Continuous cementing linkage concealed soluble graded cementing device

Abstract

The present invention relates to the technical field of cementing, and is a continuous cementing linkage concealed soluble graded cementing device, comprising an outer sleeve, an upper inner sleeve, a linkage sleeve, a switch sleeve, a sealing plug and a lower joint, wherein the upper inner sleeve is sleeved on the inner side of the upper part of the outer sleeve, and at least one first shear nail is distributed along the circumference between the upper part of the outer sleeve and the upper inner sleeve. The structure of the present invention is reasonable and compact, and the sealing plug is pre-installed in the outer sleeve in advance. After work, the sealing plug is lowered into the sealing assembly in the casing so that the linkage sleeve opens the liquid inlet hole after descending, and the liquid enters the liquid inlet hole so that the outer side of the lower part of the sealing plug moves to the bottom of the outer sleeve and expands. After the lower outer side of the sealing plug expands, it fits with the inner wall of the casing annulus. In this way, both ends of the sealing plug are under pressure, which can ensure the sealing effect, and can improve the sealing plug and the liquid inlet hole. Exposure can lead to the sealing plug being sealed in advance or the liquid inlet hole being opened, the liquid inlet hole and the circulation hole not being linked, and the pressure test failing.

Description

Technical Field

[0001] The invention relates to the technical field of well cementing, and is a continuous well cementing linkage concealed soluble graded cementing device. Background Art

[0002] Cementing is an important operation in the process of drilling and completion. With the gradual development of oil fields, the underground strata are becoming more and more complex. Under high pressure, the strata become very prone to leakage, which brings great difficulties and challenges to cementing operations. Conventional graded cementing technology still has many shortcomings. Drill-free graded cementing is a relatively cutting-edge cementing technology that can solve this difficulty. This technology eliminates the drilling and plugging process after cementing, shortens the project cycle, and reduces construction costs. At the same time, this technology extends the mining life of the oil well and has a significant effect on improving its comprehensive mining value.

[0003] At present, some scenarios in graded cementing require continuous cementing, but the continuous cementing cementing device currently only has a hydraulic expansion external pipe packer cementing device, which is simply composed of the existing drill-free graded cementing device and the external pipe packer connected in series. In normal construction operations, they will be restrained by pressure from each other, especially under abnormal pressure conditions, and the cementing operation cannot be completed. At the same time, when continuous graded cementing is used for cementing high-angle wells and horizontal wells, the detached materials of the drill-free graded cementing device cannot be completely detached to the bottom of the well, and need to be pushed to the bottom of the well through the well, which increases the operation process.

[0004] The Chinese patent document with the announcement number CN202850941U discloses a drilling-free staged cementing device, which includes a body and a hole-opening sleeve; an internal thread is provided at the lower end of the body, the hole sleeve is fixedly installed on the upper inner side of the body by means of a hole-closing sleeve shearing nail, a plug sleeve is fixedly installed on the upper inner side of the hole-closing sleeve by means of a plug sleeve shearing nail, a boss is fixed at the lower end of the plug sleeve, a clamping table is fixed on the lower inner side of the body, the inner diameter of the clamping table is the same as the inner diameter of the hole-closing sleeve, and the inner diameter of the clamping table is fixed on the inner side of the clamping table. The side is fixed with a hole sleeve seat by shear nails of the hole sleeve seat, and the hole sleeve includes a hole sleeve body and a hole sleeve head; the upper end of the hole sleeve body and the lower end of the hole sleeve head are fixed together, the lower outer side of the hole sleeve body and the upper inner side of the hole sleeve seat are fixed together by shear nails of the hole sleeve, and the hole sleeve head is sleeved on the inner side of the lower end of the hole closing sleeve, and a sealed cavity is formed among the main body, the hole closing sleeve, the hole sleeve head, the hole sleeve body, the hole sleeve seat and the card table, and there is at least one hole in the main body that communicates with the sealed cavity.

[0005] A Chinese patent document with publication number CN207161045U discloses a hydraulic drill-free graded cementing device, which includes: an upper joint; a graded cementing device body, which is provided with a circulation hole and the upper end is connected to the upper joint; a closing sleeve, which is arranged in the body and connected to the body through a closing shear nail; a sliding sleeve, which is arranged in the closing sleeve and connected to the closing sleeve through a slip-off shear nail; an opening sleeve, which is arranged in the body and below the closing sleeve, and is connected to the body through an opening shear nail; under the action of a first set pressure, the opening sleeve can move from a first position that closes the circulation hole to a second position that opens the circulation hole; and a closing plug, which cooperates with the closing sleeve to hold pressure, and under the action of a third set pressure, when the slip-off shear nail is sheared off, the closing plug drives the sliding sleeve to automatically fall off from the inside of the body.

[0006] The above-mentioned continuous cementing staged cementing devices all have exposed isolation rubber tubes. During the casing installation, especially in the large dog-leg section, the isolation rubber tubes are easily scratched, resulting in problems such as failure to seal and pressure test, weak positive and negative pressure bearing capacity of the isolation part, etc., leading to failure of isolation cementing.

[0007] Secondly, the fluid inlet hole is exposed, and the fluid inlet hole is not linked with the circulation hole. Abnormal circulation pressure during casing lowering and cementing will cause the packer to expand prematurely or the packer to fail to open and close, leading to downhole accidents and increasing operational risks and engineering costs. Summary of the invention

[0008] The present invention provides a continuous cementing-linked concealed soluble graded cementing device, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems of the prior graded cementing device, such as the sealing plug and the liquid inlet hole being exposed, resulting in the sealing plug being expanded and sealed in advance or the liquid inlet hole being opened, the liquid inlet hole and the circulation hole not being linked, and the pressure test failing.

[0009] The technical scheme of the present invention is realized by the following measures: a continuous cementing linkage concealed soluble graded cementing device, comprising an outer sleeve, an upper inner sleeve, a linkage sleeve, a switch sleeve, a sealing plug and a lower joint, wherein the upper inner sleeve is sleeved on the inner side of the upper part of the outer sleeve, at least one first shear nail is distributed along the circumference between the upper part of the outer sleeve and the upper inner sleeve, a linkage sleeve is sleeved on the inner side of the outer sleeve corresponding to the position below the upper inner sleeve, at least one second shear nail is distributed along the circumference between the lower part of the linkage sleeve and the outer sleeve, a circulation hole communicating inside and outside is provided on the outer side of the lower part of the outer sleeve corresponding to the position between the upper end of the linkage sleeve and the second shear nail, and a first step surface and a second step surface are provided on the inner side of the lower part of the outer sleeve corresponding to the position below the second shear nail. A sealing hole connected inside and outside is provided on the inner side of the lower part of the linkage sleeve corresponding to the position below the first step surface, a switch sleeve is fixedly installed on the inner side of the outer sleeve corresponding to the position between the first step surface and the second step surface, a liquid inlet hole is provided on the inner wall of the switch sleeve corresponding to the position between the sealing hole and the lower end of the linkage sleeve, the other end of the liquid inlet hole extends to the lower end of the switch sleeve, a stop pin is provided on the inner side of the switch sleeve corresponding to the position below the linkage sleeve, a lower joint is fixedly installed on the inner side of the lower end of the switch sleeve corresponding to the position below the stop pin, a sealing sleeve is installed on the outer side of the lower joint corresponding to the position below the second step surface, and a sealing plug is fixedly installed on the inner side of the lower part of the outer sleeve, and an annular sealing block is fixedly installed on the outer side of the lower joint corresponding to the position below the sealing plug.

[0010] The following are further optimizations and / or improvements to the above technical solutions:

[0011] At least one third shear nail may be distributed along the circumference between the upper part of the sealing plug and the lower joint, and the distance between the lower end of the sealing plug and the upper end surface of the sealing block is less than the length of the sealing plug.

[0012] A gravity plug seat can be installed in the linkage sleeve corresponding to the position below the sealing hole, at least one fourth shear pin is distributed along the circumference between the linkage sleeve and the gravity plug seat corresponding to the position above the liquid inlet hole and below the sealing hole, and at least one first sealing member is installed at upper and lower intervals between the outer side of the gravity plug seat and the inner side of the linkage sleeve corresponding to the position above and below the fourth shear pin.

[0013] A secondary rubber plug seat may be mounted on the inner side of the upper inner sleeve, at least one fifth shear pin is distributed along the circumference between the secondary rubber plug seat corresponding to the position below the first shear pin and the upper inner sleeve, and at least one second sealing member is installed at intervals up and down on the outer side of the secondary rubber plug seat corresponding to the position above and below the fifth shear pin.

[0014] The inner sides of the secondary rubber plug and the gravity plug seat can be stepped holes with larger upper part and smaller lower part. The lower inner diameter of the secondary rubber plug seat is larger than that of the gravity plug seat. At least one third sealing member is installed at intervals on the upper inner side of the gravity plug seat.

[0015] A spacing may be provided between the upper end of the above-mentioned lower joint and the lower end of the linkage sleeve. An inside-outside connecting mounting screw hole is provided on the outer side of the lower part of the outer sleeve. A radially through fixing hole is provided on the outer side of the switch sleeve corresponding to the position of the mounting screw hole. A stop pin is threaded into the mounting screw hole and the end thereof passes through the fixing hole and is located between the bottom of the linkage sleeve and the top of the upper joint.

[0016] An upper joint may be fixedly mounted on the inner side of the upper portion of the outer sleeve corresponding to the upper end of the upper inner sleeve.

[0017] At least one fourth sealing member may be provided at intervals above and below the outer side of the linkage sleeve above the corresponding circulation hole, between the circulation hole and the second shear pin, and between the second shear pin and the first step surface;

[0018] At least one fifth sealing member may be provided at intervals up and down on the outer side of the upper inner sleeve corresponding to the position above and below the first shear pin.

[0019] A spacing may be provided between the lower end of the upper inner sleeve and the upper end of the linkage sleeve.

[0020] The structure of the present invention is reasonable and compact. The sealing plug is pre-installed in the outer sleeve in advance. After work, the sealing plug is lowered into the sealing assembly in the casing so that the linkage sleeve opens the liquid inlet hole after descending. Liquid enters the liquid inlet hole so that the outer side of the lower part of the sealing plug moves to the bottom of the outer sleeve and then expands. After the lower outer side of the sealing plug expands, it fits with the inner wall of the casing annulus. In this way, both ends of the sealing plug are under pressure, which can ensure the sealing effect. The problems of the sealing plug and the liquid inlet hole being exposed, resulting in the sealing plug being expanded and sealed in advance or the liquid inlet hole being opened, the liquid inlet hole and the circulation hole not being linked, and the pressure test failing can be improved.

[0021] The present invention has the following effects:

[0022] During the casing lowering process, the sealing rubber plug is placed inside the outer casing, and the inner side of the outer casing can protect the sealing rubber plug and prevent it from being scratched;

[0023] During the first-level construction process, the internal part of the continuous cementing linkage hidden soluble graded cementing device is less affected, and the sealing plug will not be expanded in advance or the liquid inlet hole will not be opened;

[0024] The switches of the liquid inlet hole and the circulation hole are interrelated, so that the upper inner sleeve finally closes the circulation hole to ensure that the pressure test is qualified. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Attached Figure 1 It is a schematic diagram of the main cross-sectional structure of the best embodiment of the present invention.

[0026] Attached Figure 2 It is a schematic diagram of the main cross-sectional structure when the sealing hole and the liquid inlet hole are aligned in the best embodiment of the present invention.

[0027] Attached Figure 3 This is a schematic diagram of the main cross-sectional structure when the liquid inlet hole is closed and the circulation hole is opened in the best embodiment of the present invention.

[0028] Attached Figure 4 It is a schematic diagram of the main cross-sectional structure when the circulation hole is closed in the best embodiment of the present invention.

[0029] Attached Figure 5 This is a schematic diagram of the main cross-sectional structure of the best embodiment of the present invention when the work is completed.

[0030] Attached Figure 6 It is a schematic diagram of the main structure of the gravity plug in the best embodiment of the present invention.

[0031] Attached Figure 7 It is a schematic diagram of the main structure of the secondary rubber plug in the best embodiment of the present invention.

[0032] Attached Figure 8 This is a schematic diagram of the main structure of the primary rubber plug in the best embodiment of the present invention.

[0033] The codes in the accompanying drawings are: 1 is an outer sleeve, 2 is an upper inner sleeve, 3 is a linkage sleeve, 4 is a switch sleeve, 5 is a sealing plug, 6 is a lower joint, 7 is a sealing block, 8 is a first shear nail, 9 is a second shear nail, 10 is a stop pin, 11 is a circulation hole, 12 is a sealing hole, 13 is a liquid inlet hole, 14 is a first step surface, 15 is a second step surface, 16 is a third shear nail, 17 is a fourth shear nail, 18 is a fifth shear nail, 19 is a first seal, 20 is a second seal, 21 is a third seal, 22 is a fourth seal, 23 is a fifth seal, 24 is a gravity plug, 25 is a gravity plug seat, 26 is a secondary plug, 27 is a secondary plug seat, 28 is an upper joint, and 29 is a primary plug. DETAILED DESCRIPTION

[0034] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0035] In the present invention, for the convenience of description, the relative position relationship of each component is described according to the attached Figure 1 The layout is described in detail, such as the positional relationship of front, back, top, bottom, left, right, etc., which is based on the attached manual. Figure 1 It is determined by the layout direction.

[0036] The present invention will be further described below in conjunction with embodiments and drawings:

[0037] Embodiment 1: As shown in the attached Figures 1 to 5As shown in Figure 8, the continuous cementing linkage concealed soluble graded cementing device comprises an outer sleeve 1, an upper inner sleeve 2, a linkage sleeve 3, a switch sleeve 4, a sealing plug 5 and a lower joint 6. The upper inner sleeve 2 is sleeved on the inner side of the upper part of the outer sleeve 1, and at least one first shear nail 8 is distributed along the circumference between the upper part of the outer sleeve 1 and the upper inner sleeve 2. The inner side of the outer sleeve 1 corresponding to the position below the upper inner sleeve 2 is sleeved with a linkage sleeve 3, and at least one second shear nail 9 is distributed along the circumference between the lower part of the linkage sleeve 3 and the outer sleeve 1. A circulation hole 11 connected to the inside and outside is provided on the outer side of the lower part of the outer sleeve 1 corresponding to the position between the upper end of the linkage sleeve 3 and the second shear nail 9. A first step surface 14 and a second step surface 15 are provided on the inner side of the lower part of the outer sleeve 1 corresponding to the position below the second shear nail 9 from top to bottom. A sealing hole 12 which is connected inside and outside is provided on the inner side of the lower part of the linkage sleeve 3 at the square position; a switch sleeve 4 is fixedly installed on the inner side of the outer sleeve 1 at the position between the first step surface 14 and the second step surface 15; a liquid inlet hole 13 is provided on the inner wall of the switch sleeve 4 at the position between the bottom of the sealing hole 12 and the lower end of the linkage sleeve 3; the other end of the liquid inlet hole 13 extends to the lower end of the switch sleeve 4; a stop pin 10 is provided on the inner side of the switch sleeve 4 at the position below the linkage sleeve 3; a lower joint 6 is fixedly installed on the inner side of the lower end of the switch sleeve 4 at the position below the stop pin 10; a sealing plug 5 which is mounted on the inner side of the lower part of the outer sleeve 1 is installed on the outer side of the lower joint 6 at the position below the second step surface 15; and an annular sealing block 7 is fixedly installed on the outer side of the lower part of the lower joint 6 at the position below the sealing plug 5.

[0038] According to the requirements, a first shear nail 8 is installed between the upper part of the outer sleeve 1 and the upper inner sleeve 2, a second shear nail 9 is installed between the lower part of the linkage sleeve 3 and the outer sleeve 1, and the outer side of the outer sleeve 1 is provided with an upper connecting screw hole and a lower connecting screw hole that are connected to the inside and outside at intervals from top to bottom. The outer side of the upper inner sleeve 2 corresponding to the position of the upper connecting screw hole is provided with an upper connecting hole, and the outer side of the linkage sleeve 3 corresponding to the position of the lower connecting screw hole is provided with a lower connecting hole. The upper connecting screw hole is threaded with a first shear nail 8 whose end is sleeved in the upper connecting hole, and the lower connecting screw hole is threaded with a second shear nail 9 whose end is sleeved in the lower connecting hole. The sealing rubber plug 5 includes two rubber plugs symmetrically arranged up and down, and the rubber plug has an umbrella-shaped structure, which improves the sealing rubber. The pressure-bearing capacity of both ends of the plug 5, the sealing plug 5 is pre-installed into the outer sleeve 1 in advance. After work, the outer side of the lower part of the sealing plug 5 moves to the bottom of the outer sleeve 1 and then expands. Both ends of the expanded sealing plug 5 are under pressure, which can ensure the sealing effect. The lower joint 6 and the inner side of the sealing block 7 are fixed together by threaded connection. When the sealing plug 5 installed in the outer sleeve 1 moves downward, the outer side of the lower part of the sealing plug 5 is separated from the outer sleeve 1 and then expands. When the sealing plug 5 moves downward to the sealing block 7, the sealing block 7 blocks the sealing plug 5. In this way, the outer side of the lower part of the sealing plug 5 expands and fits with the outer annulus to achieve sealing. The switch sleeve 4 and the lower joint 6 can be set as a whole.

[0039] The method of using the continuous cementing linkage hidden soluble graded cementer is as follows:

[0040] S1, connect the upper part of the jacket 1 to the lower end of the pipe string and lower it into the target position;

[0041] S2, first-level construction, including:

[0042] S21, injection of first-grade cement;

[0043] S22, after inserting the first-level rubber plug 29, injecting the dissolving liquid (ensuring that the part below the circulation hole 11 is filled with the dissolving liquid);

[0044] S23, first-stage displacement, after displacement, the well bottom is hit by pressure;

[0045] S3, blocking, including:

[0046] S31, insert the first plugging component, the first plugging component seals the inner side of the linkage sleeve 3 below the sealing hole 12, the first plugging component can be an existing well-known technology, such as the first plugging component includes a plugging plug and a plug seat installed on the inner side of the lower end of the linkage sleeve 3 through shear nails, or a plugging plug and an inner ring platform tightly sleeved on the inner side of the linkage sleeve 3, when the pressure above the plugging plug is greater than the set value, the shear nails are cut off or the plugging plug and the inner ring platform tightly sleeved on the inner side of the linkage sleeve 3 can move downward relative to the linkage sleeve 3;

[0047] S32, wellhead pressure is applied to cut off the second shear pin 9;

[0048] S33, the linkage sleeve 3 moves downward, and when the lower end of the linkage sleeve 3 contacts the stop pin 10, the sealing hole 12 and the liquid inlet hole 13 are aligned and connected to each other;

[0049] S34, continue to pressurize so that the sealing rubber plug 5 tightly fitted in the outer sleeve 1 moves downward;

[0050] S35, the lower end of the sealing plug 5 contacts the upper end of the sealing block 7, and the outer side of the lower part of the sealing plug 5 expands and fits the outer annulus to achieve sealing;

[0051] S4, injection of secondary cement, including:

[0052] S41, continue to pressurize to cut off the stop pin 10, the linkage sleeve 3 and the first plugging assembly continue to move downward, the sealing hole 12 and the liquid inlet hole 13 are in a completely closed state before the first plugging assembly is put into use, and will not be affected by the casing cycle and the primary construction;

[0053] S42, when the lower end of the linkage sleeve 3 contacts the upper end of the lower joint 6, the liquid inlet hole 13 is closed and the circulation hole 11 is opened;

[0054] S43, start injecting secondary cement through the circulation hole 11;

[0055] S5, closing the graded cementer, including:

[0056] S51, inserting a second plugging component, which may have the same structure as the first plugging component, and whose outer diameter is larger than that of the first plugging component, so that the first plugging component will not get stuck in the upper inner sleeve 2 after being inserted, and then injecting a dissolving liquid;

[0057] S52, secondary displacement, when the second plugging assembly plugs the inner side of the upper inner sleeve 2, the pressure is continued to be held to cut off the first shear nail 8 between the upper inner sleeve 2 and the outer sleeve 1;

[0058] S53, the upper inner sleeve 2 moves downward and closes the circulation hole 11;

[0059] S6, stage cementer falls off, including:

[0060] S61, continue to increase the pressure in the upper end of the outer sleeve 1;

[0061] S62, by holding the pressure, the second plugging component and the first plugging component are separated from the linkage sleeve 3 and then fall down;

[0062] S63, the second plugging assembly and the first plugging assembly fall to the bottom of the well together by their own weight.

[0063] According to the continuous cementing linkage concealed soluble graded cementing device of the present invention, the isolation plug 5 is pre-installed in the outer sleeve 1 in advance. After work, the isolation plug 5 is lowered into the isolation assembly in the casing so that the linkage sleeve 3 is lowered and then the liquid inlet hole 13 is opened. Liquid enters the liquid inlet hole 13 so that the lower outer side of the isolation plug 5 moves to the bottom of the outer sleeve 1 and then expands. After the lower outer side of the isolation plug 5 expands, it fits with the inner wall of the casing annulus. In this way, both ends of the isolation plug 5 are under pressure, which can ensure the isolation effect. The problem that the isolation plug 5 and the liquid inlet hole 13 are exposed, resulting in the isolation plug 5 being expanded and sealed in advance or the liquid inlet hole 13 being opened, the liquid inlet hole 13 and the circulation hole 11 not being linked, and the pressure test failing can be improved.

[0064] The present invention has the following effects:

[0065] During the casing lowering process, the sealing rubber plug 5 is sleeved on the inner side of the outer sleeve 1, and the inner side of the outer sleeve 1 can protect the sealing rubber plug 5 and prevent the sealing rubber plug 5 from being scratched;

[0066] During the first-level construction process, the internal part of the continuous cementing linkage hidden soluble graded cementing device is slightly affected, and the sealing plug 5 will not be expanded and sealed in advance or the liquid inlet hole 13 will not be opened;

[0067] The opening and closing of the liquid inlet hole 13 and the circulation hole 11 are interrelated, so that the upper inner sleeve 2 finally closes the circulation hole 11 to ensure that the pressure test is qualified.

[0068] According to actual needs, the above-mentioned continuous cementing linkage concealed soluble graded cementing device can be further optimized and / or improved:

[0069] Embodiment 2: As an optimization of the above embodiment, as shown in the attached Figures 1 to 5 As shown, at least one third shear nail 16 is distributed along the circumference between the upper part of the sealing plug 5 and the lower joint 6 , and the distance between the lower end of the sealing plug 5 and the upper end surface of the sealing block 7 is less than the length of the sealing plug 5 .

[0070] According to the requirements, a third shear pin 16 is provided between the upper part of the sealing plug 5 and the lower joint 6, that is, a threaded through hole communicating with the inside and outside is provided on the outer side of the upper part of the sealing plug 5, and a limiting groove is provided on the outer side of the upper part of the lower joint 6 corresponding to the position of the threaded through hole, and a third shear pin 16 with its end inserted into the limiting groove is threadedly connected in the threaded through hole.

[0071] During use, with such an arrangement, the wellhead is pressurized to cut off the second shear nail 9, and the linkage sleeve 3 and the gravity plug seat 25 move downward. When the lower end of the linkage sleeve 3 contacts with the stop pin 10, the sealing hole 12 and the liquid inlet hole 13 are aligned and connected to each other, and the pressure is continued until the third shear nail 16 is cut off, so that the sealing plug 5 hidden in the outer sleeve 1 moves downward, and the lower end of the sealing plug 5 moves downward to the sealing block 7, and the outer side of the lower part of the sealing plug 5 expands and fits with the outer annulus to achieve sealing. The distance between the lower end of the sealing plug 5 and the upper end face of the sealing block 7 is less than the length of the sealing plug 5. In this way, when the lower end of the sealing plug 5 contacts with the upper end of the sealing block 7, the upper part of the sealing plug 5 is still sheathed in the outer sleeve 1, and the outer side of the lower part of the sealing plug 5 under the outer sleeve 1 expands and fits with the outer annulus. In this way, both ends of the sealing plug 5 are under pressure, which can ensure the sealing effect, thereby achieving sealing and facilitating the secondary cementing operation.

[0072] Embodiment 3: As an optimization of the above embodiment, as shown in the attached Figures 1 to 6 As shown, a gravity plug seat 25 is installed in the linkage sleeve 3 corresponding to the position below the sealing hole 12, at least one fourth shear pin 17 is distributed along the circumference between the linkage sleeve 3 and the gravity plug seat 25 at a position between the top of the liquid inlet hole 13 and the bottom of the sealing hole 12, and at least one first sealing member 19 is installed at upper and lower intervals between the outer side of the gravity plug seat 25 and the inner side of the linkage sleeve 3 at positions above and below the fourth shear pin 17.

[0073] According to the requirements, a fourth shear nail 17 is installed between the linkage sleeve 3 and the gravity plug seat 25 at the position between the top of the liquid inlet hole 13 and the bottom of the sealing hole 12, that is, a radially through threaded hole is provided on the outer side of the lower part of the linkage sleeve 3, and a blind hole is provided on the outer side of the upper part of the secondary plug seat 27 corresponding to the position of the threaded hole, and the fourth shear nail 17 with the end portion sleeved in the blind hole is threaded in the threaded hole, and the first sealing member 19 is an existing well-known sealing ring.

[0074] During use, through such a setting, the circulation hole 11 is closed after the upper inner sleeve 2 descends, and the pressure in the upper end of the outer sleeve 1 is continuously increased. By holding the pressure, the fifth shear nail 18 between the secondary rubber plug seat 27 and the upper inner sleeve 2 is sheared, and the fourth shear nail 17 between the gravity plug seat 25 and the linkage sleeve 3 is sheared, so that the gravity plug 24 and the gravity plug seat 25 fall to the bottom of the well together by their own weight. The material of the gravity plug 24 and the gravity plug seat 25 can be a known soluble material, such as aluminum magnesium. Alloy, or the soluble material unit recorded in the soluble fracturing displacement sand flushing tool and fracturing method disclosed in the Chinese patent document with publication number CN112012707A, the soluble material unit has a pressure resistance of 80MPa and a temperature resistance of 50-120°C. It can be completely dissolved after being immersed in 90°C fracturing fluid for 15 days, and the dissolved residue is a granular or flocculent solid phase. In this way, the gravity plug 24 and the gravity plug seat 25 are immersed in the dissolving liquid, and after dissolution, there is no blockage in the cement injector.

[0075] Embodiment 4: As an optimization of the above embodiment, as shown in the attached Figures 1 to 7 As shown, a secondary rubber plug seat 27 is sleeved on the inner side of the upper inner sleeve 2, and at least one fifth shear pin 18 is distributed along the circumference between the secondary rubber plug seat 27 corresponding to the position below the first shear pin 8 and the upper inner sleeve 2, and at least one second sealing member 20 is installed at intervals up and down on the outer side of the secondary rubber plug seat 27 corresponding to the position above and below the fifth shear pin 18.

[0076] According to the needs, a fifth shear pin 18 is provided between the secondary rubber plug seat 27 corresponding to the position below the first shear pin 8 and the upper inner sleeve 2, a screw hole communicating inside and outside is provided on the outer side of the lower part of the upper inner sleeve 2, a card groove is provided on the outer side of the secondary rubber plug seat 27 corresponding to the position of the screw hole, and the fifth shear pin 18 with the end portion sleeved in the card groove is threadedly connected in the screw hole, and the second sealing member 20 is an existing well-known sealing ring.

[0077] During use, by such a setting, the secondary rubber plug 26 is thrown and the dissolving liquid is injected. When the secondary rubber plug 26 descends to the secondary rubber plug seat 27, the pressure is continued to be held, and the first shear nail 8 between the upper inner sleeve 2 and the outer sleeve 1 can be quickly and smoothly sheared. In this way, the circulation hole 11 is closed after the upper inner sleeve 2 descends, and then the pressure in the upper end of the outer sleeve 1 is continued to be increased, and the fourth shear nail 17 between the gravity plug seat 25 and the linkage sleeve 3 is sheared by holding the pressure. In this way, the gravity plug 24, the gravity plug seat 25, the secondary rubber plug 26, and the secondary rubber plug seat 27 fall to the bottom of the well together by their own weight, and the gravity plug 24, the gravity plug seat 25, the secondary rubber plug 26, and the secondary rubber plug seat 27 fall to the bottom of the well together by their own weight. The materials of the rubber plug 26 and the secondary rubber plug seat 27 are all existing well-known soluble materials, such as aluminum-magnesium alloy or the soluble material unit recorded in the soluble fracturing displacement sand flushing tool and fracturing method disclosed in the Chinese patent document with publication number CN112012707A. The soluble material unit has a pressure resistance of 80MPa and a temperature resistance of 50-120°C. It can be completely dissolved after being immersed in 90°C fracturing fluid for 15 days. The dissolved residue is a granular or flocculent solid phase. In this way, the gravity plug 24, the gravity plug seat 25, the secondary rubber plug 26, and the secondary rubber plug seat 27 are immersed in the dissolving liquid, and after dissolution, there is no blockage in the cement injector.

[0078] Embodiment 5: As an optimization of the above embodiment, as shown in the attached Figures 1 to 8 As shown, the inner side of the secondary rubber plug 26 and the inner side of the gravity plug seat 25 are both stepped holes with a larger upper part and a smaller lower part. The lower inner diameter of the secondary rubber plug seat 27 is larger than the lower inner diameter of the gravity plug seat 25. At least one third sealing member 21 is installed at intervals on the upper inner side of the gravity plug seat 25.

[0079] According to the requirements, the inner side of the secondary rubber plug 26 and the gravity plug seat 25 are both existing well-known technologies, and the third sealing member 21 is an existing well-known sealing ring. During use, the first-level cement is injected, and after the first-level rubber plug 29 is thrown, the dissolving liquid is injected, and the first-level displacement is replaced. After displacement, it hits the bottom of the well and the first-level construction is completed.

[0080] First, a gravity plug 24 with a smaller outer diameter is thrown in, and the gravity plug 24 moves down to the gravity plug seat 25. After the gravity plug 24 blocks the gravity plug seat 25, pressure is applied at the wellhead to shear off the second shear nail 9. The linkage sleeve 3 and the gravity plug seat 25 move down. When the lower end of the linkage sleeve 3 contacts the stopper pin 10, the sealing hole 12 and the liquid inlet hole 13 are aligned and connected to each other. Pressure is continued until the third shear nail 16 is sheared off, so that the sealing rubber plug 5 hidden in the outer sleeve 1 moves down and moves down to the sealing block 7. The sealing rubber plug 5 expands and fits the outer annulus to achieve sealing.

[0081] Continue to press to cut off the stop pin 10, the linkage sleeve 3 and the gravity plug seat 25 move downward, the liquid inlet hole 13 is closed, and at the same time, continue to press to complete the opening of the graded cementing device to achieve linkage (that is, the linkage sleeve 3 and the gravity plug seat 25 move downward, the liquid inlet hole 13 is closed when the lower end of the linkage sleeve 3 contacts the upper end of the lower joint 6, and the circulation hole 11 is opened at the same time), and the secondary cement can be injected through the circulation hole 11, and then the secondary rubber plug 26 with a larger outer diameter is thrown to block the upper inner sleeve 2, so that the upper inner sleeve 2 can move downward and block the circulation hole 11 after the first shear nail 8 is cut off, so that the cementing operation can be carried out in sequence, thereby improving the success rate of the cementing operation.

[0082] Continue to increase the pressure in the upper end of the outer sleeve 1, and by holding the pressure, the fifth shear nail 18 between the secondary rubber plug seat 27 and the upper inner sleeve 2 is sheared, and the fourth shear nail 17 between the gravity plug seat 25 and the linkage sleeve 3 is sheared, and the gravity plug 24, the gravity plug seat 25, the secondary rubber plug 26, and the secondary rubber plug seat 27 fall to the bottom of the well together by their own weight, and the gravity plug 24, the gravity plug seat 25, the secondary rubber plug 26, and the secondary rubber plug seat 27 are immersed in the dissolving liquid, and after dissolution, there is no blockage in the cementing device.

[0083] Embodiment 6: As an optimization of the above embodiment, as shown in the attached Figures 1 to 5 As shown, there is a spacing between the upper end of the lower joint 6 and the lower end of the linkage sleeve 3, a mounting screw hole communicating inside and outside is provided on the outer side of the lower part of the outer sleeve 1, a radially through fixing hole is provided on the outer side of the switch sleeve 4 corresponding to the position of the mounting screw hole, and a stop pin 10 is threaded in the mounting screw hole, the end of which passes through the fixing hole and is located between the bottom of the linkage sleeve 3 and the top of the upper joint 28.

[0084] During use, through such an arrangement, the stop pin 10 can be installed according to the spacing between the sealing hole 12 and the liquid inlet hole 13. When the lower end of the linkage sleeve 3 is in contact with the head of the stop pin 10, the sealing hole 12 and the liquid inlet hole 13 can be connected. When the second shear nail 9 is cut off, the linkage sleeve 3 moves downward. When the lower end of the linkage sleeve 3 moves to contact with the head of the stop pin 10, the projection of the sealing hole 12 in the vertical plane is partially or completely located within the projection of the liquid inlet hole 13 in the vertical plane. In this embodiment, when the lower end of the linkage sleeve 3 moves to contact with the head of the stop pin 10, When touched, the projection of the sealing hole 12 in the vertical plane coincides with the projection of the liquid inlet hole 13 in the vertical plane, and pressure is continued until the third shear nail 16 is cut off, so that the sealing plug 5 hidden in the outer sleeve 1 moves downward, and the lower end of the sealing plug 5 moves downward to the sealing block 7, and the sealing plug 5 expands and fits the outer annulus to achieve sealing, and pressure is continued to shear off the stop pin 10, and the linkage sleeve 3 and the gravity plug seat 25 move downward. When the lower end of the linkage sleeve 3 contacts the upper end of the lower joint 6, the liquid inlet hole 13 is closed, and the circulation hole 11 is opened at the same time, and the secondary cement can be injected through the circulation hole 11, thereby improving the continuity of the cement injection operation.

[0085] Embodiment 7: As an optimization of the above embodiment, as shown in the attached Figures 1 to 5As shown, an upper joint 28 is fixedly installed on the inner side of the upper portion of the outer sleeve 1 corresponding to the upper end position of the upper inner sleeve 2.

[0086] During use, an upper joint 28 is provided to facilitate assembly and disassembly between the outer sleeve 1 and the pipe column. According to requirements, the upper joint 28 and the outer sleeve 1 are fixedly installed together by threaded connection.

[0087] Embodiment 8: As an optimization of the above embodiment, as shown in the attached Figures 1 to 5 As shown, at least one fourth sealing member 22 is provided at intervals above and below the outer side of the linkage sleeve 3 corresponding to the position above the circulation hole 11, between the bottom of the circulation hole 11 and the top of the second shear pin 9, and between the bottom of the second shear pin 9 and the first step surface 14.

[0088] According to the requirements, the fourth sealing member 22 is a well-known sealing ring. During use, the fourth sealing member 22 arranged on the outer side of the linkage sleeve 3 above the circulation hole 11 and between the lower side of the circulation hole 11 and the upper side of the second shear pin 9 can improve the sealing performance of the linkage sleeve 3 to the circulation hole 11, and the fourth sealing member 22 on the outer side of the linkage sleeve 3 between the lower side of the circulation hole 11 and the upper side of the second shear pin 9 and between the lower side of the second shear pin 9 and the first step surface 14 can improve the sealing performance above and below the second shear pin 9, so as to facilitate the rapid shearing of the second shear pin 9 when the pressure is increased.

[0089] Embodiment 9: As an optimization of the above embodiment, as shown in the attached Figures 1 to 7 As shown, at least one fifth sealing member 23 is provided at intervals up and down on the outer side of the upper inner sleeve 2 corresponding to the position above the first shear pin 8 and below the fifth shear pin 18 .

[0090] According to the requirements, two fifth seals 23 are provided at intervals between the outer side of the upper inner sleeve 2 and the inner side of the upper part of the outer sleeve 1 at the upper and lower positions corresponding to the first shear nail 8. The fifth seal 23 is a known sealing ring. During use, by providing the fifth seal 23, the sealing between the inner side of the upper part and the lower part of the upper inner sleeve 2 and the inner side of the outer sleeve 1 can be ensured, so that the circulation hole 11 is opened after the linkage sleeve 3 moves downward. When the circulation hole 11 needs to be closed again, the secondary rubber plug 26 is thrown and the dissolving liquid is injected. When the secondary rubber plug 26 descends to the secondary rubber plug seat 27, the pressure is continued to be held, and the first shear nail 8 between the upper inner sleeve 2 and the outer sleeve 1 can be quickly and smoothly cut off. In this way, the circulation hole 11 is closed after the upper inner sleeve 2 descends, so that the subsequent cementing operation can be carried out smoothly.

[0091] Embodiment 10: As an optimization of the above embodiment, as shown in the attached Figures 1 to 8 As shown, a distance is provided between the lower end of the upper inner sleeve 2 and the upper end of the linkage sleeve 3.

[0092] During use, through such an arrangement, after the secondary rubber plug 26 is inserted into the upper inner sleeve 2, the pressure in the pipe string can all act on the first shear nail 8, so that the first shear nail 8 can be quickly sheared off, ensuring the continuous cementing.

[0093] During use, the method of using the continuous cementing linkage hidden soluble graded cementing device is as follows:

[0094] S1, connect the upper part of the upper joint 28 to the lower end of the pipe string and lower it into the target position;

[0095] S2, first-level construction, including:

[0096] S21, injection of first-grade cement;

[0097] S22, after inserting the first-level rubber plug 29, injecting the dissolving liquid (ensuring that the part below the circulation hole 11 is filled with the dissolving liquid);

[0098] S23, first-stage displacement, after displacement, the well bottom is hit by pressure;

[0099] S3, blocking, including:

[0100] S31, throwing the gravity plug 24, the gravity plug 24 descends to the gravity plug seat 25 and blocks the inner side of the gravity plug seat 25;

[0101] S32, wellhead pressure is applied (by setting the pressure gradient to work in stages, such as the shearing pressure of the second shear nail 9 is 2MPa, the shearing pressure of the third shear nail 16 is 3MPa, the shearing pressure of the stop pin 10 is 4MPa, and the shearing pressure of the first shear nail 8 is 8MPa, to ensure the smooth construction sequence) to shear the second shear nail 9;

[0102] S33, the linkage sleeve 3 and the gravity plug seat 25 move downward, and when the lower end of the linkage sleeve 3 contacts the stopper pin 10, the sealing hole 12 and the liquid inlet hole 13 are aligned and connected to each other.

[0103] S34, continue pressing until the third shear pin 16 is cut off, so that the sealing rubber plug 5 hidden in the outer sleeve 1 moves downward;

[0104] S35, the sealing plug 5 moves downward to the sealing block 7, and the outer side of the lower part of the sealing plug 5 expands and fits with the outer annulus to achieve sealing;

[0105] S4, injection of secondary cement, including:

[0106] S41, continue pressing to cut off the stop pin 10, and the linkage sleeve 3 and the gravity plug seat 25 move downward;

[0107] S42, when the lower end of the linkage sleeve 3 contacts the upper end of the lower joint 6, the liquid inlet hole 13 is closed and the circulation hole 11 is opened;

[0108] S43, start injecting secondary cement through the circulation hole 11;

[0109] S5, closing the graded cementer, including:

[0110] S51, insert the secondary rubber plug 26 and inject the dissolving liquid;

[0111] S52, secondary displacement, when the secondary rubber plug 26 moves downward to the secondary rubber plug seat 27 to block the inner side of the secondary rubber plug seat 27, the pressure is continued to be held to cut off the first shear nail 8 between the upper inner sleeve 2 and the outer sleeve 1;

[0112] S53, the upper inner sleeve 2 moves downward and closes the circulation hole 11;

[0113] S6, stage cementing device falls off, including:

[0114] S61, continue to increase the pressure in the upper end of the outer sleeve 1;

[0115] S62, by holding the pressure, the fifth shear nail 18 between the secondary rubber plug seat 27 and the upper inner sleeve 2 is sheared, and the fourth shear nail 17 between the gravity plug seat 25 and the linkage sleeve 3 is sheared;

[0116] S63, the gravity plug 24, the gravity plug seat 25, the secondary rubber plug 26 and the secondary rubber plug seat 27 fall to the bottom of the well together by their own weight;

[0117] S64, the gravity plug 24, the gravity plug seat 25, the secondary rubber plug 26 and the secondary rubber plug seat 27 are immersed in the dissolving liquid, and after being dissolved, there is no blockage in the cementing device.

[0118] The above technical features respectively constitute various embodiments of the present invention, which have strong adaptability and optimal implementation effects. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

[0119] The use process of the best embodiment of the present invention:

[0120] Inject first-level cement, throw in first-level rubber plug 29, first-level displacement, after displacement, the well bottom is hit by pressure, and the first-level construction is completed;

[0121] The gravity plug 24 is thrown in, and the gravity plug 24 moves down to the gravity plug seat 25 to seal the inner side of the gravity plug seat 25. The wellhead is pressurized to cut off the second shear nail 9, and the linkage sleeve 3 moves down to the stop pin 10, so that the sealing hole 12 is aligned and connected with the liquid inlet hole 13. The pressure is continued until the third shear nail 16 is cut off, so that the sealing rubber plug 5 hidden in the outer sleeve 1 moves down, and the lower end of the sealing rubber plug 5 moves down to the upper end of the sealing block 7. After the outer side of the lower part of the sealing rubber plug 5 expands, it fits with the outer annulus to achieve sealing;

[0122] Continue to press until the stop pin 10 is cut off, the linkage sleeve 3 and the gravity plug seat 25 continue to move downward, the liquid inlet hole 13 is closed by the linkage sleeve 3, and the circulation hole 11 is opened at the same time, and the secondary cement is injected through the circulation hole 11;

[0123] The secondary rubber plug 26 is inserted to replace the secondary rubber plug. When the secondary rubber plug 26 descends into the secondary rubber plug seat 27 and seals the secondary rubber plug seat 27, the pressure is continued to be held, and the first shear nail 8 between the upper inner sleeve 2 and the outer sleeve 1 is cut off. The upper inner sleeve 2 and the secondary rubber plug seat 27 descend, and the upper inner sleeve 2 closes the circulation hole 11 again, completing the graded cementing closure;

[0124] Then, the pressure in the upper end of the outer sleeve 1 is further increased, and the fifth shear nail 18 between the secondary rubber plug seat 27 and the upper inner sleeve 2 and the fourth shear nail 17 between the gravity plug seat 25 and the linkage sleeve 3 are sheared by holding the pressure, so that the gravity plug 24, the gravity plug seat 25, the secondary rubber plug 26, and the secondary rubber plug seat 27 fall to the bottom of the well together by their own weight, and the step cementing device is detached;

[0125] The gravity plug 24, the gravity plug seat 25, the secondary rubber plug 26 and the secondary rubber plug seat 27 are immersed in the dissolving liquid, and after being dissolved, there is no blockage in the cementing device.

Claims

1. A continuous cementing linkage concealed soluble graded cementing device, characterized in that The invention comprises an outer sleeve, an upper inner sleeve, a linkage sleeve, a switch sleeve, a sealing plug and a lower joint. The upper inner sleeve is sleeved on the inner side of the upper part of the outer sleeve. At least one first shear nail is distributed along the circumference between the upper part of the outer sleeve and the upper inner sleeve. The inner side of the outer sleeve corresponding to the position below the upper inner sleeve is sleeved with a linkage sleeve. At least one second shear nail is distributed along the circumference between the lower part of the linkage sleeve and the outer sleeve. A circulation hole communicating with the inside and outside is provided on the outer side of the lower part of the outer sleeve corresponding to the position between the upper end of the linkage sleeve and the second shear nail. A first step surface and a second step surface are provided from top to bottom on the inner side of the lower part of the outer sleeve corresponding to the position below the second shear nail. The lower inner side of the linkage sleeve corresponding to the position below the first step surface is provided with a first step surface and a second step surface. A sealing hole communicating with the inside and outside is provided on the side, a switch sleeve is fixedly installed on the inner side of the outer sleeve corresponding to the position between the first step surface and the second step surface, a liquid inlet hole is provided on the inner wall of the switch sleeve corresponding to the position between the bottom of the sealing hole and the lower end of the linkage sleeve, the other end of the liquid inlet hole extends to the lower end of the switch sleeve, a stop pin is provided on the inner side of the switch sleeve corresponding to the position below the linkage sleeve, a lower joint is fixedly installed on the inner side of the lower end of the switch sleeve corresponding to the position below the stop pin, a sealing sleeve is installed on the outer side of the lower joint corresponding to the position below the second step surface, and a sealing plug is fixedly installed on the inner side of the lower part of the outer sleeve, and an annular sealing block is fixedly installed on the outer side of the lower part of the lower joint corresponding to the position below the sealing plug.

2. The continuous cementing linkage concealed soluble graded cementing device according to claim 1 is characterized in that At least one third shear nail is distributed at intervals along the circumference between the upper part of the sealing rubber plug and the lower joint, and the distance between the lower end of the sealing rubber plug and the upper end surface of the sealing block is less than the length of the sealing rubber plug.

3. The continuous cementing linkage concealed soluble graded cementing device according to claim 1 or 2, characterized in that A gravity plug seat is installed in the linkage sleeve corresponding to the position below the sealing hole, at least one fourth shear pin is distributed along the circumference between the linkage sleeve and the gravity plug seat corresponding to the position above the liquid inlet hole and below the sealing hole, and at least one first sealing member is installed at upper and lower intervals between the outer side of the gravity plug seat and the inner side of the linkage sleeve corresponding to the position above and below the fourth shear pin.

4. The continuous cementing linkage concealed soluble graded cementing device according to claim 3 is characterized in that A secondary rubber plug seat is mounted on the inner side of the upper inner sleeve, and at least one fifth shear pin is distributed along the circumference between the secondary rubber plug seat below the first shear pin and the upper inner sleeve, and at least one second sealing member is installed at intervals on the outer side of the secondary rubber plug seat above and below the fifth shear pin.

5. The continuous cementing linkage concealed soluble graded cementing device according to claim 4 is characterized in that The inner sides of the secondary rubber plug and the gravity plug seat are both stepped holes with larger upper part and smaller lower part. The lower inner diameter of the secondary rubber plug seat is larger than that of the gravity plug seat. At least one third sealing member is installed at intervals on the upper inner side of the gravity plug seat.

6. The continuous cementing linkage concealed soluble graded cementing device according to claim 1, 2, 4 or 5, characterized in that There is a spacing between the upper end of the lower joint and the lower end of the linkage sleeve, and a mounting screw hole communicating with the inside and outside is provided on the outer side of the lower part of the outer sleeve. A radially penetrating fixing hole is provided on the outer side of the switch sleeve corresponding to the position of the mounting screw hole, and a stop pin is screwed in the mounting screw hole, and the end of the stop pin passes through the fixing hole and is located between the lower part of the linkage sleeve and the upper part of the upper joint; Or / and, an upper joint is fixedly installed on the inner side of the upper part of the outer sleeve corresponding to the upper end position of the upper inner sleeve.

7. The continuous cementing linkage concealed soluble graded cementing device according to claim 3 is characterized in that There is a spacing between the upper end of the lower joint and the lower end of the linkage sleeve, and a mounting screw hole communicating with the inside and outside is provided on the outer side of the lower part of the outer sleeve. A radially penetrating fixing hole is provided on the outer side of the switch sleeve corresponding to the position of the mounting screw hole, and a stop pin is screwed in the mounting screw hole, and the end of the stop pin passes through the fixing hole and is located between the lower part of the linkage sleeve and the upper part of the upper joint; Or / and, an upper joint is fixedly installed on the inner side of the upper part of the outer sleeve corresponding to the upper end position of the upper inner sleeve.

8. The continuous cementing linkage concealed soluble graded cementing device according to claim 1, 2, 4, 5 or 7, characterized in that At least one fourth sealing member is provided at intervals above and below the outer side of the linkage sleeve corresponding to the position above the circulation hole, between the position below the circulation hole and the position above the second shear pin, and between the position below the second shear pin and the first step surface; Or / and, at least one fifth sealing member is provided on the outer side of the upper inner sleeve at intervals above and below the first shear pin and below the fifth shear pin; Or / and, a spacing is provided between the lower end of the upper inner sleeve and the upper end of the linkage sleeve.

9. The continuous cementing linkage concealed soluble graded cementing device according to claim 3 is characterized in that At least one fourth sealing member is provided at intervals above and below the outer side of the linkage sleeve corresponding to the position above the circulation hole, between the position below the circulation hole and the position above the second shear pin, and between the position below the second shear pin and the first step surface; Or / and, at least one fifth sealing member is provided on the outer side of the upper inner sleeve corresponding to the position above the first shear pin and below the fifth shear pin at intervals from top to bottom; Or / and, a spacing is provided between the lower end of the upper inner sleeve and the upper end of the linkage sleeve.

10. The continuous cementing linkage concealed soluble graded cementing device according to claim 6, characterized in that At least one fourth sealing member is provided at intervals above and below the outer side of the linkage sleeve corresponding to the position above the circulation hole, between the position below the circulation hole and the position above the second shear pin, and between the position below the second shear pin and the first step surface; Or / and, at least one fifth sealing member is provided on the outer side of the upper inner sleeve at intervals above and below the first shear pin and below the fifth shear pin; Or / and, a spacing is provided between the lower end of the upper inner sleeve and the upper end of the linkage sleeve.

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