Straight well infinite-stage tubing fracturing pipe column technology and implementation method

Abstract

The present application provides a kind of straight well infinite level tubing fracturing pipe string process and implementation method, belong to oilfield completion fracturing device technical field.The well killing valve is located in the uppermost end, hydraulic anchor and packer are sequentially arranged below the well killing valve;Infinite level fracturing sliding sleeve, safety release joint and packer are sequentially arranged between two target layers;Infinite level fracturing sliding sleeve is arranged at each downhole target layer;Infinite level fracturing sliding sleeve includes opening tool assembly for controlling the opening of infinite level fracturing sliding sleeve;Telescopic pipe is arranged between the packer of each target layer and the infinite level fracturing sliding sleeve of next target layer;Set sealing ball seat above the target layer closest to artificial bottom, sealing ball seat can provide pressure holding condition when setting sealing.The present application solves the problem that the existing straight well pressure distribution pipe string process technology is limited in pressure distribution number, fracturing scale, while reducing the difficulty of setting and releasing operation of pressure distribution pipe string, having pipe string sand burying ability, improving the safety of pressure distribution pipe string.

Description

Technical Field

[0001] This invention relates to the field of oilfield well completion and fracturing equipment technology, and in particular to a process and method for fracturing tubing strings for vertical wells with unlimited tubing. Background Technology

[0002] For vertical well stratified fracturing, the packer + sliding sleeve stratified fracturing string process is a long-established technique with a wealth of string technology and downhole tools. Especially for old areas and old wells undergoing repeated fracturing, due to the long service life of the casing and tubing, casing damage and leakage are prominent, making it impossible to use the casing as a fracturing string. The combination of tubing with a packer and sliding sleeve is almost the only feasible solution.

[0003] Although this type of process offers a variety of tubular options, they generally share the following common problems that are difficult to overcome:

[0004] 1. Limitations on the Number of Fracturing Stages. For vertical well fracturing strings, regardless of string structure variations, fracturing sleeves must be used as fluid passages between the string and the formation during fracturing. Currently, fracturing sleeves are deployed using a step-by-step ball dropping method, dropping balls in ascending order of sleeve diameter to open fracturing sleeves at different formations. Since the tubing string operating within the casing is inherently small, radial dimensions are extremely valuable. This method limits the number of fracturing stages (generally no more than 3 stages for commonly used 139.7mm casings). Furthermore, the inner diameter of the first and second stage sleeves is constrained by radial dimensions (wellbore inner diameter) and is typically smaller, making it impossible to match the inner diameter of the uppermost sleeve.

[0005] 2. Impact on Fracturing Scale. As mentioned earlier, the working principle of the fracturing sliding sleeve results in a very small inner diameter at the lowest sliding sleeve, given the already limited number of pressure distribution stages. During fracturing operations, the increased displacement leads to higher throttling pressure, causing an increase in the operating pump pressure. This not only affects engineering safety but also results in greater energy waste. Simultaneously, at the same operating displacement, the fluid velocity flowing through the narrower sliding sleeve increases significantly, eroding downhole tools and oil layer casing. This not only affects the safety of the tubing string but also causes irreversible damage to the oil layer casing.

[0006] 3. Impact on operational safety. A series of issues affecting operational safety before and after fracturing operations include: whether the fracturing string is reliably set; whether tool erosion is severe during fracturing, whether layer replacement is smooth and safe; and whether the fracturing string can be successfully unsealed after fracturing, and whether it will be buried by sand.

[0007] Currently, vertical well fracturing string technology cannot achieve unlimited fracturing stages. Generally, expandable packers or combinations of multiple packer types are used. Expandable packers require continuous fluid flow to set, making pre-setting impossible and the reliability of the setting unknown before operation. Furthermore, the high fluid outlet velocity due to throttling during fracturing operations with this type of packer can easily cause irreversible erosion damage to the casing. Combinations of multiple packer types, such as mechanical and hydraulic packers, result in complex string structures due to different setting methods. The setting and unsetting operations differ, making setting and unsetting difficult. Moreover, downhole accessories such as safety couplings cannot simultaneously accommodate the structural characteristics of both packers. This complexity leads to high safety risks.

[0008] The existing technology has at least the following shortcomings:

[0009] 1. The number of pressure-distributing stages and the scale of fracturing are limited by the vertical well pressure-distributing tubing technology;

[0010] 2. The operation of unsealing the pressure divider string is difficult;

[0011] 3. It lacks the ability to prevent sand burial in the tubing, and the safety of the pressure-distributing tubing is low. Summary of the Invention

[0012] To address the problems existing in the prior art, this invention provides a vertical well infinite-stage tubing fracturing string process, comprising: a kill valve, a telescopic pipe, a hydraulic anchor, a packer, an infinite-stage fracturing sliding sleeve, a safety release connector, and a setting ball seat; the kill valve is located at the uppermost end, and the hydraulic anchor and packer are sequentially arranged between the kill valve and the first downhole target layer; the hydraulic anchor is anchored to the inner wall of the casing; the infinite-stage fracturing sliding sleeve, the safety release connector, and the packer are sequentially arranged between each downhole target layer and the next downhole target layer; the infinite-stage fracturing... A fracturing sleeve is installed at each target formation in the downhole, providing a fluid flow channel during stratified fracturing. The infinite-stage fracturing sleeve includes an opening tool assembly for controlling its opening; a safety release connector enables shear release when the tubing becomes stuck. A telescopic tube is installed between the packer of each target formation and the infinite-stage fracturing sleeve of the next target formation, and also between the kill valve and the hydraulic anchor. A setting ball seat is installed above the target formation closest to the artificial well bottom, providing pressure-locking conditions during setting. This invention solves the problems of limited fracturing stages and scale in existing vertical well fracturing tubing technology, while reducing the difficulty of setting and unsetting fracturing tubing, providing sand-proofing capabilities, and improving the safety of the fracturing tubing.

[0013] This invention provides a vertical well infinite-stage tubing fracturing string process, wherein the vertical well infinite-stage tubing fracturing string includes: a kill valve, a telescopic pipe, a hydraulic anchor, a packer, an infinite-stage fracturing sliding sleeve, a safety release joint, and a setting ball seat;

[0014] The kill valve is located at the top, and a hydraulic anchor and a packer are sequentially arranged between the kill valve and the first target formation in the well; the hydraulic anchor is anchored to the inner wall of the casing.

[0015] An infinite-stage fracturing sleeve, a safety release connector, and a packer are sequentially installed between each downhole target layer and the next downhole target layer. The infinite-stage fracturing sleeve is located at each downhole target layer to provide a fluid flow channel during stratified fracturing. The infinite-stage fracturing sleeve includes an opening tool assembly for controlling the opening of the infinite-stage fracturing sleeve, and the safety release connector can shear and release the sleeve when the tubing string becomes stuck.

[0016] The telescopic pipe is installed between the packer of each target layer and the infinite-stage fracturing sleeve of the next target layer. The telescopic pipe is also installed between the kill valve and the hydraulic anchor.

[0017] A setting ball seat is installed above the target layer closest to the bottom of the artificial well, and the setting ball seat can provide the pressure conditions during setting.

[0018] Before withdrawing the tubing string, the kill valve is opened to circulate and kill the well, meeting well control requirements; the telescopic tubing is used to provide a portion of the tubing extension to meet the corresponding tubing string process requirements; during fracturing, the hydraulic anchor is firmly anchored to the casing wall to provide an anchoring point for the tubing string; the packer is used to isolate the target formation downhole; the infinite-stage fracturing sleeve is used to provide a fluid flow channel during stratified fracturing; the safety release connector is used to achieve shear release when the tubing string gets stuck; the setting ball seat is used to provide pressure conditions during setting, and after setting is completed, the ball seat is removed to provide the first-stage fracturing channel.

[0019] Preferably, the packer is a hydraulic compression packer.

[0020] Preferably, the kill valve includes a kill valve body, an inner sliding sleeve assembly, and an opening ball. The inner sliding sleeve assembly is located inside the kill valve body, and the opening ball is located inside the kill valve body. The inner sliding sleeve assembly can slide along the inner wall of the kill valve body, and the opening ball can slide down along the inside of the inner sliding sleeve assembly.

[0021] Preferably, the kill valve body includes an upper connector, a lock screw, and a lower connector; a fluid outlet is provided at the upper center of the upper connector, the upper connector and the lower connector are connected by threads and secured with the lock screw.

[0022] Preferably, the inner sleeve assembly includes a kill valve inner sleeve, a kill valve sealing ring, and an opening shear pin. The upper end of the kill valve inner sleeve has a sloping step, which is fixed in a predetermined closed position using the opening shear pin. The kill valve sealing ring is sleeved on the outside of the kill valve inner sleeve.

[0023] Preferably, the slope of the step at the upper end of the inner sleeve of the kill valve is less than 25 degrees. Only in this way can the deployment and passage of the infinite-stage fracturing sleeve opening tool be ensured during layer replacement operations in the later tubing string process.

[0024] Preferably, the telescopic tube includes a telescopic tube body assembly, a movable assembly, a telescopic tube accessory, and an actuation assembly. The movable assembly is disposed inside the telescopic tube body assembly, and the relative movement of the movable assembly and the telescopic tube body assembly is pre-reserved to realize the tube length compensation function. The telescopic tube accessory is disposed at one end inside the telescopic tube body assembly and is used to connect the telescopic tube body assembly and provide a seal. The actuation assembly is embedded in the side wall of the other end of the telescopic tube body assembly and is connected to the movable assembly. The actuation assembly controls whether the telescopic tube body assembly and the movable assembly move.

[0025] Preferably, the telescopic tube body assembly includes a telescopic tube upper connector, an extension tube, a telescopic tube body, a telescopic tube outer cylinder, and a telescopic tube protective cover; wherein, the telescopic tube upper connector, the extension tube, the telescopic tube body, and the telescopic tube outer cylinder are connected by threads, the upper end of the telescopic tube body has a small liquid passage hole, and the lower end of the telescopic tube body has a locking hole; the upper end of the telescopic tube protective cover has threads and is connected to the telescopic tube body; the telescopic tube outer cylinder and the telescopic tube protective cover are jointly connected to the telescopic tube body by threads.

[0026] Preferably, the movable component includes a limiting cap and a telescopic tube center tube, the lower end of the telescopic tube center tube has a groove, and the limiting cap and the telescopic tube center tube are connected as a whole by threads.

[0027] Preferably, the telescopic tube accessory includes a telescopic tube sealing ring and a telescopic tube anti-loosening screw. The telescopic tube sealing ring is sleeved on the outside of the extension tube and the telescopic tube center tube, and the telescopic tube anti-loosening screw connects the upper connector of the telescopic tube and the extension tube.

[0028] Preferably, the starting assembly includes a starting piston, a starting shear pin, a starting shear ring, and a steel ball. The starting piston is disposed in a reserved space between the telescopic tube body and the telescopic tube outer cylinder. The starting shear pin and the starting shear ring are disposed at one end of the starting piston. The starting shear pin is embedded in the side wall of the telescopic tube outer cylinder. The starting shear ring is connected to the starting shear pin and disposed between the telescopic tube body and the telescopic tube outer cylinder. Part of the steel ball is located in the groove at the lower end of the telescopic tube center tube, and the other part of the steel ball is located in the locking hole at the lower end of the telescopic tube body.

[0029] Preferably, the packer is a hydraulic compression packer, comprising an upper packer connector, a central packer tube, a release shear pin, an upper pressure cap, a packer sealing ring, a sealing unit, a liner, a packer retaining ring, an upper cone, a packer outer cylinder, a locking ring, an anchoring mechanism, a lower cone, a lower packer connector, a packer anti-drop screw, and an anti-seating shear pin; the upper packer connector, the central packer tube, and the lower packer connector are connected; the packer sealing ring is fitted onto the central packer tube; the upper part of the liner is connected to the upper pressure cap; the central packer tube has several fluid passage holes; both the central packer tube and the liner have grooves; the packer retaining ring is engaged in the grooves of the central packer tube and the liner; the sealing unit... The packer is connected to the outer cylinder to form a sealed whole; the upper cone and the lower cone are connected and located inside the outer cylinder of the packer; the upper cone is a piston structure, and the lower cone is connected to the lower end of the liner; the release shear pin is installed in the shear pin hole at the upper end of the upper pressure cap and is positioned with the groove of the packer center tube; the anti-drop screw is fixed in the screw hole at the lower part of the upper cone, and the upper part of the anti-drop screw moves in the slot on the anchoring mechanism; the anti-seating shear pin is installed in the shear pin hole at the lower end of the outer cylinder of the packer and is positioned with the groove on the lower cone; the locking ring is installed between the outer cylinder of the packer and the upper cone to ensure that the outer cylinder of the packer and the upper cone can only move in one direction.

[0030] Preferably, the packer center tube and the packer lower connector are connected by threads, and the upper part of the liner is connected to the upper pressure cap by threads; the side wall of the packer center tube has several liquid passage holes, and the upper part of the side wall of the packer center tube has a groove; the lower end of the liner is an elastic claw structure, and the middle part of the liner has a groove and a liquid passage hole; the packer retaining ring is an open C-shaped elastic ring.

[0031] Preferably, the sealing unit includes a rubber cylinder piston, a rubber cylinder, and a spacer ring. The rubber cylinder has multiple grooves, and the spacer ring is disposed in the grooves of the rubber cylinder. The rubber cylinder piston squeezes the rubber cylinder and the spacer ring to form the sealing unit.

[0032] Preferably, the lower end of the rubber sleeve piston has a threaded structure, which is connected to the outer cylinder of the packer through the threaded structure. The lower end of the liner has a step, and the lower end of the lower cone has a groove inside. The groove inside the lower end of the lower cone matches the step at the lower end of the liner, thereby achieving connection and positioning.

[0033] Preferably, the anchoring mechanism includes a slip, a spring, and a slip holder; the slip and the spring are mounted on the slip holder, the spring is disposed between two slips, the slip holder has a slot, and the upper part of the anti-drop screw moves within the slot on the slip holder.

[0034] Preferably, the locking ring is an open C-shaped elastic ring with a thread on one side and a one-way tooth on the other.

[0035] Preferably, the infinite-level fracturing sleeve includes an infinite-level fracturing sleeve body assembly, an infinite-level fracturing sleeve accessory, and an opening tool assembly. The opening tool assembly is embedded in the side wall of the infinite-level fracturing sleeve body assembly and connected to the infinite-level fracturing sleeve accessory. The opening tool assembly controls whether the infinite-level fracturing sleeve body assembly and the infinite-level fracturing sleeve accessory are movable.

[0036] Preferably, the infinite-level fracturing sleeve body assembly includes an infinite-level fracturing sleeve upper connector, an infinite-level fracturing sleeve body, an infinite-level fracturing sleeve shear pin, an infinite-level fracturing sleeve inner sleeve, an infinite-level fracturing sleeve retaining ring, and an infinite-level fracturing sleeve lower connector; the infinite-level fracturing sleeve upper connector has an internal ramp and is integrally connected to the infinite-level fracturing sleeve body and the infinite-level fracturing sleeve lower connector by threads; the infinite-level fracturing sleeve inner sleeve is pre-positioned at a predetermined position on the infinite-level fracturing sleeve body by the infinite-level fracturing sleeve shear pin; the infinite-level fracturing sleeve retaining ring is sleeved on the outside of the infinite-level fracturing sleeve inner sleeve to prevent the infinite-level fracturing sleeve inner sleeve from moving in the opposite direction.

[0037] Preferably, the infinite-stage fracturing sleeve retainer is a C-shaped elastic open ring.

[0038] Preferably, the opening tool assembly includes: an upper pumping ball, an infinite-stage fracturing sleeve sealing ring, an upper ball seat, an opening tool body, a lower pumping ball, and a lower ball seat; the upper ball seat and the lower ball seat have sealing grooves, the infinite-stage fracturing sleeve sealing ring is installed in the sealing grooves, and the upper ball seat and the lower ball seat are connected to the opening tool body; the opening tool body is a stepped sleeve, the right end face of the step of the opening tool body matches the lower end of the groove of the inner sleeve of the infinite-stage fracturing sleeve, and the upper connector of the infinite-stage fracturing sleeve has a slope inside.

[0039] Preferably, the slope of the ramp inside the joint of the infinite-level fracturing sleeve is less than 25 degrees.

[0040] Preferably, the upper ball seat and the lower ball seat are connected to the opening tool body by screws; the opening tool body is a stepped, hollowed-out metal flexible sleeve.

[0041] Preferably, the safety release connector includes a safety release upper connector, a safety release outer cylinder, a safety release lower connector, a safety release sealing ring, and a safety release scissor pin. The safety release upper connector has an internal ramp, and the safety release upper connector is integrated with the safety release outer cylinder. The safety release upper connector and the safety release lower connector are connected by the safety release scissor pin.

[0042] Preferably, the safety release clip is installed in the threaded hole at the lower end of the safety release outer tube; the safety release upper connector is connected to the safety release outer tube as a whole by threaded connection.

[0043] This invention provides a method for implementing the above-mentioned vertical well unlimited-stage tubing fracturing string process, comprising the following steps:

[0044] Fracturing string insertion: After completing the wellbore preparations for washing, cleaning, and scraping, connect the vertical well unlimited tubing fracturing string, and then, based on the target formation depth, run the vertical well unlimited tubing fracturing string into the predetermined position and set up the wellhead equipment.

[0045] Packer setting: A setting ball is inserted and allowed to sink freely or be pumped to the setting ball seat. At this time, a dead cavity is formed in the tubing string. The wellhead pump truck pressurizes the pressure to the preset pressure P0 to complete the setting of the packer downhole. Then the setting ball is removed to achieve communication between the tubing string and the formation.

[0046] fracture:

[0047] First stage of fracturing: Fracturing fluid is injected and flows out from the tail end of the tubing string into the formation, completing the first stage of fracturing. The working pressure during fracturing is set to P.

[0048] During the fracturing process, the telescopic tube will reach the working pressure P1, thus entering the working state;

[0049] For layer-switching fracturing, the opening tool assembly is deployed from the wellhead, and the pump is moved to the next stage. The pressure is built up to the opening pressure P2 of the infinite-stage fracturing sleeve, and the infinite-stage fracturing sleeve is opened to perform fracturing of the current stage. This process of layer-switching fracturing is repeated to achieve fracturing of all stages.

[0050] Lifting the tubing string load: Drop a ball that matches the kill valve into the wellhead and let it sink naturally to the kill valve. When the pressure of the kill valve reaches P3, open the kill valve and perform circulation kill to the preset qualified standard; lift the tubing string load to the preset unsealing load F0, the downhole packer is unsealed, and the entire well tubing string is pulled out;

[0051] Drop and retrieval: In case of unexpected situations such as sand burial of downhole tools or tubing jamming, the tubing load is raised to the preset drop load F1, then the safety drop connector is sheared, the upper tubing is pulled out, and then the sand flushing and retrieval are carried out in stages.

[0052] Preferably, in implementing the above-described vertical well unlimited-stage tubing fracturing string process, the parameters are set as follows:

[0053] Packer setting and release pressure P0 < fracturing pump pressure P;

[0054] Infinite fracturing sleeve opening pressure P1 <P;

[0055] The well kill valve opening pressure P2 < the fracturing pump pressure P;

[0056] Packer setting and release pressure P0 < telescopic opening pressure P3 < fracturing pump pressure P;

[0057] The fracturing pump pressure P is the maximum design pressure that the tubing string can withstand.

[0058] Unsealing load F0 < Disposal load F1.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] (1) This invention solves the problem of limited number of pressure stages in the existing gradual ball-dropping stage by using an infinite-level fracturing sliding sleeve; at the same time, the fracturing sliding sleeve used is a large-diameter equal-diameter sleeve with no throttling (or minimal throttling effect), which can effectively increase the working pump pressure, solve the problem of limited fracturing scale, and solve the problem of limited number of pressure stages and fracturing scale in the existing vertical well pressure distribution tubing process technology.

[0061] (2) By using a hydraulic telescopic tube installed under the packer, the present invention can provide effective space for unsealing when the tube string is lifted to unseal, so that the packer can be unsealed step by step, reducing the difficulty of unsealing the pressure-dividing tube string.

[0062] (3) By using a safe release connector, the present invention can release the connector and then flush and retrieve the pipe in case of sand burial accident, thus providing the pipe string with sand burial prevention capability and improving the safety of the pressure dividing pipe string. Attached Figure Description

[0063] Figure 1 This is a schematic diagram of a vertical well infinite pressure distribution string structure according to an embodiment of the present invention; the string diagram and tool symbols are drawn according to SY / T5373; all leader lines point to the top of the tool rather than the middle;

[0064] Figure 2 This is a schematic diagram of a well control valve structure in the ball-seated state according to an embodiment of the present invention;

[0065] Figure 3 This is a schematic diagram of the structure of the kill valve in the well entry state according to an embodiment of the present invention;

[0066] Figure 4 This is a schematic diagram of the well control valve in the open state according to an embodiment of the present invention;

[0067] Figure 5 This is a schematic diagram of the telescopic pipe structure in the assembled and inserted state according to an embodiment of the present invention;

[0068] Figure 6 This is a schematic diagram illustrating the working principle of the telescopic tube activation assembly according to an embodiment of the present invention;

[0069] Figure 7 This is a schematic diagram of the telescopic tube in the working state (i.e., the compensation state) according to an embodiment of the present invention;

[0070] Figure 8 (a) and (b) together form a schematic diagram of a hydraulic compression packer structure in the assembled and inserted state of an embodiment of the present invention. (a) and (b) are an integral whole and are each part of a schematic diagram of a hydraulic compression packer structure in the assembled and inserted state of an embodiment of the present invention.

[0071] Figure 9 (a) and (b) together form a schematic diagram of a hydraulic compression packer structure in the setting state of an embodiment of the present invention. (a) and (b) are an integral whole and are each part of a schematic diagram of a hydraulic compression packer structure in the setting state of an embodiment of the present invention.

[0072] Figure 10 (a) and (b) together constitute a schematic diagram of a hydraulic compression packer structure in the unsealed state of an embodiment of the present invention. (a) and (b) are an integral whole and are each part of a schematic diagram of a hydraulic compression packer structure in the unsealed state of an embodiment of the present invention.

[0073] Figure 11 This is a schematic diagram of an infinite-stage fracturing sliding sleeve structure in the well entry state according to an embodiment of the present invention;

[0074] Figure 12 (a) is a structural diagram of the inner sliding sleeve of the infinite-stage fracturing sliding sleeve according to an embodiment of the present invention, and (b) is a partial enlarged view of part B in (a);

[0075] Figure 13 This is a schematic diagram of the opening tool assembly structure of an infinite-stage fracturing sleeve according to an embodiment of the present invention;

[0076] Figure 14(a) is a structural diagram of the opening tool body of an infinite-level fracturing slide sleeve according to an embodiment of the present invention; (b) is a cross-sectional view along the AA direction in (a); (c) is a partial enlarged view at point B in (a); and (d) is a cross-sectional view along the CC direction in (a).

[0077] Figure 15 A schematic diagram illustrating the mismatch between the activation tool component and the infinite-stage fracturing sleeve.

[0078] Figure 16 This is a schematic diagram of the opening tool assembly matching with an infinite-stage fracturing sleeve according to an embodiment of the present invention;

[0079] Figure 17 A schematic diagram of the opening tool assembly opening an infinite-stage fracturing sleeve according to an embodiment of the present invention;

[0080] Figure 18 This is a schematic diagram of a safety release connector structure according to an embodiment of the present invention;

[0081] Figure 19 This is a schematic diagram of the structure of the safety release connector exit section according to an embodiment of the present invention;

[0082] Figure 20 This is a schematic diagram of the downhole portion of the safety release connector according to an embodiment of the present invention;

[0083] Figure 21 This is a flowchart illustrating the process of implementing a vertical well infinite-stage tubing fracturing string according to an embodiment of the present invention.

[0084] In the diagram, 1. Kill valve; 2. Telescopic pipe; 3. Hydraulic anchor; 4. Packer; 5. Infinite-stage fracturing sleeve; 6. Safety release connector; 7. Setting ball seat; 1-a. Kill valve body; 1-b. Inner sleeve assembly; 1-c. Opening ball; 1-a1. Upper connector of kill valve body; 1-a2. Anti-loosening screw of kill valve body; 1-a3. Lower connector of kill valve body; 1-b1. Inner sleeve of kill valve; 1-b2. Kill valve sealing ring; 1-b3. Opening shear pin; 2-a. Telescopic pipe body assembly; 2-b. Moving assembly; 2-c. Telescopic pipe accessories; 2-d. Starting assembly; 2-a1. Telescopic... 2-a2, Extension tube; 2-a3, Telescopic tube body; 2-a4, Telescopic tube outer cylinder; 2-a5, Telescopic tube protective cover; 2-b1, Limiting cap; 2-b2, Telescopic tube center tube; 2-c1, Telescopic tube sealing ring; 2-c2, Telescopic tube anti-loosening screw; 2-d1, Starting piston; 2-d2, Starting shear pin; 2-d3, Starting shear ring; 2-d4, Steel ball; 4-1, Packer upper connector; 4-2, Packer center tube; 4-3, Unsealing shear pin; 4-4, Upper pressure cap; 4-5, Packer sealing ring; 4-6, Liner; 4-7, Rubber sleeve; 4-8, Spacer ring; 4- 9. Packer piston; 4-10. Packer retaining ring; 4-11. Upper cone; 4-12. Packer outer cylinder; 4-13. Locking ring; 4-14. Slip holder; 4-15. Spring; 4-16. Slip; 4-17. Lower cone; 4-18. Packer lower connector; 4-19. Packer anti-drop screw; 4-20. Anti-seating shear pin; 5-a. Infinite-stage fracturing sleeve body assembly; 5-b. Infinite-stage fracturing sleeve accessories; 5-c. Opening tool assembly; 5-a1. Infinite-stage fracturing sleeve upper connector; 5-a2. Infinite-stage fracturing sleeve body; 5-a3. Infinite-stage fracturing sleeve shear pin; 5- a4. Inner sliding sleeve of the infinite-level fracturing sleeve; 5-a5. Snap ring of the infinite-level fracturing sleeve; 5-a6. Lower connector of the infinite-level fracturing sleeve; 5-b1. Anti-loosening screw of the infinite-level fracturing sleeve accessory; 5-b2. Sealing ring of the infinite-level fracturing sleeve accessory; 5-c1. Upper pumping ball; 5-c2. Sealing ring of the infinite-level fracturing sleeve; 5-c3. Upper ball seat; 5-c4. Opening tool body; 5-c5. Lower pumping ball; 5-c6. Lower ball seat; 6-1. Upper safety release upper connector; 6-2. Outer safety release cylinder; 6-3. Lower safety release lower connector; 6-4. Sealing ring of the safety release; 6-5. Safety release shear pin. Detailed Implementation

[0085] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0086] This invention provides a vertical well infinite-stage tubing fracturing string process, wherein the vertical well infinite-stage tubing fracturing string includes: a kill valve 1, a telescopic pipe 2, a hydraulic anchor 3, a packer 4, an infinite-stage fracturing sliding sleeve 5, a safety release connector 6, and a setting ball seat 7.

[0087] The kill valve 1 is located at the top. A hydraulic anchor 3 and a packer 4 are sequentially arranged between the kill valve 1 and the first target formation in the well. The hydraulic anchor 3 is anchored to the inner wall of the casing.

[0088] An infinite-stage fracturing sleeve 5, a safety release connector 6, and a packer 4 are sequentially installed between each downhole target layer and the next downhole target layer. The infinite-stage fracturing sleeve 5 is installed at each downhole target layer to provide a fluid flow channel during stratified fracturing. The infinite-stage fracturing sleeve 5 includes an opening tool assembly 5-c for controlling the opening of the infinite-stage fracturing sleeve 5. The safety release connector 6 can shear and release the sleeve when the tubing is stuck.

[0089] The telescopic pipe 2 is disposed between the packer 4 of each target layer and the infinite fracturing sleeve 5 of the next target layer. The telescopic pipe 2 is also disposed between the kill valve 1 and the hydraulic anchor 3.

[0090] A setting ball seat 7 is installed above the target layer closest to the bottom of the artificial well, and the setting ball seat 7 can provide the pressure-holding conditions during setting.

[0091] According to one specific embodiment of the present invention, the packer 4 is a hydraulic compression packer.

[0092] According to a specific embodiment of the present invention, the kill valve 1 includes a kill valve body 1-a, an inner sliding sleeve assembly 1-b, and an opening ball 1-c. The inner sliding sleeve assembly 1-b is located inside the kill valve body 1-a, and the opening ball 1-c is located inside the kill valve body 1-a. The inner sliding sleeve assembly 1-b is slidable along the inner wall of the kill valve body 1-a, and the opening ball 1-c is slidable down along the inside of the inner sliding sleeve assembly 1-b.

[0093] According to a specific embodiment of the present invention, the kill valve body 1-a includes an upper connector 1-a1, a lock screw 1-a2, and a lower connector 1-a3; a fluid outlet hole is provided in the upper center of the upper connector 1-a1, the upper connector 1-a1 and the lower connector 1-a3 are connected by threads and are fastened by the lock screw 1-a2.

[0094] According to a specific embodiment of the present invention, the inner sliding sleeve assembly 1-b includes a kill valve inner sliding sleeve 1-b1, a kill valve sealing ring 1-b2, and an opening shear pin 1-b3. The upper end of the kill valve inner sliding sleeve 1-b1 has a sloping step, and the opening shear pin 1-b3 is used to fix it in a predetermined closed position. The kill valve sealing ring 1-b2 is sleeved on the outside of the kill valve inner sliding sleeve 1-b1.

[0095] According to a specific embodiment of the present invention, the slope of the step at the upper end of the inner sliding sleeve 1-b1 of the kill valve is less than 25 degrees. Only in this way can the deployment and passage of the infinite-stage fracturing sliding sleeve opening tool be ensured during the layer replacement operation in the subsequent tubing string process.

[0096] Secure the opening clips 1-b3 to the predetermined closed position, in this well-entry state (e.g.) Figure 3 The outlet of the kill valve is closed, preventing communication between the tubing string and the annulus.

[0097] When the tubing string needs to be lifted, the opening ball 1-c is inserted. The opening ball 1-c slides down to the upper end of the inner sliding sleeve, where a sloping step is formed inside the tubing string. When the pressure is reached to the opening pressure of the kill valve, the opening shear pin 1-b3 is sheared. The inner sliding sleeve descends to the step inside the lower connector, and the kill valve opens, allowing communication between the tubing string and the annulus, thus enabling circulating kill conditions.

[0098] The borehole diameter of the kill valve is denoted as D1.

[0099] According to a specific embodiment of the present invention, the telescopic tube 2 includes a telescopic tube body assembly 2-a, a movable component 2-b, a telescopic tube accessory 2-c, and an actuation component 2-d. The movable component 2-b is disposed inside the telescopic tube body assembly 2-a. The movable component 2-b and the telescopic tube body assembly 2-a have a pre-reserved stroke for relative movement, realizing the tube length compensation function. The telescopic tube accessory 2-c is disposed at one end inside the telescopic tube body assembly 2-a and is used to connect the telescopic tube body assembly 2-a and provide a seal. The actuation component 2-d is embedded in the side wall of the other end of the telescopic tube body assembly 2-a and connected to the movable component 2-b. The actuation component 2-d controls whether the telescopic tube body assembly 2-a and the movable component 2-b move.

[0100] According to a specific embodiment of the present invention, the telescopic tube body assembly 2-a includes a telescopic tube upper connector 2-a1, an extension tube head 2-a2, a telescopic tube body 2-a3, a telescopic tube outer cylinder 2-a4, and a telescopic tube protective cover 2-a5; wherein, the telescopic tube upper connector 2-a1, the extension tube head 2-a2, the telescopic tube body 2-a3, and the telescopic tube outer cylinder 2-a4 are connected by threads; the upper end of the telescopic tube body 2-a3 has a small liquid passage hole, and the lower end of the telescopic tube body 2-a3 has a locking hole; the upper end of the telescopic tube protective cover 2-a5 has threads and is connected to the telescopic tube body 2-a3; the telescopic tube outer cylinder 2-a4 and the telescopic tube protective cover 2-a5 are jointly connected to the telescopic tube body 2-a3 by threads.

[0101] According to a specific embodiment of the present invention, the movable component 2-b includes a limiting cap 2-b1 and a telescopic tube center tube 2-b2. The lower end of the telescopic tube center tube 2-b2 has a groove. The limiting cap 2-b1 and the telescopic tube center tube 2-b2 are connected as a whole by threads.

[0102] According to a specific embodiment of the present invention, the telescopic tube accessory 2-c includes a telescopic tube sealing ring 2-c1 and a telescopic tube anti-loosening screw 2-c2. The telescopic tube sealing ring 2-c1 is sleeved on the outside of the extension tube head 2-a2 and the telescopic tube center tube 2-b2, and the telescopic tube anti-loosening screw 2-c2 connects the telescopic tube upper connector 2-a1 and the extension tube head 2-a2.

[0103] According to a specific embodiment of the present invention, the starting assembly 2-d includes a starting piston 2-d1, a starting shear pin 2-d2, a starting shear ring 2-d3, and a steel ball 2-d4. The starting piston 2-d1 is disposed in the reserved space between the telescopic tube body 2-a3 and the telescopic tube outer cylinder 2-a4. The starting shear pin 2-d2 and the starting shear ring 2-d3 are disposed at one end of the starting piston 2-d1. The starting shear pin 2-d2 is embedded in the side wall of the telescopic tube outer cylinder 2-a4. The starting shear ring 2-d3 is connected to the starting shear pin 2-d2 and is disposed between the telescopic tube body 2-a3 and the telescopic tube outer cylinder 2-a4. A portion of the steel ball 2-d4 is located in the groove at the lower end of the telescopic tube center tube 2-b2, and another portion of the steel ball 2-d4 is located in the locking hole at the lower end of the telescopic tube body 2-a3.

[0104] The initiation component 2-d is hydraulically controlled. When the telescopic pipe body assembly 2-a and the movable component 2-b have a relative tendency to move, the steel ball 2-d4 moves radially outward, while the shear ring restricts the space in which the steel ball 2-d4 moves radially. Therefore, the telescopic pipe body assembly 2-a and the movable component 2-b cannot move, completing the assembly and insertion into the well. Figure 5 As shown. The starting piston 2-d1 is positioned in the reserved space between the telescopic tube body 2-a3 and the telescopic tube outer cylinder 2-a4. Pressure from within the tube column is discharged through a small hole on the telescopic tube body 2-a3 and acts on the starting piston 2-d1. When the set value is reached, the starting piston 2-d1 moves downward, pushing the starting shear ring 2-d3 to shear the starting shear pin 2-d2. The starting shear ring 2-d3 then moves downward (as shown). Figure 6 (As shown). At this point, the radial restriction of the shear ring 2-d3 on the steel ball 2-d4 is released, and the steel ball 2-d4 can be squeezed into the internal space of the starting piston 2-d1. The movable component 2-b can then move downward under the action of axial tension, completing the length compensation function. Figure 7As shown. The inner diameter of the expansion joint is denoted as D2.

[0105] The structural features of the downhole tool telescopic tube provided in this invention, including hydraulic opening and tubing compensation functions, form the basis for lifting the tubing string during the operation process. First, the hydraulically opened telescopic tube allows for precise setting of the opening timing during fracturing, preventing premature operation of the telescopic tube from affecting the setting operation. Second, after the telescopic tube is opened, the operation of releasing the packer 4 during tubing string lifting can be done in stages, reducing the axial unsealing load.

[0106] According to a specific embodiment of the present invention, the packer 4 is a hydraulic compression packer, comprising a packer upper connector 4-1, a packer central tube 4-2, a release shear pin 4-3, an upper pressure cap 4-4, a packer sealing ring 4-5, a sealing unit, a liner 4-6, a packer retaining ring 4-10, an upper cone 4-11, a packer outer cylinder 4-12, a locking ring 4-13, an anchoring mechanism, a lower cone 4-17, a packer lower connector 4-18, a packer anti-drop screw 4-19, and an anti-seating shear pin. Nail 4-20; The packer upper connector 4-1, the packer central tube 4-2, and the packer lower connector 4-18 are connected; the packer sealing ring 4-5 is sleeved on the packer central tube 4-2; the upper part of the liner 4-6 is connected to the upper pressure cap 4-4; the packer central tube 4-2 has several liquid passage holes; both the packer central tube 4-2 and the liner 4-6 have grooves; the packer retaining ring 4-10 is engaged with the packer central tube 4-2 and the liner 4-6. The sealing unit is connected to the outer cylinder 4-12 of the packer, forming a sealed whole; the upper cone 4-11 and the lower cone 4-17 are connected and located inside the outer cylinder 4-12 of the packer; the upper cone 4-11 is a piston structure, and the lower cone 4-17 is connected to the lower end of the liner 4-6; the unsealing shear pin 4-3 is installed in the shear pin hole at the upper end of the upper pressure cap 4-4 and is positioned with the groove of the central tube 4-2 of the packer; The anti-drop screw is fixed in the screw hole at the lower part of the upper cone 4-11, and the upper part of the anti-drop screw moves in the groove on the anchoring mechanism; the anti-seating shear pin 4-20 is installed in the shear pin hole at the lower end of the packer outer cylinder 4-12 and is positioned with the groove on the lower cone 4-17; the locking ring 4-13 is installed between the packer outer cylinder 4-12 and the upper cone 4-11 to ensure that the packer outer cylinder 4-12 and the upper cone 4-11 can only move in one direction.

[0107] According to a specific embodiment of the present invention, the packer center tube 4-2 and the packer lower connector 4-18 are connected by threads, and the upper part of the liner 4-6 is connected to the upper pressure cap 4-4 by threads; the side wall of the packer center tube 4-2 has several liquid passage holes, and the upper part of the side wall of the packer center tube 4-2 has a groove; the lower end of the liner 4-6 is an elastic claw structure, and the middle part of the liner 4-6 has a groove and a liquid passage hole; the packer retaining ring 4-10 is an open C-shaped elastic ring.

[0108] According to a specific embodiment of the present invention, the sealing unit includes a rubber sleeve piston 4-9, a rubber sleeve 4-7, and a spacer ring 4-8. The rubber sleeve 4-7 has multiple grooves, and the spacer ring 4-8 is disposed in the grooves of the rubber sleeve 4-7. The rubber sleeve piston 4-9 compresses the rubber sleeve 4-7 and the spacer ring 4-8 to form the sealing unit.

[0109] According to a specific embodiment of the present invention, the lower end of the rubber sleeve piston 4-9 has a threaded structure, which is connected to the outer cylinder 4-12 of the packer through the threaded structure. The lower end of the liner 4-6 has a step, and the lower end of the lower cone 4-17 has a groove inside. The groove inside the lower end of the lower cone 4-17 matches the step at the lower end of the liner 4-6, thereby achieving connection and positioning.

[0110] According to a specific embodiment of the present invention, the anchoring mechanism includes a slip 4-16, a spring 4-15, and a slip bracket 4-14; the slip 4-16 and the spring 4-15 are mounted on the slip bracket 4-14, the spring 4-15 is disposed between two slips 4-16, and the slip bracket 4-14 has a slot, the upper part of the anti-drop screw is movable in the slot on the slip bracket 4-14.

[0111] According to a specific embodiment of the present invention, the locking ring 4-13 is an open C-shaped elastic ring with a thread on one side and a one-way tooth on the other.

[0112] According to a specific embodiment of the present invention, the infinite-level fracturing sleeve 5 includes an infinite-level fracturing sleeve body assembly 5-a, an infinite-level fracturing sleeve accessory 5-b, and an opening tool assembly 5-c. The opening tool assembly 5-c is embedded in the side wall of the infinite-level fracturing sleeve body assembly 5-a and connected to the infinite-level fracturing sleeve accessory 5-b. The opening tool assembly 5-c controls whether the infinite-level fracturing sleeve body assembly 5-a and the infinite-level fracturing sleeve accessory 5-b are movable.

[0113] According to a specific embodiment of the present invention, the infinite-level fracturing sleeve body assembly 5-a includes an infinite-level fracturing sleeve upper connector 5-a1, an infinite-level fracturing sleeve body 5-a2, an infinite-level fracturing sleeve shear pin 5-a3, an infinite-level fracturing sleeve inner sleeve 5-a4, an infinite-level fracturing sleeve retaining ring 5-a5, and an infinite-level fracturing sleeve lower connector 5-a6; the infinite-level fracturing sleeve upper connector 5-a1 has a ramp inside and is connected to the infinite-level fracturing sleeve body 5-a2 and the infinite-level fracturing sleeve lower connector 5-a6 by threads to form an integral unit; the infinite-level fracturing sleeve inner sleeve 5-a4 is pre-positioned on the infinite-level fracturing sleeve body 5-a2 at a predetermined position by the infinite-level fracturing sleeve shear pin 5-a3; the infinite-level fracturing sleeve retaining ring 5-a5 is sleeved on the infinite-level fracturing sleeve inner sleeve 5-a4 to prevent the infinite-level fracturing sleeve inner sleeve 5-a4 from moving in the opposite direction.

[0114] According to a specific embodiment of the present invention, the infinite-stage fracturing sleeve retaining ring 5-a5 is a C-shaped elastic open ring.

[0115] According to a specific embodiment of the present invention, the opening tool assembly 5-c includes: an upper pumping ball 5-c1, an infinite-stage fracturing sleeve sealing ring 5-c2, an upper ball seat 5-c3, an opening tool body 5-c4, a lower pumping ball 5-c5, and a lower ball seat 5-c6; the upper ball seat 5-c3 and the lower ball seat 5-c6 have sealing grooves, the infinite-stage fracturing sleeve sealing ring 5-c2 is installed in the sealing grooves, the upper ball seat 5-c3 and the lower ball seat 5-c6 are connected to the opening tool body 5-c4; the opening tool body 5-c4 is a stepped sleeve, the right end face of the step of the opening tool body 5-c4 matches the lower end of the groove of the inner sleeve 5-a4 of the infinite-stage fracturing sleeve, and the upper connector 5-a1 of the infinite-stage fracturing sleeve has a slope inside.

[0116] The outer circumference of the inner sliding sleeve 5-a4 of the infinite-stage fracturing sleeve is provided with sealing grooves and shear pin grooves. The inner circumference is designed with special groove features. This groove is a groove with a negative angle, that is, compared with a straight step, the angle between the step surface and the radial direction is less than 90 degrees. The inner diameter of the groove is denoted as D5-2, and the groove length is denoted as H. Figure 12 As shown. The nominal diameter of the inner sliding sleeve 5-a4 of the infinite-stage fracturing sleeve is denoted as D5-1.

[0117] The opening tool body 5-c4 is a stepped sleeve, preferably a hollowed-out flexible metal sleeve, whose right end face of the step matches the lower end of the groove of the inner sleeve 5-a4 of the infinite-stage fracturing sleeve. See Figure 14The outer diameter of the flexible step is denoted as d5-1, and the step length is denoted as h. The outer sealing surface diameters of the upper ball seat 5-c3 and the lower ball seat 5-c6 are the same, denoted as d5-2. All dimensions satisfy: d5-2=d5=D5-1 <d5-1<D5-1。

[0118] After the opening tool assembly 5-c is inserted into the tubing, it is pumped to the upper connector and introduced into the tool via the ramp there. As described above, the sealing dimension d5-2 of the front and rear ball seats of the opening tool assembly 5-c is the same as the bore diameter D5-1 of the inner sleeve 5-a4 of the infinite fracturing sleeve, forming a seal at this point. Since the upper pumping ball 5-c1 and the lower pumping ball 5-c5 block the downward flow channel of the liquid, under the axial force generated by the liquid, the flexible step on the opening tool body 5-c4 is radially compressed, and the diameter d-51 decreases to d5, entering the inner hole of the inner sleeve 5-a4 of the infinite fracturing sleeve.

[0119] When the length h of the flexible step on the opening tool body 5-c4 is greater than the length H of the inner groove of the infinite-stage fracturing sleeve 5-a4, the opening tool assembly 5-c continues to pass through the inner hole of the infinite-stage fracturing sleeve 5, such as... Figure 15 As shown; conversely, the groove on the opening tool body 5-c4 engages with the inner groove of the inner sleeve 5-a4 of the infinite-stage fracturing sleeve. For example... Figure 16 As shown.

[0120] The structure of the infinite-stage fracturing sleeve 5 in this invention forms the basis for layer-swapping fracturing. The infinite-stage fracturing method used in this invention can achieve full-bore and equal-bore tubing.

[0121] At this point, under the action of liquid pressure, the opening tool assembly 5-c will descend along with the inner sliding sleeve 5-a4 of the infinite-stage fracturing sleeve, shearing the infinite-stage fracturing sleeve shear pin 5-a3, and descending to the designed position. At this time, the infinite-stage fracturing sleeve 5 opens and enters the working state, as shown below. Figure 17 As shown. The infinite-stage fracturing sleeve retaining ring 5-a5 is a C-shaped elastic open ring. After being compressed in diameter, it will be installed and will then return to its larger diameter to prevent the inner sleeve 5-a4 of the infinite-stage fracturing sleeve from moving in the opposite direction and accidentally closing the sleeve.

[0122] According to one specific embodiment of the present invention, the slope of the ramp inside the joint 5-a1 of the infinite-level fracturing sleeve is less than 25 degrees.

[0123] According to a specific embodiment of the present invention, the upper ball seat 5-c3 and the lower ball seat 5-c6 are connected to the opening tool body 5-c4 by screws; the opening tool body 5-c4 is a stepped hollow metal flexible sleeve.

[0124] According to a specific embodiment of the present invention, the safety release connector 6 includes a safety release upper connector 6-1, a safety release outer cylinder 6-2, a safety release lower connector 6-3, a safety release sealing ring 6-4, and a safety release scissor pin 6-5. The safety release upper connector 6-1 has an internal slope, and the safety release upper connector 6-1 is integrally connected with the safety release outer cylinder 6-2. The safety release upper connector 6-1 and the safety release lower connector 6-3 are connected by the safety release scissor pin 6-5.

[0125] According to a specific embodiment of the present invention, the safety release scissor 6-5 is installed in the threaded hole at the lower end of the safety release outer tube 6-2; the safety release upper connector 6-1 and the safety release outer tube 6-2 are connected as one unit by thread.

[0126] When the tubing string becomes stuck, raise the load on the tubing string to the predetermined load, and shear the safety release shear pin 6-5. Then, the upper part of the safety release upper connector 6-1 and the safety release outer cylinder 6-2 can be lifted out. Figure 19 As shown; however, the safety release connector 6-3 remains downhole. A standard tubing thread is pre-installed at the upper end of the connector for later retrieval. (See diagram). Figure 20 As shown. The nominal diameter of the safety release connector 6 is denoted as D6.

[0127] In this invention, the downhole tool safety release connector 6 is the guarantee for both release and retrieval. The shear-type safety release connector 6 allows for timely release when the tubing is buried in sand, while the pre-drilled retrieval threads on the safety release connector 6 facilitate subsequent retrieval using general-purpose retrieval tools. Furthermore, the pure shear-type safety connector reduces the number of retrieval attempts. Because the shear load F1 > the unsealing load F0, if the packer 4 can be unsealed normally and the tubing can be lifted normally, the safety connector will not shear, reducing the number of retrieval attempts. If other methods are used, such as hydraulic opening, the safety connector will release regardless of whether the tubing is stuck, increasing the number of retrieval attempts.

[0128] This invention provides a method for implementing the above-mentioned vertical well unlimited-stage tubing fracturing string process, comprising the following steps:

[0129] Fracturing string insertion: After completing the wellbore preparations for washing, cleaning, and scraping, connect the vertical well unlimited tubing fracturing string, and then, based on the target formation depth, run the vertical well unlimited tubing fracturing string into the predetermined position and set up the wellhead equipment.

[0130] Packer 4 setting: A setting ball is inserted and allowed to sink freely or be pumped to the setting ball seat 7. At this time, a dead cavity is formed in the tubing string. The wellhead pump truck pressurizes the pressure to the preset pressure P0 to complete the setting of the packer 4 downhole. Then the setting ball is removed to achieve communication between the tubing string and the formation.

[0131] fracture:

[0132] First stage of fracturing: Fracturing fluid is injected and flows out from the tail end of the tubing string into the formation, completing the first stage of fracturing. The working pressure during fracturing is set to P.

[0133] During the fracturing process, the telescopic tube 2 will reach the working pressure P1, thus entering the working state;

[0134] For layer-switching fracturing, the opening tool assembly 5-c is deployed from the wellhead to pump to the next stage, pressurize to the opening pressure P2 of the infinite-stage fracturing sleeve 5, open the infinite-stage fracturing sleeve 5, and perform fracturing of the current layer; repeat the layer-switching fracturing process to achieve fracturing of all stages;

[0135] Lifting the tubing string load: Drop a ball that matches the kill valve 1 from the wellhead, let it sink naturally to the kill valve 1, pressurize it until the pressure of the kill valve 1 is P3, open the kill valve 1, and perform circulation kill to the preset qualified standard; lift the tubing string load to the preset unsealing load F0, the downhole packer 4 is unsealed, and the entire well tubing string is pulled out;

[0136] Drop and retrieval: In case of unexpected situations such as downhole tools being buried in sand or the tubing getting stuck, the tubing load is raised to the preset drop load F1, then the safety drop connector 6 is sheared, the upper tubing is pulled out, and then the sand is flushed and retrieved step by step.

[0137] According to a specific embodiment of the present invention, in the process of implementing the vertical well unlimited tubing fracturing string process, the parameters are set as follows:

[0138] Packer 4 setting pressure P0 < fracturing pump pressure P;

[0139] Infinite-stage fracturing sleeve 5 opening pressure P1 <P;

[0140] Well kill valve 1 opening pressure P2 < fracturing pump pressure P;

[0141] Packer 4 setting pressure P0 < telescopic opening pressure P3 < fracturing pump pressure P;

[0142] The fracturing pump pressure P is the maximum design pressure that the tubing string can withstand.

[0143] Unsealing load F0 < Disposal load F1.

[0144] Sealing process:

[0145] After pressure builds up inside the tubing, liquid enters the liner 4-6 through the hole in the packer's central tube 4-2, and the liquid pressure is applied to the rubber sleeve piston 4-9 and the upper cone 4-11 through the liquid orifice. The rubber sleeve piston 4-9 compresses the rubber sleeve 4-7 and the spacer ring 4-8 to form a sealing unit, filling the annular spacer and achieving a seal. Simultaneously, the liquid pressure pushes the upper cone 4-11 downward, compressing the slip 4-16. Under the action of the lower cone 4-17, the slip 4-16 compresses the spring 4-15, moving radially outward and biting into the sleeve, achieving anchoring. Due to the unidirectional structure of the locking ring 4-13, the packer outer cylinder 4-12 and the upper cone 4-11 cannot move in opposite directions, maintaining the setting state even after the setting pressure is released. Figure 9 As shown.

[0146] The process of lifting the lockdown:

[0147] Raise the tubing to the predetermined load, shear off the release pin 4-3, and the packer upper connector 4-1, packer center tube 4-2, and packer lower connector 4-18 move upwards. The packer center tube 4-2 moves to the lower step of the liner 4-6, causing the liner 4-6 to move upwards. Since the upper pressure cap 4-4 is integrated with it, it also moves upwards, releasing the ballast on the rubber sleeve 4-7, which then returns to its original position. Simultaneously, the packer retaining ring 4-10 on the liner 4-6 moves the rubber sleeve piston 4-9 and the packer outer cylinder 4-12 upwards together. Due to the one-way structure of the locking ring 4-13, the upper cone 4-11 also moves upwards, thus removing the ballast on the slip 4-16. Under the action of the spring 4-15, the slip contracts radially inwards, releasing the anchor. At this point, the release is complete. Figure 10 As shown.

[0148] In this invention, the structure of packer 4 ensures packer setting and the load capacity of the tubing string. First, using the same type of hydraulic packer throughout the well, and employing the same setting method, guarantees successful setting of all packers 4 on the first attempt, regardless of the number of packers 4. Second, the same lifting and unsealing method ensures simple unsealing operation and improves the success rate of unsealing.

[0149] Example 1

[0150] According to a specific embodiment of the present invention, the vertical well unlimited tubing fracturing string process of the present invention will be described in detail below.

[0151] This invention provides a vertical well infinite-stage tubing fracturing string process, wherein the vertical well infinite-stage tubing fracturing string includes: a kill valve 1, a telescopic pipe 2, a hydraulic anchor 3, a packer 4, an infinite-stage fracturing sliding sleeve 5, a safety release connector 6, and a setting ball seat 7.

[0152] The kill valve 1 is located at the top. A hydraulic anchor 3 and a packer 4 are sequentially arranged between the kill valve 1 and the first target formation in the well. The hydraulic anchor 3 is anchored to the inner wall of the casing.

[0153] An infinite-stage fracturing sleeve 5, a safety release connector 6, and a packer 4 are sequentially installed between each downhole target layer and the next downhole target layer. The infinite-stage fracturing sleeve 5 is installed at each downhole target layer to provide a fluid flow channel during stratified fracturing. The infinite-stage fracturing sleeve 5 includes an opening tool assembly 5-c for controlling the opening of the infinite-stage fracturing sleeve 5. The safety release connector 6 can shear and release the sleeve when the tubing is stuck.

[0154] The telescopic pipe 2 is disposed between the packer 4 of each target layer and the infinite fracturing sleeve 5 of the next target layer. The telescopic pipe 2 is also disposed between the kill valve 1 and the hydraulic anchor 3.

[0155] A setting ball seat 7 is installed above the target layer closest to the bottom of the artificial well, and the setting ball seat 7 can provide the pressure-holding conditions during setting.

[0156] Example 2

[0157] Unlike Example 1, this example employs infinite-level pressure distribution, utilizing a special fracturing sleeve to achieve infinite-level pressure distribution in vertical wells, resulting in simple and efficient layer-changing operations. The downhole tools in contact with the opening tool have specific requirements for their diameter (greater than the outer diameter d5-1 of the opening tool step or equal to the outer diameter d5-2 of the opening tool body) to ensure smooth passage of the opening tool.

[0158] The infinite-level fracturing slide sleeve 5 includes an infinite-level fracturing slide sleeve body assembly 5-a, an infinite-level fracturing slide sleeve accessory 5-b, and an opening tool assembly 5-c. The opening tool assembly 5-c is embedded in the side wall of the infinite-level fracturing slide sleeve body assembly 5-a and connected to the infinite-level fracturing slide sleeve accessory 5-b. The opening tool assembly 5-c controls whether the infinite-level fracturing slide sleeve body assembly 5-a and the infinite-level fracturing slide sleeve accessory 5-b are movable.

[0159] The infinite-level fracturing sleeve body assembly 5-a includes an infinite-level fracturing sleeve upper connector 5-a1, an infinite-level fracturing sleeve body 5-a2, an infinite-level fracturing sleeve shear pin 5-a3, an infinite-level fracturing sleeve inner sleeve 5-a4, an infinite-level fracturing sleeve retaining ring 5-a5, and an infinite-level fracturing sleeve lower connector 5-a6. The infinite-level fracturing sleeve upper connector 5-a1 has an internal ramp and is connected to the infinite-level fracturing sleeve body 5-a2 and the infinite-level fracturing sleeve lower connector 5-a6 by threads. The infinite-level fracturing sleeve inner sleeve 5-a4 is pre-positioned on the infinite-level fracturing sleeve body 5-a2 by the infinite-level fracturing sleeve shear pin 5-a3. The infinite-level fracturing sleeve retaining ring 5-a5 is sleeved on the infinite-level fracturing sleeve inner sleeve 5-a4 to prevent the infinite-level fracturing sleeve inner sleeve 5-a4 from moving in the opposite direction.

[0160] The infinite-level fracturing sliding sleeve retainer 5-a5 is a C-shaped elastic open ring.

[0161] The opening tool assembly 5-c includes: an upper pumping ball 5-c1, an infinite-stage fracturing sleeve sealing ring 5-c2, an upper ball seat 5-c3, an opening tool body 5-c4, a lower pumping ball 5-c5, and a lower ball seat 5-c6; the upper ball seat 5-c3 and the lower ball seat 5-c6 have sealing grooves, and the infinite-stage fracturing sleeve sealing ring 5-c2 is installed in the sealing grooves; the upper ball seat 5-c3 and the lower ball seat 5-c6 are connected to the opening tool body 5-c4; the opening tool body 5-c4 is a stepped sleeve, and the right end face of the step of the opening tool body 5-c4 matches the lower end of the groove of the inner sleeve 5-a4 of the infinite-stage fracturing sleeve; the upper connector 5-a1 of the infinite-stage fracturing sleeve has a slope inside.

[0162] The outer circumference of the inner sliding sleeve 5-a4 of the infinite-stage fracturing sleeve is provided with sealing grooves and shear pin grooves. The inner circumference is designed with special groove features. This groove is a groove with a negative angle, that is, compared with a straight step, the angle between the step surface and the radial direction is less than 90 degrees. The inner diameter of the groove is denoted as D5-2, and the groove length is denoted as H. Figure 12 As shown. The nominal diameter of the inner sliding sleeve 5-a4 of the infinite-stage fracturing sleeve is denoted as D5-1.

[0163] The opening tool body 5-c4 is a stepped sleeve, preferably a hollowed-out flexible metal sleeve, whose right end face of the step matches the lower end of the groove of the inner sleeve 5-a4 of the infinite-stage fracturing sleeve. See Figure 14 The outer diameter of the flexible step is denoted as d5-1, and the step length is denoted as h. The outer sealing surface diameters of the upper ball seat 5-c3 and the lower ball seat 5-c6 are the same, denoted as d5-2. All dimensions satisfy: d5-2=d5=D5-1 <d5-1<D5-1。

[0164] After the opening tool assembly 5-c is inserted into the tubing, it is pumped to the upper connector and introduced into the tool via the ramp there. As described above, the sealing dimension d5-2 of the front and rear ball seats of the opening tool assembly 5-c is the same as the bore diameter D5-1 of the inner sleeve 5-a4 of the infinite fracturing sleeve, forming a seal at this point. Since the upper pumping ball 5-c1 and the lower pumping ball 5-c5 block the downward flow channel of the liquid, under the axial force generated by the liquid, the flexible step on the opening tool body 5-c4 is radially compressed, and the diameter d-51 decreases to d5, entering the inner hole of the inner sleeve 5-a4 of the infinite fracturing sleeve.

[0165] When the length h of the flexible step on the opening tool body 5-c4 is greater than the length H of the inner groove of the infinite-stage fracturing sleeve 5-a4, the opening tool assembly 5-c continues to pass through the inner hole of the infinite-stage fracturing sleeve 5, such as... Figure 15 As shown; conversely, the groove on the opening tool body 5-c4 engages with the inner groove of the inner sleeve 5-a4 of the infinite-stage fracturing sleeve. For example... Figure 16 As shown.

[0166] The structure of the infinite-stage fracturing sleeve 5 in this embodiment is the basis for layer-swapping fracturing. The infinite-stage fracturing method used in this invention can achieve full-bore and equal-bore tubing.

[0167] At this point, under the action of liquid pressure, the opening tool assembly 5-c will descend along with the inner sliding sleeve 5-a4 of the infinite-stage fracturing sleeve, shearing the infinite-stage fracturing sleeve shear pin 5-a3, and descending to the designed position. At this time, the infinite-stage fracturing sleeve 5 opens and enters the working state, as shown below. Figure 17 As shown. The infinite-stage fracturing sleeve retaining ring 5-a5 is a C-shaped elastic open ring. After being compressed in diameter, it will be installed and will then return to its larger diameter to prevent the inner sleeve 5-a4 of the infinite-stage fracturing sleeve from moving in the opposite direction and accidentally closing the sleeve.

[0168] Among them, the slope of the ramp inside the joint 5-a1 of the infinite-level fracturing sleeve is less than 25 degrees.

[0169] The upper ball seat 5-c3 and the lower ball seat 5-c6 are connected to the opening tool body 5-c4 by screws; the opening tool body 5-c4 is a stepped, hollowed-out metal flexible sleeve.

[0170] Example 3

[0171] Unlike Example 1, this example achieves single-operation tubing setting. Multiple hydraulically compressed packers of the same specifications are used in the downhole system, and all packers are set in a single pressurization operation, ensuring a simple, safe, and reliable tubing setting operation. Furthermore, the packer setting is completed before the fracturing operation.

[0172] In this embodiment, the packer 4 is a hydraulic compression packer, including a packer upper connector 4-1, a packer central tube 4-2, a release shear pin 4-3, an upper pressure cap 4-4, a packer sealing ring 4-5, a sealing unit, a liner 4-6, a packer retaining ring 4-10, an upper cone 4-11, a packer outer cylinder 4-12, a locking ring 4-13, an anchoring mechanism, a lower cone 4-17, a packer lower connector 4-18, a packer anti-drop screw 4-19, and an anti-seating shear pin 4-20; The packer upper connector 4-1, the packer center tube 4-2, and the packer lower connector 4-18 are connected. The packer sealing ring 4-5 is fitted onto the packer center tube 4-2. The upper part of the liner 4-6 is connected to the upper pressure cap 4-4. The packer center tube 4-2 has several liquid passage holes. Both the packer center tube 4-2 and the liner 4-6 have grooves. The packer retaining ring 4-10 is engaged with the packer center tube 4-2 and the liner 4-6. The sealing unit is connected to the outer cylinder 4-12 of the packer to form a sealed whole; the upper cone 4-11 and the lower cone 4-17 are connected and located inside the outer cylinder 4-12 of the packer; the upper cone 4-11 is a piston structure, and the lower cone 4-17 is connected to the lower end of the liner 4-6; the unsealing shear pin 4-3 is installed in the shear pin hole at the upper end of the upper pressure cap 4-4 and is positioned with the groove of the central tube 4-2 of the packer; the anti- The anti-drop screw is fixed in the screw hole at the lower part of the upper cone 4-11, and the upper part of the anti-drop screw moves in the groove on the anchoring mechanism; the anti-seating shear pin 4-20 is installed in the shear pin hole at the lower end of the packer outer cylinder 4-12 and is positioned with the groove on the lower cone 4-17; the locking ring 4-13 is installed between the packer outer cylinder 4-12 and the upper cone 4-11 to ensure that the packer outer cylinder 4-12 and the upper cone 4-11 can only move in one direction.

[0173] The packer center tube 4-2 and the packer lower connector 4-18 are connected by threads, and the upper part of the liner 4-6 is connected to the upper pressure cap 4-4 by threads. The side wall of the packer center tube 4-2 has several liquid passage holes, and the upper part of the side wall of the packer center tube 4-2 has a groove. The lower end of the liner 4-6 is an elastic claw structure, and the middle part of the liner 4-6 has a groove and a liquid passage hole. The packer retaining ring 4-10 is an open C-shaped elastic ring.

[0174] The sealing unit includes a rubber cylinder piston 4-9, a rubber cylinder 4-7, and a spacer ring 4-8. The rubber cylinder 4-7 has multiple grooves, and the spacer ring 4-8 is disposed in the grooves of the rubber cylinder 4-7. The rubber cylinder piston 4-9 squeezes the rubber cylinder 4-7 and the spacer ring 4-8 to form the sealing unit.

[0175] The lower end of the rubber sleeve piston 4-9 has a threaded structure, which connects to the outer cylinder 4-12 of the packer through the threaded structure. The lower end of the liner 4-6 has a step, and the lower end of the lower cone 4-17 has a groove inside. The groove inside the lower end of the lower cone 4-17 matches the step at the lower end of the liner 4-6, thus achieving connection and positioning.

[0176] The anchoring mechanism includes a slip 4-16, a spring 4-15, and a slip bracket 4-14. The slip 4-16 and the spring 4-15 are mounted on the slip bracket 4-14. The spring 4-15 is disposed between two slips 4-16. The slip bracket 4-14 has a slot, and the upper part of the anti-drop screw moves within the slot on the slip bracket 4-14.

[0177] The locking ring 4-13 is an open C-shaped elastic ring with a thread on one side and a one-way tooth on the other.

[0178] Example 4

[0179] According to a specific embodiment of the present invention, the implementation method of the above-mentioned vertical well infinite-stage tubing fracturing string process is described in detail below.

[0180] This invention provides a method for implementing the above-mentioned vertical well unlimited-stage tubing fracturing string process, comprising the following steps:

[0181] Fracturing string insertion: After completing the wellbore preparations for washing, cleaning, and scraping, connect the vertical well unlimited tubing fracturing string, and then, based on the target formation depth, run the vertical well unlimited tubing fracturing string into the predetermined position and set up the wellhead equipment.

[0182] Packer 4 setting: A setting ball is inserted and allowed to sink freely or be pumped to the setting ball seat 7. At this time, a dead cavity is formed in the tubing string. The wellhead pump truck pressurizes the pressure to the preset pressure P0 to complete the setting of the packer 4 downhole. Then the setting ball is removed to achieve communication between the tubing string and the formation.

[0183] fracture:

[0184] First stage of fracturing: Fracturing fluid is injected and flows out from the tail end of the tubing string into the formation, completing the first stage of fracturing. The working pressure during fracturing is set to P.

[0185] During the fracturing process, the telescopic tube 2 will reach the working pressure P1, thus entering the working state;

[0186] For layer-switching fracturing, the opening tool assembly 5-c is deployed from the wellhead to pump to the next stage, pressurize to the opening pressure P2 of the infinite-stage fracturing sleeve 5, open the infinite-stage fracturing sleeve 5, and perform fracturing of the current layer; repeat the layer-switching fracturing process to achieve fracturing of all stages;

[0187] Lifting the tubing string load: Drop a ball that matches the kill valve 1 from the wellhead, let it sink naturally to the kill valve 1, pressurize it until the pressure of the kill valve 1 is P3, open the kill valve 1, and perform circulation kill to the preset qualified standard; lift the tubing string load to the preset unsealing load F0, the downhole packer 4 is unsealed, and the entire well tubing string is pulled out;

[0188] Drop and retrieval: In case of unexpected situations such as downhole tools being buried in sand or the tubing getting stuck, the tubing load is raised to the preset drop load F1, then the safety drop connector 6 is sheared, the upper tubing is pulled out, and then the sand is flushed and retrieved step by step.

[0189] This embodiment implements tubing string compensation. The telescopic tube at the upper end of the tubing string provides expansion and contraction compensation during fracturing, ensuring the safety of the fracturing tubing string; the telescopic tube between the packers is activated during fracturing, which can provide a certain stroke at the lower part of the packer when the tubing string is lifted, reducing the unsealing load and enabling step-by-step unsealing.

[0190] Meanwhile, this embodiment employs a shear-type safety release connector, which opens under axial load in case of accidents such as tool burial in sand. This provides the possibility of tiered retrieval. Furthermore, using axial load instead of hydraulic opening is consistent with the packer release method, ensuring opening only when necessary and minimizing unnecessary retrieval attempts.

[0191] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A vertical well unlimited-stage tubing fracturing string process, characterized in that, The vertical well unlimited-stage tubing fracturing string includes: kill valve, telescopic pipe, hydraulic anchor, packer, unlimited-stage fracturing sliding sleeve, safety release joint and setting ball seat; The kill valve is located at the top, and a hydraulic anchor and a packer are sequentially installed between the kill valve and the first target formation in the well; the hydraulic anchor is anchored to the inner wall of the casing. An infinite-stage fracturing sleeve, a safety release connector, and a packer are sequentially installed between each downhole target layer and the next downhole target layer. The infinite-stage fracturing sleeve is located at each downhole target layer to provide a fluid flow channel during stratified fracturing. The infinite-stage fracturing sleeve includes an opening tool assembly for controlling the opening of the infinite-stage fracturing sleeve, and the safety release connector can shear and release the sleeve when the tubing string becomes stuck. The telescopic pipe is installed between the packer of each target layer and the infinite-stage fracturing sleeve of the next target layer, and the telescopic pipe is also installed between the kill valve and the hydraulic anchor; A setting ball seat is installed above the target layer closest to the bottom of the artificial well, and the setting ball seat can provide the pressure-holding conditions during setting. The packer is a hydraulic compression packer, comprising an upper packer connector, a central packer tube, a release shear pin, an upper pressure cap, a packer sealing ring, a sealing unit, a liner, a packer retaining ring, an upper cone, a packer outer cylinder, a locking ring, an anchoring mechanism, a lower cone, a lower packer connector, a packer anti-drop screw, and an anti-seating shear pin. The upper packer connector, the central packer tube, and the lower packer connector are connected. The packer sealing ring is fitted onto the central packer tube. The upper part of the liner is connected to the upper pressure cap. The central packer tube has several fluid passage holes. Both the central packer tube and the liner have grooves. The packer retaining ring is engaged within the grooves of the central packer tube and the liner. The sealing unit and... The packer outer cylinder is connected to form a sealed whole; the upper cone and the lower cone are connected and located inside the packer outer cylinder; the upper cone is a piston structure, and the lower cone is connected to the lower end of the liner; the release shear pin is installed in the shear pin hole at the upper end of the upper pressure cap and is positioned with the groove of the packer center tube; the anti-drop screw is fixed in the screw hole at the lower part of the upper cone, and the upper part of the anti-drop screw moves in the slot on the anchoring mechanism; the anti-seating shear pin is installed in the shear pin hole at the lower end of the packer outer cylinder and is positioned with the groove on the lower cone; the locking ring is installed between the packer outer cylinder and the upper cone to ensure that the packer outer cylinder and the upper cone can only move in one direction.

2. The vertical well unlimited-stage tubing fracturing string process according to claim 1, characterized in that, The kill valve includes a kill valve body, an inner sliding sleeve assembly, and an opening ball. The inner sliding sleeve assembly is located inside the kill valve body, and the opening ball is located inside the kill valve body. The inner sliding sleeve assembly can slide along the inner wall of the kill valve body, and the opening ball can slide down along the inside of the inner sliding sleeve assembly.

3. The vertical well unlimited-stage tubing fracturing string process according to claim 2, characterized in that, The kill valve body includes an upper connector, a lock screw, and a lower connector. A fluid outlet is provided at the center of the upper connector. The upper connector and the lower connector are connected by a thread and secured with the lock screw.

4. The vertical well unlimited-stage tubing fracturing string process according to claim 3, characterized in that, The inner sleeve assembly includes a kill valve inner sleeve, a kill valve sealing ring, and an opening shear pin. The upper end of the kill valve inner sleeve has a sloping step, which is fixed in a predetermined closed position using the opening shear pin. The kill valve sealing ring is sleeved on the outside of the kill valve inner sleeve.

5. The vertical well unlimited-stage tubing fracturing string process according to claim 4, characterized in that, The slope of the upper step of the inner sleeve of the well control valve is less than 25 degrees.

6. The vertical well unlimited-stage tubing fracturing string process according to claim 1, characterized in that, The telescopic tube includes a telescopic tube body assembly, a movable assembly, a telescopic tube accessory, and an actuation assembly. The movable assembly is disposed inside the telescopic tube body assembly. The movable assembly and the telescopic tube body assembly have a pre-reserved stroke for relative movement, realizing the tube length compensation function. The telescopic tube accessory is disposed at one end inside the telescopic tube body assembly and is used to connect to the telescopic tube body assembly and provide a seal. The actuation assembly is embedded in the side wall of the other end of the telescopic tube body assembly and is connected to the movable assembly. The actuation assembly controls whether the telescopic tube body assembly and the movable assembly move.

7. The vertical well unlimited-stage tubing fracturing string process according to claim 6, characterized in that, The telescopic tube body assembly includes a telescopic tube upper connector, an extension tube, a telescopic tube body, a telescopic tube outer cylinder, and a telescopic tube protective cover; wherein, the telescopic tube upper connector, the extension tube, the telescopic tube body, and the telescopic tube outer cylinder are connected by threads, the upper end of the telescopic tube body has a small liquid passage hole, and the lower end of the telescopic tube body has a locking hole; the upper end of the telescopic tube protective cover has threads and is connected to the telescopic tube body; the telescopic tube outer cylinder and the telescopic tube protective cover are connected to the telescopic tube body by threads.

8. The vertical well unlimited-stage tubing fracturing string process according to claim 7, characterized in that, The movable component includes a limiting cap and a telescopic tube center tube. The lower end of the telescopic tube center tube has a groove. The limiting cap and the telescopic tube center tube are connected as a whole by threads.

9. The vertical well unlimited-stage tubing fracturing string process according to claim 8, characterized in that, The telescopic tube accessory includes a telescopic tube sealing ring and a telescopic tube anti-loosening screw. The telescopic tube sealing ring is sleeved on the outside of the extension tube and the telescopic tube center tube, and the telescopic tube anti-loosening screw connects the upper connector of the telescopic tube and the extension tube.

10. The vertical well unlimited-stage tubing fracturing string process according to claim 9, characterized in that, The starting assembly includes a starting piston, a starting shear pin, a starting shear ring, and a steel ball. The starting piston is disposed in the reserved space between the telescopic tube body and the telescopic tube outer cylinder. The starting shear pin and the starting shear ring are disposed at one end of the starting piston. The starting shear pin is embedded in the side wall of the telescopic tube outer cylinder. The starting shear ring is connected to the starting shear pin and is disposed between the telescopic tube body and the telescopic tube outer cylinder. Part of the steel ball is located in the groove at the lower end of the telescopic tube center tube, and the other part of the steel ball is located in the locking hole at the lower end of the telescopic tube body.

11. The vertical well unlimited-stage tubing fracturing string process according to claim 1, characterized in that, The packer center tube and the packer lower connector are connected by threads, and the upper part of the liner is connected to the upper pressure cap by threads; the side wall of the packer center tube has several liquid passage holes, and the upper part of the side wall of the packer center tube has a groove; the lower end of the liner is an elastic claw structure, and the middle part of the liner has a groove and a liquid passage hole; the packer retaining ring is an open C-shaped elastic ring.

12. The vertical well unlimited-stage tubing fracturing string process according to claim 1, characterized in that, The sealing unit includes a rubber cylinder piston, a rubber cylinder, and a spacer ring. The rubber cylinder has multiple grooves, and the spacer ring is disposed in the grooves of the rubber cylinder. The rubber cylinder piston squeezes the rubber cylinder and the spacer ring to form the sealing unit.

13. The vertical well unlimited-stage tubing fracturing string process according to claim 12, characterized in that, The lower end of the rubber sleeve piston has a threaded structure, which connects to the outer cylinder of the packer through the threaded structure. The lower end of the liner has a step, and the lower end of the lower cone has a groove inside. The groove inside the lower end of the lower cone matches the step at the lower end of the liner, thus achieving connection and positioning.

14. The vertical well unlimited-stage tubing fracturing string process according to claim 1, characterized in that, The anchoring mechanism includes a slip, a spring, and a slip holder; the slip and the spring are mounted on the slip holder, the spring is disposed between two slips, and the slip holder has a slot, the upper part of which of the anti-drop screw moves within the slot on the slip holder.

15. The vertical well unlimited-stage tubing fracturing string process according to claim 1, characterized in that, The locking ring is an open C-shaped elastic ring with a thread on one side and a one-way tooth on the other.

16. The vertical well unlimited-stage tubing fracturing string process according to claim 1, characterized in that, The infinite-level fracturing sleeve includes an infinite-level fracturing sleeve body assembly, an infinite-level fracturing sleeve accessory, and an opening tool assembly. The opening tool assembly is embedded in the side wall of the infinite-level fracturing sleeve body assembly and connected to the infinite-level fracturing sleeve accessory. The opening tool assembly controls whether the infinite-level fracturing sleeve body assembly and the infinite-level fracturing sleeve accessory are movable.

17. The vertical well unlimited-stage tubing fracturing string process according to claim 16, characterized in that, The infinite-level fracturing sleeve body assembly includes an infinite-level fracturing sleeve upper connector, an infinite-level fracturing sleeve body, an infinite-level fracturing sleeve shear pin, an infinite-level fracturing sleeve inner sleeve, an infinite-level fracturing sleeve retaining ring, and an infinite-level fracturing sleeve lower connector. The upper connector of the infinite-level fracturing sleeve has an internal ramp and is connected to the body of the infinite-level fracturing sleeve and the lower connector of the infinite-level fracturing sleeve by threads to form a whole; the inner sleeve of the infinite-level fracturing sleeve is pre-positioned on a predetermined position on the body of the infinite-level fracturing sleeve by the infinite-level fracturing sleeve shear pin; the retaining ring of the infinite-level fracturing sleeve is sleeved on the outside of the inner sleeve of the infinite-level fracturing sleeve to prevent the inner sleeve of the infinite-level fracturing sleeve from moving in the opposite direction.

18. The vertical well unlimited-stage tubing fracturing string process according to claim 17, characterized in that, The infinite-level fracturing slip ring is a C-shaped elastic open ring.

19. The vertical well unlimited-stage tubing fracturing string process according to claim 17, characterized in that, The opening tool assembly includes: an upper pumping ball, an infinite-stage fracturing sleeve sealing ring, an upper ball seat, an opening tool body, a lower pumping ball, and a lower ball seat; the upper ball seat and the lower ball seat have sealing grooves, and the infinite-stage fracturing sleeve sealing ring is installed in the sealing grooves; the upper ball seat and the lower ball seat are connected to the opening tool body; the opening tool body is a stepped sleeve, and the right end face of the step of the opening tool body matches the lower end of the groove of the inner sleeve of the infinite-stage fracturing sleeve; the upper connector of the infinite-stage fracturing sleeve has a slope inside.

20. The vertical well unlimited-stage tubing fracturing string process according to claim 19, characterized in that, The slope of the ramp inside the joint of the infinite-level fracturing sleeve is less than 25 degrees.

21. The vertical well unlimited-stage tubing fracturing string process according to claim 19, characterized in that, The upper ball seat and the lower ball seat are connected to the opening tool body by screws; the opening tool body is a stepped, hollowed-out metal flexible sleeve.

22. The vertical well unlimited-stage tubing fracturing string process according to claim 1, characterized in that, The safety release connector includes a safety release upper connector, a safety release outer cylinder, a safety release lower connector, a safety release sealing ring, and a safety release scissor pin. The safety release upper connector has an internal ramp and is integrated with the safety release outer cylinder. The safety release upper connector and the safety release lower connector are connected by the safety release scissor pin.

23. The vertical well unlimited-stage tubing fracturing string process according to claim 22, characterized in that, The safety release clip is installed in the threaded hole at the lower end of the safety release outer tube; the safety release upper connector is connected to the safety release outer tube by a threaded connection.

24. A method for implementing the vertical well unlimited-stage tubing fracturing string process according to any one of claims 1-23, characterized in that, Includes the following steps: Fracturing string insertion: After completing the wellbore preparations for washing, cleaning, and scraping, connect the vertical well unlimited tubing fracturing string, and then, based on the target formation depth, run the vertical well unlimited tubing fracturing string into the predetermined position and set up the wellhead equipment. Packer setting: A setting ball is inserted and allowed to sink freely or be pumped to the setting ball seat. At this time, a dead cavity is formed in the tubing string. The wellhead pump truck pressurizes the pressure to the preset pressure P0 to complete the setting of the packer downhole. Then the setting ball is removed to achieve communication between the tubing string and the formation. fracture: First stage of fracturing: Fracturing fluid is injected and flows out from the tail end of the tubing string into the formation, completing the first stage of fracturing. The working pressure during fracturing is set to P. During the fracturing process, the telescopic tube will reach the working pressure P1, thus entering the working state; For layer-switching fracturing, the opening tool assembly is deployed from the wellhead, and the pump is moved to the next stage. The pressure is built up to the opening pressure P2 of the infinite-stage fracturing sleeve, and the infinite-stage fracturing sleeve is opened to perform fracturing of the current stage. This process of layer-switching fracturing is repeated to achieve fracturing of all stages. Lifting the tubing string load: Drop a ball that matches the kill valve into the wellhead and let it sink naturally to the kill valve. When the pressure of the kill valve reaches P3, open the kill valve and perform circulation kill to the preset qualified standard; lift the tubing string load to the preset unsealing load F0, the downhole packer is unsealed, and the entire well tubing string is pulled out; Drop and retrieval: In case of unexpected situations such as sand burial of downhole tools or tubing jamming, the tubing load is raised to the preset drop load F1, then the safety drop connector is sheared, the upper tubing is pulled out, and then the sand flushing and retrieval are carried out in stages.

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