Drilling device and drilling method for salt cavern gas storage

Abstract

The invention relates to the technical field of drilling of salt cavern energy storage engineering, in particular to a drilling device and method for a salt cavern gas storage. Comprising a drilling tool system, a drilling fluid adaptation system and an intelligent temperature control system which are integrated. The drilling tool system comprises a double-drill-bit assembly, and the double-drill-bit assembly comprises a main cutting drill bit and a finishing and expanding drill bit which are coaxially arranged up and down; the drilling fluid adaptation system comprises an anti-sloughing drilling fluid tank and a saturated brine tank; the intelligent temperature control system comprises a ground temperature monitoring module, a heating and heat preservation module and a PLC. By means of the integrated scheme of upper and lower double-drill-bit collaborative drilling, salt rock section saturated brine adaptation and ground temperature linkage temperature control, three core targets are achieved, the mechanical drilling speed is increased by 30% or above, the salt rock section diameter expansion rate is smaller than or equal to 3%, the non-salt rock section diameter shrinkage rate is smaller than or equal to 2%, meanwhile, the underground accident rate is reduced, and the drilling efficiency is improved. And efficient and stable technical support is provided for large-aperture multi-interlayer salt rock stratum drilling.

Description

Technical Field

[0001] This invention relates to the field of drilling technology for salt cavern energy storage projects, and in particular to a drilling device and drilling method for a salt cavern gas storage facility. Background Technology

[0002] Salt cavern compressed air energy storage is one of the core technologies for large-scale, long-term energy storage. The quality of well construction directly determines the storage capacity, sealing performance, and operational lifespan. Drilling large-diameter (300-500mm) injection-production wells / cavitation wells is a key aspect of salt cavern energy storage projects. However, multi-layered salt rock formations (including interbedded salt rock, shale, and sandstone) present significant challenges in drilling due to their large lithological differences, the easy dissolution and creep of salt rock, and the high water sensitivity of non-salt rock.

[0003] Early salt cavern drilling technology followed conventional oil and gas drilling approaches, employing a single drill bit for large-diameter, single-pass drilling, using ordinary fresh water or low-concentration brine drilling fluid. This resulted in low efficiency and poor wellbore stability. With the large-scale development of salt cavern energy storage projects, the industry gradually optimized drilling fluid systems, attempting to use saturated brine to inhibit salt rock dissolution. However, this did not solve the problems of high single-bit cutting load and salt rock creep enlargement caused by the mismatch between drilling fluid temperature and ground temperature. In recent years, drilling large-diameter, multi-layered salt rock formations has faced a bottleneck where efficiency and wellbore stability are difficult to balance, urgently requiring targeted innovation in drilling processes and adaptable technologies. Summary of the Invention

[0004] The present invention aims to overcome the defects of the prior art and provide a drilling device and drilling method for salt cavern gas storage, which helps to improve drilling efficiency and wellbore stability.

[0005] This invention provides a drilling device for a salt cavern gas storage facility, comprising a drilling tool system, a drilling fluid adaptation system, and an intelligent temperature control system, with the three systems integrated into one unit; The drilling tool system includes a dual-drill-bit assembly, which includes a main cutting drill bit and a dressing and reaming drill bit arranged coaxially. The main cutting drill bit and the dressing and reaming drill bit are connected by a connecting rod. The drilling fluid adaptation system includes a saturated brine tank and an anti-collapse drilling fluid tank, which are connected to a three-way switching valve via pipelines. The intelligent temperature control system includes a ground temperature monitoring module, a heating and insulation module, and a PLC controller. The detection end of the ground temperature monitoring module is located at the front end of the dressing and enlarging drill bit. The heating and insulation module is located outside the saturated brine tank. The PLC controller is connected to the ground temperature monitoring module and the heating and insulation module.

[0006] Furthermore, the main cutting drill bit adopts PDC composite cutting teeth with a claw-toe tooth shape and a diameter 10-15mm smaller than the target hole diameter; the dressing and enlarging drill bit adopts a retractable blade structure, and the diameter of the blade after opening is consistent with the target hole diameter, and the surface of the blade is provided with a wear-resistant alloy layer.

[0007] Furthermore, both ends of the connecting rod are double-fixed to the main cutting drill bit and the dressing and expanding drill bit using threads and pins. The connecting rod can withstand a torque of ≥3000 N·m and a pressure of ≥60 MPa. The main cutting drill bit and the dressing and expanding drill bit are respectively provided with a centralizer on the side near the drill rod.

[0008] Furthermore, the Cl of the saturated brine in the saturated brine tank - Concentration ≥ 1.89 × 10 5 mg / L, with the addition of 0.5%-1% salt recrystallization inhibitor and 0.3%-0.5% lubricant, resulting in a density of 1.2-1.3 g / cm³. 3 The viscosity is 20-30 mPa·s; the anti-collapse drilling fluid in the anti-collapse drilling fluid tank is composed of potassium-based polyamine, aluminum complex plugging agent, and lubricant, with a density of 1.1-1.2 g / cm³. 3 The viscosity is 25-35 mPa·s.

[0009] Furthermore, the drilling fluid adaptation system is equipped with a circulation purification module with a purification accuracy of ≤20μm, which is used to circulate and purify the saturated brine in the saturated brine tank and the anti-collapse drilling fluid in the anti-collapse drilling fluid tank.

[0010] Furthermore, the ground temperature monitoring module uses a drilling temperature measurement sensor with a measurement range of 0-150℃, an accuracy of ±0.5℃, a sampling frequency of 10Hz, and transmits downhole ground temperature data in real time; the heating and insulation module uses an electric heating jacket.

[0011] This invention provides a drilling method for a salt cavern gas storage facility, employing the aforementioned drilling system, and includes the following steps: S1. Preliminary Preparation Stage The distribution of interlayers was clarified by 3D seismic and well logging data, the salt rock section and the non-salt rock section were divided, the geothermal gradient was determined, the dual drill bit assembly was connected to the drill pipe and lowered into the wellhead; S2. Drilling stage in non-salt rock section Start the drilling pump to circulate the anti-collapse drilling fluid, and the main cutting bit and the dressing and enlarging bit work together to cut; at the same time, monitor the well diameter and well inclination data in real time to ensure that the diameter reduction rate is ≤2% and the well inclination is ≤0.5° / 100m. When the diameter reduction trend is observed, increase the viscosity and flow rate of the anti-collapse drilling fluid; identify the salt rock formation through drilling data and prepare to switch the drilling fluid. S3. Drilling and Temperature Control Stage in Salt Rock Section The wellbore is quickly switched to saturated brine using a three-way switching valve and circulated for 10-15 minutes to stabilize it. The PLC controller adjusts the power of the heating and insulation module based on the real-time ground temperature data transmitted by the ground temperature monitoring module, adjusting the temperature of the saturated brine to a difference of ≤5℃ from the ground temperature. The main cutting drill bit and the dressing and enlarging drill bit work together for cutting. The main cutting drill bit breaks the rock, while the dressing and enlarging drill bit trims the well wall to ensure that the enlargement rate of the salt rock section is ≤3%. S4. Well Completion Stabilization Stage: For salt rock sections, circulate saturated brine for ≥30 minutes and for non-salt rock sections, circulate anti-collapse drilling fluid for ≥45 minutes. Test the wellbore quality and anti-collapse drilling fluid performance to ensure that the design requirements are met before pulling out the dual drill bit assembly and maintaining the equipment.

[0012] Furthermore, the drilling parameters set in step S2 are: drilling pressure 25-40kN, rotation speed 50-70r / min, and displacement 30-40L / s.

[0013] Furthermore, the drilling parameters set in step S3 are: drilling pressure 30-50kN, rotation speed 60-80r / min, and displacement 35-45L / s.

[0014] Furthermore, step S2 involves interlayer transition treatment: if the thickness of the salt rock section is <0.5m, maintain saturated brine circulation and reduce drilling pressure to 20-30kN; if the thickness of the salt rock section is ≥0.5m, switch back to anti-collapse drilling fluid and drill according to the parameters for non-salt rock sections.

[0015] In summary, compared with the prior art, the present invention has the following advantages: I. Significantly Improved Drilling Efficiency: This invention utilizes a main cutting drill bit and a dressing and enlarging drill bit arranged coaxially to work together to distribute the cutting load of large-diameter holes, achieving a mechanical drilling speed of 7-9 m / h, which is more than 30% higher than the traditional single-drill-bit technology, and shortening the drilling cycle of a single well by 20%-25%.

[0016] II. Significantly Improved Wellbore Stability: The drilling fluid adaptation system set up in this invention uses anti-collapse drilling fluid and saturated brine. In the salt rock section, saturated brine is used to inhibit dissolution, and an intelligent temperature control system is used to reduce creep, with an enlargement rate of ≤3%. In the non-salt rock section, anti-collapse drilling fluid is maintained, with a reduction rate of ≤2%, and the regularity of the wellbore is improved by 60%.

[0017] 3. Significantly reduced downhole accident rate: This invention solves the problems of wellbore enlargement and reduction, and reduces the incidence of accidents such as stuck drill bit and mud bag to ≤0.2 times / km, which is 75% lower than the existing technology.

[0018] IV. Strong adaptability and compatibility: The dual-bit design of the main cutting drill bit and the dressing and enlarging drill bit in this invention is suitable for target hole diameters of 300-500mm. The switching mechanism of saturated brine and anti-collapse drilling fluid is suitable for 2-5 layers of non-salt rock interlayers. The temperature control range covers ground temperatures of 40-120℃ and is compatible with salt cavern engineering at different depths.

[0019] V. Reduced construction costs: The technical solution provided by this invention improves efficiency and reduces accidents, leading to a 15%-20% reduction in single-well drilling costs. Furthermore, the saturated brine can be recycled, further reducing material costs. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the drilling device in an embodiment of the present invention.

[0022] Explanation of reference numerals in the attached diagram: 1-Main cutting drill bit; 2-Dressing and enlarging drill bit; 3-Connecting rod; 4-Center; 5-Saturated brine tank; 6-Anti-collapse drilling fluid tank; 7-Three-way switching valve; 8-Electric heating jacket; 9-Drilling temperature sensor; 10-PLC controller; 11-Drill pipe. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Example A drilling device for a salt cavern gas storage facility, such as Figure 1 As shown, the system integrates three components: a drilling tool system, a drilling fluid compatibility system, and an intelligent temperature control system. Details are as follows: I. Drilling Tool System The drilling tool system includes a dual-drill-bit assembly, comprising a main cutting drill bit 1 and a dressing and reaming drill bit 2, coaxially arranged. The main cutting drill bit 1 and the dressing and reaming drill bit 2 are connected by a connecting rod 3, which is made of a rigid material. The system employs a coaxial layout of the upper main cutting drill bit and the lower dressing and reaming drill bit, fixed by rigid connecting rods (500-800mm spacing), and is suitable for target hole diameters of 300-500m.

[0027] The main cutting drill bit 1 uses PDC composite cutting teeth with a claw-toe tooth shape. The tooth arrangement is differentiated between salt rock and non-salt rock interlayers, with a high tooth density in the salt rock section and a thicker wear-resistant coating on the tooth surface in the non-salt rock section. The tooth density in the salt rock section is 2.5 teeth / cm². 2 The circumferential spacing between adjacent cutting teeth is 9 mm, and the axial spacing is 5.5 mm, which is suitable for the characteristics of salt rock with high plasticity and fine rock cuttings, and disperses the cutting load; the tooth density in the non-salt rock section is 1.2 teeth / cm³. 2 The circumferential spacing between adjacent cutting teeth is 13mm, and the axial spacing is 8.5mm. The working surfaces of the cutting teeth in the non-salt rock section are covered with a TiN wear-resistant coating with a thickness of 10μm (compared to a conventional coating thickness of 4μm) and a hardness of HV2000. This coating is prepared using PVD (physical vapor deposition) technology, enhancing its resistance to the high abrasiveness of non-salt rocks. The main cutting drill bit 1 has a diameter 10-15mm smaller than the target hole diameter and undertakes the primary rock-breaking task.

[0028] The dressing and enlarging drill bit 2 adopts a retractable blade structure. When the blade is opened, its diameter is consistent with the target hole diameter. The blade surface is provided with a wear-resistant alloy layer, which is responsible for dressing the well wall, calibrating the hole diameter, and ensuring the wellbore is regular.

[0029] The connecting rod 3 has a double-layer tube structure. The outer layer is responsible for transmitting torque and is made of high-strength steel pipe. The inner layer is responsible for conveying drilling fluid and is made of thin-walled pipe or central pipe. Both ends are double-fixed to the main cutting drill bit 1 and the dressing and enlarging drill bit 2 by threads and pins. It can withstand torque ≥3000 N·m and pressure ≥60 MPa to ensure the coordinated operation of the two drill bits and smooth flow of drilling fluid.

[0030] Centralizers 4 are respectively installed on the side of the main cutting drill bit 1 and the dressing and enlarging drill bit 2 near the drill pipe 11. One centralizer 4 is sleeved on the outside of the connecting rod 3, and the other centralizer 4 is sleeved on the outside of the drill pipe 11. The centralizers 4 are elastic centralizers made of polyurethane, with an extension diameter adapted to the wellbore size to ensure that the drill string is centered and the well deviation control accuracy is ≤0.5° / 100m.

[0031] II. Drilling Fluid Adaptation System The drilling fluid adaptation system includes 5 saturated brine tanks (50m³ capacity). 3 ), 6 anti-collapse drilling fluid tanks (capacity 50m³) 3 The saturated brine tank 5 and the anti-collapse drilling fluid tank 6 are both connected to the three-way switching valve 7 via pipelines. The three-way switching valve 7 has a response time of ≤5s and can quickly switch the drilling fluid system according to the formation type.

[0032] The saturated brine in saturated brine tank 5 is used in the salt rock section, Cl - Concentration ≥ 1.89 × 10 5 mg / L, with the addition of 0.5%-1% salt recrystallization inhibitor and 0.3%-0.5% lubricant, the density is 1.2-1.3 g / cm³. 3 The viscosity is 20-30 mPa·s, which inhibits the dissolution and creep of salt rocks. For example, the following scheme can be referred to: saturated brine can be of the NaCl type, the added salt recrystallization inhibitor can be PESA, HEDP or HPMA, and the lubricant can be sodium petroleum sulfonate or fatty acid amide.

[0033] The anti-collapse drilling fluid in anti-collapse drilling fluid tank 6 is used in non-salt rock sections. It consists of potassium-based polyamine, aluminum complex plugging agent, and lubricant, with a density of 1.1-1.2 g / cm³. 3 The viscosity is 25-35 mPa·s, which inhibits the hydration and expansion of mudstone and shale. For example, the following scheme can be used (by mass volume concentration): 1000 parts water, 30-40 g / L potassium-based polyamine, 18-25 g / L aluminum complex plugging agent, and 10-15 g / L lubricant. The lubricant can be fatty acid amide or sulfurized olefin.

[0034] The drilling fluid adaptation system is also equipped with a circulation purification module with a purification accuracy of ≤20μm, ensuring stable drilling fluid performance and preventing rock cuttings from affecting drilling and wellbore stability. The circulation purification module is a conventional technology in this field, including a vibrating screen, desander, desilter, sand pump, desilter pump, and transition tank. These components are connected in series through pipelines to form a closed-loop purification system. The drilling fluid containing rock cuttings returned from the wellhead is sequentially screened by the vibrating screen, transported by the sand pump to the desander for desandering, transferred to the transition tank, and then transported by the desilter pump to the desilter for fine separation before flowing into the saturated brine tank 5 or the anti-collapse drilling fluid tank 6. The solid residues discharged by the desander and desilter are returned to the vibrating screen for secondary filtration.

[0035] III. Intelligent Temperature Control System The intelligent temperature control system includes a ground temperature monitoring module, a heating and insulation module, and a PLC controller 10. The ground temperature monitoring module uses a drilling temperature sensor 9, whose detection end is installed at the front end of the dressing and enlarging drill bit 2. Its measurement range is 0-150℃, with an accuracy of ±0.5℃ and a sampling frequency of 10Hz, transmitting downhole ground temperature data in real time.

[0036] The heating and insulation module uses an electric heating jacket 8, which is wrapped around the outside of the saturated brine tank 5. The electric heating jacket 8 has a power of 50-100kW and a heating rate of 5-10℃ / h, and can adjust the temperature of the saturated brine to a difference of ≤5℃ from the ground temperature. At the same time, the pipelines transporting the saturated brine are all equipped with rock wool insulation layers.

[0037] The PLC controller 10 receives data from the drilling temperature sensor 9, automatically adjusts the power of the electric heating jacket 8, and achieves dynamic adaptation between the saturated brine temperature and the ground temperature, while displaying the real-time temperature and adjustment status.

[0038] A drilling method for a salt cavern gas storage facility, using the aforementioned drilling device, is described in the following steps: S1. Preliminary Preparation Stage Geological preprocessing: Using 3D seismic and well logging data, the distribution of interlayers (thickness, depth, lithology) is clarified, drilling areas are divided into salt rock sections and non-salt rock sections, and the geothermal gradient distribution is determined; Equipment commissioning: Assemble the dual drill bit assembly and test the torque transmission performance of the connecting rod 3 and the stability of the drill bit operation; calibrate the downhole temperature sensor 9, the electric heating jacket 8 and the PCL controller 10 to ensure the temperature regulation accuracy is ≤ ±0.5℃; prepare the anti-collapse drilling fluid and saturated brine and verify the response speed of the three-way switching valve 7. Drill string lowering: Connect the dual drill bit assembly, the temperature sensor 9 while drilling, and the drill pipe 11, and slowly lower them into the wellhead to ensure that the centralizer 4 extends normally and the drilling fluid flow path is unobstructed.

[0039] S2. Drilling stage in non-salt rock section Start drilling: Turn on the drilling pump, circulate anti-collapse drilling fluid, and set the drilling parameters: drilling pressure 25-40kN, rotation speed 50-70r / min, displacement 30-40L / s. The main cutting drill bit 1 and the dressing and enlarging drill bit 2 work together to cut the non-salt rock formation. Wellbore monitoring: Real-time acquisition of drilling pressure, torque, and wellbore data to ensure that the diameter reduction rate of non-salt rock sections is ≤2% and the well inclination is ≤0.5° / 100m. If a diameter reduction trend occurs, the viscosity and flow rate of the anti-collapse drilling fluid should be appropriately increased. Formation identification: When drilling data shows that the lithology changes to salt rock with resistivity ≥100Ω·m and density ≤2.2g / cm³, the formation is identified. 3 Prepare to switch drilling fluid.

[0040] S3. Drilling and Temperature Control Stage in Salt Rock Section Drilling fluid switching: Quickly switch to saturated brine using the three-way switching valve 7. Maintain anti-collapse drilling fluid circulation during the switching process to prevent wellbore collapse. After the switching is completed, maintain stable circulation for 10-15 minutes. Temperature regulation: Based on the ground temperature data transmitted by the drilling temperature sensor 9, the PLC controller 10 automatically starts the electric heating jacket 8 to adjust the temperature of the saturated brine to a difference of ≤5℃ from the ground temperature, and continuously monitors temperature changes and dynamically fine-tunes the heating power. Parameter optimization: Set drilling parameters for the salt rock section: drilling pressure 30-50kN, rotation speed 60-80r / min, displacement 35-45L / s, main cutting bit 1 and dressing and enlarging bit 2 work together to cut, main cutting bit 1 breaks the rock, dressing and enlarging bit 2 trims the well wall, ensuring that the enlargement rate of the salt rock section is ≤3%.

[0041] Interlayer transition treatment: If a thin interlayer with a thickness of <0.5m is encountered in the salt rock section, maintain saturated brine circulation and appropriately reduce the drilling pressure (20-30kN); if the interlayer thickness is ≥0.5m, switch back to anti-collapse drilling fluid, drill according to the parameters for non-salt rock sections, and switch back to saturated brine and adjust the temperature after passing through the interlayer.

[0042] S4. Well Completion Stabilization Stage Wellbore dressing: After drilling to the target depth, the wellbore is dressed using a slow tripping and segmented circulation method. Saturated brine is circulated for ≥30 minutes in the salt rock section and anti-collapse drilling fluid is circulated for ≥45 minutes in the non-salt rock section to remove residual rock cuttings in the well. Performance testing: The wellbore quality is tested using a caliper to ensure that the enlargement rate of the salt rock section is ≤3%, the reduction rate of the non-salt rock section is ≤2%, and the well inclination is ≤0.5° / 100m; the performance degradation of the drilling fluid is tested, and the feasibility of recycling is evaluated. Drill bit retrieval: Smoothly retrieve the dual drill bit assembly and drill pipe 11, clean residual rock cuttings and salt scale from the drill bit cutting teeth, and perform equipment maintenance.

[0043] The core parameters set in the above drilling method are shown in Table 1.

[0044] Table 1 Core Parameter Specifications

[0045] Important considerations for implementing the above drilling method: 1. Before the dual drill bit assembly is lowered into the well, a ground bench test must be conducted to ensure that there is no vibration or leakage under maximum drilling pressure and rotation speed, and that the connecting rod has a torque bearing capacity of ≥3000 N·m.

[0046] 2. When switching drilling fluids, a gradient transition method should be adopted. First, the flow rate of the anti-collapse drilling fluid should be reduced to 20-25 L / s, and then gradually increased to the set flow rate of the salt rock section after switching to avoid the system sudden change leading to wellbore instability.

[0047] 3. During drilling in the salt rock section, the saturated brine concentration should be checked every 100m. If Cl... - Concentration below 1.89 × 10 5 mg / L, timely replenishment of industrial salt to ensure inhibitory effect.

[0048] 4. The intelligent temperature control system should be equipped with a backup power supply to avoid a sudden drop in the temperature of the saturated brine due to power failure, which could cause creep expansion of the salt rock. During the heating process, the viscosity of the brine should be monitored in real time. If the viscosity exceeds 30 mPa·s, lubricant should be added appropriately to adjust it.

[0049] The key points of the technical solution provided by this invention are as follows: I. Coordinated layout of upper and lower dual drill bits: The design adopts a coaxial dual drill bit design for main cutting and dressing and enlarging, which disperses the cutting load of large-diameter holes and improves rock breaking efficiency and wellbore regularity.

[0050] II. Adaptation Mechanism of Saturated Brine in Salt Rock Section: Through High Concentration Cl - It inhibits salt rock dissolution, reduces salt rock creep when used with a dedicated inhibitor, and is compatible with rapid switching of anti-collapse drilling fluids in non-salt rock sections.

[0051] III. Ground temperature linkage temperature control technology: The ground temperature is monitored while drilling, and the temperature of the saturated brine is adjusted in real time to keep the temperature difference between the drilling fluid and the ground ≤5℃, thereby reducing the enlargement of the salt rock caused by thermal stress.

[0052] IV. Integrated Collaborative Control Logic: Integrates drilling tools, drilling fluid switching, and temperature control systems to achieve a coordinated response of formation identification, drill bit cutting, drilling fluid adaptation, and temperature regulation.

[0053] The technical solution provided by this invention has the following advantages: I. Significantly improved drilling efficiency: The upper and lower drill bits work together to cut, dispersing the cutting load of large-diameter holes, and the mechanical drilling speed reaches 7-9 m / h, which is more than 30% higher than the traditional single drill bit technology, and the drilling cycle of a single well is shortened by 20%-25%.

[0054] II. Significantly improved wellbore stability: Saturated brine is used to inhibit dissolution in salt rock sections, and temperature control is used to reduce creep, with an enlargement rate of ≤3%; high-quality anti-collapse drilling fluid is maintained in non-salt rock sections, with a reduction rate of ≤2% and a 60% improvement in wellbore regularity.

[0055] 3. Significantly reduced downhole accident rate: The problems of wellbore enlargement and reduction have been solved, and the incidence of accidents such as stuck drill bit and mud bag has been reduced to ≤0.2 times / km, which is 75% lower than existing technologies.

[0056] IV. Strong adaptability and compatibility: The multi-bit structure is suitable for target hole diameters of 300-500mm, the saturated brine + anti-collapse drilling fluid switching mechanism is suitable for 2-5 layers of non-salt rock interlayers, the temperature control range covers ground temperatures of 40-120℃, and it is compatible with salt cavern projects of different depths.

[0057] V. Reduced construction costs: Improved efficiency and fewer accidents lead to a 15%-20% reduction in single-well drilling costs, and saturated brine can be recycled, further reducing material costs.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A drilling device for a salt cavern gas storage facility, characterized in that, It includes a drilling tool system, a drilling fluid adaptation system, and an intelligent temperature control system, all three of which are integrated into one system. The drilling tool system includes a dual-drill-bit assembly, which includes a main cutting drill bit (1) and a dressing and enlarging drill bit (2) arranged coaxially. The main cutting drill bit (1) and the dressing and enlarging drill bit (2) are connected by a connecting rod (3). The drilling fluid adaptation system includes a saturated brine tank (5) and an anti-collapse drilling fluid tank (6), which are connected to a three-way switching valve (7) via pipelines. The intelligent temperature control system includes a ground temperature monitoring module, a heating and insulation module, and a PLC controller (10). The detection end of the ground temperature monitoring module is located at the front end of the dressing and enlarging drill bit (2). The heating and insulation module is located outside the saturated brine tank (5). The PLC controller (10) is connected to the ground temperature monitoring module and the heating and insulation module.

2. The drilling device according to claim 1, characterized in that, The main cutting drill bit (1) adopts PDC composite cutting teeth with a claw-toe tooth shape and a diameter 10-15mm smaller than the target hole diameter; the dressing and enlarging drill bit (2) adopts a telescopic blade structure, and the diameter of the blade after it is opened is consistent with the target hole diameter. The blade surface is provided with a wear-resistant alloy layer.

3. The drilling device according to claim 1, characterized in that, The connecting rod (3) is fixed to the main cutting drill bit (1) and the dressing and expanding drill bit (2) by both ends using threads and pins. The connecting rod (3) can withstand a torque of ≥3000 N·m and a pressure of ≥60 MPa. The main cutting drill bit (1) and the dressing and expanding drill bit (2) are respectively provided with a stabilizer (4) on the side near the drill rod.

4. The drilling device according to claim 1, characterized in that, The Cl of the saturated brine in the saturated brine tank (5) - Concentration ≥ 1.89 × 10 5 mg / L, with the addition of 0.5%-1% salt recrystallization inhibitor and 0.3%-0.5% lubricant, resulting in a density of 1.2-1.3 g / cm³. 3 The viscosity is 20-30 mPa·s; the anti-collapse drilling fluid in the anti-collapse drilling fluid tank (6) is composed of potassium-based polyamine, aluminum complex plugging agent, and lubricant, with a density of 1.1-1.2 g / cm³. 3 Its viscosity is 25-35 mPa·s.

5. The drilling device according to claim 1, characterized in that, The drilling fluid adaptation system is equipped with a circulation purification module with a purification accuracy of ≤20μm, which is used to circulate and purify the saturated brine in the saturated brine tank (5) and the anti-collapse drilling fluid in the anti-collapse drilling fluid tank (6).

6. The drilling apparatus according to claim 1, characterized in that, The ground temperature monitoring module uses a drilling temperature sensor (9), with a measurement range of 0-150℃, an accuracy of ±0.5℃, a sampling frequency of 10Hz, and real-time transmission of downhole ground temperature data; the heating and insulation module uses an electric heating jacket (8).

7. A drilling method for a salt cavern gas storage facility, characterized in that, Based on the drilling apparatus according to any one of claims 1-6, the method includes the following steps: S1. Preliminary Preparation Stage The distribution of interlayers was clarified by 3D seismic and well logging data, the salt rock section and the non-salt rock section were divided, the geothermal gradient was determined, the dual drill bit assembly was connected to the drill pipe and lowered into the wellhead; S2. Drilling stage in non-salt rock section Start the drilling pump to circulate the anti-collapse drilling fluid, and the main cutting bit and the dressing and enlarging bit work together to cut; at the same time, monitor the well diameter and well inclination data in real time to ensure that the diameter reduction rate is ≤2% and the well inclination is ≤0.5° / 100m. When the diameter reduction trend is observed, increase the viscosity and flow rate of the anti-collapse drilling fluid; identify the salt rock formation through drilling data and prepare to switch the drilling fluid. S3. Drilling and Temperature Control Stage in Salt Rock Section The wellbore is quickly switched to saturated brine using a three-way switching valve and circulated for 10-15 minutes to stabilize it. The PLC controller adjusts the power of the heating and insulation module based on the real-time ground temperature data transmitted by the ground temperature monitoring module, adjusting the temperature of the saturated brine to a difference of ≤5℃ from the ground temperature. The main cutting drill bit and the dressing and enlarging drill bit work together for cutting. The main cutting drill bit breaks the rock, while the dressing and enlarging drill bit trims the well wall to ensure that the enlargement rate of the salt rock section is ≤3%. S4. Well Completion Stabilization Stage: For salt rock sections, circulate saturated brine for ≥30 minutes and for non-salt rock sections, circulate anti-collapse drilling fluid for ≥45 minutes. Test the wellbore quality and anti-collapse drilling fluid performance to ensure that the design requirements are met before pulling out the dual drill bit assembly and maintaining the equipment.

8. The drilling method according to claim 7, characterized in that, The drilling parameters set in step S2 are: drilling pressure 25-40kN, rotation speed 50-70r / min, and displacement 30-40L / s.

9. The drilling method according to claim 7, characterized in that, The drilling parameters set in step S3 are: drilling pressure 30-50kN, rotation speed 60-80r / min, and displacement 35-45L / s.

10. The drilling method according to claim 8, characterized in that, Step S2 involves interlayer transition treatment: if the thickness of the salt rock section is <0.5m, maintain saturated brine circulation and reduce drilling pressure to 20-30kN; if the thickness of the salt rock section is ≥0.5m, switch back to anti-collapse drilling fluid and drill according to the parameters for non-salt rock sections.

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