Test Method for Radial Buckling and Collapse Pressure of Thermoplastic Pipe for Oil and Gas Transportation

Abstract

The present invention provides a method for testing the radial buckling and collapse pressure of thermoplastic pipes for oil and gas transportation. The environmental simulation test and the annulus pressure test are successively carried out on the test sample of the thermoplastic-lined steel pipe, realizing the test of the anti-buckling and collapse performance of the lining layer of the full-size thermoplastic-lined steel pipe product. Through the environmental simulation test, the service conditions of the full-size composite pipe product under the oil and gas transportation working conditions are simulated to the greatest extent. The temperature, pressure, gas components, liquid medium, etc. can be adjusted, and the test sample can rotate, and the test data obtained is more instructive. Through the annulus pressure monitoring system in the annulus pressure test, the law and morphology of the deformation of the lining pipe under pressure during the annulus pressure test can be monitored in real time, providing effective support for the analysis of the anti-buckling or collapse performance of the lining pipe. The present invention can also connect a vacuum pump or a pressure circulation testing machine to the transfer joint through a through hole to study the influence of the negative pressure state or the pressure circulation state on the anti-buckling or collapse performance of the lining pipe.

Description

Technical Field

[0001] The present invention relates to the technical field of performance testing of non-metallic composite pipes, and specifically to a method for testing the radial buckling and collapse pressure of thermoplastic pipes for oil and gas transportation. Background Art

[0002] The corrosion of carbon steel pipes used in the oilfield surface gathering and transportation system is becoming increasingly serious, and corrosion failure accidents occur frequently, causing huge economic losses and environmental pollution. By using the trenchless method, thermoplastic pipes (such as high-density polyethylene pipes HDPE, high-temperature resistant polyolefin pipes HTPO, nylon pipes PA, etc.) are inserted into the corroded steel pipes to form a "pipe-in-pipe" thermoplastic lined steel pipe structure, which can not only isolate the corrosion of the transportation medium to the steel pipe, but also repair some corrosion defects of the steel pipe, and greatly extend the service life of the pipe. This has become a widely used corrosion protection technology in oilfields at home and abroad.

[0003] During the service process after the repair, the petroleum liquid medium will penetrate into the thermoplastic material, resulting in an obvious swelling phenomenon, which will further lead to a decrease in the rigidity of the thermoplastic pipe. In addition, various gases dissolved in the petroleum medium, such as CH4, H2S, CO2, etc., will undergo adsorption, diffusion and other penetration phenomena on the inner surface of the thermoplastic pipe. The gas that penetrates into the interlayer (forming an annulus) between the thermoplastic pipe and the steel pipe will gradually accumulate. When the pipeline is shut down, the internal pressure fluctuates or suddenly goes negative, the external pressure generated by the gas accumulated in the annulus will cause the thermoplastic pipe to undergo radial buckling or collapse failure. Harsh oil and gas gathering and transportation working conditions, such as high temperature, high pressure, and high gas content environment, will, on the one hand, exacerbate the swelling phenomenon of the thermoplastic pipe, and on the other hand, accelerate the gas penetration process, making the risk of radial buckling and collapse failure of the thermoplastic pipe greater. Summary of the Invention

[0004] Aiming at the problem in the prior art that the radial buckling and collapse pressure of thermoplastic pipes cannot be effectively simulated and detected, the present invention provides a method for testing the radial buckling and collapse pressure of thermoplastic pipes for oil and gas transportation. By experimental research, the radial buckling or collapse pressure of the thermoplastic lined pipes to be inserted under different use conditions is determined, and the influence of the oil and gas transportation medium on the radial buckling or collapse performance of the pipes is clarified. Thus, the material properties and specification dimensions of the thermoplastic lined pipes can be optimized in the design stage, which can greatly reduce the risk of buckling or collapse failure of the thermoplastic lined pipes during the subsequent service process from the source, and is of great significance for ensuring the safe, long-term and reliable operation of thermoplastic pipes for oil and gas transportation.

[0005] The present invention is realized through the following technical solutions:

[0006] Test method for radial buckling and collapse pressure of thermoplastic pipes for oil and gas transportation, comprising the following steps:

[0007] Insert the thermoplastic lined pipe into the steel base pipe to obtain a thermoplastic lined steel pipe test sample; after inputting the oil-water simulation medium inside the thermoplastic lined steel pipe test sample, seal the ends and end faces of the thermoplastic lined steel pipe test sample as a whole, convey the gas components, and carry out the environmental simulation test under the conditions simulating the field application working conditions;

[0008] After the environmental simulation test is completed, carry out an annulus pressure test on the thermoplastic lined steel pipe test sample, use the pressure acquisition system to monitor the change of the pressure inside the annulus of the thermoplastic lined steel pipe test sample in real time, and obtain the pressure when the thermoplastic lined pipe radially buckles or collapses through the analysis of the pressure curve.

[0009] Preferably, the length of the thermoplastic lined pipe is greater than the outer diameter length of the thermoplastic lined pipe; when the thermoplastic lined pipe is inserted into the steel base pipe, the two end parts of the thermoplastic lined pipe are respectively 15 - 30 mm longer than the two end parts of the steel base pipe.

[0010] Preferably, the oil-water simulation medium adopts the original liquid from the oil field site or the simulated original liquid prepared in the laboratory; the gas components adopt N2, CO2, H2S or CH4.

[0011] Preferably, a sealing system and a transfer joint are arranged on the thermoplastic lined steel pipe test sample to form a thermoplastic lined steel pipe end sealing test device;

[0012] The sealing system includes sealing plugs, the sealing plugs are respectively inserted into the two end ports of the thermoplastic lined pipe, and the two end ports of the thermoplastic lined pipe are sealed by inner sealing rings respectively;

[0013] The transfer joint is threadedly connected inside the sealing plugs at both ends of the thermoplastic lined pipe, and a pressure gauge, an air inlet valve and a pressure relief valve are arranged on the transfer joint, and a through hole is arranged inside the transfer joint, and the through hole is communicated with the thermoplastic lined pipe;

[0014] The two end faces of the steel base pipe are sealed by flange plates and outer sealing rings, and the outer sealing rings are arranged on the contact line between the end face of the steel base pipe and the thermoplastic lined pipe; the flange plates at both ends of the steel base pipe are connected by fastening screws and tightened by nuts.

[0015] Furthermore, in the environmental simulation test of the thermoplastic lined steel pipe end sealing test device, place the two ends of the thermoplastic lined steel pipe test sample on the support seats respectively and place them in the environmental test chamber, and the environmental test chamber has a temperature rising temperature control function;

[0016] The transfer joints at both ends of the thermoplastic-lined pipe are exposed outside the environmental test chamber. One transfer joint at one end of the thermoplastic-lined pipe is connected to a gas cylinder through a pressure pipe; the transfer joint at the other end of the thermoplastic-lined pipe is connected to an exhaust gas treatment system.

[0017] One transfer joint at one end of the thermoplastic-lined pipe is connected to a motor through a conveyor belt. After starting the motor, it can drive the test sample of the thermoplastic-lined steel pipe to rotate, realizing a dynamic environmental simulation test.

[0018] Furthermore, in the environmental simulation test, the rotational speed of the motor is 10 - 50 r / min.

[0019] Further, during the annulus pressure test of the thermoplastic-lined steel pipe end sealing test device, the pressure relief valve on the transfer joint is in an open state.

[0020] Further, during the annulus pressure test of the thermoplastic-lined steel pipe end sealing test device, an annulus pressure system and an annulus pressure monitoring system are arranged on the steel base pipe;

[0021] The annulus pressure system includes a water inlet, a pressure hose, and a pressure pump; the water inlet is arranged on one side of the steel base pipe, one end of the pressure hose is connected to the water inlet, and the other end is connected to the pressure pump;

[0022] The annulus pressure monitoring system includes a camera, a video connection cable, a pressure sensor connection port, a pressure sensor, and a data acquisition system; the pressure sensor connection port is arranged on the other side of the steel base pipe and is arranged opposite to the water inlet; the data acquisition system is connected to the pressure sensor connection port through the pressure sensor, the camera is arranged on the sealing plug, and is connected to the data acquisition system through the video connection cable.

[0023] Furthermore, during the annulus pressure test, both ends of the thermoplastic-lined steel pipe end sealing test device are fixedly placed on fixed piers.

[0024] Furthermore, during the annulus pressure test, the annulus pressure rate range is 0.1 MPa / s - 0.5 MPa / s.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] The present invention provides a method for testing the radial buckling and collapse pressure of thermoplastic pipes for oil and gas transportation. The environmental simulation test and the annulus pressure test are successively carried out on the test sample of the thermoplastic-lined steel pipe, realizing the test of the anti-buckling and collapse performance of the lining layer of the full-size thermoplastic-lined steel pipe product; through the environmental simulation test, the service conditions of the full-size composite pipe product under the oil and gas transportation working conditions are simulated to the greatest extent, and the temperature, pressure, gas components, liquid media, etc. can be adjusted, and the test sample can rotate, and the test data obtained is more instructive. The annulus pressure test can, through the annulus pressure monitoring system, monitor in real time the law and morphology of the compressive deformation of the lining pipe during the annulus pressure test, providing effective support for the analysis of the anti-buckling or collapse performance of the lining pipe. The present invention can also connect a vacuum pump or a pressure circulation test machine to the transfer joint through a through hole to study the influence of the negative pressure state or the pressure circulation state on the anti-buckling or collapse performance of the lining pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the environmental simulation test system for the thermoplastic-lined steel pipe in the present invention;

[0028] Figure 2 It is a schematic diagram of the end sealing and buckling or collapse pressure test device for the thermoplastic-lined steel pipe in the present invention;

[0029] Figure 3 It is the radial buckling pressure test curve of the thermoplastic-lined pipe in the present invention;

[0030] Figure 4 It is the radial collapse pressure test curve of the thermoplastic-lined pipe in the present invention.

[0031] In the figure: 1 - transfer joint; 2 - pressure gauge; 3 - thermoplastic-lined pipe; 4 - sealing plug; 5 - flange; 6 - fastening screw; 7 - steel base pipe; 8 - water inlet; 9 - pressure hose; 10 - pressure pump; 11 - nut; 12 - outer sealing ring; 13 - inner sealing ring; 14 - intake valve; 15 - pressure relief valve; 16 - video connection line; 17 - camera; 18 - fixed pier; 19 - pressure sensor connection port; 20 - pressure sensor; 21 - data acquisition system; 22 - through hole; 23 - pressure pipe; 24 - gas cylinder; 25 - conveyor belt; 26 - motor; 27 - environmental test chamber; 28 - support seat; 29 - waste gas treatment system. DETAILED DESCRIPTION OF THE INVENTION

[0032] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0034] The present invention will be further described in detail below in conjunction with the accompanying drawings:

[0035] In an embodiment of the present invention, a method for testing the radial buckling and collapse pressure of thermoplastic pipes for oil and gas transportation is provided. By experimental research, the radial buckling or collapse pressure of the thermoplastic inner lining pipes to be inserted and used under different operating conditions is determined, and the influence of the oil and gas transportation medium on the radial buckling or collapse performance of the pipes is clarified. Thus, the material properties and specifications of the thermoplastic inner lining pipes can be optimized in the design stage, which can greatly reduce the risk of buckling or collapse failure during the subsequent service process of the thermoplastic inner lining pipes from the source, and is of great significance for ensuring the safe, long-term and reliable operation of the thermoplastic pipes for oil and gas transportation.

[0036] For the experimental samples of thermoplastic inner lining steel pipes, an inlet water pressure valve group and an annulus pressure monitoring system are opened, and an end sealing device is designed. After the oil, water and gas media are placed in the experimental samples and sealed and put into the environmental test chamber, an annulus pressure test is carried out after a certain time of environmental test simulating the on-site operating conditions, and the annulus pressure and the deformation change law of the thermoplastic inner lining pipes are recorded, and the pressure change curve is analyzed, and then the radial buckling and collapse pressure of the thermoplastic inner lining pipes under the simulated oil and gas transportation environment is determined.

[0037] Specifically, the method for testing the radial buckling and collapse pressure of the thermoplastic pipes for oil and gas transportation includes the following steps:

[0038] Step 1: Insert the thermoplastic-lined pipe 3 into the steel base pipe 7 according to the traditional internal insertion process to prepare a thermoplastic-lined steel pipe test sample, or directly cut a thermoplastic-lined steel pipe made on the oilfield site as the thermoplastic-lined steel pipe test sample.

[0039] Specifically, the length of the thermoplastic-lined pipe 3 is greater than 5 times the outer diameter length of the thermoplastic-lined pipe 3; when the thermoplastic-lined pipe 3 is inserted into the steel base pipe 7, the two ends of the thermoplastic-lined pipe 3 are respectively 15 - 30 mm longer than the two ends of the steel base pipe 7.

[0040] Step 2: Design the end sealing system of the thermoplastic-lined steel pipe test sample according to the specifications of the thermoplastic-lined pipe 3, where the specifications include outer diameter, inner diameter, wall thickness, etc.

[0041] Specifically, a sealing system and a transfer joint 1 are set on the thermoplastic-lined steel pipe test sample to form a thermoplastic-lined steel pipe end sealing test device, as Figure 2 shown;

[0042] The sealing system includes sealing plugs 4, and the sealing plugs 4 are respectively inserted into the two ends of the thermoplastic-lined pipe 3, and the two ends of the thermoplastic-lined pipe 3 are sealed by inner sealing rings 13 respectively;

[0043] The transfer joint 1 is threadedly connected to the sealing plugs 4 at both ends of the thermoplastic-lined pipe 3, and a pressure gauge 2, an air inlet valve 14 and a pressure relief valve 15 are provided on the transfer joint 1, and a through hole 22 is provided inside the transfer joint 1, and the through hole 22 is communicated with the thermoplastic-lined pipe 3;

[0044] The two end faces of the steel base pipe 7 are sealed by flange plates 5 and outer sealing rings 12, and the outer sealing rings 12 are arranged on the contact line between the end face of the steel base pipe 7 and the thermoplastic-lined pipe 3; the flange plates at both ends of the steel base pipe 7 are connected by fastening screws 6 and tightened by nuts 11.

[0045] Step 3: Place the oil-water medium into the test sample and then seal it with the end sealing system and put it into the environmental test chamber 27, establish the on-site operating conditions of the thermoplastic-lined steel pipe (fill with gas to a certain pressure and heat to a certain temperature), start the motor 26 to drive the test sample to rotate and carry out the environmental simulation test. After the environmental simulation test is completed, release the gas inside the test sample.

[0046] Specifically, the oil-water simulation medium uses the original fluid on the oilfield site or the simulated original fluid prepared in the laboratory; the gas components use N2, CO2, H2S or CH4.

[0047] Specifically, according to Figure 1As shown, during the environmental simulation test of the end-sealing test device for thermoplastic-lined steel pipes, both ends of the test sample of the thermoplastic-lined steel pipe are respectively placed on the support seats 28 and placed in the environmental test chamber 27, which has a temperature control function for heating up.

[0048] The transfer joints 1 at both ends of the thermoplastic-lined pipe 3 are exposed outside the environmental test chamber 27. Among them, the transfer joint 1 at one end of the thermoplastic-lined pipe 3 is connected to the gas cylinder 24 through the pressure pipe 23; the transfer joint 1 at the other end of the thermoplastic-lined pipe 3 is connected to the waste gas treatment system 29.

[0049] The transfer joint 1 at one end of the thermoplastic-lined pipe 3 is connected to the motor 26 through the conveyor belt 25. After starting the motor 26, the test sample of the thermoplastic-lined steel pipe can be driven to rotate to realize the dynamic environmental simulation test.

[0050] During the environmental simulation test, the rotation speed of the motor 26 is 10 - 50 r / min.

[0051] Step 4, an annulus pressure testing system and an annulus pressure monitoring system are arranged at the middle part of the steel base pipe to carry out the annulus pressure test, and the change of the annulus pressure is recorded.

[0052] Specifically, during the annulus pressure test of the end-sealing test device for thermoplastic-lined steel pipes, the pressure relief valve 15 on the transfer joint 1 is in an open state.

[0053] According to Figure 2 As shown, during the annulus pressure test of the end-sealing test device for thermoplastic-lined steel pipes, an annulus pressure testing system and an annulus pressure monitoring system are arranged on the steel base pipe 7.

[0054] The annulus pressure testing system includes a water inlet 8, a pressure hose 9 and a pressure pump 10; the water inlet 8 is arranged on one side of the steel base pipe 7, one end of the pressure hose 9 is connected to the water inlet 8, and the other end is connected to the pressure pump 10.

[0055] The annulus pressure monitoring system includes a camera 17, a video connection cable 16, a pressure sensor connection port 19, a pressure sensor 20 and a data acquisition system 21; the pressure sensor connection port 19 is arranged on the other side of the steel base pipe 7 and is arranged opposite to the water inlet 8; the data acquisition system 21 is connected to the pressure sensor connection port 19 through the pressure sensor 20, the camera 17 is arranged on the sealing plug 4 and is connected to the data acquisition system 21 through the video connection cable 16.

[0056] During the annulus pressure test, both ends of the end-sealing test device for thermoplastic-lined steel pipes are fixedly placed on the fixed piers 18 to maintain the stability of the test system.

[0057] In the annulus pressure test, the annulus pressure rate ranges from 0.1 MPa / s to 0.5 MPa / s.

[0058] Step 5, analyze the annulus pressure change curve to determine the buckling and collapse pressures of the thermoplastic lined pipe 3, as Figure 3 and Figure 4 shown.

[0059] The present invention first opens a pressure injection system and an annulus pressure monitoring system on the thermoplastic lined steel pipe test sample, and designs an end sealing system. After placing the simulated oil-water medium into the test sample, it is sealed and placed in the environmental test chamber 27. After applying gas pressure to the inside of the thermoplastic lined steel pipe test sample, the oil-gas working condition environmental simulation test is started. After a certain period of simulation test, the internal pressure of the test sample is relieved to the ambient pressure, the annulus pressure test is carried out, and the annulus pressure and the deformation change law of the thermoplastic lined pipe are recorded, and the pressure change curve is analyzed to further determine the radial buckling and collapse pressures of the thermoplastic lined pipe.

[0060] According to Figure 2 shown, it includes a thermoplastic lined steel pipe test sample, an annulus pressure injection system, an annulus pressure monitoring system, and a sealing system and a transfer joint 1 are arranged on the thermoplastic lined steel pipe test sample to form a thermoplastic lined steel pipe end sealing test device;

[0061] Both ends of the thermoplastic lined steel pipe test sample are sealed by inserting the sealing plugs 4 into the thermoplastic lined pipe 3 and using the inner sealing rings 13 for end sealing. The transfer joint 1 is connected to the sealing plug 4 by a threaded connection method. A pressure gauge 2, an air inlet valve 14 and a pressure relief valve 15 are arranged on the transfer joint 1 to control the pressure injection or pressure relief inside the thermoplastic lined steel pipe test sample during the environmental simulation test. A through hole 22 is also arranged inside the transfer joint 1, which can be connected to an external gas cylinder or a vacuum pump and a pressure circulation pump.

[0062] The end face of the steel base pipe 7 is sealed by a flange 5 and an outer sealing ring 12. The outer sealing ring is arranged on the contact line between the end face of the steel base pipe 7 and the thermoplastic lined pipe 3 to ensure the sealing of the annulus. The flanges 5 at both ends of the thermoplastic lined steel pipe test sample are connected by fastening screws 6 and tightened by nuts 11.

[0063] The upper annulus pressure injection system and annulus pressure monitoring system provided on the steel base pipe 7, the annulus pressure injection system includes a water inlet 8, a pressure injection hose 9 and a pressure pump 10; the water inlet 8 is arranged on one side of the steel base pipe 7, one end of the pressure injection hose 9 is connected to the water inlet 8, and the other end is connected to the pressure pump 10;

[0064] The annulus pressure monitoring system includes a camera 17, a video connection cable 16, a pressure sensor connection port 19, a pressure sensor 20, and a data acquisition system 21; the pressure sensor connection port 19 is arranged on the other side of the steel base pipe 7 and is arranged opposite to the water inlet 8; the data acquisition system 21 is connected to the pressure sensor connection port 19 through the pressure sensor 20 to monitor the annulus pressure change in real time and collect the pressure change curve. The camera 17 is arranged on the sealing plug 4 and is connected to the data acquisition system 21 through the video connection cable 16 to monitor the internal morphology change of the thermoplastic plastic lined pipe 3 in real time.

[0065] As Figure 1 shown, in the environmental simulation test, it includes modules such as an assembled thermoplastic plastic lined steel pipe test sample, an internal pressure supply system, a heating system, a driving system, an exhaust gas treatment system, etc.

[0066] After one end of the thermoplastic plastic lined steel pipe test sample is sealed with the said sealing plug 4, the liquid medium (such as oil, water, etc.) transported by the oil field is placed into the test sample, and the other end of the test sample is sealed with the said sealing plug 4. The adapter 1 connected to the sealing plug 4 is connected to the pressure pipe 23 and the gas cylinder 24 through the internal through hole 22. Close the pressure relief valve 15 and open the intake valve 14 to pressurize the inside of the said test sample. After the said test sample is pressurized to the set value, close the intake valve 14, place the entire test sample filled with the liquid medium and maintaining a certain internal pressure on the support seat 28, and push it into the environmental test chamber 27.

[0067] The environmental test chamber 27 is heated by air and can realize functions of heating up, keeping warm and constant temperature with air circulation.

[0068] The exhaust gas treatment system 29 mainly treats dangerous gases such as H2S and CH4.

[0069] The adapter 1 connected to the sealing plug 4 can be connected to the motor 26 through the conveyor belt 25. Start the motor 26 to drive the test sample to rotate, which can ensure the contact between the entire inner wall of the thermoplastic plastic lined pipe and the liquid medium and realize the dynamic simulation test. After setting the corresponding test parameters (such as pressure, temperature, time, rotation speed, etc.), the oil and gas working condition environmental simulation test of the thermoplastic plastic lined steel pipe can be completed. Subsequently, release the internal pressure of the test sample and connect Figure 2 the modules such as the annulus pressure boosting system and the annulus pressure monitoring system shown, and then the radial buckling and collapse pressure test of the thermoplastic plastic lined pipe can be carried out.

[0070] Example 1

[0071] Test the buckling pressure of the lining layer of a DN100 nylon lined steel pipe transporting oil-water medium under the operating conditions of 60 °C and 2 MPa

[0072] Test sample preparation: Cut a nylon-lined steel pipe test sample with a length of 1200 mm on-site. Machining is used to cut off about 15 - 30 mm of the steel base pipe at both ends.

[0073] Annulus pressure injection system setup: An inlet is opened at the middle part of the steel base pipe layer of the nylon-lined steel pipe test sample.

[0074] Annulus pressure monitoring system setup: At the middle part of the steel base pipe layer of the nylon-lined steel pipe test sample, perpendicular to the inlet direction, a connection port for the pressure sensor is opened.

[0075] End sealing system design: Based on the outer diameter size of the nylon-lined pipe material, design the inner diameter, thickness, and other dimensions of the flange, as well as the outer sealing ring size. Based on the inner diameter size of the DN100 mm nylon-lined pipe material, design the outer diameter of the sealing plug and the position of the inner sealing ring. The width of the sealing plug is more than 3 times the thickness of the flange, and the groove position of the inner sealing ring is at the center of the width of the sealing plug.

[0076] System connection: Connect the adapter with the inlet valve, pressure relief valve, and pressure gauge to the sealing plug. After installing the inner sealing ring on the connected sealing plug, insert it into one end of the nylon-lined pipe material, pour the prepared oil-water medium from the other end, and seal it with the connected sealing plug in the same way. Place the outer sealing ring on the contact line between the end face of the steel base pipe and the outer surface of the nylon-lined pipe material, and then slip on the flange. Use the fastening screw to tightly connect the flanges at both ends of the test sample. Adjust the insertion position of the sealing plug in the nylon-lined pipe material to ensure that the outer end face of the sealing plug is flush with the outer end face of the flange.

[0077] Environmental simulation test: Connect the gas cylinder to the adapter, close the pressure relief valve, open the inlet valve, and increase the pressure to a certain value (not exceeding 2 MPa). After closing the inlet valve, place the entire test sample filled with liquid medium and maintaining a certain internal pressure on the support seat, push it into the environmental test chamber, and connect the transmission belt of the motor to the adapter. Start the motor to drive the test sample to rotate, at the same time control the environmental test chamber to heat up to 60 °C, and open the inlet valve again to adjust the internal pressure of the test sample to 2 MPa, and then start the environmental simulation test timing. After reaching the set test time (such as 168 h), stop the motor and open the pressure relief valve to release the internal gas pressure of the test sample.

[0078] Annulus pressure injection test: Keep the test sample placed in the environmental test chamber and at a constant temperature of 60 °C, connect the annulus pressure injection system and the annulus pressure monitoring system. Open the pressure pump, inject pressure into the annulus at a rate of 0.2 MPa / s, record the change of the annulus pressure, and use the video system to observe the morphological change of the nylon-lined pipe material in real time.

[0079] Result determination: When the annulus pressure appears as Figure 3When the shown change occurs, stop pressurizing, and the inflection point position of the pressure change curve is the radial buckling pressure of the DN100mm nylon-lined pipe for transporting oil-water medium at 60°C.

[0080] Example 2

[0081] Test the collapse pressure of the inner lining of the DN80 polyethylene-lined steel pipe for transporting brine under the operating conditions of 50°C and 2.5MPa.

[0082] Test sample preparation: Cut a DN80 polyethylene-lined steel pipe test sample with a length of 1000mm on-site. Machining and cutting off about 15 - 30mm of the steel base pipe at both ends.

[0083] Annular space pressurizing system setting: Open a water inlet at the middle part of the steel base pipe layer of the polyethylene-lined steel pipe test sample.

[0084] Annular space pressure monitoring system setting: Open a pressure sensor connection port at the middle part of the steel base pipe layer of the polyethylene-lined steel pipe test sample, perpendicular to the water inlet direction.

[0085] End sealing system design: According to the outer diameter size of the polyethylene-lined pipe, design the inner diameter, thickness and other dimensions of the flange, as well as the outer sealing ring size. According to the inner diameter size of the DN80mm polyethylene-lined pipe, design the outer diameter of the sealing plug and the position of the inner sealing ring. The width of the sealing plug is more than 3 times the thickness of the flange, and the groove position of the inner sealing ring is at the center of the width of the sealing plug.

[0086] System connection: Connect the adapter with an intake valve, a pressure relief valve and a pressure gauge to the sealing plug. After installing the inner sealing ring on the connected sealing plug, insert it into one end of the polyethylene-lined pipe, pour the prepared brine solution from the other end, and also use the connected sealing plug for sealing. Place the outer sealing ring on the contact line between the end face of the steel base pipe and the outer surface of the polyethylene-lined pipe, and then put on the flange. Use the fastening screw to tightly connect the flanges at both ends of the test sample. Adjust the insertion position of the sealing plug in the polyethylene-lined pipe to ensure that the outer end face of the sealing plug is flush with the outer end face of the flange.

[0087] Environmental simulation test: Connect the gas cylinder to the transfer joint, close the pressure relief valve, open the inlet valve, and boost the pressure to a certain level (not exceeding 2.5 MPa). After closing the inlet valve, place the entire test sample filled with liquid medium and maintaining a certain internal pressure on the support seat, and push it into the environmental test chamber. Connect the transmission belt of the motor to the transfer joint. Start the motor to drive the test sample to rotate. At the same time, control the environmental test chamber to heat up to 50 °C, and then open the inlet valve again to adjust the internal pressure of the test sample to 2.5 MPa. Then start the environmental simulation test timing. After reaching the set test time (such as 200 h), stop the motor and open the pressure relief valve to release the internal gas pressure of the test sample.

[0088] Annulus pressure test: Keep the test sample placed in the environmental test chamber and maintain a constant temperature of 50 °C. Connect the annulus pressure injection system and the annulus pressure monitoring system. Open the pressure pump and inject pressure into the annulus at a rate of 0.3 MPa / s. Record the change of annulus pressure, and use the video system to observe the morphological changes of the polyethylene lined pipe in real time.

[0089] Result determination: When the annulus pressure curve shows a downward trend (such as Figure 4 ), stop the pressure injection. The highest point position of the pressure change curve is the radial collapse pressure of the DN80 mm polyethylene lined pipe for transporting brine medium at 50 °C.

[0090] Example 3

[0091] Test the radial buckling pressure of a polyethylene pipe with an outer diameter of 150 mm and a wall thickness of 5 mm at room temperature;

[0092] Test sample preparation: Cut a polyethylene pipe with a length of 1500 mm as the test liner pipe sample. Insert the polyethylene pipe into the steel base pipe according to the traditional internal insertion construction process to prepare a polyethylene lined steel pipe test sample. The two ends of the polyethylene pipe in the polyethylene lined steel pipe test sample are each 15 - 30 mm longer than the steel base pipe.

[0093] Annulus pressure injection system setting: Open a water inlet at the middle part of the steel base pipe layer of the polyethylene lined steel pipe test sample.

[0094] Annulus pressure monitoring system setting: Open a pressure sensor connection port at the middle part of the steel base pipe layer of the polyethylene lined steel pipe test sample, perpendicular to the water inlet direction.

[0095] End sealing system design: Design the inner diameter, thickness and other dimensions of the flange, as well as the outer sealing ring dimensions according to the outer diameter size of the polyethylene pipe. Design the outer diameter of the sealing plug and the position of the inner sealing ring according to the inner diameter size of the DN150 mm polyethylene pipe. The width of the sealing plug is more than 3 times the thickness of the flange, and the position of the inner sealing ring groove is at the center of the width of the sealing plug.

[0096] System connection: Connect the adapter with an intake valve, a pressure relief valve and a pressure gauge to the sealing plug. After installing the inner sealing ring on the connected sealing plug, insert it into both ends of the polyethylene lined pipe. Place the outer sealing ring on the contact line between the end face of the steel base pipe and the outer surface of the polyethylene lined pipe, and then slip on the flange. Use the fastening screw to tightly connect the flanges at both ends of the test sample. Adjust the insertion position of the sealing plug inside the polyethylene lined pipe to ensure that the outer end face of the sealing plug is flush with the outer end face of the flange. Place the assembled test sample on the fixed pier and connect the annulus pressure pumping system and the annulus pressure monitoring system.

[0097] Annulus pressure pumping test: Start the pressure pump and pump the annulus at a rate of 0.2 MPa / s, record the change of the annulus pressure, and use the video system to observe the morphological change of the polyethylene lined pipe in real time.

[0098] Result determination: When the annulus pressure shows a change as Figure 3 shown, stop pumping. The inflection point of the pressure change curve is the radial buckling pressure of the polyethylene pipe with an outer diameter of 150 mm and a wall thickness of 5 mm.

[0099] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: Modifications or equivalent replacements can still be made to the specific implementation manners of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. Test method for radial buckling and collapse pressure of thermoplastic pipes for oil and gas transportation, characterized in that, The method includes the following steps: Insert a thermoplastic lined pipe (3) into a steel base pipe (7) to obtain a thermoplastic lined steel pipe test sample. After injecting an oil-water simulation medium into the interior of the thermoplastic lined steel pipe test sample, seal the ends and end faces of the thermoplastic lined steel pipe test sample as a whole, convey gas components, and conduct an environmental simulation test under simulated on-site application conditions. After the environmental simulation test is completed, conduct an annulus pressure test on the thermoplastic lined steel pipe test sample, use a pressure acquisition system to monitor the change of the pressure in the annulus of the thermoplastic lined steel pipe test sample in real time, and obtain the pressure at which the thermoplastic lined pipe (3) radially buckles or collapses through pressure curve analysis. Set up a sealing system and a transfer joint (1) on the thermoplastic lined steel pipe test sample to form an end sealing test device for the thermoplastic lined steel pipe. The sealing system includes a sealing plug (4). The sealing plugs (4) are respectively inserted into the two end ports of the thermoplastic lined pipe (3), and the two end ports of the thermoplastic lined pipe (3) are sealed by inner sealing rings (13) respectively. The transfer joint (1) is threadedly connected to the sealing plugs (4) at both ends of the thermoplastic lined pipe (3). A pressure gauge (2), an intake valve (14) and a pressure relief valve (15) are provided on the transfer joint (1). A through hole (22) is provided in the transfer joint (1), and the through hole (22) communicates with the thermoplastic lined pipe (3). The two end faces of the steel base pipe (7) are sealed by flange plates (5) and outer sealing rings (12). The outer sealing rings (12) are arranged on the contact line between the end face of the steel base pipe (7) and the thermoplastic lined pipe (3). The flange plates at both ends of the steel base pipe (7) are connected by fastening screws (6) and tightened by nuts (11). The length of the thermoplastic lined pipe (3) is greater than the outer diameter length of the thermoplastic lined pipe (3). When the thermoplastic lined pipe (3) is inserted into the steel base pipe (7), the two end parts of the thermoplastic lined pipe (3) are respectively 15 - 30 mm longer than the two end parts of the steel base pipe (7). During the annulus pressure test of the end sealing test device for the thermoplastic lined steel pipe, set up an annulus pressure boosting system and an annulus pressure monitoring system on the steel base pipe (7). The annulus pressure boosting system includes a water inlet (8), a pressure boosting hose (9) and a pressure pump (10). The water inlet (8) is arranged on one side of the steel base pipe (7). One end of the pressure boosting hose (9) is connected to the water inlet (8), and the other end is connected to the pressure pump (10). The annulus pressure monitoring system includes a camera (17), a video connection cable (16), a pressure sensor connection port (19), a pressure sensor (20) and a data acquisition system (21). The pressure sensor connection port (19) is arranged on the other side of the steel base pipe (7) and is arranged opposite to the water inlet (8). The data acquisition system (21) is connected to the pressure sensor connection port (19) through the pressure sensor (20). The camera (17) is arranged on the sealing plug (4) and is connected to the data acquisition system (21) through the video connection cable (16).

2. The method for testing the radial buckling and collapse pressure of a thermoplastic pipe for oil and gas transportation according to claim 1, characterized in that, The oil-water simulation medium uses the original fluid on the oilfield site or the simulated original fluid prepared in the laboratory; the gas components use N2, CO2, H2S or CH4.

3. The method for testing the radial buckling and collapse pressure of the thermoplastic pipe for oil and gas transportation according to claim 1, wherein In the environmental simulation test of the thermoplastic plastic-lined steel pipe end sealing test device, both ends of the thermoplastic plastic-lined steel pipe test sample are respectively placed on the support seats (28) and placed in the environmental test chamber (27), and the environmental test chamber (27) has a temperature control function for heating up; The transfer joints (1) at both ends of the thermoplastic plastic-lined pipe (3) are exposed outside the environmental test chamber (27), wherein the transfer joint (1) at one end of the thermoplastic plastic-lined pipe (3) is connected to the gas cylinder (24) through the pressure pipe (23); the transfer joint (1) at the other end of the thermoplastic plastic-lined pipe (3) is connected to the waste gas treatment system (29); The transfer joint (1) at one end of the thermoplastic plastic-lined pipe (3) is connected to the motor (26) through the conveyor belt (25). After starting the motor (26), the thermoplastic plastic-lined steel pipe test sample can be driven to rotate to realize the dynamic environmental simulation test.

4. The method for testing the radial buckling and collapse pressure of thermoplastic pipes for oil and gas transportation according to claim 3, characterized in that In the environmental simulation test, the rotation speed of the motor (26) is 10~50r / min.

5. The method for testing the radial buckling and collapse pressure of a thermoplastic pipe for oil and gas transportation according to claim 1, characterized in that, In the process of the annulus pressure test of the thermoplastic plastic-lined steel pipe end sealing test device, the pressure relief valve (15) on the transfer joint (1) is in the open state.

6. The method for testing the radial buckling and collapse pressure of thermoplastic pipes for oil and gas transportation according to claim 1, characterized in that, In the annulus pressure test, both ends of the thermoplastic plastic-lined steel pipe end sealing test device are fixedly placed on the fixed piers (18).

7. The method for testing the radial buckling and collapse pressure of a thermoplastic pipe for oil and gas transportation according to claim 1, characterized in that In the annulus pressure test, the annulus pressure rate range is 0.1MPa / s~0.5MPa / s.

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