A downhole pvt sampler

Abstract

The application discloses a downhole PVT sampler, which comprises a sampling cylinder and valve assemblies sealingly connected to two ends of the sampling cylinder, a locking connecting rod is arranged in the sampling cylinder, the locking connecting rod is connected with the lower valve assembly through an expansion type self-locking device, when the self-locking device is in a locking state, the sampling cylinder is communicated with the two valve assemblies, so that liquid can enter the sampling cylinder, when the self-locking device is unlocked, the two valve assemblies are closed, the sampling cylinder is in a sealed state, and sampling is completed, the sampler has simple structure and convenient sampling, the sealing structure between the sampling cylinder body and the valve joint and the sampling cylinder is changed, so that the sampler has higher pressure bearing capacity and good sealing performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of downhole PVT sampling downhole device, specifically to a downhole PVT sampler. BACKGROUND

[0002] Oil and gas reservoir fluid high pressure physical property (PVT) parameters have a wide range of uses, and are the basis for studying oilfield driving types, determining oilfield development methods, calculating oil and gas field reserves, and selecting oil and gas well work systems, and are of great significance for correctly understanding and evaluating oil and gas fields. Therefore, downhole PVT sampling analysis plays a crucial role in oilfield development and application. At present, there are more and more high-temperature, high-pressure, and ultra-deep wells (referred to as "three super wells"). The downhole pressure of such wells is as high as 120 MPa, the downhole temperature is as high as 180 DEG C, the well depth is more than 6000 meters, and some wells also contain corrosive media such as carbon dioxide or hydrogen sulfide. Downhole sampling becomes very difficult. According to the investigation, it is found that the PVT sampler currently used by the cable downhole sampling method has the highest pressure resistance of 103 MPa and the highest temperature resistance of 180 DEG C. At present, due to the limitations of the structure of the sampling cylinder, the sealing structure, the sealing method, and the buckle type, the pressure-bearing capacity of the sampler cannot meet the sampling needs of "three super wells" (the highest pressure is more than 120 MPa) without significantly increasing the outer diameter of the sampler.

[0003] At present, the sample analysis of high-temperature and high-pressure wells is basically carried out by sampling at the ground wellhead or the separator. The analysis results cannot ensure that the sample truly represents the content and properties of the formation oil and gas components. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a downhole PVT sampler, which can meet the sampling needs of high-temperature and high-pressure wells such as "three super wells" and solve the downhole PVT sampling problem of high-temperature and high-pressure wells.

[0005] The present application is realized by the following technical solutions:

[0006] A downhole PVT sampler comprises a sampling cylinder, the two ends of which are respectively sealed and connected with valve assemblies, and the two valve assemblies are arranged symmetrically along the axial center of the sampling cylinder;

[0007] A locking link is coaxially arranged in the sampling cylinder, the upper end of the locking link is connected with the sealing structure of the first valve assembly, the lower end of the locking link is provided with an expansion self-locking device, the expansion self-locking device is connected with the sealing structure of the second valve assembly, and when the expansion self-locking device is separated from the sealing structure of the second valve assembly, the two sealing structures seal the sampling cylinder.

[0008] Preferably, the self-locking device comprises an expansion locking mechanism, a convex ring and a locking needle, the convex ring is arranged at the lower end of the inner wall of the sampling cylinder, the expansion locking mechanism is connected with the lower end of the locking connecting rod, and the locking needle is arranged at the top of the sealing structure of the second valve assembly;

[0009] When the locking needle is inserted into the expansion locking mechanism, the expansion locking mechanism is buckled with the convex ring, and the sampling cylinder is in a conductive state; when the locking needle is separated from the expansion locking mechanism, the two sealing structures are reversely moved to seal the sampling cylinder.

[0010] Preferably, the expansion locking mechanism comprises a fixed base and a limiting plate, the top of the fixed plate is connected with the lower end of the locking connecting rod, and a plurality of limiting plates are circumferentially and interval arranged at the bottom edge of the fixed plate and extend downward, the bottom of the outer wall of the limiting plate is provided with an outwardly extending positioning block, and a positioning hole of the limiting plate is used for buckling with the lower end of the convex ring when the limiting plate is deformed.

[0011] Preferably, the fixed base is connected with the lower end of the locking connecting rod through an adjusting rod, and the adjusting rod is used for adjusting the axial position of the expansion locking mechanism.

[0012] Preferably, the valve assembly comprises a shell, a return spring assembly and a sealing structure.

[0013] The end of the shell is provided with a sealing pipe, the shell is fixedly connected with the end of the sampling cylinder, the sealing pipe is located in the sampling cylinder and is sealingly connected, the return spring assembly is arranged in the shell, the sealing structure is arranged at the end of the sealing pipe, the return spring assembly is connected with the sealing structure, and the working state of the sealing structure is controlled through the elastic force; when the sealing structure is opened, the valve assembly is communicated with the sampling cylinder.

[0014] Preferably, a plurality of sealing rings are arranged between the sealing pipe and the sampling cylinder, and the shell and the sampling cylinder are connected through threads.

[0015] Preferably, the sealing structure comprises a tapered groove and a tapered sealing block matched with the tapered groove, and the return spring assembly comprises a spring and a pull rod.

[0016] The tapered groove is arranged at the end of the sealing pipe, the spring is arranged in the shell, one end of the pull rod is connected with the spring, and the other end of the pull rod extends into the sampling cylinder and is connected with the tapered sealing block; when the spring is compressed, the tapered groove is separated from the tapered sealing block.

[0017] Preferably, a fluid outlet is arranged on the first valve assembly, and a fluid inlet is arranged on the second valve assembly.

[0018] Preferably, the upper end of the first valve assembly is connected with a jar, and the lower end of the second valve assembly is connected with a control device.

[0019] Preferably, the control device is a clock control mechanism, a wall-mounted control mechanism or a shear pin control mechanism.

[0020] Compared with the prior art, the present application has the following beneficial technical effects:

[0021] The present application provides a downhole PVT sampler, comprising a sampling cylinder and a valve assembly sealingly connected at both ends thereof, a locking connecting rod is arranged in the sampling cylinder, the locking connecting rod is connected with the lower valve assembly through an expansion self-locking device, when the self-locking device is in a locking state, the sampling cylinder is communicated with the two valve assemblies, so that liquid can enter the sampling cylinder, when the self-locking device is unlocked, the two valve assemblies are closed to make the sampling cylinder in a sealed state to complete sampling, the sampler is simple in structure and convenient for sampling, the expansion self-locking device improves the pressure-bearing capacity of the sampling cylinder without increasing the sampling cylinder, through factory test, under the condition that the outer diameter of the sampling cylinder is 48 mm, nitrogen, water and hydraulic oil are used for sealing and pressure-bearing test, the highest pressure-bearing capacity reaches 160 MPa, the highest temperature is 200 ℃, under the ground environmental condition, the fluid is placed in the sampling cylinder for seven days without leakage. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a sectional view of the sampler of the present application in an open state;

[0023] Figure 2 is a sectional view of the sampler of the present application in a closed state;

[0024] Figure 3 is a schematic view of the body structure of the sampling cylinder of the present application;

[0025] Figure 4 is a schematic view of the valve joint structure of the present application.

[0026] In the drawing: control mechanism 1, lower valve assembly 2, sampling cylinder 3, upper valve assembly 4, coupling head 5, positioning pin 6, pin needle 7, fluid inlet 8, ejector pin 9, lower return spring assembly 10, lower sealing ring 11, locking connecting rod 12, upper sealing ring 13, upper return spring assembly 14, stirring block 15, fluid outlet 16, sealing surface 17, convex ring 18, thread 19, locking block 20. DETAILED DESCRIPTION

[0027] The present application will be further described in detail below in combination with the drawings, which is an explanation of the present application rather than a limitation.

[0028] Reference Figures 1-4 is a downhole PVT sampler, comprising a control mechanism 1, a lower valve assembly 2, a sampling cylinder 3 and an upper valve assembly 4, the upper valve assembly 4 and the lower valve assembly 2 are sealingly connected at both ends of the sampling cylinder 3 respectively, and the upper valve assembly 4 is connected with a coupling head 5.

[0029] A locking link 12 is coaxially arranged in the sampling cylinder 3. The upper end of the locking link 12 is connected with the sealing structure of the upper valve assembly 4. The lower part of the locking link 12 is provided with a stirring block 15. The lower end of the locking link 12 is provided with a self-locking device which is connected with the sealing structure of the lower valve assembly 2. When the self-locking device is separated from the sealing structure, the two sealing structures seal the liquid inlet and liquid outlet of the sampling cylinder 3 respectively.

[0030] The self-locking device comprises an expansion locking mechanism, a convex ring 18 and a locking pin. The convex ring is arranged at the lower end of the inner wall of the sampling cylinder 3. The expansion locking mechanism is connected with the lower end of the locking link. The locking pin is arranged at the top of the sealing structure of the lower valve assembly 2. Before sampling, the expansion locking mechanism is located in the area of the convex ring, and the locking pin is inserted into the expansion locking mechanism, so that the expansion locking mechanism and the convex ring 18 are locked with each other. After sampling, the locking pin is separated from the expansion locking mechanism, and the sealing structures of the two valve assemblies are moved reversely to seal the liquid inlet and liquid outlet of the sampling cylinder 3.

[0031] The expansion locking mechanism is a locking block 20 which comprises a fixed base and a limiting block, and an adjusting rod. The lower end of the adjusting rod is connected with the fixed base. The adjusting rod is connected with the locking link through threads, for adjusting the position of the locking block, so that it is better coupled with the convex ring inside the sampling cylinder.

[0032] The upper end of the adjusting rod is connected with the lower end of the locking link. The limiting block is a semicircular structure. The upper end of the limiting block is hinged with the fixed plate through a pin. The two limiting blocks are symmetrically arranged, and the inner concave arc surfaces are oppositely arranged. A V-shaped guide angle is arranged on the inner wall of the limiting block. The lower end of the outer wall of the limiting plate is provided with a positioning block. Before sampling, the locking block is moved to the position of the convex ring, and at the same time, the positioning block is located at the lower end of the convex ring. When the locking pin is inserted between the two limiting plates, the two limiting plates are opened outward, and at the same time, the positioning block is buckled with the lower end of the convex ring. At this time, the liquid inlet and liquid outlet of the sampling cylinder 3 are in communication.

[0033] The upper valve assembly 4 and the lower valve assembly 2 are the same structure and symmetrically arranged at the two ends of the sampling cylinder. The valve assembly comprises a shell, a return spring assembly and a sealing structure.

[0034] The shell is a hollow structure, one end of the shell is connected with the end of the sampling cylinder 3 through thread 19, the connecting end of the shell and the sampling cylinder is provided with a sealing tube, the sealing tube extends into the sampling cylinder, a sealing ring is arranged between the sealing surface 17 between the sealing tube and the sampling cylinder, the sealing structure comprises a taper groove and a tapered sealing block, the return spring assembly comprises a spring and a pull rod, the taper groove is arranged at the end of the sealing tube, the small end of the taper groove is located in the interior of the sealing tube, the spring is arranged in the shell, the shoulder in the shell limits the spring, one end of the pull rod is connected with the spring, the other end of the pull rod extends into the sampling cylinder 3, the tapered sealing block is arranged at the end of the pull rod and can cooperate with the taper groove to seal by the elastic force, and a sealing ring is arranged between the tapered sealing block and the taper groove.

[0035] In the embodiment, the shell of the upper valve assembly 4 is provided with a fluid outlet 16, the shell of the upper valve assembly 4 is provided with an upper return spring assembly 14, the tapered sealing block of the upper valve assembly 4 is connected with the upper end of the locking connecting rod 12, and an upper sealing ring 13 is arranged between the tapered sealing block and the taper groove, the upper end of the shell is connected with the coupling head 5, and the coupling head 5 is used for connecting the jar.

[0036] The shell of the lower valve assembly 2 is provided with a fluid inlet 8, the shell of the lower valve assembly 2 is provided with a lower return spring assembly 10, the tapered sealing block of the lower valve assembly 2 is connected with the lower end of the locking needle, and a lower sealing ring 11 is arranged between the tapered sealing block and the taper groove, and the lower end of the shell is connected with the control mechanism 1.

[0037] The control mechanism 1 comprises a control shell, the upper end of the control shell is connected with the shell of the lower valve assembly through thread, the control shell is provided with a thimble 9, the upper end of the thimble 9 is connected with the lower end of the spring of the lower valve assembly 2, the lower end of the thimble 9 is connected with the counterweight rod through the pin needle 7, the lower end of the counterweight rod is located outside the control shell and is connected with the connecting piece, and the lower part of the counterweight rod is connected with the lower end of the control shell through the positioning pin 6.

[0038] The working principle of the downhole PVT sampler provided by the application will be described in detail below.

[0039] Referring to Figure 1 The figure is the structure of the sampler before sampling, the upper valve assembly 4 and the lower valve assembly 2 are symmetrically arranged at the two ends of the sampling cylinder, the upper end of the upper valve assembly 4 is connected with the jar through the coupling head 5, and the lower valve assembly 2 is connected with the control device through the positioning pin 6 and the pin needle 7.

[0040] Before sampling, the positioning block of the locking block 20 is clamped with the lower end of the convex ring, the locking needle is inserted into the locking block 20, the spring of the lower valve assembly 2 is in a compressed state, and the tapered groove is separated from the tapered sealing block, that is, the fluid inlet 8 on the shell of the lower valve assembly 2 is communicated with the sampling cylinder, and since the locking block 20 is clamped with the convex ring, the spring of the upper valve assembly 4 is compressed by the locking connecting rod 12 at the same time, and the tapered groove of the upper valve assembly 4 is separated from the tapered sealing block, so that the sampling cylinder is communicated with the fluid outlet 16 on the upper valve assembly 4.

[0041] During sampling, the communication of the sampler is checked by blowing, then the sampler is pulled into the top of the blowout preventer and fixed with the downhole wire, and after the well opening pressure test is qualified, the sampler is lowered, and during the lowering of the sampler into the well, the lowering speed is slowed down at the variable diameter place, and the control device pin cannot be cut off in advance due to impact on the bottom of the sampler. After the sampler is lowered to the predetermined position in the well, the fluid enters the sampling cylinder through the fluid inlet, then the variable diameter or other positioning device is struck downward, the control device pin is cut off, the sampler is closed, and the sampling is successful.

[0042] Referring to Figure 2 After sampling, the pins 6 and 7 of the control device are cut off under the action of gravity acceleration and the jar, the ejector pin 9 is ejected and falls to the limiting step under the action of the spring of the lower valve assembly 2, the sealing structure of the lower valve is sealed under the action of the spring, the sampling cylinder is blocked with the fluid inlet 8, the locking needle is separated from the locking block 20, the locking block is contracted, the positioning connecting rod 12 moves upward under the action of the spring of the upper valve, the sealing structure of the upper valve is sealed, the sampling cylinder is blocked with the fluid outlet 16, the sampling of the sample in the well is completed, and as the tool is pulled up, the pressure in the sampling cylinder is greater than the pressure in the well, the upper and lower valves are pressed more tightly, a good sealing effect is achieved, the fluid is locked in the sampling cylinder, and the fluid at the predetermined depth in the well is taken out with the sampler, and the qualified sample is taken in the sealed state.

[0043] The downhole PVT sampling device of the present application sets a sealing pipe at the end of the housing of the valve assembly, and then threadedly connects the housing of the valve assembly with the sampling pipe, and then sets a sealing ring between the inner wall of the sealing pipe and the sampling pipe, and changes the existing outer sealing to inner sealing, and sets the sealing device at the end of the threaded section, and seals inside the sampling cylinder, and the current market samplers basically set a sealing O-ring at the root of the connection, which causes the outer cylinder wall thickness to be thin, and in the case of not greatly increasing the outer diameter, the pressure bearing capacity of the sample cylinder cannot be guaranteed.

[0044] The valve joint structure design is different from other samplers, and the upper and lower valves and the sampling cylinder body are sealed by a sealing pipe, which reduces the external thrust received by the thread and increases the pressure bearing capacity of the sampler; the current market samplers use a threaded connection to compress the sealing ring, which increases the external thrust received by the thread.

[0045] A convex ring with a length of about 150mm is designed inside the sampling cylinder close to the lower valve sealing part, the convex ring and the maximum inner diameter of the sampling cylinder differ by 2mm on one side, the locking limit plate and locking needle of the locking connecting rod are used to achieve the purpose of controlling the opening and closing of the upper and lower valves, and the wall thickness of the sample cylinder is guaranteed, and the pressure bearing capacity is increased; the sealing between the sampling cylinder and the valve joint is inside the cylinder body, and after the valve is closed, the connecting thread will not be immersed in the fluid inside the cylinder.

[0046] The sampler of the present application can be used with a clock control mechanism, a wall-mounted control mechanism and a shear pin type control mechanism, and can be selectively used according to different well conditions, and at present, the shear pin type control mechanism is used in conjunction with in the "three super wells" with high temperature and high pressure.

[0047] The downhole PVT sampler for high temperature and high pressure wells of the present application can obtain "real" fluid of gas reservoirs according to the sampling requirements of Bozi and DaBei oil and gas regions, and can carry out researches on phase characteristics of different condensate oil content and different wax content condensate gas reservoirs, wax deposition experiments and wellbore wax deposition theoretical models, form a sampling specification suitable for condensate gas reservoirs in the Bozi-Dabei region, complete the understanding of plane phase distribution law and wax precipitation law, establish a gas well wellbore wax precipitation phase theory model, and provide support for the development of high wax condensate gas reservoirs.

[0048] The above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A downhole PVT sampler characterized by, The sampling cylinder (3) is connected with two valve assemblies at both ends, and the two valve assemblies are arranged symmetrically along the axial center of the sampling cylinder; A locking connecting rod (12) is arranged coaxially in the sampling cylinder (3), the upper end of the locking connecting rod (12) is connected with the sealing structure of the first valve assembly, the lower end of the locking connecting rod (12) is provided with an expansion type self-locking device, the expansion type self-locking device is connected with the sealing structure of the second valve assembly, when the expansion type self-locking device is separated from the sealing structure of the second valve assembly, the two sealing structures seal the sampling cylinder (3). The locking device comprises an expansion type locking mechanism, a convex ring (18) and a locking needle, the convex ring is arranged at the lower end of the inner wall of the sampling cylinder (3), the expansion type locking mechanism is connected with the lower end of the locking connecting rod, and the locking needle is arranged at the top of the sealing structure of the second valve assembly (2). When the locking needle is inserted into the expansion type locking mechanism, the expansion type locking mechanism is buckled with the convex ring (18), and the sampling cylinder is in a conductive state, when the locking needle is separated from the expansion type locking mechanism, the two sealing structures move reversely to seal the sampling cylinder (3). The expansion type locking mechanism comprises a fixed base and a limiting plate, the top of the fixed plate is connected with the lower end of the locking connecting rod, a plurality of limiting plates are arranged circumferentially and spaced apart at the bottom edge of the fixed plate and extend downward, the bottom of the outer wall of the limiting plate is provided with a positioning block extending outward, and a positioning hole is arranged in the limiting plate for buckling with the lower end of the convex ring when the limiting plate is deformed. The fixed base is connected with the lower end of the locking connecting rod through an adjusting rod, and the adjusting rod is used for adjusting the axial position of the expansion type locking mechanism.

2. A downhole PVT sampler according to claim 1, wherein, The valve assembly comprises a shell, a return spring assembly and a sealing structure; The end of the shell is provided with a sealing pipe, the shell is fixedly connected with the end of the sampling cylinder, the sealing pipe is located in the sampling cylinder (3) and is sealingly connected, the return spring assembly is arranged in the shell, the sealing structure is arranged at the end of the sealing pipe, the return spring assembly is connected with the sealing structure, and the working state of the sealing structure is controlled through the elastic force, when the sealing structure is opened, the valve assembly communicates with the sampling cylinder.

3. A downhole PVT sampler according to claim 2, wherein, A plurality of sealing rings are arranged between the sealing pipe and the sampling cylinder, and the shell is connected with the sampling cylinder (3) through threads.

4. A downhole PVT sampler according to claim 2, wherein, The sealing structure comprises a taper groove and a tapered sealing block matched with the taper groove, and the return spring assembly comprises a spring and a pull rod. The taper groove is arranged at the end of the sealing pipe, the spring is arranged in the shell, one end of the pull rod is connected with the spring, and the other end of the pull rod extends into the sampling cylinder (3) and is connected with the tapered sealing block, and when the spring is compressed, the tapered sealing block is separated from the taper groove.

5. The downhole PVT sampler of claim 1, wherein, A fluid outlet is arranged on the first valve assembly, and a fluid inlet (8) is arranged on the second valve assembly.

6. A downhole PVT sampler according to claim 5, wherein, The upper end of the first valve assembly is connected with a jar, and the lower end of the second valve assembly is connected with a control device.

7. A downhole PVT sampler according to claim 6, wherein, The control device is a clock control mechanism, a wall-mounted control mechanism or a shear pin type control mechanism.

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