Open hole packer capable of preventing obstruction

Abstract

The invention relates to the technical field of oil and gas well completion tools, and discloses an anti-resistance open hole packer which comprises a central pipe and a rubber sleeve arranged outside the central pipe in a sleeving mode, and further comprises a double-piston setting mechanism arranged on the central pipe in a sleeving mode and defining a pressure-bearing cavity, one end of the double-piston setting mechanism abuts against the end of the rubber sleeve, and the other end of the double-piston setting mechanism abuts against the end of the rubber sleeve. Axial thrust is generated by receiving high-pressure liquid conducted in the center pipe, and the rubber barrel is extruded to deform in the radial direction and be attached to the open hole well wall. And the lower piston assembly is arranged in a pressure-bearing cavity between the central pipe and the double-piston setting mechanism, firstly moves in the direction far away from the rubber barrel under the action of high-pressure liquid, relieves the pre-locking state of the double-piston setting mechanism and then drives the double-piston setting mechanism to move in the direction of the rubber barrel. The open hole packer capable of preventing resistance encountering aims at solving the problems that a setting mechanism is started in advance and set accidentally due to resistance encountering in the process that an existing open hole packer goes into a well, and the existing open hole packer cannot reach a preset packing position accurately.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well completion tools, specifically to an open-hole packer designed to prevent obstruction. Background Technology

[0002] In oil and gas field development, open-hole fracturing operations require packers to effectively isolate different sections. Open-hole packers form a seal by radially expanding a rubber sleeve and adhering to the wellbore, and are fixed in position by an anchoring mechanism, thus meeting the technological requirements of segmented fracturing. Existing open-hole packers typically use a hydraulic drive for setting, where high-pressure fluid is pumped into the central tube, pushing a piston assembly to compress the rubber sleeve, causing it to expand radially and sealing the open-hole wellbore. With the deepening exploration and development of unconventional oil and gas reservoirs, higher demands are placed on the reliability and adaptability of packers, especially in complex well conditions where accurate positioning and effective setting are crucial.

[0003] However, existing open-hole packers have significant drawbacks during the wellbore running process: when the packer passes through narrow sections, dogleg sections, or encounters complex well conditions such as wellbore collapse, wellbore resistance acts on the packer's external structure, generating axial thrust. This thrust is directly transmitted to the setting mechanism, causing the piston assembly to activate prematurely and deform the rubber sleeve, resulting in the packer unexpectedly setting at an unintended position. This premature setting upon encountering resistance not only prevents the packer from reaching the designed depth, affecting the accuracy of fracturing stages, but also may cause complex downhole accidents due to premature expansion of the rubber sleeve, severely restricting the safety and reliability of open-hole completion operations. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that existing open-hole packers encounter obstacles during the well running process, causing the setting mechanism to start prematurely and unexpectedly set, thus failing to accurately reach the predetermined packing position. Therefore, this invention proposes an open-hole packer that is resistant to encountering obstacles.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: An obstruction-resistant open-eye packer includes a central tube and a rubber sleeve fitted over the central tube, and further includes: The double piston setting mechanism is sleeved on the central tube and encloses a pressure-bearing chamber. One end of the piston abuts against the end of the rubber sleeve. By receiving the high-pressure liquid transmitted in the central tube, it generates axial thrust, squeezing the rubber sleeve to deform radially and fit tightly against the open hole well wall. The lower piston assembly is located in the pressure-bearing chamber between the central tube and the double piston setting mechanism. Under the action of high-pressure liquid, it first moves away from the rubber cylinder, releasing the pre-locking state of the double piston setting mechanism, and then drives the double piston setting mechanism to move towards the rubber cylinder. The anchoring and locking mechanism is sleeved on the outside of the central tube and connected to the other end of the double piston setting mechanism. It can limit and lock the axial position of the double piston setting mechanism after displacement, so as to achieve stable maintenance of the rubber sleeve setting state.

[0006] Based on the above technical solution, the present invention can be further improved as follows.

[0007] Furthermore, the dual-piston setting mechanism includes an upper piston sleeve and a lower piston sleeve. The upper piston sleeve and the lower piston sleeve are coaxially sleeved on the outside of the central tube. The two together with the outer wall of the central tube form a pressure-bearing chamber. The high-pressure liquid in the central tube enters the pressure-bearing chamber and generates an axial thrust to drive the rubber sleeve to expand radially and fit against the open hole well wall.

[0008] Furthermore, the dual-piston setting mechanism also includes an upper piston, which is sleeved on the outside of the central tube and connects the upper piston sleeve and the lower piston sleeve. The end of the upper piston near the lower piston assembly is provided with an elastic claw structure. Under the axial pressure of the lower piston assembly, the elastic claw is tightly attached to the outer wall of the central tube, bearing the resistance load during the well running process and preventing the dual-piston setting mechanism from starting prematurely.

[0009] Furthermore, the outer wall of the central tube is fixed with two semi-rings, and a retaining ring, a hoop ring and an O-ring are symmetrically arranged between the two semi-rings in sequence. The outer circumferential surface of the O-ring slides and seals with the inner wall of the upper piston sleeve. The O-ring, the central tube and the upper piston sleeve enclose and form the first liquid inlet area. Two pressure transmission holes are opened on the wall of the central tube, one of which is connected to the first liquid inlet area to realize the directional delivery of high pressure liquid.

[0010] Furthermore, the lower piston assembly includes a lower piston and a first shear pin. The lower piston is sleeved outside the central tube and accommodated in the inner cavity of the lower piston sleeve. The end of the lower piston presses against the elastic claw of the upper piston. The first shear pin passes through and fixes the lower piston and the central tube. The upper piston, lower piston sleeve, central tube and lower piston enclose to form a second liquid inlet area. Another pressure transmission hole connects to the second liquid inlet area. When high-pressure liquid enters the second liquid inlet area, the first shear pin is sheared, driving the lower piston to move away from the rubber tube, releasing the pressure on the elastic claw, and releasing the double piston setting mechanism to start setting.

[0011] Furthermore, two C-shaped rings are embedded in the outer wall of the central tube, with the two C-shaped rings located on both sides of the lower piston's axial direction to limit the axial stroke of the lower piston.

[0012] Furthermore, the central tube is connected to an upper connector and a lower connector at its two axial ends, respectively. The upper connector abuts against the end face of the rubber tube away from the double piston setting mechanism to form an axial limiting constraint, and the lower connector is connected to the anchoring and locking mechanism.

[0013] Furthermore, the anchoring and locking mechanism includes: A shearing sleeve is fitted onto the outer wall of the central tube and is detachably connected to the lower connector via a second shearing pin. A locking ring sleeve is installed between the shear sleeve and the lower piston sleeve, connecting the shear sleeve and the double piston setting mechanism in series. The locking ring is sleeved on the outside of the central tube and housed in the annular space between the shear sleeve and the locking ring sleeve. When the double piston setting mechanism is displaced, the locking ring sleeve drives the shear sleeve to cut off the second shear pin. The shear sleeve pushes the locking ring to lock and engage with the central tube, thereby achieving self-locking retention of the setting state.

[0014] Furthermore, the outer circumferential surface of the central tube is provided with several circumferentially distributed first ratchet teeth, and the inner circumferential surface of the locking ring is provided with several second ratchet teeth that cooperate with the first ratchet teeth. The first ratchet teeth and the second ratchet teeth form a one-way meshing structure. When the locking ring is axially displaced, the ratchet teeth gradually mesh and self-lock, continuously maintaining the setting thrust and preventing the rubber sleeve from rebounding and losing its seal due to the reaction force of the formation.

[0015] Furthermore, an elastic element is provided between the locking ring and the shear sleeve. The elastic element applies a pre-tightening force to the locking ring to ensure that the locking ring quickly engages with the ratchet of the central tube and maintains contact pressure during the anchoring process.

[0016] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: During the downhole operation, when the packer passes through a narrowing section of the wellbore or encounters wellbore collapse, the axial thrust generated by the wellbore resistance acting on the outside of the packer is absorbed by the lower piston assembly and transmitted to the central tube, rather than directly acting on the dual-piston setting mechanism. At this time, the lower piston assembly maintains a pre-locked state against the dual-piston setting mechanism, effectively preventing accidental activation of the setting mechanism and ensuring that the packer can smoothly pass through complex well conditions and reach the designed depth. Once the packer reaches the predetermined position, high-pressure fluid pumped into the central tube enters the pressure chamber, first pushing the lower piston assembly to the distal end. Displacement away from the packer releases the pre-locking constraint on the dual-piston setting mechanism. Subsequently, high-pressure fluid continues to act on the dual-piston setting mechanism to generate axial thrust, squeezing the packer radially to expand and adhere tightly to the open hole wellbore wall, achieving effective setting. In addition, the anchoring and locking mechanism limits and locks the axial position of the dual-piston setting mechanism after its displacement, continuously maintaining the squeezing force on the packer and preventing it from rebounding and losing its seal due to formation reaction force. This ensures that the packer maintains a stable sealing effect throughout the entire fracturing operation, improving the reliability and safety of open hole completion operations. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the connection structure before the sealing of the present invention; Figure 2 For the present invention Figure 1 Enlarged view of point A in the middle; Figure 3 For the present invention Figure 1Enlarged view at point B in the middle; Figure 4 For the present invention Figure 1 Enlarged view at point C; Figure 5 This is a schematic diagram of the connection structure during the setting process of the present invention; Figure 6 For the present invention Figure 5 Enlarged view at point D; Figure 7 For the present invention Figure 5 Enlarged view of point E in the middle.

[0018] In the diagram: 1. Central tube; 2. Rubber sleeve; 3. Double piston setting mechanism; 31. Upper piston sleeve; 32. Lower piston sleeve; 33. Upper piston; 4. Lower piston assembly; 41. Lower piston; 42. First shear pin; 5. Anchoring and locking mechanism; 51. Shear sleeve; 52. Second shear pin; 53. Locking ring sleeve; 54. Locking ring; 6. Half ring; 7. Retaining ring; 8. Hoop ring; 9. O-ring; 10. C-ring; 11. Upper connector; 12. Lower connector; 13. Elastic element. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 and Figure 5 As shown, this invention provides an open-hole packer for preventing obstruction, comprising a central tube 1 and a rubber sleeve 2 fitted outside the central tube 1. The central tube 1 adopts an integral tube structure, with its two ends axially connected and fixed to an upper connector 11 and a lower connector 12, respectively. The outer circumference of the central tube 1 is provided with an external thread structure, and the upper connector 11 and the lower connector 12 are provided with internal thread structures. The upper connector 11 and the lower connector 12 are connected to the central tube 1 by threads. One end of the rubber sleeve 2 can be fixed to the central tube 1 by a threaded connection. The rubber sleeve 2 adopts a segmented sealing structure, including a combination of an upper outer back ring, a side rubber sleeve, a middle rubber sleeve, and a lower outer back ring. This structural design allows the rubber sleeve 2 to expand uniformly radially when subjected to axial compression, effectively conforming to the irregular morphology of the open-hole wall. It should also be noted that the structure, shape, and working principle of the rubber sleeve 2 have been disclosed in Chinese patent application number CN202511952868.6, a rubber sleeve with a large expansion rate, and will not be repeated here.

[0021] Furthermore, the present invention also includes a double-piston setting mechanism 3, such as... Figure 1 and Figure 3 As shown, the mechanism is fitted onto the central tube 1 and encloses the outer wall of the central tube 1 to form a pressure-bearing chamber. This pressure-bearing chamber serves as the pressure-bearing chamber for hydraulic transmission, receiving high-pressure liquid transmitted from inside the central tube 1. One end of the double-piston setting mechanism 3 abuts against the end of the rubber sleeve 2, generating axial thrust through the action of the high-pressure liquid in the pressure-bearing chamber, squeezing the rubber sleeve 2 into radial deformation to fit tightly against the open hole well wall.

[0022] Specifically, the dual-piston setting mechanism 3 includes an upper piston sleeve 31 and a lower piston sleeve 32. The upper piston sleeve 31 and the lower piston sleeve 32 are coaxially sleeved on the outside of the central tube 1, and together with the outer wall of the central tube 1, they enclose a pressure-bearing chamber. The high-pressure liquid inside the central tube 1 is guided to the pressure-bearing chamber, forming a hydraulic thrust in the pressure-bearing chamber, which drives the dual-piston setting mechanism 3 to axially displace towards the rubber sleeve 2, causing the rubber sleeve 2 to expand radially and fit against the open hole well wall.

[0023] To achieve tandem force transmission between two pistons, such as Figure 1 and Figure 3 As shown, the dual-piston setting mechanism 3 also includes an upper piston 33, which is sleeved on the outside of the central tube 1 and bridges the upper piston sleeve 31 and the lower piston sleeve 32. The upper piston 33 has two external threads on its outer circumference, which mesh with the internal threads of the upper piston sleeve 31 and the lower piston sleeve 32 respectively, forming a mechanical tandem structure of two-stage pistons. This two-stage piston design provides a greater setting thrust compared to a single-piston structure. Several exhaust holes are provided on the outer walls of the upper piston sleeve 31 and the lower piston sleeve 32. When the gas in the pressure chamber is compressed during the setting process, the gas is discharged outward through the exhaust holes, avoiding the air pocket effect from affecting the setting effect.

[0024] The upper piston 33 has an elastic claw structure on its end face near the lower piston assembly 4. The elastic claw has multiple claw teeth distributed circumferentially and has a certain radial elastic deformation in its free state. During the downhole operation, the elastic claw is pressed by the end face of the lower piston assembly 4, causing the elastic claw to fit tightly against the outer wall of the central tube 1. At the same time, the end of the elastic claw is also provided with a corresponding protrusion, and a recess is provided on the outer wall of the central tube 1 to match the protrusion. The protrusion fits tightly into the recess. At this time, a frictional contact relationship is formed between the elastic claw, the end of the lower piston 41, and the recess of the central tube 1. This frictional force is sufficient to withstand the obstruction load caused by wellbore reduction, dogleg section, or well wall collapse during the downhole process, effectively preventing the double piston setting mechanism 3 from starting prematurely under the action of external mechanical force. The elastic claw structure can also be an elastic leaf spring or a sloped locking structure, both of which can achieve a pre-locking function.

[0025] like Figure 1 and Figure 3As shown, the lower piston assembly 4 is located in the pressure-bearing chamber between the central tube 1 and the double-piston setting mechanism 3. This assembly plays a graded control role of "unlocking first, then driving" during the setting and starting process. Specifically, the lower piston assembly 4 includes a lower piston 41 and a first shear pin 42. The lower piston 41 is sleeved on the outside of the central tube 1 and accommodated in the inner cavity of the lower piston sleeve 32. The end face of the lower piston 41 presses against the elastic claw of the upper piston 33 to maintain a pre-locked state. The first shear pin 42 radially penetrates and fixes the lower piston 41 and the central tube 1. The shear strength of the shear pin is designed and selected according to the preset setting pressure.

[0026] Two semi-rings 6 are fixed to the outer wall of the central tube 1. Between the two semi-rings 6, a retaining ring 7, a hoop ring 8, and an O-ring 9 are symmetrically arranged in sequence. This assembly together constitutes a sealing and positioning assembly. Figure 1 and Figure 2 As shown, the outer circumferential surface of the O-ring 9 forms a sliding seal with the inner wall of the upper piston sleeve 31, allowing the upper piston sleeve 31 to move axially relative to the central tube 1 while maintaining a radial seal. The O-ring 9, the central tube 1, and the upper piston sleeve 31 together form the first liquid inlet area, which provides hydraulic power to the upper piston sleeve 31. Two pressure transmission holes are formed on the wall of the central tube 1. One pressure transmission hole is located near the end of the upper piston sleeve 31, and the other pressure transmission hole is located near the end of the lower piston sleeve 32. The pressure transmission hole near the end of the upper piston sleeve 31 connects to the first liquid inlet area, realizing the directional delivery and pressure distribution of high-pressure liquid.

[0027] like Figure 1 and Figure 3 As shown, the upper piston 33, lower piston sleeve 32, central tube 1, and lower piston 41 together form the second liquid inlet area. A pressure transmission hole near the end of the lower piston sleeve 32 connects to this second liquid inlet area. When the high-pressure liquid pumped into the central tube 1 reaches the preset setting pressure, the liquid simultaneously enters the first and second liquid inlet areas. The hydraulic pressure in the second liquid inlet area first acts on the lower piston 41, generating an axial force sufficient to shear the first shear pin 42, driving the lower piston 41 to move away from the rubber sleeve 2. This releases the clamping constraint on the elastic claw of the upper piston 33. At this time, the elastic claw, under its own elastic restoring force, disengages from the outer wall of the central tube 1, releasing the pre-locked state of the double-piston setting mechanism 3, allowing it to start setting under hydraulic pressure, and subsequently driving the double-piston setting mechanism 3 to move towards the rubber sleeve 2. This "hydraulic unlocking" mechanism ensures that only hydraulic signals from inside the central tube 1 can initiate setting, while external mechanical loads cannot trigger the process.

[0028] To ensure a good seal, inner and outer sealing rings are respectively embedded on the inner and outer sides of the lower piston 41 and the upper piston 33. The inner sealing ring is in sealing contact with the outer wall of the central tube 1, and the outer sealing ring is in sealing contact with the inner wall of the lower piston sleeve 32, forming a double sealing structure to ensure the liquid tightness of the second liquid inlet area.

[0029] To prevent excessive displacement, two C-shaped rings 10 are also embedded in the outer wall of the central tube 1, such as Figure 3 and Figure 7 As shown, the two C-rings 10 are located at the two ends of the axial displacement stroke of the lower piston 41, respectively, to limit the axial displacement distance of the lower piston 41 and prevent the lower piston 41 from over-displacement due to excessive hydraulic pressure, which could damage the sealing structure. The C-rings 10 can also be replaced by axial limiting elements such as snap rings or retaining rings.

[0030] The upper connector 11 abuts against the end face of the rubber sleeve 2 away from the double piston setting mechanism 3. This abutment surface forms an axial limiting constraint, ensuring that the rubber sleeve 2 can only expand radially without axial movement when subjected to compression. The lower connector 12 is connected to the subsequent anchoring and locking mechanism 5, serving as the terminal support for force transmission.

[0031] Anchoring and locking mechanism 5 is sleeved on the outside of central tube 1 and connected to the other end of double piston setting mechanism 3. This mechanism can limit and lock the axial position of double piston setting mechanism 3 after displacement, so as to stabilize the setting state of rubber tube 2 and prevent rubber tube 2 from rebounding and losing its seal due to the reaction force of the stratum.

[0032] Specifically, the anchoring and locking mechanism 5 includes a shear sleeve 51, a second shear pin 52, a locking ring sleeve 53, and a locking ring 54, as follows: Figure 4 and Figure 7 As shown.

[0033] The shear sleeve 51 is fitted onto the outer wall of the central tube 1 and is detachably connected to the lower connector 12 via the second shear pin 52. This detachable connection provides axial constraint before setting, preventing the mechanism from loosening. The locking ring sleeve 53 has external threads at both ends. One end engages with the internal thread of the lower piston sleeve 32, and the other end engages with the internal thread of the shear sleeve 51. The locking ring sleeve 53 connects the shear sleeve 51 and the double piston setting mechanism 3 in series, forming a complete transmission chain. The locking ring 54 is fitted onto the outside of the central tube 1 and accommodated in the annular space between the shear sleeve 51 and the locking ring sleeve 53. This annular space provides the locking ring 54 with room for radial contraction and axial displacement.

[0034] When the dual-piston setting mechanism 3 is hydraulically driven to move towards the rubber sleeve 2, the locking ring sleeve 53 drives the shearing sleeve 51 to move synchronously. The shearing sleeve 51 applies a shear load to the second shearing pin 52. When the load reaches the shear strength limit of the pin, the second shearing pin 52 is sheared, and the shearing sleeve 51 gains free displacement capability, pushing the locking ring 54 forward under axial thrust. The outer circumferential surface of the central tube 1 is pre-machined with several circumferentially distributed first ratchet teeth, and the inner circumferential surface of the locking ring 54 is provided with several second ratchet teeth that match the tooth shape of the first ratchet teeth. The two sets of ratchet teeth adopt a unidirectional meshing design, that is, when the locking ring 54 moves axially in the setting direction, the ratchet teeth gradually mesh, but when it moves in the opposite direction, the ratchet teeth immediately lock to form a self-locking mechanism. Figure 7 As shown, this ratchet self-locking structure ensures that the anchoring and locking mechanism 5 maintains the setting thrust after setting. Even if the hydraulic pressure inside the central tube 1 is released, the compressive force on the rubber sleeve 2 is still borne by the ratchet meshing surface, effectively preventing the rubber sleeve 2 from rebounding and losing its seal due to the elastic recovery of the formation. The first and second ratchet teeth can also be designed as sawtooth or wedge-shaped tooth structures, and the number of teeth and tooth profile parameters can be adjusted according to the locking force requirements.

[0035] An elastic element 13 is provided between the locking ring 54 and the shear sleeve 51. This elastic element can be a wave spring, a disc spring, or a cylindrical helical spring. Figure 4 As shown, the elastic element 13 applies a continuous preload to the locking ring 54. This preload ensures that the locking ring 54 quickly engages with the first ratchet of the central tube 1 during anchoring and maintains contact pressure, eliminating engagement gaps and improving locking reliability. The preload of the elastic element 13 can also compensate for the thermal expansion and contraction effect caused by temperature changes, maintaining the stability of the ratchet engagement state.

[0036] The working principle of the obstruction-resistant naked-eye packer of this invention is as follows: During the process of lowering the packer into the well along with the tubing, the end of the lower piston 41 continuously presses against the elastic claw structure of the upper piston 33, causing the elastic claw to form frictional contact with the outer wall of the central tube 1. Simultaneously, the first shear pin 42 penetrates and fixes the lower piston 41 to the central tube 1, and the second shear pin 52 locks the shear sleeve 51 to the lower connector 12. The double-piston setting mechanism 3 is in a pre-locked state. Figure 1 As shown; When the packer passes through the wellbore narrowing section, dogleg section or encounters the axial resistance generated by wellbore collapse during the well running process, the axial thrust is effectively prevented from starting the double piston setting mechanism 3 in advance by the friction between the elastic claw and the outer wall of the central tube 1 and the fixing action of the first shear pin 42, thus ensuring that the packer is smoothly lowered to the predetermined depth. When the packer reaches the predetermined packing position, high-pressure liquid is pumped from the oil pipe into the central pipe 1. This high-pressure liquid enters the first and second inlet regions respectively through two pressure-transmitting holes in the wall of the central pipe 1. As the hydraulic pressure continues to rise, the high-pressure liquid in the second inlet region first generates sufficient axial thrust on the lower piston 41. When this thrust reaches the shear strength threshold of the first shear pin 42, the first shear pin 42 is sheared off. Figure 7 As shown; Driven by high-pressure liquid, the lower piston 41 moves axially away from the rubber sleeve 2. Two C-rings 10 limit the displacement stroke of the lower piston 41. After displacement, the lower piston 41 releases the axial pressure on the elastic claw of the upper piston 33. Under its own elastic restoring force, the elastic claw disengages from the outer wall of the central tube 1, releasing the pre-locked state of the double-piston setting mechanism 3. Figure 7 As shown; Subsequently, the high-pressure liquid in the first inlet area continuously generates axial thrust on the upper piston sleeve 31 and the lower piston sleeve 32, driving the double piston setting mechanism 3 to move as a whole towards the rubber sleeve 2. The upper piston sleeve 31 forms a two-stage thrust series transmission through the threaded connection between the upper piston 33 and the lower piston sleeve 32, squeezing the rubber sleeve 2 to expand radially until it is tightly attached to the open hole well wall to achieve a seal. The exhaust holes opened on the outer walls of the upper piston sleeve 31 and the lower piston sleeve 32 allow the gas in the pressure chamber to be discharged during the compression process. While the dual-piston setting mechanism 3 moves towards the rubber sleeve 2, the locking ring sleeve 53 drives the shear sleeve 51 to move synchronously. When the shear load applied by the shear sleeve 51 to the second shear pin 52 reaches its shear strength, the second shear pin 52 is sheared off. Under the action of axial thrust, the shear sleeve 51 pushes the locking ring 54 forward. The second ratchet on the inner circumferential surface of the locking ring 54 and the first ratchet pre-machined on the outer circumferential surface of the central tube 1 form a progressive engagement. Since the ratchet adopts a unidirectional engagement design, the locking ring 54 can move along the setting direction, but it immediately locks itself when moving in the opposite direction, forming a self-locking mechanism. The elastic element 13 between the locking ring 54 and the shear sleeve 51 applies a pre-tightening force to the locking ring 54 to ensure that the ratchet engages quickly and maintains contact pressure. The anchoring and locking mechanism 5 continuously maintains the setting thrust through the ratchet self-locking structure. Figure 7 As shown; Even after the hydraulic pressure inside the central tube 1 is released, the compressive force borne by the rubber sleeve 2 is still borne by the meshing surface of the first and second ratchet teeth, effectively preventing the rubber sleeve 2 from rebounding and losing its seal due to the elastic reaction force of the formation. This ensures that the packer maintains a stable sealing effect throughout the entire fracturing operation. The upper connector 11 abuts against the end face of the rubber sleeve 2 away from the double piston setting mechanism 3 to form an axial limiting constraint, so that the rubber sleeve 2 can only expand radially without axial movement, thereby completing the entire process of anti-obstruction downhole, hydraulic start-up setting, and ratchet locking and retention.

[0037] This invention effectively solves the technical problem of early setting of open-hole packers when encountering obstruction through a graded control mechanism of pre-locking and hydraulic unlocking, improving the success rate of running-in and the reliability of setting in complex well conditions, and has good application and promotion value.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A drag-free open hole packer comprising a central pipe (1) and a rubber sleeve (2) fitted outside the central pipe (1), characterized in that, Also include: Double piston setting mechanism (3), set on the central tube (1) and enclosed to form a pressure chamber, one end of which is in contact with the rubber cylinder (2), generates axial thrust by receiving high pressure liquid conducted in the central tube (1), extrudes the rubber cylinder (2) to deform radially and adhere to the well wall; Lower piston assembly (4), arranged in the pressure chamber between the central tube (1) and the double piston setting mechanism (3), first moves away from the rubber cylinder (2) under the action of high pressure liquid, releases the pre-locking state of the double piston setting mechanism (3), and then drives the double piston setting mechanism (3) to move towards the rubber cylinder (2); Anchor locking mechanism (5), set on the outside of the central tube (1) and in transmission connection with the other end of the double piston setting mechanism (3), can limit the axial position of the double piston setting mechanism (3) after displacement, realize the stable maintenance of the rubber cylinder (2) setting state.

2. The drift avoidance open hole packer of claim 1, wherein, The double piston setting mechanism (3) includes an upper piston sleeve (31) and a lower piston sleeve (32), which are coaxially set on the outside of the central tube (1), and the two form a pressure chamber with the outer wall of the central tube (1). The high pressure liquid in the central tube (1) enters the pressure chamber to generate axial thrust to drive the rubber cylinder (2) to expand radially and adhere to the well wall.

3. A drift avoidance open hole packer according to claim 2, wherein, The double piston setting mechanism (3) further includes an upper piston (33) which is set on the outside of the central tube (1) and connects the upper piston sleeve (31) and the lower piston sleeve (32). The end of the upper piston (33) close to the lower piston assembly (4) is provided with a resilient claw structure. The resilient claw is in close contact with the outer wall of the central tube (1) under the axial compression of the lower piston assembly (4), bears the resistance load during the lowering process, and prevents the double piston setting mechanism (3) from starting too early.

4. The untripped open hole packer of claim 3, wherein, The outer wall of the central tube (1) is fixed with two half rings (6), and a blocking ring (7), a hoop ring (8) and an O-ring (9) are symmetrically arranged between the two half rings (6). The outer circumferential surface of the O-ring (9) is in sliding sealing cooperation with the inner wall of the upper piston sleeve (31), and the O-ring (9), the central tube (1) and the upper piston sleeve (31) form a first liquid inlet area. Two pressure transmission holes are provided in the wall of the central tube (1), one of which communicates with the first liquid inlet area to realize the directional delivery of high pressure liquid.

5. A drift avoidance open hole packer according to claim 4, wherein, The lower piston assembly (4) includes a lower piston (41) and a first shear pin (42). The lower piston (41) is set on the outside of the central tube (1) and accommodated in the inner cavity of the lower piston sleeve (32). The end of the lower piston (41) presses the resilient claw of the upper piston (33). The first shear pin (42) penetrates and fixes the lower piston (41) and the central tube (1). The upper piston (33), the lower piston sleeve (32), the central tube (1) and the lower piston (41) form a second liquid inlet area, and the other pressure transmission hole communicates with the second liquid inlet area.

6. A drift avoidance open hole packer according to claim 5, wherein, The outer wall of the central tube (1) is embedded with two C-shaped rings (10), which are respectively located on the two sides of the axial direction of the lower piston (41) to limit the axial stroke of the lower piston (41).

7. The untripped open hole packer of claim 2, wherein, The axial both ends of the central pipe (1) are connected with an upper joint (11) and a lower joint (12) respectively, the upper joint (11) abuts against the end face of the rubber sleeve (2) away from the double-piston setting mechanism (3), forming axial limiting constraint, and the lower joint (12) is connected with the anchoring and locking mechanism (5).

8. The drift avoidance open hole packer of claim 7, wherein, The anchoring and locking mechanism (5) comprises: A shearing sleeve (51) is sleeved on the outer wall of the central pipe (1) and is detachably connected with the lower joint (12) through a second shearing pin (52); A lock ring sleeve (53) is arranged between the shearing sleeve (51) and the lower piston sleeve (32), connecting the shearing sleeve (51) and the double-piston setting mechanism (3) in series; A lock ring (54) is sleeved on the outer side of the central pipe (1) and accommodated in the annular space between the shearing sleeve (51) and the lock ring sleeve (53), when the double-piston setting mechanism (3) is displaced, the lock ring sleeve (53) drives the shearing sleeve (51) to shear the second shearing pin (52), the shearing sleeve (51) pushes the lock ring (54) to lock and engage with the central pipe (1), realizing self-locking retention in the setting state.

9. A drift avoidance open hole packer according to claim 8, wherein, The outer peripheral surface of the central pipe (1) is provided with a plurality of first ratchets distributed in the ring direction, the inner peripheral surface of the lock ring (54) is provided with a plurality of second ratchets matched with the first ratchets, the first ratchets and the second ratchets form a one-way meshing structure, the ratchets gradually mesh and self-lock when the lock ring (54) is axially displaced, continuously maintaining the setting thrust, preventing the rubber sleeve (2) from rebounding and losing sealing due to the ground reaction force.

10. The drift avoidance open hole packer of claim 9, wherein, An elastic member (13) is arranged between the lock ring (54) and the shearing sleeve (51), the elastic member (13) applies a pre-tightening force to the lock ring (54), ensuring that the lock ring (54) is quickly meshed with the ratchets of the central pipe (1) and maintains contact pressure during anchoring.

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