Shale oil and gas horizontal well anti-burrowing drilling string and multi-block formation unblocking technology

Abstract

This invention discloses a drilling string for preventing burial in shale oil and gas horizontal wells and a process for unblocking in multi-block formations. From bottom to top, the string consists of a PDC drill bit, a rotary directional instrument, a burial prevention torque clutch, an energy storage device, and drilling tools. The energy storage device includes: an upper energy storage connector; an outer cylinder, the lower end of which is screwed to an intermediate cylinder and transmits torque to the intermediate cylinder; an intermediate cylinder, the lower part of which has an inner spiral groove that transmits torque to a drive shaft; a drive shaft, the outer periphery of which has an outer spiral that forms a helical pair with the inner spiral groove of the intermediate cylinder, the lower end of which is screwed to the drill bit; a piston, located in the lower inner cavity of the outer cylinder, the lower end of which is screwed to the upper end of the drive shaft; an inner sealing sleeve, the upper end of which is screwed into the lower inner threaded hole of the upper energy storage connector, and the lower end inserted into the central hole of the piston and capable of axial sliding; and multiple sets of butterfly springs in the annular space between the outer cylinder and the inner sealing sleeve, supporting the lower end face of the upper energy storage connector and the upper end face of the piston. This design prevents the drilling tools from being buried and facilitates unblocking.

Description

Technical Field

[0001] This invention relates to a horizontal well drilling string, and more particularly to a shale oil and gas horizontal well anti-burrowing drilling string. This invention also relates to a multi-block formation unblocking process for an anti-burrowing drilling string for shale oil and gas horizontal wells, belonging to the field of petroleum drilling technology. Background Technology

[0002] Deep shale oil and gas reservoirs in China are typically buried at depths of ≥3500m. Drilling in the target layer generally employs Ф215.9mm drill bits in conjunction with rotary steerable drilling instruments. Rotary steerable drilling systems offer many advantages, effectively increasing mechanical drilling speed, enabling real-time wellbore trajectory control, improving wellbore quality, and reducing overall drilling costs. However, the instruments themselves have large outer diameters and high rigidity, making them highly susceptible to sticking due to formation rockfall. The complex formations and downhole conditions in my country's deep shale oil and gas wells pose significant challenges to exploration and development. During horizontal well drilling in the Longmaxi Formation of shale gas in southern Sichuan, complex drilling conditions such as wellbore instability, severe rockfall, and frequent sticking have been encountered. From 2019 to 2021, CNPC and Sinopec had 59 rotary steerable drilling instruments stuck in wells during shale gas drilling in southern Sichuan, a sticking rate of 9.75%. Rotary steerable drilling instruments are high-precision products with extremely high costs; their sticking results in substantial losses. In complex rotary steerable wells where the well is stuck, stuck pipe accidents all occur at the rotary steerable position in the horizontal section (outer diameter Ф212mm), mainly due to shale rock falling and causing the pipe to become stuck. After the rotary steerable instrument in many shale gas horizontal wells became stuck, in addition to the drill string being unable to move freely, the drilling fluid circulation and pump pressure were normal. Once the rotary steerable instrument becomes stuck and the well is buried, the losses are huge.

[0003] Furthermore, abnormal torque fluctuations during drilling can easily lead to drill string self-excited vibration, drill string breakage, and screw drill string stagnation, resulting in frequent drill string lifting and pump pressure fluctuations, thus affecting drilling efficiency. When encountering gravel layers or formations with high hardness and poor stability, severe drill skipping can occur, causing significant damage to the drill bit and drill string.

[0004] Currently, shale dissolving agents have been developed on-site to address the structural strength of shale based on the characteristics of the formation's lithology. However, after the rotary steerable drilling tool gets stuck, the time required for the application of unsticking agents or shale corrosives, their introduction into the well, and the dissolution of loose material generally takes 3-4 days. During this period, the drill string cannot move or rotate freely. During drilling fluid circulation, solid phases gradually deposit on the lower wellbore wall above the stuck point in the horizontal section. Alternatively, prolonged circulation with the drill string stationary prevents the effective upward return of wellbore cuttings and small-sized loose material from being agitated by the drill string. As a result, most of these material gradually spreads and accumulates between the drill pipe and the lower wellbore wall, causing the lower side of the drill pipe in the horizontal section to become gradually buried, leading to more drill string getting stuck and increasing the difficulty of subsequent unsticking.

[0005] In the exploration and development of unconventional shale oil and gas wells, near-bit monitoring of formation gamma values ​​is often used in horizontal well sections to ensure the maximum acquisition of high-quality carbonaceous mudstone and shale during directional rotary drilling, aiming to maximize engineering, geological, and economic benefits. Taking the drilling of unconventional shale oil and gas horizontal well sections in the Sichuan Basin as an example: the Longmaxi Formation is mainly composed of non-expanding clay, with poor hydration expansion and dispersion capabilities, but it contains illite-saturated mixed layers, making it highly water-sensitive and prone to wellbore collapse and instability. The well-developed shale bedding and microfractures provide natural channels for drilling fluid filtrate intrusion. The filtrate intrudes into the shale, causing surface hydration. The hydration film "wedges" into the shale, connecting microfractures to the main fracture. Finally, mechanical damage occurs along the weakest point of the formation, leading to wellbore instability such as rockfall.

[0006] The Longmaxi Formation exhibits dual wetting characteristics, with an oil wetting angle of 37.8°. When using oil-based drilling fluids, the intrusion of oil-phase filtrate easily induces adsorption, dissolution, and swelling of the oil phase and organic matter. Different types of organic matter have different dissolution and swelling characteristics, resulting in varying swelling pressures or solvation repulsion forces, causing stress imbalances within the formation. This can easily lead to formation spalling or collapse along bedding planes and fracture surfaces. Furthermore, the Longmaxi-Wufeng Formation shale exhibits well-developed bedding and fractures, with widespread horizontal bedding fractures and high-angle structural fractures, and locally numerous fractures and small faults forming "ant-like" structures. The organic-rich black shale of the Longyi-1 sub-member is a key target layer for shale gas development, considered a "geological sweet spot." Studies of its sub-layers revealed that the Longyi-14 section has a high clay content, the Longyi-13 section has well-developed shale bedding, and the Longyi-12 and Longyi-11 sections have distributed pyrite bedding, high brittleness index, and are mainly continuous Class I reservoirs. These formations are highly susceptible to downhole failures, such as stuck rotary steerable assembly, when drilling to horizontal sections. Combining imaging logging data and elemental analysis of rock fragments returned from multiple wells, it was found that the rock fragments mostly originated from the interface between the Guanyinqiao Formation shell-like limestone and the Wufeng Formation siliceous mudstone at the bottom of Longyi-11. During actual drilling, under normal drilling fluid circulation, unstable shale formations experienced sudden rock fragmentation or collapse of "ant-like" formations, resulting in instantaneous top drive failure (the top drive limit is generally 25–30 kN·m), causing the rotary steerable assembly to get stuck.

[0007] Deep and ultra-deep shale gas wells require oil-based drilling fluids with high densities, generally exceeding 1.70 g / cm³, averaging 2.10 g / cm³, and reaching a maximum of 2.87 g / cm³. Micromax (ultrafine barite powder, ultrafine iron ore powder, and ultrafine manganese ore powder) are important materials for controlling the suspension stability and rheological properties of ultra-high density drilling fluids. Iron ore powder has a certain degree of magnetism, which can affect the use of measurement-while-drilling (MWD) tools. Ultramax effectively reduces interparticle frictional resistance and significantly improves the rheological properties of drilling fluids; however, its price is more than ten times that of high-density barite. Therefore, most oil-based drilling fluids use ultramax barite powder for weighting, resulting in a solid content exceeding 55% in the drilling fluid. When a rotary steerable tool assembly (including drill bit) gets stuck, the solid phase in the high-density oil-based drilling fluid gradually settles on the wellbore wall because the drill string cannot rotate. This results in barite powder deposition, causing the lower edge of the drill pipe in the horizontal section to stick. When dealing with stuck drill bits is complicated, the upward pulling force and downward pressure cannot reach the stuck rotary steerable assembly, causing the accident to worsen, leading to the failure of the rotary steerable assembly retrieval and huge losses due to well burial.

[0008] When a rotary steerable assembly gets stuck, common methods used to try to unstick it include: ① lifting and lowering with heavy-duty equipment; ② torsion of the drill string with high torque; ③ impacting the downhole accumulator. However, these methods often fail to allow the drill string (drill pipe) above the rotary steerable assembly to rotate continuously. According to fluid dynamics principles, the theoretical flow velocity at the wellbore is zero. Under gravity, solid particles move downwards towards the wellbore. As the stuck time increases, the solid phase in the high-density oil-based drilling fluid gradually settles more and more on the wellbore wall, increasing the thickness and length of solid phase burial in the lower half of the horizontal section of the drill pipe. This leads to the failure of the impactor, and the inability to apply the lifting force and lowering pressure of the hook to the stuck rotary steerable assembly. This increases the difficulty of subsequent unsticking attempts and ultimately leads to unsticking failure.

[0009] Chinese invention patent CN106150393B discloses a rotatable drill string sliding drilling sub, including a drilling fluid discharge control switch assembly and a drive shaft assembly. The drilling fluid discharge control switch assembly includes an outer cylinder, an inner cylinder, rollers, a switch slider, a first spring, a second spring, and a drilling fluid baffle structure. The drive shaft assembly includes an inner hollow shaft. The upper end of the inner hollow shaft is inserted into the inner cavity of the inner cylinder and connected to the lower end of the inner wall of the inner cylinder, and can rotate with the inner cylinder.

[0010] Chinese invention patent CN109750989B discloses a rotatable drill string directional drilling sub and a drilling method, including a housing; a cylinder housed within the housing; a switch assembly configured to separate the cylinder and housing for relative rotation when open, and to connect the cylinder and housing for synchronous rotation when closed; and a wellbore friction mechanism including a first joint connected to the cylinder and a movable member disposed within the first joint, the movable member configured to move radially according to the flow rate of drilling fluid flowing through the sub, thereby selectively applying different frictional forces to the wellbore. During directional drilling, when the switch is turned on, the drill string can rotate under the drive of the rotary table. The counter-torque of the screw drill bit below the sub is balanced by the frictional force generated by the wellbore friction mechanism, and the tool face is in a stable state, achieving the effect of a rotatable drill string for directional drilling, thereby effectively reducing the pressure drag effect and improving the mechanical drilling rate.

[0011] Both of the above invention patents have the following shortcomings: the start and stop of drill string rotation are controlled by the displacement. On the one hand, the displacement cannot be precisely controlled during on-site construction, and the compressive force generated by the displacement on the spring is affected by multiple factors such as drilling fluid density and solid content, making it impossible to effectively control the spring compression. On the other hand, when the drill string gets stuck, the accumulation of cuttings will prevent circulation, thus this structure has significant limitations in solving the problem of drill string unblocking. Summary of the Invention

[0012] The primary objective of this invention is to overcome the problems existing in the prior art and provide a shale oil and gas horizontal well anti-burrowing drilling string that can reliably unstick when stuck at the bottom and maintain the independent rotation of the upper drill string while keeping the string sealed.

[0013] To solve the above technical problems, the present invention provides a shale oil and gas horizontal well anti-burrowing drilling string, which, from bottom to top, includes a PDC drill bit, a rotary steering instrument, an anti-burrowing torque clutch, an energy storage device, and a drilling tool. The upper part of the drilling tool is driven by a drilling rig, and the energy storage device includes:

[0014] The energy storage connector has a female thread at the top that screws into the upper drill bit, and an external thread at the bottom that screws into the top of the outer cylinder.

[0015] The outer cylinder is screwed to the middle cylinder at its lower end and transmits torque to the middle cylinder;

[0016] The intermediate cylinder has a spiral groove on the lower part of its inner wall to transmit torque to the drive shaft.

[0017] The drive shaft has an outer spiral on its middle outer periphery that forms a spiral pair with the spiral groove inside the intermediate cylinder, and its lower end is screwed to the drill bit.

[0018] The piston is located in the lower inner cavity of the outer cylinder, and its lower end is screwed to the upper end of the drive shaft;

[0019] The inner sealing sleeve has its upper end screwed into the lower end of the inner threaded hole of the energy storage upper connector, and its lower end inserted into the center hole of the piston and can slide axially.

[0020] Multiple sets of butterfly springs are provided in the annular space between the outer cylinder and the inner sealing sleeve. The butterfly springs are supported between the lower end face of the energy storage connector and the upper end face of the piston.

[0021] As an improvement of the present invention, an outer shell expansion annular groove is provided above the inner spiral groove of the intermediate cylinder. The inner diameter of the outer shell expansion annular groove is larger than the outer diameter of the outer spiral of the drive shaft, and the height of the outer shell expansion annular groove is larger than the pitch of the inner spiral groove of the intermediate cylinder.

[0022] As a further improvement of the present invention, the drive shaft is provided with a drive shaft sealing section, a drive shaft cylindrical thread section, a drive shaft first expansion section, a drive shaft second expansion section, a drive shaft reduction section, a drive shaft third expansion section, a drive shaft fourth expansion section and a drive shaft tapered thread section from top to bottom, and the drive shaft outer helix is ​​located on the outer periphery of the drive shaft second expansion section.

[0023] As a further improvement of the present invention, the lower end of the intermediate cylinder is screwed with a lower sleeve, and the lower end of the lower sleeve is fitted onto the outer wall of the third expansion section of the drive shaft and they are sealed to each other.

[0024] As a further improvement of the present invention, the inner diameter of the lower sleeve is larger than the outer diameter of the second expansion section of the drive shaft.

[0025] As a further improvement of the present invention, the anti-burial torque clutch includes:

[0026] The upper connector of the clutch has its upper port connected to the energy storage device above.

[0027] The core tube is screwed into the lower end of the inner threaded hole of the upper connector of the clutch at its upper end, and has an enlarged diameter core tube sealing section in the middle section and external torque teeth evenly distributed around the lower circumference.

[0028] The torque sleeve has its upper end fitted onto the lower outer periphery of the upper connector of the clutch, and its lower inner periphery is provided with inner torque teeth that mesh with the outer torque teeth;

[0029] The clutch lower connector is screwed onto the underside of the torque sleeve.

[0030] As an improvement to the present invention, the anti-burrowing drilling string for shale oil and gas horizontal wells also includes:

[0031] The liquid cylinder is fitted around the outer periphery of the core tube and its upper end is sealed to the core tube, while its middle inner wall is sealed to the core tube sealing section.

[0032] A hydraulic cylinder shear pin locks the upper part of the hydraulic cylinder to the outer wall of the core tube;

[0033] The upper part of the core tube sealing section and the top of the hydraulic cylinder form a hydraulic chamber, and the core tube is provided with a pressure transmission hole that communicates with the hydraulic chamber.

[0034] As a further improvement of the present invention, the outer periphery of the liquid cylinder is fitted with an elastic sleeve, the top cover of the elastic sleeve covers the top of the liquid cylinder, and a plurality of slots with lower openings are evenly provided on the lower circumference of the elastic sleeve. An elastic claw with the lower end protruding outward is provided between adjacent slots, and each elastic claw is embedded in a claw groove on the lower inner periphery of the torque sleeve. The claw groove is located above the inner torque tooth.

[0035] As a further improvement of the present invention, the lower end of the claw groove is a horizontal right angle side, and the upper end is provided with a chamfer.

[0036] As a further improvement of the present invention, each of the elastic claws is provided with a claw upper conical surface that is narrower at the top and wider at the bottom, and the claw upper conical surface is in contact with the chamfer of the claw groove.

[0037] As a further improvement of the present invention, each of the elastic claws is provided with a claw lower conical surface that is narrower at the top and wider at the bottom. Each claw lower conical surface abuts against the outer conical surface of the core tube at the lower end of the core tube to lock each elastic claw in the claw groove of the torque sleeve. The outer conical surface of the core tube is located above the outer torque tooth.

[0038] As a further improvement of the present invention, a bearing is installed below the inner step of the middle section of the torque sleeve, the lower end of the outer ring of the bearing abuts against the retaining ring of the hole, the retaining ring of the hole is embedded in the retaining ring groove of the inner wall of the torque sleeve, and the inner ring of the bearing is fitted on the lower outer periphery of the elastic sleeve, so that the elastic sleeve can rotate relative to the torque sleeve.

[0039] As a further improvement of the present invention, a ball seat support sleeve is provided below the core tube, and an outwardly folded support sleeve protrusion is provided at the upper end of the ball seat support sleeve. The outer edge of the support sleeve protrusion is pressed between the torque sleeve and the lower joint of the clutch. A ball seat body for pressing the ball seat is installed in the ball seat support sleeve.

[0040] As a further improvement of the present invention, the outer periphery of the upper large-diameter section of the ball seat body is fixed to the inner wall of the ball seat support sleeve by ball seat shear pins, and the middle section of the ball seat support sleeve 7 has flow holes evenly distributed on its circumferential wall.

[0041] As a further improvement of the present invention, a ball seat sealing ring is embedded in the outer periphery of the upper large-diameter section of the ball seat body to achieve a seal with the inner wall of the ball seat support sleeve.

[0042] As a further improvement of the present invention, the lower end of the ball seat support sleeve is provided with a reduced diameter inner step, and the lower end of the ball seat body passes through the central hole of the inner step of the support sleeve.

[0043] As a further improvement of the present invention, an axial gap is provided between the lower end of the core tube and the top of the ball seat support sleeve.

[0044] As a further improvement of the present invention, during normal drilling, the torque from the upper tubing is transmitted to the core tube through the upper joint of the clutch, and the outer torque teeth at the lower end of the core tube transmit the torque to the inner torque teeth of the torque sleeve, and then transmit it downward through the lower joint of the clutch.

[0045] As a further improvement of the present invention, during tripping, the pulling force from the upper tubing is transmitted to the core tube through the upper joint of the clutch, then to the elastic jaws through the outer conical surface of the core tube, and then to the torque sleeve through the elastic jaws, and finally to the lower joint of the clutch through the torque sleeve.

[0046] Another objective of this invention is to overcome the problems existing in the prior art and provide a multi-block formation unblocking process for anti-burial drilling strings in shale oil and gas horizontal wells. When encountering a blockage below the clutch, it can reliably unblock the drill string, improve the unblocking success rate of the rotary steering assembly, and provide a feasible solution for unblocking rotary steering rigs in complex, multi-block shale oil and gas wells.

[0047] To solve the above technical problems, the present invention provides a multi-block formation unblocking process for shale oil and gas horizontal well anti-burrowing drilling string, comprising the following steps:

[0048] S1. The pressure-reducing buoy is thrown into the tubing from the ground, and the pressure-reducing buoy falls into the bell mouth of the buoy seat to achieve setting and sealing;

[0049] S2. Press down the drill bit to eliminate the axial gap between the core tube and the ball seat support sleeve. The outer conical surface of the core tube at the lower end of the core tube separates from the lower conical surface of each elastic jaw, so that each elastic jaw has a radial retraction space.

[0050] S3. Start the pump and pressurize to 8-10MPa to cut the hydraulic cylinder shear pin. The pressurized fluid enters the hydraulic chamber of the hydraulic cylinder through the pressure transmission hole. Under the pressure, the hydraulic cylinder pushes the elastic sleeve upward. The elastic claws at the lower end retract and disengage from the claw groove of the torque sleeve. When the elastic claws abut against the lower part of the bearing inner ring, the elastic sleeve reaches the top dead center.

[0051] S4. Continue to pressurize to 15-17 MPa to cut the ball seat shear pin. The ball seat body falls to the inner step of the support sleeve at the lower end of the ball seat support sleeve, and the flow hole is opened to establish a circulation channel.

[0052] S5. Inject the unsticking agent from the wellhead and circulate it through the flow hole to the stuck point in the drill string annulus to soak and dissolve the fallen block until the set soaking time is reached.

[0053] S6. Press down the drill string to re-engage the outer torque teeth at the lower end of the core tube with the inner torque teeth of the torque sleeve. Then rotate the drill string to drive the rotary guide and PDC drill bit below to rotate, thereby releasing the stuck parts. At the same time as rotating the drill string, perform a large-volume circulation to circulate the fallen blocks out of the wellhead and prevent them from accumulating again above the rotary guide.

[0054] As an improvement of the present invention, in step S5, the upper drill string is kept in the soaking period so that the outer torque tooth at the lower end of the core tube disengages from the inner torque tooth of the torque sleeve, and the drill string is rotated from the ground to prevent the upper drill string from being buried due to the solid phase deposition of drilling fluid; the elastic chuck and the inner ring of the bearing follow the rotation of the upper drill string to reduce rotational friction.

[0055] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. When the anti-burial torque clutch of the present invention is connected, the tension is transmitted from the core tube to the torque sleeve through the elastic claw. Since the elastic claw is subjected to shear rather than tension, the whole has higher tensile strength. After the clutch is disengaged, the upper drill bit can rotate freely, but still has strong tensile strength, ensuring the lifting and lowering of the device and the smooth retrieval of the rotary guide to the wellhead.

[0056] 2. The anti-burial torque clutch has high reliability, ensuring that the shearing mechanism is never under stress during normal drilling, thus preventing the risk of premature shearing due to shearing fatigue. The ball seat uses an anti-fall-off design; after the shearing cycle is established, the pressure ball and ball seat body will not fall off like traditional ball seats, thus preventing the risk of clogging the water hole. This invention achieves both circulating flow and prevents the ball seat from falling off and clogging the water hole.

[0057] 3. This invention, by strategically positioning the shale oil and gas horizontal well anti-burrowing drilling string within the drilling string, allows for torque gear disengagement when the lower rotary steering tool becomes stuck. This is achieved by pressing down on the drill string, holding the pressure, and then lifting the drill string, enabling the upper drill string to rotate freely. During drilling fluid circulation, the deposited solid phase is carried along with the drill string, preventing the upper drill string from becoming stuck due to drilling fluid solid phase deposition. After pressing down, the torque clutch can again transmit torque, driving the lower rotary steering tool and PDC drill bit to rotate, thus releasing the stuck drill string.

[0058] 4. Wait for the unblocking fluid to dissolve the shale fragments between the rotary steerable instrument and the well wall. After pressing down, rotate the drill string, and the torque teeth of the drill pipe anti-burial clutch will re-engage, driving the rotary steerable instrument and PDC drill bit to rotate and unblock. This will protect the rotary steerable instrument and allow it to be successfully pulled out to the wellhead, reducing the risk of burial and reducing well construction costs.

[0059] 5. Used in formations with microfractures, horizontal bedding fractures, and high-angle structural fractures, as well as in "ant-like" formations with numerous local fractures and small faults, where the rotary steering assembly becomes stuck. By pre-designing the drilling string, the anti-burrowing drilling string for shale oil and gas horizontal wells is positioned above the rotary steering instrument or above the predicted obstruction point. After the drill string becomes stuck, the torque transmission between the upper drill string and the lower stuck rotary steering instrument is released through the drill string anti-burrowing clutch joint, while maintaining the string seal, thus allowing the drill string above the obstruction point to rotate freely.

[0060] 6. During the drilling fluid circulation process, the drill string above the stuck point can always rotate, driving the solid phase deposited in the horizontal section of the drilling fluid to participate in the circulation with the drilling fluid, preventing the upper drill string from being buried by the deposited solid phase, thus improving the success rate of unsticking the rotary steerable assembly and providing a feasible solution for unsticking the rotary steerable assembly in complex, multi-block shale oil and gas wells.

[0061] 7. The energy storage device uses a disc spring as a buffer element. During drilling, the impact force of the drill bit contacting the formation is absorbed by the disc spring. By storing and releasing abnormal torque generated during drilling operations, it is possible to adjust drilling torque fluctuations in real time, i.e., "peak shaving and valley filling", to solve problems such as drill bit sticking, skipping, and slippage in hard formations and interlayers of PDC drill bits.

[0062] 8. It is less affected by downhole conditions, does not fatigue, has a long service life, good energy storage effect, and does not have high sealing requirements.

[0063] 9. Reduce the occurrence of jamming and slippage, avoid drill string torsional vibration, and prevent drill string breakage; prevent drill bit tooth breakage and damage, and improve drill bit life; prevent damage to downhole drilling tools and rotary steering instruments. Attached Figure Description

[0064] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The drawings are provided for reference and illustration only and are not intended to limit the present invention.

[0065] Figure 1 This is a schematic diagram of the anti-burrowing drilling string for shale oil and gas horizontal wells according to the present invention;

[0066] Figure 2 This is a front view of the anti-burial torque clutch in this invention;

[0067] Figure 3 for Figure 2 Half-sectional view of the intermediate torque sleeve;

[0068] Figure 4 for Figure 2 3D view of the core tube;

[0069] Figure 5 for Figure 2A three-dimensional view of a medium elastic sleeve;

[0070] Figure 6 This is a schematic diagram of the energy storage device in this invention;

[0071] In the diagram: A. PDC drill bit; B. Rotary steerable instrument; C. Anti-burrowing torque clutch; D. Energy accumulator; E. Drilling tool;

[0072] Anti-buried torque clutch C: 1. Upper clutch connector; 1a. Tapered female thread; 1b. Plain tube section; 2. Torque sleeve; 2a. Internal torque teeth; 3. Core tube; 3a. Core tube countersunk hole; 3b. Pressure transmission hole; 3c. Core tube sealing section; 3d. Core tube outer tapered surface; 3e. External torque teeth; 3f. Core tube sealing ring; 4. Elastic sleeve; 4a. Elastic pawl; 4b. Upper tapered surface of pawl; 4c. Lower tapered surface of pawl; 5. Hydraulic cylinder; 5a. Hydraulic cylinder sealing ring; 5b. Hydraulic cylinder countersunk pin; 6. Bearing; 6a. Hole retaining ring; 7. Ball seat support sleeve; 7a. Flow hole; 7b. Inner step of support sleeve; 8. Pressure ball; 9. Ball seat body; 9a. Ball seat sealing ring; 9b. Ball seat countersunk pin; 10. Lower clutch connector;

[0073] Energy accumulator D: 11. Energy storage upper connector; 11a. Upper connector sealing ring; 12. Outer cylinder; 13. Inner sealing sleeve; 14. Disc spring; 15. Piston; 15a. Piston upper sealing ring; 15b. Piston lower sealing ring; 15c. Piston outer sealing ring; 16. Intermediate cylinder; 16a. Screw plug; 17. Drive shaft; 17a. Drive shaft outer helix; 18. Lower sleeve; 19. Lower sleeve sealing ring. Detailed Implementation

[0074] In the following description of the present invention, the terms "upper," "lower," "front," "rear," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device must have a specific orientation. Regardless of the state of the tool, being closer to the ground is collectively referred to as "upper," and being closer to the bottom of the well is collectively referred to as "lower."

[0075] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention.

[0077] like Figure 1As shown, the shale oil and gas horizontal well anti-burrowing drilling string of the present invention includes, from bottom to top, a PDC drill bit A, a rotary steerable instrument B, an anti-burrowing torque clutch C, an energy storage device D, and a drill string E. The upper part of the drill string E is directly connected to the drilling rig. The rotary steerable instrument B performs real-time geological guidance during drilling, and its outer diameter is Ф212mm, which is larger than the drill string's outer diameter Ф165mm. The drill string is composed of multiple drill pipes connected one by one by couplings. It transports drilling mud to the PDC drill bit A and, together with the PDC drill bit A, raises, lowers, or rotates the bottom hole device, extending the wellbore length.

[0078] The upper part of the drill pipe is directly connected to the top drive of the drilling rig, providing the torque and drilling fluid circulation required during drilling. The outer diameter of the PDC drill bit is greater than that of the rotary steerable instrument, which is greater than the outer diameter of the drill pipe anti-burrowing clutch, which is greater than that of the accumulator, which is greater than the outer diameter of the drill pipe.

[0079] like Figures 2 to 5 As shown, the anti-burial torque clutch C of the present invention includes an upper clutch connector 1, a torque sleeve 2, a core tube 3, an elastic sleeve 4, a hydraulic cylinder 5, a bearing 6, a ball seat support sleeve 7, a pressure ball 8, a ball seat body 9, and a lower clutch connector 10. The upper end of the upper clutch connector 1 is provided with a tapered female thread 1a to be screwed to the upper pipe column or tool. The lower end of the upper clutch connector 1 is connected to the upper end of the core tube 3 through a sealing thread. The hydraulic cylinder 5 is fitted on the outer periphery of the core tube 3 and is connected to the upper closed end of the hydraulic cylinder 5 through hydraulic cylinder shear pins 5b. Four hydraulic cylinder shear pins 5b are evenly screwed into the screw holes on the upper circumference of the hydraulic cylinder 5. The inner end of each hydraulic cylinder shear pin 5b is respectively embedded in the core tube shear pin countersunk hole 3a on the outer periphery of the core tube 3 to fix the hydraulic cylinder 5. The number of hydraulic cylinder shear pins 5b can also be adjusted by the shear value.

[0080] The upper closed end of the hydraulic cylinder 5 is fitted with a hydraulic cylinder sealing ring 5a to achieve a seal with the outer periphery of the core tube 3. The middle section of the core tube 3 is provided with an enlarged diameter core tube sealing section 3c, and the outer periphery of the core tube sealing section 3c is fitted with a core tube sealing ring 3f to achieve a seal with the inner wall of the middle section of the hydraulic cylinder 5. A hydraulic cavity is formed between the upper part of the core tube sealing section 3c and the top of the hydraulic cylinder 5, and this hydraulic cavity is connected to the central channel of the core tube 3 through a pressure transmission hole 3b.

[0081] An elastic sleeve 4 is fitted around the outer periphery of the hydraulic cylinder 5. The top of the elastic sleeve 4 is closed and abuts against the outer wall of the core tube 3. Multiple slots with open bottom ends are evenly milled on the lower circumference of the elastic sleeve 4. Elastic claws 4a with their lower ends protruding outward are provided between adjacent slots. Each elastic claw 4a is embedded in a claw groove on the lower inner circumference of the torque sleeve 2. The lower end of the claw groove is a horizontal right angle side, and the upper end is chamfered, which not only limits the upper end of the elastic claw 4a, but also facilitates the upward sliding of the elastic claw 4a.

[0082] Each elastic jaw 4a has a top milled upper conical surface 4b that is narrower at the top and wider at the bottom, which fits with the chamfer of the jaw groove; each elastic jaw 4a has a bottom milled lower conical surface 4c that is narrower at the top and wider at the bottom, which abuts against the outer conical surface 3d of the core tube at the lower end of the core tube 3, locking each elastic jaw 4a in the jaw groove of the torque sleeve 2.

[0083] The upper end of the torque sleeve 2 is fitted around the outer periphery of the light tube section 1b at the lower part of the clutch upper connector 1 and can float axially. A bearing 6 is installed below the inner step in the middle of the torque sleeve 2. The bottom of the outer ring of the bearing 6 abuts against the retaining ring 6a. The retaining ring 6a is embedded in the retaining ring groove on the inner wall of the torque sleeve 2. The inner ring of the bearing 6 is fitted around the lower outer periphery of the elastic sleeve 4.

[0084] The inner circumferential wall below the claw groove of the torque sleeve 2 is milled with evenly distributed inner torque teeth 2a, and the lower circumference of the core tube 3 is milled with evenly distributed outer torque teeth 3e. The inner torque teeth 2a and the outer torque teeth 3e mesh with each other to transmit torque.

[0085] The lower end of the torque sleeve 2 is connected to the upper end of the clutch lower connector 10 by a sealing thread. The lower end of the clutch lower connector is provided with a tapered male thread that can be screwed into the lower pipe column or tool.

[0086] The upper end of the ball seat support sleeve 7 is provided with an outwardly folded support sleeve protrusion. The outer edge of the support sleeve protrusion is pressed between the torque sleeve 2 and the clutch lower connector 10. That is, the top of the support sleeve protrusion is pressed below the circumference where the inner torque tooth 2a is located, and the bottom of the support sleeve protrusion is pressed on the upper port of the clutch lower connector 10.

[0087] The ball seat support sleeve 7 has a ball seat body 9 installed inside its inner cavity. A ball seat sealing ring 9a is embedded in the outer circumference of the upper large-diameter section of the ball seat body 9 and is fixed to the inner wall of the ball seat support sleeve 7 by ball seat shear pins 9b. The ball seat sealing ring 9a seals against the inner wall of the ball seat support sleeve 7. Flow holes 7a are evenly distributed on the circumferential wall of the middle section of the ball seat support sleeve 7, connecting the inner and outer spaces of the ball seat support sleeve 7.

[0088] The lower end of the ball seat support sleeve 7 is provided with a reduced-diameter inner step 7b, and the lower end of the ball seat body 9 passes through the central hole of the inner step 7b and is fitted with a clearance.

[0089] The ball seat shear pins 9b are evenly screwed on the circumference of the ball seat support sleeve 7 in six pieces, and the number can also be adjusted by the shear value.

[0090] A gap is provided between the lower end face of the core tube 3 and the top of the ball seat support sleeve 7, with an axial distance greater than 10mm.

[0091] The pressure ball 8 can be made of copper alloy, with external vulcanized rubber to improve sealing reliability. It does not enter the well synchronously with the tubing string. When the rotary guide instrument gets stuck and the torque clutch needs to work, it is put into the tubing string from the ground.

[0092] During normal drilling, torque is transmitted through the upper clutch connector 1, core tube 3, torque sleeve 2, and lower clutch connector 10. The bottom of the core tube 3 presses against the top of the ball seat support sleeve 7, and the two are in axial contact to transmit drilling pressure. When pulling out of the hole, the pulling force is transmitted through the upper clutch connector 1, core tube 3, elastic jaw 4a, torque sleeve 2, and lower clutch connector 10. At this time, there is an axial gap between the core tube 3 and the ball seat support sleeve 7.

[0093] During actual horizontal drilling, shale fragments can easily cause the drill string to jam at the location of the rotary steerable tool, which has a larger outer diameter. This jamming occurs between the rotary steerable tool and the wellbore, and attempts to lift, lower, vibrate, or increase torque fail to dislodge it. After prolonged circulation, drilling fluid solids deposits gradually accumulate below the drill string in the horizontal section, causing the drill string to become stuck as well.

[0094] At this point, the pressure-retaining ball 8 is dropped into the tubing from the ground. It can fall freely or be pumped by the pump. The pressure-retaining ball 8 lands in the flared opening at the top of the ball seat 9, thus achieving setting and sealing.

[0095] Then, the drill bit is pressed down by 10 tons, and relative sliding occurs between the clutch upper connector 1 and the torque sleeve 2. The axial gap between the core tube 3 and the ball seat support sleeve 7 disappears. The outer conical surface 3d of the core tube at the lower end of the core tube 3 sinks and separates from the lower conical surface 4c of the claw at the lower end of each elastic claw 4a, so that each elastic claw 4a of the elastic sleeve 4 has a radial retraction space.

[0096] The pump is started and pressurized to 8-10 MPa. The hydraulic cylinder shear pin 5b is then cut, and the pressurized fluid enters the hydraulic chamber of the hydraulic cylinder 5 through the pressure transmission hole 3b. Under pressure, the hydraulic cylinder 5 moves upward, and the elastic sleeve 4 slides upward under the push of the hydraulic cylinder 5. The elastic claws 4a at the lower end retract and slide out of the claw grooves of the torque sleeve 2, and slide upward along the inner wall of the torque sleeve 2. When the elastic claws 4a at the lower end of the elastic sleeve 4 abut against the inner ring of the bearing 6, the upward movement is restricted.

[0097] Continue pressurizing to 15-17 MPa, then cut the ball seat shear pin 9b, causing the ball seat body 9 to fall. The inner step 7b of the lower end of the ball seat support sleeve 7 limits the lower position of the ball seat body 9. This prevents the pressurized ball 8 and ball seat body 9 from falling off like traditional ball seats, thus avoiding the risk of clogging the water eye. This invention adopts a design where the parts do not separate after shearing, achieving both circulating flow and preventing them from falling off and clogging the water eye.

[0098] At this point, the flow hole 7a is opened, establishing a circulation channel. Unsticking agent is injected from the wellhead. The agent passes through the flow hole 7a and flows downwards from the drill bit water hole at the bottom of the well into the annular space outside the drill string, then upwards to reach the outer annulus of the rotary steerable instrument for soaking and unsticking, dissolving and scavenging shale chunks.

[0099] During soaking, the tubing string is kept raised so that the outer torque tooth 3e at the lower end of the core tube 3 disengages from the inner torque tooth 2a of the torque sleeve 2, allowing the drill string to rotate from the surface. This prevents the upper drill string from becoming stuck due to drilling fluid solid phase deposition during drilling fluid circulation. During this process, the elastic chuck 4a and the inner ring of the bearing 6 rotate with the upper drill string to reduce rotational friction and improve overall service life.

[0100] After the unblocking fluid has soaked the shale fragments for the set time, the fragments have dissolved. At this point, the drill string is rotated under pressure, causing the outer torque tooth 3e at the lower end of the core tube 3 to re-engage with the inner torque tooth 2a of the torque sleeve 2. This drives the rotary directional instrument and PDC drill bit below to rotate, thus unblocking the shale fragments and ensuring they can be successfully pulled to the wellhead, reducing the risk of them being buried and lowering well construction costs. Simultaneously, a high-volume circulation process is performed to circulate the loose fragments out of the wellhead, preventing them from accumulating again above the rotary directional instrument.

[0101] like Figure 6 As shown, the energy storage device D in this invention includes an upper energy storage connector 11, an outer cylinder 12, an inner sealing sleeve 13, a butterfly spring 14, a piston 15, an intermediate cylinder 16, a drive shaft 17, and a lower sealing sleeve 18.

[0102] The upper end of the energy storage upper connector 11 is provided with a tapered female thread, which is connected to the upper tool. The lower end of the energy storage upper connector 11 is provided with a tapered male thread, which is screwed to the upper end of the outer cylinder 12.

[0103] The tapered female thread at the lower end of the outer cylinder 12 is screwed into the male thread at the upper end of the intermediate cylinder 16, and the male thread at the lower end of the intermediate cylinder 16 is connected to the female thread at the upper end of the lower sleeve 18.

[0104] The inner wall of the intermediate cylinder 16 is provided with an inner spiral groove, which is screwed into the outer spiral 17a of the drive shaft on the outer periphery of the middle section of the drive shaft 17 to form a non-self-locking spiral pair.

[0105] Above the spiral groove inside the intermediate cylinder is a shell expansion annular groove. The inner diameter of the shell expansion annular groove is larger than the outer diameter of the outer spiral 17a of the drive shaft, and the height of the shell expansion annular groove is larger than the pitch of the spiral groove inside the intermediate cylinder.

[0106] The outer wall of the expanded-diameter annular groove of the intermediate cylinder 16 is provided with an oil injection screw hole, and a screw plug 16a is screwed on. After removing the screw plug 16a, lubricating oil can be poured into the tool through the threaded hole, making the helical engagement between the intermediate cylinder 16 and the drive shaft 17 smoother. Before entering the well, the screw plug 16a is used to plug the threaded hole to prevent lubricating oil from overflowing and mud from the wellbore from entering the tool.

[0107] The upper external thread section of the inner sealing sleeve 13 is screwed into the lower internal thread hole of the energy storage upper connector 11. The upper part of the external thread section is the sealing section of the inner sealing sleeve, and the upper part of the internal thread hole of the energy storage upper connector 11 is the sealing section of the energy storage upper connector. The sealing section of the energy storage upper connector is provided with two annular grooves of the energy storage upper connector. The two annular grooves of the energy storage upper connector are respectively fitted with upper connector sealing rings 11a, so as to achieve the sealing between the upper end of the inner sealing sleeve 13 and the energy storage upper connector 11.

[0108] The lower end of the inner sealing sleeve 13 is inserted into the inner cavity of the piston 15 and can slide axially relative to the piston 15 to meet the needs of compression or elongation of the buffer element.

[0109] The piston 15 has three inner ring grooves on its upper inner circumference, and each inner ring groove is fitted with an upper piston sealing ring 15a and the lower outer wall of the inner sealing sleeve 13 to achieve a seal. The piston 15 has three outer ring grooves on its lower outer circumference, and each outer ring groove is fitted with an outer piston sealing ring 15c and the inner wall of the outer cylinder 12 to achieve a seal.

[0110] A butterfly spring 14 is installed as a buffer element in the annular space between the outer cylinder 12 and the inner sealing sleeve 13.

[0111] The lower end of the piston 15 is provided with an internal piston thread for screwing into the upper end of the drive shaft 17. Two piston lower sealing rings 15b are embedded in the inner wall of the lower end of the piston 15 to achieve sealing with the outer circumference of the upper end of the drive shaft 17.

[0112] A locking screw is screwed onto the lower circumference of the piston 15. The inner end of the locking screw is embedded in the upper threaded section of the drive shaft 17. The locking screw strengthens the connection of the threaded pair and prevents circumferential displacement between the piston 15 and the drive shaft 17.

[0113] The drive shaft 17 is provided with a drive shaft sealing section, a drive shaft cylindrical thread section, a drive shaft first expansion section, a drive shaft second expansion section, a drive shaft reduction section, a drive shaft third expansion section, a drive shaft fourth expansion section, and a drive shaft tapered thread section from top to bottom. The drive shaft outer helix 17a is located on the outer periphery of the drive shaft second expansion section.

[0114] The upper connector sealing ring 11a seals the outer wall of the drive shaft sealing section. The cylindrical thread section of the drive shaft is screwed into the internal thread of the piston. The first expansion section of the drive shaft extends to be opposite to the expansion annular groove of the outer shell of the intermediate cylinder 16.

[0115] The expanded diameter annular groove of the outer shell of the intermediate cylinder 16 helps to increase the rising height of the outer spiral 17a of the drive shaft, and the reduced diameter section of the drive shaft helps to increase the relative downward distance of the intermediate cylinder 16.

[0116] The outer circumference of the second expansion section of the drive shaft is provided with an external helix 17a for engaging with the internal helical groove of the intermediate cylinder 16. The lower end of the drive shaft 17 has a tapered male thread for connecting with the lower drilling tool or drill bit.

[0117] The upper end of the lower sleeve 18 is provided with an internal thread for screwing into the lower male thread of the intermediate cylinder 16. The lower inner circumference of the lower sleeve 18 is provided with three lower sleeve inner ring grooves, and each lower sleeve inner ring groove is respectively installed with a lower sleeve sealing ring 19 to achieve sealing with the lower outer circumference of the drive shaft 17.

[0118] During drilling operations, when the torque of the PDC drill bit reaches a certain value, the drive shaft 17 moves upward through the helical pair between it and the intermediate cylinder 16, compressing the disc spring 14 through the piston 15.

[0119] When torque is continuously applied at the wellhead, the drill bit is obstructed at the bottom of the well, causing it to rise relative to the energy storage connector 11 until it returns to its original rotational speed. When the torque of the drill bit decreases, the compression of the disc spring 14 decreases, which, through the piston 15, pushes the drive shaft 17 downward through the helical pair between it and the intermediate cylinder 16, releasing the torque energy and maintaining normal drilling.

[0120] The number and arrangement of the disc springs 14 are calculated based on the well conditions and drilling parameters used by the tool.

[0121] The moment the drill string reaches the bottom of the well, the drill bit contacts the formation, creating an impact force that can damage the drill bit prematurely. The elasticity of the disc spring 14 can reduce this impact force.

[0122] The above description is merely a preferred embodiment of the present invention, illustrating and illustrating the basic principles, main features, and advantages of the invention. It is not intended to limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. In addition to the above embodiments, the present invention may have other implementations without departing from the spirit and scope of the invention. Various changes and modifications to the present invention are possible, and all technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents. Technical features not described in the present invention can be implemented by or using existing technology, and will not be elaborated upon here.

Claims

1. A drilling string for preventing burial in shale oil and gas horizontal wells, characterized in that, From bottom to top, the components include a PDC drill bit, a rotary guide, an anti-burrowing torque clutch, an energy accumulator, and drill string. The upper part of the drill string is driven by the drilling rig. The energy accumulator includes: The energy storage connector has a female thread at the top that screws into the upper drill bit, and an external thread at the bottom that screws into the top of the outer cylinder. The outer cylinder is screwed to the middle cylinder at its lower end and transmits torque to the middle cylinder; The intermediate cylinder has a spiral groove on the lower part of its inner wall to transmit torque to the drive shaft. The drive shaft has an outer spiral on its middle outer periphery that forms a spiral pair with the spiral groove inside the intermediate cylinder, and its lower end is screwed to the drill bit. The piston is located in the lower inner cavity of the outer cylinder, and its lower end is screwed to the upper end of the drive shaft; The inner sealing sleeve has its upper end screwed into the lower end of the inner threaded hole of the energy storage upper connector, and its lower end inserted into the center hole of the piston and can slide axially. Multiple sets of butterfly springs are provided in the annular space between the outer cylinder and the inner sealing sleeve. The butterfly springs are supported between the lower end face of the energy storage connector and the upper end face of the piston.

2. The shale oil and gas horizontal well anti-burrowing drilling string according to claim 1, characterized in that: Above the spiral groove inside the intermediate cylinder is a shell expansion annular groove. The inner diameter of the shell expansion annular groove is larger than the outer diameter of the outer spiral of the drive shaft, and the height of the shell expansion annular groove is larger than the pitch of the spiral groove inside the intermediate cylinder.

3. The anti-burial drilling string for shale oil and gas horizontal wells according to claim 1, characterized in that: The drive shaft is provided with a drive shaft sealing section, a drive shaft cylindrical thread section, a drive shaft first expansion section, a drive shaft second expansion section, a drive shaft reduction section, a drive shaft third expansion section, a drive shaft fourth expansion section, and a drive shaft tapered thread section from top to bottom. The drive shaft outer helix is ​​located on the outer periphery of the drive shaft second expansion section.

4. The shale oil and gas horizontal well anti-burrowing drilling string according to claim 3, characterized in that: The lower end of the intermediate cylinder is screwed with a lower sleeve, and the lower end of the lower sleeve is fitted onto the outer wall of the third expansion section of the drive shaft and they are sealed to each other.

5. The shale oil and gas horizontal well anti-burrowing drilling string according to claim 4, characterized in that: The inner diameter of the lower sleeve is larger than the outer diameter of the second expansion section of the drive shaft.

6. The anti-burial drilling string for shale oil and gas horizontal wells according to claim 1, characterized in that, The anti-buried torque clutch includes: The upper connector of the clutch has its upper port connected to the energy storage device above. The core tube is screwed into the lower end of the inner threaded hole of the upper connector of the clutch at its upper end, and has an enlarged diameter core tube sealing section in the middle section and external torque teeth evenly distributed around the lower circumference. The torque sleeve has its upper end fitted onto the lower outer periphery of the upper connector of the clutch, and its lower inner periphery is provided with inner torque teeth that mesh with the outer torque teeth; The clutch lower connector is screwed onto the underside of the torque sleeve.

7. The shale oil and gas horizontal well anti-burrowing drilling string according to claim 6, characterized in that, Also includes: The liquid cylinder is fitted around the outer periphery of the core tube and its upper end is sealed to the core tube, while its middle inner wall is sealed to the core tube sealing section. A hydraulic cylinder shear pin locks the upper part of the hydraulic cylinder to the outer wall of the core tube; The upper part of the core tube sealing section and the top of the hydraulic cylinder form a hydraulic chamber, and the core tube is provided with a pressure transmission hole that communicates with the hydraulic chamber.

8. The shale oil and gas horizontal well anti-burrowing drilling string according to claim 7, characterized in that: The outer periphery of the hydraulic cylinder is fitted with an elastic sleeve, the top cover of which covers the top of the hydraulic cylinder. The lower circumference of the elastic sleeve is evenly provided with multiple slots with openings at the lower end. Between adjacent slots, there are elastic claws with their lower ends protruding outward. Each elastic claw is embedded in a claw groove on the lower inner circumference of the torque sleeve, and the claw groove is located above the inner torque teeth.

9. The shale oil and gas horizontal well anti-burrowing drilling string according to claim 8, characterized in that: The lower end of the claw groove is a horizontal right angle side, and the upper end is chamfered; the top of each elastic claw is provided with a claw upper conical surface that is narrower at the top and wider at the bottom, and the claw upper conical surface fits into the chamfer of the claw groove.

10. The shale oil and gas horizontal well anti-burrowing drilling string according to claim 9, characterized in that: Each of the elastic claws has a lower conical surface at the bottom that is narrower at the top and wider at the bottom. Each lower conical surface abuts against the outer conical surface of the core tube at the lower end of the core tube to lock each elastic claw in the claw groove of the torque sleeve. The outer conical surface of the core tube is located above the outer torque tooth.

11. The anti-burrowing drilling string for shale oil and gas horizontal wells according to claim 8, characterized in that: A bearing is installed below the inner step in the middle section of the torque sleeve. The lower end of the outer ring of the bearing abuts against the retaining ring of the hole. The retaining ring of the hole is embedded in the retaining ring groove of the inner wall of the torque sleeve. The inner ring of the bearing is fitted on the lower outer periphery of the elastic sleeve, so that the elastic sleeve can rotate relative to the torque sleeve.

12. The shale oil and gas horizontal well anti-burrowing drilling string according to claim 8, characterized in that: The core tube is provided with a ball seat support sleeve below it. The upper end of the ball seat support sleeve is provided with an outwardly folded support sleeve protrusion. The outer edge of the support sleeve protrusion is pressed between the torque sleeve and the lower clutch connector. A ball seat body for pressing the ball seat is installed in the ball seat support sleeve.

13. The anti-burrowing drilling string for shale oil and gas horizontal wells according to claim 12, characterized in that: The outer circumference of the upper large-diameter section of the ball seat body is fixed to the inner wall of the ball seat support sleeve by ball seat shear pins, and the middle section of the ball seat support sleeve has evenly distributed flow holes.

14. The anti-burrowing drilling string for shale oil and gas horizontal wells according to claim 12, characterized in that: The upper large-diameter section of the ball seat is fitted with a ball seat sealing ring, which seals against the inner wall of the ball seat support sleeve.

15. The anti-burrowing drilling string for shale oil and gas horizontal wells according to claim 12, characterized in that: The lower end of the ball seat support sleeve is provided with a reduced-diameter inner step, and the lower end of the ball seat body passes through the central hole of the inner step of the support sleeve.

16. The anti-burrowing drilling string for shale oil and gas horizontal wells according to claim 12, characterized in that: An axial gap is provided between the lower end of the core tube and the top of the ball seat support sleeve.

17. A multi-block formation unblocking process for shale oil and gas horizontal well anti-burial drilling string as described in claim 16, characterized in that, Includes the following steps: S1. The pressure-reducing buoy is thrown into the tubing from the ground, and the pressure-reducing buoy falls into the bell mouth of the buoy seat to achieve setting and sealing; S2. Press down the drill bit to eliminate the axial gap between the core tube and the ball seat support sleeve. The outer conical surface of the core tube at the lower end of the core tube separates from the lower conical surface of each elastic jaw, so that each elastic jaw has a radial retraction space. S3. Start the pump and pressurize to 8-10MPa to cut the hydraulic cylinder shear pin. The pressurized fluid enters the hydraulic chamber of the hydraulic cylinder through the pressure transmission hole. Under the pressure, the hydraulic cylinder pushes the elastic sleeve upward. The elastic claws at the lower end retract and disengage from the claw groove of the torque sleeve. When the elastic claws abut against the lower part of the bearing inner ring, the elastic sleeve reaches the top dead center. S4. Continue to pressurize to 15-17 MPa to cut the ball seat shear pin. The ball seat body falls to the inner step of the support sleeve at the lower end of the ball seat support sleeve, and the flow hole is opened to establish a circulation channel. S5. Inject the unsticking agent from the wellhead and circulate it through the flow hole to the stuck point in the drill string annulus to soak and dissolve the fallen block until the set soaking time is reached. S6. Press down the drill string to re-engage the outer torque teeth at the lower end of the core tube with the inner torque teeth of the torque sleeve. Then rotate the drill string to drive the rotary guide and PDC drill bit below to rotate, thereby releasing the stuck parts. At the same time as rotating the drill string, perform a large-volume circulation to circulate the fallen blocks out of the wellhead and prevent them from accumulating again above the rotary guide.

18. The multi-block formation unblocking process for shale oil and gas horizontal well anti-burial drilling string according to claim 17, characterized in that: In step S5, the tubing string is kept raised during soaking, so that the outer torque teeth at the lower end of the core tube disengage from the inner torque teeth of the torque sleeve, and the drill string is rotated from the ground to prevent the upper drill string from being buried due to drilling fluid solid phase deposition; the elastic chuck and the inner ring of the bearing follow the rotation of the upper drill string to reduce rotational friction.

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