Shale oil and gas horizontal well anti-burying drilling pipe column and multi-falling-block stratum jam releasing process

Abstract

The invention discloses a shale oil and gas horizontal well anti-burying drilling pipe column and a multi-falling-block stratum jam releasing process, the shale oil and gas horizontal well anti-burying drilling pipe column comprises a PDC drill bit, a rotary steering instrument, an anti-burying torque clutch, an energy storage device and a drilling tool from bottom to top in sequence, and the energy storage device comprises an energy storage upper connector; the lower end of the outer cylinder is screwed with the middle cylinder, and the outer cylinder transmits torque to the middle cylinder; the lower part of the inner wall of the middle cylinder is provided with a middle cylinder inner spiral groove for transmitting torque to the driving shaft; the periphery of the middle part of the driving shaft is provided with a driving shaft outer spiral and a middle cylinder inner spiral groove to form a spiral pair, and the lower end is screwed with a drill bit; the piston is located in a lower inner cavity of the outer cylinder, and the lower end of the piston is rotationally connected with the upper end of the driving shaft; the upper end of the inner sealing sleeve is screwed in an inner screw hole in the lower end of the energy storage upper connector, and the lower end of the inner sealing sleeve is inserted in a center hole of the piston and can axially slide; a plurality of sets of belleville springs are arranged in an annular space between the outer barrel and the inner sealing sleeve and supported between the lower end face of the upper energy storage connector and the upper end face of the piston. The drilling tool can be prevented from being buried, and jam releasing is convenient.

Description

Technical Field

[0001] The invention relates to a horizontal well drilling string, in particular to a shale oil and gas horizontal well anti-buried drilling string. The invention also relates to a multi-block formation unblocking process for the shale oil and gas horizontal well anti-buried drilling string, belonging to the technical field of petroleum drilling. Background Art

[0002] Domestic deep shale oil and gas reservoirs are buried deep, generally ≥3500m. The target layer is generally drilled with a Ф215.9mm drill bit combined with a rotary steerable instrument. The rotary steerable drilling system has many advantages, which can effectively improve the mechanical drilling speed, control the wellbore trajectory in real time, improve the wellbore quality, and reduce the overall drilling cost. However, the instrument itself has a large outer diameter and strong rigidity, and the probability of the rotary steerable instrument being stuck due to formation block drop is high. The formations of my country's deep shale oil and gas wells are complex, and there are many complex underground conditions, which pose severe challenges to exploration and development. In the process of horizontal well drilling of shale gas in the Longmaxi Formation in southern Sichuan, there are complex drilling conditions such as wellbore instability, serious block drop, and frequent blockage. From 2019 to 2021, CNPC and Sinopec have buried 59 sets of rotary steerable instruments in the process of drilling shale gas wells in southern Sichuan, with a burial rate of up to 9.75%. The rotary steerable instrument is a high-precision technology product with extremely high cost. If it is buried, the loss will be great. In the complex wells with rotary steering for buried wells, the stuck drill accident occurred at the rotary steering position of the horizontal section (outer diameter 212mm), mainly due to the shale falling off and the stuck drill. After the rotary steering of many shale gas horizontal wells stuck the drill, except that the drill tool could not move freely, the drilling fluid circulation displacement was normal and the pump pressure was normal. Once the rotary steering instrument stuck the drill and buried the well, the loss was huge.

[0003] In addition, during the drilling process, abnormal fluctuations in torque can easily lead to self-excited vibration of the drill string, breakage of the drill bit, and stagnation of the screw drill bit, resulting in frequent lifting of the drill bit and fluctuations in pump pressure, affecting drilling efficiency. When drilling in gravel layers or formations with high hardness and poor stability, serious drill jumping will occur, causing great damage to the drill bit and drill bit.

[0004] At present, shale dissolving agents have been developed on site to destroy the structural strength of shale according to the characteristics of the formation lithology components. However, after the rotary steerable instrument is stuck, it generally takes 3 to 4 days from organizing the unblocking agent or shale corrosive agent, to the unblocking agent or shale corrosive agent entering the well, and dissolving the blocks. During this period, the drill bit cannot be moved freely or rotated. During the circulation of the drilling fluid, the solid phase in the drilling fluid above the stuck point in the horizontal section gradually deposits on the lower well wall, or the drill bit circulates for a long time in a static state. The wellbore cuttings and small-sized blocks cannot be effectively returned under the stirring of the drill bit, resulting in most of them gradually spreading and accumulating between the drill pipe and the lower well wall, causing the lower side of the drill pipe in the horizontal well section to be gradually buried, causing more drill bits to be stuck, and increasing the difficulty of subsequent unblocking.

[0005] In the process of exploration and development of unconventional shale oil and gas wells, horizontal well sections often use near-bit while-drilling monitoring of formation gamma values ​​to ensure that the maximum amount of high-quality carbonaceous shale is obtained by rotary drilling in a directional manner, in order to maximize engineering, geological and economic benefits. Take 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, and the hydration expansion and dispersion capabilities of the formation are poor, but it contains illite-montmorillonite mixed layers, which are highly water-sensitive and easily cause wellbore collapse and instability. The shale bedding and microcracks are developed, providing a natural channel for the invasion of drilling fluid filtrate. The filtrate invades the shale to hydrate the surface, and the hydration film "wedges" to connect the microcracks to the main fracture. Finally, the formation is mechanically damaged along the weakest point, causing wellbore instability such as block drop.

[0006] The Longmaxi Formation has the characteristics of dual wetting, with an oil wetting angle of 37.8°. When using oil-based drilling fluid, the invasion of oil phase filtrate is likely to cause adsorption, dissolution, swelling and other effects between the oil phase and organic matter. Different types of organic matter have different dissolution and swelling characteristics, and the resulting swelling pressure or solvation repulsion is different, causing stress imbalance inside the formation, which can easily cause the formation to peel off or collapse along the bedding and fracture sections. At the same time, the shale lamination and fractures of the Longmaxi Formation-Wufeng Formation are very developed, horizontal bedding fractures and high-angle structural fractures are generally developed, and multiple fractures and small faults are locally developed in the "ant body" structure. Among them, the organic-rich black shale in the Longyi 1 sub-member is the main target layer "geological sweet spot" for shale gas development. The study of its sub-layers shows that the clay content of Longyi 14 is high, the lamination of Longyi 13 is well developed, the pyrite stratification distribution of Longyi 12 and Longyi 11 is high, the brittleness index is high, and the continuous Class I reservoir is dominant. When drilling to the horizontal section, it is very easy to get stuck in the downhole failure of the rotary guide instrument combination. Combining the imaging logging data and the element analysis results of the block returned from multiple wells, it is found that the blocks are mostly from the interface between the shell limestone of Guanyinqiao Formation and the siliceous mudstone of Wufeng Formation at the bottom of Longyi 11. During the actual drilling process, under the condition of normal circulation of drilling fluid, the unstable shale formation peels off or the "ant body" formation suddenly collapses, and the top drive phenomenon stops instantly (the general limit of top drive is 25-30kN.m), resulting in the stuck drill of the rotary guide instrument combination.

[0007] The density of oil-based drilling fluid in deep and ultra-deep shale gas wells is high, generally exceeding 1.70g / cm³, averaging 2.10 g / cm³, and reaching a maximum of 2.87g / cm³. Ultrafine barite powder, ultrafine iron ore powder, and ultrafine manganese ore powder (MicroMax) are important materials for regulating the suspension stability and rheology of ultra-high density drilling fluids. Iron ore powder has a certain degree of magnetism, which will affect the use of measurement while drilling tools. Ultrafine manganese ore powder can effectively reduce the friction resistance between particles and significantly improve the rheology of drilling fluids, but its price is more than ten times that of high-density barite. Therefore, most oil-based drilling fluids are weighted with ultrafine barite powder, resulting in a solid content of more than 55% in the drilling fluid. After the rotary steerable (including drill bit) tool combination gets stuck, the drill bit cannot rotate, and the solid phase in the high-density oil-based drilling fluid gradually settles on the wellbore wall below the wellbore, causing barite powder to deposit and causing sticking on the lower side of the horizontal drill pipe. When handling the stuck drill, the upward pulling force and downward pressure cannot reach the stuck rotary steerable combination, causing the accident to worsen, resulting in the failure of the rotary steerable combination salvage and huge well burial losses.

[0008] After the rotary guide assembly is stuck, the following methods are generally used to try to release the stuck drill bit: ① lifting and lowering with large tonnage; ② twisting the drill bit with high torque; ③ shocking the downhole energy storage device up and down, but the drill bit is unable to continuously rotate the drill bit (drill pipe) above the rotary guide assembly. According to the principles of fluid mechanics, the theoretical flow rate of the well wall treatment is 0. Under the action of gravity, the solid phase particles move toward the lower well wall. As the stuck drill bit time increases, the solid phase in the high-density oil-based drilling fluid gradually settles more and more on the well wall below the wellbore, aggravating the buried thickness and length of the solid phase in the lower half of the horizontal section drill pipe, resulting in the failure of the jar, the pulling force of the large hook lifting and the pressure of the lower hook, which cannot be applied to the stuck rotary guide assembly part, making the subsequent release of the rotary guide assembly more difficult and leading to the failure of the release.

[0009] The Chinese invention patent with publication number CN106150393B discloses a rotatable drill string sliding drilling short section, including a drilling fluid displacement control switch assembly and a transmission shaft assembly; the drilling fluid displacement control switch assembly includes an outer cylinder, an inner cylinder, a roller, a switch slider, a first spring, a second spring and a drilling fluid baffle structure; the transmission 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 is connected to the lower end of the inner wall of the inner cylinder, and can rotate with the inner cylinder.

[0010] The Chinese invention patent with the publication number CN109750989B discloses a rotatable drill string directional drilling short section and a drilling method, including a housing; a cylinder body arranged in the cylinder housing; a switch assembly, the switch assembly is configured to separate the cylinder body and the housing when turned on so that they can rotate relative to each other, and to connect the cylinder body and the housing when turned off so that they can rotate synchronously; a well wall friction mechanism, including a first joint connected to the cylinder body, and a movable member arranged in the first joint, the movable member is configured to be able to move radially according to the displacement of the drilling fluid flowing through the short section, so as to selectively apply different friction forces to the well wall. During directional drilling, the switch is turned on, the drill pipe can rotate under the drive of the turntable, the counter torque of the screw drill tool below the short section is balanced by the friction force generated by the well wall friction mechanism, the tool face is in a stable state, and the effect of the rotatable drill string for directional drilling is achieved, thereby effectively reducing the support pressure effect and improving the mechanical drilling speed.

[0011] The above two invention patents have the following shortcomings: the start and stop of drill string rotation is controlled by displacement. On the one hand, the displacement cannot be accurately controlled during on-site construction, and the compression force generated by the displacement on the spring is also affected by multiple factors such as drilling fluid density and solid content, and the spring compression cannot be effectively controlled. On the other hand, when the drill bit is stuck, it will be unable to circulate due to the accumulation of rock cuttings, so this structure has great limitations in solving the problem of unblocking the drill bit. Summary of the invention

[0012] The primary purpose of the present invention is to overcome the problems existing in the prior art and provide a shale oil and gas horizontal well anti-buried drilling string that can reliably unstuck when stuck at the bottom, and can maintain the independent rotation of the upper drill bit while maintaining the sealing of the string.

[0013] In order to solve the above technical problems, a shale oil and gas horizontal well anti-buried drilling string of the present invention comprises a PDC drill bit, a rotary guide instrument, an anti-buried torque clutch, an energy accumulator and a drilling tool from bottom to top, wherein the upper part of the drilling tool is driven by a drilling rig, and the energy accumulator comprises: The energy storage upper joint has an upper female thread that is screwed to the upper drilling tool, and a lower external thread that is screwed to the upper end of the outer cylinder; The outer cylinder body has a lower end which is screwed to the middle cylinder and transmits torque to the middle cylinder; The middle cylinder has a spiral groove at the lower part of the inner wall to transmit torque to the drive shaft; The driving shaft has an outer spiral of the driving shaft at the middle outer periphery, which forms a spiral pair with the spiral groove in the intermediate cylinder, and the lower end is screwed to the drill bit; A piston, located in the lower inner cavity of the outer cylinder, and 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 inner screw hole at the lower end of the energy storage upper joint, and the lower end of which is inserted into the central hole of the piston and can slide axially; A plurality of groups of butterfly springs are arranged in the annular space between the outer cylinder and the inner sealing sleeve, and the butterfly springs are supported between the lower end surface of the energy storage upper joint and the upper end surface of the piston.

[0014] As an improvement of the present invention, an outer shell expansion ring groove is provided above the spiral groove in the intermediate cylinder, the inner diameter of the outer shell expansion ring groove is larger than the outer diameter of the outer spiral of the drive shaft, and the height of the outer shell expansion ring groove is larger than the pitch of the spiral groove in the intermediate cylinder.

[0015] 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 conical thread section in sequence from top to bottom, and the drive shaft outer spiral is located on the outer periphery of the second expansion section of the drive shaft.

[0016] As a further improvement of the present invention, a lower sealing sleeve is screwed onto the lower end of the intermediate cylinder, and the lower end of the lower sealing sleeve is sleeved onto the outer wall of the third diameter expansion section of the drive shaft and the two are sealed with each other.

[0017] As a further improvement of the present invention, the inner diameter of the lower sleeve is larger than the outer diameter of the second diameter expansion section of the drive shaft.

[0018] As a further improvement of the present invention, the anti-buried torque clutch comprises: The upper connector of the clutch has an upper port connected to the energy storage device above; The core tube has an upper end screwed into the inner screw hole at the lower end of the clutch upper joint, a core tube sealing section with an expanded diameter is provided in the middle section, and external torque teeth are evenly provided on the circumference of the lower end; A torque sleeve, the upper end of which is sleeved on the lower outer periphery of the upper joint of the clutch, and the lower inner periphery is provided with inner torque teeth meshing with the outer torque teeth; The clutch lower joint is screwed under the torque sleeve.

[0019] As an improvement of the present invention, the shale oil and gas horizontal well anti-buried drilling string also includes: A liquid cylinder is sleeved on the outer periphery of the core tube and the upper ends are sealed with each other, and the inner wall of the middle part is sealed with the sealing section of the core tube; Cylinder shear pins lock the upper portion of the cylinder to the outer wall of the core tube; The upper part of the sealing section of the core tube and the top of the hydraulic cylinder form a hydraulic chamber, and the core tube is provided with a pressure transmission hole which communicates with the hydraulic chamber.

[0020] As a further improvement of the present invention, an elastic sleeve is mounted on the outer periphery of the liquid cylinder, and the top cover of the elastic sleeve covers the top of the liquid cylinder. A plurality of slots with lower ends opening are evenly arranged on the lower circumference of the elastic sleeve, and elastic claws with lower ends protruding toward the outer periphery are arranged between adjacent slots. Each elastic claw is embedded in a claw groove on the inner periphery of the lower part of the torque sleeve, and the claw groove is located above the inner torque tooth.

[0021] As a further improvement of the present invention, the lower end of the claw embedding groove is a horizontal right-angled side, and the upper end is provided with a chamfer.

[0022] As a further improvement of the present invention, the top of each elastic claw is provided with a claw upper conical surface which is narrow at the top and wide at the bottom, and each claw upper conical surface fits with the chamfer of the claw embedding groove.

[0023] As a further improvement of the present invention, the bottom of each elastic claw is provided with a claw lower conical surface which is narrow at the top and wide at the bottom. Each claw lower conical surface abuts against the core tube outer conical surface at the lower end of the core tube to lock each elastic claw in the claw groove of the torque sleeve. The core tube outer conical surface is located above the external torque tooth.

[0024] 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 hole retaining ring, the hole retaining ring is embedded in the retaining ring groove of the inner wall of the torque sleeve, and the inner ring of the bearing is sleeved on the middle and lower outer periphery of the elastic sleeve, so that the elastic sleeve can rotate relative to the torque sleeve.

[0025] As a further improvement of the present invention, a ball seat support sleeve is provided below the core tube, and a support sleeve convex ring folded outward is provided at the upper end of the ball seat support sleeve, and the outer edge of the support sleeve convex ring is pressed between the torque sleeve and the lower joint of the clutch, and a ball seat body for sealing the pressure ball is installed in the ball seat support sleeve.

[0026] 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 nails, and the middle circumferential wall of the ball seat support sleeve 7 is evenly distributed with flow holes.

[0027] As a further improvement of the present invention, a ball seat sealing ring is embedded in the outer periphery of the large diameter section at the upper end of the ball seat body to achieve sealing with the inner wall of the ball seat support sleeve.

[0028] As a further improvement of the present invention, the lower end of the ball seat support sleeve is provided with a support sleeve inner step with a reduced diameter, and the lower end of the ball seat body passes through the center hole of the support sleeve inner step.

[0029] 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.

[0030] As a further improvement of the present invention, during normal drilling, the torque from the upper pipe string is transmitted to the core pipe through the upper joint of the clutch, and the outer torque teeth at the lower end of the core pipe transmit the torque to the inner torque teeth of the torque sleeve, and then transmit it downward through the lower joint of the clutch.

[0031] As a further improvement of the present invention, when drilling, the pulling force from the upper pipe string is transmitted to the core pipe through the upper joint of the clutch, then transmitted to the elastic claw through the outer cone surface of the core pipe, and then transmitted from the elastic claw to the torque sleeve, and then transmitted downward by the torque sleeve through the lower joint of the clutch.

[0032] Another object of the present invention is to overcome the problems existing in the prior art and provide a process for unstuck multi-block formations of shale oil and gas horizontal well anti-buried drilling pipes, which can reliably unstuck when stuck below the clutch, thereby improving the unstuck success rate of the rotary guide instrument combination, and providing a feasible solution for unstuck rotary guide instruments in complex shale oil and gas wells with multiple block drops.

[0033] In order to solve the above technical problems, a multi-block formation unstuck process for an anti-buried drilling string for shale oil and gas horizontal wells of the present invention comprises the following steps: S1. Put the pressure ball into the pipe string from the ground, and the pressure ball falls into the bell mouth of the ball seat to achieve sealing; S2, press down the drill tool to make the axial gap between the core tube and the ball seat support sleeve disappear, and the outer cone surface of the core tube at the lower end of the core tube is separated from the lower cone surface of the claw at the lower end of each elastic claw, so that each elastic claw has recovery space in the radial direction; S3. Turn on the pump and hold the pressure to 8-10MPa to cut off the hydraulic cylinder shear pins. The pressure liquid enters the hydraulic chamber of the hydraulic cylinder through the pressure transmission hole. Under the action of pressure, the hydraulic cylinder moves upward against the elastic sleeve. The elastic claws at the lower end are recovered and separated from the claw grooves of the torque sleeve. When the elastic claws are against the lower inner ring of the bearing, the elastic sleeve reaches the top dead center. S4, continue to hold the pressure to 15-17 MPa to cut off the ball seat shear nails, the ball seat body falls to the step inside the support sleeve at the lower end of the ball seat support sleeve, the flow hole is opened, and the circulation channel is established; S5, injecting a de-stuck agent from the wellhead, circulating the de-stuck agent to the stuck point of the drill string annulus through the flow hole to soak and dissolve the fallen blocks until the set soaking time is reached; S6. Press down the drill bit to re-engage the outer torque teeth at the lower end of the core tube with the inner torque teeth of the torque sleeve, and then rotate the drill bit to drive the rotary guide instrument and PDC drill bit below to rotate to achieve jam release; while rotating the drill bit, perform a large displacement circulation to circulate the dropped blocks out of the wellhead to prevent them from accumulating again above the rotary guide instrument.

[0034] As an improvement of the present invention, in step S5, the pipe column is kept lifted during immersion so that the outer torque teeth at the lower end of the core pipe are disengaged from the inner torque teeth of the torque sleeve, and the drill bit is rotated from the ground to prevent the upper drill bit from being buried due to solid phase deposition of drilling fluid; the elastic claws and the inner ring of the bearing rotate with the upper drill bit to reduce rotational friction.

[0035] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. When the anti-buried torque clutch of the present invention is connected, the pulling force is transmitted from the core tube to the torque sleeve through the elastic claws. Since the elastic claws bear shear rather than tension, the overall tensile strength is higher; after the clutch is disconnected, the upper drilling tool can rotate freely, but still has a strong tensile strength, ensuring that the lifting and lowering are unblocked, and the rotary guide instrument can be smoothly lifted to the wellhead.

[0036] 2. The anti-buried torque clutch has high reliability. During normal drilling, the shearing mechanism is always unstressed to prevent the risk of premature shearing due to fatigue of the shearing nails. The ball seat adopts an anti-drop design. After the shearing nail shearing cycle is established, the pressure-holding ball and the ball seat body will not fall like the traditional ball seat, causing the risk of blocking the water eye. The present invention not only realizes the circulation flow, but also prevents the water eye from falling and blocking the water eye.

[0037] 3. The present invention sets a shale oil and gas horizontal well anti-buried drilling string at a reasonable position in the drilling string. When the lower rotary guide instrument is stuck, the torque teeth are disengaged by pressing down the drill tool, holding the pressure, and lifting the drill tool, so that the upper drill tool can rotate freely. When the drilling fluid circulates, the deposited solid phase is driven to participate in the circulation, preventing the upper drill tool from being buried due to the deposition of the drilling fluid solid phase. After pressing down, the torque clutch can realize torque transmission again, driving the lower rotary guide instrument and the PDC drill bit to rotate, and realize unblocking.

[0038] 4. Wait for the unstuck fluid to dissolve the shale between the rotary guide instrument and the well wall, press down and rotate the drill bit, the torque teeth of the drill pipe anti-buried clutch will re-engage, drive the rotary guide instrument and PDC drill bit to rotate and unblock, thereby protecting the rotary guide instrument from being smoothly lifted to the wellhead, reducing the risk of being buried and reducing the cost of well construction.

[0039] 5. After the rotary steering combination is stuck in formations with crisscrossing microcracks, horizontal bedding fractures and high-angle structural fractures, and in "ant body" formations with many local fractures and small faults and many block formations, the anti-buried drilling string for shale oil and gas horizontal wells is set above the rotary steering instrument or above the predicted resistance point through reasonable design of the drilling string in advance. After the drill is stuck, the torque transmission between the upper drill bit and the lower stuck rotary steering instrument is released through the drill bit anti-buried clutch joint, but the string is still kept sealed, so that the drill bit above the resistance point can rotate freely.

[0040] 6. During the circulation of drilling fluid, the drill bit above the stuck point can keep rotating all the time, driving the solid phase deposition of drilling fluid in the horizontal section to participate in the circulation with the drilling fluid, preventing the upper drill bit from being buried by the deposited solid phase and causing sticking or drilling burial, thereby improving the success rate of the rotary guide instrument combination for unstuck, and providing a feasible solution for the rotary guide instrument for drilling complex shale oil and gas wells with many broken blocks.

[0041] 7. The energy accumulator uses butterfly springs as buffer elements. During the drilling process, the impact force of the drill bit contacting the formation is absorbed by the butterfly springs. By storing and releasing the abnormal torque generated during the drilling operation, the drilling torque fluctuation can be adjusted in real time, that is, "peak shaving and valley filling", solving the problems of PDC drill bits in hard formations and interlayers, such as stuck drilling, sticking and slipping.

[0042] 8. It is less affected by underground conditions, will not get tired, has a long service life, has good energy storage effect, and does not require high sealing.

[0043] 9. Reduce the occurrence of sticking and slipping, avoid torsional vibration of drill tools, and prevent drill tool breakage; prevent drill bit tooth breakage and damage, and increase drill bit life; prevent damage to downhole drilling tools and rotary guide instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The accompanying drawings are only provided for reference and explanation and are not intended to limit the present invention.

[0045] Figure 1 This is a schematic diagram of the structure of the anti-buried drilling string for shale oil and gas horizontal wells of the present invention; Figure 2 It is a front view of the anti-buried torque clutch in the present invention; Figure 3 for Figure 2 A half-section view of the middle torque sleeve; Figure 4 for Figure 2 A three-dimensional view of the core tube; Figure 5 for Figure 2 A three-dimensional view of the middle elastic sleeve; Figure 6 It is a structural schematic diagram of the energy storage device in the present invention; In the figure: A. PDC drill bit; B. Rotary guide instrument; C. Anti-buried torque clutch; D. Energy accumulator; E. Drilling tool; Anti-buried torque clutch C: 1. Clutch upper joint; 1a. Conical female thread; 1b. Smooth tube section; 2. Torque sleeve; 2a. Internal torque teeth; 3. Core tube; 3a. Core tube shear pin countersunk hole; 3b. Pressure transmission hole; 3c. Core tube sealing section; 3d. Core tube outer cone surface; 3e. External torque teeth; 3f. Core tube sealing ring; 4. Elastic sleeve; 4a. Elastic claw; 4b. Upper cone surface of claw; 4c. Lower cone surface of claw; 5. Liquid cylinder; 5a. Liquid cylinder sealing ring; 5b. Liquid cylinder shear pin; 6. Bearing; 6a. Circlip for hole; 7. Ball seat support sleeve; 7a. Flow hole; 7b. Inner step of support sleeve; 8. Pressure holding ball; 9. Ball seat body; 9a. Ball seat sealing ring; 9b. Ball seat shear pin; 10. Clutch lower joint; Energy accumulator D: 11. Energy storage upper joint; 11a. Upper joint sealing ring; 12. Outer cylinder; 13. Inner sealing sleeve; 14. Butterfly 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 spiral; 18. Lower sealing sleeve; 19. Lower sealing sleeve sealing ring. DETAILED DESCRIPTION

[0046] In the following description of the present invention, the terms "upper", "lower", "front", "back", "left", "right", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the 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, the one closer to the ground is collectively referred to as "upper", and the one closer to the bottom of the well is collectively referred to as "lower".

[0047] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below with reference to specific diagrams.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0049] like Figure 1 As shown, the shale oil and gas horizontal well anti-buried drilling string of the present invention includes PDC drill bit A, rotary guide instrument B, anti-buried torque clutch C, energy storage device D, and drilling tool E from bottom to top, and the upper part of drilling tool E is directly connected to the drilling rig. When the drill string is rotated for drilling, the rotary guide instrument B completes the geological guidance function in real time while drilling, and its outer diameter is Ф212mm, which is larger than the outer diameter of the drilling tool Ф165mm. The drilling tool is formed by screwing multiple drill rods one by one through a coupling, transporting the drilling mud to the PDC drill bit A, and raising, lowering or rotating the bottom hole device together with the PDC drill bit A, and extending the wellbore length.

[0050] The upper part of the drill pipe is directly connected to the top drive of the drilling rig to provide the torque and drilling fluid circulation required during drilling. Among them, the outer diameter of the PDC drill bit> the outer diameter of the rotary guide instrument> the outer diameter of the drill pipe anti-buried clutch> the outer diameter of the energy accumulator> the outer diameter of the drill pipe.

[0051] like Figures 2 to 5 As shown, the anti-buried torque clutch C in the present invention includes a clutch upper joint 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-holding ball 8, a ball seat body 9 and a clutch lower joint 10. The upper end of the clutch upper joint 1 is provided with a tapered female thread 1a for screwing with an upper pipe column or a tool. The inner screw hole at the lower end of the clutch upper joint 1 is connected to the upper end of the core tube 3 through a sealing thread. The outer periphery of the core tube 3 is sleeved with a hydraulic cylinder 5, and is connected to the upper closed end of the hydraulic cylinder 5 through a hydraulic cylinder shear nail 5b. Four hydraulic cylinder shear nails 5b are evenly screwed in the screw holes on the upper circumference of the hydraulic cylinder 5. The inner ends of the hydraulic cylinder shear nails 5b are respectively embedded in the core tube shear nail countersunk holes 3a on the outer periphery of the core tube 3 to fix the hydraulic cylinder 5. The number of hydraulic cylinder shear nails 5b can also be adjusted by the shear value.

[0052] The upper closed end of the liquid cylinder 5 is embedded with a liquid cylinder sealing ring 5a to achieve sealing with the outer periphery of the core tube 3. The middle section of the core tube 3 is provided with a core tube sealing section 3c with an expanded diameter, and the outer periphery of the core tube sealing section 3c is embedded with a core tube sealing ring 3f to achieve sealing with the inner wall of the middle section of the liquid cylinder 5. A hydraulic chamber is formed between the upper part of the core tube sealing section 3c and the top of the liquid cylinder 5, and the hydraulic chamber is communicated with the central channel of the core tube 3 through the pressure transmission hole 3b.

[0053] The outer periphery of the cylinder 5 is covered with an elastic sleeve 4, the top of the elastic sleeve 4 is closed and abuts against the outer wall of the core tube 3, a plurality of slots with lower ends open are evenly milled on the lower circumference of the elastic sleeve 4, and elastic claws 4a with lower ends protruding toward the outer periphery are arranged between adjacent slots, and each elastic claw 4a is embedded in a claw embedding groove on the inner periphery of the lower middle part of the torque sleeve 2. The lower end of the claw embedding groove is a horizontal right-angled side, and the upper end is provided with a chamfer, which not only limits the upper end of the elastic claw 4a, but also facilitates the elastic claw 4a to slide upward.

[0054] The top of each elastic claw 4a is milled with an upper conical surface 4b that is narrow at the top and wide at the bottom, and the upper conical surface 4b of the claw cooperates with the chamfer of the claw groove; the bottom of each elastic claw 4a is milled with a lower conical surface 4c that is narrow at the top and wide at the bottom, and the lower conical surface 4c of the claw rests on the outer conical surface 3d of the core tube at the lower end of the core tube 3, thereby locking each elastic claw 4a in the claw groove of the torque sleeve 2.

[0055] The upper end of the torque sleeve 2 is sleeved on the outer periphery of the light tube section 1b at the lower part of the clutch upper joint 1 and can float axially. A bearing 6 is installed below the inner step in the middle part of the torque sleeve 2. The bottom of the outer ring of the bearing 6 abuts against the hole retaining ring 6a. The hole 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 sleeved on the outer periphery of the middle and lower part of the elastic sleeve 4.

[0056] The inner circumferential wall below the claw groove of the torque sleeve 2 is milled with uniformly distributed internal torque teeth 2a, and the lower end of the core tube 3 is circumferentially milled with uniformly distributed external torque teeth 3e. The internal torque teeth 2a and the external torque teeth 3e mesh with each other to transmit torque.

[0057] The lower end of the torque sleeve 2 is connected to the upper end of the clutch lower joint 10 through a sealing thread. The lower end of the clutch lower joint is provided with a tapered male thread that is screwed to the lower pipe column or tool.

[0058] The upper end of the ball seat support sleeve 7 is provided with a support sleeve convex ring folded outward, and the outer edge of the support sleeve convex ring is pressed between the torque sleeve 2 and the clutch lower joint 10, that is, the top of the support sleeve convex ring is pressed below the circumference of the inner torque tooth 2a, and the bottom of the support sleeve convex ring is pressed on the upper port of the clutch lower joint 10.

[0059] The inner cavity of the ball seat support sleeve 7 is equipped with a ball seat body 9, and 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 fixed to the inner wall of the ball seat support sleeve 7 by ball seat shear nails 9b, so that the ball seat sealing ring 9a is sealed with the inner wall of the ball seat support sleeve 7. The middle circumferential wall of the ball seat support sleeve 7 is evenly distributed with flow holes 7a to communicate the inner and outer spaces of the ball seat support sleeve 7.

[0060] The lower end of the ball seat support sleeve 7 is provided with a support sleeve inner step 7b with a reduced diameter, and the lower end of the ball seat body 9 passes through the central hole of the support sleeve inner step 7b and is clearance-matched with each other.

[0061] There are six ball seat shear nails 9b evenly screwed on the circumference of the ball seat support sleeve 7, and the number can also be adjusted by the shear value.

[0062] A gap is provided between the lower end surface of the core tube 3 and the top of the ball seat support sleeve 7, and the axial distance is greater than 10 mm.

[0063] The pressure holding ball 8 can be made of copper alloy, and the external vulcanized rubber improves the sealing reliability. It does not enter the well synchronously with the pipe string. When the rotary guide instrument is stuck and the torque clutch needs to work, it is put into the pipe string from the ground.

[0064] During normal drilling, the torque is transmitted through the clutch upper joint 1, the core tube 3, the torque sleeve 2, and the clutch lower joint 10. The bottom of the core tube 3 is pressed on the top of the ball seat support sleeve 7, and the two are in axial contact to transmit drilling pressure. When drilling, the pulling force is transmitted through the clutch upper joint 1, the core tube 3, the elastic claw 4a, the torque sleeve 2, and the clutch lower joint 10. At this time, there is an axial gap between the core tube 3 and the ball seat support sleeve 7.

[0065] When drilling in the actual horizontal section, shale blocks are very likely to get stuck at the rotary guide tool position with a larger outer diameter, that is, stuck between the rotary guide tool and the well wall. Lifting, lowering, jarring and increasing torque can never unblock it. After a long period of circulation, the solid phase deposition of drilling fluid will gradually increase below the horizontal section drill bit, causing the drill bit position to also get stuck.

[0066] At this time, the pressure-holding ball 8 is thrown into the pipe column from the ground, and can fall freely, or the pump can be turned on to pump the pressure-holding ball 8. The pressure-holding ball 8 falls into the horn mouth at the upper end of the ball seat body 9 to realize the setting.

[0067] Then the drill bit is pressed down by 10 tons, and relative sliding occurs between the clutch upper joint 1 and the torque sleeve 2. The axial clearance between the core tube 3 and the ball seat support sleeve 7 disappears, and the outer conical surface 3d of the core tube at the lower end of the core tube 3 sinks and disengages 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 recovery space in the radial direction.

[0068] The pump is turned on and the pressure is held up to 8-10 MPa, the hydraulic cylinder shear pin 5b is cut off, and the pressure fluid enters the hydraulic chamber of the hydraulic cylinder 5 through the pressure transmission hole 3b. The hydraulic cylinder 5 moves upward under the pressure, and the elastic sleeve 4 slides upward under the push of the hydraulic cylinder 5. The elastic claws 4a at the lower end are recovered 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 lower inner ring of the bearing 6, the rise is limited.

[0069] Continue to hold the pressure to 15-17 MPa, cut off the ball seat shear nail 9b, and the ball seat body 9 falls down. The inner step 7b of the support sleeve at the lower end of the ball seat support sleeve 7 sets a lower limit on the ball seat body 9. The pressure holding ball 8 and the ball seat body 9 will not fall down like the traditional ball seat, causing the risk of blocking the water eye. The present invention adopts a design of not separating after shearing off, which not only realizes the circulation flow, but also prevents the falling and blocking the water eye.

[0070] At this time, the flow hole 7a is opened to establish a circulation channel. The unstuck agent is injected from the wellhead, and the unstuck agent passes through the flow hole 7a downward from the drill bit water hole at the bottom of the well into the annular space outside the drill string, and then reaches the outer annulus of the rotary guide instrument upward to soak and unstuck, dissolving the shale blocks.

[0071] During the soaking period, the pipe column is lifted up to disengage the outer torque teeth 3e at the lower end of the core pipe 3 from the inner torque teeth 2a of the torque sleeve 2, and the drill tool is rotated from the ground to avoid the risk of the upper drill tool being buried due to the solid phase deposition of the drilling fluid during the circulation of the drilling fluid. During this process, the elastic claw 4a and the inner ring of the bearing 6 rotate with the upper drill tool to reduce the rotational friction and increase the overall service life.

[0072] After the unstuck liquid is soaked for a set time, the shale blocks have been dissolved. At this time, the drill bit is rotated after pressing down, so that the outer torque teeth 3e at the lower end of the core tube 3 re-engage with the inner torque teeth 2a of the torque sleeve 2, driving the rotary guide instrument and PDC drill bit below to rotate, and unstuck, thereby protecting the rotary guide instrument so that it can be smoothly brought to the wellhead, reducing the risk of being buried and reducing the cost of well construction. While rotating the drill bit, a large displacement cycle is performed to circulate the loose blocks out of the wellhead to prevent the blocks from accumulating again above the rotary guide instrument.

[0073] like Figure 6 As shown, the energy accumulator D in the present invention includes an energy storage upper joint 11, an outer cylinder 12, an inner sealing sleeve 13, a butterfly spring 14, a piston 15, an intermediate cylinder 16, a driving shaft 17 and a lower sealing sleeve 18.

[0074] The upper end of the energy storage upper joint 11 is provided with a tapered female thread connected to the upper tool, and the lower end of the energy storage upper joint 11 is provided with a tapered male thread screwed to the upper end of the outer cylinder 12 .

[0075] The tapered female thread at the lower end of the outer cylinder 12 is screwed to 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 sealing sleeve 18 .

[0076] The inner wall of the intermediate cylinder 16 is provided with an intermediate cylinder inner spiral groove, which is screwed together with the driving shaft outer spiral 17a on the outer periphery of the middle section of the driving shaft 17 to form a non-self-locking spiral pair.

[0077] A shell diameter expansion ring groove is provided above the spiral groove in the intermediate cylinder. The inner diameter of the shell diameter expansion ring groove is larger than the outer diameter of the outer spiral 17a of the driving shaft, and the height of the shell diameter expansion ring groove is larger than the pitch of the spiral groove in the intermediate cylinder.

[0078] The outer wall of the enlarged diameter ring 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 screw hole, so that the spiral matching movement of the intermediate cylinder 16 and the drive shaft 17 is smoother. Before entering the well, the screw plug 16a is used to block the screw hole to prevent the lubricating oil from overflowing and the mud in the wellbore from entering the tool.

[0079] The external threaded section at the upper end of the inner sealing sleeve 13 is screwed into the internal threaded hole at the lower end of the energy storage upper joint 11. The inner sealing sleeve sealing section is located above the external threaded section, and the energy storage upper joint sealing section is located above the internal threaded hole of the energy storage upper joint 11. The energy storage upper joint sealing section is provided with two energy storage upper joint annular grooves, in which upper joint sealing rings 11a are respectively embedded, to achieve sealing between the upper end of the inner sealing sleeve 13 and the energy storage upper joint 11.

[0080] 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 extension of the buffer element.

[0081] The piston 15 has three inner ring grooves on its upper inner circumference, each of which is respectively embedded with a piston upper sealing ring 15a to seal with the lower outer wall of the inner sealing sleeve 13. The piston 15 has three outer ring grooves on its lower outer circumference, each of which is respectively embedded with a piston outer sealing ring 15c to seal with the inner wall of the outer cylinder 12.

[0082] A disc spring 14 is installed in the annular space between the outer cylinder 12 and the inner sealing sleeve 13 as a buffer element.

[0083] The lower end of the piston 15 is provided with a piston internal thread for being screwed with the upper end of the drive shaft 17. The inner wall of the lower end of the piston 15 is embedded with two piston lower sealing rings 15b to seal with the outer periphery of the upper end of the drive shaft 17.

[0084] A locking screw is screwed on the lower circumference of the piston 15, and 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 strength of the thread pair to prevent the piston 15 and the drive shaft 17 from circumferential displacement.

[0085] 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 conical thread section from top to bottom, and the drive shaft outer spiral 17a is located on the outer periphery of the second expansion section of the drive shaft.

[0086] The upper joint sealing ring 11a is sealed on the outer wall of the driving shaft sealing section, the driving shaft cylindrical thread section is screwed with the piston internal thread, and the first diameter expansion section of the driving shaft extends to be opposite to the outer shell diameter expansion ring groove of the intermediate cylinder 16.

[0087] The outer shell diameter expansion ring groove of the intermediate cylinder 16 is conducive to increasing the rising height of the outer spiral 17a of the driving shaft, and the reduced diameter section of the driving shaft is conducive to increasing the relative downward distance of the intermediate cylinder 16.

[0088] The outer circumference of the second enlarged diameter section of the drive shaft is provided with an outer drive shaft spiral 17a for cooperating with the inner spiral groove of the intermediate tube 16. The lower end of the drive shaft 17 has a tapered male thread for screwing with the lower drilling tool or drill bit.

[0089] The upper end of the lower seal 18 is provided with an internal thread for screwing with the lower male thread of the intermediate tube 16. The inner circumference of the lower end of the lower seal 18 is provided with three lower seal inner ring grooves, each of which is respectively installed with a lower seal ring 19 to achieve sealing with the lower outer circumference of the drive shaft 17.

[0090] During drilling construction, when the torque of the PDC drill bit reaches a certain value, the drive shaft 17 moves upward through the spiral pair between the drive shaft 17 and the intermediate cylinder 16 , and the butterfly spring 14 is compressed through the piston 15 .

[0091] When the torque is continuously applied at the wellhead, the drill bit is blocked at the bottom of the well, causing the drill bit to rise relative to the energy storage upper joint 11 until the drill bit returns to its original rotation speed. When the torque of the drill bit decreases, the compression of the butterfly spring 14 decreases, and the piston 15 pushes the drive shaft 17 downward through the spiral pair between the piston 15 and the intermediate cylinder 16, releasing the torque energy and maintaining the normal drilling of the drill bit.

[0092] The number and arrangement of the butterfly springs 14 are obtained by comprehensive calculation based on the conditions of the well in which the tool is used and the drilling parameters.

[0093] When the drill string reaches the bottom of the well, the drill bit contacts the stratum and there is an impact force, which can impact the drill bit and cause early damage to the drill bit. The elasticity of the butterfly spring 14 can reduce this impact force.

[0094] The above is only a preferred embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention, but does not limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. In addition to the above embodiments, the present invention may have other implementation modes without departing from the spirit and scope of the present invention. The present invention may also have various changes and improvements, and all technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents. The technical features not described in the present invention can be realized by or using existing technologies, which will not be repeated here.

Claims

1. A shale oil and gas horizontal well anti-buried drilling string, characterized in that: From bottom to top, it includes a PDC drill bit, a rotary guide instrument, an anti-buried torque clutch, an energy accumulator and a drilling tool. The upper part of the drilling tool is driven by the drilling rig. The energy accumulator includes: The energy storage upper joint has an upper female thread that is screwed to the upper drilling tool, and a lower external thread that is screwed to the upper end of the outer cylinder; The outer cylinder body has a lower end which is screwed to the middle cylinder and transmits torque to the middle cylinder; The lower part of the inner wall of the intermediate cylinder is provided with an inner spiral groove of the intermediate cylinder to transmit torque to the driving shaft; The driving shaft has an outer spiral of the driving shaft at the middle outer periphery, which forms a spiral pair with the spiral groove in the intermediate cylinder, and the lower end is screwed to the drill bit; A piston, located in the lower inner cavity of the outer cylinder, and 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 inner screw hole at the lower end of the energy storage upper joint, and the lower end of which is inserted into the central hole of the piston and can slide axially; A plurality of groups of butterfly springs are arranged in the annular space between the outer cylinder and the inner sealing sleeve, and the butterfly springs are supported between the lower end surface of the energy storage upper joint and the upper end surface of the piston.

2. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 1, characterized in that: A shell diameter expansion ring groove is provided above the spiral groove in the intermediate cylinder. The inner diameter of the shell diameter expansion ring groove is larger than the outer diameter of the outer spiral of the drive shaft. The height of the shell diameter expansion ring groove is larger than the pitch of the spiral groove in the intermediate cylinder.

3. The anti-buried 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 diameter expansion section, a drive shaft second diameter expansion section, a drive shaft reduced diameter section, a drive shaft third diameter expansion section, a drive shaft fourth diameter expansion section and a drive shaft conical thread section in sequence from top to bottom, and the drive shaft outer spiral is located on the outer periphery of the second diameter expansion section of the drive shaft.

4. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 3 is characterized by: A lower sealing sleeve is screwed onto the lower end of the intermediate cylinder, and the lower end of the lower sealing sleeve is sleeved on the outer wall of the third diameter expansion section of the drive shaft and sealed with each other.

5. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 4, characterized in that: The inner diameter of the lower sleeve is greater than the outer diameter of the second expanded diameter section of the drive shaft.

6. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 1, characterized in that: The anti-buried torque clutch comprises: The upper connector of the clutch has an upper port connected to the energy storage device above; The core tube has an upper end screwed into the inner screw hole at the lower end of the clutch upper joint, a core tube sealing section with an expanded diameter is provided in the middle section, and external torque teeth are evenly provided on the circumference of the lower end; A torque sleeve, the upper end of which is sleeved on the lower outer periphery of the upper joint of the clutch, and the lower inner periphery is provided with inner torque teeth meshing with the outer torque teeth; The clutch lower joint is screwed under the torque sleeve.

7. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 6, characterized in that: Also includes: A liquid cylinder is sleeved on the outer periphery of the core tube and the upper ends are sealed with each other, and the inner wall of the middle part is sealed with the sealing section of the core tube; Cylinder shear pins lock the upper portion of the cylinder to the outer wall of the core tube; The upper part of the sealing section of the core tube and the top of the hydraulic cylinder form a hydraulic chamber, and the core tube is provided with a pressure transmission hole which communicates with the hydraulic chamber.

8. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 7, characterized in that: An elastic sleeve is sleeved on the outer circumference of the liquid cylinder, and the top cover of the elastic sleeve covers the top of the liquid cylinder. A plurality of slots with lower ends opening are evenly arranged on the lower circumference of the elastic sleeve, and elastic claws with lower ends protruding toward the outer circumference are arranged between adjacent slots. Each elastic claw is embedded in a claw embedding groove on the inner circumference of the lower part of the torque sleeve, and the claw embedding groove is located above the inner torque tooth.

9. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 8, characterized in that: The lower end of the clamping claw groove is a horizontal right-angled side, and the upper end is provided with a chamfer; the top of each elastic clamping claw is respectively provided with a clamping claw upper conical surface which is narrow at the top and wide at the bottom, and each clamping claw upper conical surface fits with the chamfer of the clamping claw groove.

10. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 9, characterized in that: The bottom of each elastic claw is provided with a claw lower conical surface which is narrow at the top and wide at the bottom. Each claw lower conical surface abuts against the core tube outer conical surface at the lower end of the core tube to lock each elastic claw in the claw groove of the torque sleeve. The core tube outer conical surface is located above the external torque tooth.

11. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 8, characterized in that: 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 hole retaining ring, the hole retaining ring is embedded in the retaining ring groove of the inner wall of the torque sleeve, and the inner ring of the bearing is sleeved on the middle and lower outer periphery of the elastic sleeve, so that the elastic sleeve can rotate relative to the torque sleeve.

12. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 8, characterized in that: A ball seat support sleeve is provided below the core tube, and a support sleeve convex ring folded outward is provided at the upper end of the ball seat support sleeve. The outer edge of the support sleeve convex ring is pressed between the torque sleeve and the lower joint of the clutch, and a ball seat body for sealing the pressure ball is installed in the ball seat support sleeve.

13. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 12, characterized in that: 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 through ball seat shear nails, and the middle section circumferential wall of the ball seat support sleeve is evenly distributed with flow holes.

14. The anti-buried drilling string for shale oil and gas horizontal wells according to claim 12, characterized in that: A ball seat sealing ring is embedded on the outer periphery of the large diameter section at the upper end of the ball seat body to achieve sealing with the inner wall of the ball seat support sleeve.

15. The anti-buried 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 support sleeve inner step with a reduced diameter, and the lower end of the ball seat body passes through the central hole of the support sleeve inner step.

16. The anti-buried 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 process for releasing stuck blocks in multi-block formations of a shale oil and gas horizontal well anti-buried drilling string as claimed in claim 16, characterized in that: The steps include: S1. Put the pressure ball into the pipe string from the ground, and the pressure ball falls into the bell mouth of the ball seat to achieve sealing; S2, press down the drill tool to make the axial gap between the core tube and the ball seat support sleeve disappear, and the outer cone surface of the core tube at the lower end of the core tube is separated from the lower cone surface of the claw at the lower end of each elastic claw, so that each elastic claw has recovery space in the radial direction; S3. Turn on the pump and hold the pressure to 8-10MPa to cut off the hydraulic cylinder shear pins. The pressure liquid enters the hydraulic chamber of the hydraulic cylinder through the pressure transmission hole. Under the action of pressure, the hydraulic cylinder moves upward against the elastic sleeve. The elastic claws at the lower end are recovered and separated from the claw grooves of the torque sleeve. When the elastic claws are against the lower inner ring of the bearing, the elastic sleeve reaches the top dead center. S4, continue to hold the pressure to 15-17 MPa to cut off the ball seat shear nails, the ball seat body falls to the step inside the support sleeve at the lower end of the ball seat support sleeve, the flow hole is opened, and the circulation channel is established; S5, injecting a de-stuck agent from the wellhead, circulating the de-stuck agent to the stuck point of the drill string annulus through the flow hole to soak and dissolve the fallen blocks until the set soaking time is reached; S6. Press down the drill bit to re-engage the outer torque teeth at the lower end of the core tube with the inner torque teeth of the torque sleeve, and then rotate the drill bit to drive the rotary guide instrument and PDC drill bit below to rotate to achieve jam release; while rotating the drill bit, perform a large displacement circulation to circulate the dropped blocks out of the wellhead to prevent them from accumulating again above the rotary guide instrument.

18. The process for releasing stuck blocks in multi-block formations of a shale oil and gas horizontal well anti-buried drilling string according to claim 17, characterized in that: In step S5, the pipe column is lifted up during the soaking period, so that the outer torque teeth at the lower end of the core pipe are disengaged from the inner torque teeth of the torque sleeve, and the drill bit is rotated from the ground to prevent the upper drill bit from being buried due to the solid phase deposition of the drilling fluid; the elastic claws and the inner ring of the bearing rotate with the upper drill bit to reduce the rotational friction.

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