Full-closed gas sampling device for wellhead of oil well

Abstract

The utility model discloses a fully-closed gas sampling device for a wellhead of an oil well. According to the technical scheme, a gas sampling device and a hydraulic pump are installed on the upper surface of a sampling device base, the bottom of the gas sampling device is connected to a sampling valve through a sampling pipe, the top of the gas sampling device is connected to the input end of a gas buffer through a pipeline and a control valve, and the output end of the gas buffer is connected with a gas inlet of a gas sampling bag through a pipeline; a gas outlet of the gas collecting bag is connected to the gas purifier through a pipeline; and one side of the top of the gas taking device is connected to the hydraulic pump through a hydraulic pipeline. The device has the beneficial effects that residual associated gas is introduced into the gas purifier, so that harmless treatment is realized; besides, after gas sample collection is finished, oil-gas mixed liquid taken out from a wellhead is pressed back into a wellhead pipeline by a hydraulic pump, so that crude oil sewage is prevented from falling to the ground, harmless treatment of toxic and harmful gas such as hydrogen sulfide in associated gas is realized, dissipation of toxic gas in the sampling process is reduced, and personal injury accidents are avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of oil field sampling, in particular to a fully enclosed gas sampling device at an oil well head. Background Art

[0002] In the oilfield production and gathering and transportation process, multiple links need to collect oil samples, water samples, and associated gas samples, and detect the chemical composition of the oil phase, water phase, and gas phase, so as to provide a basis for the subsequent production adjustment of the oil well and the implementation of anti-corrosion and anti-scaling measures; in the wellhead sampling process, the conventional method is to directly open the valve of the reserved sampling port, and the oil sample, water sample, associated gas sample, etc. will flow into the sampling barrel from the sampling port. In particular, in the process of gas collection, no closed device is used, so the air is in direct contact with the sampling barrel, which will cause the dissolved oxygen content in the water phase in the sampling barrel to increase. In addition, after the sampling barrel is left to stand for a period of time, the oilfield associated gas in the oil sample will slowly escape, which will cause the hydrocarbon gas content in the oilfield associated gas to decrease on the one hand, and on the other hand, the oilfield associated gas contains toxic gases such as toxic hydrogen sulfide, so it is easy to cause poisoning risks during the collection process. However, in the existing technology, when sampling, it is difficult for the sampling barrel, gas sampling bag and wellhead to be completely sealed and connected, which may cause deviations in the test results on the one hand, and cause health damage to the test personnel on the other hand.

[0003] The Chinese patent document number is CN211038630U, and the patent name is "A Sampling Device at the Oil Wellhead", which includes an oil pipeline, an opening is opened on the bottom wall of the oil pipeline, a connecting pipe is connected to the opening at the bottom of the oil pipeline, the connecting pipe and the opening are connected to each other, and a lower oil cylinder with a closed bottom is arranged at the bottom of the connecting pipe. The utility model is provided with a movable block in the lower oil cylinder, and a sealing sleeve is sleeved on the movable block, which is close to the inner wall of the lower oil cylinder. The movable block is moved upward in the lower oil cylinder to push the sample remaining in the lower oil cylinder after sampling back into the oil pipeline, so as to avoid the residual sample in the lower oil cylinder affecting the accuracy of the next sampling and analysis work; the movable sleeve in the rotating groove of the movable block has a turntable, and the turntable is fixedly sleeved on one end of the threaded rod, and the rotation of the threaded rod in the threaded sleeve is used to realize the up and down movement of the movable block in the lower oil cylinder. The problem is that it does not adopt a closed sampling method, which is easy to cause health damage to the detection personnel.

[0004] The Chinese patent document number is CN109632407A, and the patent name is "Closed sampling device and closed sampling method for oil well production fluid", which includes a sampling barrel, characterized in that it also includes a wellhead sampling valve, a metal hose, a threaded connection assembly, a rubber plug, a gas sampling bag and a sampling barrel mouth connection assembly; the wellhead sampling valve is arranged on the pipeline at the wellhead oil outlet, a flexible rubber plug is installed at the inlet of the sampling barrel, one end of the metal hose is connected to the outlet end of the wellhead sampling valve through a threaded connection assembly, the other end of the metal hose is connected to the sampling barrel through a sampling barrel mouth connection assembly, and the gas sampling bag is connected to the sampling barrel. The invention can realize the closed sampling of wellhead oil, water and gas mixed samples, avoid the mixing of air during the sampling process, and can realize the closed sampling from the wellhead to the sampling barrel and sampling bag, ensuring that the obtained oil well production fluid will not be polluted by air. The problems are: on the one hand, the sampling barrel used is equipped with a rubber stopper, which has a poor oil-water separation effect; on the other hand, a gas sampling bag is used. When in use, hydrocarbon gas is introduced into the gas sampling bag. When the gas sampling bag is full, the outlet valve is opened to squeeze out and replace the original gas in the sampling bag. After replacement three times, the gas sample is collected. This will still cause toxic gases such as hydrogen sulfide to escape, causing damage to the health of the testers.

[0005] In addition, the existing closed sampling device for oil well fluid production at the wellhead cannot determine the change of the liquid level in the device, and cannot determine whether the gas volume meets the test requirements when collecting gas samples; moreover, when producing gas, the gas collected by the sampling device is high-pressure gas. If a syringe is used directly to take samples, the volume is inaccurate and the test results are greatly deviated. The high-pressure venting balance pressure poses environmental risks and the risk of personnel poisoning.

[0006] Therefore, it is necessary to design a fully enclosed gas sampling device at the wellhead of an oil well. Utility Model Content

[0007] The purpose of the utility model is to provide a fully enclosed gas sampling device at the wellhead of an oil well in view of the above-mentioned defects in the prior art. The device adopts a safe and enclosed design to provide scientific data support for the collection, detection and treatment measures of associated gas, and at the same time, to harmlessly treat toxic and harmful gases such as hydrogen sulfide in the associated gas, reduce the escape of toxic gases during the sampling process, and avoid personal injury accidents.

[0008] The utility model mentions a fully enclosed gas sampling device at the wellhead of an oil well, and its technical solution is: it includes a sampling device base, a gas extraction device, a sampling tube, a control valve, a gas buffer, a gas collection bag, a gas purifier, a hydraulic pipeline, and a hydraulic pump. The gas extraction device and the hydraulic pump are installed on the upper surface of the sampling device base, the bottom of the gas extraction device is connected to the sampling valve through the sampling tube, the top of the gas extraction device is connected to the input end of the gas buffer through the pipeline and the control valve, the output end of the gas buffer is connected to the air inlet of the gas collection bag through the pipeline, and the air outlet of the gas collection bag is connected to the gas purifier through the pipeline; one side of the top of the gas extraction device is connected to the hydraulic pump through the hydraulic pipeline.

[0009] Preferably, the gas extraction device includes a base plate, fixing screws, an oil and gas inlet, a gas collection cylinder, a movable piston, and a magnetic flap level meter. The bottom of the gas collection cylinder is fixed with a base plate, the middle of the base plate is provided with an oil and gas inlet, and the outer side of the base plate is connected to the base of the sampling device by fixing screws; a movable piston is installed in the inner cavity of the gas collection cylinder, and a magnetic flap level meter is installed on the gas collection cylinder, and a gas collection outlet is provided on the top of the movable piston.

[0010] Preferably, the magnetic flap level meter comprises a magnetic float and a level display panel, wherein the magnetic float is arranged in the middle inner cavity of the movable piston, and the level display panel is installed on one side of the top of the gas collection cylinder.

[0011] Preferably, the movable piston comprises a lower piston extension and an upper piston body, a protruding lower piston extension is provided at the lower end of the upper piston body, and an oil and gas storage chamber is provided in the inner cavity of the upper piston body.

[0012] Preferably, the magnetic float is installed in the oil and gas storage cavity of the inner cavity of the upper piston body.

[0013] Preferably, a back pressure port is provided at the top of the gas collection cylinder.

[0014] Preferably, an upper sealing ring is arranged on the outer side of the upper piston body.

[0015] Preferably, a lower sealing ring is provided on the outer side of the lower piston extension body.

[0016] Preferably, a roller is provided at the bottom of the base of the sampling device, and a pressure gauge is installed on the top of the movable piston.

[0017] Preferably, the above-mentioned gas purifier includes a sealed container, a purification liquid, a mixed gas input pipe, and a clean gas output pipe. The sealed container is provided with a purification liquid, the mixed gas input pipe is inserted into the purification liquid, and the lower end of the clean gas output pipe is located above the purification liquid in the sealed container.

[0018] The beneficial effects of the utility model are as follows: the utility model separates the oil and gas through the gas extraction device through the oil and gas mixed liquid extracted from the oil well, observes the change of the liquid level flap meter to control the liquid inlet level of the device, prevents the sampled liquid phase from overflowing and polluting the gas extraction chamber, controls the gas extraction volume by the control valve, and enters the double-valve gas extraction bag through the gas buffer to provide a gas sample for the next step of normal pressure testing and analysis, and introduces the residual associated gas into the gas purifier to achieve harmless treatment; in addition, after the gas sample is collected, the hydraulic pump injects high-pressure liquid into the upper end cavity of the gas extraction device, and the piston movement inside the device hydraulically returns the oil and gas mixture extracted from the wellhead to the wellhead pipeline, so that the crude oil and sewage do not fall to the ground, and the toxic and harmful gases such as hydrogen sulfide in the associated gas are harmlessly treated, and the escape of toxic gases during the sampling process is reduced to avoid the occurrence of personal injury accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0020] Figure 2 It is a structural schematic diagram of the gas extraction device;

[0021] Figure 3 is a schematic structural diagram of a first embodiment of a mobile piston;

[0022] Figure 4 It is a schematic diagram of the structure of a gas purifier;

[0023] Figure 5 is a schematic structural diagram of a second embodiment of a mobile piston;

[0024] Figure 6 It is a schematic diagram of the structure of the gas collection bag;

[0025] In the figure above: sampling device base 1, roller 2, gas extraction device 3, sampling tube 4, control valve 5, gas buffer 6, gas sampling bag 7, gas purifier 8, pressure gauge 9, hydraulic pipeline 10, hydraulic pump 11, bottom plate 3.1, fixing screw 3.2, lower sealing ring 3.3, oil and gas inlet 3.4, gas sampling tube 3.5, magnetic float 3.6, movable piston 3.7, back pressure port 3.8, upper sealing ring 3.9, liquid level display board 3.10, gas sampling outlet 3.11, aluminum foil bag body 7.1, air inlet valve 7.2, air outlet valve 7.3, sealed container 8.1, purified liquid 8.2, mixed gas input pipe 8.3, clean gas output pipe 8.4. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0027] Example 1, reference Figure 1-Figure 4The utility model mentions a fully enclosed gas sampling device at the wellhead of an oil well, comprising a sampling device base 1, a gas extraction device 3, a sampling tube 4, a control valve 5, a gas buffer 6, a gas sampling bag 7, a gas purifier 8, a hydraulic pipeline 10, and a hydraulic pump 11. The gas extraction device 3 and the hydraulic pump 11 are installed on the upper surface of the sampling device base 1, the bottom of the gas extraction device 3 is connected to the sampling valve through the sampling tube 4, the top of the gas extraction device 3 is connected to the input end of the gas buffer 6 through the pipeline and the control valve 5, the output end of the gas buffer 6 is connected to the air inlet of the gas sampling bag 7 through the pipeline, and the air outlet of the gas sampling bag 7 is connected to the gas purifier 8 through the pipeline; one side of the top of the gas extraction device 3 is connected to the hydraulic pump 11 through the hydraulic pipeline 10.

[0028] Reference Figure 2 The gas extraction device 3 mentioned in the utility model includes a bottom plate 3.1, fixing screws 3.2, an oil and gas inlet 3.4, a gas collection tube 3.5, a movable piston 3.7, and a magnetic flap liquid level meter. The bottom of the gas collection tube 3.5 is fixed with the bottom plate 3.1, and the middle of the bottom plate 3.1 is provided with an oil and gas inlet 3.4. The outer side of the bottom plate 3.1 is connected to the sampling device base 1 through fixing screws 3.2; the inner cavity of the gas collection tube 3.5 is installed with a movable piston 3.7, and a magnetic flap liquid level meter is installed on the gas collection tube 3.5, and a gas collection outlet 3.11 is provided at the top of the movable piston 3.7.

[0029] The magnetic flap level meter mentioned in the utility model comprises a magnetic float 3.6 and a level display board 3.10. The magnetic float 3.6 is arranged in the middle inner cavity of the moving piston 3.7, and the level display board 3.10 is installed on one side of the top of the gas collection tube 3.5.

[0030] Reference Figure 3 The movable piston 3.7 mentioned in the utility model comprises a lower piston extension body 3.7.1 and an upper piston body 3.7.2. A protruding lower piston extension body 3.7.1 is provided at the lower end of the upper piston body 3.7.2, and an oil and gas storage chamber 3.7.3 is provided in the inner cavity of the upper piston body 3.7.2.

[0031] The magnetic float 3.6 is installed in the oil and gas storage chamber 3.7.3 of the inner cavity of the upper piston body 3.7.2. The magnetic float 3.6 cooperates with the liquid level display board 3.10 according to the liquid level, so as to display the liquid level for easy observation.

[0032] The top of the gas cylinder 3.5 is provided with a back pressure port 3.8, and the hydraulic pump pumps high pressure liquid into the gas cylinder 3.5 through the hydraulic pipeline 10 through the back pressure port 3.8, so that the movable piston 3.7 moves downward. The hydraulic pump 11 can be a manual hydraulic pump.

[0033] The bottom of the sampling device base 1 is provided with a roller 2, and the top of the movable piston 3.7 is provided with a pressure gauge 9 for displaying the pressure condition in the sampling device.

[0034] Reference Figure 4 The gas purifier 8 mentioned in the utility model includes a sealed container 8.1, a purification liquid 8.2, a mixed gas input pipe 8.3, and a clean gas output pipe 8.4. The sealed container 8.1 is provided with a purification liquid 8.2, the mixed gas input pipe 8.3 is inserted into the purification liquid 8.2, and the lower end of the clean gas output pipe 8.4 is located above the purification liquid 8.2 in the sealed container 8.1.

[0035] When the utility model is used, one end of the sampling tube 4 is connected to the sampling valve to be sampled, and the other end is connected to the gas extraction device 3 through the oil and gas inlet 3.4. Then, the high-pressure oil and gas mixture enters the inner cavity of the gas extraction device 3, and the oil and gas are separated by the gas extraction device. The changes of the magnetic flap liquid level meter are observed, and the liquid level of the inlet of the gas extraction device 3 is controlled to prevent the sampled liquid phase from overflowing and polluting. The gas extraction amount is controlled by the control valve 5, and enters the double-valve gas extraction bag 7 through the gas buffer 6 to provide gas samples for the next step of realizing normal pressure testing and analysis. The residual associated gas is introduced into the gas purifier 8 to realize Harmless treatment; when the gas sample collection is completed, the hydraulic pump 11 injects high-pressure liquid into the cavity between the movable piston 3.7 and the gas sampling cylinder 3.5 in the upper inner cavity of the gas extraction device 3, thereby pushing the gas sampling cylinder 3.5 to move downward, and the sampled oil and gas mixture is pressed back into the wellhead pipeline through the oil and gas inlet 3.4 and the sampling tube 4, so that during the sampling process, neither crude oil nor sewage falls to the ground, avoiding pollution to the environment and damage to the health of the testers, ensuring that the oil, gas and water sampling and testing processes meet the safety, environmental protection and occupational health management requirements.

[0036] Embodiment 2, the utility model mentions a fully enclosed gas sampling device at the wellhead of an oil well, comprising a sampling device base 1, a gas extraction device 3, a sampling tube 4, a control valve 5, a gas buffer 6, a gas collection bag 7, a gas purifier 8, a hydraulic pipeline 10, and a hydraulic pump 11. The gas extraction device 3 and the hydraulic pump 11 are installed on the upper surface of the sampling device base 1, the bottom of the gas extraction device 3 is connected to the sampling valve through the sampling tube 4, the top of the gas extraction device 3 is connected to the input end of the gas buffer 6 through the pipeline and the control valve 5, the output end of the gas buffer 6 is connected to the air inlet of the gas collection bag 7 through the pipeline, and the air outlet of the gas collection bag 7 is connected to the gas purifier 8 through the pipeline; one side of the top of the gas extraction device 3 is connected to the hydraulic pump 11 through the hydraulic pipeline 10.

[0037] The difference from Example 1 is:

[0038] An upper sealing ring 3.9 is arranged on the outer side of the upper piston body 3.7.2 of the movable piston 3.7, and is in sealing contact with the top outlet of the gas collection tube 3.5 through the upper sealing ring 3.9. In addition, a lower sealing ring 3.3 is arranged on the outer side of the lower piston extension body 3.7.1, and is in sealing sliding contact with the inner wall of the gas collection tube 3.5 through the lower sealing ring 3.3, thereby achieving a better sealing effect.

[0039] Embodiment 3, the utility model mentions a fully enclosed gas sampling device at the wellhead of an oil well, comprising a sampling device base 1, a gas extraction device 3, a sampling tube 4, a control valve 5, a gas buffer 6, a gas collection bag 7, a gas purifier 8, a hydraulic pipeline 10, and a hydraulic pump 11. The gas extraction device 3 and the hydraulic pump 11 are installed on the upper surface of the sampling device base 1, the bottom of the gas extraction device 3 is connected to the sampling valve through the sampling tube 4, the top of the gas extraction device 3 is connected to the input end of the gas buffer 6 through the pipeline and the control valve 5, the output end of the gas buffer 6 is connected to the air inlet of the gas collection bag 7 through the pipeline, and the air outlet of the gas collection bag 7 is connected to the gas purifier 8 through the pipeline; one side of the top of the gas extraction device 3 is connected to the hydraulic pump 11 through the hydraulic pipeline 10.

[0040] The difference from Example 2 is:

[0041] The hydraulic pump 11 mentioned in the present embodiment can adopt an electric hydraulic pump, thereby reducing the time for detection personnel to press the sampled oil and gas mixture back into the wellhead pipeline through the oil and gas inlet 3.4 and the sampling tube 4, so that during the sampling process, neither crude oil nor sewage falls to the ground, which is more efficient, saves effort and time.

[0042] Embodiment 4, the utility model mentions a fully enclosed gas sampling device at the wellhead of an oil well, comprising a sampling device base 1, a gas extraction device 3, a sampling tube 4, a control valve 5, a gas buffer 6, a gas collection bag 7, a gas purifier 8, a hydraulic pipeline 10, and a hydraulic pump 11. The gas extraction device 3 and the hydraulic pump 11 are installed on the upper surface of the sampling device base 1, the bottom of the gas extraction device 3 is connected to the sampling valve through the sampling tube 4, the top of the gas extraction device 3 is connected to the input end of the gas buffer 6 through the pipeline and the control valve 5, the output end of the gas buffer 6 is connected to the air inlet of the gas collection bag 7 through the pipeline, and the air outlet of the gas collection bag 7 is connected to the gas purifier 8 through the pipeline; one side of the top of the gas extraction device 3 is connected to the hydraulic pump 11 through the hydraulic pipeline 10.

[0043] The difference from Example 2 is:

[0044] Reference Figure 5In this embodiment, the lower piston extension body 3.7.1 of the movable piston 3.7 is thickened, which improves the stability of the upward and downward movement of the movable piston. In addition, a thickened lower sealing ring 3.3 is provided on the outer side of the lower piston extension body 3.7.1. The lower sealing ring 3.3 is in sealing and sliding contact with the inner wall of the gas collection tube 3.5 to achieve a better sealing effect.

[0045] Embodiment 5, the utility model mentions a fully enclosed gas sampling device at the wellhead of an oil well, comprising a sampling device base 1, a gas extraction device 3, a sampling tube 4, a control valve 5, a gas buffer 6, a gas collection bag 7, a gas purifier 8, a hydraulic pipeline 10, and a hydraulic pump 11. The gas extraction device 3 and the hydraulic pump 11 are installed on the upper surface of the sampling device base 1, the bottom of the gas extraction device 3 is connected to the sampling valve through the sampling tube 4, the top of the gas extraction device 3 is connected to the input end of the gas buffer 6 through the pipeline and the control valve 5, the output end of the gas buffer 6 is connected to the air inlet of the gas collection bag 7 through the pipeline, and the air outlet of the gas collection bag 7 is connected to the gas purifier 8 through the pipeline; one side of the top of the gas extraction device 3 is connected to the hydraulic pump 11 through the hydraulic pipeline 10.

[0046] The difference from Example 2 or 3 is:

[0047] The gas sampling bag 7 mentioned in this embodiment adopts an aluminum foil sampling bag. The aluminum foil used is a nylon film, aluminum foil, and polyethylene film composited by a two-component adhesive. It is opaque, has good light-shielding properties, low permeability, good air tightness, low adsorption, stable chemical properties, and high mechanical strength. Figure 6 The bag mainly comprises an aluminum foil bag body 7.1, an air inlet valve 7.2 and an air outlet valve 7.3. The air inlet of the upper end of the aluminum foil bag body 7.1 is provided with the air inlet valve 7.2, and the air outlet of the lower end is provided with the air outlet valve 7.3, so that it is convenient to charge, discharge and replace air.

[0048] The above is only a preferred embodiment of the utility model. Any person skilled in the art may modify the utility model by using the above technical solution or modify it into an equivalent technical solution. Therefore, any simple modification or equivalent transformation based on the technical solution of the utility model shall fall within the scope of protection claimed by the utility model.

Claims

1. A fully enclosed gas sampling device at the wellhead of an oil well, characterized by: The invention comprises a sampling device base (1), a gas extraction device (3), a sampling tube (4), a control valve (5), a gas buffer (6), a gas sampling bag (7), a gas purifier (8), a hydraulic pipeline (10), and a hydraulic pump (11). The gas extraction device (3) and the hydraulic pump (11) are installed on the upper surface of the sampling device base (1); the bottom of the gas extraction device (3) is connected to the sampling valve through the sampling tube (4); the top of the gas extraction device (3) is connected to the input end of the gas buffer (6) through the pipeline and the control valve (5); the output end of the gas buffer (6) is connected to the gas inlet of the gas sampling bag (7) through the pipeline; the gas outlet of the gas sampling bag (7) is connected to the gas purifier (8) through the pipeline; and one side of the top of the gas extraction device (3) is connected to the hydraulic pump (11) through the hydraulic pipeline (10).

2. The fully enclosed gas sampling device for oil wellhead according to claim 1, characterized in that: The gas extraction device (3) comprises a bottom plate (3.1), fixing screws (3.2), an oil and gas inlet (3.4), a gas sampling tube (3.5), a movable piston (3.7), and a magnetic flap level meter. The bottom of the gas sampling tube (3.5) is fixed with the bottom plate (3.1), the middle of the bottom plate (3.1) is provided with an oil and gas inlet (3.4), and the outer side of the bottom plate (3.1) is connected to the sampling device base (1) via fixing screws (3.2); the movable piston (3.7) is installed in the inner cavity of the gas sampling tube (3.5), and a magnetic flap level meter is installed on the gas sampling tube (3.5); and a gas sampling outlet (3.11) is provided at the top of the movable piston (3.7).

3. The fully enclosed gas sampling device for oil wellhead according to claim 2, characterized in that: The magnetic flap liquid level meter comprises a magnetic float (3.6) and a liquid level display board (3.10); the magnetic float (3.6) is arranged in the middle inner cavity of the movable piston (3.7); and the liquid level display board (3.10) is installed on one side of the top of the gas sampling cylinder (3.5).

4. The fully enclosed gas sampling device for oil wellhead according to claim 3 is characterized by: The movable piston (3.7) comprises a lower piston extension body (3.7.1) and an upper piston body (3.7.2); a protruding lower piston extension body (3.7.1) is provided at the lower end of the upper piston body (3.7.2); and an oil and gas storage chamber (3.7.3) is provided in the inner cavity of the upper piston body (3.7.2).

5. The fully enclosed gas sampling device for oil wellhead according to claim 4 is characterized in that: The magnetic float (3.6) is installed in the oil and gas storage chamber (3.7.3) of the inner chamber of the upper piston body (3.7.2).

6. A fully enclosed gas sampling device at the wellhead of an oil well according to claim 4 or 5, characterized in that: A back pressure port (3.8) is provided at the top of the gas collection cylinder (3.5).

7. The fully enclosed gas sampling device for oil wellhead according to claim 6, characterized in that: An upper sealing ring (3.9) is arranged on the outer side of the upper piston body (3.7.2).

8. The fully enclosed gas sampling device for oil wellhead according to claim 7, characterized in that: A lower sealing ring (3.3) is provided on the outer side of the lower piston extension body (3.7.1).

9. The fully enclosed gas sampling device for oil wellhead according to claim 2, characterized in that: A roller (2) is provided at the bottom of the sampling device base (1), and a pressure gauge (9) is installed at the top of the movable piston (3.7).

10. The fully enclosed gas sampling device for oil wellhead according to claim 1, characterized in that: The gas purifier (8) comprises a sealed container (8.1), a purification liquid (8.2), a mixed gas input pipe (8.3), and a clean gas output pipe (8.4); the sealed container (8.1) is provided with the purification liquid (8.2); the mixed gas input pipe (8.3) is inserted into the purification liquid (8.2); and the lower end of the clean gas output pipe (8.4) is located above the purification liquid (8.2) in the sealed container (8.1).

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