0022] When well completion operations are performed, the anti-reverse protrusion is located below the anti-reverse step, the end of the protrusion abuts against the outer wall of the cementing casing, and the snap-fit ​​structure is in a locked state;

[0023] When the cementing casing is lifted out, the toothed plate moves upward with the cementing casing. The first guide surface and the second guide surface come into contact and guide the anti-reverse protrusion into the receiving groove through the bottom opening of the receiving groove. The end of the protrusion separates from the outer wall of the cementing casing, and the snap-fit ​​structure is in the unlocked state.

[0024] In a preferred embodiment of the present invention, when the buckle structure is in the unlocked state, the bottom of the anti-reverse protrusion abuts against the top of the anti-reverse step.

[0025] In a preferred embodiment of the present invention, the buckle structure further includes a limiting groove located on the inner wall of the sleeve clamp and a limiting boss located on the plate surface of the toothed plate in the direction opposite to the axis of the straightener.

[0026] When performing well completion operations, the limiting boss is located below the limiting groove, and the limiting boss abuts against the inner wall of the casing clamp located below the limiting groove, so that the end of the protrusion abuts against the outer wall of the cementing casing.

[0027] When the cementing casing is lifted out, the limiting boss moves up with the toothed plate and enters the limiting groove, and the top of the limiting boss abuts against the top inner wall of the limiting groove.

[0028] In a preferred embodiment of the present invention, there are two limiting bosses, which are located at the top and bottom of the toothed plate in the direction away from the axis of the straightener, respectively, and there are two limiting grooves corresponding to the limiting bosses.

[0029] In a preferred embodiment of the present invention, there are multiple snap-fit ​​structures, and the multiple snap-fit ​​structures are arranged circumferentially along the sleeve clamping member.

[0030] In a preferred embodiment of the present invention, a sealing ring is provided on the inner wall of the casing clamp along its circumference, and the sealing ring is in close contact with the outer wall of the cementing casing.

[0031] In a preferred embodiment of the present invention, the well completion operation is a two-stage well completion, wherein a first-stage well completion operation is performed before the last stage well completion operation.

[0032] During the initial well opening operation, the drill is driven down to below the soil surface and a surface casing is installed.

[0033] In a preferred embodiment of the present invention, after the cementing operation is completed, the surface casing is retained inside the wellbore, and the surface casing is located on the outer periphery of the formed cement annulus well wall.

[0034] In a preferred embodiment of the present invention, the well completion operation is a three-stage well completion operation, wherein a first-stage well completion operation and a second-stage well completion operation are performed sequentially before the last stage well completion operation is performed.

[0035] During the first well opening operation, the drilling is carried out to a depth below the soil surface and a surface casing is installed.

[0036] During the second well completion operation, the drilling proceeds downwards to below the water-bearing and gas-bearing layers of the soil, and a technical casing is installed.

[0037] In a preferred embodiment of the present invention, after the cementing operation is completed, the surface casing and the technical casing are retained inside the wellbore, with the surface casing located on the outer periphery of the technical casing and the technical casing located on the outer periphery of the formed cement annulus well wall.

[0038] In a preferred embodiment of the invention, the thickness of the molded cement annular well wall is 1.5 inches to 2.0 inches.

[0039] In a preferred embodiment of the present invention, the cement slurry is injected into the annulus within the wellbore and between the cementing casing and the initial cement sheath wall. The cement slurry is an anti-corrosion cement slurry.

[0040] Based on the above, the characteristics and advantages of the salt cavern energy storage well completion method without injection and production tubing of the present invention are as follows:

[0041] During the final well completion operation, a cement sheath is installed on the wellbore wall to form an initial cement sheath wellbore wall. After the final drilling is completed, multiple cementing casings are sequentially driven into the wellbore to a predetermined depth. Then, cement slurry is injected into the annulus between the cementing casings and the initial cement sheath wellbore wall to perform cementing operations. After all the cementing casings are pulled out one by one, the cement slurry replenishes the annulus and forms a smooth and solid cement sheath wellbore wall on the basis of the initial cement sheath wellbore wall, thus achieving the purpose of cementing.

[0042] Throughout the final well completion process, cement sheaths were used for completion operations. After the cemented casing was lifted out, the formed cement sheath wall served as the wellbore wall. During salt cavern construction and operation, the fluid flowing through the wellbore directly contacted the formed cement sheath wall, avoiding direct contact with the cemented casing. This also prevented casing damage caused by corrosion and hydrogen embrittlement, which are common when using cemented casing. This effectively prevented damage to the integrity of the wellbore, ensuring the strength of the wellbore and the long-term, stable operation of the salt cavern. Attached Figure Description

[0043] The accompanying drawings are intended only to illustrate and explain the present invention and do not limit the scope of the invention.

[0044] in:

[0045] Figure 1 This is a flowchart of the salt cavern energy storage well completion method without injection and production tubing according to the present invention.

[0046] Figure 2 This is a schematic diagram of the wellbore structure for the second-stage completion operation in the salt cavern energy storage well completion method without injection and production tubing of the present invention.

[0047] Figure 3 This is a schematic diagram of the wellbore structure for the three-stage completion operation in the salt cavern energy storage well completion method without injection and production tubing of the present invention.

[0048] Figure 4 This is a schematic diagram showing the location of the centralizer in the salt cavern energy storage well completion method without injection and production tubing of the present invention.

[0049] Figure 5 This is a schematic diagram of the centralizer in the salt cavern energy storage well completion method without injection and production tubing of the present invention.

[0050] Figure 6 This is a top view of the centralizer in the salt cavern energy storage well completion method without injection and production tubing of the present invention.

[0051] Figure 7 :for Figure 5 A magnified view of a portion of position A in the middle.

[0052] Figure 8: This is a schematic diagram of the locking structure in the straightening device of the present invention in the locked state.

[0053] Figure 9 : This is a schematic diagram of the buckle structure in the straightening device of the present invention in the unlocked state.

[0054] The reference numerals in the accompanying drawings of this invention are:

[0055] 1. Molded cement annular well casing; 2. Cementing casing;

[0056] 3. Centralizer; 301. Sleeve clamp;

[0057] 3011, receiving groove; 30111, anti-reverse step;

[0058] 3012, limiting groove; 302, spring;

[0059] 303, toothed plate; 3031, convex tooth;

[0060] 3032, extension plate; 30321, anti-reverse boss;

[0061] 3033, Limiting boss; 304, Buckle structure;

[0062] 305. Sealing ring; 4. Surface sleeve;

[0063] 5. Technical casing; 6. Soil surface layer;

[0064] 7. Soil moisture content and aeration layer. Detailed Implementation

[0065] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0066] like Figure 1 As shown, this invention provides a method for completing salt cavern energy storage wells without injection and production tubing, used for multiple well completion operations. This method includes the following steps:

[0067] Step S1: During the final well completion operation, an initial cement sheath is installed along the well wall inside the wellbore;

[0068] Step S2: After the last drilling is completed, multiple cementing casings 2 are sequentially run into the wellbore to a preset depth along the initial cement sheath wall;

[0069] Step S3: Inject cement slurry into the annulus inside the wellbore and between the cementing casing 2 and the initial cement sheath wall to carry out cementing operations;

[0070] Step S4: After the cementing operation is completed, pull out all the cementing casings 2 one by one to form a smooth and solid cement annular well wall 1.

[0071] In this invention, during the final well completion operation, a cement sheath is installed on the wellbore wall to form an initial cement sheath well wall. After the final drilling is completed, multiple cementing casings 2 are sequentially driven into the wellbore to a predetermined depth. Then, cement slurry is injected into the annulus between the cementing casings 2 and the initial cement sheath well wall to perform cementing operations. After all the cementing casings 2 are pulled out one by one, the cement slurry replenishes the annulus and forms a smooth and solid shaped cement sheath well wall 1 on the basis of the initial cement sheath well wall, thus achieving the purpose of cementing. Throughout the final well completion process, cement sheaths were used for well completion operations. After the cemented casing 2 was finally lifted out, the formed cement sheath wall 1 served as the wellbore wall. During the salt cavern construction and operation, the fluid flowing through the wellbore directly contacted the formed cement sheath wall 1, avoiding direct contact with the cemented casing. This also prevented casing damage caused by various factors such as corrosion and hydrogen embrittlement that are prone to occur when using cemented casings. This effectively prevented damage to the integrity of the wellbore and ensured the strength of the wellbore and the long-term, stable operation of the salt cavern.

[0072] In an optional embodiment of the present invention, before the final well completion operation (i.e. before step S1), other well completion operations can be carried out in a conventional manner (using the current cementing process and cement slurry system) according to the well structure, and the cementing cement slurry needs to be returned to the surface. Only during the final well completion operation is a shaped cement annular well wall 1 established to play the role of preventing corrosion of the well wall.

[0073] In an optional embodiment of the present invention, before multiple cementing casings 2 are sequentially lowered into the wellbore to a preset depth (i.e., after the last drilling operation and before the cementing casings 2 are lowered), a lubricating layer is applied to the outer wall of each cementing casing 2 to be lowered. The lubricating layer is used to reduce the frictional resistance between the cementing casing 2 and the cement sheath, which facilitates the easy lifting and lowering of the cementing casing 2.

[0074] Furthermore, the lubricating layer can be formed by mixing a concrete release agent and a lubricant, and the lubricating release agent is sprayed onto the outer wall of the cementing casing 2 to form the casing. The concrete release agent and the lubricant are merely mixed; no chemical reaction occurs between them. This increases the lubrication function, allowing the cementing casing 2 to be smoothly pulled out after the formed cement annular well wall 1 has solidified. This further reduces the frictional resistance between the outer wall of the cementing casing 2 and the formed cement annular well wall 1 during the lifting and removal of the cementing casing 2, while ensuring that the cementing casing 2 and the formed cement annular well wall 1 do not adhere together.

[0075] In an optional embodiment of the present invention, before multiple cementing casings 2 are sequentially lowered into the wellbore to a preset depth (i.e., before step S2), a centralizer 3 with a self-unlocking lifting function is installed on the cementing casings 2, such as... Figure 4 As shown, the centralizer 3 is used to ensure that the cementing casing 2 is centered in the wellbore after it is lowered into the wellbore (i.e., the cementing casing 2 is coaxial with the wellbore), thereby achieving a more uniform thickness of the cement sheath at various positions in the circumferential direction. After the cement sheath well wall 1 solidifies, during the lifting of the cementing casing 2, the centralizer 3 automatically unlocks from the cementing casing 2 under the action of the lifting force, allowing the cementing casing 2 to be smoothly pulled out, while the centralizer 3 remains in the cement sheath well wall 1.

[0076] Furthermore, among the three cementing casings 2 connected in sequence, at least one cementing casing 2 is equipped with a centralizer 3 to ensure that the multiple cementing casings 2 sequentially lowered into the wellbore are in the central position within the wellbore.

[0077] In this embodiment, as Figures 5 to 9 As shown, the centralizer 3 includes at least two annular sleeve clamping members 301 and a plurality of elongated spring plates 302. The plurality of spring plates 302 are spaced apart and evenly arranged along the circumference of the sleeve clamping members 301, and one end of each spring plate 302 is connected to one sleeve clamping member 301, and the other end of each spring plate 302 is connected to another sleeve clamping member 301. A plurality of toothed plates 303 are evenly distributed along the circumference of the inner wall of the sleeve clamping member 301. The toothed plates 303 have a plurality of protruding teeth 3031 arranged in an array on the plate surface facing the axial direction of the centralizer 3. The shape and size of the 01 are adapted to the cementing casing 2, allowing the casing clamp 301 to be fitted onto the outside of the cementing casing 2. The ends of the protruding teeth 3031 on the toothed plate 303 can abut against the outer wall of the cementing casing 2. When the cementing casing 2 is in a straightened state, pressure is applied into the wellbore, causing the two casing clamps 301 to move closer together, thus compressing the spring 302 and bending it away from the axis of the straightener 3. This ensures that at least the middle outer wall of the spring 302 abuts against the inner wall of the wellbore, thereby clamping the cementing casing 2 and straightening it in the centered position within the wellbore. In another optional embodiment, when manufacturing the straightener 3, an existing spring straightener can be directly used, with toothed plates 303 added to both ends of the spring straightener for improvement, thus meeting the construction requirements.

[0078] Specifically, such as Figures 5 to 9As shown, the casing clamping member 301 is provided with a latching structure 304 that automatically releases the locking of the toothed plate 303 onto the cementing casing 2 when the casing 2 is lifted out. The latching structure 304 includes a receiving groove 3011 on the inner wall of the casing clamping member 301 and an extension plate 3032 on the top of the toothed plate 303. The receiving groove 3011 has an opening at the bottom, and a barbed anti-retraction step 30111 is formed at the opening. The extension plate 3032 has an anti-retraction boss 30321. The lower part of the anti-retraction step 30111 has a first guide surface inclined from bottom to top away from the axis of the centralizer 3, and the upper part of the anti-retraction boss 30321 has a second guide surface inclined from bottom to top away from the axis of the centralizer 3. Figure 7 As shown, during well completion operations, the anti-reverse protrusion 30321 is located below the anti-reverse step 30111, the end of the protrusion 3031 abuts against the outer wall of the cementing casing 2, and the latching structure 304 is in a locked state; as Figure 8 As shown, when the cementing casing 2 is lifted out, the toothed plate 303 moves upward with the cementing casing 2. The first guide surface and the second guide surface come into contact and guide the anti-reverse protrusion 30321 to enter the receiving groove 3011 through the bottom opening of the receiving groove 3011. The end of the tooth 3031 separates from the outer wall of the cementing casing 2, and the snap-fit ​​structure 304 is in the unlocked state.

[0079] Furthermore, such as Figure 9 As shown, when the buckle structure 304 is in the unlocked state, the bottom of the anti-reverse protrusion 30321 abuts against the top of the anti-reverse step 30111, thereby ensuring that the toothed plate 303 remains fixed when the cementing casing 2 is lifted. The toothed plate 303 will neither continue to move upward with the cementing casing 2 nor will it retract.

[0080] Furthermore, such as Figures 7 to 9 As shown, the snap-fit ​​structure 304 also includes a limiting groove 3012 located on the inner wall of the sleeve clamp 301 and a limiting boss 3033 located on the plate surface of the toothed plate 303 facing away from the axis of the centralizer 3; as Figure 7 As shown, during well completion operations, the limiting boss 3033 is located below the limiting groove 3012, and the limiting boss 3033 abuts against the inner wall of the casing clamp 301 located below the limiting groove 3012, so that the end of the protrusion 3031 abuts against the outer wall of the cementing casing 2; as Figure 8 As shown, when the cementing casing 2 is lifted out, the limiting boss 3033 moves up with the toothed plate 303 and enters the limiting groove 3012. The top of the limiting boss 3033 abuts against the top inner wall of the limiting groove 3012, so as to position the toothed plate 303 when the cementing casing 2 is lifted out.

[0081] Furthermore, such as Figures 7 to 9As shown, there are two limiting bosses 3033. One limiting boss 3033 is located on the top of the plate surface of the toothed plate 303 facing away from the axis of the stabilizer 3, and the other limiting boss 3033 is located on the bottom of the plate surface of the toothed plate 303 facing away from the axis of the stabilizer 3. There are two limiting grooves 3012 corresponding to the limiting bosses 3033, so as to ensure that the toothed plate 303 as a whole plays a stable positioning role.

[0082] Furthermore, there are multiple snap-fit ​​structures 304, which are spaced apart and evenly arranged along the circumference of the sleeve clamping member 301.

[0083] Furthermore, such as Figures 7 to 9 As shown, a sealing ring 305 is provided circumferentially on the inner wall of the casing clamp 301. The sealing ring 305 fits tightly against the outer wall of the cementing casing 2 to ensure that no cement slurry will invade the mating connection between the toothed plate 303 and the casing clamp 301 during the cementing slurry injection process, thereby ensuring that the mud and water slurry will not affect the self-unlocking function of the centralizer 3. The sealing ring 305 can be made of, but is not limited to, soft rubber material, and has a relatively thin thickness so that it will fall off and be sheared during the lifting process of the cementing casing 2, but it will not affect the normal lifting of the cementing casing 2.

[0084] In an optional embodiment of the present invention, when injecting cement slurry into the annulus within the wellbore and located between the cementing casing 2 and the initial cement sheath wall (i.e., in step S3), the cement slurry can be an anti-corrosion cement slurry. The anti-corrosion cement slurry refers to a cement slurry system that, after solidification, allows the cement sheath to maintain its strength under long-term erosion from CO2 and / or H2. After the cementing casing 2 is removed, the entire inner wall of the wellbore becomes the contact surface between the formed cement sheath wall 1 and the ambient gas. The amount of gas permeating into the formed cement sheath wall 1 will be much higher than in conventional casing cementing schemes; therefore, an anti-corrosion cement slurry is required to ensure that the formed cement sheath wall 1 will not be corroded during long-term use. Existing anti-corrosion cement slurry can be used; alternatively, corresponding anti-corrosion agents can be added according to the ambient gas to achieve the desired anti-corrosion effect. The specific type and dosage of the added anti-corrosion agent can be adjusted according to the actual ambient gas and are not limited here.

[0085] In this invention, the dimensions of the wellbore (or wellbore) and the cementing casing 2 can be designed according to the well structure and the strength of the cement sheath can be optimized. Since the inner side of the formed cement sheath well wall 1 is not supported by the cementing casing 2 after the last opening completion, the thickness of the formed cement sheath well wall 1 should be appropriately increased according to the strength of the formed cement sheath well wall 1. When setting the well diameter and cementing casing 2 for the last opening, the thickness of the formed cement sheath well wall 1 should be ensured to be 1.5 inches to 2.0 inches.

[0086] In an optional embodiment of the present invention, such as Figure 2 As shown, when the well completion operation is a two-stage completion (i.e., the well structure is designed as a two-stage well), a first-stage completion operation is performed before the final completion operation. To ensure the stability of the well wall in the soft soil layer 6 located on the soil surface and the secure installation of the wellhead equipment, a large-diameter drill bit is used to drill down to below the soil surface 6 during the first-stage completion operation, and a surface casing 4 is installed. After the cementing operation is completed, the surface casing 4 remains inside the wellbore and is located on the outer periphery of the formed cement annulus well wall 1. The cement slurry injected during the second-stage cementing operation needs to be returned to the surface to protect the surface casing 4 from contact with the ambient gas. After the cement slurry solidifies, the cementing casing 2 is removed, forming a formed cement annulus well wall 1 without injection and production tubing.

[0087] In another alternative embodiment of the invention, such as Figure 3 As shown, when the well completion operation is a three-stage completion (i.e., the well structure is designed in three stages), the first and second stage completion operations are performed sequentially before the final stage completion operation. During the first stage completion operation, a large-diameter drill bit is used to drill down to below the soil surface layer 6, and the surface casing 4 is installed. During the second stage completion operation, drilling is performed down to below the water-bearing and gas-bearing layers 7, and the technical casing 5 is installed. After cementing is completed, the surface casing 4 and the technical casing 5 remain inside the wellbore and are not removed. The surface casing 4 is located on the outer periphery of the technical casing 5, and the technical casing 5 is located on the outer periphery of the formed cement sheath well wall 1. Sufficient space is provided for the installation of the formed cement sheath well wall 1 to ensure that the cement sheath of the three-stage completion is not eroded by water and gas in the formation. During the third stage cementing, the cement slurry must be returned to the surface to protect the technical casing 5 from contact with gas.

[0088] The following is a specific embodiment provided by the present invention:

[0089] The salt rock layer is 1000m deep, and the designed depth of the three-section well is 1050m. A high-pressure aquifer is located between 700m and 750m, thus a three-section wellbore structure is suitable. In the first section, a 17.5-inch drill bit is used to drill to a formation depth of 70m, and a 16-inch diameter surface casing (4) is run in for cementing, with the cement slurry returned to the surface. In the second section, a 15-inch drill bit is used to drill to a formation depth of 800m, and a 13.5-inch diameter technical casing (5) is run in for cementing and to isolate the high-pressure aquifer. In the water-bearing layer, the cement slurry needs to be returned to the surface. In the third drilling operation, a 12.25-inch drill bit is used to drill to a depth of 1050m. In the third drilling operation, an 8.625-inch diameter cement casing 2 is used to construct the initial cement annulus well wall (thickened cement annulus). Before lowering the cement casing 2, a lubricating release agent is evenly sprayed onto the outer wall of each cement casing 2. A centralizer 3 with a self-unlocking function is installed on one of every three connected cement casing 2s. After the cement casing 2 reaches the preset depth in the wellbore, pre-prepared anti-corrosion cement slurry is injected into the annulus and allowed to solidify. After the anti-corrosion cement slurry solidifies, the cement casing 2 is lifted out. Under the action of the lubricating release agent, the cement casing 2 does not adhere to the cement slurry, and the lifting force causes the centralizer 3 to unlock. After the cementing casing 2 is completely removed, the centralizer 3 remains in the cement sheath, and the initial cement sheath well wall forms a smooth and solid shaped cement sheath well wall 1.

[0090] The features and advantages of the salt cavern energy storage well completion method without injection and production tubing of the present invention are as follows:

[0091] This salt cavern energy storage well completion method without injection and production tubing can effectively solve the problem of brine corrosion on the casing during the construction of salt cavern reservoirs. At the same time, it can also solve the problem of casing damage caused by the corrosive effect of ambient gas under high pressure after the reservoir is built. It provides a new completion method for salt cavern construction and provides important technical support for the long-term stable operation of salt cavern reservoirs.

[0092] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for completing salt cavern energy storage wells without injection and production tubing, used for multiple well completion operations, characterized in that, The method includes the following steps: During the final well completion operation, an initial cement annulus is installed along the well wall inside the wellbore. After the last drilling operation is completed, multiple cementing casings are sequentially run into the wellbore to a predetermined depth along the initial cement sheath wall. Cement slurry is injected into the annulus within the wellbore and between the cementing casing and the initial cement sheath wall to perform cementing operations. After the cementing operation is completed, all the cementing casings are pulled out one by one to form a smooth and strong cement sheath well wall.

2. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 1, characterized in that, Before sequentially running multiple cementing casings into the wellbore to a predetermined depth along the initial cement sheath, a lubricating layer is applied to the outer wall of each cementing casing to reduce frictional resistance.

3. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 2, characterized in that, The lubricating layer is formed by spraying a lubricating release agent, which is a mixture of concrete release agent and lubricant, onto the outer wall of the cementing casing.

4. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 1, characterized in that, Before the cementing casing is sequentially lowered into the wellbore and along the initial cement sheath wall to a preset depth within the wellbore, a centralizer with an upward self-unlocking function is installed on the cementing casing. The centralizer is used to position the cementing casing in the center of the wellbore as it is lowered into the wellbore.

5. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 4, characterized in that, Of the three cementing casings connected in sequence, at least one of the cementing casings is equipped with the centralizer.

6. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 4 or 5, characterized in that, The straightener includes at least two annular sleeve clamps and multiple springs. The multiple springs are arranged at intervals along the circumference of the sleeve clamps, and the two ends of the springs are respectively connected to the two sleeve clamps. The inner wall of the casing clamp is provided with a plurality of toothed plates along its circumference. The toothed plates have a plurality of protruding teeth arranged in an array on the plate surface facing the axis of the centralizer. The casing clamp is sleeved on the outside of the cementing casing, and the ends of the protruding teeth abut against the outer wall of the cementing casing.

7. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 6, characterized in that, When the cementing casing is in the stabilizing state, the two casing clamps move toward each other to compress the spring plate and bend it away from the axis of the stabilizer, so that at least the outer wall of the middle part of the spring plate abuts against the inner wall of the wellbore.

8. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 6, characterized in that, The casing clamp is provided with a buckle structure that automatically releases the toothed plate from locking the cementing casing when the cementing casing is lifted out. The snap-fit ​​structure includes a receiving groove on the inner wall of the sleeve clamp and an extension plate on the top of the toothed plate. The bottom of the receiving groove is open, and a barb-shaped anti-retraction step is formed at the opening. The extension plate has an anti-retraction boss. The lower part of the anti-retraction step has a first guide surface that is inclined from bottom to top away from the axis of the stabilizer. The upper part of the anti-retraction boss has a second guide surface that is inclined from bottom to top away from the axis of the stabilizer. When well completion operations are performed, the anti-reverse protrusion is located below the anti-reverse step, the end of the protrusion abuts against the outer wall of the cementing casing, and the snap-fit ​​structure is in a locked state; When the cementing casing is lifted out, the toothed plate moves upward with the cementing casing. The first guide surface and the second guide surface come into contact and guide the anti-reverse protrusion into the receiving groove through the bottom opening of the receiving groove. The end of the protrusion separates from the outer wall of the cementing casing, and the snap-fit ​​structure is in the unlocked state.

9. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 8, characterized in that, When the buckle structure is in the unlocked state, the bottom of the anti-reverse protrusion abuts against the top of the anti-reverse step.

10. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 8, characterized in that, The buckle structure also includes a limiting groove on the inner wall of the sleeve clamp and a limiting boss on the plate surface of the toothed plate facing away from the axis of the straightener. When performing well completion operations, the limiting boss is located below the limiting groove, and the limiting boss abuts against the inner wall of the casing clamp located below the limiting groove, so that the end of the protrusion abuts against the outer wall of the cementing casing. When the cementing casing is lifted out, the limiting boss moves up with the toothed plate and enters the limiting groove, and the top of the limiting boss abuts against the top inner wall of the limiting groove.

11. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 10, characterized in that, The number of limiting bosses is two, and the two limiting bosses are respectively located at the top and bottom of the plate surface of the toothed plate in the direction away from the axis of the straightener. The two limiting grooves are corresponding to the limiting bosses.

12. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 8, characterized in that, The number of the snap-fit ​​structures is multiple, and the multiple snap-fit ​​structures are arranged along the circumference of the sleeve clamp.

13. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 6, characterized in that, A sealing ring is provided on the inner wall of the casing clamp along its circumference, and the sealing ring is tightly fitted to the outer wall of the cementing casing.

14. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 1, characterized in that, The well completion operation is a two-stage well completion operation, wherein a first-stage well completion operation is performed before the final well completion operation is performed. During the initial well opening operation, the drill is driven down to below the soil surface and a surface casing is installed.

15. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 14, characterized in that, After the cementing operation is completed, the surface casing remains inside the wellbore, and the surface casing is located on the outer periphery of the formed cement annulus well wall.

16. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 1, characterized in that, The well completion operation is a three-stage well completion operation. Before the final well completion operation, the first-stage well completion operation and the second-stage well completion operation are performed in sequence. During the first well opening operation, the drilling is carried out to a depth below the soil surface and a surface casing is installed. During the second well completion operation, the drilling proceeds downwards to below the water-bearing and gas-bearing layers of the soil, and a technical casing is installed.

17. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 16, characterized in that, After the cementing operation is completed, the surface casing and the technical casing remain inside the wellbore, with the surface casing located on the outer periphery of the technical casing and the technical casing located on the outer periphery of the formed cement annulus well wall.

18. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 1, characterized in that, The thickness of the molded cement annular well wall is 1.5 inches to 2.0 inches.

19. The method for completing a salt cavern energy storage well without injection and production tubing as described in claim 1, characterized in that, The cement slurry is injected into the annulus inside the wellbore and located between the cementing casing and the initial cement sheath wall. The cement slurry is an anti-corrosion cement slurry.

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