A casing stress limiter for oil and gas wells

Abstract

The present application relates to the technical fields of oil and gas well casing protection, and particularly relates to an oil and gas well casing ultimate stress releaser, which comprises an inner tube and an outer sleeve, the outer sleeve and the inner tube are coaxially arranged along the vertical direction and are sleeved with each other, the upper buffer cavity and the lower buffer cavity are defined between the outer sleeve and the inner tube, and the upper buffer cavity and the lower buffer cavity are both filled with sealing filler. The tensile stress release part is arranged at the upper buffer cavity, the compressive stress release part is arranged at the lower buffer cavity, and the torsional stress release part is arranged between the outer sleeve and the inner tube. The oil and gas well casing ultimate stress releaser makes the tensile stress release part, the compressive stress release part and the torsional stress release part start respectively when the corresponding threshold value is exceeded, so as to actively release the tensile stress, the compressive stress and the torsional stress. The comprehensive release mechanism for various stresses is provided, and the overall protection effect of the casing is significantly improved, and the service life of the oil and gas well is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas well casing protection, and particularly relates to an oil and gas well casing limit stress releaser. BACKGROUND

[0002] In the oil and gas well exploitation, the casing string is a key component for ensuring the stability of the well wall, separating different formation fluids and supporting the downhole equipment, and the performance and safety of the casing string are crucial to the oil and gas exploitation operation. However, in the actual exploitation process, the casing string is long-term exposed to the complex and changeable downhole environment, and is often affected by various factors such as formation movement, temperature change and fluid pressure fluctuation, and then bears various forms of loads such as tensile stress, compressive stress and torsional stress.

[0003] For example, when the formation is subjected to tectonic movement, the casing is subjected to extrusion or stretching, and generates compressive stress or tensile stress. The frequent fluctuation of fluid pressure, especially when different operation links such as drilling, oil production and gas injection are alternated, will make the casing bear periodic stress changes, and at the same time, the torsional stress will be generated in the casing rotation operation or the torque transmission process of the downhole tool. Once these stresses exceed or approach the limit bearing value of the casing, the casing will be easily deformed, broken and other serious problems, which not only will cause the oil and gas well to reduce or even stop production, increase the exploitation cost, but also may cause blowout, oil and gas leakage and other major safety accidents, which pose a great threat to personnel safety and ecological environment. At present, the stress release devices in the prior art mostly only protect against a single stress type, and when facing complex combined working conditions, the protection effect is greatly reduced, and the actual complex stress environment in the downhole cannot be met. SUMMARY

[0004] The present application provides an oil and gas well casing limit stress releaser, which monitors and actively releases the tensile stress, compressive stress and torsional stress in real time, so as to solve the problem that the existing stress release devices mostly only protect against a single stress type, lack of comprehensive release mechanism for multiple stresses, and cannot meet the demand of the actual complex stress environment in the downhole when facing complex combined working conditions.

[0005] The oil and gas well casing ultimate stress releaser adopts the following technical scheme: an oil and gas well casing ultimate stress releaser is installed between two casings arranged adjacently in a casing string, comprising an inner pipe and an outer sleeve, the outer sleeve and the inner pipe are coaxially arranged along the vertical direction and are sleeved with each other, the upper end of the inner pipe is connected with the casing above it, and the lower end of the outer sleeve is connected with the casing below it; the upper buffer cavity and the lower buffer cavity are defined between the outer sleeve and the inner pipe, 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 filler; the tensile stress releasing part is arranged at the upper buffer cavity, the compressive stress releasing part is arranged at the lower buffer cavity, and the torsional stress releasing part is further arranged between the outer sleeve and the inner pipe; in the initial state, the tensile stress releasing part limits the outer sleeve and the inner pipe from moving away from each other in the vertical direction, the compressive stress releasing part limits the outer sleeve and the inner pipe from moving close to each other in the vertical direction, and the torsional stress releasing part limits the outer sleeve and the inner pipe from rotating relative to each other around the vertical direction; and when the tensile stress of the casing string is greater than the set threshold value of the tensile stress releasing part, the tensile stress releasing part allows the outer sleeve and the inner pipe to move away from each other in the vertical direction, and at this time, the upper buffer cavity is compressed; when the compressive stress of the casing string is greater than the set threshold value of the compressive stress releasing part, the compressive stress releasing part allows the outer sleeve and the inner pipe to move close to each other in the vertical direction, and at this time, the lower buffer cavity is compressed; and when the torsional stress of the casing string is greater than the set threshold value of the torsional stress releasing part, the torsional stress releasing part allows the outer sleeve and the inner pipe to rotate relative to each other around the vertical direction.

[0006] Further, the set threshold value of the tensile stress releasing part is 70% of the casing ultimate tensile stress, the set threshold value of the compressive stress releasing part is 70% of the casing ultimate compressive stress, and the set threshold value of the torsional stress releasing part is 70% of the casing ultimate torsional stress.

[0007] Further, the outer sleeve comprises a first outer pipe and a second outer pipe, the first outer pipe and the second outer pipe are both arranged along the vertical direction and are coaxial, the first outer pipe is located above the second outer pipe and is screwed with the second outer pipe; the lower end of the second outer pipe is connected with the casing below it; the inner pipe comprises a first pipe segment and a second pipe segment, the first pipe segment and the second pipe segment are both coaxially arranged along the vertical direction, the first pipe segment is located above the second pipe segment and is screwed with the second pipe segment; the upper end of the first pipe segment is connected with the casing above it; the second pipe segment is provided with a first boss and a second boss arranged along the vertical direction, the first boss is located above the second boss, and the first boss and the second boss are both in sliding sealing with the inner wall of the first outer pipe; the upper buffer cavity is defined by the first outer pipe, the first pipe segment and the first boss; and the lower buffer cavity is defined by the first outer pipe, the second pipe segment and the second boss.

[0008] Further, a plurality of first bolts are arranged at the screwing part of the first outer pipe and the second outer pipe, and the plurality of first bolts are uniformly distributed around the vertical direction at the screwing part of the first outer pipe and the second outer pipe.

[0009] Further, the tensile stress release member comprises a first tensile stress release valve sleeve, the first tensile stress release valve sleeve is provided with a first collapse point, the upper end of the first outer pipe is provided with a first edge, the first edge is located on the inner circumferential wall surface of the first outer pipe, the outer circumferential wall surface of the first pipe segment is provided with a second edge, the first edge and the second edge are both located in the upper buffer cavity and abut against the upper and lower end surfaces of the first tensile stress release valve sleeve respectively.

[0010] Further, the compressive stress release member comprises a compressive stress release valve sleeve, the compressive stress release valve sleeve is installed on the lower end of the second pipe segment, the compressive stress release valve sleeve is provided with a second collapse point, the lower end surface of the second pipe segment abuts against the upper end surface of the compressive stress release valve sleeve, and the upper end surface of the second outer pipe abuts against the lower end surface of the compressive stress release valve sleeve.

[0011] Further, the torsional stress release member is installed in the torsional cavity.

[0012] Further, the torsional stress release member comprises a torsional stress release pin, the torsional stress release pin is arranged in the radial direction of the first outer pipe and is inserted into the torsional cavity in the radial direction of the first outer pipe, the second pipe segment is provided with a sliding groove for slidingly cooperating with the torsional stress release pin, and the sliding groove is arranged in the vertical direction; the torsional stress release pin is provided with a third collapse point.

[0013] Further, the upper end of the first outer pipe is screwed with a third outer pipe, the third outer pipe is coaxial with the first outer pipe, and the third outer pipe and the first pipe segment are provided with a second tensile stress release valve sleeve and a connecting pipe, 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 in the vertical direction; the set threshold value of the second tensile stress release valve sleeve is greater than the set threshold value of the first tensile stress release valve sleeve and less than 85% of the casing ultimate tensile stress, and the third outer pipe is spaced apart from the upper end surface of the second tensile stress release valve sleeve in the vertical direction in the initial state, and the third outer pipe can abut against the upper end surface of the second tensile stress release valve sleeve by moving downward.

[0014] Further, the first outer pipe and the first tensile stress release valve sleeve are provided with a first elastic member, the first elastic member is arranged in the vertical direction; the first outer pipe and the third outer pipe are provided with an adjusting ring, the adjusting ring has elasticity, the adjusting ring is arranged in the vertical direction and can be extended and retracted in the vertical direction, there is a space between the adjusting ring and the third outer pipe in the initial state, and the adjusting ring is located between the third outer pipe and the connecting pipe in the radial direction of the third outer pipe, the adjusting ring is provided with a double-sided ratchet, the double-sided ratchet is engaged with the connecting pipe and the third outer pipe respectively, and the double-sided ratchet enables the connecting pipe and the third outer pipe to move upward relative to the adjusting ring and to move downward synchronously with the adjusting ring.

[0015] The beneficial effects of this invention are as follows: The oil and gas well casing ultimate stress release device of this invention features an outer sleeve that engages with the inner tube. By monitoring the stress on the casing string in real time, the tensile stress release component, compressive stress release component, and torsional stress release component are activated when their corresponding thresholds are exceeded. This allows relative movement between the outer sleeve and the inner tube, thereby proactively releasing tensile, compressive, and torsional stresses in a targeted manner. Compared to a single stress protection device, it possesses a comprehensive stress release mechanism for multiple stresses, capable of handling multiple stresses simultaneously. Even when facing complex combinations of working conditions, it can still meet the needs of the complex downhole stress environment, significantly improving the overall protection effect of the casing and extending the service life of the oil and gas well. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the ultimate stress relief device for oil and gas well casing according to the present invention;

[0018] Figure 2 This is a front view of the overall structure of an embodiment of the ultimate stress relief device for oil and gas well casing according to the present invention;

[0019] Figure 3 for Figure 2 Sectional view at point AA along the middle;

[0020] Figure 4 for Figure 3 Enlarged view of point B in the middle;

[0021] Figure 5 for Figure 3 Enlarged view of point C in the middle;

[0022] Figure 6 for Figure 3 Enlarged view of point D in the middle;

[0023] Figure 7 This is a schematic diagram of the overall structure of a second embodiment of the ultimate stress relief device for oil and gas well casing according to the present invention;

[0024] Figure 8 This is a front view of the overall structure of a second embodiment of the ultimate stress relief device for oil and gas well casing according to the present invention;

[0025] Figure 9 for Figure 8A sectional view along E-E;

[0026] Figure 10 As Figure 9 An enlarged view at F;

[0027] Figure 11 As Figure 10 An enlarged view at G;

[0028] Figure 12 A compressed state diagram of the adjusting ring of the second embodiment of the oil and gas well casing limit stress releaser of the present application;

[0029] Figure 13 A split diagram of the overall structure of the second embodiment of the oil and gas well casing limit stress releaser of the present application.

[0030] 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 cavity; 310, first tensile stress release sleeve; 311, first collapse point; 400, lower buffer cavity; 410, compressive stress release sleeve; 411, second collapse point; 500, torsional stress release pin; 501, third collapse point; 510, torsional cavity; 600, third outer tube; 601, main tube; 602, mounting tube section; 603, engagement section; 604, second bolt; 610, second tensile stress release sleeve; 611, fourth collapse point; 620, connecting tube; 630, first elastic member; 640, adjusting ring; 641, double-sided ratchet. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0032] An embodiment of the oil and gas well casing limit stress releaser of the present application is shown in Figures 1 to 13 .

[0033] Embodiment I:

[0034] Referring to Figures 1 to 6As shown, an oil and gas well casing extreme stress releaser is installed between two casings arranged adjacently in a casing string (not shown in the casing string specification drawing, the casing string is composed of a plurality of casings arranged in sequence along the vertical direction), comprising an inner tube 100 and an outer sleeve 200, the outer sleeve 200 and the inner tube 100 are coaxially arranged along the vertical direction, the outer sleeve 200 is sleeved with the inner tube 100, the upper end of the inner tube 100 is connected with the casing above it, and the lower end of the outer sleeve 200 is connected with the casing below it. The outer sleeve 200 and the inner tube 100 define an upper buffer cavity 300 and a lower buffer cavity 400 arranged in sequence along the vertical direction, the upper buffer cavity 300 is located above the lower buffer cavity 400, and the upper buffer cavity 300 and the lower buffer cavity 400 are both filled with sealing filler. A tensile stress release member is arranged at the upper buffer cavity 300, a compressive stress release member is arranged at the lower buffer cavity 400, and a torsional stress release member is arranged between the outer sleeve 200 and the inner tube 100.

[0035] 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 close to 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 around the vertical direction; and when the tensile stress of 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 of 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 close to each other in the vertical direction, and at this time the lower buffer cavity 400 is compressed; and when the torsional stress of 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 around the vertical direction.

[0036] Specifically, the upper end of the inner tube 100 is connected with the casing above it, and the lower end of the outer sleeve 200 is connected with the casing below it. Therefore, when the casing string is subjected to tensile stress, the inner tube 100 and the outer sleeve 200 tend to move away from each other in the vertical direction; and when the casing string is subjected to compressive stress, the inner tube 100 and the outer sleeve 200 tend to move close to each other in the vertical direction.

[0037] The outer sleeve 200 and the inner tube 100 are arranged in the present embodiment, and by monitoring the stress condition of the casing string in real time, the tensile stress release member, the compressive stress release member and the torsional stress release member are respectively started when the corresponding threshold is exceeded, allowing the outer sleeve 200 and the inner tube 100 to move relative to each other, thereby actively releasing the tensile stress, the compressive stress and the torsional stress.

[0038] Specifically, when the tensile stress of the casing string exceeds the threshold value, the tensile stress release member of the upper buffer cavity 300 allows the outer sleeve 200 to move away from the inner tube 100 and compress the upper buffer cavity 300, releasing the tensile stress; when the compressive stress of the casing string exceeds the threshold value, the compressive stress release member of the lower buffer cavity 400 allows the outer sleeve 200 to move close to the inner tube 100 and compress the lower buffer cavity 400, releasing the compressive stress; when the torsional stress of the casing string exceeds the threshold value, the torsional stress release member allows the outer sleeve 200 to rotate relative to the inner tube 100, releasing the torsional stress. Compared with a single stress protection device, the comprehensive release mechanism for multiple stresses can handle multiple stresses at the same time, and when faced with complex combined working conditions, it can still meet the needs of the actual downhole complex stress environment, significantly improving the overall protection effect of the casing, ensuring the long-term safe operation of the oil and gas well, reducing maintenance costs, and prolonging the service life of the oil and gas well.

[0039] In the embodiment, the set threshold value of the tensile stress release member is 70% of the casing ultimate tensile stress, the set threshold value of the compressive stress release member is 70% of the casing ultimate compressive stress, and the set threshold value of the torsional stress release member is 70% of the casing ultimate torsional stress.

[0040] The tensile stress release member, the compressive stress release member, and the torsional stress release member all realize directional release of stress only when the stress reaches the set threshold value. By intervening in advance, the risk of stress overload is reduced, and the tensile stress, the compressive stress, and the torsional stress exceeding the limit value are released, which can reduce the probability of damage such as deformation and fracture of the casing, and reduce the maintenance cost of the oil and gas well.

[0041] In the embodiment, the outer sleeve 200 includes a first outer tube 210 and a second outer tube 220, both of which are arranged in the vertical direction and coaxially, and the first outer tube 210 is located above the second outer tube 220 and is screwed with the second outer tube 220. The lower end of the second outer tube 220 is connected with the casing below it. And the screwing place of the first outer tube 210 and the second outer tube 220 is provided with a plurality of first bolts 211, which are uniformly distributed around the vertical direction at the screwing place of the first outer tube 210 and the second outer tube 220.

[0042] The inner tube 100 comprises a first tube segment 110 and a second tube segment 120, both of which are coaxially arranged along the vertical direction, and the first tube segment 110 is located above the second tube segment 120 and is screwed with the second tube segment 120. The upper end of the first tube segment 110 is connected with the casing pipe above it. The second tube segment 120 is provided with a first boss 121 and a second boss 122 arranged along the vertical direction, the first boss 121 is located above the second boss 122, and both of the first boss 121 and the second boss 122 are in sliding seal with the inner wall of the first outer tube 210. The upper buffer cavity 300 is defined by the first outer tube 210, the first tube segment 110 and the first boss 121. The lower buffer cavity 400 is defined by the first outer tube 210, the second tube segment 120 and the second boss 122.

[0043] The torsion cavity 510 is defined between the first outer tube 210, the second tube segment 120, the first boss 121 and the second boss 122, and in the vertical direction, the torsion cavity 510 is located between the upper buffer cavity 300 and the lower buffer cavity 400. The torsion stress release member is installed in the torsion cavity 510.

[0044] In the embodiment, the tensile stress release member comprises a first tensile stress release valve sleeve 310, and the first tensile stress release valve sleeve 310 is provided with a first collapse point 311. The upper end of the first outer tube 210 is provided with a first rim 212, which is located on the inner peripheral wall surface of the first outer tube 210. The outer peripheral wall surface of the first tube segment 110 is provided with a second rim 111, and both of the first rim 212 and the second rim 111 are located in the upper buffer cavity 300 and abut against the upper and lower end faces of the first tensile stress release valve sleeve 310 respectively.

[0045] When the casing string is subjected to tensile stress, the first tube segment 110 is subjected to upward force, so that the first tube segment 110 has a tendency to move upward with the second tube segment 120. At this time, the second rim 111 of the first tube segment 110 has a tendency to promote the upward movement of the first tensile stress release valve sleeve 310. Meanwhile, the second outer tube 220 is subjected to downward force, so that the second outer tube 220 has a tendency to move downward with the first outer tube 210. At this time, the first rim 212 of the first outer tube 210 has a tendency to promote the downward movement of the first tensile stress release valve sleeve 310. When the tensile stress of the casing string is greater than the set threshold value of the first tensile stress release valve sleeve 310, the first tensile stress release valve sleeve 310 will be broken at the first collapse point 311.

[0046] The compressive stress release member comprises a compressive stress release valve sleeve 410, which is located at the lower end of the second tube segment 120 and is screwed with the second tube segment 120. The compressive stress release valve sleeve 410 is provided with a second collapse point 411. The lower end surface of the second tube segment 120 abuts against the upper end surface of the compressive stress release valve sleeve 410, and the upper end surface of the second outer tube 220 abuts against the lower end surface of the compressive stress release valve sleeve 410.

[0047] When the casing string is subjected to a compressive stress, the first pipe segment 110 is subjected to a downward force, which causes the first pipe segment 110 to have a tendency to move the second pipe segment 120 downward, at this time, the lower end surface of the second pipe segment 120 will have a tendency to move the compressive stress release valve sleeve 410 downward. And the second outer pipe 220 has a tendency to move the first outer pipe 210 upward, and at this time, the upper end surface of the second outer pipe 220 will have a tendency to move the compressive stress release valve sleeve 410 upward. And when the compressive stress of the casing string is greater than the set threshold value of the compressive stress release valve sleeve 410, the compressive stress release valve sleeve 410 will be broken from the second fracture point 411.

[0048] The torsional stress release member includes a torsional stress release pin 500, which is arranged in the radial direction of the first outer pipe 210 and is inserted into the torsional cavity 510 in the radial direction of the first outer pipe 210. The second pipe segment 120 is provided with a sliding groove for sliding cooperation with the torsional stress release pin 500, and the sliding groove is arranged in the vertical direction. The torsional stress release pin 500 is provided with a third fracture point 501.

[0049] When the casing string is subjected to a torsional stress, the first pipe segment 110 has a tendency to rotate the second pipe segment 120 around the vertical direction, and the second outer pipe 220 has a tendency to rotate the first outer pipe 210 around the vertical direction, and the directions of rotation of the two are opposite, but because the torsional stress release pin 500 is in key groove cooperation with the second pipe segment 120, the relative rotation of the two is limited. When the torsional stress of the casing string is greater than the set threshold value of the torsional stress release pin 500, the torsional stress release pin 500 will be broken from the third fracture point 501, and the torsional stress release pin 500 will be sheared. And when the casing string is subjected to a tensile stress or a compressive stress, the torsional stress release pin 500 can slide in the sliding groove, and does not affect the release of the tensile stress or the compressive stress.

[0050] Embodiment two:

[0051] Referring to Figures 7 to 13 The difference between the embodiment one and the embodiment two is that the upper end of the first outer pipe 210 is screwed with a third outer pipe 600, the third outer pipe 600 is coaxial with the first outer pipe 210, and a plurality of second bolts 604 are arranged at the screwing position of the third outer pipe 600 and the first outer pipe 210, and the plurality of second bolts 604 are uniformly distributed around the vertical direction at the screwing position of the third outer pipe 600 and the first outer pipe 210.

[0052] The third outer tube 600 is provided with a second tensile stress release valve sleeve 610 and a connecting tube 620 between the first tube segment 110, the connecting tube 620 is located between the first tensile stress release valve sleeve 310 and the second tensile stress release valve sleeve 610 in the vertical direction and abuts against the first tensile stress release valve sleeve 310 and the second tensile stress release valve sleeve 610. The set threshold of the second tensile stress release valve sleeve 610 is greater than the set threshold of the first tensile stress release valve sleeve 310 and less than 85% of the casing ultimate tensile stress. In the initial state, the third outer tube 600 is spaced apart from the upper end surface of the second tensile stress release valve sleeve 610 in the vertical direction, and the third outer tube 600 can abut against the upper end surface of the second tensile stress release valve sleeve 610 by moving downward.

[0053] Specifically, the second tensile stress release valve sleeve 610 is provided with a fourth collapse point 611, and 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.

[0054] In use, in a casing string composed of a plurality of casings, a stress release device can be provided between every two casings arranged adjacent in the vertical direction. That is, the stress release device can be provided several times (greater than or equal to one). By providing the third outer tube 600 and the second tensile stress release valve sleeve 610, when the casing string is subjected to tensile stress, the two ends of the stress release device located between two casings arranged adjacent in the casing string will also be subjected to tension.

[0055] Taking one of the stress release devices as an example, when the casing string is subjected to tensile stress, the first tube segment 110 of the stress release device has a tendency to drive the first tensile stress release valve sleeve 310 to move upward, and the first tensile stress release valve sleeve 310 has a tendency to drive the second tensile stress release valve sleeve 610 to move upward through the connecting tube 620. The second outer tube 220 has a tendency to drive the third outer tube 600 to move downward and close to the second tensile stress release valve sleeve 610 by the first outer tube 210. Because the ultimate stress that the fourth collapse point 611 can withstand is greater than the ultimate stress that the first collapse point 311 can withstand, the first collapse point 311 will break first. After the first collapse point 311 breaks, the second tensile stress release valve sleeve 610 still supports between the inner tube 100 and the outer sleeve 200 to prevent the sliding phenomenon between them, so that other stress release devices cannot respond. The provision of the second tensile stress release valve sleeve 610 can make the second tensile stress release valve sleeve 610 start to break only after all the first tensile stress release valve sleeves 310 of the stress release devices break, thereby prolonging the service life of the ultimate stress release device.

[0056] In another possible embodiment, a first elastic member 630 is arranged between the first outer tube 210 and the first tensile stress relief valve sleeve 310, the first elastic member 630 is arranged in the vertical direction, and the first elastic member 630 is a disc spring. An adjusting ring 640 is arranged between the first outer tube 210 and the third outer tube 600, the adjusting ring 640 is elastic, the adjusting ring 640 is arranged in the vertical direction and can be telescoped in the vertical direction, there is a gap between the adjusting ring 640 and the third outer tube 600 in the initial state, and in the radial direction of the third outer tube 600, the adjusting ring 640 is located between the third outer tube 600 and the connecting tube 620, the upper end of the adjusting ring 640 is provided with a double-sided ratchet 641, the double-sided ratchet 641 is engaged with the connecting tube 620 and the third outer tube 600 respectively, and the double-sided ratchet 641 enables the connecting tube 620 and the third outer tube 600 to be moved upward relative to the adjusting ring 640 and to be moved downward synchronously with the adjusting ring 640.

[0057] The third outer tube 600 includes a main tube 601, a mounting tube segment 602, and an engagement segment 603. The main tube 601 is coaxial with the first outer tube 210 and is screwed with the first outer tube 210. The mounting tube segment 602 is located above the main tube 601, coaxial with the main tube 601 and screwed with the main tube 601. The second tensile stress relief valve sleeve 610 is located between the mounting tube segment 602 and the first tube segment 110. The engagement segment 603 is located between the main tube 601 and the mounting tube segment 602 and is fixedly connected with the main tube 601. The engagement segment 603 is ratchet-matched with the adjusting ring 640.

[0058] The adjusting ring 640 and the first elastic member 630 are further arranged on the basis of the previous embodiment. In the process that the casing string is subjected to the fluctuating tensile stress generated by non-formation factors (the value of the fluctuating tensile stress is less than the set threshold of the first tensile stress relief valve sleeve 310).

[0059] If the casing string is subjected to the first preset value of the tensile stress (the first preset value is less than the set threshold of the first tensile stress relief valve sleeve 310), the first tube segment 110 drives the first tensile stress relief valve sleeve 310 to move upward, compresses the first elastic member 630, and drives the connecting tube 620 to move upward relative to the adjusting ring 640 through the first tensile stress relief valve sleeve 310. At this time, the ratchet between the connecting tube 620 and the adjusting ring 640 does not work. The second outer tube 220 will move downward and compress the first elastic member 630 through the first outer tube 210. The first outer tube 210 will drive the third outer tube 600 to move downward synchronously. The third outer tube 600 will drive the upper end of the adjusting ring 640 to move downward synchronously through the ratchet matching. However, the lower end of the adjusting ring 640 abuts against the first outer tube 210 at this time, and the two ends of the adjusting ring 640 remain relatively stationary. Therefore, the adjusting ring 640 will not be deformed.

[0060] If the tensile stress on the casing string becomes 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 pipe section 110 is moved downward relative to the adjusting ring 640 through the first tensile stress release valve sleeve 310, and the adjusting ring 640 is not affected by the movement of the first pipe section 110. At this time, the first outer pipe 210 is moved upward, and the lower end of the adjusting ring 640 is moved upward, and the first outer pipe 210 promotes the upward movement of the third outer pipe 600, so that the third outer pipe 600 is moved upward relative to the adjusting ring 640, and the ratchet between the third outer pipe 600 and the adjusting ring 640 does not work. That is, the lower end of the adjusting ring 640 is close to the upper end. During the fluctuation of the tensile stress on the casing string, the adjusting ring 640 is deformed from the state shown in FIG. 8 to the state shown in FIG. 9. During this process, the contact area between the two end surfaces of the adjusting ring 640 in the radial direction of the outer sleeve 200 and the third outer pipe 600 and the connecting pipe 620 gradually increases, that is, the friction between the adjusting ring 640 and the third outer pipe 600 and the friction between the adjusting ring 640 and the connecting pipe 620 gradually increases. Figure 11 Figure 12 During this process, if the value of the fluctuating tensile stress generated by non-formation factors on the casing string suddenly exceeds the set threshold of the first tensile stress release valve sleeve 310, when the first pipe section 110 moves upward to compress the first elastic member 630 and moves the connecting pipe 620 upward relative to the adjusting ring 640 through the first tensile stress release valve sleeve 310, due to the friction between the adjusting ring 640 and the connecting pipe 620, the tensile stress on the casing string is offset by a part of the friction. At this time, the second outer pipe 220 is moved downward, and the first elastic member 630 is compressed through the first outer pipe 210, and the first outer pipe 210 moves synchronously with the third outer pipe 600, so that the third outer pipe 600 is moved downward relative to the adjusting ring 640, and due to the friction between the third outer pipe 600 and the adjusting ring 640, the tensile stress on the casing string is offset by a part of the friction. Therefore, at this time, the first tensile stress release valve sleeve 310 will not be disconnected due to the short-term stress fluctuation.

[0061] That is, if the value of the fluctuating tensile stress generated by non-formation factors on the casing string suddenly exceeds the set threshold of the first tensile stress release valve sleeve 310, and the tensile stress can be offset by a part of the additional friction between the adjusting ring 640 and the connecting pipe 620 and the third outer pipe 600, so that within a certain range, the first tensile stress release valve sleeve 310 will not be disconnected due to the short-term stress fluctuation, and the first tensile stress release valve sleeve 310 is only activated when the stress reaches the limit, which improves the discrimination ability of the device to the effective stress and the interference stress. It should be particularly pointed out that the fluctuating compressive stress is not considered because it is very small and has a low frequency.

[0062] That is, if the value of the fluctuating tensile stress generated by non-formation factors on the casing string suddenly exceeds the set threshold of the first tensile stress release valve sleeve 310, and the tensile stress can be offset by a part of the additional friction between the adjusting ring 640 and the connecting pipe 620 and the third outer pipe 600, so that within a certain range, the first tensile stress release valve sleeve 310 will not be disconnected due to the short-term stress fluctuation, and the first tensile stress release valve sleeve 310 is only activated when the stress reaches the limit, which improves the discrimination ability of the device to the effective stress and the interference stress. It should be particularly pointed out that the fluctuating compressive stress is not considered because it is very small and has a low frequency. ​

[0063] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A casing stress riser for an oil and gas well, installed between two casings located adjacent to each other in a casing string, characterized in that: The device comprises an inner tube and an outer sleeve, the outer sleeve and the inner tube are coaxially arranged in the vertical direction and are sleeved with each other, the upper end of the inner tube is connected with the sleeve above it, and the lower end of the outer sleeve is connected with the sleeve below it; the upper buffer cavity and the lower buffer cavity are defined between the outer sleeve and the inner tube, the upper buffer cavity is above the lower buffer cavity, and the upper buffer cavity and the lower buffer cavity are both filled with sealing filler; the tensile stress release part is arranged at the upper buffer cavity, the compressive stress release part is arranged at the lower buffer cavity, and the torsional stress release part is arranged between the outer sleeve and the inner tube; in the initial state, the tensile stress release part limits the outer sleeve and the inner tube from moving away from each other in the vertical direction, the compressive stress release part limits the outer sleeve and the inner tube from moving close to each other in the vertical direction, and the torsional stress release part limits the outer sleeve and the inner tube from rotating relative to each other around the vertical direction; when the tensile stress of the sleeve 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 tube to move away from each other in the vertical direction, and at this time, the upper buffer cavity is compressed; when the compressive stress of the sleeve 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 tube to move close to each other in the vertical direction, and at this time, the lower buffer cavity is compressed; when the torsional stress of the sleeve 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 tube to rotate relative to each other around the vertical direction; the outer sleeve comprises a first outer tube and a second outer tube, the first outer tube and the second outer tube are arranged in the vertical direction and are coaxial, the first outer tube is above the second outer tube and is screwed with the second outer tube; the lower end of the second outer tube is connected with the sleeve below it; the inner tube comprises a first tube segment and a second tube segment, the first tube segment and the second tube segment are coaxially arranged in the vertical direction, the first tube segment is above the second tube segment and is screwed with the second tube segment; the upper end of the first tube segment is connected with the sleeve above it; the tensile stress release part comprises a first tensile stress release valve sleeve, and a first collapse point is arranged on the first tensile stress release valve sleeve; the upper end of the first outer tube is provided with a first edge, the first edge is located on the inner circumferential wall surface of the first outer tube, a second edge is arranged on the outer circumferential wall surface of the first tube segment, 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 faces of the first tensile stress release valve sleeve; the compressive stress release part comprises a compressive stress release valve sleeve, the compressive stress release valve sleeve is installed on the lower end of the second tube segment, and a second collapse point is arranged on the compressive stress release valve sleeve; the lower end face of the second tube segment abuts against the upper end face of the compressive stress release valve sleeve, and the upper end face of the second outer tube abuts against the lower end face of the compressive stress release valve sleeve; the torsional stress release part comprises a torsional stress release pin, the torsional stress release pin is arranged in the radial direction of the first outer tube, a sliding groove for slidingly cooperating with the torsional stress release pin is arranged on the second tube segment, and the sliding groove is arranged in the vertical direction; a third collapse point is arranged on the torsional stress release pin; the second tube segment is provided with a first boss and a second boss which are arranged in the vertical direction, the first boss is above the second boss, and the first boss and the second boss are both in sliding sealing with the inner wall of the first outer tube; the upper buffer cavity is defined by the first outer tube, the first tube segment and the first boss; and the lower buffer cavity is defined by the first outer tube, the second tube segment and the second boss.The first outer tube, the second tube segment, the first boss and the second boss define a torsion cavity therebetween, and in the vertical direction, the torsion cavity is located between the upper buffer cavity and the lower buffer cavity, and a torsion stress release member is installed in the torsion cavity.

2. An oil and gas well casing extreme stress reliever according to claim 1, characterized in that: The set threshold of the tensile stress release member is 70% of the casing ultimate tensile stress, the set threshold of the compressive stress release member is 70% of the casing ultimate compressive stress, and the set threshold of the torsional stress release member is 70% of the casing ultimate torsional stress.

3. An oil and gas well casing extreme stress reliever according to claim 1, characterized in that: The screw joint of the first outer tube and the second outer tube is provided with a plurality of first bolts, which are uniformly distributed around the vertical direction at the screw joint of the first outer tube and the second outer tube.

4. An oil and gas well casing extreme stress reliever according to claim 1, characterized in that: The torsional stress release pin is inserted into the torsional cavity along the radial direction of the first outer tube.

5. An oil and gas well casing extreme stress reliever according to claim 1, characterized in that: The third outer tube is screwed on the upper end of the first outer tube, the third outer tube is coaxial with the first outer tube, and the second tensile stress release valve sleeve and the connecting pipe are arranged between the third outer tube and the first pipe segment. 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; the set threshold of the second tensile stress release valve sleeve is greater than the set threshold of the first tensile stress release valve sleeve and less than 85% of the casing ultimate tensile stress; in the initial state, the third outer tube is spaced apart from 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 by moving downward.

6. An oil and gas well casing extreme stress reliever according to claim 5, characterized in that: A first elastic member is arranged between the first outer tube and the first tensile stress release valve sleeve, and the first elastic member is arranged in the vertical direction; an adjusting ring is arranged between the first outer tube and the third outer tube, the adjusting ring has elasticity, the adjusting ring is arranged in the vertical direction and can be stretched and contracted in the vertical direction, there is a space between the adjusting ring and the third outer tube in the initial state, and in the radial direction of the third outer tube, the adjusting ring is located between the third outer tube and the connecting pipe; the adjusting ring is provided with a double-sided ratchet, the double-sided ratchet is engaged with the connecting pipe and the third outer tube respectively, and the double-sided ratchet enables the connecting pipe and the third outer tube to move upward relative to the adjusting ring and to move downward synchronously with the adjusting ring.

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