CN217440014U

CN217440014U - Gas sampling device for wellhead of oil and gas well

Info

Publication number: CN217440014U
Application number: CN202220430356.9U
Authority: CN
Inventors: 任垒; 杜远宗; 李韧; 张静; 刘敬; 王瑞杰
Original assignee: China Petroleum and Chemical Corp
Current assignee: China Petroleum and Chemical Corp
Priority date: 2022-03-01
Filing date: 2022-03-01
Publication date: 2022-09-16
Anticipated expiration: 2032-03-01

Abstract

The utility model relates to an oil gas well head gas sampling technical field, concretely relates to oil gas well head gas sampling device. The wellhead gas sampling device of the oil-gas well comprises a sampling cylinder with a piston cavity, wherein an exhaust piston is assembled in the piston cavity in a guiding manner; an air inlet valve is arranged on the front side cavity wall of the piston cavity; the front contour of the piston cavity is matched with the end shape of the exhaust piston; the rear end of the sampling cylinder is provided with a sealing cover, a driving rod penetrates through the sealing cover, and the driving rod is connected with the exhaust piston to drive the exhaust piston to perform exhaust action and air suction action; the side wall of the piston cavity is provided with an air outlet channel, the outlet end of the air outlet channel is provided with an exhaust valve, and the exhaust piston can move backwards under the driving of the driving rod and cross over the inlet end of the air outlet channel. By the design, the gas sampling device at the wellhead of the oil-gas well is suitable for conventional gas wells and gas wells with small gas volumes, and the gas sampling device at the wellhead of the oil-gas well is high in universality.

Description

Gas sampling device for wellhead of oil and gas well

Technical Field

The utility model relates to an oil gas well head gas sampling technical field, concretely relates to oil gas well head gas sampling device.

Background

The component test of the gas produced by the oil-gas well is an important means for carrying out dynamic analysis of the oil-gas well, and for conventional oil-gas production wells, the sampling of gas at the well mouth is generally completed by adopting a sampling steel cylinder on site at present. During the sample, open sampling steel bottle air inlet valve and gas outlet valve earlier, be connected gas inlet valve and well head manometer cock (cock is promptly the cock valve), back open well head manometer cock, utilize the well gas to sweep the sampling steel bottle, sweep and close gas outlet valve, the air inlet valve of sampling steel bottle in proper order again after abundant, accomplish sampling operation promptly.

However, for waste oil and gas wells, the gas quantity which can be stored in a shaft is small, particularly for a gas storage blocking well, because the shaft formed by the casing pipes is generally plugged by injecting ash and injected with protective liquid, the gas space which can be contained in the well is very limited, and when the gas in the well needs to be sampled and detected due to abnormal pressure at the well head, the gas quantity which can be sampled is small. Under this kind of condition, if adopt the conventional sampling steel bottle sample, the situation that gas can't fully sweep the sampling steel bottle in the oil gas well probably appears for still remaining the air in the sampling steel bottle, causing the gas sample that draws and the residual air in the sampling steel bottle to mix, influence follow-up chemical examination result.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide an oil gas well head gas sampling device to it can't fully sweep the unsafe technical problem of sample result that leads to adopt the steel bottle to solve prior art well gas volume when less well head gas is gaseous.

In order to achieve the above purpose, the utility model discloses oil gas well head gas sampling device's technical scheme is:

the wellhead gas sampling device for the oil-gas well comprises a sampling cylinder with a piston cavity, wherein an exhaust piston is assembled in the piston cavity in a guiding manner; the sampling cylinder is provided with a front side corresponding to the exhaust action direction of the exhaust piston and a rear side corresponding to the air extraction action direction of the exhaust piston, and the cavity wall of the front side of the piston cavity is provided with an air inlet valve for the gas in the oil and gas well to enter the piston cavity; the front profile of the piston cavity is matched with the end shape of the exhaust piston and is used for exhausting the gas in the piston cavity when the exhaust piston completely enters the piston cavity; the rear end of the sampling cylinder is provided with a sealing cover, a driving rod penetrates through the sealing cover, and the driving rod is connected with the exhaust piston to drive the exhaust piston to perform exhaust action and air suction action; the cavity side wall of the piston cavity is provided with an air outlet channel, the outlet end of the air outlet channel is provided with an exhaust valve, and the exhaust piston can move backwards under the driving of the driving rod and cross the inlet end of the air outlet channel so as to enable gas in the oil-gas well to sequentially pass through the air inlet valve, the piston cavity and the air outlet channel to purge the sampling cylinder when the exhaust valve is opened.

The beneficial effects are that: when the oil-gas well wellhead gas sampling device is used for sampling a conventional gas well, the gas inlet valve can be directly connected with a wellhead pressure gauge cock so as to perform purging work. When being used for the less gas well of sampling gas volume, need earlier discharge the cartridge interior air is whole, at this moment, actuating lever drive exhaust piston moves forward for the front end of exhaust piston laminates with the chamber bottom wall in piston chamber completely, discharges through the admission valve with the air in the piston chamber is whole, reduces the pressure in the cartridge, the well head gas of being convenient for flows and discharges through outlet channel in to the piston chamber, and then makes sampling gas be full of the cartridge, improves sampling gas purity and chemical examination result precision. By the design, the gas sampling device at the wellhead of the oil-gas well is suitable for conventional gas wells and gas wells with small gas volumes, and the gas sampling device at the wellhead of the oil-gas well is high in universality.

The front end of the exhaust piston is provided with a reducing section, and the diameter of the reducing section is gradually increased from front to back; the bottom wall of the piston cavity is provided with a diameter gradual change section which is matched with the shape of the reducing section.

The beneficial effects are that: when the exhaust piston moves forwards to exhaust gas in the piston cavity, the diameter gradual change section can guide the gas to be exhausted through the air inlet valve, and the exhaust of the original air in the piston cavity is facilitated; meanwhile, after gas in the well enters the piston cavity along the gas inlet valve, the diameter gradual change section of the piston cavity can guide the gas to flow, and the gas purging sampling cylinder in the well is facilitated.

In a further improvement, the reducing section is a conical section.

The beneficial effects are that: the conical section has a simple structure and is convenient to process.

In a further improvement, the front end face of the exhaust piston is provided with an exhaust rod for insertion into the intake valve to exhaust the gas therein.

The beneficial effects are that: by the design, the exhaust rod can exhaust residual air in the air inlet valve, and the testing precision of the sampled gas is further improved.

Further improved, more than two air outlet channels are distributed along the circumferential direction of the piston cavity.

The beneficial effects are that: design like this, be favorable to the gas in each corner in the sampling cylinder to discharge through outlet channel nearby, avoid having to sweep the dead angle and cause residual air in the sampling cylinder to influence the chemical examination precision of sample gas.

In a further improvement, the inlet end of the air outlet channel communicated with the piston cavity is inclined backwards.

The beneficial effects are that: due to the design, the inclined inlet end can guide the gas in the piston cavity to enter the gas outlet channel, and the blowing dead angle in the gas outlet channel is avoided.

In a further improvement, the cavity side wall of the piston cavity is provided with a piston stop structure so as to limit the backward movement limit position of the exhaust piston to just beyond the inlet end of the air outlet channel.

The beneficial effects are that: the design is that the exhaust piston is axially limited by the exhaust piston stopping structure, so that the condition that the exhaust piston passes through the inlet end backwards and then a sweeping dead angle exists between the front end surface of the exhaust piston and the cavity wall of the piston cavity is avoided, and the gas in the sampling cylinder is prevented from being discharged through the gas outlet channel.

Further improved, the piston stopping structure is a clamp spring.

The beneficial effects are that: the clamp spring is simple in structure and convenient to install and detach.

The further improvement is that the peripheral surface of the exhaust piston is provided with a sealing ring mounting groove, and a sealing ring is mounted in the sealing ring mounting groove.

The beneficial effects are that: design like this, sealed cooperation between exhaust piston and the sampling cylinder avoids the air to get into the piston chamber through the clearance between exhaust piston and the sampling cylinder inner wall to influence the gaseous chemical examination precision of sample.

The improved structure is characterized in that the driving rod is a driving screw rod, the driving screw rod is in threaded connection with the sealing cover, and a hand wheel is installed at one end, extending out of the sealing cover, of the driving screw rod.

The beneficial effects are that: by the design, the exhaust piston is driven to move by the hand wheel, so that the structure is simple and the operation is convenient; the drive screw rod is in threaded connection with the sealing cover, so that the situation that the drive screw rod is pushed to move backwards when the pressure in the piston cavity is high can be avoided.

Drawings

FIG. 1 is a schematic structural view of the wellhead gas sampling device of the oil and gas well of the utility model;

fig. 2 is a top view of the cartridge of fig. 1.

In the figure: 11. a sampling cartridge; 12. an exhaust piston; 13. sealing the cover; 14. a drive rod; 15. a hand wheel; 16. an exhaust valve; 17. a seal ring; 18. a clamp spring; 19. an air outlet channel; 20. an exhaust rod; 21. an intake valve; 22. a piston cavity; 23. a reducing section.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention, i.e., the described embodiments are only some, but not all embodiments of the invention. The components of embodiments of the present invention, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the accompanying drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiment of the present invention, all other embodiments obtained by the person skilled in the art without creative work belong to the protection scope of the present invention.

It is noted that relational terms such as "first" and "second," and the like, which may be present, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, terms such as "comprises," "comprising," or any other variation thereof, which may be present, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, elements recited by the phrases "comprising an … …," or the like, do not exclude the presence of such elements, processes, or methods.

In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" when they are used are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; either directly or indirectly through intervening media, or may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those skilled in the art from the specific situation.

In the description of the present invention, it should be noted that, unless explicitly stated or limited otherwise, the term "provided" may be used in a broad sense, for example, the object of "provided" may be a part of the body, or may be arranged separately from the body and connected to the body, and the connection may be a detachable connection or a non-detachable connection. The specific meaning of the above terms in the present invention can be understood by those skilled in the art from the specific situation.

The present invention will be described in further detail with reference to examples.

The utility model discloses an oil gas well head gas sampling device's embodiment 1:

the utility model discloses an oil gas well head gas sampling device can be connected with the manometer cock of oil gas well head to make the well head gas sweep sampling device, and then sampling device takes a sample to the well head gas.

As shown in fig. 1, the gas sampling device at the wellhead of the oil and gas well comprises a sampling cylinder 11 with a piston cavity 22, an exhaust piston 12 is guided in the piston cavity 22, and the exhaust piston 12 moves in the piston cavity 22 to perform exhaust and air suction. The exhaust operation direction of the exhaust piston 12 is defined as the front side, and the air-extracting operation direction of the exhaust piston 12 is defined as the rear side. The rear end of the sampling cylinder 11 is an opening, the opening is in threaded connection with a sealing cover 13, a driving rod 14 extending along the axial direction of the sampling cylinder 11 penetrates through the sealing cover 13, in this embodiment, the driving rod 14 is a driving screw rod, and the driving screw rod is in threaded connection with the sealing cover 13. A hand wheel 15 is installed at one end, extending out of the sampling cylinder 11, of the driving rod 14, one end, extending into the sampling cylinder 11, of the driving rod 14 is fixed to the rear end of the exhaust piston 12, and the hand wheel 15 can be rotated to drive the exhaust piston 12 to screw in and out so as to perform exhaust action and air suction action in the sampling cylinder 11. Note that, when the drive rod 14 rotates, the cap 13 screwed to the drive rod 14 remains stationary.

As shown in fig. 1, the exhaust piston 12 includes a reducing section 23 disposed at the front end and a cylindrical section connected to the rear end of the reducing section 23, a sealing ring mounting groove is formed on the outer peripheral surface of the cylindrical section, and a sealing ring 17 is mounted in the sealing ring mounting groove to realize the sealing engagement between the exhaust piston 12 and the sampling cylinder 11. The reducing section 23 is a conical section with the diameter gradually increasing from front to back, the bottom wall of the piston cavity 22 is provided with a diameter gradually-changing section matched with the reducing section 23 in shape, so that when the exhaust piston 12 completely enters the piston cavity 22, the reducing section 23 is attached to the diameter gradually-changing section to discharge all gas in the piston cavity 22, redundant air is removed for subsequent purging work, and the influence of mixing of the air and the purging gas on the component test result of the sampled gas is avoided.

As shown in fig. 1 and 2, the front end of the sampling cylinder 11 is connected with an air inlet valve 21 in a threaded manner, the air inlet valve 21 is used for being connected with a pressure gauge at a well head, a pore passage of the air inlet valve 21 is communicated with a piston cavity 22 and a well head pipeline, and a pore passage of the air inlet valve 21 forms an air inlet of the sampling cylinder 11. Two air outlet channels 19 extending along the axial direction of the sampling cylinder 11 are formed in the side wall of the sampling cylinder 11, and the two air outlet channels 19 are symmetrically arranged along the axis of the sampling cylinder. The inlet end of the air outlet channel 19 is communicated with the piston cavity 22, the outlet end of the air outlet channel 19 is provided with the exhaust valve 16, and when the air inlet valve 21 and the exhaust valve 16 are opened, the wellhead gas sequentially passes through the air inlet, the piston cavity 22 and the air outlet channel 19 to purge the gas in the sampling cylinder 11, so that the wellhead gas is sampled. And the inlet end of the air outlet channel 19 inclines upwards to guide the air in the piston cavity 22 to smoothly enter the air outlet channel 19, so that the air outlet channel 19 is prevented from having a sweeping dead angle. In other embodiments, one, three or more air outlet channels can be provided.

As shown in fig. 1, an exhaust rod 20 extending along the axial direction of the piston cavity 22 is disposed on the front end surface of the reducing section 23, the outer diameter of the exhaust rod 20 is the same as the inner diameter of the hole of the air intake valve 21, and the exhaust rod 20 can be inserted into the hole of the air intake valve 21 to exhaust the gas in the hole, thereby improving the purity of the sampled gas.

As shown in fig. 1, a snap spring 18 is disposed on the cavity side wall of the piston cavity 22, and when the rear end of the exhaust piston 12 is in stop fit with the snap spring 18, the front end surface of the exhaust piston 12 just crosses over the inlet end of the air outlet channel 19, so as to avoid a blowing dead angle formed between the front end surface of the exhaust piston 12 and the cavity side wall of the piston cavity 22, and facilitate the air entering the air outlet channel 19. At this moment, the front end face of the exhaust piston 12, the inner wall of the sampling cylinder 11 and the air outlet channel 19 enclose a sample storage space for storing wellhead sampling gas, and when the wellhead gas sweeps the sampling cylinder 11, the sample storage space can store the wellhead gas so as to sample the wellhead gas. In this embodiment, the snap spring 18 forms a piston stopper structure.

When the gas sampling device at the wellhead of the oil-gas well is used for sampling a conventional gas well, the gas inlet valve 21 and the gas outlet valve 16 are opened, the hand wheel 15 is rotated to unscrew the gas outlet piston 12 until the gas outlet piston is in blocking fit with the clamp spring 18, the gas outlet channel 19 is communicated with the piston cavity 22, the gas inlet valve 21 is connected with a pressure gauge of the wellhead, the pressure gauge of the wellhead is opened, and after the gas is fully purged, the gas outlet valve 16, the gas inlet valve 21 and the pressure gauge are sequentially closed to finish sampling operation.

When the gas sampling device at the wellhead of the oil-gas well is used for a waste gas well with a small sampling gas amount, the wellhead pressure is low, in order to discharge the air in the sampling cylinder 11, the air inlet valve 21 is opened firstly, the exhaust valve 16 is closed, the hand wheel 15 is rotated to enable the exhaust piston 12 to be screwed forward to be in full contact with the cavity bottom wall of the piston cavity 22, and all the air in the sampling cylinder 11 is discharged. Then, the air inlet valve 21 is connected with a pressure gauge cock at the wellhead, the pressure gauge cock and the air outlet valve 16 are opened, the hand wheel 15 is rotated reversely to enable the air outlet piston 12 to be screwed out to be in blocking fit with the clamp spring 18, and then the air outlet valve 16, the air inlet valve 21 and the pressure gauge cock are closed in sequence to complete sampling operation.

When the oil-gas well wellhead gas sampling device is used for sampling a conventional gas well, the gas inlet valve can be directly connected with a wellhead pressure gauge cock so as to perform purging work. When being used for the less gas well of sample gas volume, need earlier discharge the whole dischargings of interior air of sampling cylinder, at this moment, actuating lever drive exhaust piston moves forward for the front end of exhaust piston laminates with the chamber bottom wall in piston chamber completely, discharges through the admission valve with the air in the piston chamber is whole, reduces the pressure in the sampling cylinder, the well head gas of being convenient for flows and discharges through outlet channel to the piston intracavity, and then makes the sampling gas be full of the sampling cylinder, improves sample gas purity and chemical examination result precision. By the design, the gas sampling device at the wellhead of the oil-gas well is suitable for conventional gas wells and gas wells with small gas volumes, and the gas sampling device at the wellhead of the oil-gas well is high in universality.

The utility model discloses an oil gas well head gas sampling device's embodiment 2:

this example differs from example 1 in that: in embodiment 1, the front end of the exhaust piston 12 is provided with a reducing section 23, and the diameter of the reducing section 23 gradually increases from front to back; the bottom wall of the piston cavity 22 is provided with a diameter transition section with a shape matched with the shape. In this embodiment, the arrangement of the neck section is cancelled, the front end face of the exhaust piston is a plane, and correspondingly, the bottom wall of the cavity of the piston cavity is a plane.

The utility model discloses an oil gas well head gas sampling device's embodiment 3:

the present example differs from example 1 in that: in example 1, the reduced diameter section 23 is a tapered section. In this embodiment, the reducing section is hemispherical.

The utility model discloses an oil gas well head gas sampling device's embodiment 4:

this example differs from example 1 in that: in embodiment 1, the front end surface of the exhaust piston 12 is provided with an exhaust rod 20, and the exhaust rod 20 is inserted into the intake port to exhaust the gas in the intake valve 21. In the embodiment, the exhaust rod is not arranged, and the air in the pore passage of the air inlet valve is less, so that the proportion of the air in the sampled gas is less, and the influence on the test result of the sampled gas is less.

The utility model discloses an oil gas well head gas sampling device's embodiment 5:

this example differs from example 1 in that: in embodiment 1, the inlet end of the air outlet channel 19 communicating with the piston chamber 22 is inclined rearward. In this embodiment, the inlet end is perpendicular to the axis of the cartridge.

The utility model discloses an oil gas well head gas sampling device's embodiment 6:

this example differs from example 1 in that: in embodiment 1, the cavity side wall of the piston cavity 22 is provided with a snap spring 18, when the exhaust piston 12 is in stop fit with the snap spring 18, the exhaust piston 12 just passes over the inlet end of the air outlet channel 19, and the snap spring 18 forms a piston stop structure. In this embodiment, the piston stop structure is a screw or a pin penetrating the cavity sidewall of the piston cavity. In other embodiments, a piston stopping structure is omitted, the length of the sampling cylinder is adjusted, when the exhaust piston moves backwards to just cross the inlet end of the air outlet channel, the rear end face of the exhaust piston is in contact with the sealing cover, and the exhaust piston is axially limited through the sealing cover. Of course, the vent piston may also be located behind the inlet end of the vent passageway when the vent piston is engaged with the closure stop.

The utility model discloses an oil gas well head gas sampling device's embodiment 7:

this example differs from example 1 in that: in embodiment 1, a seal ring mounting groove is provided on the outer peripheral surface of the exhaust piston 12, and a seal ring 17 is mounted in the seal ring mounting groove. In this embodiment, the cavity wall of the piston cavity is provided with a sealing ring mounting groove. In other embodiments, the installation groove of the sealing ring can be eliminated.

The utility model discloses an oil gas well head gas sampling device's embodiment 8:

this example differs from example 1 in that: in embodiment 1, the driving rod 14 is a driving screw rod, the driving screw rod is in threaded connection with the sealing cover 13, and a hand wheel 15 is mounted at one end of the driving screw rod extending out of the sealing cover 13. In this embodiment, a hand wheel is not provided, and at this time, the end of the driving screw rod extending out of the end cap is hexagonal, and the hexagonal end can be clamped and rotated by a wrench, so that the exhaust piston is screwed and unscrewed. In other embodiments, the driving rod is a polished rod penetrating through the sealing cover, and at this time, a hand wheel can be omitted, and an operator directly operates one end of the polished rod extending out of the sampling cylinder to drive the exhaust piston to move. In other embodiments, whether the end of the drive rod remote from the exhaust piston extends out of the sampling cylinder or is located in the sampling cylinder, the end is connected with an output shaft of a motor, and the drive rod is driven to move by the motor.

Finally, it should be noted that the above mentioned embodiments are only preferred embodiments of the present invention, and not intended to limit the present invention, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made without inventive effort to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some of the technical features. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The wellhead gas sampling device for the oil and gas well is characterized by comprising a sampling cylinder (11) with a piston cavity (22), wherein an exhaust piston (12) is assembled in the piston cavity (22) in a guiding manner; the sampling cylinder (11) is provided with a front side corresponding to the exhaust action direction of the exhaust piston (12) and a rear side corresponding to the air extraction action direction of the exhaust piston (12), and the cavity wall of the front side of the piston cavity (22) is provided with an air inlet valve (21) for gas in an oil-gas well to enter the piston cavity (22); the front profile of the piston cavity (22) is matched with the end shape of the exhaust piston (12) and is used for exhausting the gas in the piston cavity (22) when the exhaust piston (12) completely enters the piston cavity (22); a sealing cover (13) is arranged at the rear end of the sampling cylinder (11), a driving rod (14) penetrates through the sealing cover (13), and the driving rod (14) is connected with the exhaust piston (12) to drive the exhaust piston (12) to perform exhaust action and air suction action; be equipped with air outlet channel (19) on the chamber lateral wall of piston chamber (22), the exit end of air outlet channel (19) is equipped with discharge valve (16), and discharge piston (12) can be under the drive of actuating lever (14) backward motion and cross the entrance point of air outlet channel (19) to make gas in the oil gas well loop through admission valve (21), piston chamber (22) and air outlet channel (19) and sweep sampling cylinder (11) when discharge valve (16) are opened.

2. An oil and gas well wellhead gas sampling device according to claim 1, characterized in that the front end of the exhaust piston (12) is provided with a reducing section (23), the diameter of the reducing section (23) is gradually increased from front to back; the bottom wall of the piston cavity (22) is provided with a diameter gradual change section matched with the shape of the reducing section (23).

3. An oil and gas well wellhead gas sampling device as claimed in claim 2 characterised in that the reduced diameter section (23) is a tapered section.

4. Oil and gas well wellhead gas sampling device according to any of claims 1 to 3, characterized in that the front end face of the exhaust piston (12) is provided with an exhaust stem (20), the exhaust stem (20) being intended to be inserted into an intake valve (21) to exhaust the gas in the intake valve (21).

5. An oil and gas well wellhead gas sampling device as claimed in any one of claims 1 to 3, characterised in that the gas outlet passages (19) are distributed in at least two along the circumference of the piston cavity (22).

6. An oil and gas well wellhead gas sampling device as claimed in any of claims 1 to 3 characterised in that the inlet end of the gas outlet passage (19) communicating with the piston chamber (22) is inclined rearwardly.

7. An oil and gas well wellhead gas sampling device according to any of claims 1 to 3 characterized in that the piston chamber (22) is provided with piston stop structure on the chamber side wall to limit the extreme position of the exhaust piston (12) moving backwards to just beyond the inlet end of the gas outlet channel (19).

8. An oil and gas well wellhead gas sampling device as claimed in claim 7, wherein the piston stop structure is a circlip (18).

9. An oil and gas well wellhead gas sampling device as claimed in any one of claims 1 to 3, wherein the outer peripheral surface of the exhaust piston (12) is provided with a sealing ring mounting groove, and a sealing ring (17) is mounted in the sealing ring mounting groove.

10. An oil and gas well wellhead gas sampling device according to any one of claims 1 to 3, characterized in that the driving rod (14) is a driving screw rod, the driving screw rod is in threaded connection with the sealing cover (13), and a hand wheel (15) is installed at one end of the driving screw rod extending out of the sealing cover (13).