CN115126433B - Plug-in pressure-holding coring device suitable for soft formation and its application method - Google Patents

Abstract

The invention relates to a plug-in type pressure-maintaining coring device suitable for soft formations and a method for using the same, comprising a coring device outer tube, a core tube, a penetration shoe, a flap valve, a pressure-maintaining inner tube, and a pressure-measuring and pressure-releasing interface Piston: The piston and flap valve are installed in the outer tube of the corer, the piston is connected with the outer tube of the corer through a pin, the upper end of the core tube is connected with the piston, and the penetration shoe is connected with the lower end of the core tube; The lower end is held against the valve seat, and the pressure-maintaining valve cover is limited in the annular space between the pressure-maintaining inner tube and the outer tube of the core remover. Under the action of external force, the inner tube can move to seal fit with the outer tube of the coring device; when the pressure-maintaining inner tube moves to a certain height, the flap valve is closed. This application utilizes hydraulically driven pistons to drive core pipes and penetration boots into soft formations to obtain pressure-holding cores; flow holes can effectively prevent damage to bottomhole tools; pressure measurement and pressure relief interfaces are convenient for pressure measurement and safe pressure relief , can improve safety performance.

Description

Plug-in pressure-holding coring device suitable for soft formation and its application method

technical field

The invention relates to the technical field of pressure-maintaining coring, in particular to a plug-in pressure-maintaining coring device suitable for soft formations and a use method thereof.

Background technique

Cores are important physical geological data for studying and understanding underground geology and mineral conditions.

It is necessary to select an appropriate amount of wells within the scope of the oil field, and drill a certain number of cores for the relevant oil and gas layers. Through observation, analysis and research, we can understand: ①The age, lithology, and sedimentary characteristics of the formation; ②The characteristics of the reservoir Physical and chemical properties and oil, gas and water conditions; ③ oil-generating layer characteristics and oil-generating indicators; ④ underground structure conditions (such as faults, joints, dip angles, etc.); ⑤ basic data for qualitative and quantitative interpretation of various logging methods; ⑥ The movement and distribution of oil, gas and water during the exploitation process, as well as the change of stratum structure; the rock core can also be used for indoor experimental analysis of water injection or various methods of enhancing recovery and increasing production and injection measures. It is an essential basic data for improving the water flooding development effect and recovery factor of reservoirs.

Core drilling refers to the drilling method in which the core is carved and taken out during drilling to study the underground geological conditions. Core drilling is usually rotary drilling, using drilling machinery to cut, grind, and break rocks in various ways, so that the drill bit continues to drill deep into the rock formation and carve cores.

However, the hardness of the target formation varies from soft to hard. For medium-hard or hard formations with uniform lithology and good columnarity, the current common method is to drive the drill bit forward with a hydraulic motor, and then pull out the core. For loose and soft formations, there are mainly mechanical pressurized coring, hydraulic pressurization coring and fully enclosed coring methods. Coring effect, ball valve pressure holding has the problem of small core diameter, and it is difficult to meet the current demand for coring without pressure holding.

Contents of the invention

In order to adapt to the acquisition of pressure-holding cores in soft formations, the present application provides a plug-in pressure-holding corer, which uses hydraulically driven pistons to drive core pipes and penetration shoes into soft formations, thereby obtaining pressure-holding cores.

The application is realized through the following technical solutions:

Plug-in pressure-holding corer for soft formations, including corer outer tube, core tube, penetration shoe, flap valve, pressure-holding inner tube and piston:

The outer tube of the core remover is provided with a lower limit structure for limiting the downward movement of the piston and a first upper limit structure for limiting the upward movement of the pressure-holding inner tube, and the first upper limit structure is located above the lower limit structure;

The piston is installed in the outer tube of the core remover, the piston has a first sealing ring, the piston and the outer tube of the core remover are connected together by pins, and the piston is provided with a connecting structure for connecting the pulling device;

The upper end of the core tube is connected with the piston, and the penetration shoe is connected with the lower end of the core tube;

The flap valve includes a valve seat and a pressure-holding bonnet. The valve seat is connected to the outer pipe of the core remover. One side of the pressure-holding bonnet is movably connected to the top side of the valve seat. Seat sealing surface;

The lower end of the pressure-maintaining inner tube is held against the valve seat, and the pressure-maintaining valve cover is limited in the annular space between the outer wall of the pressure-maintaining inner tube and the inner wall of the outer tube of the coring device. Intermittent or no spring; under the action of external force, the piston can pass through the valve seat and enter the pressure-maintaining inner tube and seal with the pressure-maintaining inner tube. The second upper limit of the pressure-maintaining inner tube is used to limit the upward movement of the piston Structure; under the action of external force, the pressure-holding inner tube can move to resist the first upper limit structure and seal with the outer tube of the core remover; when the pressure-holding inner tube moves to a certain height in the outer tube of the core remover, the The pressure bonnet loses its restriction and falls back to the top of the valve seat and fits tightly with the valve seat.

Optionally, the inner wall of the outer tube of the coring device is provided with a first shoulder to form the lower limit structure, the inner wall of the pressure-holding inner tube is provided with a second shoulder to form the second upper limit structure, and the inner wall of the outer tube of the corer is provided with a second upper limit structure. The third shoulder constitutes the first upper limit structure, the second shoulder is located above the first shoulder, and the third shoulder is located above the second shoulder.

Optionally, a second sealing ring is installed on the third shoulder, and when the upper end of the pressure-maintaining inner tube moves to abut against the third shoulder, the second sealing ring is used to realize the sealing between the two.

In particular, there is at least one flow hole passing through the inner and outer walls of the outer tube of the core remover, the flow hole is located above the lower limit structure, and the axial distance between the flow hole and the lower limit structure is greater than the axis of the piston. to the thickness.

Optionally, the outer tube of the coring device has an upper section of the outer tube and a lower section of the outer tube, and the lower end of the upper section of the outer tube is threadedly connected with the upper end of the lower section of the outer tube; the inner diameter of the upper section of the outer tube is larger than the diameter of the lower section of the outer tube, and the lower section of the outer tube can be sealed with the piston , the first shoulder, flow hole and pin hole are set on the lower section of the outer tube, the third shoulder is set on the upper section of the outer tube, and the pressure-holding inner tube is located in the upper section of the outer tube.

Optionally, the pressure-maintaining inner pipe has a first section, a second section and a third section manufactured integrally, the first section, the second section and the third section are connected in sequence, and the first section, the second section and the third section The diameters of the sections decrease successively, and the connection between the first section and the second section forms a second upper limit structure, and the second section can seal fit with the piston.

Optionally, there is a pressure measuring and releasing port on the piston, the pressure measuring and releasing port runs through the upper and lower surfaces of the piston, and a check valve is installed at the pressure measuring and releasing port. The one-way valve can choose the existing one-way valve.

In particular, the pressure measurement and pressure relief interface includes a valve cavity, a first hole and a second hole. The lower end of the first hole passes through the lower surface of the piston, the upper end of the first hole passes through the valve cavity, the upper end of the second hole passes through the upper surface of the piston, and the second hole passes through the upper surface of the piston. The lower end of the hole passes through the valve cavity;

The one-way valve includes a valve core and a second spring. The valve cavity is a stepped hole, and the valve core is adapted to the small hole of the valve cavity. in the large hole of the valve cavity; the valve core is located above the second spring, and under the action of the second spring, the valve core is installed in the small hole of the valve cavity and is held against the inner shoulder of the pressure measuring and pressure releasing interface.

In particular, the piston has the following two types: first, the diameter of the second hole is smaller than the diameter of the valve cavity, the diameter of the first hole is greater than or equal to the diameter of the valve cavity, and the second hole is equipped with an axial through hole The threaded head, the threaded head is threadedly connected with the first channel, the lower end of the second spring is held against the threaded head, and under the action of the second spring, the valve core is held against the shoulder at the junction of the second channel and the valve cavity; The one-way valve includes or does not include a valve stem adapted to the second hole, the valve stem is installed in the second hole, and the lower end of the valve stem is connected to the valve core;

The second type, the diameter of the first channel is smaller than the diameter of the valve cavity, the diameter of the second channel is greater than or equal to the diameter of the valve cavity, the second channel is equipped with a threaded head with an axial through hole, and the threaded head and the second channel thread connection, the lower end of the second spring bears against the inner shoulder at the connection between the first hole and the valve chamber, and under the action of the second spring, the valve core bears against the threaded head; the check valve includes or does not include the first The valve rod adapted to the two holes is installed in the axial through hole, and the lower end of the valve rod is connected with the valve core.

The method of using the plug-in pressure-holding coring device suitable for soft formations includes the following steps:

After lowering the coring tool to the target coring formation, inject drilling fluid, the drilling fluid has a tendency to drive the piston to move downward, and then cut the pin, after the pin is cut, the piston moves downward under the action of the drilling fluid, driving the core The pipe and the penetrating shoe perform a downward coring movement, and the obtained core enters the interior of the core pipe;

After the core completely enters the core tube, the lower end of the piston is also located on the lower limit structure of the outer tube of the corer. When the outer tube of the corer is provided with a flow hole, the drilling fluid flows out to the corer outside of the outer tube;

After the core completely enters the core tube, connect the piston at the wellhead through a pulling device;

The piston is pulled up by the pulling device, which drives the piston, core tube, penetration shoe and core to move upward, so that the core enters the pressure-holding inner tube, and the piston and the pressure-holding inner tube are sealed;

Continue to pull upwards to drive the pressure-holding inner tube to move upwards synchronously. The upper end of the pressure inner tube is sealed with the second sealing ring and the outer tube of the core remover; at the same time, the pressure-holding inner tube moves upward to cross the flap valve, and then provides space for the turning of the pressure-holding valve cover, and the pressure-holding valve cover is turned over The sealing of the lower end is completed until it is closed with the valve seat, thereby forming a pressure-holding space.

Compared with the prior art, the present application has the following beneficial effects:

1. This application uses a hydraulically driven piston to drive the core pipe and the penetration shoe to penetrate into the soft formation to obtain the pressure-holding core; the flap valve is used to realize the pressure-holding seal at the lower end, which can solve the problem of small core diameter caused by the ball valve ;

2. After the core enters the core tube, the flow hole is automatically opened, which can effectively avoid the damage to the bottom hole tools caused by the bottom hole pressure;

3. This application is equipped with a pressure measurement and pressure relief interface, which is convenient for pressure measurement and safe pressure relief, and can improve safety performance.

Description of drawings

The drawings described here are used to provide a further understanding of the embodiments of the present application, constitute a part of the application, and do not limit the embodiments of the present invention.

Fig. 1 is the structural representation of the plug-in type pressure-holding coring device under the initial state in the embodiment;

Fig. 2 is a partial enlarged view of place A in Fig. 1;

Fig. 3 is the structural representation when the flap valve and the pressure-holding inner pipe are installed in the outer pipe of the coring device in the embodiment;

Fig. 4 is the structural representation of pressure-holding inner pipe in the embodiment;

Fig. 5 is the structural representation of one-way valve and first kind of piston in the embodiment;

Fig. 6 is the structural representation of the first kind of piston in the embodiment;

Fig. 7 is the structural representation of check valve and second piston in the embodiment;

Fig. 8 is the structural representation of the second piston in the embodiment;

Fig. 9 is a schematic structural view of the plug-in pressure-holding coring device in the embodiment just when the rock core is obtained;

Fig. 10 is a schematic diagram of the structure when the lifting device is connected to the plug-in pressure-holding core remover in the embodiment;

Fig. 11 is the structural representation in the upward lifting process of piston and core pipe in the embodiment;

Fig. 12 is a structural schematic view of the embodiment when the pressure-holding inner tube is lifted to abut against the outer tube of the core remover.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments. Apparently, the described embodiments are some but not all of the embodiments of the present invention. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. It should be noted that each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. For the same and similar parts in each embodiment, refer to each other, that is, Can.

In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer" etc. is based on the orientation or positional relationship shown in the drawings, or the The orientation or positional relationship that is usually placed when the inventive product is used, or the orientation or positional relationship that is commonly understood by those skilled in the art, is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must be Having a particular orientation, being constructed and operating in a particular orientation, and therefore not to be construed as limiting the invention. In addition, the terms "first", "second", etc. are only used for distinguishing descriptions, and should not be construed as indicating or implying relative importance.

In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "installation", "installation", "connection" and "connection" should be understood in a broad sense, for example, it may be a fixed connection, It can also be a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

As shown in Figure 1, the plug-in type pressure-holding corer suitable for soft formations disclosed in this embodiment includes a corer outer tube 1, a core tube 2, a penetration shoe 3, a flap valve 4, and a pressure-holding inner tube. Tube 5 and piston 6.

The core tube 2, the pressure-holding inner tube 5 and the piston 6 are all located in the outer tube 1 of the coring device. The lower part of the pipe 2 is connected to the penetration shoe 3 .

The outer tube 1 of the core remover is provided with a lower limit structure for limiting the downward movement of the piston 6 and a first upper limit structure for limiting the upward movement of the pressure-maintaining inner tube 5, and the first upper limit structure is located above the lower limit structure. Under the action of external force, the pressure-maintaining inner tube 5 can move to abut against the first upper limit structure and seal fit with the core remover outer tube 1 . Under the action of external force, the piston 6 enters into the pressure-maintaining inner tube 5 and seals with the pressure-maintaining inner tube 5 . The second upper limit structure inside the pressure-maintaining inner tube 5 is used to limit the upward movement of the piston 6 .

As shown in Figure 2, the flap valve 4 includes a valve seat 41 and a pressure maintaining valve cover 42, the valve seat 41 is connected to the outer tube 1 of the core remover, and one side of the pressure maintaining valve cover 42 is movably connected to the top side of the valve seat 41. The top of the valve seat 41 has a valve seat sealing surface adapted to the pressure maintaining valve cover 42 . The valve seat 41 can be flipped and closed by its own weight, and a spring can also be added to provide trigger elastic force.

In a possible design, the flap valve 4 further includes a first spring 43 , and the first spring 43 is installed on the inner wall of the outer tube 1 of the core remover or in a groove on the outer surface of the pressure maintaining valve cover 42 . In a possible design, one side of the pressure maintaining valve cover 42 is hinged to the top of the valve seat 41, and a torsion spring is provided at the hinge.

As shown in Figure 1, in the initial state, the lower end of the pressure-maintaining inner tube 5 is held against the valve seat 41, and the pressure-maintaining inner tube 5 limits the pressure-maintaining valve cover 42 to the outer wall of the pressure-maintaining inner tube 5 and the outer tube 1 of the coring device. In the annular space of the inner wall, the pressure maintaining valve cover 42 is opened; the first spring 43 is compressed between the pressure maintaining valve cover 42 and the outer tube 1 of the core remover.

In the initial state, the piston 6 and the outer pipe 1 of the core remover are connected together by a pin 7; the piston 6 is located below the flap valve 4. There are pin holes 15 adapted to the pin 7 on the piston 6 and the coring device outer tube 1, and the pin 7 is radially installed in the pin hole 15.

It is worth noting that the number of pins 7 is reasonably set according to needs, and usually it is better to set two pins 7 symmetrically.

The inner wall of the outer tube 1 of the coring device is provided with a first shoulder 11 to form a lower limit structure, the inner wall of the pressure-holding inner tube 5 is provided with a second shoulder 51 to form a second upper limit structure, and the inner wall of the outer tube 1 of the corer is provided with a third shoulder 13 The first upper limit structure is formed, the second shoulder 51 is located above the first shoulder 11 , and the third shoulder 13 is located above the second shoulder 51 .

In a possible design, a second sealing ring 14 is installed on the third shoulder 13, and when the upper end of the pressure-maintaining inner tube 5 moves to abut against the third shoulder 13, the second sealing ring 14 is used to realize two the seal between them.

In a possible design, there is at least one flow hole 12 passing through the inner and outer walls of the outer tube 1 of the coring device, the flow hole 12 is located above the first shoulder 11, the flow hole 12 is connected to the first The axial distance of the shoulder 11 is greater than the axial thickness of the piston 6 .

It is worth noting that the number of flow holes 12 is reasonably set according to needs, and it is generally appropriate to arrange at least two flow holes 12 at equal intervals in the circumferential direction.

In a possible design, as shown in FIG. 3 , the outer tube 1 of the core remover has an upper section 101 of the outer tube and a lower section 102 of the outer tube, and the lower end of the upper section 101 of the outer tube is screwed to the upper end of the lower section 102 of the outer tube. The inner diameter of the upper section 101 of the outer tube is greater than the diameter of the lower section 102 of the outer tube. The lower section 102 of the outer tube can be sealed with the piston 6. The first shoulder 11, the flow hole 12 and the pin hole 15 are arranged on the lower section 102 of the outer tube. The third The shoulder 13 is arranged on the upper section 101 of the outer tube, and the pressure-maintaining inner tube 5 is located in the upper section 101 of the outer tube.

In a possible design, as shown in Fig. 4, the pressure-holding inner tube 5 has a first segment 501, a second segment 502 and a third segment 503 made integrally, and the first segment 501, the second segment 502 and the third segment The sections 503 are connected sequentially, the diameters of the first section 501, the second section 502 and the third section 503 are successively reduced, and the connection between the first section 501 and the second section 502 forms a second shoulder 51, and the second section 502 can be connected with The piston 6 is tightly matched to form the sealing section of the pressure-maintaining inner tube 5 .

In a possible design, as shown in FIGS. 5-8 , the outer wall of the piston 6 has an annular groove, and a first sealing ring 61 is installed in the annular groove. There is a pressure measuring and releasing port on the piston 6, and the pressure measuring and releasing port runs through the upper and lower surfaces of the piston 6, and a check valve 8 is installed at the pressure measuring and releasing port. In particular, the pressure measurement and relief interface includes a valve chamber 62, a first hole 63 and a second hole 64, the lower end of the first hole 63 passes through the lower surface of the piston 6, the upper end of the first hole 63 passes through the valve chamber 62, and the upper end of the second hole 64 Through the upper surface of the piston 6 , the lower end of the second hole 64 passes through the valve chamber 62 . The one-way valve 8 includes a spool 81 and a second spring 82. The valve cavity 62 is a stepped hole. The spool 81 is installed in the small hole of the valve cavity 62 and is sealed with the hole wall through the spool sealing ring. The spool 81 second The spring 82 is installed in the large hole of the valve cavity 62 . The spool 81 is located above the second spring 82 , under the action of the second spring 82 , the spool 81 is installed in the small hole of the valve chamber 62 and abuts against the inner shoulder of the pressure measuring and releasing interface.

In order to facilitate the installation of the one-way valve 8, two structures of the piston 6 are provided in this embodiment. The first kind, as shown in Figure 5 and Figure 6, the diameter of the second hole 64 is smaller than the diameter of the valve cavity 62, the diameter of the first hole 63 is greater than or equal to the diameter of the valve cavity 62, and the second hole 64 is equipped with a shaft To the threaded head 63 of the through hole 66, the threaded head 63 is threadedly connected with the first channel 63, the lower end of the second spring 82 is held against the threaded head 63, and under the action of the second spring 82, the spool 81 is held against the second On the shoulder at the junction of the hole 64 and the valve cavity 62 . In particular, the one-way valve 8 further includes a valve stem 83 adapted to the second hole 64 , the valve stem 83 is installed in the second hole 64 , and the lower end of the valve stem 83 is connected to the valve core 81 . In particular, the valve stem 83 is integrally manufactured with the valve core 81 .

The second kind, as shown in Figure 7 and Figure 8, the diameter of the first port 63 is smaller than the diameter of the valve chamber 62, the diameter of the second port 64 is greater than or equal to the diameter of the valve chamber 62, and the second port 64 is equipped with a shaft To the threaded head 63 of the through hole 66, the threaded head 63 is threadedly connected with the second channel 64, and the lower end of the second spring 82 bears on the inner shoulder of the connection between the first channel 63 and the valve chamber 62, and the second spring 82 Under the action of the spool 81 against the threaded head 63 . In particular, the one-way valve 8 further includes a valve stem 83 adapted to the second hole 64 , the valve stem 83 is installed in the axial through hole 66 , and the lower end of the valve stem 83 is connected to the valve core 81 .

In a possible design, the penetration shoe 3 is a conical barrel, and its large end is fixedly connected to the lower end of the core tube 2 .

The piston 6 is provided with a connecting structure for connecting the pulling device, so as to pull the piston 6 and the core pipe 2 upwards. In a possible design, the top of the piston 6 is provided with a spearhead 9, and the lifting device can choose a wire rope 91 and an overshot 92, which is a conventional technology in the art and will not be repeated here.

How to use the plug-in pressure-holding core remover:

Before coring, the pin 7 connects the piston 6 with the outer tube 1 of the coring device, as shown in Figure 1;

After the coring device is lowered to the target coring formation, the drilling fluid is introduced. The drilling fluid tends to drive the piston 6 to move downward, and then cut the pin 7. After the pin 7 is cut, the piston 6 moves downward under the action of the drilling fluid. , driving the core tube 2 and the penetration shoe 3 to perform a downward coring movement, and the obtained core enters the inside of the core tube 2;

After the rock core has completely entered the core tube 2, the lower end of the piston 6 is also located on the first shoulder 11 of the outer tube 1 of the coring device. At this time, the flow hole 12 is opened, and the drilling fluid flows out through the flow hole 12 to the core. The outside of the outer tube 1 of the device prevents pressure from being suppressed and avoids damage to the core remover, as shown in Figure 9;

After the rock core has completely entered the core pipe 2, the overshot 92 is put into the wellhead through the steel wire rope 91, and the overshot 92 is connected with the spear head 9, as shown in Figure 10;

Pull the wire rope 91 to drive the piston 6, the rock core pipe 2, and the rock core to move upwards, so that the rock core enters the pressure-holding inner pipe 5, and the first sealing ring 41 of the piston 6 enters the sealing section of the pressure-holding inner pipe 5 for sealing. As shown in Figure 11;

Continue to pull the steel wire rope 91 to drive the pressure-maintaining inner tube 5 to move upward synchronously, the upper end of the pressure-maintaining inner tube 5 is located on the third shoulder 13 of the outer tube 1 of the core remover, and the upper end of the pressure-maintaining inner tube 5 relies on the second sealing ring 14 Seal with the outer tube 1 of the core remover; at the same time, the pressure-holding inner tube 5 moves upward to cross the flap valve 4, and then provides space for the turning of the pressure-holding valve cover 42. Under the action of the first spring 43, the pressure-holding The valve cover 42 is turned over to close with the valve seat 1 to complete the sealing of the lower end, thereby forming a pressure-holding space, as shown in Figure 12;

After the core remover is lifted from the bottom of the well to the surface, the pressure measurement and pressure relief interface and the one-way valve 8 provided on the piston 6 can be used to complete the measurement of the internal pressure of the core pipe 2, and pass the measurement before taking out the core. The pressure relief interface is used for pressure relief to ensure the safety of operation. The specific operation is as follows: connect an external pressure measuring element or a pressure relief mechanism to the pressure measuring and pressure relief interface, push the spool 81 down to compress the second spring 82, and the spool sealing ring on the spool 81 loses the sealing effect, so that the core tube 2 The internal pressure can be measured or unloaded through this interface.

This application can maintain pressure to obtain rock cores in soft formations. By setting up a pressure measurement and pressure relief interface on the piston, the internal pressure of the core tube can be measured through this channel, and the pressure can be unloaded through this channel to prevent pressure operation. Can effectively improve security.

The above specific implementations have further described the purpose, technical solutions and beneficial effects of the application in detail. It should be understood that the above are only specific implementations of the present invention, and are not used to limit the protection scope of the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (11)

1. The plug-in pressure-holding coring device suitable for soft formations is characterized in that it includes: The outer tube (1) of the core remover is provided with a lower limit structure for limiting the downward movement of the piston (6) and a first upper limit structure for limiting the upward movement of the pressure-holding inner tube (5). The first upper limit structure is located at Above the lower limit structure; The piston (6) is installed in the outer tube (1) of the coring device, the piston (6) has a first sealing ring (61), and the pin (7) is passed between the piston (6) and the outer tube (1) of the coring device connected together, the piston (6) is provided with a connecting structure for connecting the lifting device; The core pipe (2), the upper end is connected with the piston (6); The penetration shoe (3) is connected with the lower end of the core pipe (2); The flap valve (4) includes a valve seat (41) and a pressure-holding valve cover (42). (41) One side of the top is flexibly connected, and the top of the valve seat (41) has a valve seat sealing surface that is compatible with the pressure-maintaining valve cover (42); The lower end of the pressure-maintaining inner tube (5) is held against the valve seat (41), and the pressure-maintaining valve cover (42) is limited between the outer wall of the pressure-maintaining inner tube (5) and the inner wall of the corer outer tube (1) in the ring; Under the action of external force, the piston (6) can pass through the valve seat (41) and enter the pressure-maintaining inner tube (5) to seal fit with the pressure-maintaining inner tube (5). The second upper limit structure that restricts the upward movement of the piston (6); the pressure-holding inner tube (5) can move to resist the first upper limit structure under the action of external force and seal with the core remover outer tube (1) Cooperate; When the pressure-holding inner tube (5) moves to a certain height in the core remover outer tube (1), the pressure-holding valve cover (42) loses its restriction and falls back to the top of the valve seat (41) and seals with the valve seat (41) . 2. The plug-in type pressure-maintaining corer suitable for soft formations according to claim 1, characterized in that: the inner wall of the outer tube (1) of the corer is provided with a first shoulder (11) to form the lower limit position structure, the inner wall of the pressure-holding inner tube (5) is provided with a second shoulder (51) to form the second upper limit structure, and the inner wall of the outer tube (1) of the core remover is provided with a third shoulder (13) to form the first upper limit bit structure, the second shoulder (51) is located above the first shoulder (11), and the third shoulder (13) is located above the second shoulder (51). 3. The plug-in type pressure-maintaining coring device suitable for soft formations according to claim 1, characterized in that a spring is provided between the pressure-maintaining valve cover (42) and the outer tube (1) of the coring device. 4. The plug-in type pressure-holding corer suitable for soft formations according to claim 2, characterized in that: a second sealing ring (14) is installed on the third shoulder (13), when the pressure-holding inner tube ( 5) When the upper end moves to abut against the third shoulder (13), the second sealing ring (14) realizes the sealing between the two. 5. The plug-in type pressure-holding core remover suitable for soft formations according to any one of claims 1-4, characterized in that: there is at least one through wall of the outer pipe (1) of the core remover The flow hole (12) on the inner and outer walls is located above the lower limit structure, and the axial distance between the flow hole (12) and the lower limit structure is greater than the axial thickness of the piston (6). 6. The plug-in type pressure-maintaining corer suitable for soft formations according to claim 2, characterized in that: the outer tube (1) of the corer has an upper section (101) and a lower section (102) of the outer tube, the outer tube The lower end of the upper section of the pipe (101) is threadedly connected with the upper end of the lower section of the outer pipe (102); The inner diameter of the upper section of the outer tube (101) is greater than the diameter of the lower section of the outer tube (102), and the lower section of the outer tube (102) can be sealed with the piston (6). The first shoulder (11), the flow hole (12) and the pin hole (15) is set on the lower section of the outer tube (102), the third shoulder (13) is set on the upper section of the outer tube (101), and the pressure-maintaining inner tube (5) is located in the upper section of the outer tube (101). 7. The plug-in type pressure-holding core remover suitable for soft formations according to claim 1 or 6, characterized in that: the pressure-holding inner pipe (5) has a first section (501) made integrally, a second section paragraph (502) and the third paragraph (503), the first paragraph (501), the second paragraph (502) and the third paragraph (503) are sequentially connected, the first paragraph (501), the second paragraph (502) and the The diameters of the three sections (503) decrease sequentially, and the connection between the first section (501) and the second section (502) forms a second upper limit structure, and the second section (502) can seal fit with the piston (6). 8. The plug-in type pressure-maintaining coring device suitable for soft formations according to claim 1, characterized in that: the piston (6) has a pressure measurement and pressure relief interface, and the pressure measurement and pressure relief interface runs through the piston (6) On the upper and lower surfaces, a check valve (8) is installed at the pressure measurement and pressure relief interface. 9. The plug-in type pressure-holding coring tool suitable for soft formations according to claim 8, characterized in that: the pressure measurement and pressure relief interface includes a valve cavity (62), a first hole (63) and a second hole (64), the lower end of the first hole (63) passes through the lower surface of the piston (6), the upper end of the first hole (63) passes through the valve chamber (62), and the upper end of the second hole (64) passes through the upper surface of the piston (6), The lower end of the second channel (64) passes through the valve chamber (62); The one-way valve (8) includes a valve core (81) and a second spring (82), the valve cavity (62) is a stepped hole, the valve core (81) is adapted to the small hole of the valve cavity (62), and the valve core (81) is provided with a spool sealing ring for sealing cooperation with the hole wall, and the second spring (82) is installed in the large hole of the valve chamber (62); The spool (81) is located above the second spring (82). Under the action of the second spring (82), the spool (81) is installed in the small hole of the valve chamber (62) and is held against the pressure measuring and releasing port. on the inner shoulder of the 10. The plug-in pressure-holding coring device suitable for soft formations according to claim 9, characterized in that: the piston (6) has the following two types: In the first type, the diameter of the second hole (64) is smaller than the diameter of the valve cavity (62), the diameter of the first hole (63) is greater than or equal to the diameter of the valve cavity (62), and the second hole (64) is equipped with a device The threaded head (63) of the axial through hole (66), the threaded head (63) is threadedly connected with the first channel (63), the lower end of the second spring (82) is against the threaded head (63), and the second spring Under the action of (82), the spool (81) bears on the shoulder at the junction of the second hole (64) and the valve chamber (62); the one-way valve (8) includes a The valve stem (83), the valve stem (83) is installed in the second hole (64), and the lower end of the valve stem (83) is connected with the valve core (81); In the second type, the diameter of the first hole (63) is smaller than the diameter of the valve cavity (62), the diameter of the second hole (64) is greater than or equal to the diameter of the valve cavity (62), and the second hole (64) is equipped with a device The threaded head (63) of the axial through hole (66), the threaded head (63) is threadedly connected with the second hole (64), and the lower end of the second spring (82) resists between the first hole (63) and the valve cavity (62 ) on the inner shoulder of the joint, under the action of the second spring (82), the spool (81) is held against the threaded head (63); the one-way valve (8) includes a The matching valve stem (83), the valve stem (83) is contained in the axial through hole (66), and the valve stem (83) lower end is connected with the valve core (81). 11. The method for using the plug-in pressure-holding core remover suitable for soft formations according to any one of claims 1-10, characterized in that it comprises the following steps: After the coring tool is lowered to the target coring formation, the drilling fluid is injected, and the drilling fluid tends to drive the piston (6) to move downward, and then cut off the pin (7). After the pin (7) is cut, the piston (6) Under the action of the drilling fluid, it moves downward, driving the core tube (2) and the penetration shoe (3) to move downward for coring, and the obtained core enters the inside of the core tube (2); After the core completely enters the core tube (2), the lower end of the piston (6) is also located on the lower limit structure of the outer tube (1) of the coring device. 12), the drilling fluid flows out through the flow hole (12) to the outside of the outer tube (1) of the core remover; After the core completely enters the core tube (2), connect the piston (6) at the wellhead through a pulling device; The piston (6) is pulled upward by the pulling device, which drives the piston (6), core tube (2), penetration shoe (3) and core to move upward, so that the core enters the pressure-holding inner tube (5), and the piston (6) Sealed with the pressure-holding inner tube (5); Continue to pull upwards to drive the pressure-holding inner tube (5) to move upward synchronously. On the second upper limit structure of the pressure inner tube (5), the upper end of the pressure keeping inner tube (5) is sealed with the second sealing ring (14) and the outer tube (1) of the core remover; at the same time, the pressure keeping inner tube (5) Move upward to cross the flap valve (4), and then provide space for the overturning of the pressure maintaining valve cover (42), and the pressure maintaining valve cover (42) is overturned to close with the valve seat (1) to complete the sealing of the lower end, thereby Form a holding space.

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