Well drilling method for injection-production well of salt cavern gas storage

Abstract

The invention belongs to the technical field of oil and gas storage and transportation, and discloses a drilling method for an injection-production well of a salt cavern gas storage. The well drilling method for the injection-production well of the salt cavern gas storage comprises the following steps that a first-opening well hole is drilled, and a surface layer casing pipe is put into the first-opening well hole; drilling equipment is used for drilling a second preset length in the vertical direction, drilling a third preset length in the preset direction forming an included angle with the vertical direction and drilling a fourth preset length in the vertical direction in sequence, and a second-opening well hole is formed; an anchoring part is installed at the lower end of the production casing and anchored to the well wall under the action of pressure; and drilling a third-opening well hole. According to the drilling construction method for the injection-production well of the salt cavern gas storage, the influence degree of earth surface obstacles on injection-production well construction is reduced, and a foundation is laid for improving the cavity building efficiency of the injection-production well, the natural gas injection and extraction rate and the utilization rate of salt mine resources.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas storage and transportation, and in particular to a drilling method for injection and production wells of salt cavern gas storage reservoirs. Background Art

[0002] At present, underground gas storage, as an important facility for natural gas storage, plays a key role in balancing gas transmission, improving pipeline utilization and ensuring gas supply security. According to different geological conditions, underground gas storage can be mainly divided into four types: depleted oil and gas reservoir type, aquifer type, salt cave type and mine type. Among them, salt cave gas storage mainly stores natural gas in closed salt-dissolved caves formed by fresh water dissolving salt layers, and has excellent sealing performance and extremely low permeability (permeability is less than 10m 2 -18m 2 ), huge storage capacity (single chamber volume can reach hundreds of thousands of cubic meters) and high safety factor, it is regarded as one of the most ideal underground natural gas storage facilities.

[0003] During the construction of salt cavern gas storage, injection and production wells must be drilled on the surface to connect the underground cavity with the surface. However, existing injection and production wells for salt cavern gas storage generally use small vertical well structures with diameters generally not exceeding 500mm. In areas with surface obstacles, this vertical well design can severely restrict construction feasibility. Moreover, for deep salt cavern gas storage, the small wellbore directly limits the natural gas flow rate, reducing natural gas injection and production efficiency and potentially causing flow assurance issues such as gas-liquid carryover.

[0004] Therefore, there is an urgent need for a drilling method for injection and production wells in salt cavern gas storage to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a drilling method for injection and production wells in salt cavern gas storage, which ensures the safety and stability of natural gas injection and production, reduces the impact of surface obstacles on the construction of injection and production wells, and lays a foundation for improving the cavity creation efficiency of injection and production wells, the rate of injection and production of natural gas, and the utilization rate of salt mine resources.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] A drilling method for a salt cavern gas storage injection and production well is provided, wherein the injection and production well comprises a primary wellbore, a secondary wellbore, and a tertiary wellbore, wherein a production casing is installed in the secondary wellbore. The drilling method for a salt cavern gas storage injection and production well comprises the following steps:

[0008] S1. Drilling a first preset length in a vertical direction using drilling equipment to form an open wellbore, and running a surface casing having a diameter of not less than 508.0 mm into the open wellbore;

[0009] S2. Using a drilling device, drilling a second preset length, a third preset length, and a fourth preset length in the vertical direction in sequence to form a second wellbore, wherein the preset direction is set at an angle to the vertical direction;

[0010] S3. Install an anchor at the lower end of the production casing, lower the production casing into the secondary wellbore, and connect the upper end of the production casing to the surface casing. The diameter of the production casing must be no less than 339.7 mm.

[0011] S4. Increase the pressure in the production casing, and anchor the anchor to the wellbore wall of the secondary wellbore under the action of pressure;

[0012] S5. Drilling a fifth preset length vertically from the lower end of the second wellbore using drilling equipment to form a third wellbore.

[0013] Optionally, the anchor member includes an anchor body and a plurality of flukes, wherein the plurality of flukes are provided along an extension direction of the anchor body and a circumferential direction of the anchor body, the flukes are rotatably connected to the anchor body, and the flukes have a retracted state parallel to the extension direction of the anchor body and an anchored state arranged at an angle to the extension direction of the anchor body;

[0014] In step S3, during the process of running the production casing into the secondary wellbore, the anchor claw is in a retracted state. In step S4, the anchor claw is opened from the retracted state to the anchored state under pressure and anchored into the wellbore wall of the secondary wellbore.

[0015] Optionally, a connecting piece is provided on the anchor body, and the connecting piece is connected to the bottom end of the production casing;

[0016] Step S3 specifically includes the following steps:

[0017] S31. Install a connector at the bottom end of the production casing, and connect the anchor body to the production casing through the connector;

[0018] S32. Lower the production casing into the secondary wellbore, and connect the upper end of the production casing with the upper end of the surface casing.

[0019] Optionally, a plurality of production casings are provided, the plurality of production casings are connected and coaxially arranged, a casing head is provided at the upper end of the uppermost production casing, and the uppermost production casing is connected to the surface casing through the casing head;

[0020] Step S32 specifically includes the following steps: using a lifting device to lift multiple production casings into the secondary wellbore, and using a casing head to connect the uppermost production casing with the surface casing.

[0021] Optionally, the drilling equipment includes a straight drilling tool and an inclined drilling tool, and step S2 specifically includes the following steps:

[0022] S21, drilling a second preset length in the vertical direction using a linear drilling tool to form a first straight well section;

[0023] S22, using an increasing-inclination drilling tool to drill into the lower end of the first straight well section to form an arc-shaped increasing-inclination section, wherein the upper end of the increasing-inclination section extends in a vertical direction, and the lower end of the increasing-inclination section extends in a preset direction;

[0024] S23, using a linear drilling tool to drill a third preset length from the lower end of the increasing inclination section along a preset direction to form a stable inclination well section;

[0025] S24, using an increasing-inclination drilling tool to drill into the lower end of the stable-inclination well section to form an arc-shaped curved descending section, wherein the upper end of the descending section extends in a preset direction and the lower end of the descending section extends in a vertical direction;

[0026] S25. Drill a fourth preset length in the vertical direction from the lower end of the descending section using a straight drilling tool to form a second vertical well section.

[0027] Optionally, step S5 may be followed by step S6, wherein a reaming drill is used to drill into the well wall of the third-opening wellbore to expand the diameter of the third-opening wellbore.

[0028] Optionally, step S4 specifically includes the following steps:

[0029] S41, injecting cement slurry between the wellbore wall and the production casing of the secondary wellbore;

[0030] S42. Apply pressure to the production casing using a pressure-increasing device until the pressure in the production casing reaches a preset pressure value. At the same time, the anchor is anchored to the wellbore wall of the secondary wellbore under the action of pressure.

[0031] Optionally, after step S42, the following steps are further included:

[0032] S43, using the lifting equipment to pull the production casing upward for multiple times until the hanging weight or elongation of the production casing meets the construction requirements;

[0033] S44, lowering the production casing using a lifting device, and installing casing head slips in the secondary wellbore before the lower end of the production casing moves to the lowest end of the secondary wellbore;

[0034] S45. Stop lowering the production casing until the casing head slips lock the production casing.

[0035] Optionally, before step S1, the method further includes step S0, using drilling equipment to drill a sixth preset length vertically from the ground to form an initial wellbore, and installing a guide tube in the initial wellbore;

[0036] In step S1, after the surface casing is lowered into an open wellbore, the upper end of the surface casing is connected to the conduit.

[0037] Optionally, step S1 specifically includes the following steps:

[0038] S11, using drilling equipment to drill a first preset length in a vertical direction to form an open wellbore;

[0039] S12, using a lifting device to lift the surface casing into an open wellbore;

[0040] S13, injecting cement slurry between the wellbore wall and the surface casing of the open wellbore;

[0041] S14. After a preset time, drilling fluid is injected into the surface casing, and the pressure value in the surface casing is monitored.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention provides a drilling method for injection and production wells in salt cavern gas storage. The diameter of the surface casing is no less than 508.0 mm, and the diameter of the production casing is no less than 339.7 mm. This allows the diameters of the primary and secondary wellbores to be increased accordingly, thereby increasing the volume of natural gas that can be injected and produced per unit time, accelerating the injection and production rate, and ensuring the efficiency of natural gas injection and production even when the salt cavern gas storage is buried at a deep depth. The secondary wellbores include a well section extending in a preset direction. This well section allows the upper and lower ends of the secondary wellbores to be located at different horizontal positions. Therefore, when an obstacle exists directly above the salt cavern gas storage, the upper end of the secondary wellbores can be located to one side of the obstacle in the horizontal direction, provided that the lower end of the secondary wellbores can extend to the salt layer of the salt cavern gas storage. This allows the injection and production wells to be smoothly constructed in the presence of ground obstacles, thereby reducing the impact of surface obstacles on the construction of the injection and production wells. The anchors, anchored to the wellbore wall under pressure, strengthen the connection between the production casing and the wellbore, secure the production casing in place within the secondary wellbore, and prevent movement and deformation, ensuring the safety and stability of the natural gas injection and production process. Compared to existing technologies, the drilling method for salt cavern gas storage injection and production wells provided by this invention lays the foundation for subsequent improvements in injection and production well cavity creation efficiency, natural gas injection and production rates, and salt mine resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A cross-sectional view of an injection-production well constructed using the drilling method for a salt cavern gas storage injection-production well provided by the present invention;

[0045] Figure 2 A first flow chart of the drilling method for a salt cavern gas storage injection and production well provided by the present invention;

[0046] Figure 3The second flow chart of the drilling method for the injection and production well of the salt cavern gas storage provided by the present invention

[0047] Figure 4 A schematic diagram of an anchor in a recovered state in a drilling method for a salt cavern gas storage injection and production well provided by the present invention;

[0048] Figure 5 This is a schematic diagram of an anchor in an anchored state for the drilling method for a salt cavern gas storage injection and production well provided by the present invention.

[0049] In the picture:

[0050] 100, second wellbore; 101, first vertical section; 102, increasing inclination section; 103, stable inclination section; 104, decreasing inclination section; 105, second vertical section; 200, third wellbore;

[0051] 1. Conduit; 2. Surface casing; 3. Production casing; 4. Anchor; 41. Anchor body; 42. Anchor claw; 43. Connector. DETAILED DESCRIPTION

[0052] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0053] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0054] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0055] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0056] like Figures 1 to 5 As shown, this embodiment provides a drilling method for injection and production wells in salt cavern gas storage, which ensures the safety and stability of natural gas injection and production, reduces the impact of surface obstacles on the construction of injection and production wells, and lays a foundation for improving the cavity creation efficiency of injection and production wells, the rate of natural gas injection and production, and the utilization rate of salt mine resources.

[0057] See Figure 1 and Figure 2 The injection and production wells include a first opening wellbore, a second opening wellbore 100 and a third opening wellbore 200, and a production casing 3 is installed in the second opening wellbore 100. The drilling method for the injection and production wells of the salt cavern gas storage includes the following steps:

[0058] S1. Drilling a first preset length in a vertical direction using drilling equipment to form an open wellbore, and running a surface casing 2 having a diameter of not less than 508.0 mm into the open wellbore;

[0059] S2. Using a drilling device, drilling a second preset length, a third preset length, and a fourth preset length in the vertical direction in sequence to form a second wellbore 100, wherein the preset direction is set at an angle to the vertical direction;

[0060] S3. Install an anchor 4 at the lower end of the production casing 3, lower the production casing 3 into the secondary wellbore 100, and connect the upper end of the production casing 3 to the surface casing 2. The diameter of the production casing 3 is not less than 339.7 mm.

[0061] S4, increasing the pressure in the production casing 3, and anchoring the anchor 4 to the wellbore wall of the secondary wellbore 100 under the action of pressure;

[0062] S5. Drilling a fifth preset length in the vertical direction from the lower end of the secondary wellbore 100 using drilling equipment to form the tertiary wellbore 200.

[0063] In the drilling method for a salt cavern gas storage injection and production well provided in this embodiment, the diameter of the surface casing 2 is no less than 508.0 mm, and the diameter of the production casing 3 is no less than 339.7 mm. This increases the diameters of the primary and secondary wellbores 100, thereby increasing the volume of natural gas that can be injected and produced per unit time, accelerating the rate of natural gas injection and production, and ensuring the efficiency of natural gas injection and production even when the salt cavern gas storage is buried at a deep depth. The secondary wellbores 100 include a well section extending along a preset direction. This well section allows the upper and lower ends of the secondary wellbores 100 to be located at different horizontal positions. Therefore, when an obstacle exists directly above the salt cavern gas storage, the upper end of the secondary wellbores 100 can be located to one side of the obstacle in the horizontal direction, provided that the lower end of the secondary wellbores 100 can extend to the salt layer of the salt cavern gas storage. This allows the injection and production wells to be smoothly constructed in the presence of surface obstacles, thereby reducing the impact of surface obstacles on the construction of the injection and production wells. Anchoring the anchor 4 to the wellbore under pressure, it can improve the strength of the connection between the production casing 3 and the wellbore, fix the production casing 3 in the secondary wellbore 100, prevent the production casing 3 from moving and deforming, and ensure the safety and stability of the natural gas injection and production process. Compared with the existing technology, the drilling method for injection and production wells in salt cavern gas storage provided in this embodiment lays the foundation for subsequently improving the cavity creation efficiency of injection and production wells, the injection and production rate of natural gas, and the utilization rate of salt mine resources.

[0064] Among them, the values of the first preset length, the second preset length, the third preset length, the fourth preset length and the fifth preset length are all determined according to the specific construction conditions and the test conditions before construction.

[0065] Furthermore, the production casing 3 includes a first section and a second section that are connected, the first section is made of carbon steel, and the second section is made of anti-corrosion material, the first section is located in the sandstone layer, and the second section is located in the salt rock layer, so that the production casing 3 has anti-corrosion performance while also reducing the production cost of the production casing 3.

[0066] Exemplarily, the second segment is made of 13Cr (chromium).

[0067] Optionally, see Figure 1 and Figure 3 Prior to step S1, the method further includes step S0, using drilling equipment to drill a sixth preset length vertically from the ground to form an initial wellbore, and installing a guide tube 1 in the initial wellbore. In step S1, after the surface casing 2 is lowered into the initial wellbore, the upper end of the surface casing 2 is connected to the guide tube 1. The guide tube 1 can reinforce the soft formation around the initial wellbore, ensuring that subsequent drilling equipment can be securely installed at the wellhead.

[0068] Specifically, when installing the guide tube 1, the guide tube 1 is first hoisted into the initial wellbore using a hoisting device; then, cement slurry is injected between the wellbore wall of the initial wellbore and the guide tube 1 to perform cementing operations; finally, after the cement slurry is allowed to solidify for a period of time and the solidification degree and strength of the cement slurry meet the requirements, step S1 is executed.

[0069] The value of the sixth preset length is determined according to the specific construction conditions. In this embodiment, the sixth preset length is 25m.

[0070] For example, the diameter of the conduit 1 is 720 mm, and the diameter of the surface casing 2 is 508 mm. In step S0, the conduit 1 with a diameter of 720 mm is hoisted into the initial wellbore, and the cement slurry is allowed to solidify for 12 hours.

[0071] Optionally, see Figure 1 and Figure 3 , step S1 specifically includes the following steps:

[0072] S11. Drilling a first preset length in a vertical direction using drilling equipment to form a wellbore.

[0073] S12, using a lifting device to lift the surface casing 2 into an open wellbore.

[0074] Specifically, after step S11 and before step S12, well cleaning and logging operations may be performed. The well cleaning operation can remove impurities such as drill cuttings and mud cake left in the wellbore during the drilling process, ensuring the smooth progress of subsequent logging operations and the lowering of the surface casing 2. Well logging operations can obtain parameters such as the resistivity, density, and neutron porosity of the formation, which are helpful for analyzing information such as the lithology and reservoir characteristics of the formation. The well cleaning and logging operations are both existing technologies in the art and will not be described in detail here.

[0075] S13, injecting cement slurry between the wellbore wall and the surface casing 2 to perform cementing operations. The cement slurry can completely cement and seal the annulus between the wellbore wall and the surface casing 2, effectively preventing the cross-flow of natural gas in the injection and production well, and ensuring the safety of the injection and production well.

[0076] S14, after the cementing has waited for a preset time, drilling fluid is injected into the surface casing 2, and the pressure value in the surface casing 2 is monitored. The preset time is the time for the cement slurry to wait for setting.

[0077] Specifically, after the cementing process has waited for a preset period of time, the cementing quality is tested to see if it meets the requirements. If so, the subsequent steps are performed. If not, the cementing quality is tested again after it meets the requirements. After the cementing quality meets the requirements, the casing head is installed on the surface casing 2. Subsequently, drilling fluid is injected into the surface casing 2 and the pressure inside the surface casing 2 is monitored. The pressure changes during the drilling fluid injection process to test the strength and sealing properties of the surface casing 2.

[0078] For example, when the buried depth of the salt mine is between 1000m and 2500m, in step S11, a drill bit with an outer diameter of 660.4mm is used to drill to 611m underground to form an open wellbore; in step S12, a surface casing 2 with a diameter of 508mm is lowered to 610m underground; in step S14, the preset time is 24 hours.

[0079] Optionally, see Figure 1 and Figure 3 The drilling equipment includes a straight drilling tool and an inclined drilling tool. Step S2 specifically includes the following steps:

[0080] S21, drilling a second preset length in the vertical direction using a linear drilling tool to form a first straight well section 101;

[0081] S22, using an increasing-inclination drilling tool to drill into the lower end of the first straight well section 101, forming an arc-shaped increasing-inclination section 102, wherein the upper end of the increasing-inclination section 102 extends in a vertical direction, and the lower end of the increasing-inclination section 102 extends in a preset direction;

[0082] S23, using a straight drilling tool to drill a third preset length from the lower end of the inclination increasing section 102 along a preset direction to form a stable inclination well section 103;

[0083] S24, using an increasing inclination drilling tool to drill into the lower end of the stable inclination well section 103, forming an arc-shaped curved descending section 104, wherein the upper end of the descending section 104 extends in a preset direction, and the lower end of the descending section 104 extends in a vertical direction;

[0084] S25 , using a straight drilling tool to drill a fourth preset length in the vertical direction from the lower end of the descending section 104 to form a second vertical well section 105 .

[0085] This construction method can precisely control the drilling path of the secondary wellbore 100 and flexibly cope with the drilling of injection and production wells under complex geological conditions. By using the inclination drilling tool in steps S22 and S24, the curvature of the secondary wellbore 100 in this section can be changed, thereby achieving a change in the extension direction of the secondary wellbore 100 and ensuring the smoothness of the direction change process.

[0086] For example, when the salt mine is buried at a depth between 1000m and 2500m, a secondary wellbore 100 is drilled using a drill bit with an outer diameter of 444.5mm. Specifically, the drill bit is used to drill vertically to 700m underground, forming a first straight well section 101. Subsequently, the drill bit is used to drill at a build-up rate of 2° / 30m to 966.61m underground, forming an increasing-inclination section 102. At this point, the angle between the preset direction and the vertical direction is 17.77°. Next, drilling continues in the preset direction until it reaches 1442.15m underground, forming a stable-inclination section 103. The drill bit is used to drill at a build-up rate of 1.5° / 30m to 1797.63m underground, forming a decreasing-inclination section 104. Finally, the drill bit is used to drill vertically to 2008.63m underground, forming a second vertical well section 105. In step S3, the production casing 3 with a diameter of 339.7 m is lowered to 2007.63 m underground.

[0087] In this embodiment, after step S25 and before step S3, well cleaning and logging operations need to be performed in the secondary wellbore 100. The specific processes are all existing technologies and will not be described again here.

[0088] Optionally, see Figure 1 、 Figure 4 and Figure 5 The anchor 4 includes an anchor body 41 and multiple anchor claws 42. Multiple anchor claws 42 are arranged along the extension direction and circumference of the anchor body 41. The anchor claws 42 are rotatably connected to the anchor body 41. The anchor claws 42 have a retracted state, parallel to the extension direction of the anchor body 41, and an anchored state, arranged at an angle to the extension direction of the anchor body 41. During step S3, when the production casing 3 is lowered into the secondary wellbore 100, the anchor claws 42 are in the retracted state. In step S4, the anchor claws 42 are opened from the retracted state to the anchored state under pressure and anchored into the wellbore 100. The provision of multiple anchor claws 42 strengthens the connection between the anchor 4 and the wellbore, ensuring the secure installation of the production casing 3 in the secondary wellbore 100 and improving the safety and stability of the natural gas injection and production process. During the lowering of the production casing 3, the anchor claws 42 are in the retracted state, preventing the anchor claws 42 from contacting the surface casing 2 and the wellbore wall, thereby preventing any impact on existing structures.

[0089] In this embodiment, refer to Figure 3 and Figure 4 The anchor body 41 is provided with a connecting piece 43, which is connected to the bottom end of the production casing 3. Step S3 specifically includes the following steps:

[0090] S31 . Install a connector 43 at the bottom end of the production casing 3 . The anchor body 41 is connected to the production casing 3 via the connector 43 .

[0091] S32 , lowering the production casing 3 into the secondary wellbore 100 , and connecting the upper end of the production casing 3 to the upper end of the surface casing 2 .

[0092] For example, the connector 43 is a coupling, and the diameter of the anchor body 41 is the same as the diameter of the production casing 3 , so that the anchor body 41 can be connected to the production casing 3 through the coupling.

[0093] Specifically, see Figure 1 Multiple production casings 3 are provided, and the multiple production casings 3 are connected and coaxially arranged. A casing head is provided at the upper end of the topmost production casing 3. The topmost production casing 3 is connected to the surface casing 2 via the casing head to ensure the secure connection between the production casing 3 and the surface casing 2. Step S32 specifically includes the following steps: using a lifting device to lift the multiple production casings 3 into the secondary wellbore 100, and using the casing head to connect the topmost production casing 3 to the surface casing 2.

[0094] Optionally, see Figure 1 and Figure 3 , step S4 specifically includes the following steps:

[0095] S41 . Inject cement slurry between the wellbore wall of the secondary wellbore 100 and the production casing 3 to perform cementing operations.

[0096] In this embodiment, the cement slurry used for the secondary wellbore 100 adopts a double-setting and double-density tough cement slurry system, that is, the leading slurry adopts a low-density tough cement slurry with a density of 1.50g / cm3 to 1.60g / cm3 and a thickening time of the cementing construction time plus 60 minutes, and the tailing slurry adopts a conventional density tough cement slurry with a density of 1.85g / cm3 to 1.95g / cm3 and a thickening time of the sum of the tailing slurry injection time, the plugging time, and the slurry replacement time plus 60 minutes.

[0097] S42. Pressure is applied to the production casing 3 using a pressurizing device until the pressure in the production casing 3 reaches a preset value, completing the impact and pressure holding operations on the production casing 3. Simultaneously, the anchor 4 is anchored to the wellbore 100 under the action of pressure. The pressure holding operation after impact and pressure holding is performed to a certain value to ensure that the cement slurry forms sufficient bonding strength between the production casing 3 and the wellbore, thereby facilitating the solidification of the cement slurry and its close bonding to the wellbore.

[0098] The preset pressure value is determined by the specific construction conditions and the test results before construction. In this embodiment, the preset pressure value is 10MPa to 15MPa.

[0099] S43. Lift the production casing 3 upward multiple times using a lifting device until the hanging weight or elongation of the production casing 3 meets the construction requirements. Lifting the production casing 3 helps the cement slurry form a uniform annulus between the production casing 3 and the wellbore wall, ensuring that the cement slurry can fully solidify and form a good cement ring. Furthermore, lifting the production casing 3 upward slowly over multiple times can avoid excessive disturbance of the cement slurry, which could affect the bonding between the cement slurry and the wellbore wall.

[0100] For example, the values of the hanging weight and the elongation are determined by the specific construction conditions and the test results before construction. In this embodiment, the lifting is stopped after the hanging weight reaches 220kN.

[0101] S44, lowering the production casing 3 using a lifting device, and installing a casing head slip in the secondary wellbore 100 before the lower end of the production casing 3 moves to the lowermost end of the secondary wellbore 100;

[0102] S45: Stop lowering the production casing 3 until the casing head slips lock the production casing 3.

[0103] The casing head slip is a device for fixing the position of the production casing 3 in the secondary wellbore 100 . After the casing head slip holds the production casing 3 tightly, the production casing 3 will not move in the secondary wellbore 100 .

[0104] After step S45, it is necessary to wait for a period of time (such as 72 hours) to test whether the cementing quality meets the requirements and whether the strength and sealing of the production casing 3 meet the requirements. The specific operation process is the same as that of the surface casing 2 and will not be repeated here.

[0105] Optionally, see Figure 1 and Figure 3 After step S5, step S6 is also included, in which a reaming drill is used to drill into the wall of the three-opening wellbore 200 to expand the diameter of the three-opening wellbore 200. This not only enables a large-sized cavity-making string of a salt cavern gas storage with a deeper burial depth to be smoothly lowered into the three-opening wellbore 200, thereby ensuring smooth construction of the salt cavern gas storage, but also enables natural gas to enter or flow out of the salt cavern gas storage more smoothly.

[0106] For example, when the buried depth of the salt mine is between 1000m and 2500m, in step S5, a drill bit with an outer diameter of 303.0mm is used to drill to 2432.63m underground to form a three-opening wellbore 200; in step S6, a reaming drill bit with an outer diameter of 340mm is used to expand the wellbore, and the expanded well section is in the range of 2018m to 2432.63m underground.

[0107] Furthermore, after step S6, well cleaning operations, well logging operations and wellbore air tightness testing operations need to be performed in the three-opened wellbore 200. The specific processes are all existing technologies and will not be repeated here.

[0108] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A drilling method for a salt cavern gas storage injection and production well, wherein the injection and production well comprises a first wellbore, a second wellbore (100) and a third wellbore (200), wherein a production casing (3) is installed in the second wellbore (100), and wherein: The drilling method for a salt cavern gas storage injection and production well comprises the following steps: S1. Drilling a first preset length in a vertical direction using drilling equipment to form the wellbore, and running a surface casing (2) having a diameter of not less than 508.0 mm into the wellbore; S2, using the drilling equipment to drill a second preset length in the vertical direction, a third preset length in the preset direction, and a fourth preset length in the vertical direction in sequence to form the second wellbore (100), wherein the preset direction is set at an angle to the vertical direction; S3, installing an anchor (4) at the lower end of the production casing (3), lowering the production casing (3) into the second wellbore (100), and connecting the upper end of the production casing (3) to the surface casing (2), wherein the diameter of the production casing (3) is not less than 339.7 mm; S4, increasing the pressure in the production casing (3), so that the anchor (4) is anchored to the wellbore wall of the secondary wellbore (100) under the action of the pressure; S5. Drilling a fifth preset length in a vertical direction from the lower end of the second wellbore (100) using the drilling equipment to form the third wellbore (200).

2. The drilling method for injection and production wells of salt cavern gas storage according to claim 1, characterized in that: The anchor (4) comprises an anchor body (41) and a plurality of flukes (42), wherein the plurality of flukes (42) are arranged along the extension direction of the anchor body (41) and the circumference of the anchor body (41), the flukes (42) are rotatably connected to the anchor body (41), and the flukes (42) have a retracted state parallel to the extension direction of the anchor body (41) and an anchored state at an angle to the extension direction of the anchor body (41); In step S3, during the process of lowering the production casing (3) into the secondary wellbore (100), the anchor claw (42) is in the retracted state. In step S4, the anchor claw (42) is opened from the retracted state to the anchored state under the action of pressure and anchored into the wellbore wall of the secondary wellbore (100).

3. The drilling method for injection and production wells of salt cavern gas storage according to claim 2, characterized in that: The anchor body (41) is provided with a connecting piece (43), and the connecting piece (43) is connected to the bottom end of the production casing (3); Step S3 specifically includes the following steps: S31, installing the connecting piece (43) at the bottom end of the production casing (3), and connecting the anchor body (41) to the production casing (3) through the connecting piece (43); S32, lowering the production casing (3) into the second wellbore (100), and connecting the upper end of the production casing (3) to the upper end of the surface casing (2).

4. The drilling method for injection and production wells of salt cavern gas storage according to claim 3, characterized in that: The production casing (3) is provided with a plurality of pieces, the plurality of production casings (3) are connected and coaxially arranged, a casing head is provided at the upper end of the production casing (3) located at the top, and the production casing (3) located at the top is connected to the surface casing (2) through the casing head; Step S32 specifically includes the following steps: using a lifting device to lift multiple production casings (3) into the second wellbore (100), and using the casing head to connect the production casing (3) located at the top with the surface casing (2).

5. The drilling method for injection and production wells of salt cavern gas storage according to claim 1, characterized in that: The drilling equipment includes a straight drilling tool and an inclined drilling tool, and step S2 specifically includes the following steps: S21, using the linear drilling tool to drill the second preset length in the vertical direction to form a first straight well section (101); S22, using the deflection increasing drilling tool to drill into the lower end of the first vertical well section (101), forming an arc-shaped curved deflection increasing section (102), wherein the upper end of the deflection increasing section (102) extends in a vertical direction, and the lower end of the deflection increasing section (102) extends in the preset direction; S23, using the linear drilling tool to drill the third preset length from the lower end of the inclination increasing section (102) along the preset direction to form a stable inclination well section (103); S24, using the increasing inclination drilling tool to drill into the lower end of the stable inclination well section (103), forming an arc-shaped curved descending section (104), wherein the upper end of the descending section (104) extends along the preset direction, and the lower end of the descending section (104) extends along the vertical direction; S25, using the linear drilling tool to drill the fourth preset length from the lower end of the descending section (104) in the vertical direction to form a second vertical well section (105).

6. The drilling method for injection and production wells of salt cavern gas storage according to claim 1, characterized in that: After step S5, the method further includes step S6, using a reaming drill to drill into the well wall of the three-opening wellbore (200) to expand the diameter of the three-opening wellbore (200).

7. The drilling method for injection and production wells of a salt cavern gas storage according to any one of claims 1 to 6, characterized in that: Step S4 specifically includes the following steps: S41, injecting cement slurry between the well wall of the second wellbore (100) and the production casing (3); S42, applying pressure to the production casing (3) using a pressure device until the pressure value in the production casing (3) increases to a preset pressure value, and at the same time, the anchor (4) is anchored to the wellbore wall of the second wellbore (100) under the action of pressure.

8. The drilling method for injection and production wells of salt cavern gas storage according to claim 7, characterized in that: After step S42, the following steps are also included: S43, using a lifting device to pull the production casing (3) upward for multiple times until the hanging weight or elongation of the production casing (3) reaches the construction requirement; S44, lowering the production casing (3) using the lifting device, and installing a casing head slip in the second wellbore (100) before the lower end of the production casing (3) moves to the lowermost end of the second wellbore (100); S45, until the casing head slips lock the production casing (3), stop lowering the production casing (3).

9. The drilling method for injection and production wells of a salt cavern gas storage according to any one of claims 1 to 6, characterized in that: Before step S1, the method further includes step S0, using the drilling equipment to drill a sixth preset length from the ground in a vertical direction to form an initial wellbore, and installing a guide tube (1) in the initial wellbore; In step S1, after the surface casing (2) is lowered into the first wellbore, the upper end of the surface casing (2) is connected to the conduit (1).

10. The drilling method for injection and production wells of a salt cavern gas storage according to any one of claims 1 to 6, characterized in that: Step S1 specifically includes the following steps: S11, using the drilling equipment to drill the first preset length in a vertical direction to form the wellbore; S12, using a lifting device to lift the surface casing (2) into the first wellbore; S13, injecting cement slurry between the wellbore wall of the first wellbore and the surface casing (2); S14: After a preset time, drilling fluid is injected into the surface casing (2), and the pressure value in the surface casing (2) is monitored.

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