Limit stress releaser for oil and gas well casing

Abstract

The invention relates to the technical field of oil and gas well casing protection, in particular to an oil and gas well casing limit stress releaser which comprises an inner pipe and an outer sleeve, the outer sleeve and the inner pipe are coaxially arranged in the vertical direction and connected in a sleeved mode, an upper buffering cavity and a lower buffering cavity are defined between the outer sleeve and the inner pipe, and the upper buffering cavity and the lower buffering cavity are filled with sealing filler. A tensile stress releasing part is arranged at the upper buffering cavity, a pressure stress releasing part is arranged at the lower buffering cavity, and a torsional stress releasing part is further arranged between the outer sleeve and the inner pipe. According to the limit stress releaser for the oil and gas well casing pipe, the tensile stress releasing piece, the pressure stress releasing piece and the torsion stress releasing piece are started when the tensile stress releasing piece, the pressure stress releasing piece and the torsion stress releasing piece exceed corresponding threshold values, and therefore the tensile stress, the pressure stress and the torsion stress are actively released in a targeted mode. And a comprehensive release mechanism for various stresses is achieved, the comprehensive protection effect on the casing pipe is remarkably improved, and the service life of an oil and gas well is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well casing protection, and in particular to an oil and gas well casing limit stress releaser. Background Art

[0002] During oil and gas well production, casing strings serve as key components for ensuring wellbore stability, separating fluids from different formations, and supporting downhole equipment. Their performance and safety are crucial to oil and gas production operations. However, in actual production, casing strings are exposed to complex and changing downhole environments for extended periods of time, often affected by factors such as formation movement, temperature changes, and fluid pressure fluctuations. Consequently, they are subjected to various loads, including tensile, compressive, and torsional stresses.

[0003] For example, when tectonic movement occurs in the stratum, the casing will be squeezed or stretched, generating compressive stress or tensile stress. The frequent fluctuations in fluid pressure, especially when different operating links such as drilling, oil production and gas injection are alternating, will cause the casing to undergo periodic stress changes. At the same time, torsional stress will be generated during the casing rotation operation or the torque transmission of the downhole tool. Once these stresses exceed or approach the limit bearing value of the casing, it is very easy to cause serious problems such as deformation and fracture of the casing. Not only will it cause the oil and gas well to reduce or even stop production, increase mining costs, but it may also cause major safety accidents such as blowouts and oil and gas leaks, posing a huge threat to personnel safety and the ecological environment. At present, most stress release devices in the existing technology only provide protection for a single stress type. When faced with complex combinations of working conditions, the protection effect is greatly reduced and cannot meet the needs of the actual complex stress environment in the well. Summary of the Invention

[0004] The present invention provides an extreme stress releaser for oil and gas well casing, which monitors and actively releases tensile stress, compressive stress and torsional stress in real time to solve the problem that most existing stress release devices only protect against a single stress type and lack a comprehensive release mechanism for multiple stresses. When faced with complex working conditions, they cannot meet the needs of the actual complex stress environment underground.

[0005] The invention provides an oil and gas well casing limit stress releaser adopts the following technical scheme: an oil and gas well casing limit stress releaser, which is installed between two adjacent casings in a casing string, and comprises an inner tube and an outer tube, the outer tube and the inner tube are coaxially arranged in a vertical direction and are sleeved with each other, the upper end of the inner tube is connected to the casing above it, and the lower end of the outer tube is connected to the casing below it; an upper buffer cavity and a lower buffer cavity are defined between the outer tube and the inner tube, the upper buffer cavity is located above the lower buffer cavity, and both the upper buffer cavity and the lower buffer cavity are filled with sealing fillers; a tensile stress release part is provided at the upper buffer cavity, a compressive stress release part is provided at the lower buffer cavity, and a torsional stress release part is further provided between the outer tube and the inner tube; in the initial state, the tensile stress release part limits The outer tube and the inner tube are moved away from each other in the vertical direction, the compressive stress release member limits the outer tube and the inner tube from approaching each other in the vertical direction, and the torsional stress release member limits the outer tube and the inner tube from rotating relative to each other in the vertical direction; and when the tensile stress on the casing string is greater than the set threshold of the tensile stress release member, the tensile stress release member allows the outer tube and the inner tube to move away from each other in the vertical direction, and the upper buffer cavity is compressed at this time; when the compressive stress on the casing string is greater than the set threshold of the compressive stress release member, the compressive stress release member allows the outer tube and the inner tube to approach each other in the vertical direction, and the lower buffer cavity is compressed at this time; when the torsional stress on the casing string is greater than the set threshold of the torsional stress release member, the torsional stress release member allows the outer tube and the inner tube to rotate relative to each other in the vertical direction.

[0006] Furthermore, the set threshold value of the tensile stress release member is 70% of the ultimate tensile stress of the casing, the set threshold value of the compressive stress release member is 70% of the ultimate compressive stress of the casing, and the set threshold value of the torsional stress release member is 70% of the ultimate torsional stress of the casing.

[0007] Furthermore, the outer sleeve includes a first outer tube and a second outer tube, which are both arranged in the vertical direction and are coaxial, and the first outer tube is located above the second outer tube and is screwed to the second outer tube; the lower end of the second outer tube is connected to the sleeve below it; the inner tube includes a first pipe section and a second pipe section, which are both coaxially arranged in the vertical direction, and the first pipe section is located above the second pipe section and is screwed to the second pipe section; the upper end of the first pipe section is connected to the sleeve above it; the second pipe section is provided with a first boss and a second boss arranged in the vertical direction, the first boss is located above the second boss, and the first boss and the second boss are both slidingly sealed with the inner wall of the first outer tube; the upper buffer chamber is defined by the first outer tube, the first pipe section and the first boss; the lower buffer chamber is defined by the first outer tube, the second pipe section and the second boss.

[0008] Furthermore, a plurality of first bolts are provided at the threaded connection between the first outer tube and the second outer tube, and the plurality of first bolts are evenly distributed around the vertical direction at the threaded connection between the first outer tube and the second outer tube.

[0009] Furthermore, the tensile stress release component includes a first tensile stress release valve sleeve, a first collapse point is provided on the first tensile stress release valve sleeve, a first edge is provided at the upper end of the first outer tube, the first edge is located on the inner circumferential wall surface of the first outer tube, and a second edge is provided on the outer circumferential wall surface of the first pipe section. The first edge and the second edge are both located in the upper buffer cavity and respectively abut against the upper and lower end surfaces of the first tensile stress release valve sleeve.

[0010] Furthermore, the pressure stress release component includes a pressure stress release valve sleeve, which is installed at the lower end of the second pipe section. A second collapse point is provided on the pressure stress release valve sleeve. The lower end surface of the second pipe section abuts against the upper end surface of the pressure stress release valve sleeve, and the upper end surface of the second outer tube abuts against the lower end surface of the pressure stress release valve sleeve.

[0011] Furthermore, a torsion cavity is defined between the first outer tube, the second tube section, the first boss and the second boss, and in the vertical direction, the torsion cavity is located between the upper buffer cavity and the lower buffer cavity, and the torsion stress release member is installed in the torsion cavity.

[0012] Furthermore, the torsional stress release part includes a torsional stress release pin, which is arranged along the radial direction of the first outer tube and inserted into the torsional cavity along the radial direction of the first outer tube. A sliding groove for slidingly cooperating with the torsional stress release pin is provided on the second tube section, and the sliding groove is arranged along the vertical direction; a third collapse point is provided on the torsional stress release pin.

[0013] Furthermore, a third outer tube is screwed to the upper end of the first outer tube, and the third outer tube is coaxial with the first outer tube. A second tensile stress release valve sleeve and a connecting pipe are provided between the third outer tube and the first pipe section. In the vertical direction, the connecting pipe is located between the first tensile stress release valve sleeve and the second tensile stress release valve sleeve, and abuts against the first tensile stress release valve sleeve and the second tensile stress release valve sleeve; a set threshold value of the second tensile stress release valve sleeve is greater than a set threshold value of the first tensile stress release valve sleeve and is less than 85% of the ultimate tensile stress of the sleeve. In the initial state, a distance is left between the third outer tube and the upper end surface of the second tensile stress release valve sleeve in the vertical direction, and the third outer tube can abut against the upper end surface of the second tensile stress release valve sleeve when it moves downward.

[0014] Furthermore, a first elastic member is provided between the first outer tube and the first tensile stress release valve sleeve, and the first elastic member is provided in the vertical direction; an adjusting ring is provided between the first outer tube and the third outer tube, the adjusting ring is elastic, and the adjusting ring is provided in the vertical direction and can be stretched and retracted in the vertical direction. In the initial state, there is a distance between the adjusting ring and the third outer tube, and in the radial direction of the third outer tube, the adjusting ring is located between the third outer tube and the connecting tube. Double-sided ratchets are provided on the adjusting ring, and the double-sided ratchets are respectively engaged with the connecting tube and the third outer tube. The double-sided ratchets enable the connecting tube and the third outer tube to move up relative to the adjusting ring and move down synchronously with the adjusting ring.

[0015] The beneficial effects of the present invention are as follows: an oil and gas well casing extreme stress releaser of the present invention is provided with an outer sleeve and an inner sleeve, and by real-time monitoring of the stress conditions of the casing string, the tensile stress release member, the compressive stress release member, and the torsional stress release member are respectively activated when their corresponding thresholds are exceeded, allowing relative movement between the outer sleeve and the inner sleeve, thereby actively releasing tensile stress, compressive stress, and torsional stress in a targeted manner. Compared with a single stress protection device, it has a comprehensive release mechanism for multiple stresses and can handle multiple stresses at the same time. When faced with complex working conditions, it can still meet the needs of the actual complex stress environment downhole, significantly improving the comprehensive protection effect of the casing and extending the service life of the oil and gas well. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a schematic diagram of the overall structure of a first embodiment of an oil and gas well casing limit stress releaser according to the present invention; Figure 2 This is a front view of the overall structure of a first embodiment of an oil and gas well casing limit stress releaser of the present invention; Figure 3 for Figure 2 Cross-sectional view along the middle line AA; Figure 4 for Figure 3 Enlarged view of point B in the middle; Figure 5 for Figure 3 Enlarged view of point C in the middle; Figure 6 for Figure 3 Enlarged view of point D in the middle; Figure 7 This is a schematic diagram of the overall structure of a second embodiment of an oil and gas well casing limit stress releaser according to the present invention; Figure 8 This is a front view of the overall structure of a second embodiment of an oil and gas well casing limit stress releaser of the present invention; Figure 9 for Figure 8 Cross-sectional view along the middle edge EE; Figure 10 for Figure 9 Enlarged view of point F in the middle; Figure 11 for Figure 10Enlarged view of point G in the middle; Figure 12 This is a diagram showing the state of the adjustment ring after compression of the second embodiment of the oil and gas well casing limit stress releaser of the present invention; Figure 13 This is a disassembled view of the overall structure of Example 2 of an oil and gas well casing limit stress releaser of the present invention.

[0018] In the figure: 100, inner tube; 110, first tube section; 111, second edge; 120, second tube section; 121, first boss; 122, second boss; 200, outer sleeve; 210, first outer tube; 211, first bolt; 212, first edge; 220, second outer tube; 300, upper buffer chamber; 310, first tensile stress relief valve sleeve; 311, first collapse point; 400, lower buffer chamber; 410, pressure relief valve sleeve Stress release valve sleeve; 411, second collapse point; 500, torsional stress release pin; 501, third collapse point; 510, torsional chamber; 600, third outer tube; 601, main tube; 602, installation tube section; 603, meshing section; 604, second bolt; 610, second tensile stress release valve sleeve; 611, fourth collapse point; 620, connecting tube; 630, first elastic member; 640, adjustment ring; 641, double-sided ratchet. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] An embodiment of an oil and gas well casing limit stress releaser of the present invention is as follows Figures 1 to 13 shown.

[0021] Example 1:

[0022] See also Figures 1 to 6As shown, an oil and gas well casing extreme stress reliever is installed between two adjacent casings in a casing string (not shown in the drawings of the casing string specification; the casing string consists of multiple casings arranged in sequence along a vertical direction). It includes an inner tube 100 and an outer tube 200. The outer tube 200 and the inner tube 100 are both arranged vertically coaxially and slotted onto the inner tube 100. The upper end of the inner tube 100 is connected to the casing above it, and the lower end of the outer tube 200 is connected to the casing below it. An upper buffer chamber 300 and a lower buffer chamber 400, arranged vertically in sequence, are defined between the outer tube 200 and the inner tube 100. The upper buffer chamber 300 is located above the lower buffer chamber 400 and both are filled with sealing filler. A tensile stress reliever is provided in the upper buffer chamber 300, a compressive stress reliever is provided in the lower buffer chamber 400, and a torsional stress reliever is also provided between the outer tube 200 and the inner tube 100.

[0023] In the initial state, the tensile stress release member limits the outer sleeve 200 and the inner tube 100 from moving away from each other in the vertical direction, the compressive stress release member limits the outer sleeve 200 and the inner tube 100 from moving towards each other in the vertical direction, and the torsional stress release member limits the outer sleeve 200 and the inner tube 100 from rotating relative to each other in the vertical direction; and when the tensile stress applied to the casing string is greater than the set threshold of the tensile stress release member, the tensile stress release member allows the outer sleeve 200 and the inner tube 100 to move away from each other in the vertical direction, and at this time the upper buffer cavity 300 is compressed; when the compressive stress applied to the casing string is greater than the set threshold of the compressive stress release member, the compressive stress release member allows the outer sleeve 200 and the inner tube 100 to move towards each other in the vertical direction, and at this time the lower buffer cavity 400 is compressed; when the torsional stress applied to the casing string is greater than the set threshold of the torsional stress release member, the torsional stress release member allows the outer sleeve 200 and the inner tube 100 to rotate relative to each other in the vertical direction.

[0024] Specifically, the upper end of the inner tube 100 is connected to the casing located above it, and the lower end of the outer tube 200 is connected to the casing located below it. Therefore, when the casing string is subjected to tensile stress, the inner tube 100 and the outer tube 200 tend to move away from each other in the vertical direction; when the casing string is subjected to compressive stress, the inner tube 100 and the outer tube 200 tend to move toward each other in the vertical direction.

[0025] In this embodiment, the outer sleeve 200 is arranged to cooperate with the inner tube 100. By real-time monitoring of the stress conditions of the casing string, the tensile stress release member, the compressive stress release member and the torsional stress release member are respectively activated when their corresponding thresholds are exceeded, allowing relative movement between the outer sleeve 200 and the inner tube 100, thereby actively releasing the tensile stress, compressive stress and torsional stress in a targeted manner.

[0026] Specifically, when the tensile stress on the casing string exceeds a threshold, the tensile stress release member of the upper buffer chamber 300 allows the outer sleeve 200 and the inner tube 100 to move relatively apart and compress the upper buffer chamber 300, thereby releasing the tensile stress; when the compressive stress on the casing string exceeds a threshold, the compressive stress release member of the lower buffer chamber 400 allows the outer sleeve 200 and the inner tube 100 to move relatively close and compress the lower buffer chamber 400, thereby releasing the compressive stress; when the torsional stress on the casing string exceeds a threshold, the torsional stress release member allows the outer sleeve 200 and the inner tube 100 to rotate relative to each other, thereby releasing the torsional stress. Compared with a single stress protection device, this device has a comprehensive release mechanism for multiple stresses and can handle multiple stresses at the same time. When faced with complex working conditions, it can still meet the needs of the actual complex stress environment downhole, significantly improving the comprehensive protection effect of the casing, ensuring the long-term safe operation of oil and gas wells, reducing maintenance costs, and extending the service life of oil and gas wells.

[0027] In this embodiment, the set threshold value of the tensile stress release member is 70% of the ultimate tensile stress of the casing, the set threshold value of the compressive stress release member is 70% of the ultimate compressive stress of the casing, and the set threshold value of the torsional stress release member is 70% of the ultimate torsional stress of the casing.

[0028] Tensile, compressive, and torsional stress relievers each provide targeted stress relief only when stress reaches a set threshold. This reduces the risk of stress overload by enabling early intervention and relieving tensile, compressive, and torsional stresses that exceed their limits. This reduces the probability of casing damage, such as deformation and fracture, and reduces well maintenance costs.

[0029] In this embodiment, the outer sleeve 200 includes a first outer tube 210 and a second outer tube 220. The first outer tube 210 and the second outer tube 220 are both arranged vertically and coaxially. The first outer tube 210 is positioned above the second outer tube 220 and is threadedly connected to the second outer tube 220. The lower end of the second outer tube 220 is connected to the sleeve below it. A plurality of first bolts 211 are provided at the threaded connection between the first and second outer tubes 210, 220. The plurality of first bolts 211 are evenly distributed vertically around the threaded connection between the first and second outer tubes 210, 220.

[0030] The inner tube 100 includes a first tube section 110 and a second tube section 120. The first tube section 110 and the second tube section 120 are coaxially arranged in a vertical direction. The first tube section 110 is located above the second tube section 120 and is threadedly connected to the second tube section 120. The upper end of the first tube section 110 is connected to the sleeve above it. The second tube section 120 is provided with a first boss 121 and a second boss 122 arranged in a vertical direction. The first boss 121 is located above the second boss 122. The first boss 121 and the second boss 122 are both slidingly sealed with the inner wall of the first outer tube 210. The upper buffer chamber 300 is defined by the first outer tube 210, the first tube section 110, and the first boss 121. The lower buffer chamber 400 is defined by the first outer tube 210, the second tube section 120, and the second boss 122.

[0031] A torsional cavity 510 is defined between the first outer tube 210 , the second tube section 120 , the first boss 121 and the second boss 122 , and in the vertical direction, the torsional cavity 510 is located between the upper buffer cavity 300 and the lower buffer cavity 400 , and the torsional stress release member is installed in the torsional cavity 510 .

[0032] In this embodiment, the tensile stress relief member includes a first tensile stress relief valve sleeve 310, which is provided with a first collapse point 311. A first edge 212 is provided at the upper end of the first outer tube 210, and the first edge 212 is located on the inner circumferential wall surface of the first outer tube 210. A second edge 111 is provided on the outer circumferential wall surface of the first tube section 110. The first edge 212 and the second edge 111 are both located within the upper buffer cavity 300 and abut the upper and lower end surfaces of the first tensile stress relief valve sleeve 310, respectively.

[0033] When the casing string is subjected to tensile stress, the first pipe section 110 is subjected to an upward force, which tends to drive the second pipe section 120 upward. At this time, the second edge 111 of the first pipe section 110 tends to move the first tensile stress relief valve sleeve 310 upward. Meanwhile, the second outer tube 220 is subjected to a downward force, which tends to drive the first outer tube 210 downward. At this time, the first edge 212 of the first outer tube 210 tends to move the first tensile stress relief valve sleeve 310 downward. When the tensile stress on the casing string exceeds the set threshold of the first tensile stress relief valve sleeve 310, the first tensile stress relief valve sleeve 310 will break at the first collapse point 311.

[0034] The pressure relief member includes a pressure relief valve sleeve 410, which is located at the lower end of the second pipe section 120 and threadedly connected to the second pipe section 120. The pressure relief valve sleeve 410 is provided with a second collapse point 411. The lower end surface of the second pipe section 120 abuts the upper end surface of the pressure relief valve sleeve 410, and the upper end surface of the second outer tube 220 abuts the lower end surface of the pressure relief valve sleeve 410.

[0035] When the casing string is subjected to compressive stress, the first pipe section 110 is subjected to a downward force, which tends to drive the second pipe section 120 downward. At this point, the lower end surface of the second pipe section 120 tends to push the compressive stress relief valve sleeve 410 downward. Meanwhile, the second outer tube 220 tends to drive the first outer tube 210 upward. At this point, the second outer tube 220 is subjected to an upward force, which tends to drive the upper end surface of the second outer tube 220 upward. When the compressive stress on the casing string exceeds the set threshold of the compressive stress relief valve sleeve 410, the compressive stress relief valve sleeve 410 will break at the second collapse point 411.

[0036] The torsional stress relief member includes a torsional stress relief pin 500, which is radially disposed along the first outer tube 210 and inserted into the torsional cavity 510. A vertically extending slot is defined in the second tube section 120 for sliding engagement with the torsional stress relief pin 500. The torsional stress relief pin 500 is provided with a third collapse point 501.

[0037] When the casing string is subjected to torsional stress, the first tube section 110 tends to drive the second tube section 120 to rotate vertically, and the second outer tube 220 tends to drive the first outer tube 210 to rotate vertically, with the two rotating in opposite directions. However, due to the keyway fit between the torsional stress relief pin 500 and the second tube section 120, their relative rotation is restricted. When the torsional stress on the casing string exceeds the set threshold of the torsional stress relief pin 500, the torsional stress relief pin 500 will break at the third collapse point 501, shearing the torsional stress relief pin 500. Furthermore, when the casing string is subjected to tensile or compressive stress, the torsional stress relief pin 500 can slide within the slide groove, without affecting the release of tensile or compressive stress.

[0038] Example 2:

[0039] See also Figures 7 to 13 As shown, the difference from Example 1 is that a third outer tube 600 is screwed to the upper end of the first outer tube 210, the third outer tube 600 is coaxial with the first outer tube 210, and a plurality of second bolts 604 are provided at the screw connection between the third outer tube 600 and the first outer tube 210. The plurality of second bolts 604 are evenly distributed around the vertical direction at the screw connection between the third outer tube 600 and the first outer tube 210.

[0040] A second tensile stress relief valve sleeve 610 and a connecting pipe 620 are disposed between the third outer tube 600 and the first tube section 110. Vertically, the connecting pipe 620 is located between the first and second tensile stress relief valve sleeves 310 and 610, abutting against the first and second tensile stress relief valve sleeves 310 and 610. The set threshold of the second tensile stress relief valve sleeve 610 is greater than the set threshold of the first tensile stress relief valve sleeve 310 and less than 85% of the ultimate tensile stress of the casing. Initially, a vertical gap remains between the third outer tube 600 and the upper end surface of the second tensile stress relief valve sleeve 610, allowing the third outer tube 600 to move downwardly and abut against the upper end surface of the second tensile stress relief valve sleeve 610.

[0041] Specifically, a fourth collapse point 611 is provided on the second tensile stress release valve sleeve 610. The ultimate stress that the fourth collapse point 611 on the second tensile stress release valve sleeve 610 can withstand is greater than the ultimate stress that the first collapse point 311 on the first tensile stress release valve sleeve 310 can withstand. That is, compared with the first collapse point 311, the fourth collapse point 611 is less likely to break.

[0042] During use, a stress reliever can be installed between every two vertically adjacent casings in a casing string consisting of multiple casings. That is, a plurality of stress relievers (one or more) can be provided. By providing the third outer tube 600 and the second tensile stress relief valve sleeve 610, when the casing string is subjected to tensile stress, both ends of the stress reliever located between two adjacent casings in the casing string will also be subjected to tension.

[0043] Taking one stress reliever as an example, when the casing string is subjected to tensile stress, the first pipe section 110 of the stress reliever tends to drive the first tensile stress relief valve sleeve 310 upward, and the first tensile stress relief valve sleeve 310 tends to drive the second tensile stress relief valve sleeve 610 upward through the connecting pipe 620. The second outer pipe 220, through the first outer pipe 210, tends to cause the first tensile stress relief valve sleeve 310 to move downward, and the second outer pipe 220 tends to cause the third outer pipe 600 to move downward closer to the second tensile stress relief valve sleeve 610. Because the ultimate stress that the fourth collapse point 611 can withstand is greater than that of the first collapse point 311, the first collapse point 311 will break first. After the first collapse point 311 is disconnected, the second tensile stress relief valve sleeve 610 is still supported between the inner tube 100 and the outer tube 200, thereby preventing slippage between the two and rendering other stress relievers unable to respond. The provision of the second tensile stress relief valve sleeve 610 ensures that the second tensile stress relief valve sleeve 610 will not begin to disconnect until the first tensile stress relief valve sleeves 310 of all stress relievers are disconnected, thereby extending the service life of the extreme stress relief device.

[0044] In another possible embodiment, a first elastic member 630 is disposed between the first outer tube 210 and the first tensile stress relief valve sleeve 310. The first elastic member 630 is disposed vertically and is a disc spring. An adjustment ring 640 is disposed between the first outer tube 210 and the third outer tube 600. The adjustment ring 640 is elastic, disposed vertically, and is capable of vertical expansion and contraction. Initially, there is a gap between the adjustment ring 640 and the third outer tube 600. In the radial direction of the third outer tube 600, the adjustment ring 640 is located between the third outer tube 600 and the connecting tube 620. Double-sided ratchet teeth 641 are disposed on the upper end of the adjustment ring 640. The double-sided ratchet teeth 641 engage with the connecting tube 620 and the third outer tube 600, respectively. The double-sided ratchet teeth 641 enable both the connecting tube 620 and the third outer tube 600 to move upward relative to the adjustment ring 640 and to move downward synchronously with the adjustment ring 640.

[0045] Among them, the third outer tube 600 includes a main tube 601, an installation tube section 602 and an engagement section 603. The main tube 601 is coaxial with the first outer tube 210 and is screwed to the first outer tube 210. The installation tube section 602 is located above the main tube 601, is coaxial with the main tube 601, and is screwed to the main tube 601. The second tensile stress relief valve sleeve 610 is located between the installation tube section 602 and the first tube section 110. The engagement section 603 is located between the main tube 601 and the installation tube section 602 and is fixed to the main tube 601. The engagement section 603 is ratcheted with the adjustment ring 640.

[0046] This embodiment further provides an adjustment ring 640 and a first elastic member 630 on the basis of the previous embodiment. When the casing string is subjected to fluctuating tensile stress caused by non-formation factors (the value of the fluctuating tensile stress is less than the set threshold of the first tensile stress release valve sleeve 310),

[0047] If the tensile stress applied to the casing string reaches a first preset value (the first preset value is less than the set threshold of the first tensile stress relief valve sleeve 310), the first pipe section 110 drives the first tensile stress relief valve sleeve 310 upward, compressing the first elastic member 630. This, through the first tensile stress relief valve sleeve 310, drives the connecting pipe 620 upward relative to the adjustment ring 640. At this point, the ratchet between the connecting pipe 620 and the adjustment ring 640 is inoperative. The second outer pipe 220 moves downward, compressing the first elastic member 630 through the first outer pipe 210. This in turn drives the third outer pipe 600 downward synchronously. The ratchet engagement of the third outer pipe 600 drives the upper end of the adjustment ring 640 downward synchronously. However, because the lower end of the adjustment ring 640 abuts the first outer pipe 210, the two ends of the adjustment ring 640 remain relatively stationary, preventing deformation of the adjustment ring 640.

[0048] If the tensile stress on the casing string changes to the second preset value (the second preset value is smaller than the first preset value), the first elastic member 630 is released, and the first tensile stress release valve sleeve 310 causes the first pipe section 110 to move downward relative to the adjustment ring 640, and the adjustment ring 640 is not affected by the movement of the first pipe section 110. The first outer tube 210 will move upward, and cause the lower end of the adjustment ring 640 to move upward, and the first outer tube 210 will cause the third outer tube 600 to move upward, causing the third outer tube 600 to move upward relative to the adjustment ring 640. At this time, the ratchet between the third outer tube 600 and the adjustment ring 640 does not work. That is, the lower end of the adjustment ring 640 approaches the upper end. And in the process of the casing string being subjected to fluctuating tensile stress, the adjustment ring 640 will continue to deform, and the adjustment ring 640 will be Figure 11 The state shown is transformed to Figure 12 During this process, the contact areas between the two end faces of the adjusting ring 640 in the radial direction of the outer sleeve 200 and the third outer tube 600 and the connecting tube 620 gradually increase, that is, the friction between the adjusting ring 640 and the third outer tube 600, as well as the friction between the adjusting ring 640 and the connecting tube 620, gradually increase.

[0049] During this process, if the tensile stress on the casing string caused by fluctuations in non-formation factors suddenly exceeds the set threshold of the first tensile stress relief valve sleeve 310, the first pipe section 110 drives the first tensile stress relief valve sleeve 310 upward, compressing the first elastic member 630. This, through the first tensile stress relief valve sleeve 310, drives the connecting pipe 620 upward relative to the adjustment ring 640. Due to the friction between the adjustment ring 640 and the connecting pipe 620, the tensile stress on the casing string will be partially offset by the friction. The second outer pipe 220 will then move downward, compressing the first elastic member 630 through the first outer pipe 210. This will drive the third outer pipe 600 downward synchronously, causing it to move downward relative to the adjustment ring 640. Due to the friction between the third outer pipe 600 and the adjustment ring 640, the tensile stress on the casing string will also be partially offset by the friction. Therefore, the first tensile stress relief valve sleeve 310 will not disconnect due to the temporary stress fluctuation.

[0050] Specifically, if the value of fluctuating tensile stress on the casing string, caused by factors other than the formation, suddenly exceeds the set threshold of the first tensile stress relief valve sleeve 310, and this tensile stress can be partially offset by the additional friction generated between the adjustment ring 640, the connecting pipe 620, and the third outer pipe 600, then within a certain range, the first tensile stress relief valve sleeve 310 will not disconnect due to short-term stress fluctuations. This allows the first tensile stress relief valve sleeve 310 to activate only when the stress reaches its limit, thereby improving the device's ability to distinguish between effective and interfering stresses. It should be noted that fluctuating compressive stress is not considered because it is very small and occurs infrequently.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An oil and gas well casing limit stress releaser, installed between two adjacent casings in a casing string, characterized by: The utility model comprises an inner tube and an outer tube, the outer tube and the inner tube are coaxially arranged in the vertical direction and sleeved with each other, the upper end of the inner tube is connected to the sleeve above it, and the lower end of the outer tube is connected to the sleeve below it; an upper buffer cavity and a lower buffer cavity are defined between the outer tube and the inner tube, the upper buffer cavity is located above the lower buffer cavity, and the upper buffer cavity and the lower buffer cavity are both filled with sealing fillers; a tensile stress release part is provided at the upper buffer cavity, a compressive stress release part is provided at the lower buffer cavity, and a torsional stress release part is also provided between the outer tube and the inner tube; in the initial state, the tensile stress release part limits the outer tube and the inner tube from moving away from each other in the vertical direction, and the compressive stress release part limits the outer tube and the inner tube When the outer sleeve and the inner sleeve are close to each other in the vertical direction, the torsional stress release part limits the relative rotation of the outer sleeve and the inner sleeve around the vertical direction; and when the tensile stress on the casing string is greater than the set threshold of the tensile stress release part, the tensile stress release part allows the outer sleeve and the inner sleeve to move away from each other in the vertical direction, and the upper buffer cavity is compressed at this time; when the compressive stress on the casing string is greater than the set threshold of the compressive stress release part, the compressive stress release part allows the outer sleeve and the inner sleeve to approach each other in the vertical direction, and the lower buffer cavity is compressed at this time; when the torsional stress on the casing string is greater than the set threshold of the torsional stress release part, the torsional stress release part allows the outer sleeve and the inner sleeve to rotate relative to each other around the vertical direction.

2. The oil and gas well casing limit stress reliever according to claim 1, characterized in that: The set threshold value of the tensile stress relief part is 70% of the ultimate tensile stress of the casing, the set threshold value of the compressive stress relief part is 70% of the ultimate compressive stress of the casing, and the set threshold value of the torsional stress relief part is 70% of the ultimate torsional stress of the casing.

3. The oil and gas well casing limit stress reliever according to claim 2, characterized in that: The outer sleeve includes a first outer tube and a second outer tube, which are both arranged in the vertical direction and are coaxial, and the first outer tube is located above the second outer tube and is screwed to the second outer tube; the lower end of the second outer tube is connected to the sleeve below it; the inner tube includes a first pipe section and a second pipe section, which are both coaxially arranged in the vertical direction, and the first pipe section is located above the second pipe section and is screwed to the second pipe section; the upper end of the first pipe section is connected to the sleeve above it; the second pipe section is provided with a first boss and a second boss arranged in the vertical direction, the first boss is located above the second boss, and the first boss and the second boss are both slidingly sealed with the inner wall of the first outer tube; the upper buffer chamber is defined by the first outer tube, the first pipe section and the first boss; the lower buffer chamber is defined by the first outer tube, the second pipe section and the second boss.

4. The oil and gas well casing limit stress reliever according to claim 3, characterized in that: A plurality of first bolts are provided at the threaded connection between the first outer tube and the second outer tube. The plurality of first bolts are evenly distributed in the vertical direction at the threaded connection between the first outer tube and the second outer tube.

5. The oil and gas well casing limit stress reliever according to claim 3, characterized in that: The tensile stress release member includes a first tensile stress release valve sleeve, which is provided with a first collapse point; a first edge is provided at the upper end of the first outer tube, and the first edge is located on the inner circumferential wall surface of the first outer tube; a second edge is provided on the outer circumferential wall surface of the first pipe section, and the first edge and the second edge are both located in the upper buffer cavity and respectively abut against the upper and lower end surfaces of the first tensile stress release valve sleeve.

6. The oil and gas well casing limit stress reliever according to claim 3, characterized in that: The pressure stress release component includes a pressure stress release valve sleeve, which is installed at the lower end of the second pipe section and is provided with a second collapse point; the lower end surface of the second pipe section abuts against the upper end surface of the pressure stress release valve sleeve, and the upper end surface of the second outer tube abuts against the lower end surface of the pressure stress release valve sleeve.

7. The oil and gas well casing limit stress reliever according to claim 3, characterized in that: A torsion cavity is defined between the first outer tube, the second tube section, the first boss and the second boss. In the vertical direction, the torsion cavity is located between the upper buffer cavity and the lower buffer cavity. The torsion stress release member is installed in the torsion cavity.

8. The oil and gas well casing limit stress reliever according to claim 7, characterized in that: The torsional stress release part includes a torsional stress release pin, which is arranged along the radial direction of the first outer tube and inserted into the torsional cavity along the radial direction of the first outer tube. A sliding groove for slidingly cooperating with the torsional stress release pin is provided on the second tube section, and the sliding groove is arranged along the vertical direction; a third collapse point is provided on the torsional stress release pin.

9. The oil and gas well casing limit stress reliever according to claim 5, characterized in that: A third outer tube is screwed to the upper end of the first outer tube, and the third outer tube is coaxial with the first outer tube. A second tensile stress release valve sleeve and a connecting pipe are provided between the third outer tube and the first pipe section. In the vertical direction, the connecting pipe is located between the first tensile stress release valve sleeve and the second tensile stress release valve sleeve, and abuts against the first tensile stress release valve sleeve and the second tensile stress release valve sleeve; a set threshold value of the second tensile stress release valve sleeve is greater than a set threshold value of the first tensile stress release valve sleeve and is less than 85% of the ultimate tensile stress of the sleeve. In the initial state, a gap is left between the third outer tube and the upper end surface of the second tensile stress release valve sleeve in the vertical direction, and the third outer tube can abut against the upper end surface of the second tensile stress release valve sleeve when it moves downward.

10. The oil and gas well casing limit stress reliever according to claim 9, characterized in that: A first elastic member is provided between the first outer tube and the first tensile stress release valve sleeve, and the first elastic member is provided in the vertical direction; an adjusting ring is provided between the first outer tube and the third outer tube, the adjusting ring is elastic, and is provided in the vertical direction and can be expanded and contracted in the vertical direction. In the initial state, there is a distance between the adjusting ring and the third outer tube, and in the radial direction of the third outer tube, the adjusting ring is located between the third outer tube and the connecting tube, and double-sided ratchet teeth are provided on the adjusting ring, and the double-sided ratchet teeth are respectively engaged with the connecting tube and the third outer tube, and the double-sided ratchet teeth enable the connecting tube and the third outer tube to move up relative to the adjusting ring and move down synchronously with the adjusting ring.

Images