A method for leak detection and pressure test of a gathering system

Abstract

The application discloses a kind of gathering and transportation system leak detection, pressure test method, comprising the following steps: station outside pipeline portion leak detection, pressure test: using fuel gas or nitrogen to station outside pipeline segmented pressure leak detection;Using acid gas to the station outside pipeline is pressurized and leak detection inspection;The station outside pipeline is connected to production state;Station inside pipeline portion leak detection, pressure test: using fuel gas or nitrogen to station inside pipeline leak detection;Using acid gas to the station inside pipeline segmented pressure test, to station inside whole process leak detection;Station inside and outside pipeline is connected, completes gathering and transportation system leak detection, pressure test.This method is used, station outside pipeline is divided into different segments and pressurized leak detection, can determine the location of abnormal leakage point in time, facilitate fast positioning abnormal point, and fast disposal exception, avoid the traditional whole section leak detection need to shut down whole section pipeline, leak point is caused by manpower, material waste, shorten leak detection time, improve work efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural gas pipeline engineering, and particularly relates to a leak detection and pressure test method for a gathering and transportation system. BACKGROUND

[0002] As known, sour gas is a classification of natural gas, which contains a large amount of impurities, making the gas acidic. The sour gas contains a large amount of toxic components such as hydrogen sulfide (H2S). This gas can corrode and damage the gathering and transportation pipeline, and once leaked, it will cause damage to the surrounding environment and organisms.

[0003] The gathering and transportation system pipeline network of a certain gas field in Sichuan is laid in a "radial + branch + double line" manner, sour gas is mixed in the gas gathering station and then enters the purification plant to remove hydrogen sulfide, and finally is transported through the connecting line. The sour gas pipeline is relatively long, and since the gas field is a high-sulfur gas field, it is necessary to shut down the gathering and transportation station for maintenance, fully understand the equipment operation state, and eliminate safety hazards to ensure the safe and stable operation of the gas field.

[0004] When the gathering and transportation station is shut down for maintenance, the sour gas needs to be mixed in the gas gathering station and then enter the purification plant. When the gas gathering station is maintained, all stations and external pipelines of the gas field need to be shut down for a month or even longer. Since the equipment and facilities in the station and the external pipelines are under pressure, sudden pressure relief when the well is shut down and sudden pressure charging when the well is opened can easily cause medium leakage. The gas field is located in a mountainous area, the pipeline conditions are complex, and the laying method of the pipeline shows diversity with the changes of topography and landform, and needs to cross mountains and valleys many times, has many bends, and has large changes in pipeline elevation. Under the condition of long gathering and transportation pipeline network and high operation risk, since the medium in the gathering and transportation pipeline network of the gas field is high-sulfur natural gas, and the gas field is located in a densely populated area, once the pipeline leaks, it will cause more serious economic losses and personnel casualties.

[0005] Therefore, in order to achieve zero sour gas emission during the whole production resumption process, discover hidden trouble points in time and dispose hidden trouble problems in time, it is necessary to optimize the well opening and production resumption process after the whole gas field is shut down for maintenance, so that the gathering and transportation system of the whole gas field can be successfully resumed at one time, and the risk of medium leakage is reduced. SUMMARY

[0006] The present application aims to solve the problem that the existing leak detection and pressure test method for the gathering and transportation pipeline cannot locate the leakage point and cannot discover and eliminate hidden troubles before the sour gas enters the pipeline when the gathering and transportation station of the gas field is shut down for maintenance, and provides a leak detection and pressure test method for a gathering and transportation system.

[0007] In order to achieve the above-mentioned application purpose, the present application provides the following technical scheme:

[0008] A leak detection and pressure test method for a gathering and transportation system, comprising the following steps:

[0009] Leak detection and pressure test of the station-out pipeline section: fuel gas or nitrogen is used to pressurize and detect leaks of the station-out pipeline section; acid gas is used to pressurize and detect leaks of the station-out pipeline; and the station-out pipeline is connected to the production state;

[0010] Leak detection and pressure test of the station-in pipeline section: fuel gas or nitrogen is used to detect leaks of the station-in pipeline; and acid gas is used to pressurize and detect leaks of the station-in pipeline section.

[0011] The station-in and station-out pipelines are connected to complete the leak detection and pressure test of the gathering and transportation system.

[0012] The leak detection and pressure test method of the gathering and transportation system provided by the present application divides the station-out pipeline into different sections, and pressurizes and detects leaks of the pipelines in different sections respectively. If a leak occurs in the section being detected, the location of the abnormal leak point can be determined in time, the abnormal point can be positioned conveniently and quickly, and the abnormality can be disposed quickly, thereby shortening the leak detection time and improving the work efficiency. The method also pressurizes the station-out pipeline by using different media (i.e. relatively safe fuel gas or nitrogen and harmful acid gas) in sections. Since the gathering pipeline is mainly used for transporting acid gas, and acid gas leakage will pollute the surrounding environment and personnel, the relatively safe fuel gas or nitrogen is used for pressure test first. The fuel gas or nitrogen is used as the pressurizing gas. Since the fuel gas or nitrogen is relatively safe, the impact on the surrounding environment and personnel is small if a leak occurs. After the pressure is qualified, the harmful acid gas is used for pressure test, thereby reducing the harm of acid gas leakage to the surrounding environment and residents.

[0013] Preferably, the leak detection and pressure test of the station-in pipeline section is performed first, and then the leak detection and pressure test of the station-out pipeline section is performed. Finally, the station-in and station-out pipelines are connected to complete the leak detection and pressure test of the gathering and transportation system.

[0014] Preferably, the station-out pipeline is leak detected and pressure tested first, and then the station-in pipeline is leak detected and pressure tested. The leak detection and pressure test process is optimized, and the situation that the station-in pipeline is pressure tested and leak detected, and then it is found that the station-out pipeline still has unqualified pressure test or still has a leak point is avoided. If this situation occurs, the station-out pipeline needs to be pressure tested and leak detected again for safety consideration. After the station-out pipeline is pressure tested and leak detected, the station-in pipeline needs to be pressure tested and leak detected again, which causes unnecessary process repetition, waste of human resources, prolongs the construction period, and has low work efficiency.

[0015] Preferably, the leak detection and pressure test of the station-in pipeline section is performed first, and then the leak detection and pressure test of the station-out pipeline section is performed. If the leak detection and pressure test of the station-out pipeline section is unqualified, the leak detection and pressure test of the station-in pipeline section is repeated, and the leak detection and pressure test of the station-out pipeline section is performed again. Finally, the station-in and station-out pipelines are connected to complete the leak detection and pressure test of the gathering and transportation system.

[0016] Preferably, the specific steps of pressurizing and detecting leaks of the station-out pipeline section by using fuel gas or nitrogen include the following steps:

[0017] S11. dividing the station-out pipeline into several branches, each of which is independent of the others;

[0018] S12. using fuel gas or nitrogen to charge each branch independently until the target pressure is reached;

[0019] S13. arranging a line inspection personnel to inspect the station-out pipeline;

[0020] S14. waiting for at least 24 hours without a leak point before proceeding to the subsequent process;

[0021] S15. if there is a leak point, releasing the charged gas in the branch, and repeating steps S12-S14 after plugging the leak.

[0022] The station-out pipeline to be tested and inspected is divided into several independent branches. Since each branch is independent of the others, if an abnormal leak point is found, the leak point can be quickly discovered and plugged, avoiding the waste of manpower and material resources caused by shutting down the entire pipeline and checking the leak point section by section in the traditional whole-section leak inspection. Since each branch is independent of the others, the construction of other branches is not affected during the construction process, improving the work efficiency. In order to prevent the pipeline from being damaged by sudden pressure increase, the pipeline is charged in stages during the pressure test.

[0023] Preferably, the step S12 of charging in stages is at least two stages.

[0024] Charging in at least two stages can gradually increase the pressure, better protecting the pipeline to be tested.

[0025] Preferably, the step S13 of inspecting in stages is that the leak inspection is performed once for each increase in pressure.

[0026] The step S13 of inspecting in stages increases the number of inspections, avoiding the emergence of a leak point that cannot be discovered in time during the pressure increase process, causing a safety hazard.

[0027] Preferably, the step of using acid gas to charge the station-out pipeline and perform leak inspection includes the following steps:

[0028] S21. using acid gas to charge the station-out pipeline in stages;

[0029] S22. arranging a line inspection personnel to inspect the station-out pipeline in stages according to the pressure, i.e. performing leak inspection once for each increase in pressure.

[0030] Since the acid gas is a harmful gas, step-by-step pressure charging can prevent the acid gas from leaking due to sudden increase of pressure in the pipeline, and the step-by-step leakage inspection and increased inspection frequency can avoid the pipeline from having a leakage point that cannot be found in time and causes safety hazards during the process of pressure increase.

[0031] Preferably, the station pipeline commissioning and leakage inspection using fuel gas or nitrogen specifically comprises the following steps:

[0032] S41. 1±0.1 MPa fuel gas or nitrogen is charged into the station pipeline, and whether the station pipeline is passable is checked;

[0033] S42. If the station pipeline is not passable, the gas in the station pipeline is discharged through a venting system, and S41 is repeated after the blockage is removed until the station pipeline is passable;

[0034] S43. If a leakage point is found, the gas in the station pipeline is released, and S41-S42 are repeated after the leakage is blocked.

[0035] During the station pipeline commissioning, low-pressure gas of 1±0.1 MPa is first charged, and the first charging of low-pressure gas can prevent the pipeline from being damaged due to excessive pressure caused by sudden increase of pressure.

[0036] Preferably, the station pipeline is segmented by throttle valves.

[0037] Preferably, the station pipeline is segmented by throttle valves, because each station pipeline is provided with a throttle valve, which facilitates segmentation and can test the throttling effect of the throttle valve during pressure testing and leakage inspection.

[0038] Preferably, the station pipeline segmented pressure testing using acid gas is specifically step-by-step segmented pressure testing using acid gas.

[0039] Step-by-step pressure charging can prevent the acid gas from leaking due to sudden increase of pressure in the station pipeline.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] 1. The leak detection and pressure test method of the gathering and transportation system provided by the present application divides the station-out pipeline into different sections, and the pressure test and leak detection are carried out in different sections respectively. If a leak occurs in the section being tested, the location of the abnormal leak point can be determined in time, the abnormal point can be positioned quickly and conveniently, and the abnormality can be disposed quickly, thereby shortening the leak detection time and improving the work efficiency. The station-out pipeline to be tested and leak detected is divided into a plurality of independent branch lines. Since the branch lines are independent of each other, if an abnormal leak point is found, the leak point can be found and plugged in time, thereby avoiding the waste of manpower and material resources caused by stopping the whole pipeline, checking the leak point section by section and other problems in the traditional whole-section leak detection. Since the branch lines are independent of each other, the construction of other branch lines is not affected during the construction process, thereby improving the work efficiency. The method also uses different media (i.e. relatively safe fuel gas or nitrogen and harmful acid gas) to test the pressure of the station-out pipeline by section. Since the gathering pipeline is mainly used for transporting acid gas, and the acid gas will pollute the surrounding environment and personnel once leaked, the relatively safe fuel gas or nitrogen is used for pressure test first. Since the fuel gas or nitrogen is relatively safe, the influence on the surrounding environment and personnel caused by the leak is small. After the pressure is qualified, the harmful acid gas is used for pressure test, thereby reducing the harm of acid gas leakage to the surrounding environment and residents.

[0042] 2. Preferably, the station-out pipeline is tested and leak detected first, and then the station-in pipeline is tested and leak detected, thereby optimizing the leak detection and pressure test process, avoiding the situation that the station-out pipeline still has unqualified pressure test or leak point after the station-in pipeline is tested and leak detected, and causing unnecessary process repetition, waste of human resources, prolongation of construction period and low work efficiency if the situation occurs. Generally, the station-out pipeline needs to be tested and leak detected again for safety consideration after the station-in pipeline is tested and leak detected, and the station-in pipeline needs to be tested and leak detected again after the station-out pipeline is tested and leak detected, thereby causing unnecessary process repetition, waste of human resources, prolongation of construction period and low work efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is the leak detection and pressure test method flow chart of embodiment 1 of the present application;

[0044] Figure 2 is the leak detection and pressure test method flow chart of embodiment 2 of the present application. DETAILED DESCRIPTION

[0045] The present application will be further described in detail below in combination with test examples and specific embodiments. However, it should not be understood that the scope of the above-mentioned subject matter of the present application is limited to the following embodiments only, and any technology realized based on the content of the present application belongs to the scope of the present application.

[0046] Embodiment 1

[0047] The present application provides a leak detection and pressure test method of a gathering and transportation system, comprising the following steps:

[0048] Station outside pipeline part: using fuel gas or nitrogen to charge pressure and leak detection for station outside pipeline section; using acid gas to charge pressure and leak detection for the station outside pipeline; connecting the station outside pipeline to production state;

[0049] Station inside pipeline part: using fuel gas or nitrogen to leak detection for station inside pipeline; using acid gas to pressure test for station inside pipeline section, leak detection for station inside whole process;

[0050] Connecting the station inside pipeline and station outside pipeline, completing leak detection and pressure test for gathering and transportation system.

[0051] Generally, in order to avoid the situation that after the station inside pipeline pressure test and leak detection are qualified, it is found that the station outside pipeline still has unqualified pressure test or still has leakage point, generally, for safety consideration, it is needed to re-pressure test and leak detection for the station outside pipeline, and after the station outside pipeline pressure test and leak detection are qualified, it is needed to re-pressure test and leak detection for the station inside pipeline, which causes unnecessary process repetition and waste of human resources, prolongs construction period and has low work efficiency. Therefore, we prefer to first pressure test and leak detection for the station outside pipeline part, then pressure test and leak detection for the station inside pipeline part, and finally connect the station inside pipeline and station outside pipeline, complete leak detection and pressure test for gathering and transportation system, which is taken as an example for specific description in this order:

[0052] S11. The station outside pipeline is divided into several branch lines, and each branch line is independent of each other;

[0053] The station outside pipeline to be pressure tested and leak detected is divided into several independent branch lines. Since each branch line is independent of each other, if an abnormal leakage point is found, the leakage point can be quickly found and plugged, and in the construction process, it does not affect the construction of other branch lines, which improves work efficiency.

[0054] S12. Fuel gas or nitrogen is used to charge pressure for each branch line respectively, until the target pressure is reached;

[0055] In this embodiment, in order to prevent the pipeline from being damaged due to sudden increase of internal pressure, hierarchical pressure charging is adopted during pressure test, and each branch line is charged in two stages. In order to avoid pollution to the surrounding environment and personnel, fuel gas or nitrogen is used for pressure charging.

[0056] S13. Leak detection and inspection is arranged for each branch line by a line inspection personnel, that is, leak detection and inspection is carried out once for each increased pressure level, and at the same time, the station inside operator pays attention to the pipeline network pressure;

[0057] S14. After at least 24 hours without leakage point, subsequent process is carried out;

[0058] S15. If there is a leakage point, the pressure charging gas in the branch line needs to be released, and after plugging, steps S12-S14 are repeated.

[0059] S21. The station-out pipeline is pressurized using acid gas, and the pressure is gradually increased to the pipeline operating pressure;

[0060] S22. The station-out pipeline is inspected for leaks according to the pressure levels, i.e. one inspection for each level of pressure increase, to ensure smooth operation of the pipeline at the pipeline operating pressure.

[0061] S3. After the pressure test of each station-out branch line is completed and the production conditions are met, the station-out pipeline is connected to the production state;

[0062] S41. 1±0.1 MPa fuel gas or nitrogen is charged into the station-in pipeline to check whether the station-in pipeline is passable;

[0063] At this point, low-pressure fuel gas or nitrogen at 1±0.1 MPa is first charged into the station-in pipeline to prevent the pipeline pressure from being too high due to sudden pressure increase, which may damage the pipeline.

[0064] S42. If the station-in pipeline is not passable, the gas in the station-in pipeline is discharged through the venting system, and after the blockage is removed, S41 is repeated until the station-in pipeline is passable;

[0065] S43. If there is a leak, the pressurized gas in the station-in pipeline is released, and after the leak is blocked, steps S41-S42 are repeated;

[0066] S5. The station-in pipeline is segmented by throttle valves, and acid gas pressure test is performed in stages to charge the pressure to the operating pressure, and the station-in pipeline is inspected for leaks to test the air tightness of the station-in pipeline;

[0067] It is preferred to segment the station-in pipeline by throttle valves because each station-in pipeline is provided with a throttle valve, which facilitates segmentation and also tests the throttling effect of the throttle valve during pressure test and leak inspection.

[0068] S6. After the pressure test of the station-in and station-out pipelines is completed and the leak inspection is qualified, the station-in and station-out pipelines are connected, and the well is opened for production.

[0069] Example 2

[0070] Unlike Example 1, in this example, the pressure test and leak inspection of the station-in pipeline are performed first, and then the pressure test and leak inspection of the station-out pipeline are performed. If the pressure test and leak inspection of the station-out pipeline are not qualified, the leak inspection and pressure test of the station-in pipeline are repeated, and then the leak inspection and pressure test of the station-out pipeline are performed. Finally, the station-in and station-out pipelines are connected, and the well is opened for production. The above sequence is taken as an example for specific description:

[0071] A1. 1±0.1 MPa fuel gas or nitrogen is charged into the station-in pipeline to check whether the station-in pipeline is passable;

[0072] A2. If the station pipeline is not passable, the station pipeline needs to be emptied through the venting system, and after the blockage is removed, repeat A1 until the station pipeline is passable;

[0073] A3. If there is a leak, the pressurized gas in the station pipeline needs to be released, and after the leak is blocked, repeat steps A1-A2;

[0074] B. The station pipeline is divided by a throttle valve, and the acid gas pressure test is carried out in stages, the pressure is charged to the operating pressure, and the station pipeline is leak tested to test the air tightness of the station pipeline;

[0075] C1. The said station pipeline is divided into several branches, and each said branch is independent of each other;

[0076] C2. Fuel gas or nitrogen is used to charge the pressure of each said branch in stages until the target pressure is reached;

[0077] C3. Arrange the line inspection personnel to carry out leak detection and inspection of the station pipeline in stages, that is, once the pressure is increased by one level, leak detection and inspection is carried out, and the internal operator pays attention to the pressure of the pipeline network;

[0078] C4. After at least 24 hours without leaks, proceed to the subsequent process;

[0079] C5. If there is a leak, the pressurized gas in the branch needs to be released, and after the leak is blocked, repeat steps A1-C4.

[0080] D1. Use acid gas to charge the pressure of the station pipeline, and gradually charge the pressure to the operating pressure of the pipeline;

[0081] D2. Arrange the line inspection personnel to carry out leak detection and inspection of the said station pipeline in stages according to the pressure, that is, once the pressure is increased by one level, leak detection and inspection is carried out, and the internal operator pays attention to the pressure of the pipeline network;

[0082] E. After the pressure test of each station branch is completed and the production conditions are met, the station pipeline is connected to the production state;

[0083] F. After the station pipeline and the station pipeline are completed, and the leak detection is qualified, the station pipeline and the station pipeline are connected, and the well is opened for production.

[0084] The above is only a preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for leak detection and pressure testing of a gathering and transmission system, characterized in that, First, leak testing and pressure testing are conducted on the external pipelines, then on the internal pipelines. Finally, the internal and external pipelines are connected to complete the leak testing and pressure testing of the gathering and transportation system. This includes the following steps: Leak testing and pressure testing of the external pipeline: Use fuel gas or nitrogen to pressurize the external pipeline in sections for leak testing; use acid gas to pressurize the external pipeline and conduct leak testing and inspection; connect the external pipeline to the production state; The specific steps for using fuel gas or nitrogen to pressurize and test for leaks in sections of external pipelines include: S11. Divide the external pipeline into several branches, each branch being independent of the others; S12. Each branch line is pressurized in stages using either fuel gas or nitrogen until the target pressure is reached; S13. Arrange for patrol personnel to conduct leak detection and inspection of pipelines outside the station at different levels; S14. Wait at least 24 hours for no leaks before proceeding with the next steps; S15. If there is a leak, release the pressurized gas in the branch line, plug the leak, and repeat steps S12-S14. The process of pressurizing and leak-testing the external pipeline using acid gas includes the following steps: S21. Pressurize the external pipeline using acid gas in stages; S22. Arrange patrol personnel to conduct graded leak inspections of the external pipelines according to pressure levels, that is, a leak inspection is carried out for each pressure level increase. Leak testing and pressure testing of pipelines within the station: Use fuel gas or nitrogen to test for continuity and leaks in the pipelines within the station; use acid gas to perform segmented pressure testing on the pipelines within the station, and perform leak testing on the entire process within the station; The specific steps for checking for continuity and leaks in the station's pipelines using fuel gas or nitrogen include: S41. Inject 1±0.1MPa of fuel gas or nitrogen into the pipeline inside the station and check whether the pipeline inside the station is unobstructed; S42. If the pipeline in the station is not a passable path, the gas in the pipeline in the station is vented through the venting system. After removing the blockage, repeat S41 until the pipeline in the station is a passable path. S43. If a leak is found, release the gas in the pipeline inside the station, plug the leak, and repeat steps S41-S42. Connect the internal and external pipelines to complete the leak detection and pressure test of the collection and transportation system.

2. The method for leak detection and pressure testing of a gathering and transmission system according to claim 1, characterized in that, The graded pressurization described in S12 refers to pressurization in at least two stages.

3. The method for leak detection and pressure testing of a gathering and transmission system according to claim 2, characterized in that, In S13, the leak inspection is carried out in stages, specifically by conducting a leak inspection once for each pressure increase.

4. The method for leak detection and pressure testing of a gathering and transmission system according to claim 1, characterized in that, The pipeline sections within the station are divided by throttle valves.

5. The method for leak detection and pressure testing of a gathering and transmission system according to claim 1, characterized in that, The use of acid gas to perform segmented pressure testing on the pipelines within the station specifically involves using acid gas to perform segmented and graded pressure testing on the pipelines within the station.

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