Pressurizing mechanism for pressure-maintaining coring

Abstract

The pressurizing mechanism comprises a pressurizing inner cylinder, a pressurizing outer cylinder with the upper end arranged outside the pressurizing inner cylinder in a sleeving mode, a steel ball used for axially locking the pressurizing outer cylinder and the pressurizing inner cylinder and an unlocking mechanism used for unlocking axial locking, and the steel ball can be installed in the cylinder wall of the pressurizing inner cylinder and the cylinder wall of the pressurizing outer cylinder at the same time to achieve axial locking; the unlocking mechanism comprises an unlocking sleeve installed in the pressurizing inner cylinder, unlocking is achieved by enabling the unlocking sleeve to slide downwards relative to the pressurizing inner cylinder, and when the unlocking sleeve is located at an unlocking position, the steel ball retreats from the cylinder wall of the pressurizing outer cylinder and is installed in the unlocking sleeve and the cylinder wall of the pressurizing inner cylinder at the same time, so that axial locking is relieved; when the axial locking is released, the pressurizing outer barrel can move downwards from the first position to the second position relative to the pressurizing inner barrel. Unlocking is achieved through sliding of the unlocking sleeve, and fixing is safer than pure pin fixing; according to the pressurizing mechanism, the two-way movement action that the core catcher is pressed downwards for core cutting and the core cabin is pulled upwards for pressure maintaining can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pressure-maintaining coring, in particular to a pressure-maintaining coring pressurizing mechanism. BACKGROUND

[0002] The deep oil and gas low-disturbance temperature and pressure-maintaining coring technology is a coring technology that can keep the extracted core always in the original formation pore water pressure, original temperature and original state. The technology is realized through the mutual cooperation of a pressure-maintaining assembly, a temperature-maintaining assembly, a rotation-preventing assembly and a pressurizing assembly.

[0003] When pressurizing coring is performed on a loose formation, the pressurizing method is usually to use the ball throwing method to pressurize and shear a starting pin, then to apply pressure to the coring barrel and the core claw to make them descend, and finally to make the core claw contract to complete the cutting of the core. Because the pump pressure is not stable when the drilling fluid circulates, the drilling fluid will have an impact, which may cause the pin to be sheared in advance. This method that simply relies on the pin for fixation is not safe enough. SUMMARY

[0004] The present application provides a pressure-maintaining coring pressurizing mechanism.

[0005] The present application is realized through the following technical solutions: The pressure-maintaining coring pressurizing mechanism provided by the present application comprises a pressurizing inner barrel, a pressurizing outer barrel sleeved on the outside of the pressurizing inner barrel, a steel ball for axially locking the pressurizing outer barrel and the pressurizing inner barrel, and an unlocking mechanism for unlocking the axial locking of the pressurizing outer barrel and the pressurizing inner barrel. The steel ball can be simultaneously installed in the barrel wall of the pressurizing inner barrel and the pressurizing outer barrel to realize the axial locking. The unlocking mechanism comprises an unlocking sleeve installed in the pressurizing inner barrel. The unlocking sleeve has a locking position and an unlocking position. The unlocking sleeve is slid downward relative to the pressurizing inner barrel to switch the unlocking sleeve from the locking position to the unlocking position. When the unlocking sleeve is in the unlocking position, the steel ball is withdrawn from the barrel wall of the pressurizing outer barrel and simultaneously installed in the barrel wall of the unlocking sleeve and the pressurizing inner barrel, thereby unlocking the axial locking. When the axial locking is unlocked, the pressurizing outer barrel can be moved downward from a first position to a second position relative to the pressurizing inner barrel.

[0006] Optionally, a through hole is formed in the pipe wall of the pressurizing inner barrel and a steel ball is installed in the through hole. The diameter of the steel ball is greater than the thickness of the pipe wall of the pressurizing inner barrel. The inner wall of the pressurizing outer barrel has an annular inner groove matched with the steel ball. When the pressurizing outer barrel is in the first position, a part of the steel ball is installed in the pressurizing inner barrel and the other part of the steel ball is installed in the annular inner groove in the inner wall of the pressurizing outer barrel. The pressurizing inner barrel is axially fixed with the pressurizing outer barrel and can be circumferentially rotated.

[0007] Optionally, the unlocking sleeve has an annular outer groove that is adapted to the steel ball on the pressurizing inner tube; when the unlocking sleeve is in the unlocking position, the annular outer groove on the unlocking sleeve is aligned with the steel ball on the pressurizing inner tube, the steel ball can exit the annular inner groove on the pressurizing outer tube and enter the annular outer groove on the unlocking sleeve, thereby releasing the axial locking.

[0008] Optionally, the unlocking mechanism further comprises an unlocking ball, the unlocking sleeve is fixed in the pressurizing inner tube by an unlocking pin, at this time the unlocking sleeve is in the locking position; the unlocking sleeve has an internal flow channel, the top of the unlocking sleeve has a conical ball seat that is adapted to the unlocking ball, the outer sidewall of the unlocking sleeve has a first water passage that penetrates the internal flow channel of the unlocking sleeve, the first water passage is below the conical ball seat; the unlocking ball is configured to block the top opening of the internal flow channel of the unlocking sleeve when it is placed in the conical ball seat.

[0009] Optionally, the outer wall of the pressurizing inner tube has a first limiting step, the outer wall of the pressurizing outer tube has a second limiting step that is adapted to the first limiting step, the second limiting step is above the first limiting step, when the first limiting step and the second limiting step are in contact, the pressurizing outer tube cannot move downward relative to the pressurizing inner tube.

[0010] Optionally, the pressurizing mechanism for pressure-maintaining coring further comprises a spring, under the action of the spring, the pressurizing outer tube has a tendency to move downward from the first position to the second position relative to the pressurizing outer tube.

[0011] Optionally, the pressurizing mechanism for pressure-maintaining coring further comprises a differential mechanism, the differential mechanism comprises a differential inner tube, a differential outer tube, a differential ball seat, and a differential ball, the lower end of the differential inner tube is connected to the differential ball seat, the differential ball seat has a flow channel hole and a sealing surface that are adapted to the differential ball; the lower end of the differential outer tube is connected to the pressurizing inner tube, the sidewall of the differential outer tube has a second water passage that is adapted to the first water passage at a corresponding position, when the unlocking sleeve is in the locking position, the medium can flow from the internal flow channel of the pressurizing inner tube to the outside of the differential outer tube through the first water passage and the second water passage.

[0012] Optionally, the differential outer tube has a first pressure relief hole above the differential ball seat; one of the differential inner tube and the differential outer tube has a sawtooth-shaped retaining spring, the other has a safety pawl that is adapted to the sawtooth-shaped retaining spring; when the differential outer tube moves upward relative to the differential inner tube to a certain height, the safety pawl can be buckled on the sawtooth-shaped retaining spring, at this time the differential outer tube cannot move downward relative to the differential inner tube.

[0013] Optionally, the pressure-maintaining coring pressurizing mechanism further comprises a pressure relief sleeve fixed in the differential outer tube by a safety pin, an unlocking sleeve upper end mounted in the pressure relief sleeve, an unlocking sleeve lower end mounted in the pressurizing inner tube, and the pressure relief sleeve located between the unlocking sleeve and the differential outer tube; the differential outer tube has a second pressure relief hole corresponding to the position of the pressure relief sleeve, when the pressure relief sleeve is fixed in the differential outer tube by the safety pin, the second pressure relief hole is blocked by the pressure relief sleeve, and the medium cannot flow to the outside of the differential outer tube through the second pressure relief hole; when the safety pin of the pressure relief sleeve and the differential outer tube is cut by hydraulic pressure, the pressure relief sleeve can move downward relative to the differential outer tube, and when the pressure relief sleeve moves downward to a predetermined position, the second pressure relief hole on the differential outer tube is exposed, and the medium can flow to the outside of the differential outer tube through the second pressure relief hole.

[0014] Optionally, the differential outer tube has a limiting step matched with the pressure relief sleeve, when the pressure relief sleeve moves downward to abut against the limiting step of the pressure relief sleeve, the pressure relief sleeve moves to the predetermined position and cannot continue to move downward relative to the differential outer tube.

[0015] Compared with the prior art, the application has at least the following beneficial effects: 1. The application uses the sliding of the unlocking sleeve to unlock, which is safer than pure pin fixing; 2. The pressurizing mechanism of the application can realize the bidirectional movement of pressing down the core claw for cutting and lifting the core chamber for pressure maintaining.

[0016] Of course, implementing any of the schemes of the application does not necessarily need to achieve all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical schemes in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation to the scope, and other related drawings can also be obtained by those skilled in the art without creative labor on the premise of not paying.

[0018] Figure 1 The structure diagram of the pressure-maintaining coring pressurizing mechanism when the pressurizing outer tube is in the first position in the embodiment; Figure 2 The structure diagram of the pressure-maintaining coring pressurizing mechanism when the pressurizing outer tube is in the second position in the embodiment; Figure 3 The structure diagram of the coring device in the embodiment. DETAILED DESCRIPTION

[0019] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings of the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0020] It should be noted that the embodiments and features in the present application can be combined with each other without conflict. It should be noted that each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the embodiments can be referred to each other.

[0021] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly used when the product of the present application is used, or the orientation or positional relationship commonly understood by those skilled in the art, and are only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0022] In the description of the present application, it should also be noted that unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0023] As shown in the Figure 1 The preferred pressure maintaining coring pressurizing mechanism disclosed by the embodiment comprises a pressurizing inner cylinder 51, a pressurizing outer cylinder 52, a steel ball 56 for axially locking the pressurizing outer cylinder 52 and the pressurizing inner cylinder 51, and an unlocking mechanism for unlocking the axial locking of the pressurizing outer cylinder 52 and the pressurizing inner cylinder 51. The upper end of the pressurizing outer cylinder 52 is sleeved outside the pressurizing inner cylinder 51, and the steel ball 56 can be simultaneously installed in the cylinder wall of the pressurizing inner cylinder 51 and the pressurizing outer cylinder 52 to achieve the axial locking. The unlocking mechanism is used to make the steel ball 56 exit from the cylinder wall of the pressurizing outer cylinder 52 to unlock the axial locking. When the axial locking is unlocked, the pressurizing outer cylinder 52 can move downward from the first position to the second position relative to the pressurizing inner cylinder 51, and the downward pressurizing is realized by the downward movement of the pressurizing outer cylinder 52.

[0024] In some embodiments, the steel ball 56 is installed on the tube wall of the pressurized inner cylinder 51, and has a diameter greater than the thickness of the tube wall of the pressurized inner cylinder 51; the pressurized outer cylinder 52 has an annular inner groove 521 that is adapted to the steel ball 56, when the pressurized outer cylinder 52 is in the first position, a part of the steel ball 56 is installed in the pressurized inner cylinder 51, and another part of the steel ball 56 is installed in the annular inner groove 521 of the inner wall of the pressurized outer cylinder 52, the pressurized inner cylinder 51 is axially fixed with the pressurized outer cylinder 52 through the steel ball 56, and the pressurized inner cylinder 51 and the pressurized outer cylinder 52 can also rotate circumferentially through the steel ball 56.

[0025] As a preferred embodiment, the unlocking mechanism includes an unlocking sleeve 53 installed in the pressurized inner cylinder 51, and the outer wall of the unlocking sleeve 53 has an annular outer groove 532 that is adapted to the steel ball 56 on the pressurized inner cylinder 51; the unlocking sleeve 53 has a locking position and an unlocking position, as shown in FIG. 4, when the unlocking sleeve 53 is in the locking position, the pressurized outer cylinder 52 is in the first position; as shown in FIG. 5, when the unlocking sleeve 53 is in the unlocking position, the annular outer groove 532 on the unlocking sleeve 53 is aligned with the steel ball 56 of the pressurized inner cylinder 51, the steel ball 56 can exit from the annular inner groove 521 of the pressurized outer cylinder 52 and enter the annular outer groove 532 of the unlocking sleeve 53, thereby releasing the axial locking, at this time, the pressurized outer cylinder 52 can move from the first position to the second position relative to the pressurized inner cylinder 51. Figure 1 Figure 2

[0026] It is worth mentioning that the axial sliding distance of the unlocking sleeve 53 relative to the pressurized inner cylinder 51 is controlled by the axial size of the annular outer groove 532. When the steel ball 56 abuts against the top of the annular outer groove 532, the unlocking sleeve 53 cannot slide downward relative to the pressurized inner cylinder 51.

[0027] In some embodiments, the unlocking mechanism further includes an unlocking ball 54, and the unlocking sleeve 53 is fixed in the pressurized inner cylinder 51 by an unlocking pin 57, at this time, the unlocking sleeve 53 is in the locking position. The unlocking sleeve 53 has an internal flow channel, the top of the unlocking sleeve 53 has a conical ball seat 531 that is adapted to the unlocking ball 54, the outer wall of the unlocking sleeve 53 has a first water passage 510 that penetrates the internal flow channel of the unlocking sleeve 53, and the first water passage 510 is below the conical ball seat 531; the unlocking ball 54 is configured to block the top opening of the internal flow channel of the unlocking sleeve 53 when it is placed in the conical ball seat 531.

[0028] ​​In some embodiments, the outer wall of the pressurized inner cylinder 51 has a first limiting step 511, and the outer wall of the pressurized outer cylinder 52 has a second limiting step 522 adapted to the first limiting step 511, which is located above the first limiting step 511. When the first limiting step 511 and the second limiting step 522 abut against each other, the pressurized outer cylinder 52 cannot move downward relative to the pressurized inner cylinder 51.

[0029] In some embodiments, the pressure-pressurizing mechanism for core sampling further includes a spring 59, under the action of the spring 59, the pressure outer cylinder 52 tends to move downward from the first position to the second position relative to the pressure outer cylinder 52.

[0030] In some embodiments, the pressurized inner cylinder 51 is connected to a differential mechanism, which includes a differential inner tube 41, a differential outer tube 42, a differential ball seat 43, and a differential ball 44. The outer tube of the differential outer tube 42 is sleeved outside the differential inner tube 41, and there is a seal 45 between the two. The lower end of the differential inner tube 41 is connected to the differential ball seat 43. The differential ball seat 43 has a flow channel hole and a sealing surface adapted to the differential ball 44. There is also a seal 45 between the differential ball seat 43 and the differential outer tube 42.

[0031] The differential outer tube 42 has a first pressure relief hole 46, which is located above the differential ball seat 43. When the differential ball 44 is inserted, the drilling fluid cannot flow downward from the differential ball seat 43, so it can only flow out from the first pressure relief hole 46 and become pressurized in the sealed cavity formed between the differential outer tube 42 and the differential inner tube 41.

[0032] The lower end of the differential outer tube 42 is connected to the pressurized inner cylinder 51. The corresponding position on the side wall of the differential outer tube 42 has a second water passage 48 that is adapted to the first water passage 510. When the unlocking sleeve 53 is in the locked position, the medium can flow from the internal flow channel of the pressurized inner cylinder 51 through the first water passage 510 and the second water passage 48 to the outside of the differential outer tube 42.

[0033] In some embodiments, one of the differential inner tube 41 and the differential outer tube 42 has a serrated retaining ring 411, and the other has a safety claw 421 adapted to the serrated retaining ring 411. When the differential outer tube 42 moves upward relative to the differential inner tube 41 to a certain height, the safety claw 421 can be engaged with the serrated retaining spring 411. At this time, the differential outer tube 42 cannot move downward relative to the differential inner tube 41.

[0034] In some embodiments, the pressure-holding and coring mechanism further includes a pressure relief sleeve 55, which is fixed in the differential outer tube 42 by a safety pin 58. The upper end of the unlocking sleeve 53 is installed in the pressure relief sleeve 55, and the lower end of the unlocking sleeve 53 is installed in the pressure-pressurizing inner tube 51. The pressure relief sleeve 55 is located between the unlocking sleeve 53 and the differential outer tube 42. The differential outer tube 42 has a second pressure relief hole 47 corresponding to the position of the pressure relief sleeve 55. When the pressure relief sleeve 55 is fixed to the differential outer tube 42 by the safety pin 58, the second pressure relief hole 47 is blocked by the pressure relief sleeve 55, and the pressure relief sleeve 55 and the two sealing rings installed on the pressure relief sleeve 55 block the second pressure relief hole 47, so that the medium cannot flow to the outside of the differential outer tube 42 through the second pressure relief hole 47. When the safety pin 58 of the pressure relief sleeve 55 and the differential outer tube 42 is cut off by hydraulic pressure, the pressure relief sleeve 55 can be lowered relative to the differential outer tube 42. When the pressure relief sleeve 55 is lowered to a predetermined position, the second pressure relief hole 47 on the differential outer tube 42 is exposed, and the medium can flow to the outside of the differential outer tube 42 through the second pressure relief hole 47.

[0035] Optionally, the differential outer tube 42 has a limiting step matched with the pressure relief sleeve 55. When the pressure relief sleeve 55 is lowered to abut against the limiting step of the pressure relief sleeve 55, the pressure relief sleeve 55 is lowered to the predetermined position and cannot continue to be lowered relative to the differential outer tube 42.

[0036] The application uses the sliding of the unlocking sleeve to unlock, which is safer than pure pin fixing. The pressurizing mechanism of the application can realize the bidirectional movement of pressing down the core claw for cutting and lifting the core chamber for pressure maintaining.

[0037] As shown in Figure 3 The core taking device disclosed by the embodiment includes a pressure maintaining and core taking pressurizing mechanism, an outer tube assembly 1 and a core chamber assembly 7. The pressure maintaining and core taking pressurizing mechanism and the differential outer tube 42 are located in the outer tube assembly 1. The uppermost end of the outer tube assembly 1 is connected with a petroleum drill rod, and the lowermost end is connected with a core drill bit 10. The inner wall of the core drill bit 10 has a drill bit taper surface. The outer tube assembly 1 is provided with a suspension ring 21. The lower end of the suspension ring 21 is threadedly connected with a first stage separation mechanism 22, which is used to position the axial distance of the corer in the outer tube.

[0038] The differential inner tube 41 is threadedly connected below the first stage separation mechanism 22. The pressurizing outer cylinder 52 is threadedly connected with the lower end of the sensor sleeve 6. The pressurizing inner cylinder 51 or the unlocking sleeve 53 is axially provided with a spring 59 between the sensor sleeve 6. In the exemplary embodiment, the spring 59 is sleeved on the unlocking sleeve 53, and the two ends of the spring 59 act on the outer step of the unlocking sleeve 53 and the upper end surface of the sensor sleeve 6.

[0039] The sensor sleeve 6 is provided with a packaged sensor, which includes a pressure sensor, a temperature sensor and the like.

[0040] The core chamber assembly 7 includes an insulated and pressure-maintaining core chamber and an inner tube 70. The lower end of the sensor sleeve 6 is connected to the insulated and pressure-maintaining core chamber, and the lower end of the insulated and pressure-maintaining core chamber is connected to the core tube 8. A pressure-maintaining controller 9 is installed at the lower part of the inner tube 70, and a pressurized core claw 81 is connected to the lower end of the core tube 8. The pressure-maintaining controller 9 includes a valve seat and a valve cover, with one end of the valve cover movably connected to the valve seat, allowing the core tube 8 to pass through the valve seat. The structure and working principle of the pressure-maintaining controller 9 are conventional technologies in this field and will not be described in detail here.

[0041] In this embodiment, the working principle of the core extraction device is as follows: During coring operations, the pressure holding controller 9 is activated, and the core tube 8 is located inside the valve seat 91. First, the PIPPC is lowered to the target formation, and coring drilling begins. At this time, the first water passage 510 of the unlocking sleeve 53 connects to the second water passage 48 of the differential outer tube 42. Drilling fluid flows out through the first water passage 510 and the second water passage 48 into the annulus of the outer tube assembly 1. Figure 1 As shown; After the predetermined core length is reached, the unlocking ball 54 is lowered and falls onto the conical ball seat 531 of the unlocking sleeve 53, forming hydraulic pressure to shear the unlocking pin 57 between the unlocking sleeve 53 and the pressurized inner cylinder 51. The unlocking sleeve 53 descends, and when the annular outer groove 532 on the unlocking sleeve 53 aligns with the steel ball 56 of the pressurized inner cylinder 51, the axial constraint of the pressurized outer cylinder 52 is unlocked. The spring 59 at the bottom of the unlocking sleeve 53 presses down on the sensor sleeve 6, pushing the core chamber assembly 7 downwards. Under the pressure at the upper end, the pressurized core claw 81 retracts inward along the drill bit conical surface 101. When the second limiting step 522 of the pressurized outer cylinder 52 abuts against the first limiting step 511 on the outer wall of the pressurized inner cylinder 51, the pressurized outer cylinder 52 moves into position, and the pressurized core claw 81 completes the cutting and encapsulation of the core. Figure 2 As shown.

[0042] Hydraulic pressure shears off the safety pin 58 between the pressure relief sleeve 55 and the differential outer tube 42. The pressure relief sleeve 55 descends, exposing the second pressure relief hole 47 on the differential outer tube 42, and the drilling fluid water passage reopens. At this time, the differential ball 44 is inserted and falls onto the differential ball seat 43. The resulting hydraulic pressure lifts the differential outer tube 42 and drives the pressurized inner tube 51 upward. The pressurized inner tube 51 pulls the pressurized outer tube 52 and the core chamber assembly 7 upward through the limiting step surface formed between it and the pressurized outer tube 52. After passing the pressure holding controller 9, the pressure holding controller 9 automatically closes.

[0043] When the upper edge of the second pressure relief hole 47 of the differential outer tube 42 passes the seal 45 between the differential outer tube 42 and the differential ball seat 43, the hydraulic pressure rapidly and continuously decreases until the upper end of the core tube 8 presses against the inner tube 70, completing the lifting and shutting off the mud pump. At this time, the safety claw 421 on the differential outer tube 42 is suspended on the serrated retaining spring 411 of the differential inner cylinder 41. The heat-insulating and pressure-maintaining core chamber can be lifted by lifting the differential inner cylinder 41.

[0044] The coring device in this embodiment can achieve low-disturbance coring with dual-cylinder single-action. After coring is completed, the coring cylinder and core claw can move in both directions. First, it moves downward to perform a pressure-type core cutting action to wrap the core and prevent loose core from falling out. Then, it moves upward to trigger the pressure holding controller to complete the pressure holding action.

[0045] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pressure maintaining coring pressurizing mechanism characterized by comprising: The application relates to a pressure cylinder, which comprises: a pressure inner cylinder (51); a pressure outer cylinder (52) sleeved on the pressure inner cylinder (51); a steel ball (56) for axially locking the pressure outer cylinder (52) and the pressure inner cylinder (51), the steel ball (56) being simultaneously arranged in the cylinder wall of the pressure inner cylinder (51) and the pressure outer cylinder (52) to realize the axial locking; and an unlocking mechanism for releasing the axial locking of the pressure outer cylinder (52) and the pressure inner cylinder (51), the unlocking mechanism comprising an unlocking sleeve (53) arranged in the pressure inner cylinder (51), the unlocking sleeve (53) having a locking position and an unlocking position, the unlocking sleeve (53) being switched from the locking position to the unlocking position by sliding downward relative to the pressure inner cylinder (51), when the unlocking sleeve (53) is located at the unlocking position, the steel ball (56) is withdrawn from the cylinder wall of the pressure outer cylinder (52) and simultaneously arranged in the cylinder wall of the pressure inner cylinder (51) and the unlocking sleeve (53), so that the axial locking is released; when the axial locking is released, the pressure outer cylinder (52) can be moved downward from a first position to a second position relative to the pressure inner cylinder (51).

2. The pressure maintaining coring pressurizing mechanism according to claim 1, characterized by The steel ball (56) is arranged on the pipe wall of the pressure inner cylinder (51) and has a diameter larger than the thickness of the pipe wall of the pressure inner cylinder (51); The inner wall of the pressure outer cylinder (52) is provided with an annular inner groove (521) matched with the steel ball (56), when the pressure outer cylinder (52) is located at the first position, a part of the steel ball (56) is arranged in the pressure inner cylinder (51), and the other part of the steel ball (56) is arranged in the annular inner groove (521) of the inner wall of the pressure outer cylinder (52), the pressure inner cylinder (51) is axially fixed with the pressure outer cylinder (52) through the steel ball (56) and can be circumferentially rotated.

3. The pressure maintaining coring pressurizing mechanism according to claim 2, characterized by The outer wall of the unlocking sleeve (53) is provided with an annular outer groove (532) matched with the steel ball (56) on the pressure inner cylinder (51), when the unlocking sleeve (53) is located at the unlocking position, the annular outer groove (532) on the unlocking sleeve (53) is aligned with the steel ball (56) on the pressure inner cylinder (51), the steel ball (56) can be withdrawn from the annular inner groove (521) of the pressure outer cylinder (52) and arranged in the annular outer groove (532) of the unlocking sleeve (53), so that the axial locking is released.

4. The pressure maintaining coring pressurizing mechanism according to claim 2 or 3, characterized by The unlocking mechanism further comprises an unlocking small ball (54), the unlocking sleeve (53) is fixed in the pressure inner cylinder (51) by an unlocking pin (57), and the unlocking sleeve (53) is located at the locking position at this time; The unlocking sleeve (53) has an internal flow channel, the top of the unlocking sleeve (53) is provided with a conical ball seat (531) matched with the unlocking small ball (54), and the outer wall of the unlocking sleeve (53) is provided with a first water passing hole (510) penetrating the internal flow channel of the unlocking sleeve (53), the first water passing hole (510) is below the conical ball seat (531); The unlocking small ball (54) is configured to block the top opening of the internal flow channel of the unlocking sleeve (53) when being arranged in the conical ball seat (531).

5. The pressure maintaining coring pressurizing mechanism of claim 1, wherein The outer wall of the pressurizing inner cylinder (51) has a first limiting step (511), and the outer wall of the pressurizing outer cylinder (52) has a second limiting step (522) which is matched with the first limiting step (511) and is located above the first limiting step (511). When the first limiting step (511) and the second limiting step (522) are in contact, the pressurizing outer cylinder (52) cannot move downward relative to the pressurizing inner cylinder (51).

6. The pressure-maintaining coring pressurizing mechanism according to claim 1, characterized by The pressurizing outer cylinder (52) has a tendency to move downward from the first position to the second position relative to the pressurizing outer cylinder (52) under the action of the spring (59).

7. The pressure maintaining coring pressurizing mechanism of claim 1, wherein The differential mechanism comprises a differential inner tube (41), a differential outer tube (42), a differential ball seat (43) and a differential small ball (44). The lower end of the differential inner tube (41) is connected to the differential ball seat (43), and the differential ball seat (43) has a flow channel hole and a sealing surface which are matched with the differential small ball (44). The lower end of the differential outer tube (42) is connected to the pressurizing inner cylinder (51), and the sidewall of the differential outer tube (42) has a second water passage hole (48) which is matched with the first water passage hole (510) at the corresponding position. When the unlocking sleeve (53) is in the locked position, the medium can flow from the inner channel of the pressurizing inner cylinder (51) to the outside of the differential outer tube (42) through the first water passage hole (510) and the second water passage hole (48).

8. The pressure-maintaining coring pressurizing mechanism according to claim 7, characterized by The differential outer tube (42) has a first pressure relief hole (46) which is located above the differential ball seat (43). One of the differential inner tube (41) and the differential outer tube (42) has a sawtooth-shaped snap spring (411), and the other has a safety claw (421) which is matched with the sawtooth-shaped snap spring (411). When the differential outer tube (42) moves upward relative to the differential inner tube (41) to a certain height, the safety claw (421) can be buckled on the sawtooth-shaped snap spring (411), and at this time the differential outer tube (42) cannot move downward relative to the differential inner tube (41).

9. The pressure-maintaining coring pressurizing mechanism according to claim 7, characterized by The pressure relief sleeve (55) is fixed in the differential outer tube (42) by a safety pin (58), the upper end of the unlocking sleeve (53) is installed in the pressure relief sleeve (55), the lower end of the unlocking sleeve (53) is installed in the pressurizing inner cylinder (51), and the pressure relief sleeve (55) is located between the unlocking sleeve (53) and the differential outer tube (42). The differential outer tube (42) has a second pressure relief hole (47) at the position corresponding to the pressure relief sleeve (55). When the pressure relief sleeve (55) is fixed to the differential outer tube (42) by the safety pin (58), the second pressure relief hole (47) is blocked by the pressure relief sleeve (55), and the medium cannot flow to the outside of the differential outer tube (42) through the second pressure relief hole (47). When the safety pin (58) of the pressure relief sleeve (55) and the differential outer tube (42) is cut by hydraulic pressure, the pressure relief sleeve (55) can move downward relative to the differential outer tube (42). When the pressure relief sleeve (55) moves downward to a predetermined position, the second pressure relief hole (47) on the differential outer tube (42) is exposed, and the medium can flow to the outside of the differential outer tube (42) through the second pressure relief hole (47).

10. The pressure-maintaining coring pressurizing mechanism according to claim 9, characterized by The differential outer tube (42) has a limiting step which is matched with the pressure relief sleeve (55), when the pressure relief sleeve (55) goes down to the limiting step of the pressure relief sleeve (55), the pressure relief sleeve (55) goes down to the predetermined position and the pressure relief sleeve (55) cannot continue to go down relative to the differential outer tube (42).

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