Split-type closed gas sampling device suitable for oil well

Abstract

The application provides a split type closed gas sampling device suitable for oil pumping wells, and belongs to the technical field of oil field oil and gas loss monitoring. The technical scheme is as follows: a hollow container is provided, a through hole one for placing a pumping rod is arranged at the center of the upper end surface of the container, a through hole two for placing a packing box is arranged at the center of the lower end surface of the container, and an annular plate one is concentrically arranged at the edge of the through hole one on the upper end surface of the container; an outward expanding annular plate is concentrically arranged outside the annular plate one, an annular sealing assembly is concentrically arranged inside the outward expanding annular plate, and a plurality of mounting holes are reserved on the container; the container, the annular plate one, the annular plate two, the outward expanding annular plate and the annular sealing assembly are all divided into two parts in an axis symmetry mode, a connecting plate is symmetrically arranged outside the opposite surface of each part of the container, and an ear plate is symmetrically arranged outside the opposite surface of each part of the outward expanding annular plate. The application has the beneficial effect of realizing safe and effective sampling of wellhead gas.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas loss monitoring in oil fields, and particularly relates to a split type sealed gas sampling device suitable for pumping wells. BACKGROUND

[0002] It is of great significance to monitor the oil and gas loss of typical emission sources, master the real data of oil and gas loss, and take corresponding treatment measures. As one of the typical emission sources, wellhead fugitive gas lacks effective equipment for collection and monitoring. Foreign countries use satellites, unmanned aerial vehicles and other remote sensing to monitor leakage data in the region, and single well data is not used for fine management. Domestic countries also lack corresponding research and devices. Therefore, it is necessary to develop a wellhead sealed gas sampling device to realize effective detection and identification of loss gas.

[0003] Oil and gas production and transportation in oilfield enterprises will result in a large amount of oil and gas loss. Methane, as the main component of loss gas, is the second largest greenhouse gas after carbon dioxide, which greatly reduces the contribution of carbon dioxide reduction brought by "gas instead of coal" and "gas instead of oil" projects. At present, oil and gas loss mainly occurs in the upstream oil and gas field production process, and unorganized emission including leakage at the packing ring and other places is difficult to find out.

[0004] At present, the price of related sampling tools is relatively high, and impurities are easy to enter the internal pipeline, which is prone to blockage. Sometimes the internal filter needs to be cleaned once every few hours, and it is only suitable for low-viscosity, low-density crude oil and crude oil or finished oil with few impurities; secondary separation is required, which wastes labor. SUMMARY

[0005] The purpose of the present application is to provide a split type sealed gas sampling device for realizing safe and effective sampling of wellhead gas.

[0006] The present application is realized by the following measures: a split type sealed gas sampling device suitable for pumping wells, characterized in that it comprises a hollow container, a through hole one for placing a pumping rod is arranged at the center of the upper end surface of the container, a through hole two for placing a packing box is arranged at the center of the lower end surface of the container, and an annular plate one is concentrically arranged at the edge of the through hole one on the upper end surface of the container.

[0007] An outwardly expanding annular plate is concentrically arranged outside the annular plate one, an annular sealing assembly is concentrically arranged inside the outwardly expanding annular plate, a plurality of mounting holes are reserved on the container, and the mounting holes can be used to mount a vacuum pump, a safety valve and a sampling device.

[0008] The container, the annular plate one, the annular plate two, the outer expansion annular plate and the annular sealing assembly are divided into two parts in axial symmetry, the outer side of the opposite face of each part of the container is symmetrically provided with a connecting plate, the connecting plate is connected with the annular plate one and the annular plate two, the outer side of the opposite face of each part of the outer expansion annular plate is symmetrically provided with an ear plate;

[0009] The opposite two connecting plates and the opposite two ear plates are connected through bolts.

[0010] The annular sealing assembly comprises three sealing rings, each of which is formed by inserting two semicircular rings, two end faces of the two semicircular rings are provided with a plug column and a plug slot respectively.

[0011] A compression ring is provided on the inner wall of the outer expansion annular plate above the annular sealing assembly through threaded connection, the compression ring is arranged in the outer expansion annular plate through threaded connection and can press the annular sealing assembly on the upper end face of the annular plate one, the compression ring is composed of two symmetrical annular parts, and two circular holes are arranged in each of the annular parts. Preferably, the inner diameter of the two circular holes is 4mm and the interval is 60 degrees. The compression ring can be rotated and pressed down by using a matching wrench.

[0012] An annular groove is arranged on the inner wall of the upper and lower sealing rings. The depth of the annular groove is 1mm and the height is 5mm, which can be used for applying lubricating grease and further sealing the device.

[0013] A U-shaped outer support rod is arranged on the outer wall of each part of the container, the open end of the U-shaped outer support rod is inserted into the upper and lower end faces of the container and is cross-distributed with the connecting plates, and the lower end face of the outer expansion annular plate is placed on the U-shaped outer support rod.

[0014] A flexible plate composed of two semicircular rings is concentrically arranged on the outer side of the annular plate two, and the flexible plate is made of flexible and air-tight material.

[0015] Four clamping grooves one in communication with the annular plate one are arranged on the upper end face of the container, and four clamping grooves two in communication with the annular plate two are arranged on the lower end face of the container, and the four clamping grooves one and the four clamping grooves two are cross-distributed.

[0016] The upper part of the two connecting plates and the U-shaped outer support rod in contact with each other are inserted into the clamping grooves one, and the lower part of the two connecting plates and the U-shaped outer support rod in contact with each other are inserted into the clamping grooves two.

[0017] A rectangular plate is arranged between the connecting plate and the container, a rectangular groove for placing the rectangular plate is arranged on the container, and the rectangular plate is arranged in the rectangular groove.

[0018] The upper part of the connecting plate is fixedly connected with the annular plate one, and the lower part of the connecting plate is fixedly connected with the annular plate two;

[0019] The upper part of the U-shaped outer supporting rod is fixedly connected with the annular plate one, and the lower part of the connecting plate is fixedly connected with the annular plate two.

[0020] The inner diameter of the middle sealing ring is slightly larger than the inner diameter of the upper and lower sealing rings. The inner diameter of the upper and lower sealing rings is 1mm smaller than the inner diameter of the middle sealing ring, so that the friction force can be prevented from being too large.

[0021] The working surfaces of the two parts of the container are provided with grooves, and sealing strips are arranged in the grooves.

[0022] Preferably, the outer diameter of the compression ring is 60mm, the inner diameter is 42mm, the height is 10mm, and the pitch of the compression ring is 1.5mm. The whole is processed with a thread, and then the workpiece is cut open with a wire cutting.

[0023] Working principle: according to the diameter of the sucker rod, the corresponding inner diameter of the container is selected, the annular sealing assembly is assembled, and an appropriate amount of lubricating grease is applied in the upper and lower annular grooves, then the outer expansion annular plate is put in, two sealing strips are put into the grooves respectively, then the lug plate and the connecting plate are connected through bolts, and then the annular sealing assembly is compressed tightly by tightening the compression ring;

[0024] After installation is completed, the flexible ring is wrapped and tightened with sealing strips and nylon straps and installed at the packing box, and an appropriate amount of sealant is applied; one of the installation holes is connected with a gas sampling bottle / bag through a sampling pipe, and one of the installation holes is connected with a hand vacuum pump through a pipeline; one installation hole is connected with a safety valve; after installation is completed, the inside of the sampling device is pumped into a near vacuum by using a hand vacuum pump and the valve is closed, the oil well is operated for a period of time, the valve at the sampling bottle is opened and the collection of oil well overflow gas is started, when the pressure indication of the sampling bottle reaches the required value, the timing is stopped and the valve is closed to complete the collection, the oil well is stopped and the sampling device is disassembled, and the collection of oil well overflow gas is completed.

[0025] On the basis of the above, a detection method for the leakage rate of oil and gas at the wellhead of an oil pumping well is provided, which specifically comprises:

[0026] The sampling device starts collecting gas and timing, and after the gas collection is completed, the leakage rate of oil and gas at the wellhead of the oil pumping well is determined by superimposing calculation of the gas state equation and the leakage rates of the dynamic seal and the static seal according to parameters such as the volume, pressure and gas collection time of the gas sampling bottle.

[0027] The static seal in the determination device is at the flexible plate, and the dynamic seal is at the annular sealing assembly.

[0028] The dynamic sealing part cooperates with the sucker rod, and the eccentric wear problem in the actual work of the sucker rod is considered, so the leakage of the reciprocating sealing section can be calculated according to the annular gap flow formula. The annular gap flow leakage rate formula is:

[0029] (1);

[0030] Wherein is the dynamic viscosity of the fluid, is the radius gap between the sucker rod and the dynamic sealing part, is the pressure difference between the inside and outside of the sampling tool, is the cross-sectional diameter of the sucker rod, is the sealing length between the sucker rod and the dynamic sealing part, and the above parameters can be detected or measured by using the existing technology, which will not be described here.

[0031] The static sealing part: the leakage rate of the static sealing is calculated according to the porous medium model. The non-metallic gasket material can be approximately regarded as an isotropic porous medium, and its flow channel is composed of a network of curved and radius-different capillary tubes. The flow state of gas through the porous medium can be divided into laminar flow and molecular flow, and its flow rate is the sum of the laminar flow rate and the molecular flow rate. The leakage rate equation of the gas through the sealing part is:

[0032] (2);

[0033] In the formula, is the regression coefficient (obtained by experiment fitting, which comprehensively reflects the number and diameter of the leakage channel), is the leakage rate, is the medium viscosity, b is the flow channel length, is the stress of the sealing part, is the molecular weight of the gas, is the absolute temperature of the gas, , , are the pressures inside and outside the gasket respectively.

[0034] When the equipment is connected to the gas collection bottle and the valve is opened, the time is started to be recorded, and the pressure and temperature parameters are recorded at the same time. After the gas collection is completed, the valve is closed and the time recording is stopped. According to the volume, pressure and gas collection time of the gas sampling bottle, the leakage amount of the collected gas is calculated by the gas state equation, and the leakage rate of the dynamic sealing and static sealing parts is superimposed to calculate the leakage rate of the oil well head gas.

[0035] According to the gas state equation, the leakage rate of the detected pipe flange can be calculated, and the formula derivation is as follows:

[0036] Let the leakage space volume (sampling bottle volume) at the beginning of measurement be , the pressure is , the temperature is , the number of moles of the leaked gas is , wherein, is the universal gas constant. If the pressure of the leakage space at the final measurement time is , the temperature is , the number of moles of the leaked gas is: (the volume of the sampling bottle

[0037] is constant).

[0038] Therefore, the number of moles of the leaked gas is: (3)

[0039] The leaked volume under the standard state is: (4), wherein , are the atmospheric pressure and the temperature under the standard state respectively.

[0040] If the measurement time is , the volume leakage rate is: (5)

[0041] The leakage rates of the formulas (1), (2) and (5) are added to obtain the gas leakage rate of the single well mouth

[0042] (6)

[0043] The static sealing of the sealing strip is also considered for the static sealing of the sealing strip. The leakage rate equation of the gas passing through the sealing piece of the sealing strip can be calculated by using the formula (2) in Embodiment 5.

[0044] Compared with the prior art, the beneficial effects of the present application are that the well mouth gas can be safely and effectively sampled, the structure is relatively simple, the manufacturing cost is low, the installation is convenient, the use is convenient, the in-service well mouth gas can be sampled on site, and the like. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a schematic diagram of the overall structure of the embodiment of the present application.

[0046] Figure 2 is a schematic diagram of the structure of the outer shell after being cut open in a ring shape.

[0047] Figure 3 is a schematic diagram of the internal structure of the container.

[0048] Figure 4 is a schematic diagram of the structure of part of the symmetrical component.

[0049] Figure 5Structure diagram of the container.

[0050] Figure 6 Structure diagram of the mounting plate, U-shaped outer support rod and the container.

[0051] Figure 7 Structure diagram of half mounting plate and rectangular plate.

[0052] Figure 8 Structure diagram of the ring-shaped sealing assembly.

[0053] Figure 9 Reference diagram in use.

[0054] Wherein, the reference signs are: 1, container; 2, ring-shaped plate one; 3, outer expansion ring-shaped plate; 4, top ring; 5, ring-shaped sealing assembly; 6, connecting plate; 7, rectangular plate; 8, U-shaped outer support rod; 9, ring-shaped plate two; 10, flexible ring; 11, safety valve; 12, sampling tube; 13, sampling bottle; 14, vacuum pump connecting piece; 102, clamping groove one; 103, rectangular groove; 104, mounting hole; 105, clamping groove two; 301, lug plate; 401, round hole; 501, upper sealing ring; 502, middle sealing ring; 503, lower sealing ring; 504, insertion column; 505, insertion groove; 506, ring-shaped groove; 601, groove; 801, handle. DETAILED DESCRIPTION

[0055] To make the technical features of the scheme clear, the scheme will be described below through specific embodiments.

[0056] Embodiment one:

[0057] Reference Figures 1-9 A split type closed gas sampling device suitable for oil pumping wells, comprising a hollow container 1, a through hole one for placing an oil pumping rod is arranged at the center of the upper end surface of the container 1, a through hole two for placing a packing box is arranged at the center of the lower end surface of the container 1, and a ring-shaped plate one 2 is concentrically arranged at the upper end surface of the container 1 and located at the edge of the through hole one;

[0058] An outer expansion ring-shaped plate 3 is concentrically arranged at the outer side of the ring-shaped plate one 2, a ring-shaped sealing assembly 5 is concentrically arranged in the inner part of the outer expansion ring-shaped plate 3, a plurality of mounting holes 104 are reserved on the container 1, the mounting holes 104 can be used for mounting a vacuum pump, a safety valve 11 and a sampling device, and the sampling device can be a sampling bag 13 or a sampling bottle;

[0059] The container 1, the annular plate one 2, the annular plate two 9, the outer expansion annular plate 3 and the annular sealing assembly 5 are divided into two parts in the axis symmetry, the opposite sides of each part of the container 1 are symmetrically provided with the connecting plates 6, the connecting plates 6 are connected with the annular plate one 2 and the annular plate two 9, and the opposite sides of each part of the outer expansion annular plate 3 are symmetrically provided with the ear plates 301.

[0060] The opposite two connecting plates 6 and the opposite two ear plates 301 are connected through bolts.

[0061] The annular sealing assembly 5 comprises three sealing rings, each of which is formed by inserting two semicircular rings, and the two end faces of the two semicircular rings are provided with a plug column 504 and a plug slot 505.

[0062] The inner wall of the outer expansion annular plate 3 and above the annular sealing assembly 5 are provided with a compression ring 4 through threaded connection, the compression ring 4 is arranged in the outer expansion annular plate 3 through threaded connection and can press the annular sealing assembly 5 on the upper end face of the annular plate one 2, the compression ring 4 is composed of two symmetrical annular parts, and the two annular parts are provided with two circular holes 401. Preferably, the inner diameter of the two circular holes 401 is 4mm and the interval is 60 degrees. The compression ring 4 can be rotated and pressed down by using a matching wrench.

[0063] The inner wall of the upper sealing ring 501 and the lower sealing ring 503 is provided with an annular groove 506. The depth of the annular groove 506 is 1mm, and the height is 5mm, which can be used for applying lubricating grease and further sealing the device.

[0064] The outer wall of each part of the container 1 is provided with a U-shaped outer support rod 8, the opening end of the U-shaped outer support rod 8 is inserted into the upper and lower end faces of the container 1 and is cross-distributed with the connecting plates 6, and the lower end face of the outer expansion annular plate 3 is on the U-shaped outer support rod 8.

[0065] The outer side of the annular plate two 9 is concentrically provided with a flexible plate 10 composed of two semicircular rings, and the flexible plate 10 is made of flexible and air-tight material.

[0066] Example two:

[0067] Referring to Figures 1-9 On the basis of example one, the two symmetrical parts of the container 1, the annular plate one 2, the annular plate two 9 and the outer expansion annular plate 3 can be integrally made with the U-shaped outer support rod 8, the connecting plate 6 and the ear plate one 301.

[0068] Example three:

[0069] Referring to Figures 1-9 On the basis of example one, the two symmetrical parts of the container 1, the annular plate one 2 and the annular plate two 9 are integrally made;

[0070] The upper end surface of the container 1 is provided with four clamping grooves 102 communicated with the annular plate 2, and the lower end surface of the container 1 is provided with four clamping grooves 105 communicated with the annular plate 9, and the four clamping grooves 102 and the four clamping grooves 105 are distributed in a cross shape;

[0071] The upper parts of the two connecting plates 6 and the U-shaped outer support rod 8 in contact are inserted into the clamping grooves 102, and the lower parts of the two connecting plates 6 and the U-shaped outer support rod 8 in contact are inserted into the clamping grooves 105;

[0072] The rectangular plate 7 is arranged between the connecting plate 6 and the container 1, and the container 1 is provided with a rectangular groove 103 for placing the rectangular plate 7, and the rectangular plate 7 is arranged in the rectangular groove 103.

[0073] The upper part of the connecting plate 6 is fixedly connected with the annular plate 2, and the lower part of the connecting plate 6 is fixedly connected with the annular plate 9.

[0074] The upper part of the U-shaped outer support rod 8 is fixedly connected with the annular plate 2, and the lower part of the connecting plate 6 is fixedly connected with the annular plate 9.

[0075] The connecting plate 6 and the U-shaped outer support rod 8 can be welded or adhered to the annular plate 2 and the annular plate 9, and the outer expansion annular plate 3 is welded to the annular plate 2.

[0076] In this way, the two parts of the container 1 can be connected through the rectangular plate 7 placed in the rectangular groove 103.

[0077] Because the container will be in contact with associated gas during sampling, corrosion will occur, and the container needs to be replaced regularly, which can reduce the manufacturing cost, and sometimes oil liquid will penetrate, causing residues in the container 1, affecting the sampling effect.

[0078] Example four:

[0079] Referring to Figures 1-9 A split type closed gas sampling device suitable for oil pumping wells, comprising a hollow container 1, a through hole 1 for placing a pumping rod is arranged at the center of the upper end surface of the container 1, a through hole 2 for placing a packing box is arranged at the center of the lower end surface of the container 1, and an annular plate 2 is arranged concentrically at the upper end surface of the container 1 and located at the edge of the through hole 1;

[0080] An outer expansion annular plate 3 is arranged concentrically outside the annular plate 2, an annular sealing assembly 5 is arranged concentrically inside the outer expansion annular plate 3, and a plurality of mounting holes 104 are reserved on the container 1, which can be used to mount a vacuum pump, a safety valve 11 and a sampling device, and the sampling device can be a sampling bag 13 or a sampling bottle;

[0081] The container 1, the annular plate one 2, the annular plate two 9, the outer expansion annular plate 3 and the annular sealing assembly 5 are divided into two parts in the axis symmetry, the opposite sides of each part of the container 1 are symmetrically provided with the connecting plates 6, the connecting plates 6 are connected with the annular plate one 2 and the annular plate two 9, and the opposite sides of each part of the outer expansion annular plate 3 are symmetrically provided with the ear plates 301.

[0082] The opposite two connecting plates 6 and the opposite two ear plates 301 are connected through bolts.

[0083] The annular sealing assembly 5 comprises three sealing rings, each of which is formed by inserting two semicircular rings, and the two end faces of the two semicircular rings are provided with a plug column 504 and a plug slot 505.

[0084] The inner wall of the outer expansion annular plate 3 and above the annular sealing assembly 5 are provided with a compression ring 4 connected through threads, the compression ring 4 is connected through threads in the outer expansion annular plate 3 and can press the annular sealing assembly 5 on the upper end face of the annular plate one 2, the compression ring 4 is composed of two symmetrical annular parts, and the two annular parts are provided with two circular holes 401. Preferably, the inner diameter of the two circular holes 401 is 4mm and the interval is 60 degrees. The compression ring 4 can be rotated and pressed down by using a matching wrench.

[0085] The inner wall of the upper sealing ring 501 and the lower sealing ring 503 is provided with an annular groove 506. The depth of the annular groove 506 is 1mm and the height is 5mm, which can be used for applying lubricating grease and further sealing the device.

[0086] The outer wall of each part of the container 1 is provided with a U-shaped outer support rod 8, the opening end of the U-shaped outer support rod 8 is inserted into the upper and lower end faces of the container 1 and is cross-distributed with the connecting plates 6, and the lower end face of the outer expansion annular plate 3 is on the U-shaped outer support rod 8.

[0087] The outer side of the annular plate two 9 is concentrically provided with a flexible plate 10 composed of two semicircular rings, and the flexible plate 10 is made of flexible and air-tight material.

[0088] The upper end face of the container 1 is provided with four clamping grooves one 102 communicated with the annular plate one 2, and the lower end face of the container 1 is provided with four clamping grooves two 105 communicated with the annular plate two 9, and the four clamping grooves one 102 and the four clamping grooves two 105 are cross-distributed.

[0089] The upper part of the two connecting plates 6 and the U-shaped outer support rod 8 in contact are inserted into the clamping grooves one 102, and the lower part of the two connecting plates 6 and the U-shaped outer support rod 8 in contact are inserted into the clamping grooves two 105.

[0090] The rectangular plate 7 is arranged between the connecting plate 6 and the container 1, the container 1 is provided with a rectangular groove 103 for placing the rectangular plate 7, and the rectangular plate 7 is arranged in the rectangular groove 103.

[0091] The upper part of the connecting plate 6 is fixedly connected with the annular plate one 2, and the lower part of the connecting plate 6 is fixedly connected with the annular plate two 9.

[0092] The upper part of the U-shaped outer supporting rod 8 is fixedly connected with the annular plate one 2, and the lower part of the connecting plate 6 is fixedly connected with the annular plate two 9.

[0093] The connecting plate 6 and the U-shaped outer supporting rod 8 can be welded or adhered to the annular plate one 2 and the annular plate two 9, and the outer expansion annular plate weld 3 is welded to the annular plate one 2.

[0094] The inner diameter of the middle sealing ring 502 is slightly larger than the inner diameters of the upper and lower sealing rings. The inner diameters of the upper and lower sealing rings are 1mm smaller than the inner diameter of the middle sealing ring, so that the friction force can be prevented from being too large.

[0095] The working surfaces of the two parts of the container 1 are provided with grooves 601, and sealing strips are arranged in the grooves 601.

[0096] Preferably, the outer diameter of the compression ring 4 is 60mm, the inner diameter is 42mm, the height is 10mm, and the pitch of the compression ring 4 is 1.5mm. The threads are machined integrally, and then the workpiece is cut open by wire cutting.

[0097] Usage: according to the diameter of the sucker rod, select the container 1 with the corresponding inner diameter, assemble the annular sealing assembly 5, smear an appropriate amount of lubricating grease in the upper and lower annular grooves 506, then put the outer expansion annular plate 3, put the two sealing strips into the grooves 601 respectively, then connect the lug plate 301 and the connecting plate 6 through the bolts, and then tighten the compression ring 4 to press the annular sealing assembly 5 tightly;

[0098] After installation is completed, the flexible ring 10 is wrapped and tightened with the sealing strip and the nylon strap at the packing box, and an appropriate amount of sealant is smeared; one mounting hole 104 is connected with the gas sampling bottle 13 / pack through the sampling pipe 12, and one mounting hole 104 is connected with the manual vacuum pump through the pipeline; one mounting hole 104 is connected with the safety valve 11; after installation is completed, the container is pumped to near vacuum by the manual vacuum pump, and the valve is closed, the oil well is started for a period of time, the valve at the sampling bottle 13 is opened, and the collection of the overflow gas of the oil well is started, when the pressure indication of the sampling bottle 13 reaches the required value, the timing is stopped and the valve is closed to complete the collection, the oil well is stopped and the sampling device is disassembled, and the collection of the overflow gas of the oil well is completed.

[0099] Example five:

[0100] The application is a kind of detection method of oil and gas leakage rate of oil well wellhead based on embodiment four, specifically: the sampling device starts to collect gas and time, after the end of gas collection, according to the volume, pressure and gas sampling bottle collection time and other parameters through the gas state equation and the leakage rate of dynamic sealing and static sealing two parts superposition calculation to determine the leakage rate of oil and gas of oil well wellhead.

[0101] The static sealing and dynamic sealing in the determining device, the static sealing is at the flexible plate, and the dynamic sealing is at the annular sealing assembly;

[0102] The dynamic sealing part cooperates with the sucker rod, considering the eccentric wear problem in the actual work of the sucker rod, therefore, the leakage amount of the reciprocating sealing section can be calculated according to the annular gap flow formula. The annular gap flow leakage rate formula is:

[0103] (1);

[0104] Wherein is the dynamic viscosity of the fluid, is the radius gap between the sucker rod and the dynamic sealing part, is the pressure difference between the inside and outside of the sampling tool, is the cross-sectional diameter of the sucker rod, is the sealing length between the sucker rod and the dynamic sealing part, the above parameters can be detected or measured by using the existing technology, which will not be described here.

[0105] The static sealing part: the static sealing is calculated according to the porous medium model, the porous medium model considers that the non-metal gasket material can be approximately regarded as an isotropic porous medium, and the flow channel is composed of a network of curved, radius different capillary tubes. The flow state of gas through the porous medium can be divided into laminar flow and molecular flow, and the flow rate is the sum of the laminar flow rate and the molecular flow rate. The leakage rate equation of gas through the sealing part is:

[0106] (2);

[0107] In the formula, is the regression coefficient (obtained by experiment fitting, which comprehensively reflects the number and diameter of the leakage channel), is the leakage rate, is the medium viscosity, b is the flow channel length, is the stress of the sealing part, is the molecular weight of the gas, is the absolute temperature of the gas, , , are the pressures inside and outside the gasket respectively.

[0108] When the device is coupled to the gas collection bottle to open the valve, the time is started to be recorded, and the pressure and temperature parameters are recorded at the same time, after the gas collection is completed, the valve is closed and the time recording is stopped. According to the parameters such as the volume, pressure and gas collection time of the gas sampling bottle, the leakage amount of the collected gas is calculated through the gas state equation, and the leakage rate of the dynamic seal and the static seal is superimposed and calculated to determine the leakage rate of the wellhead gas of the oil well.

[0109] According to the gas state equation, the leakage rate of the detected pipe flange can be calculated, and the formula derivation is as follows:

[0110] Let the leakage space volume (sampling bottle volume) at the initial measurement time be , the pressure be , and the temperature be , then the number of moles of the leaked gas is , wherein is a general gas constant. If the pressure of the leakage space at the final measurement time is , and the temperature is , then the number of moles of the leaked gas is: (the sampling bottle volume is constant).

[0111] Therefore, the number of moles of the leaked gas is: (3)

[0112] The standard state leakage volume is converted to: (4), wherein , are the atmospheric pressure and temperature under standard conditions respectively.

[0113] Let the measurement time be , then the volume leakage rate is: (5)

[0114] The leakage rates of formulas (1), (2) and (5) are added to obtain the gas leakage rate of a single wellhead

[0115] (6)

[0116] Example 6:

[0117] On the basis of example 5, the static seal of the sealing strip is preferably also considered. The leakage rate equation of the gas at the sealing strip through the sealing element can be calculated using formula (2) in example 5.

[0118] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0119] In the description of the present application, it is to be understood by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and not indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can be explicitly or implicitly included one or more. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0120] In the description of the present application, it should be noted that unless otherwise specified and limited, the terms "mounting", "connecting", "connecting", "setting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0121] The technical features not described in the present application can be realized by or with the prior art, which will not be repeated here. Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present application should also be within the scope of the present application.

Claims

1. A segmented closed-loop gas sampling device suitable for oil wells, characterized in that, The hollow container is provided with a through hole one for placing a sucker rod at the center of the upper end surface, and a through hole two for placing a packing box at the center of the lower end surface, and a ring-shaped plate one is concentrically arranged at the upper end surface of the container and at the edge of the through hole one. An outer expansion ring-shaped plate is concentrically arranged outside the ring-shaped plate one, and a ring-shaped sealing assembly is concentrically arranged inside the outer expansion ring-shaped plate. A plurality of mounting holes are reserved on the container, which can be used for mounting a vacuum pump, a safety valve and a sampling container. The container, the ring-shaped plate one, the ring-shaped plate two, the outer expansion ring-shaped plate and the ring-shaped sealing assembly are all divided into two parts along the axis, and the opposite sides of each part of the container are symmetrically provided with connecting plates which are connected with the ring-shaped plate one and the ring-shaped plate two. The opposite connecting plates and the opposite ear plates are connected by bolts. The outer side of the ring-shaped plate two is concentrically provided with a flexible plate composed of two semicircular rings, which is made of flexible and air-tight material. The application discloses a method for detecting the leakage rate of oil and gas at the wellhead of an oil pumping well by using a split type closed gas sampling device. The static seal is at the flexible plate, and the dynamic seal is at the ring-shaped sealing assembly. （1）； wherein is the fluid dynamic viscosity, is the radius gap between the sucker rod and the dynamic seal, is the pressure difference between the inside and outside of the sampling tool, is the cross-sectional diameter of the sucker rod, is the sealing length between the sucker rod and the dynamic seal; The dynamic seal part cooperates with the sucker rod, the leakage amount of the reciprocating sealing section is calculated according to the annular gap flow formula, and the annular gap flow leakage rate formula is as follows: （2）； wherein, is a regression coefficient, is a leakage rate, is a medium viscosity, b is a flow path length, is a seal stress, is a gas molecular weight, is a gas absolute temperature, , , are pressures on the inner and outer sides of the gasket, respectively; The static seal part: the leakage rate equation of the gas through the sealing element is as follows: When the device is connected to the gas collection bottle and the valve is opened, the time is started to be recorded, and the pressure and temperature parameters are recorded at the same time. According to the gas state equation, the leakage rate of the detected pipe flange can be calculated, and the volume leakage rate is: (5) After the gas collection is completed, the valve is closed and the time recording is stopped. （6）。 2. The split closure gas sampling device for use in oil wells according to claim 1, characterized in that, The leakage amount of the collected gas is calculated through the gas state equation according to the volume, pressure and gas collection time of the gas sampling bottle, and the leakage rates of the dynamic seal and the static seal are superimposed to calculate the leakage rate of the gas at the wellhead of the oil pumping well.

3. The split closure gas sampling device for use in oil wells according to claim 2, characterized in that, The leakage rates of the formulas (1), (2) and (5) are added to obtain the gas leakage rate of the wellhead of the single well 4. The split-type closed gas sampling device for oil well, according to claim 2, wherein The ring-shaped sealing assembly comprises three sealing rings, each of which is composed of two semicircular rings, and one end surface of each of the two semicircular rings is provided with a plug column, and the other end surface is provided with a plug slot.

5. The split closure gas sampling device for use in oil wells according to claim 2, characterized in that, A compression ring is arranged on the inner wall of the outer expansion ring-shaped plate and above the ring-shaped sealing assembly through threaded connection, the compression ring is arranged in the outer expansion ring-shaped plate through threaded connection and can press the ring-shaped sealing assembly on the upper end surface of the ring-shaped plate one, and the compression ring is composed of two symmetrical ring-shaped parts, and each of the two ring-shaped parts is provided with two circular holes. An annular groove is arranged on the inner wall of the sealing ring at the upper part and the lower part. A U-shaped outer support rod is arranged on the outer wall of each part of the container, the open end of the U-shaped outer support rod is inserted into the upper and lower end surfaces of the container and is cross-distributed with the connecting plates, and the lower end surface of the outer expansion ring-shaped plate is placed on the U-shaped outer support rod.

6. The split-type closed gas sampling device for oil well, according to claim 5, wherein Four clamping grooves one communicated with the annular plate one are arranged on the upper end surface of the container, four clamping grooves two communicated with the annular plate two are arranged on the lower end surface of the container, and the four clamping grooves one and the four clamping grooves two are distributed in a cross shape; The upper portions of the two connecting plates in contact and the U-shaped outer supporting rod are inserted into the clamping grooves one, and the lower portions of the two connecting plates in contact and the U-shaped outer supporting rod are inserted into the clamping grooves two; A rectangular plate is arranged between the connecting plate and the container, a rectangular groove for placing the rectangular plate is arranged on the container, and the rectangular plate is arranged in the rectangular groove.

7. The split closure gas sampling device for use in oil wells according to claim 6, characterized in that, The upper portion of the connecting plate is fixedly connected with the annular plate one, and the lower portion of the connecting plate is fixedly connected with the annular plate two. The upper portion of the U-shaped outer supporting rod is fixedly connected with the annular plate one, and the lower portion of the connecting plate is fixedly connected with the annular plate two.

8. The split-type closed gas sampling device for oil well, according to claim 2, wherein, The inner diameter of the middle sealing ring is slightly larger than the inner diameter of the upper sealing ring.

9. The split-type closed gas sampling device for oil well, according to claim 1, wherein, The working surfaces of the two connecting plates in contact are provided with grooves, and sealing strips are arranged in the grooves.

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