Quantifying device for pressure-maintaining sample transfer

Abstract

The utility model belongs to the field of underground sample transfer, and particularly relates to a quantifying device for pressure-maintaining sample transfer. The quantifying device for pressure maintaining and sample transferring comprises a quantifying pump, the quantifying pump is provided with a liquid inlet cavity and an adjusting mechanism for adjusting the size of the liquid inlet cavity, and the adjusting mechanism enlarges the liquid inlet cavity to the maximum size during liquid inlet and reduces the liquid inlet cavity to the minimum size during liquid outlet; the liquid inlet cavity is provided with a liquid inlet and a liquid outlet, the liquid inlet and the liquid outlet are connected with a liquid inlet pipe and a liquid outlet pipe, and the liquid inlet pipe and the liquid outlet pipe are provided with a liquid inlet valve and a liquid outlet valve respectively. The inlet and the outlet of the metering pump are connected with the liquid inlet pipe and the liquid outlet pipe which are provided with the valves, displacement liquid firstly enters the metering device to be quantified and then is discharged during sample transfer, and the operation is repeated, so that high-pressure quantitative liquid inlet and liquid discharge are realized, and the controllability of the release amount of the displacement liquid in the sample storage bottle is improved.

Description

Technical Field

[0001] The utility model belongs to the field of transferring downhole samples, and particularly relates to a quantitative device for pressure-maintaining sample transfer. Background Art

[0002] Mastering the basic phase properties of reservoir fluid samples is the basis for reserve calculation, dynamic analysis, and development plan establishment. It is also of crucial guiding significance for reservoir fluid type judgment and development plan formulation. The reservoir fluid sampling methods are mainly divided into surface sampling and downhole sampling. Among them, the samples directly obtained downhole have higher representativeness and can thus more accurately reflect the actual situation of downhole fluids.

[0003] The sampler is the main equipment for downhole sampling. During sampling, the sampler is first lowered to a predetermined position downhole. After the downhole fluid enters the sampler, it is sealed and stored. After sampling, the sampler is lifted from downhole to the surface. At this time, it is necessary to transfer the downhole sample in the sampler to the sample storage bottle under pressure and then send it to a laboratory analysis institution for phase analysis such as bubble point. During the sample transfer process, it is necessary to maintain pressure (that is, the pressure during the sample transfer process should be above the sample pressure), otherwise the phase of the sample will undergo irreversible changes due to pressure reduction, thereby affecting the accuracy of the analysis results.

[0004] The sample storage bottle is a piston-type container. Inside, the displacement fluid and the sample are separated by a piston. According to the properties of the fluids on both sides of the piston, the two ends of the sample storage bottle can be divided into a displacement fluid end and a sample end. During sample transfer, the outlet of the sampler is connected to the sample end of the sample storage bottle. A displacement pressure greater than the downhole sample pressure is applied to the floating piston of the sampler, and then the displacement fluid at the displacement fluid end of the sample storage bottle is gradually released, so that the downhole sample in the sampler can enter the sample end of the sample storage bottle.

[0005] In actual operation, generally, the displacement fluid is released by opening the gate at the displacement fluid end of the sample storage bottle. This method is applicable to low-pressure samples. However, when transferring high-pressure downhole samples (for example, often above 20 MPa), since the displacement fluid end of the sample storage bottle is also in a high-pressure state, it is very difficult to control the release amount of the displacement fluid through the gate switch, and the situation where the release process is lower than the downhole sample pressure often occurs. Content of the Utility Model

[0006] The purpose of the utility model is to provide a quantitative device for pressure-maintaining sample transfer to solve the problem that it is difficult to control the discharge of the displacement fluid at the displacement fluid end of the sample storage bottle.

[0007] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0008] A metering device for pressure-holding sample transfer, comprising a metering pump. The metering pump has a liquid inlet chamber and an adjusting mechanism for adjusting the size of the liquid inlet chamber. The adjusting mechanism enlarges the liquid inlet chamber to the maximum volume during liquid inlet and reduces the liquid inlet chamber to the minimum volume during liquid outlet. The liquid inlet chamber is provided with a liquid inlet and a liquid outlet, and a liquid inlet pipe and a liquid outlet pipe are connected to the liquid inlet and the liquid outlet respectively. A liquid inlet valve and a liquid outlet valve are respectively arranged on the liquid inlet pipe and the liquid outlet pipe.

[0009] The utility model belongs to an exploratory invention. By connecting a liquid inlet pipe and a liquid outlet pipe with valves to the inlet and outlet of the metering pump, during sample transfer, the displacement liquid first enters the metering device for metering and then is discharged. This is repeated to achieve high-pressure metering liquid inlet and discharge, improving the controllability of the displacement liquid release amount in the sample storage bottle.

[0010] Preferably, the pump body of the metering pump is provided with a piston hole. The adjusting mechanism includes a piston reciprocating in the piston hole and a top pressure elastic member for pushing the piston downward. The bottom surface of the piston constitutes the top surface of the liquid inlet chamber.

[0011] Further preferably, the adjusting mechanism includes a limiting member for limiting the upward movement of the piston. The top pressure elastic member is a compression spring connected between the limiting member and the piston.

[0012] More preferably, the piston includes a piston rod and a piston head with a diameter larger than that of the piston rod. The piston head is adapted to the piston chamber, and the compression spring is sleeved on the piston rod. The limiting member is provided with a stepped hole. The small hole section of the stepped hole is adapted to the piston rod, and the large hole section of the stepped hole is for the compression spring to be installed. The bottom surface of the large hole section presses the compression spring against the piston head.

[0013] Further preferably, the pump body of the metering pump is provided with a limiting member mounting hole connected to the upper end of the piston hole. The inner wall surface of the limiting member mounting hole is provided with internal threads, and the limiting member is provided with external threads matching the internal threads.

[0014] More preferably, the diameter of the limiting member mounting hole is larger than that of the piston hole.

[0015] Even more preferably, the lower end surface of the limiting member extends to the bottom wall of the limiting member mounting hole, and the lower end surface of the limiting member forms a limiting surface for restricting the upward movement of the piston.

[0016] Preferably, the lower end of the piston hole is connected to a liquid storage hole with a diameter smaller than that of the piston hole, and the liquid inlet pipe and the liquid outlet pipe are connected to the liquid storage hole. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of a pressure-holding sample transfer device using the metering device of the utility model;

[0018] Figure 2 ForFigure 1 Schematic structural diagram of the metering device;

[0019] Figure 3 Schematic structural diagram for filling the displacement fluid into the sample storage bottle;

[0020] Among them, 1 - sampler; 2 - sample storage bottle; 3 - metering device; 4 - displacement fluid tank; 5 - displacement pump; 6 - sampling piston; 7 - sample storage bottle piston; 8 - metering pump; 9 - inlet pipe; 10 - outlet pipe; 11 - inlet valve; 12 - outlet valve; 13 - threaded hole; 14 - piston hole; 15 - liquid storage hole; 16 - piston, 160 - piston head, 161 - piston rod; 17 - limit cap; 18 - compression spring; 19 - first pressure gauge; 20 - second pressure gauge; 21 - measuring cup. Specific implementation manner

[0021] The technical concept of the present utility model is to connect the metering device to the displacement fluid end of the sample storage bottle, intermittently and quantitatively release the displacement fluid, so that the change in the transfer sample pressure of the downhole sample matches the release amount of the displacement fluid, and the transfer sample pressure can be adjusted by adjusting the release amount of the displacement fluid. In this way, it is easy to achieve the transfer of the sample under a pressure higher than the sample pressure, and the entire transfer sample process is fast, stable and efficient.

[0022] The above-mentioned metering device includes a metering pump and an inlet pipe and an outlet pipe connected to the inlet and outlet of the metering pump. An inlet valve and an outlet valve are respectively arranged on the inlet pipe and the outlet pipe. When inletting liquid, the inlet valve is opened and the outlet valve is closed, and the high-pressure sample enters the metering pump; when discharging liquid, the inlet valve is closed and the outlet valve is opened, and the high-pressure sample flows out from the metering pump. The above-mentioned inlet and outlet operations are repeated, and the sample in the sampler gradually enters the sample storage bottle until the transfer of the sample is finally completed.

[0023] A pressure-holding sample transfer device for a sampler, including a displacement pump and a sample storage bottle for connecting with the sampler. The displacement fluid end of the sample storage bottle is connected with a metering device. The metering device includes a metering pump, and the metering pump has an inlet chamber and an adjusting mechanism for adjusting the size of the inlet chamber. The adjusting mechanism enlarges the inlet chamber to the maximum volume when inletting liquid and reduces the inlet chamber to the minimum volume when discharging liquid; the inlet chamber is provided with an inlet and an outlet, and an inlet pipe and an outlet pipe are connected to the inlet and the outlet. An inlet valve and an outlet valve are respectively arranged on the inlet pipe and the outlet pipe.

[0024] For the above-mentioned pressure-holding sample transfer device of the sampler, each time the released displacement fluid enters the metering pump through the inlet pipe, the inlet of the liquid stops when the quantitative volume is reached and the liquid is discharged through the outlet pipe; the above-mentioned inlet and discharge operations are repeated to realize the quantitative release of the displacement fluid in the sample storage bottle each time, improve the controllability of the transfer sample pressure, and effectively avoid transferring the sample under a pressure lower than the downhole sample pressure.

[0025] Preferably, the pump body of the metering pump is provided with a piston hole, and the regulating mechanism comprises a piston reciprocating in the piston hole, and a top pressure elastic member pushing the piston downward; the bottom surface of the piston constitutes the top surface of the liquid inlet cavity.

[0026] Further preferably, the adjusting mechanism comprises a limit piece for limiting the upward movement of the piston; the pressing elastic piece is a compression spring connected between the limit piece and the piston; the piston comprises a piston rod and a piston head with a diameter larger than the piston rod, the piston head is adapted to the piston cavity, and the compression spring is passed through the piston rod; the limit piece is provided with a stepped hole, the small hole section of the stepped hole is adapted to the piston rod, and the large hole section of the stepped hole is for the compression spring to be installed, and the bottom surface of the large hole section presses the compression spring against the piston head.

[0027] Preferably, the lower end of the piston hole is connected to a liquid storage hole with a diameter smaller than that of the piston hole, and the liquid inlet pipe and the liquid outlet pipe are connected to the liquid storage hole.

[0028] Preferably, a first pressure gauge is provided on the connecting pipeline between the displacement pump and the sampler; and a second pressure gauge is provided on the connecting pipeline between the sample storage bottle and the liquid inlet valve.

[0029] Specifically, the pressure-maintaining sample transfer device of the sampler is as follows: Figure 1 and Figure 2 As shown, it includes a sampler 1, a sample storage bottle 2, a quantitative device 3, a displacement liquid tank 4 and a displacement pump 5.

[0030] The sampler 1 is a downhole sampling device. After the downhole sampling is completed, the pressure-maintaining sample transfer device of the utility model is connected. The pressure-maintaining sample transfer device of the utility model is to transfer the downhole sample in the sampler to the sample storage bottle under the condition of higher pressure than the downhole sample. The sampler is built with a sampling piston 6, which can achieve displacement under a displacement pressure higher than the sample pressure inside it. The sampler 1 has a displacement fluid inlet and a sample outlet.

[0031] The sample outlet of the sampler 1 is connected to the sample storage bottle 2. The sample storage bottle 2 is a piston displacement container, in which a sample storage bottle piston 7 is arranged, and the sample storage bottle piston 7 separates the sample from the displacement fluid. The two ends of the sample storage bottle 2 are respectively divided into a sample end and a displacement fluid end according to the properties of the liquid. The sample end is connected to the sample outlet of the sampler 1, and the displacement fluid end is connected to the quantitative device 3.

[0032] The quantitative device 3 is mainly used for intermittent and quantitative release of displacement fluid under high pressure conditions. Figure 2As shown in the figure, the metering device 3 includes a metering pump 8, a liquid inlet pipe 9 and a liquid outlet pipe 10 connected to the inlet and outlet of the metering pump 8, and a liquid inlet valve 11 and a liquid outlet valve 12 for controlling the on-off of the liquid inlet pipe 9 and the liquid outlet pipe 10. The metering pump 8 has a liquid inlet chamber and an adjusting mechanism for adjusting the size of the liquid inlet chamber. The inlet and outlet of the metering pump 8 are arranged on the liquid inlet chamber. The adjusting mechanism enlarges the liquid inlet chamber to the maximum volume during liquid inlet and reduces the liquid inlet chamber to the minimum volume during liquid outlet. The metering device 3 repeatedly performs metering liquid inlet and metering liquid discharge operations in the pressure-holding sample transfer device, thereby realizing variable and controllable metering of the sample transfer pressure.

[0033] The metering pump 8 includes a pump body. A three-stage stepped hole is formed in the middle of the pump body. The three-stage stepped hole is a threaded hole 13, a piston hole 14 and a liquid storage hole 15 that are connected in sequence from top to bottom and have gradually decreasing hole diameters. The piston hole 14 restricts the piston 16 to reciprocate axially. The liquid storage hole 15 is a blind hole. A liquid inlet and a liquid outlet are respectively formed on the left and right opposite side walls of the liquid storage hole 15. The liquid inlet part of the piston hole 14 and the liquid storage hole 15 form the liquid inlet chamber. The liquid inlet part of the piston hole 14 changes with the reciprocating movement of the piston 16, thereby causing the volume of the liquid inlet chamber to change.

[0034] The adjusting mechanism for adjusting the size of the liquid inlet chamber includes the piston 16 that reciprocates in the piston hole 14, a limiting member for limiting the upward movement of the piston 16, and a pressing elastic member for pushing the piston 16 downward. The limiting member is a limiting cap 17 threadedly connected in the threaded hole 13 of the pump body. The lower end surface of the limiting cap 17 forms a limiting surface for restricting the piston from continuing to move upward. The pressing elastic member is a compression spring 18 arranged between the limiting cap 17 and the piston 16.

[0035] The piston 16 is T-shaped and includes a piston head 160 and a piston rod 161 connected to the middle of the piston head. The piston head 160 is adapted to the piston hole 14. A central hole for the piston rod 161 to pass through is provided on the limiting cap 17. The central hole is a stepped hole, including a small hole section adapted to the piston rod 161 and a large hole section connected to the small hole section. The above-mentioned compression spring 18 is sleeved on the piston rod 161. One end of the compression spring 18 abuts against the bottom surface of the large hole section, and the other end abuts against the piston head 160.

[0036] The liquid inlet and the liquid outlet of the liquid storage hole 15 are respectively connected to the liquid inlet pipe 9 and the liquid outlet pipe 10. A liquid inlet valve 11 and a liquid outlet valve 12 are correspondingly arranged on the liquid inlet pipe 9 and the liquid outlet pipe 10. Among them, the liquid inlet pipe 9 is connected to the outlet of the displacement liquid end of the sample storage bottle 2. A first pressure gauge 19 is provided on the connection pipeline. The first pressure gauge 19 can monitor the pressure of the displacement liquid released by the sample storage bottle 2 (i.e., the sample storage bottle pressure). This pressure essentially reflects the pressure of the downhole sample entering the sample storage bottle. During the sample transfer process, it is only necessary to ensure that this pressure is above the sample pressure.

[0037] Upstream of the sampler 1 is also connected with a displacement pump 5 and a displacement liquid tank 4. A second pressure gauge 20 is also provided on the connecting pipeline between the displacement pump 5 and the sampler 1. The second pressure gauge 20 reflects the magnitude of the displacement pressure, and during the sample transfer process, it only needs to be maintained above the sample pressure.

[0038] Before the pressure-holding sample transfer device of the above sampler is used, first fill the displacement liquid section of the sample storage bottle 2 with displacement liquid. This process is as Figure 3 shown. The displacement liquid is injected into the sample storage bottle 2 by the displacement liquid tank 4 under the action of the displacement pump 5. When the value of the second pressure gauge 20 suddenly increases, it indicates that it has been filled.

[0039] See Figure 1 , after the sample storage bottle 2 is filled with displacement liquid, sample transfer is carried out. The displacement pump 5 is started, and the value of the first pressure gauge 20 is maintained above the sample pressure. The inlet valve 11 of the metering device 3 is opened and the outlet valve 12 is closed. The displacement liquid enters the piston hole 14 of the pump body of the metering pump 8. The displacement liquid pushes the piston 16 to move upward to the lower end face of the limit cap 17. Then the inlet valve 11 is closed and the outlet valve 12 is opened. The displacement liquid is discharged from the outlet pipe 10 and enters the measuring cup 21. The measuring cup 21 can collect the displacement liquid and calculate the volume of the sample transfer.

[0040] The specific sample transfer method using the above metering device is as follows: Fill the sample storage bottle with displacement liquid, and displace the downhole sample in the sampler to the sample storage bottle under a pressure higher than the sample pressure; during displacement, release the displacement liquid from the displacement liquid end of the sample storage bottle to the metering device, stop releasing when the quantitative volume is reached, and the downhole sample in the sampler enters the sample storage bottle quantitatively. Then, discharge the displacement liquid in the metering device; repeatedly perform the operations of quantitatively releasing the displacement liquid to the metering device and discharging the displacement liquid in the metering device to ensure that the sample in the sampler is transferred to the sample storage bottle under a pressure not lower than the sample pressure.

[0041] During the pressure-holding sample transfer process of the above metering device, after the sample storage bottle is filled with displacement liquid, the sample end of the sample storage bottle is emptied. When sampling, the displacement liquid enters the metering device quantitatively and then is discharged. This is repeated. The release amount of the displacement liquid each time is quantitatively controllable, thereby improving the controllability of the sampling pressure of the high-pressure downhole sample in the sampler entering the sample storage bottle, and effectively avoiding sample transfer under a pressure lower than the downhole sample pressure.

[0042] During the sample transfer process, the smaller the quantitative volume, the smaller the volume change amount of each sample transfer, and the easier it is to control the sample transfer pressure above the downhole sample pressure. Preferably, the quantitative volume is not greater than 2 mL.

[0043] The above sample transfer method and the supporting device ensure that the downhole sample in the sampler is transferred under a pressure not lower than the original pressure, maintain the phase state properties of the downhole sample, and further ensure the accuracy of the downhole fluid test analysis results.

[0044] The implementation process of the present utility model will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0045] The metering device for pressure-holding sample transfer in this embodiment, as Figure 2 shown, is specifically the metering device 3 in the above-mentioned pressure-holding sample transfer device, including a metering pump 8, a liquid inlet pipe 9, a liquid outlet pipe 10 connected to the inlet and outlet of the metering pump 8, and a liquid inlet valve 11 and a liquid outlet valve 12 for controlling the on / off of the liquid inlet pipe 9 and the liquid outlet pipe 10. The metering pump 8 has a liquid inlet chamber and an adjusting mechanism for adjusting the size of the liquid inlet chamber. The inlet and outlet of the metering pump 8 are arranged on the liquid inlet chamber. The adjusting mechanism enlarges the liquid inlet chamber to the maximum volume during liquid inlet and reduces the liquid inlet chamber to the minimum volume during liquid outlet. The metering device 3 repeatedly performs metering liquid inlet and metering liquid discharge operations in the pressure-holding sample transfer device, thereby realizing variable and controllable metering of the transfer pressure.

[0046] The metering pump 8 includes a pump body. A three-stage stepped hole is formed in the middle of the pump body. The three-stage stepped hole is a threaded hole 13 (i.e., the limiting member installation hole), a piston hole 14, and a liquid storage hole 15 that are connected in sequence from top to bottom and have gradually decreasing diameters. The piston hole 14 restricts the piston 16 from making reciprocating movements in its axial direction. The liquid storage hole 15 is a blind hole. A liquid inlet and a liquid outlet are respectively formed on the left and right opposite side walls of the liquid storage hole 15. The liquid inlet part of the piston hole 14 and the liquid storage hole 15 constitute the liquid inlet chamber. The liquid inlet part of the piston hole 14 changes with the reciprocating movement of the piston 16, thereby causing the volume of the liquid inlet chamber to change.

[0047] The adjusting mechanism for adjusting the size of the liquid inlet chamber includes the piston 16 that reciprocates in the piston hole 14, a limiting member for limiting the upward movement of the piston 16, and a pressing elastic member for pushing the piston 16 downward. The limiting member is a limiting cap 17 threadedly connected to the threaded hole 13 of the pump body. The lower end surface of the limiting cap 17 forms a limiting surface for restricting the piston from continuing to move upward. The pressing elastic member is a compression spring 18 arranged between the limiting cap and the piston.

[0048] The piston 16 is T-shaped, including a piston head 160 and a piston rod 161 connected to the middle of the piston head. The piston head 160 is adapted to the piston hole 14. The limiting cap 17 is provided with a central hole for the piston rod 161 to pass through. The central hole is a stepped hole, including a small hole section adapted to the piston rod 161 and a large hole section connected to the small hole section. The above-mentioned compression spring 18 is sleeved on the piston rod 161. One end of the compression spring 18 abuts against the bottom surface of the large hole section, and the other end abuts against the piston head 160.

[0049] The liquid inlet and the liquid outlet of the liquid storage hole 15 are respectively connected to the liquid inlet pipe 9 and the liquid outlet pipe 10. The liquid inlet valve 11 and the liquid outlet valve 12 are correspondingly arranged on the liquid inlet pipe 9 and the liquid outlet pipe 10. Among them, the liquid inlet pipe 9 is connected to the outlet of the displacement liquid end of the sample storage bottle 2, and a first pressure gauge 19 is provided on the connection pipeline.

[0050] The pressure-holding sample transfer method using the above device is as follows: Fill the sample storage bottle 2 with displacement fluid, and displace the downhole sample in the sampler 1 into the sample storage bottle 2 under a pressure higher than the sample pressure. During displacement, release the displacement fluid from the displacement fluid end of the sample storage bottle 2 into the metering device 3. Stop releasing when the metered volume is reached. The downhole sample in the sampler 1 enters the sample storage bottle 2 quantitatively, and then the displacement fluid in the metering device 3 is discharged. Repeat the operations of quantitatively releasing the displacement fluid into the metering device 3 and discharging the displacement fluid in the metering device 3 to ensure that the sample in the sampler 1 is transferred to the sample storage bottle 2 under a pressure not lower than the sample pressure.

[0051] During the actual sample transfer process, the metered volume of the metering device 3 is 2 mL. In this way, the release amount of the displacement fluid each time is also 2 mL. Under this release amount, Figure 1 the reading of the first pressure gauge in [the device] is always above the sample pressure, which ensures that the pressure of the sample does not decrease during the sample transfer process, and thus can maintain its phase properties unchanged.

[0052] The above metered volume can also be controlled below 2 mL, such as 1.5 mL, 1 mL or 0.5 mL. In this way, the release amount each time is small, and the control of the sample transfer pressure is more accurate.

[0053] Generally speaking, the present utility model has the following characteristics:

[0054] 1. By using a metering device to release the displacement fluid of the sample storage bottle, the release amount of the displacement fluid is well controlled, enabling the original sample to be slowly transferred into the sample bottle, ensuring the balance and stability of the pressure of the original sample and the pressure in the sample storage bottle during the sample transfer process, and solving the accuracy of the analysis results of the sample sent for testing.

[0055] 2. The pressure-holding sample transfer device has been applied many times. During sample transfer, on-site, two pressure gauges are used to observe the pressures of the sampler and the sample storage bottle respectively. During sample transfer, the metering pump accurately measures the back pressure of the sample bottle when releasing, and the sample pressure is consistent with the original pressure, ensuring that the sample pressure does not decrease during the sample transfer process and guaranteeing the original phase retention ability of the sample.

[0056] 3. The pressure-holding sample transfer device is suitable for laboratory and on-site use. Through the analysis of high-pressure physical property fluid samples, it can provide a basis for the deployment of development wells, the design of surface engineering, and the planning of downstream projects, and can also provide a basis for the adjustment of development plans and gas production process measures, having great social and economic benefits.

Claims

1. A quantitative device for pressure-maintaining sample transfer, characterized in that: The invention comprises a metering pump, which has a liquid inlet cavity and an adjusting mechanism for adjusting the size of the liquid inlet cavity, wherein the adjusting mechanism enlarges the liquid inlet cavity to a maximum volume when liquid is inletted, and reduces the liquid inlet cavity to a minimum volume when liquid is outletted; the liquid inlet cavity is provided with a liquid inlet port and a liquid outlet port, the liquid inlet port and the liquid outlet port are connected with a liquid inlet pipe and a liquid outlet pipe, and the liquid inlet pipe and the liquid outlet pipe are provided with a liquid inlet valve and a liquid outlet valve respectively.

2. The quantitative device for pressure-maintaining sample transfer according to claim 1, characterized in that: The pump body of the metering pump is provided with a piston hole, and the regulating mechanism includes a piston reciprocating in the piston hole and a top-pressure elastic member pushing the piston downward; the bottom surface of the piston constitutes the top surface of the liquid inlet cavity.

3. The quantitative device for pressure-maintaining sample transfer according to claim 2, characterized in that: The regulating mechanism comprises a limiting member for limiting the upward movement of the piston; the pressing elastic member is a compression spring connected between the limiting member and the piston.

4. The quantitative device for pressure-maintaining sample transfer according to claim 3, characterized in that: The piston includes a piston rod and a piston head with a diameter larger than that of the piston rod, the piston head is adapted to the piston cavity, and the compression spring is passed through the piston rod; the limiting member is provided with a stepped hole, the small hole section of the stepped hole is adapted to the piston rod, and the large hole section of the stepped hole is for the compression spring to be installed, and the bottom surface of the large hole section presses the compression spring against the piston head.

5. The quantitative device for pressure-maintaining sample transfer according to claim 3 or 4, characterized in that: The pump body of the metering pump is provided with a limiter mounting hole connected to the upper end of the piston hole, the inner wall surface of the limiter mounting hole is provided with an internal thread, and the limiter is provided with an external thread matching the internal thread.

6. The quantitative device for pressure-maintaining sample transfer according to claim 5, characterized in that: The diameter of the position-limiting member mounting hole is larger than that of the piston hole.

7. The quantitative device for pressure-maintaining sample transfer according to claim 6, characterized in that: The lower end surface of the limiting member extends to the bottom wall of the limiting member mounting hole, and the lower end surface of the limiting member forms a limiting surface for limiting the upward movement of the piston.

8. The quantitative device for pressure-maintaining sample transfer according to claim 2, characterized in that: The lower end of the piston hole is connected with a liquid storage hole whose diameter is smaller than that of the piston hole, and the liquid inlet pipe and the liquid outlet pipe are connected to the liquid storage hole.

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