Mixed sampling detection system and mixed sampling method for closed reinjection of high-pressure wellhead flow

Abstract

The invention relates to the technical field of high-pressure well oil gas detection, and discloses a mixed sampling detection system and a mixed sampling method for high-pressure well mouth flow closed reinjection, the mixed sampling detection system comprises an oil nozzle manifold, an upstream pipe is arranged at one end of the oil nozzle manifold, a downstream pipe is arranged at the other end of the oil nozzle manifold, and the mixed sampling detection system further comprises a displacement tank, a movable piston is arranged in the displacement tank, a first connecting port and a second connecting port are formed in the displacement tank, a static mixer is installed on the upstream pipe, a sampling pipeline communicated with the upstream pipe is arranged at the downstream position of the static mixer, and the sampling pipeline is communicated with the first connecting port and the gas-liquid separation detection unit. The output end of the gas-liquid separation detection unit is communicated with a second connector, the second connector is further communicated with a reinjection pipeline, and the reinjection pipeline is communicated with a downstream pipe; according to the mixed sampling detection system and method, mixed-phase sampling, separation and reinjection of a high-pressure testing process are achieved, 100% reinjection of a sampled sample is achieved, and the risks of environmental pollution, personal safety and the like are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-pressure well oil and gas detection, in particular, to a high-pressure wellhead process closed-type reinjection mixed sampling detection system and a mixed sampling method. BACKGROUND

[0002] In the oil and gas exploration and testing stage, when the high-pressure oil and gas mixed fluid returns to the ground from the well bottom, it is usually necessary to carry out process sampling to analyze and detect the fluid composition in the process (such as gas component concentration, volume ratio of oil and mud in the liquid, water salinity, etc.), in order to obtain accurate results, representative samples need to be obtained, and the samples after detection (mainly oil and natural gas) are difficult to handle.

[0003] The current high-pressure process mixed sampling detection means commonly used in the operation site is mainly manual sampling detection method, such as gas detection, the on-site operator takes sample from the upstream data head of the nozzle manifold, adjusts the opening degree of the sampling pipeline valve through the manual needle valve, takes the sample into the open sample barrel, and the oil, water, solid particles and other liquid and solid mixture in the sample fall into the sampling barrel, and the gas is discharged from the opening above the sampling barrel to the air environment, and the method of gas detection is to detect the portable detector held at the outlet of the sampling barrel; the liquid and solid sampling is controlled by the same way, and the hand-held sampling glass bottle is used at the outlet of the sampling pipeline to take the sample, and the gas is also diffused from the bottle opening to the air environment, and when the volume of the solid-liquid mixture reaches the required volume (the sampling glass bottle has a scale), the sampling is stopped.

[0004] The above-mentioned sampling method has the following problems:

[0005] 1. The phase state of the fluid in the ground high-pressure process is variable (laminar flow, turbulent flow, slug flow, bubble flow, etc.), and the sample obtained through the sampling port may not be uniformly distributed, which is not representative, resulting in inaccurate detection data;

[0006] 2. The gas diffused into the air environment during sampling is harmful to the health and safety of the on-site personnel, pollutes the environment, and may cause major safety accidents such as explosion and fire, and the liquid (containing oil) after sampling is difficult to handle. SUMMARY

[0007] In order to overcome the defects of the prior art, the present application provides a high-pressure wellhead process closed-type reinjection mixed sampling detection system and a mixed sampling method to solve the above and related problems.

[0008] The technical scheme adopted by the present application to solve its technical problems is: a high-pressure wellhead process closed-type reinjection mixed sampling detection system, comprising a choke manifold, one end of the choke manifold being provided with an upstream pipe and the other end being provided with a downstream pipe, the mixed sampling detection system further comprising a displacement tank, the displacement tank being provided with a movable piston, the displacement tank being provided with a first connecting port and a second connecting port, the upstream pipe being provided with a static mixer, the static mixer being provided with a sampling pipeline connected with the upstream pipe downstream, the sampling pipeline being connected with the first connecting port and a gas-liquid separation detection unit respectively, the output end of the gas-liquid separation detection unit being connected with the second connecting port, the second connecting port being further connected with a reinjection pipeline, and the reinjection pipeline being connected with the downstream pipe.

[0009] In the high-pressure wellhead process closed-type reinjection mixed sampling detection system, the gas-liquid separation detection unit comprises a low-pressure gas-liquid separation tank and a sampling branch pipeline connected with the sampling pipeline, the input end of the low-pressure gas-liquid separation tank being connected with the sampling branch pipeline, the gas output end of the low-pressure gas-liquid separation tank being connected with a gas detection chamber through a gas pipeline, the output end of the gas detection chamber being connected with a gas-liquid mixing pipeline through a first one-way valve, the liquid output end of the low-pressure gas-liquid separation tank being connected with a liquid detection chamber through a liquid pipeline, the output end of the liquid detection chamber being connected with the gas-liquid mixing pipeline through a second one-way valve, and the gas-liquid mixing pipeline being connected with the reinjection pipeline through a fifth electrically-controlled needle valve.

[0010] In the high-pressure wellhead process closed-type reinjection mixed sampling detection system, the input end of the low-pressure gas-liquid separation tank is further connected with a nitrogen purge pipeline, and the nitrogen purge pipeline is connected with a nitrogen generator through a seventh electrically-controlled needle valve at the end thereof.

[0011] In the high-pressure wellhead process closed-type reinjection mixed sampling detection system, the sampling pipeline is sequentially provided with a first manual needle valve, a choke nozzle and a first electrically-controlled needle valve from the upstream to the downstream of gas-liquid transportation, and the reinjection pipeline is sequentially provided with a sixth electrically-controlled needle valve, a third one-way valve and a second manual needle valve from the upstream to the downstream of gas-liquid transportation.

[0012] In the high-pressure wellhead process closed-type reinjection mixed sampling detection system, the displacement tank is connected with a hydraulic control system at the end away from the first connecting port and the second connecting port, so that the piston moves in the displacement tank.

[0013] In the high-pressure wellhead process closed-type reinjection mixed sampling detection system, the sampling branch pipeline is provided with a second electrically-controlled needle valve, the gas pipeline is provided with a third electrically-controlled needle valve, and the liquid pipeline is provided with a fourth electrically-controlled needle valve.

[0014] In the above-mentioned hybrid sampling and detection system for closed-loop reinjection at a high-pressure wellhead, a pressure sensor is installed on the second connection port.

[0015] This invention also discloses a mixed sampling method for closed-loop reinjection in high-pressure wellhead processes, including the aforementioned mixed sampling and detection system. The mixed sampling and detection method further includes the following steps:

[0016] S1. Connect the static mixer and sampling line to the upstream pipe of the oil nozzle manifold, and connect the reinjection line to the downstream pipe, so that the fluid reaches a uniform distribution state before entering the sampling line. Before sampling, the first manual needle valve, the second manual needle valve, the first electric needle valve, and the sixth electric needle valve are in the open state, and the second electric needle valve, the fifth electric needle valve, and the seventh electric needle valve are in the closed state, so that the fluid is trapped in the displacement tank.

[0017] S2. When sampling is required, close the first and sixth solenoid valves, and keep the second and fifth solenoid valves closed, so that the fluid in the pipe between the first, second, fifth and sixth solenoid valves is partially blocked. Then, move the piston in the displacement tank downward to expand the space of the displacement tank and reduce the pressure in the pipe until the pressure sensor detects that the pressure has dropped to 2MPa, and then the piston stops moving.

[0018] S3. Open the second, third, fourth, and fifth electrically controlled needle valves to allow the gas in the displacement tank to enter the low-pressure gas-liquid separator under low pressure for gas-liquid separation. At this time, close the second electrically controlled needle valve, and the piston moves further downward to allow the gas in the low-pressure gas-liquid separator to enter the gas detection chamber from the gas pipeline for gas detection, and the liquid in the low-pressure gas-liquid separator to enter the liquid detection chamber from the liquid pipeline for liquid detection.

[0019] S4. The data detected by the gas and liquid are transmitted to the system PLC processing system via the current signal of the monitoring data through the 4-20mA analog signal acquisition method.

[0020] S5. After receiving the data from the system PLC processing system, open the seventh electric control needle valve, start the nitrogen generator to generate nitrogen, so that the nitrogen purge line purges the fluid in the low-pressure gas-liquid separator, gas detection chamber and liquid detection chamber, and discharges into the displacement tank through the gas-liquid mixing line. The purging time is 1 minute, and then the nitrogen generator is stopped.

[0021] S6. Close the fifth and seventh electrically controlled needle valves and open the sixth electrically controlled needle valve. The piston moves upward to discharge the fluid that was purged into the displacement tank to the reinjection line and back to the downstream pipe, thus completing the sampling and sample reinjection process.

[0022] The beneficial effects of this invention are as follows: Before sampling, the fluid can be uniformly distributed within a certain range using a static mixer, ensuring that samples obtained within that range represent the fluid characteristics at that moment; by utilizing the piston movement within the displacement tank, a pressure differential is easily formed within the pipeline, allowing the homogenized fluid to enter the gas-liquid separation and detection unit for separate gas and liquid detection. Simultaneously, the separated gas and liquid can be converged into the reinjection pipeline, allowing the detected gas and liquid to re-enter the main flow of the downstream pipeline without reprocessing. This achieves mixed-phase sampling, separation, and reinjection in a high-pressure testing process, ensuring that representative samples are obtained to create conditions for accurate detection results, and achieving 100% sample reinjection, avoiding risks such as environmental pollution and personal safety; moreover, the mixed sampling and detection method of this invention allows the fluid in the sampling pipeline to maintain a continuous flow state in the unsampling state, thereby ensuring that representative samples of the fluid at that moment are obtained during sampling, guaranteeing the timeliness and accuracy of the test data. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the hybrid sampling and detection system of the present invention.

[0024] In the diagram: Static mixer 1, upstream pipe 2, nozzle manifold 3, downstream pipe 4, first manual needle valve 5, sampling line 6, throttle nozzle 7, first electrically controlled needle valve 8, sampling branch line 9, second electrically controlled needle valve 10, low-pressure gas-liquid separator 11, gas line 12, third electrically controlled needle valve 13, gas detection chamber 14, first check valve 15, liquid line 16, fourth electrically controlled needle valve 17, liquid detection chamber 18, second check valve 19, gas-liquid mixing line 20, fifth electrically controlled needle valve 21, reinjection line 22, sixth electrically controlled needle valve 23, third check valve 24, second manual needle valve 25, displacement tank 26, piston 27, hydraulic control system 28, pressure sensor 29, nitrogen generator 30, seventh electrically controlled needle valve 31, nitrogen purging line 32. Detailed Implementation

[0025] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] like Figure 1The mixed sampling and detection system for a closed-loop reinjection process at a high-pressure wellhead, as shown, includes an oil nozzle manifold 3, with an upstream pipe 2 at one end and a downstream pipe 4 at the other. The system also includes a displacement tank 26, within which a movable piston 27 is installed. The displacement tank 26 has a first connection port and a second connection port. A static mixer 1 is installed on the upstream pipe 2. A sampling pipeline 6, connected to the upstream pipe 2, is located downstream of the static mixer 1. The sampling pipeline 6 is connected to both the first connection port and a gas-liquid separation detection unit. The output of the gas-liquid separation detection unit is connected to the second connection port, which is also connected to the reinjection pipeline 22. The reinjection pipeline 22 is connected to the downstream pipe 4. This embodiment... Before sampling, the fluid can be uniformly distributed in a certain range using a static mixer 1, ensuring that the samples obtained in that range represent the fluid characteristics at that moment. By utilizing the piston movement within the displacement tank 26, a pressure difference is easily formed in the pipeline, allowing the homogenized fluid to enter the gas-liquid separation and detection unit for separate gas and liquid detection. Simultaneously, the separated gas and liquid can be converged into the reinjection pipeline 22, allowing the detected gas and liquid to re-enter the main flow of the downstream pipe 4 without reprocessing. This achieves high-pressure process mixed-phase sampling, separation, and reinjection, ensuring that representative samples are obtained to create conditions for accurate detection results, and achieving 100% sample reinjection, avoiding risks such as environmental pollution and personal safety.

[0027] It is worth noting that the upper part of the piston 27 and the upper part of the displacement tank 26 are provided with liquid flow channels so that after the piston 27 moves upward to its maximum stroke, the liquid can flow out from the liquid flow channels into the reinjection line 22.

[0028] The gas-liquid separation and detection unit of this embodiment includes a low-pressure gas-liquid separator 11 and a sampling branch line 9 connected to the sampling line 6. The input end of the low-pressure gas-liquid separator 11 is connected to the sampling branch line 9. The gas output end of the low-pressure gas-liquid separator 11 is connected to the gas detection chamber 14 through the gas line 12. The output end of the gas detection chamber 14 is connected to the gas-liquid mixing line 20 through the first one-way valve 15. The liquid output end of the low-pressure gas-liquid separator 11 is connected to the liquid detection chamber 18 through the liquid line 16. The output end of chamber 18 is connected to gas-liquid mixing pipeline 20 through the second one-way valve 19. Gas-liquid mixing pipeline 20 is connected to reinjection pipeline 22 through the fifth electrically controlled needle valve 21. Thus, fluid can enter the low-pressure gas-liquid separator 11 for gas-liquid separation. Gas enters gas detection chamber 14 for detection, and liquid enters liquid detection chamber 18 for detection. Moreover, the detected gas and liquid can enter the reinjection pipeline 22 to converge and return to the main process of downstream pipe 4. There is no need to process the detected sample, thus reducing processing costs.

[0029] In this embodiment, the input end of the low-pressure gas-liquid separator 11 is also connected to a nitrogen purging line 32. The end of the nitrogen purging line 32 is connected to a nitrogen generator 30 through a seventh electrically controlled needle valve 31. The nitrogen generator 30 is used to generate nitrogen, so as to facilitate the purging of the interior of the low-pressure gas-liquid separator 11, the gas detection chamber 14 and the liquid detection chamber 18 with nitrogen, so as to prevent affecting the accuracy of the next sample test.

[0030] In this embodiment, the sampling pipeline 6 is sequentially equipped with a first manual needle valve 5, a throttle nozzle 7, and a first electrically controlled needle valve 8 in the direction from upstream to downstream of the gas-liquid transport. The reinjection pipeline 22 is sequentially equipped with a sixth electrically controlled needle valve 23, a third check valve 24, and a second manual needle valve 25 in the direction from upstream to downstream of the gas-liquid transport. The throttle nozzle 7 is used to control the sampling flow rate so as to control the connection or closure between pipelines. This allows the displacement tank 26 to control the pressure difference in the closed loop during the movement of the piston 27, so that the relevant fluid, gas, or liquid can enter the next pipeline.

[0031] It is worth noting that, in this embodiment, the end of the displacement tank 26 away from the first connection port and the second connection port is connected to a hydraulic control system 28, which causes the piston 27 to move inside the displacement tank 26; thereby, the internal space of the displacement tank 26 can be expanded or reduced to change the pressure difference in the pipeline.

[0032] In this embodiment, a second electrically controlled needle valve 10 is provided on the sampling branch line 9, a third electrically controlled needle valve 13 is provided on the gas line 12, and a fourth electrically controlled needle valve 17 is provided on the liquid line 16, so as to control the connection or closure of the relevant lines.

[0033] It is worth noting that a pressure sensor 29 is provided on the second connection port in this embodiment; the pressure sensor 29 is used to detect the pressure of the pipeline connected to the displacement tank 26.

[0034] This embodiment also discloses a mixed sampling method for closed-loop reinjection at high-pressure wellheads, including the aforementioned mixed sampling and detection system. The mixed sampling and detection method further includes the following steps:

[0035] S1. The upstream pipe 2 of the nozzle manifold 1 is connected to the static mixer 1 and the sampling line 6, and the downstream pipe 4 is connected to the reinjection line 22, so that the fluid reaches a uniform distribution state before entering the sampling line 6. With the cooperation of the nozzle manifold 1 and the throttling nozzle, a certain pressure difference is formed between the upstream pipe 2 and the downstream pipe 4, thereby maintaining a continuous flow state. The static mixer 1 is used to mix the oil and gas mixture in the process and achieve a uniform distribution state. Before sampling, the piston 27 is at the top of the displacement tank 26, the first manual needle valve 5, the second manual needle valve 25, the first electric needle valve 8, and the sixth electric needle valve 23 are in the open state, and the second electric needle valve 10, the fifth electric needle valve 21, and the seventh electric needle valve 31 are in the closed state, so that the fluid is trapped in the displacement tank 26.

[0036] S2. When sampling is required, close the first solenoid valve 8 and the sixth solenoid valve 23, and keep the second solenoid valve 10 and the fifth solenoid valve 21 closed, so that the fluid in the pipe between the first solenoid valve 8, the second solenoid valve 10, the fifth solenoid valve 21 and the sixth solenoid valve 23 is partially blocked. Then, the piston 27 in the displacement tank 26 is moved downward, so that the space of the displacement tank 26 is expanded and the pressure in the pipe is reduced until the pressure sensor 29 detects that the pressure has dropped to 2MPa, and then the piston 27 stops moving.

[0037] S3. Open the second electrically controlled needle valve 10, the third electrically controlled needle valve 13, the fourth electrically controlled needle valve 17 and the fifth electrically controlled needle valve 21, so that the gas in the displacement tank 26 enters the low-pressure gas-liquid separator 11 under low pressure for gas-liquid separation. At this time, close the second electrically controlled needle valve 10, and at the same time, the piston 27 moves further downward, so that the gas in the low-pressure gas-liquid separator 11 enters the gas detection chamber 14 from the gas pipeline 12 for gas detection, and the liquid in the low-pressure gas-liquid separator 11 enters the liquid detection chamber 18 from the liquid pipeline 16 for liquid detection.

[0038] S4. The data detected by the gas and liquid are transmitted to the system PLC processing system via the current signal of the monitoring data through the 4-20mA analog signal acquisition method.

[0039] S5. After receiving the data from the system PLC processing system, open the seventh electric control needle valve 31 and start the nitrogen generator 30 to generate nitrogen. The nitrogen will purge the fluid in the low-pressure gas-liquid separator 11, gas detection chamber 14 and liquid detection chamber 18 from the nitrogen purging pipeline 32, and then be discharged into the displacement tank 26 through the gas-liquid mixing pipeline 20. The purging time is 1 minute. After 1 minute, stop the nitrogen generator 30.

[0040] S6. Close the fifth solenoid valve 21 and the seventh solenoid valve 31, open the sixth solenoid valve 23, and move the piston 27 upward to discharge the fluid that was purged into the displacement tank 26 to the reinjection line 22 and back to the downstream pipe 4, thus completing the sampling and sample reinjection process.

[0041] The mixed sampling and detection method of the present invention can keep the fluid in the sampling pipeline in the non-sampling state continuously flowing, thereby ensuring that a representative sample in the fluid can be obtained at the current time, ensuring the timeliness and accuracy of the test data. The whole process realizes mixed sampling, separation and reinjection of high pressure test process, and achieves 100% reinjection of sampled samples, avoiding risks such as environmental pollution and personal safety.

[0042] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A mixed sampling and detection system for closed-loop reinjection at high-pressure wellheads, comprising an oil nozzle manifold (3), wherein one end of the oil nozzle manifold (3) has an upstream pipe (2) and the other end has a downstream pipe (4), characterized in that, It also includes a displacement tank (26), which is equipped with a movable piston (27). The displacement tank (26) is provided with a first connection port and a second connection port. A static mixer (1) is installed on the upstream pipe (2). A sampling line (6) connected to the upstream pipe (2) is provided downstream of the static mixer (1). The sampling line (6) is connected to the first connection port and the gas-liquid separation detection unit respectively. The output end of the gas-liquid separation detection unit is connected to the second connection port. The second connection port is also connected to the reinjection line (22). The reinjection line (22) is connected to the downstream pipe (4).

2. The mixed sampling and detection system for closed-loop reinjection at high-pressure wellheads according to claim 1, characterized in that, The gas-liquid separation detection unit includes a low-pressure gas-liquid separator (11) and a sampling branch line (9) connected to the sampling line (6). The input end of the low-pressure gas-liquid separator (11) is connected to the sampling branch line (9). The gas output end of the low-pressure gas-liquid separator (11) is connected to the gas detection chamber (14) through the gas line (12). The output end of the gas detection chamber (14) is connected to the gas-liquid mixing line (20) through the first one-way valve (15). The liquid output end of the low-pressure gas-liquid separator (11) is connected to the liquid detection chamber (18) through the liquid line (16). The output end of the liquid detection chamber (18) is connected to the gas-liquid mixing line (20) through the second one-way valve (19). The gas-liquid mixing line (20) is connected to the reinjection line (22) through the fifth electrically controlled needle valve (21).

3. The mixed sampling and detection system for closed-loop reinjection at high-pressure wellheads according to claim 2, characterized in that, The input end of the low-pressure gas-liquid separator (11) is also connected to a nitrogen purging pipeline (32), and the end of the nitrogen purging pipeline (32) is connected to a nitrogen generator (30) through a seventh electrically controlled needle valve (31).

4. The mixed sampling and detection system for closed-loop reinjection at high-pressure wellheads according to claim 3, characterized in that, The sampling pipeline (6) is provided with a first manual needle valve (5), a throttle nozzle (7) and a first electrically controlled needle valve (8) in sequence from upstream to downstream of the gas-liquid transport. The reinjection pipeline (22) is provided with a sixth electrically controlled needle valve (23), a third check valve (24) and a second manual needle valve (25) in sequence from upstream to downstream of the gas-liquid transport.

5. The mixed sampling and detection system for closed-loop reinjection at high-pressure wellheads according to claim 1, characterized in that, The displacement tank (26) is connected to a hydraulic control system (28) at the end away from the first and second connection ports, so that the piston (27) moves inside the displacement tank (26).

6. The mixed sampling and detection system for closed-loop reinjection at high-pressure wellheads according to claim 4, characterized in that, A second electrically controlled needle valve (10) is provided on the sampling branch line (9), a third electrically controlled needle valve (13) is provided on the gas line (12), and a fourth electrically controlled needle valve (17) is provided on the liquid line (16).

7. The mixed sampling and detection system for closed-loop reinjection at high-pressure wellheads according to claim 4, characterized in that, A pressure sensor (29) is provided on the second connection port.

8. A mixed sampling and detection method for closed-loop reinjection at high-pressure wellheads, comprising the mixed sampling and detection system as described in any one of claims 1-7, characterized in that, This pooled sampling method also includes the following steps: S1. Connect the static mixer (1) and sampling line (6) to the upstream pipe (2) of the oil nozzle manifold (1), and connect the downstream pipe (4) to the reinjection line (22) so that the fluid reaches a uniform distribution state before entering the sampling line (6). Before sampling, the first manual needle valve (5), the second manual needle valve (25), the first electric needle valve (8), and the sixth electric needle valve (23) are in the open state, and the second electric needle valve (10), the fifth electric needle valve (21), and the seventh electric needle valve (31) are in the closed state, so that the fluid is trapped inside the displacement tank (26). S2. When sampling is required, close the first solenoid valve (8) and the sixth solenoid valve (23), and keep the second solenoid valve (10) and the fifth solenoid valve (21) closed, so that the fluid in the pipe between the first solenoid valve (8), the second solenoid valve (10), the fifth solenoid valve (21) and the sixth solenoid valve (23) is partially blocked. Then, the piston (27) in the displacement tank (26) is moved downward, so that the space of the displacement tank (26) is expanded and the pressure in the pipe is reduced until the pressure sensor (29) detects that the pressure has dropped to 2MPa, and then the piston (27) stops moving. S3. Open the second, third, fourth, and fifth electrically controlled needle valves (10, 13, 17, 21) so that the gas in the displacement tank (26) enters the low-pressure gas-liquid separator (11) under low pressure for gas-liquid separation. At this time, close the second electrically controlled needle valve (10) and the piston (27) moves further downward so that the gas in the low-pressure gas-liquid separator (11) enters the gas detection chamber (14) from the gas pipeline (12) for gas detection and the liquid in the low-pressure gas-liquid separator (11) enters the liquid detection chamber (18) from the liquid pipeline (16) for liquid detection. S4. The data detected by the gas and liquid are transmitted to the system PLC processing system via the current signal of the monitoring data through the 4-20mA analog signal acquisition method. S5. After receiving the data from the system PLC processing system, open the seventh electric control needle valve (31) and start the nitrogen generator (30) to generate nitrogen. The nitrogen will purge the fluid in the low-pressure gas-liquid separator (11), gas detection chamber (14) and liquid detection chamber (18) through the nitrogen purging pipeline (32), and then be discharged into the displacement tank (26) through the gas-liquid mixing pipeline (20). The purging time is 1 minute, and then the nitrogen generator (30) is stopped. S6. Close the fifth solenoid needle valve (21) and the seventh solenoid needle valve (31), open the sixth solenoid needle valve (23), and move the piston (27) upward to discharge the fluid that was purged into the displacement tank (26) to the reinjection line (22) and back to the downstream pipe (4), thus completing the sampling and sample reinjection process.

Images