Pressure-maintaining coring tool

Abstract

The invention relates to the technical field of underground coring tools, in particular to a pressure maintaining coring tool which comprises an upper connector, a flow dividing inner barrel, a centralizer, an outer barrel, a lower connector, a coring drill bit, a built-in high-strength suspension assembly, a pressure grading differential assembly, a pressure compensation assembly and a ball valve type core cutting sealing assembly. The upper connector, the centralizer, the outer barrel, the lower connector and the coring drill bit are sequentially and fixedly installed together from top to bottom. The pipe joint is reasonable and compact in structure and convenient to use, the sealing performance in the pipe joint is guaranteed by arranging the sealing column, and liquid in a to-be-measured pipeline is prevented from overflowing from the upper end of the pipe joint; the sealing column adopts the split design of the front sealing body and the rear sealing body, so that the measuring probe is inserted between the front sealing body and the rear sealing body and then penetrates out of the lower end of the pipe joint to complete measurement, and the sealing column has the characteristics of stability, reliability and rapidness.

Description

Technical Field

[0001] The present invention relates to the technical field of downhole coring tools, and is a pressure-retaining coring tool. Background Technique

[0002] To ensure the country's energy strategic needs, PetroChina has increased the exploration and development of oil and gas, especially the development of natural gas resources, including the development of unconventional gas reservoirs. To accurately evaluate the oil and gas resource volume, especially the saturation of reservoir fluids such as coalbed methane (shale gas) and deep gas reservoirs, including important parameters such as methane content, it is necessary to minimize the loss of combustible gas components in the core during the drilling coring process, as it is related to many key development decisions such as gas well productivity prediction, selection of development target areas, and well pattern layout. In particular, the coal reservoir itself has low strength, has the characteristics of a dual-porosity structure, resulting in strong heterogeneity of the coal body structure and anisotropy of reservoir physical properties, as well as obvious stress sensitivity. Also, since coalbed methane is prone to decomposition and dissipation, there are great technical difficulties in pressure-retaining coring of deep coalbed methane.

[0003] Traditional pressure-retaining coring tools directly extract the core under the formation. However, the temperature of the core under the formation is relatively high. As the core is extracted, affected by the bottom-hole environment, the temperature of the core in the inner barrel gradually decreases. The temperature drop leads to a large amount of dissipation of oil and gas components in the core, which will cause certain deviations in the subsequent analysis results of the core by people and reduce the accuracy of the core analysis results.

[0004] A Chinese patent document with the publication number CN105927175B discloses a locking claw suspension type pressurized coring device, which is characterized by comprising an upper sub, a bearing seat, an outer barrel, a drill bit, a sleeve, a flow dividing joint, a locking claw sleeve, locking claws, a guiding sleeve, a limit sleeve, a pressure-bearing joint, an inner barrel and core claws; an inner ring groove for installing a retaining ring is arranged on the lower inner wall of the upper sub, an upper installation ring groove is arranged on the upper inner wall of the bearing seat, a lower installation ring groove is arranged on the lower outer wall of the bearing seat, the lower outer wall of the upper sub is fixedly installed with the upper installation ring groove, the lower installation ring groove is fixedly installed with the upper inner wall of the outer barrel, and the lower outer wall of the outer barrel is fixedly installed with the upper inner wall of the drill bit; a connecting ring platform is fixedly arranged on the upper outer wall of the sleeve, and the outer wall of the connecting ring platform is fixedly installed with the upper inner wall of the upper sub; at least one circulation hole is radially distributed along the circumference in the middle of the flow dividing joint, a bearing ring platform is fixedly arranged on the outer wall of the flow dividing joint above the circulation hole, a bearing ring groove is arranged on the inner wall of the bearing seat below the upper installation ring groove, the flow dividing joint is located in an annular cavity formed by the lower part of the upper sub, the bearing seat and the upper part of the outer barrel, a thrust bearing is arranged between the outer wall of the flow dividing joint above the bearing ring platform and the bearing ring groove, a retaining ring installation outer ring groove corresponding to the retaining ring installation inner ring groove is arranged on the outer wall of the flow dividing joint above the thrust bearing, and an elastic retaining ring is arranged in the retaining ring installation inner ring groove and the retaining ring installation outer ring groove; the lower inner wall of the flow dividing joint is fixedly installed with the upper outer wall of the locking claw sleeve, at least two locking claw installation long grooves are evenly distributed along the circumference on the lower outer wall of the locking claw sleeve, and claw head installation holes are arranged on the locking claw sleeve corresponding to the upper parts of the locking claw installation long grooves; the locking claws comprise locking claw bodies, locking claw pieces corresponding to the locking claw installation long grooves are fixedly arranged along the circumference on the upper end surfaces of the locking claw bodies, claw heads are fixedly arranged at the upper ends of the inner parts of the locking claw pieces, at least two axial locking claw long grooves are evenly arranged at the lower parts of the locking claw bodies, each locking claw piece is located in the corresponding locking claw installation long groove, and the claw head is placed in the corresponding claw head installation hole; a pressure relief sleeve is fixedly installed on the upper inner wall of the sleeve through a pressure relief pin, at least one pressure relief hole is radially distributed along the circumference on the sleeve corresponding to the pressure relief sleeve below the connecting ring platform, the upper part of the pressure application sleeve is located in the sleeve and is fixedly installed with the sleeve through a sleeve pin, at least one circulation hole channel is radially distributed along the circumference on the pressure application sleeve below the sleeve, and the lower part of the pressure application sleeve is located in a cavity formed by the flow dividing joint and the upper part of the locking claw sleeve;The guiding sleeve is located within the cavity formed by the locking jaw sleeve and the locking jaw. A boss corresponding to the long slot of the locking jaw is fixed on the outer wall of the lower end of the guiding sleeve. The boss is located within the corresponding long slot of the locking jaw and the outer end of the boss is located outside the long slot of the locking jaw. A pressure sleeve is sleeved on the locking jaw. The upper end of the pressure sleeve is fixedly installed together with the locking jaw sleeve through a pressure sleeve pin. A pressure sleeve limiting groove corresponding to the boss is provided on the inner wall of the lower end of the pressure sleeve. A limiting groove corresponding to the boss is provided at the upper end of the limiting sleeve. The outer wall of the lower end of the pressure sleeve is fixedly installed together with the inner wall of the limiting groove. The pressure sleeve limiting groove and the limiting groove form a boss limiting groove. The boss located outside the long slot of the locking jaw is located within the boss limiting groove. The outer wall of the lower end of the locking jaw body is fixedly installed together with the inner wall of the upper end of the pressure-bearing joint. A ball seat is fixedly installed on the inner wall of the lower part of the pressure-bearing joint. The outer wall of the lower part of the pressure-bearing joint is fixedly installed together with the inner wall of the upper end of the inner cylinder. An outer ring platform is provided on the outer wall of the pressure-bearing joint above the inner cylinder; a guiding platform with a wider upper part and a narrower lower part is provided on the inner wall of the lower part of the drill bit. The outer wall of the lower end of the inner cylinder is fixedly installed together with the inner wall of the upper part of the core catcher. The claw head of the core catcher is located on the guiding platform. An axial drilling fluid circulation hole is provided on the drill bit corresponding to the guiding platform. After years of implementation and use, when this locking jaw suspension type pressurized coring device is applied to coal reservoirs, due to the easy decomposition and dissipation of coalbed methane itself, the construction operation of pressure-maintaining coring for deep coalbed methane cannot be achieved.;

[0005] A Chinese patent document with the publication number CN115142804B discloses a pressure-holding coring tool, characterized in that the pressure-holding coring tool comprises a differential assembly, a temperature control assembly, a ball valve sealing assembly, a drill bit, an adapter joint and an outer barrel, wherein: The differential assembly includes a differential mandrel and a differential connecting barrel. The temperature control assembly includes a turbo generator, an inner barrel, a first adapter sleeve, a heating resistance wire, a heat insulation connecting barrel, a second adapter sleeve, a sliding connecting barrel, a clamp seat and a heat insulation valve body device. The ball valve sealing assembly includes a first ball valve connecting barrel, a second ball valve connecting barrel and a ball valve. The drill bit is fixedly connected to the lower end of the outer barrel. The adapter joint connects the differential mandrel and the outer barrel respectively. The outer barrel is arranged outside the differential assembly, the temperature control assembly, the ball valve sealing assembly and the adapter joint, and the ball valve sealing assembly is fixedly connected to the outer barrel. A first through hole is arranged at the top of the differential connecting barrel, a second through hole is arranged on the central axis of the differential mandrel, the lower end of the second through hole is frustum-shaped. The differential mandrel includes an upper shaft section and a lower shaft section. The outer diameter of the lower shaft section is larger than that of the upper shaft section. The outer wall of the lower shaft section is matched with the inner wall of the differential connecting barrel. The outer wall of the upper shaft section is matched with the first through hole. A third through hole communicating with the second through hole is arranged on the outer wall of the lower shaft section. A groove communicating the third through hole and the top surface of the lower shaft section is arranged on the outer wall of the lower shaft section. The turbo generator is arranged inside the differential connecting barrel. A controller, a temperature sensor and a lithium battery pack are arranged in the inner cavity of the first adapter sleeve. The upper end and the lower end of the first adapter sleeve are fixedly connected to the lower end of the differential connecting barrel and the upper end of the heat insulation connecting barrel respectively. The heating resistance wire is arranged on the outer wall of the inner barrel. The heat insulation connecting barrel is arranged outside the inner barrel. The upper end of the second adapter sleeve is fixedly connected to the lower end of the inner barrel and the lower end of the heat insulation connecting barrel respectively. The lower end of the second adapter sleeve is fixedly connected to the upper end of the sliding connecting barrel, the upper end of the clamp seat and the lower end of the second adapter sleeve respectively. A core catcher is arranged inside the clamp seat. The sliding connecting barrel is slidably connected to the first ball valve connecting barrel. The clamp seat is arranged inside the first ball valve connecting barrel. The heat insulation valve body device is arranged inside the second ball valve connecting barrel. The upper end and the lower end of the second ball valve connecting barrel are fixedly connected to the lower end of the first ball valve connecting barrel and the ball valve respectively. The turbo generator is electrically connected to the controller, the temperature sensor and the lithium battery pack respectively. The controller is electrically connected to the temperature sensor and the lithium battery pack respectively. The heating resistance wire is electrically connected to the lithium battery pack. This pressure-holding coring tool has the following technical defects: (1) The tool has a complex structural design, high processing and manufacturing costs, and high technical service and maintenance costs; (2) It is difficult for this tool to meet the drilling coring operation in different postures, so the reliability of pressure-holding coring operation in directional wells and horizontal wells is not high; (3) It is inconvenient to maintain this tool on site, and the construction and installation efficiency is low; (4) It is difficult to guarantee the coring recovery rate in coalbed methane and easily fractured formations. Summary of the Invention

[0006] The present invention provides a pressure-holding coring tool, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problem that existing probe-type instruments cannot be quickly disassembled and assembled.

[0007] The technical solution of the present invention is achieved by the following measures: A pressure-holding coring tool includes an upper sub, a flow-dividing inner barrel, a centralizer, an outer barrel, a lower sub, a coring bit, a built-in high-strength suspension assembly, a pressure-graded differential assembly, a pressure compensation assembly, and a ball-valve type core-cutting sealing assembly. The upper sub, the centralizer, the outer barrel, the lower sub, and the coring bit are fixedly installed together from top to bottom in sequence; a flow-dividing inner barrel with its lower end located inside the centralizer is installed in the upper sub in a limited way. There is a built-in high-strength suspension assembly between the upper end of the flow-dividing inner barrel and the upper sub. A pressure-graded differential assembly with its lower end located inside the outer barrel is provided at the lower part of the flow-dividing inner barrel. The lower end of the pressure-graded differential assembly is installed with a pressure compensation assembly with its lower end located inside the lower sub. The lower end of the pressure compensation assembly is installed with a ball-valve type core-cutting sealing assembly with its lower end located inside the coring bit.

[0008] The following is a further optimization and / or improvement of the above-mentioned invention technical solution: The above-mentioned built-in high-strength suspension assembly may include a sealing gland, tapered roller bearings, deep groove ball bearings, a first sealing ring, a friction ring, cylindrical roller bearings, a first sliding bearing, fixing pins, and a sealing grease retaining ring. The inner side of the lower end of the upper sub is provided with a first inner ring platform and a second inner ring platform with gradually decreasing inner diameters from top to bottom in sequence. The outer side of the upper part of the flow-dividing inner barrel corresponding to the middle position of the first inner ring platform is provided with a first outer ring platform. The inner side of the upper end of the flow-dividing inner barrel is fixedly installed with a sealing gland with its upper end located above the first inner ring platform. The outer side of the upper end of the sealing gland is provided with a second outer ring platform with its lower side seated on the upper side of the first inner ring platform; there is a first sealing ring between the sealing gland and the flow-dividing inner barrel. Tapered roller bearings and deep groove ball bearings are arranged at intervals up and down on the outer side of the flow-dividing inner barrel corresponding to the position between the second outer ring platform and the first outer ring platform. A friction ring and cylindrical roller bearings are arranged on the outer side of the flow-dividing inner barrel from top to bottom in sequence corresponding to the position between the first outer ring platform and the second inner ring platform. At least two groups of first sliding bearings are arranged between the second inner ring platform and the flow-dividing inner barrel from top to bottom in sequence. The lower side of the upper sub is fixedly installed with a sealing grease retaining ring located on the outer side of the flow-dividing inner barrel through fixing pins.

[0009] The above-mentioned pressure-graded differential assembly may include a differential seal cylinder, a positioning cylinder, a positioning pin, a compression spring, a second sealing ring, a ball seat, a fixed shear pin, and a steel ball. The inner side of the lower end of the shunt inner cylinder is fixedly installed with a ball seat through a fixed shear pin, and a steel ball is arranged on the inner side of the upper part of the ball seat. The outer side of the lower end of the shunt inner cylinder is provided with a differential seal cylinder. The differential seal cylinder is provided with a liquid passage with an upward opening. The inner side of the upper end of the differential seal cylinder is provided with a third inner ring platform. The inner side of the upper part of the third inner ring platform is provided with a seal ring groove, and a second sealing ring is arranged in the seal ring groove. The inner side of the lower end of the third inner ring platform is provided with a differential ring groove. A plurality of upper diversion holes penetrating inside and outside are arranged on the differential seal cylinder corresponding to the position of the differential ring groove. A plurality of lower diversion holes penetrating inside and outside are arranged at the lower part of the differential seal cylinder. A positioning cylinder is fixedly installed on the outer side of the lower end of the shunt inner cylinder corresponding to the lower side position of the third inner ring platform. The outer side of the upper part of the positioning cylinder is provided with a positioning outer hole. A positioning pin and a compression spring are arranged in the positioning outer hole in sequence from outside to inside. A positioning ring groove is arranged on the inner side of the upper part of the differential seal cylinder corresponding to the position below the positioning outer hole. The lower end of the differential seal cylinder is fixedly installed with a pressure compensation assembly.

[0010] The above-mentioned pressure compensation assembly may include a pressure-holding cylinder, an opening support ring, and a starting valve. The pressure-holding cylinder is provided with a gas passage with a downward opening. The outer side of the upper part of the pressure-holding cylinder is provided with an opening support ring located inside the lower joint. The outer side of the lower part of the pressure-holding cylinder is provided with an installation hole communicating with the gas passage. A starting valve capable of plugging the gas passage in the closed state is installed in the installation hole. The outer end of the starting valve is provided with a control rod capable of being opened by rotation. The control rod is in an L shape. An opening block is arranged on the inner side of the opening support ring corresponding to the position of the control rod. An opening groove is arranged on the opening block with a downward opening and capable of allowing the control rod to enter and rotate to open. High-pressure gas is arranged in the gas passage corresponding to the position above the starting valve.

[0011] The above-mentioned ball valve type core cutting seal assembly may include a core-taking inner cylinder, a core catcher sleeve, a second sliding bearing, a core catcher, a retaining ring, a closing support ring, and a ball valve core. The inner side of the lower end of the core-taking bit is provided with a fourth inner ring platform. A plurality of flow holes are arranged at intervals along the circumference on the fourth inner ring platform. The lower end of the pressure compensation assembly is fixedly installed with a core-taking inner cylinder. The outer side of the lower end of the core-taking inner cylinder is fixedly installed with a core catcher sleeve. A core catcher is arranged on the inner side of the upper part of the core catcher sleeve. The outer side of the core catcher sleeve is provided with a closing support ring seated on the upper side of the fourth inner ring platform. An installation ring groove is arranged on the outer side of the upper end of the closing support ring. A retaining ring and a second sliding bearing are arranged in the installation ring groove from top to bottom in sequence. A ball valve core in an open state is arranged on the inner side of the lower part of the core catcher sleeve. The outer end of the ball valve core is provided with a rotating rod capable of being closed by rotation. The rotating rod is in an L shape. A closing block is arranged on the inner side of the closing support ring corresponding to the position of the rotating rod. A closing groove is arranged on the closing block with a downward opening and capable of allowing the rotating rod to enter and rotate to close.

[0012] The structure of the present invention is reasonable and compact, and it is convenient to use. By setting the sealing column, the sealing performance inside the pipe joint is ensured, and the liquid in the measuring pipeline is prevented from overflowing from the upper end of the pipe joint. By adopting a split design of the front sealing body and the rear sealing body for the sealing column, it is convenient for the measuring probe to pass through the lower end of the pipe joint after being inserted between the front sealing body and the rear sealing body to complete the measurement, featuring stability, reliability, and rapidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Attached Figure 1 It is a front view sectional structure schematic diagram of the upper half of Embodiments 1 to 5 of the present invention.

[0014] Attached Figure 2 It is a front view sectional structure schematic diagram of the lower half of Embodiments 1 to 5 of the present invention.

[0015] Attached Figure 3 It is for attached Figure 1 It is a front view sectional structure schematic diagram in the use state.

[0016] Attached Figure 4 It is for attached Figure 2 It is a front view sectional structure schematic diagram in the use state.

[0017] The codes in the drawings are respectively: 1 is the upper joint, 2 is the shunt inner cylinder, 3 is the centralizer, 4 is the outer cylinder, 5 is the lower joint, 6 is the coring bit, 7 is the sealing gland, 8 is the tapered roller bearing, 9 is the deep groove ball bearing, 10 is the first sealing ring, 11 is the friction ring, 12 is the cylindrical roller bearing, 13 is the first sliding bearing, 14 is the fixing pin, 15 is the sealing grease retaining ring, 16 is the differential sealing cylinder, 17 is the positioning cylinder, 18 is the positioning pin, 19 is the compression spring, 20 is the second sealing ring, 21 is the ball seat, 22 is the fixing shear pin, 23 is the steel ball, 24 is the pressure maintaining cylinder, 25 is the opening support ring, 26 is the start valve, 27 is the coring inner cylinder, 28 is the core catcher sleeve, 29 is the second sliding bearing, 30 is the core catcher, 31 is the retaining ring, 32 is the core, 33 is the closing support ring, 34 is the ball valve spool, 35 is the first inner ring platform, 36 is the second inner ring platform, 37 is the third inner ring platform, 38 is the first outer ring platform, 39 is the second outer ring platform, 40 is the differential ring groove, 41 is the positioning ring groove, 42 is the upper flow guiding hole, 43 is the lower flow guiding hole, 44 is the flow through hole, 45 is the liquid passage, 46 is the gas passage, 47 is the start block, 48 is the closing block. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The present invention is not limited by the following embodiments, and the specific implementation manners can be determined according to the technical solution of the present invention and the actual situation.

[0019] In the present invention, for the convenience of description, the description of the relative position relationship of each component is based on the attached drawings of the specification Figure 1It is described in the layout mode, for example, the positional relationships such as front, back, top, bottom, left, and right are determined according to the layout direction of the accompanying drawings of the specification.

[0020] The present invention will be further described below in conjunction with embodiments and the accompanying drawings: Embodiment 1: As shown in Figure 1 , 2 , 3, and 4, the pressure-holding coring tool includes an upper sub 1, a flow-dividing inner barrel 2, a centralizer 3, an outer barrel 4, a lower sub 5, a coring bit 6, a built-in high-strength suspension assembly, a pressure-graded differential assembly, a pressure compensation assembly, and a ball-valve type core-cutting seal assembly. The upper sub 1, the centralizer 3, the outer barrel 4, the lower sub 5, and the coring bit 6 are fixedly installed together in sequence from top to bottom; a flow-dividing inner barrel 2 with its lower end located inside the centralizer 3 is installed in a limited position inside the upper sub 1. There is a built-in high-strength suspension assembly between the upper end of the flow-dividing inner barrel 2 and the upper sub 1. A pressure-graded differential assembly with its lower end located inside the outer barrel 4 is provided at the lower part of the flow-dividing inner barrel 2. The lower end of the pressure-graded differential assembly is installed with a pressure compensation assembly with its lower end located inside the lower sub 5. The lower end of the pressure compensation assembly is installed with a ball-valve type core-cutting seal assembly with its lower end located inside the coring bit 6. During the use process, by setting the built-in high-strength suspension assembly, flexible rotation in different postures is satisfied; by setting the pressure-graded differential assembly, the opening and closing of different functions of the tool are realized at different pressure levels; by setting the pressure compensation assembly, pressure compensation for the ball-valve type core-cutting seal assembly is realized; by setting the ball-valve type core-cutting seal assembly, coring and core-cutting operations are realized; through the design of modular built-in high-strength suspension assembly, pressure-graded differential assembly, pressure compensation assembly, and ball-valve type core-cutting seal assembly, the problem of low on-site maintenance efficiency is solved, and the operation cost is reduced. According to requirements, the coring and core-cutting structures in the ball-valve type core-cutting seal assembly are prior art known to the public, and they can be similar designs in a lock-claw suspension type pressurized coring device disclosed in a Chinese patent document with the publication number CN105927175B. The ball-valve seal structure is prior art known to the public, and it can be similar designs in a pressure-holding coring tool disclosed in a Chinese patent document with the publication number CN115142804B.

[0021] According to actual needs, the above pressure-holding coring tool can be further optimized or / and improved: Embodiment 2: As shown in Figure 1 , 2As shown in FIGS. 3 and 4, the built-in high-strength suspension assembly includes a sealing gland 7, a tapered roller bearing 8, a deep groove ball bearing 9, a first sealing ring 10, a friction ring 11, a cylindrical roller bearing 12, a first sliding bearing 13, a fixing pin 14 and a sealing grease retaining ring 3115. Inside the lower end of the upper joint 1, there are a first inner ring platform 35 and a second inner ring platform 36 with gradually decreasing inner diameters from top to bottom. On the outer side of the upper part of the flow splitting inner cylinder 2 corresponding to the middle position of the first inner ring platform 35, there is a first outer ring platform 38. The sealing gland 7 with its upper end located above the first inner ring platform 35 is fixedly installed inside the upper end of the flow splitting inner cylinder 2. On the outer side of the upper end of the sealing gland 7, there is a second outer ring platform 39 seated on the upper side of the first inner ring platform 35. A first sealing ring 10 is provided between the sealing gland 7 and the flow splitting inner cylinder 2. A tapered roller bearing 8 and a deep groove ball bearing 9 are arranged at intervals up and down on the outer side of the flow splitting inner cylinder 2 corresponding to the position between the second outer ring platform 39 and the first outer ring platform 38. A friction ring 11 and a cylindrical roller bearing 12 are successively arranged from top to bottom on the outer side of the flow splitting inner cylinder 2 corresponding to the position between the first outer ring platform 38 and the second inner ring platform 36. At least two groups of first sliding bearings 13 are successively arranged between the second inner ring platform 36 and the flow splitting inner cylinder 2 from top to bottom. The lower side of the upper joint 1 is fixedly installed with a sealing grease retaining ring 3115 located outside the flow splitting inner cylinder 2 through a fixing pin 14. During use, by setting the tapered roller bearing 8, the deep groove ball bearing 9, the cylindrical roller bearing 12 and the first sliding bearing 13, the tool rotates flexibly in different postures, solving the technical requirements for pressure-holding coring in vertical wells, directional wells and horizontal wells, and helping the oilfield company to achieve the effective development of oil and gas resources; by setting the sealing gland 7, the first sealing ring 10 and the sealing grease retaining ring 3115, the internal sealing performance is ensured, wear is reduced, and the service life is improved.

[0022] Embodiment 3: As shown in the appendix Figure 1 、 2As shown in FIGS. 3 and 4, the pressure-graded differential assembly includes a differential seal cylinder 16, a positioning cylinder 17, a positioning pin 18, a compression spring 19, a second sealing ring 20, a ball seat 21, a fixed shear pin 22 and a steel ball 23. The inner side of the lower end of the shunt inner cylinder 2 is fixedly installed with a ball seat 21 through a fixed shear pin 22, and a steel ball 23 is arranged on the inner side of the upper part of the ball seat 21; a differential seal cylinder 16 is arranged on the outer side of the lower end of the shunt inner cylinder 2. The differential seal cylinder 16 is provided with a liquid passage 45 with an upward opening. The inner side of the upper end of the differential seal cylinder 16 is provided with a third inner ring platform 37. The inner side of the upper part of the third inner ring platform 37 is provided with a sealing ring groove, and a second sealing ring 20 is arranged in the sealing ring groove. The inner side of the lower end of the third inner ring platform 37 is provided with a differential ring groove 40. A plurality of upper diversion holes 42 that penetrate inside and outside are arranged on the differential seal cylinder 16 corresponding to the position of the differential ring groove 40. A plurality of lower diversion holes 43 that penetrate inside and outside are arranged at the lower part of the differential seal cylinder 16. A positioning cylinder 17 is fixedly installed on the outer side of the lower end of the shunt inner cylinder 2 corresponding to the lower side position of the third inner ring platform 37. The outer side of the upper part of the positioning cylinder 17 is provided with a positioning outer hole. A positioning pin 18 and a compression spring 19 are arranged in the positioning outer hole from outside to inside in sequence. A positioning ring groove 41 is arranged on the inner side of the upper part of the differential seal cylinder 16 corresponding to the position below the positioning outer hole; a pressure compensation assembly is fixedly installed at the lower end of the differential seal cylinder 16. During the use process, after the steel ball 23 falls into the ball seat 21, the central channel of the shunt inner cylinder 2 is blocked. The liquid enters the differential ring groove 40 from the upper diversion holes 42, pushes the differential seal cylinder 16 to move upward until the positioning pin 18 is pushed into the positioning ring groove 41 under the action of the compression spring 19, and continues to apply pressure to cut off the fixed shear pin 22. The ball seat 21 and the steel ball 23 fall to the bottom of the liquid passage 45 of the differential seal cylinder 16 and no longer block the central channel of the shunt inner cylinder 2. The liquid flows out of the differential seal cylinder 16 from the lower diversion holes 43.

[0023] Example 4: As shown in the appendix Figure 1 、 2, as shown in Figures 3 and 4, the pressure compensation assembly includes a pressure holding cylinder 24, an opening support ring 25 and a start valve 26. The pressure holding cylinder 24 is provided with a gas passage 46 opening downward. An opening support ring 25 located within the lower joint 5 is provided on the outer side of the upper part of the pressure holding cylinder 24. An installation hole communicating with the gas passage 46 is provided on the outer side of the lower part of the pressure holding cylinder 24. A start valve 26 capable of blocking the gas passage 46 in the closed state is installed in the installation hole. The outer end of the start valve 26 is provided with a control rod that can be rotated to open it. The control rod is L-shaped. An activation block 47 is provided on the inner side of the opening support ring 25 corresponding to the position of the control rod. The activation block 47 is provided with an opening groove opening downward and capable of allowing the control rod to enter and rotate to open after entering. High-pressure gas is provided in the gas passage 46 at a position above the start valve 26. During use, by providing the opening support ring 25, after the start valve 26 moves upward, the control rod can enter the opening groove and rotate 90° to rotate the internal valve core of the start valve 26, thereby opening the start valve 26. According to requirements, the structure of the control rod can be similar to that of a "faucet". When it is in a horizontal state, it cannot enter the opening groove. It can only be rotated 90° passively during its upward movement. At this time, the control rod is in a vertical state, and thus enters the opening groove, so that the start valve 26 is switched from the closed state to the open state.

[0024] Example 5: As shown in the attached Figure 1 , 2As shown in Figures 3 and 4, the ball valve type core cutting seal assembly includes a core inner barrel 27, a core catcher sleeve 28, a second sliding bearing 29, a core catcher 30, a retaining ring 31, a closing support ring 33 and a ball valve core 34. There is a fourth inner ring platform on the inner side of the lower end of the core bit 6, and a number of flow holes 44 are arranged at intervals along the circumference on the fourth inner ring platform; the lower end of the pressure compensation assembly is fixedly installed with a core inner barrel 27, the outer side of the lower end of the core inner barrel 27 is fixedly installed with a core catcher sleeve 28, a core catcher 30 is arranged on the inner side of the upper part of the core catcher sleeve 28, a closing support ring 33 sitting on the upper side of the fourth inner ring platform is arranged on the outer side of the core catcher sleeve 28, an installation ring groove is arranged on the outer side of the upper end of the closing support ring 33, and a retaining ring 31 and a second sliding bearing 29 are arranged in sequence from top to bottom in the installation ring groove. A ball valve core 34 in an open state is arranged on the inner side of the lower part of the core catcher sleeve 28. A rotating rod capable of closing by rotation is arranged at the outer end of the ball valve core 34. The rotating rod is L-shaped. A closing block 48 is arranged on the inner side of the closing support ring 33 corresponding to the position of the rotating rod. A closing groove opening downward and allowing the rotating rod to enter and rotate to close is arranged on the closing block 48. During the use process, by arranging the core catcher sleeve 28 and the core catcher 30, the core catcher 30 can effectively hold the core tightly, prevent the core from sliding down, increase stability, ensure the core recovery rate, and meet the user's research on formation physical property data; by arranging the closing support ring 33, after the ball valve core 34 moves upward, the rotating rod can enter the closing groove and rotate 90° to make the ball valve core 34 rotate, so as to close the ball valve core 34; by arranging the second sliding bearing 29, the friction during the rotation of the core bit 6 is reduced. According to requirements, the structure of the rotating rod can be similar to the structure of a "water faucet". When it is in a horizontal state, it cannot enter the closing groove. It can only rotate 90° passively during its upward movement. At this time, the rotating rod is in a vertical state, so as to enter the closing groove, so that the ball valve core 34 is switched from the open state to the closed state.

[0025] The above technical features constitute an embodiment of the present invention, which has strong adaptability and implementation effects. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

[0026] During the use process, the working principle of the best embodiment of the present invention can be as follows: (1) Nitrogen equivalent to the bottom hole pressure is pre-filled in the gas passage 46 of the pressure holding cylinder 24. At this time, the start valve 26 is in a closed state and the ball valve core 34 is in an open state; (2) After the differential seal cylinder 16 moves upward, the start valve 26 enters an open state under the action of the opening support ring 25, and the pressure balance valve arranged therein enters a working state. When the pressure in the core inner barrel 27 decreases during the coring operation, the pressure balance valve will connect the gas passage 46 above it to realize pressure compensation for the core inner barrel 27; After the differential sealing cylinder 16 moves upward, the ball valve spool 34 enters the closed state under the action of the closing support ring 33, thereby closing the lower end of the core catcher sleeve 28 after coring.

Claims

1. A pressure-maintaining coring tool, characterized in that it includes an upper sub, a flow-dividing inner barrel, a centralizer, an outer barrel, a lower sub, a coring bit, an internal high-strength suspension assembly, a pressure-graded differential assembly, a pressure compensation assembly and a ball-valve type core-cutting seal assembly. The upper sub, the centralizer, the outer barrel, the lower sub and the coring bit are fixedly installed together from top to bottom in sequence; the flow-dividing inner barrel with its lower end located inside the centralizer is installed in the upper sub with internal limit. An internal high-strength suspension assembly is provided between the upper end of the flow-dividing inner barrel and the upper sub. A pressure-graded differential assembly with its lower end located inside the outer barrel is provided at the lower part of the flow-dividing inner barrel. The pressure compensation assembly with its lower end located inside the lower sub is installed at the lower end of the pressure-graded differential assembly. The ball-valve type core-cutting seal assembly with its lower end located inside the coring bit is installed at the lower end of the pressure compensation assembly.

2. The pressure-maintaining coring tool according to claim 1, characterized in that the internal high-strength suspension assembly includes a seal gland, tapered roller bearings, deep groove ball bearings, a first sealing ring, a friction ring, cylindrical roller bearings, a first sliding bearing, fixing pins and a seal grease retaining ring. The inner side of the lower end of the upper sub has a first inner ring platform and a second inner ring platform with gradually decreasing inner diameters from top to bottom. The outer side of the upper part of the flow-dividing inner barrel corresponding to the middle position of the first inner ring platform is provided with a first outer ring platform. The seal gland with its upper end located above the first inner ring platform is fixedly installed on the inner side of the upper end of the flow-dividing inner barrel. The outer side of the upper end of the seal gland is provided with a second outer ring platform seated on the upper side of the first inner ring platform; a first sealing ring is provided between the seal gland and the flow-dividing inner barrel. The tapered roller bearings and deep groove ball bearings are arranged at intervals up and down on the outer side of the flow-dividing inner barrel corresponding to the position between the second outer ring platform and the first outer ring platform. The friction ring and cylindrical roller bearings are arranged in sequence from top to bottom on the outer side of the flow-dividing inner barrel corresponding to the position between the first outer ring platform and the second inner ring platform. At least two groups of first sliding bearings are arranged in sequence from top to bottom between the second inner ring platform and the flow-dividing inner barrel. The lower side of the upper sub is fixedly installed with a seal grease retaining ring located on the outer side of the flow-dividing inner barrel through fixing pins.

3. The pressure-maintaining coring tool according to claim 1 or 2, characterized in that the pressure-graded differential assembly includes a differential seal barrel, a positioning barrel, positioning pins, compression springs, a second sealing ring, a ball seat, fixing shear pins and steel balls. The ball seat is fixedly installed on the inner side of the lower end of the flow-dividing inner barrel through fixing shear pins. Steel balls are provided on the inner side of the upper part of the ball seat; the differential seal barrel is provided on the outer side of the lower end of the flow-dividing inner barrel. The differential seal barrel is provided with a liquid channel with an upward opening. The inner side of the upper end of the differential seal barrel is provided with a third inner ring platform. A seal ring groove is provided on the inner side of the upper part of the third inner ring platform. The second sealing ring is provided in the seal ring groove. A differential ring groove is provided on the inner side of the lower end of the third inner ring platform. A plurality of upper diversion holes penetrating inside and outside are provided on the differential seal barrel corresponding to the differential ring groove. A plurality of lower diversion holes penetrating inside and outside are provided at the lower part of the differential seal barrel. The positioning barrel is fixedly installed on the outer side of the lower end of the flow-dividing inner barrel corresponding to the lower side of the third inner ring platform. A positioning outer hole is provided on the outer side of the upper part of the positioning barrel. The positioning pins and compression springs are arranged from outside to inside in the positioning outer hole. A positioning ring groove is provided on the inner side of the upper part of the differential seal barrel corresponding to the position below the positioning outer hole; the lower end of the differential seal barrel is fixedly installed with the pressure compensation assembly.

4. The pressure-holding coring tool according to claim 1 or 2, characterized in that the pressure compensation assembly includes a pressure-holding cylinder, an opening support ring and a starting valve. The pressure-holding cylinder is provided with a gas passage opening downward. An opening support ring located inside the lower sub is provided on the outer side of the upper part of the pressure-holding cylinder. An installation hole communicating with the gas passage is provided on the outer side of the lower part of the pressure-holding cylinder. A starting valve capable of plugging the gas passage in a closed state is installed in the installation hole. The outer end of the starting valve is provided with a control rod capable of being opened by rotation. The control rod is L-shaped. A starting block is provided on the inner side of the opening support ring corresponding to the position of the control rod. An opening groove opening downward and capable of allowing the control rod to enter and rotate to open is provided on the starting block. High-pressure gas is provided in the gas passage corresponding to the upper position of the starting valve.

5. The pressure-holding coring tool according to claim 3, characterized in that the pressure compensation assembly includes a pressure-holding cylinder, an opening support ring and a starting valve. The pressure-holding cylinder is provided with a gas passage opening downward. An opening support ring located inside the lower sub is provided on the outer side of the upper part of the pressure-holding cylinder. An installation hole communicating with the gas passage is provided on the outer side of the lower part of the pressure-holding cylinder. A starting valve capable of plugging the gas passage in a closed state is installed in the installation hole. The outer end of the starting valve is provided with a control rod capable of being opened by rotation. The control rod is L-shaped. A starting block is provided on the inner side of the opening support ring corresponding to the position of the control rod. An opening groove opening downward and capable of allowing the control rod to enter and rotate to open is provided on the starting block. High-pressure gas is provided in the gas passage corresponding to the upper position of the starting valve.

6. The pressure-holding coring tool according to claim 1 or 2 or 5, characterized in that the ball valve type core cutting seal assembly includes a coring inner barrel, a core catcher sleeve, a second sliding bearing, a core catcher, a retaining ring, a closing support ring and a ball valve core. A fourth inner ring platform is provided on the inner side of the lower end of the coring bit. A plurality of flow holes are provided at intervals along the circumference on the fourth inner ring platform. The lower end of the pressure compensation assembly is fixedly installed with a coring inner barrel. A core catcher sleeve is fixedly installed on the outer side of the lower end of the coring inner barrel. A core catcher is provided on the inner side of the upper part of the core catcher sleeve. A closing support ring seated on the upper side of the fourth inner ring platform is provided on the outer side of the core catcher sleeve. An installation ring groove is provided on the outer side of the upper end of the closing support ring. A retaining ring and a second sliding bearing are successively provided in the installation ring groove from top to bottom. A ball valve core in an open state is provided on the inner side of the lower part of the core catcher sleeve. The outer end of the ball valve core is provided with a rotating rod capable of being closed by rotation. The rotating rod is L-shaped. A closing block is provided on the inner side of the closing support ring corresponding to the position of the rotating rod. A closing groove opening downward and capable of allowing the rotating rod to enter and rotate to close is provided on the closing block.

7. The pressure-holding coring tool according to claim 1 or 2 or 3 or 6, characterized in that The ball valve type core cutting seal assembly includes a core barrel, a core catcher sleeve, a second sliding bearing, a core catcher, a retaining ring, a closing support ring and a ball valve core. There is a fourth inner ring platform on the inner side of the lower end of the core bit, and a number of flow holes are arranged at intervals along the circumference on the fourth inner ring platform; the lower end of the pressure compensation assembly is fixedly installed with a core barrel, the outer side of the lower end of the core barrel is fixedly installed with a core catcher sleeve, the inner side of the upper part of the core catcher sleeve is provided with a core catcher, the outer side of the core catcher sleeve is provided with a closing support ring seated on the upper side of the fourth inner ring platform, the outer side of the upper end of the closing support ring is provided with an installation ring groove, and a retaining ring and a second sliding bearing are arranged in sequence from top to bottom in the installation ring groove. The inner side of the lower part of the core catcher sleeve is provided with a ball valve core in an open state, the outer end of the ball valve core is provided with a rotating rod that can be rotated to close it, the rotating rod is L-shaped, a closing block is arranged on the inner side of the closing support ring corresponding to the position of the rotating rod, and a closing groove that opens downward and can allow the rotating rod to enter and rotate to close is arranged on the closing block.

8. The pressure maintaining core sampling tool according to claim 4, characterized in that the ball valve type core cutting seal assembly includes a core barrel, a core catcher sleeve, a second sliding bearing, a core catcher, a retaining ring, a closing support ring and a ball valve core. There is a fourth inner ring platform on the inner side of the lower end of the core bit, and a number of flow holes are arranged at intervals along the circumference on the fourth inner ring platform; the lower end of the pressure compensation assembly is fixedly installed with a core barrel, the outer side of the lower end of the core barrel is fixedly installed with a core catcher sleeve, the inner side of the upper part of the core catcher sleeve is provided with a core catcher, the outer side of the core catcher sleeve is provided with a closing support ring seated on the upper side of the fourth inner ring platform, the outer side of the upper end of the closing support ring is provided with an installation ring groove, and a retaining ring and a second sliding bearing are arranged in sequence from top to bottom in the installation ring groove. The inner side of the lower part of the core catcher sleeve is provided with a ball valve core in an open state, the outer end of the ball valve core is provided with a rotating rod that can be rotated to close it, the rotating rod is L-shaped, a closing block is arranged on the inner side of the closing support ring corresponding to the position of the rotating rod, and a closing groove that opens downward and can allow the rotating rod to enter and rotate to close is arranged on the closing block.

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