Oil casing joint external pressure air-tight seal test system and method

Abstract

The invention belongs to the technical field of petroleum casing pipe external pressure air-tight seal detection, and relates to a petroleum casing pipe joint external pressure air-tight seal test system and method.The system comprises a welding type external pressure test unit, a pressurizing unit, a data acquisition unit and a leakage detection unit; the welding type external pressure test unit is composed of an external pressure cylinder, two annular welding end plugs, two safety lantern rings and two plugging baffles, the external pressure cylinder is arranged outside a petroleum casing joint in a sleeving mode, the petroleum casing joint is located in the center of the external pressure cylinder, and a first multifunctional connector and a second multifunctional connector are installed on the external pressure cylinder; the two annular welding end plugs are welded with the outer pressure cylinder and the petroleum casing joint through welding seams to form a sealed annular space area, and the annular space area is filled with the two safety lantern rings. By the adoption of the safety lantern ring, the use amount of test gas can be reduced by 70% or above, the blasting energy is greatly reduced, and the test safety and economical efficiency are higher.

Description

Technical Field

[0001] The present invention belongs to the technical field of external pressure gas tightness detection of oil casing, and relates to an external pressure gas tightness test system and method for an oil casing joint. Background Art

[0002] Oil casing is a key material for oil and gas resource exploration and development. The sealing performance of its joints is a key performance index to ensure the safety of construction and production operations. An objective evaluation of the joint sealing performance can be obtained through the gas tightness test of the oil casing.

[0003] In the existing evaluation technology for the sealing performance of oil casing joints, the tests for the internal pressure sealing ability of the joints have been realized by using liquid or gas as the test medium. In the test for the external pressure sealing ability of the joints, the problem of external pressure gas tightness of the oil casing has been solved by using a liquid medium in the sealing combination of an external pressure autoclave and a rubber ring. However, the problem of gas external pressure sealing has not been solved. Due to the great danger of high-pressure tests, generally, the test device needs to be isolated over a long distance or safety facilities (such as a blasting pit) need to be built, resulting in huge safety investment. There is an urgent need to develop a new evaluation method to fill the blank of the test method for the gas external pressure sealing ability of oil casing joints. Summary of the Invention

[0004] Aiming at the problem of the external pressure gas tightness test for oil casing joints, an external pressure gas tightness test system and method for oil casing joints are provided. A more secure test device is designed, and a safety component - a safety collar is set, which can reduce the test gas consumption by more than 70%, greatly reduce the blasting energy, and has higher test safety and economy. By optimizing the test device and adjusting the test parameters, the accuracy and reliability of the external pressure gas tightness test for oil casing joints are achieved. This test method is applicable to the external high-pressure sealing test with gas as the test medium, which helps to improve the connection quality and safety of oil casing joints.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] On the one hand, the present invention provides an external pressure gas sealing test system for an oil casing joint, which includes a welded external pressure test unit, a pressurizing unit, a data acquisition unit, and a leakage detection unit; the welded external pressure test unit is composed of an external pressure cylinder, two annular welded end plugs, two safety collar rings, and two blocking baffles; the external pressure cylinder is sleeved outside the oil casing joint, and the oil casing joint is located at the central position of the external pressure cylinder. A first multi-functional interface and a second multi-functional interface are installed on the external pressure cylinder; the two annular welded end plugs are welded to the external pressure cylinder and the oil casing joint through welds to form a sealed annulus area. The two safety collar rings are filled in the annulus area, and the two blocking baffles are respectively welded to the two ends of the oil casing joint through welds. One of the blocking baffles is provided with a conduit interface; the pressurizing unit includes a pressurizing device and a high-pressure pipe; the pressurizing device includes a gas booster pump and a gas supply cylinder group. The outlet of the gas supply cylinder group is connected to the inlet of the gas booster pump, and the outlet of the gas booster pump is connected to the second multi-functional interface through a high-pressure pipe; the data acquisition unit is composed of a high-precision pressure sensor, a signal transmission line, and a data acquisition module. The data acquisition module includes a connected data acquisition instrument and a computer. One end of the signal transmission line is connected to the high-precision pressure sensor, and the other end is connected to the data acquisition instrument. The high-precision pressure sensor is hermetically connected to the first multi-functional interface; the leakage detection unit is composed of a conduit and a leak detection device. One end of the conduit is connected to the conduit interface on the blocking baffle, and the other end is connected to the leak detection device.

[0007] Further, the length of the external pressure cylinder should satisfy the joint (coupling length) + 1000 mm. During installation, ensure that the joint is located at the central interface of the external pressure cylinder to eliminate the influence of subsequent welding equipment on the oil casing joint to be tested.

[0008] Further, the gas booster pump is provided with a drive switch, an adjustment switch, and an output cut-off valve, and the gas supply cylinder group is provided with a gas source cut-off valve.

[0009] Further, the leak detection device includes a water tank, a measuring cylinder, and a measuring cylinder support. The measuring cylinder is inverted in the water tank, and the other end of the conduit extends into the water tank and is fixed 10 - 20 mm directly below the mouth of the inverted measuring cylinder.

[0010] An annulus area is formed by the oil casing joint, the external pressure cylinder, and the annular welded end plug for storing high-pressure gas, providing a high-pressure gas environment (gas pressure is the test pressure) for the oil casing joint; the safety collar rings are used to fill the annulus area, minimizing the gas usage volume as much as possible to reduce the energy stored by the high-pressure gas, effectively reducing the destructive power, improving safety, and at the same time improving the pressurization efficiency; a closed space is formed by the oil casing joint and the blocking baffle for storing the gas leaking from the joint (if any).

[0011] Welding and assembly is the most effective connection method for this test device and is also a crucial step for the success of the test. The area within 100 mm on both sides of the weld should be preheated, and the preheating temperature should be controlled at 350 ± 50 °C. The strength of the welding rod should be as close as possible to that of the welded component and needs to be baked according to the usage instructions. After welding, heat preservation measures such as winding asbestos cloth should be taken to cool slowly to room temperature.

[0012] Furthermore, the high-pressure pipe of the pressurization system is a high-pressure rigid pipe or a high-pressure flexible pipe, and its pressure-bearing capacity is not less than 60000 psi.

[0013] On the other hand, the present invention provides a method for the above-mentioned external pressure gas sealing test system of an oil casing joint, including:

[0014] 1) Start the data acquisition unit, set the data acquisition frequency to 1 point per second, and record the pressure-time curve in real time. The accuracy of the high-precision pressure sensor is 0.5% FS, and the range should meet the maximum test pressure and fall within 70% - 90% of its range;

[0015] 2) Pre-pressurize: Open the gas source stop valve and the output stop valve on the pressurization device, and use the gas cylinder group to pressurize itself to 7 - 8 MPa;

[0016] 3) Boost pressure and hold pressure: Start the gas booster pump, control the boost pressure speed at 10 - 105 MPa / min, close the control switch after boosting to the test target pressure, enter the pressure-holding stage, and observe the pressure change of the data acquisition unit;

[0017] 4) Leak detection and judgment: When the pressure of the data acquisition unit continues to drop, at the same time observe whether the inverted measuring cylinder in the water tank collects leaked gas; if no gas is collected in the measuring cylinder, it means that the leak occurs in the test device and each connection port; if gas is collected in the measuring cylinder, it means that the tested oil casing joint (15) has leaked;

[0018] 5) Release pressure: After the pressure-holding ends, end the gas supply and release the pressure to 0 MPa;

[0019] 6) When the test ends, the computer generates a pressure-time test curve, and disassemble the external pressure gas sealing test system of the oil casing joint (15) for the next test.

[0020] Furthermore, in step (4), the leakage rate q is used to characterize the degree of leakage. The liquid level of the measuring cylinder is read once every 5 minutes and the liquid level reading is recorded until the pressure maintenance ends. The leakage rate q = ΔL / Δt, ΔL is the leakage amount, specifically the difference between two liquid level readings, and Δt is the interval between the readings. Except for the first reading, the leakage rate is calculated for each reading, and the maximum value of all leakage rates is used to characterize the leakage of the oil casing joint. After the pressure maintenance time is reached, the pressure maintenance is completed, the gas source shut-off valve on the pressure charging unit is closed, the relief valve on the pressure charging unit is opened, and the pressure relief in the external pressure cylinder is relieved to 0MPa; the data acquisition instrument recovers the data and generates a pressure-time test curve.

[0021] Furthermore, the driving pressure of the gas booster pump is 0.6-0.8 MPa.

[0022] Furthermore, the gas supply cylinder group uses 8-15MPa dry nitrogen as a gas source.

[0023] Furthermore, the water depth of the water tank is 200-300 mm, and the liquid level is consistent with the central horizontal plane of the external pressure cylinder.

[0024] The invention can complete the tests of various petroleum casing external pressure gas sealing test schemes.

[0025] The advantages and positive effects of the present invention are:

[0026] (1) The design of the safety collar in the welded external pressure test device of the present invention can reduce the amount of test gas used by more than 70%, greatly reducing the explosion energy, and making the test safer and more economical.

[0027] (2) The present invention adopts a welding assembly method, which improves the success rate of the external pressure gas sealing test of the petroleum casing joint.

[0028] (3) The leakage detection device of the present invention is simple and low-cost. By optimizing the test device and adjusting the test parameters, the leakage degree of the oil casing joint can be quantitatively and qualitatively characterized at the same time, thereby achieving the accuracy and reliability of the external pressure gas sealing test of the oil casing joint, and having strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The invention discloses an external pressure gas sealing test system for a petroleum casing joint.

[0030] 1-sealing baffle, 2-weld, 3-annular welding end plug, 4-first multifunctional interface, 5-high-precision pressure sensor, 6-signal transmission line, 7-safety collar, 8-external pressure cylinder, 9-high-pressure pipe, 10-data acquisition module, 11-pressurizing device, 12-leak detection device, 13-catheter, 14-second multifunctional interface, 15-oil casing joint. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below through specific embodiments. The following embodiments are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0032] Embodiment 1

[0033] As Figure 1 shown, an external pressure gas sealing test system for an oil casing joint includes a welded external pressure test unit, a pressurizing unit, a data acquisition unit, and a leakage detection unit.

[0034] The welded external pressure test unit consists of an external pressure cylinder 8, two annular welded end plugs 3, two safety collar rings 7, and two plugging baffles 1; the external pressure cylinder 8 is sleeved outside the oil casing joint 15, and the oil casing joint 15 is located at the central position of the external pressure cylinder 8. The two annular welded end plugs 3 are welded to the external pressure cylinder 8 and the oil casing joint 15 through welds 2 to form a sealed annulus area for storing high-pressure gas and providing a high-pressure gas environment for the oil casing joint 15, and the gas pressure is the test pressure. The two safety collar rings 7 are filled in the annulus area between the oil casing joint 15 and the external pressure cylinder 8. The two plugging baffles 1 are respectively welded to the two ends of the oil casing joint 15 through welds 2, and one of the plugging baffles 1 is provided with a conduit interface; the safety collar rings 7 filling the annulus area can reduce the gas usage volume by 70%, so as to reduce the energy stored by the high-pressure gas, effectively reduce the destructive power, improve the safety, and at the same time improve the pressurization efficiency; a closed space is formed by the oil casing joint 15 and the plugging baffle 1 for storing the gas generated by the joint leakage.

[0035] A first multi-functional interface 4 and a second multi-functional interface 14 are installed on the external pressure cylinder 8, both of which penetrate the full wall thickness of the external pressure cylinder 8 to communicate the inside and outside of the external pressure cylinder 8.

[0036] The pressurizing unit includes a pressurizing device 11 and a high-pressure pipe 9. The pressurizing device 11 includes a gas booster pump and a gas supply cylinder group. The gas booster pump is equipped with a drive switch, an adjustment switch, and an output cut-off valve, and the gas supply cylinder group has a gas source cut-off valve; the low-pressure end of the gas booster pump is connected to a dry nitrogen cylinder group as the input gas source. One end of the high-pressure pipe 9 is hermetically connected to the second multi-functional interface 14, and the other end is connected to the high-pressure end interface of the gas booster pump; the high-pressure pipe 9 is a high-pressure hard pipe or a high-pressure hose, and its pressure-bearing capacity is not less than 60000 psi.

[0037] The data acquisition unit is used to collect data and consists of a high-precision pressure sensor 5, a signal transmission line 6, and a data acquisition module 10. The data acquisition module 10 includes a connected data acquisition instrument and a computer. One end of the signal transmission line 6 is connected to the high-precision pressure sensor 5, and the other end is connected to the data acquisition instrument. The high-precision pressure sensor 5 is hermetically connected to the first multi-functional interface 4 for detecting the gas pressure in the annulus area;

[0038] The leakage detection unit consists of a conduit 13 and a leak detection device 12. The leak detection device includes a water tank, a graduated cylinder and a graduated cylinder support. The plastic conduit 13 has a diameter of about 10 mm and the pressure resistance should not be less than 0.1 MPa. The water depth in the water tank is preferably 200 - 300 mm. During the experiment, the liquid level in the water tank should be basically at the same horizontal plane as the central horizontal section of the external pressure cylinder 8 to reduce the influence of atmospheric pressure. The accuracy of the graduated cylinder is 0.1 mL and the capacity can be 100 mL - 200 mL. When in use, it is filled with water and inverted, and the mouth of the graduated cylinder is placed below the liquid level in the water tank and fixed on the graduated cylinder support. One end of the plastic conduit 13 is connected to the conduit 13 interface on the sealing baffle 1, and the other end extends into the water tank and is fixed 10 - 20 mm directly below the mouth of the inverted graduated cylinder.

[0039] Example 2

[0040] A method for an external pressure airtight test system of an oil casing joint 15 for Example 1 includes:

[0041] 1. Assembly of the external pressure test unit:

[0042] 1.1 Place the oil casing joint 15 to be tested in the external pressure cylinder 8, and keep the joint at the central position of the external pressure cylinder 8;

[0043] 1.2 Install safety collar rings 7 on both sides of the joint respectively;

[0044] 1.3 Install annular welded end plugs 3 on both sides of the oil casing joint 15 to be tested respectively;

[0045] 1.4 Pre-assemble two sealing baffles 1 at both ends of the oil casing joint 15 to be tested;

[0046] 1.5 Complete the assembly of welding at each weld 2. The key points of the welding process refer to the technical solution. Both sides within 100 mm of the weld 2 need to be preheated, and the preheating temperature is controlled at 350 ± 50 °C. The strength of the welding rod should be as close as possible to that of the welding component, and it needs to be baked according to the instructions. After welding, heat preservation measures such as winding asbestos cloth should be taken to cool slowly to room temperature;

[0047] 2. Connect the pressurization unit:

[0048] 2.1 Install one end of the high-pressure pipe 9 on the second multi-functional interface 14 on the external pressure cylinder 8, and connect the other end to the high-pressure end interface of the gas booster pump;

[0049] 2.2 Connect the low-pressure end of the gas booster pump to the dry nitrogen cylinder group as the input gas source;

[0050] 2.2 Open the gas source cut-off valve and the output cut-off valve on the pressurization device 11 for trial pressurization to ensure that there is gas discharge at the first multi-functional interface 4 on the external pressure cylinder 8 to ensure the smoothness of the pressurization pipe and the interface. After trial pressurization, close the output cut-off valve;

[0051] 3. Connect the data acquisition unit:

[0052] 3.1 Install the pressure sensor 5 on the second multi-functional interface 14 on the external pressure cylinder 8;

[0053] 3.2 Connect the signal transmission line 6, with one end connected to the pressure sensor 5 and the other end connected to the data acquisition module 10;

[0054] 4. Connect the leak detection device:

[0055] 4.1 Fill the graduated cylinder with water and invert it below the water surface in the water tank, and fix it on the graduated cylinder support;

[0056] 4.2 Connect one end of the conduit 13 to the conduit interface on the safety baffle, and the other end extends into the water tank and is fixed 10 - 20 mm directly below the mouth of the inverted graduated cylinder.

[0057] 5. Test

[0058] 5.1 Start the data acquisition unit, set the data acquisition frequency to 1 point per second, and record the pressure-time curve in real time. The accuracy of the high-precision pressure sensor 5 is 0.5% FS, and the range should meet the maximum test pressure and fall within 70% - 90% of its range;

[0059] 5.2 Pre-charge pressure: Open the gas source stop valve and the output stop valve on the pressure charging device 11, and use dry nitrogen at 8 - 15 MPa from the gas supply cylinder group as the gas source to self-charge to 7 - 8 MPa;

[0060] 5.3 Increase pressure: Turn on the control switch of the pressure booster pump on the pressure charging device 11 to start increasing pressure. The driving pressure of the gas pressure booster pump is 0.6 - 0.8 MPa, and the pressure increasing speed is 10 - 105 MPa / min. After increasing the pressure to the test target pressure, turn off the control switch and close the output stop valve on the pressure charging device 11 to enter the pressure holding stage;

[0061] 5.4 Hold pressure: The pressure holding time is according to the test plan, generally not less than 1 h;

[0062] 5.5 Leak detection and judgment: Read the liquid level of the graduated cylinder every 5 minutes and record the liquid level position until the pressure holding time required by the test plan is reached. Except for the first reading, calculate the leakage rate q (mL / min) for each reading, and characterize the leakage situation of the oil casing joint 15 with the maximum value among all the leakage rates.

[0063] The leakage rate q = ΔL / Δt, where q is the leakage rate; ΔL is the leakage amount (the difference in the readings of the two liquid levels); Δt is the reading interval time;

[0064] 5.6 Pressure relief: After the pressure holding time, the pressure holding is completed. Close the gas source stop valve, open the relief valve, and start pressure relief to reduce the pressure in the external pressure test device to 0 MPa;

[0065] 5.7 The test is completed. The data acquisition module 10 retrieves the data and generates a pressure-time test curve.

[0066] 6. After the test is completed, disassemble the external pressure gas sealing test system for oil casing in the reverse order of 1 to 4 for use in the next test.

[0067] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. An external pressure gas sealing test system for an oil casing joint, characterized in that, Comprising: A welded external pressure test unit, which consists of an external pressure cylinder (8), two annular welded end plugs (3), two safety collar rings (7), and two plugging baffles (1); the external pressure cylinder (8) is sleeved outside the oil casing joint (15), the oil casing joint (15) is located at the central position of the external pressure cylinder (8), and a first multi-functional interface (4) and a second multi-functional interface (14) are installed on the external pressure cylinder (8); the two annular welded end plugs (3) are welded to the external pressure cylinder (8) and the oil casing joint (15) through welds (2) to form a sealed annulus area, the two safety collar rings (7) are filled in the annulus area, and the two plugging baffles (1) are respectively welded to the two ends of the oil casing joint (15) through welds (2), and one of the plugging baffles (1) is provided with a conduit interface; A pressurizing unit, which includes a pressurizing device (11) and a high-pressure pipe (9); the pressurizing device (11) includes a gas booster pump and a gas supply cylinder group, the outlet of the gas supply cylinder group is connected to the inlet of the gas booster pump, and the outlet of the gas booster pump is connected to the second multi-functional interface (14) through the high-pressure pipe (9); A data acquisition unit, which consists of a high-precision pressure sensor (5), a signal transmission line (6), and a data acquisition module (10), the data acquisition module (10) includes a connected data acquisition instrument and a computer, one end of the signal transmission line (6) is connected to the high-precision pressure sensor (5), the other end is connected to the data acquisition instrument, and the high-precision pressure sensor (5) is hermetically connected to the first multi-functional interface (4); A leakage detection unit, which consists of a conduit (13) and a leak detection device (12), one end of the conduit (13) is connected to the conduit interface on the plugging baffle (1), and the other end is connected to the leak detection device.

2. The external pressure gas sealing test system for an oil casing joint according to claim 1, wherein The length of the external pressure cylinder (8) satisfies the coupling length + 1000 mm.

3. The external pressure gas sealing test system for an oil casing joint according to claim 1, wherein The leak detection device includes a water tank, a graduated cylinder, and a graduated cylinder support, and the graduated cylinder is inverted in the water tank.

4. The external pressure gas sealing test system for an oil casing joint according to claim 1, characterized in that The high-pressure pipe (9) is a high-pressure rigid pipe or a high-pressure flexible pipe.

5. A method for an external pressure gas sealing test system of the oil casing joint according to any one of claims 1 to 4, characterized in that, Comprising: 1) Start the data acquisition unit, set the data acquisition frequency to 1 point per second, and record the pressure-time curve in real time. The accuracy of the high-precision pressure sensor (5) is 0.5% FS, and the range should meet the maximum test pressure and fall within 70% - 90% of its range; 2) Pre-pressurize: Open the gas source cut-off valve and the output cut-off valve of the pressurizing device (11), and use the gas supply cylinder group to self-pressurize to 7 - 8 MPa; 3) Boost pressure and hold pressure: Start the gas booster pump, control the pressure boost speed at 10 - 105 MPa / min, enter the pressure holding stage after boosting to the test target pressure, and observe the pressure change of the data acquisition unit; 4) Leak detection and judgment: When the pressure of the data acquisition unit continues to drop, at the same time observe whether the inverted graduated cylinder in the water tank collects leaked gas; if no gas is collected in the graduated cylinder, it means that the leakage occurs at the test device and each connection port; if gas is collected in the graduated cylinder, it means that the tested oil casing joint (15) has leaked; 5) Release pressure: After the pressure holding ends, end the gas supply and release the pressure to 0 MPa; 6) After the test is completed, the computer generates a pressure-time test curve, and the external pressure gas sealing test system of the oil casing joint (15) is disassembled for use in the next test.

6. The method according to claim 5, wherein In step 4), the leakage rate q is used to characterize the degree of leakage. The liquid level of the graduated cylinder is read every 5 minutes and the liquid level reading is recorded until the pressure holding ends. The leakage rate q = ΔL / Δt, where ΔL is the leakage amount, specifically the difference between two liquid level readings, and Δt is the reading interval time.

7. The method according to claim 5, characterized in that The driving pressure of the gas booster pump is 0.6 - 0.8 MPa.

8. The method according to claim 5, characterized in that, The water depth of the water tank is 200 - 300 mm, and the liquid level is kept consistent with the central horizontal plane of the external pressure cylinder (8).

9. The method according to claim 5, characterized in that, The gas supply cylinder group uses dry nitrogen with a pressure of 8 - 15 MPa as the gas source.

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