Pipe column stress corrosion testing device and method

Abstract

The invention relates to the technical field of oil well pipe performance detection, and discloses a pipe column stress corrosion testing device and method.The pipe column stress corrosion testing device comprises a reaction system and a fluid circulation system, and the reaction system comprises a reaction kettle, a to-be-tested pipe column and a sealing cover; the reaction kettle comprises a hollow kettle body and an axial loading structure arranged at the upper part of the kettle body; the axial loading structure is connected with the sealing cover and penetrates out of the kettle body; the to-be-tested tubular column and the reaction kettle are coaxially arranged, and the outer side wall of the to-be-tested tubular column, the inner side wall of the reaction kettle and the sealing cover form a sealed tubular column annulus; the fluid circulation system comprises an in-pipe fluid circulation structure and an annular fluid circulation structure; the inner pressure and the confining pressure are respectively used for filling a corrosion fluid into a to-be-detected tubular column to provide internal pressure and injecting the corrosion fluid into a tubular column annulus to provide confining pressure for the to-be-detected tubular column; the device can simultaneously apply axial stress, tubular column internal pressure and annular confining pressure to a tubular column, accurately simulate a stress corrosion environment and carry out stress corrosion test experiments on the inner wall and the outer wall of the tubular column.

Description

Technical Field

[0001] This application belongs to the technical field of performance testing of oil well pipes, and specifically relates to a pipe string stress corrosion testing device and method. Background Technique

[0002] Carbon capture, utilization and storage (CCUS), as one of the few key technologies that can currently achieve large-scale carbon emissions reduction in fossil energy facilities, plays an important role in the field of addressing climate change. Research by the International Energy Agency (IEA) shows that to achieve the climate goal of controlling global temperature rise within 1.5°C, CCUS technology needs to contribute approximately 15% of the cumulative emissions reduction. In major carbon-emitting countries, CCUS technology is an important technical support for achieving the carbon neutrality goal. However, during the process of CO2 geological storage, the injection well pipe string is long-term in an acidic corrosion environment formed by the dissolution of corrosion media such as CO2 and H2S, and at the same time bears multiple mechanical actions such as the axial load generated by the self-weight of the pipe string, injection gas pressure, and annulus liquid column confining pressure, resulting in a significant mechanical-chemical corrosion coupling effect. The specific manifestations are as follows: corrosion defects exacerbate stress concentration, while the multiaxial stress field accelerates the metal corrosion process, forming a self-excited failure cycle. This synergistic effect enables the pipe string to possibly undergo stress corrosion cracking (SCC) under working conditions far lower than the material yield stress, causing sudden fracture accidents, seriously threatening the safe production of oil and gas fields and restricting the large-scale application of CCUS technology.

[0003] Currently, the research methods for stress corrosion mainly have the following technical limitations: The finite element models and experimental devices for surface gas transmission pipelines are mostly based on the coupling effect of internal pressure-external load under soil environment, and are difficult to be directly applied to the complex downhole working conditions; among the research methods for downhole pipe strings, although the downhole in-situ testing method can conduct corrosion detection in a real environment, due to the limitation of the wellbore space, it can only apply simple tensile or bending loads to sheet specimens and cannot reproduce the complex stress state actually borne by the pipe string; the indoor simulation experiment method has double defects. On the one hand, the existing devices can only apply a single type of stress, such as pure tension or pure bending, to sheet base metal specimens, which is significantly different from the downhole multiaxial stress field, and there are essential differences in material properties between sheet specimens and real pipes; on the other hand, although some scholars have tried to develop a testing device for tubular specimens, the corrosion effect of annulus liquid and the influence of confining pressure on external wall stress corrosion are not considered, resulting in a serious deviation between the experimental conditions and the actual service environment of CCUS well pipe strings.

[0004] It can be seen that there are significant technical bottlenecks in the existing stress corrosion research systems, and none of them can truly characterize the damage evolution law of CCUS well tubulars under the combined action of acidic corrosion media and multiaxial composite stress. In particular, for key factors such as synchronous corrosion of the inner and outer walls of the tubular, dynamic action of annulus fluid, and true mechanical response of the pipe material, an experimental evaluation system that can synchronously reproduce the complex mechanical-chemical coupling conditions downhole has not been established. This technical gap leads to insufficient prediction accuracy of the stress corrosion life of the tubular, severely restricting the design of high-reliability gas injection wellbores and the safety assessment of CCUS projects. There is an urgent need to develop a full-dimensional simulation test device and test method that can apply axial-circumferential-radial composite stress to a real tubular specimen and couple the dynamic action of annulus fluid corrosion media. Summary of the Invention

[0005] In view of at least one of the above-mentioned defects or deficiencies of the prior art, the present application provides a stress corrosion test device and method for tubulars, which can carry out stress corrosion research under fine simulation of different stress and corrosion environments.

[0006] To achieve the above object, on the one hand, the present application provides a stress corrosion test device for tubulars, including: a reaction system, the reaction system includes a reaction kettle, a test tubular disposed inside the reaction kettle, and sealing covers respectively connected to the upper and lower ends of the test tubular; the reaction kettle includes a hollow kettle body and an axial loading structure disposed at the upper part of the kettle body; the axial loading structure is connected to the sealing cover and passes through the kettle body; the test tubular is coaxially disposed with the reaction kettle, and the outer side wall of the test tubular, the inner side wall of the reaction kettle, and the sealing cover form a sealed tubular annulus; a fluid circulation system, including an in-tube fluid circulation structure and an annulus fluid circulation structure; the in-tube fluid circulation structure is connected to the inside of the test tubular and is used to fill the inside of the test tubular with corrosion fluid and provide internal pressure; the annulus fluid circulation structure is connected to the tubular annulus and is used to inject corrosion fluid into the tubular annulus and provide confining pressure for the test tubular.

[0007] In some embodiments, the sealing cover includes an upper sealing cover and a lower sealing cover, the upper part of the lower sealing cover is connected to the test tubular by threads, and the lower part of the lower sealing cover is connected to the reaction kettle by threads;

[0008] The lower sealing cover has a bottom liquid flow hole, and the in-tube fluid circulation structure is connected to the bottom liquid flow hole through a pipeline;

[0009] The kettle body has an annulus liquid injection hole and an annulus liquid discharge hole, and the annulus fluid circulation structure is connected to the annulus liquid injection hole through a pipeline.

[0010] In some embodiments, the axial loading structure includes:

[0011] A stress loading disc, which is threadedly connected to the upper sealing cover;

[0012] A drive rod, the first end of the drive rod is connected with a stress loading head, the stress loading head is fittedly connected with the stress loading disc, and the second end of the drive rod passes through the stress loading disc and the reaction kettle and is placed outside the reaction kettle.

[0013] In some embodiments, a rectangular groove is provided in the stress loading disc, and cylindrical rollers are provided on the stress loading head;

[0014] The stress loading head is fittedly connected with the rectangular groove in the stress loading disc through the cylindrical rollers.

[0015] In some embodiments, the drive rod further includes: an intermediate rod, a cylindrical boss, a mounting hole and a force applying rod;

[0016] The first end of the intermediate rod is connected with the stress loading head, and the second end of the intermediate rod is threadedly connected with the cylindrical boss;

[0017] The cylindrical boss is placed in the axial movement groove at the top of the reaction kettle and is threadedly connected with the axial movement groove;

[0018] The rod body of the drive rod placed outside the reaction kettle has a mounting hole, and the force applying rod passes through the mounting hole.

[0019] In some embodiments, the in-tube fluid circulation structure includes:

[0020] An in-tube fluid control device, an in-tube gas control device and an in-tube drain device that are sequentially connected to the bottom liquid flow hole through pipelines;

[0021] The in-tube fluid control device includes an in-tube fluid storage bottle, a first double plunger pump and an in-tube liquid control valve that are sequentially connected;

[0022] The in-tube gas control device includes a first high-pressure gas cylinder, a pressure reducing valve and an in-tube gas control valve that are sequentially connected, and the output end of the in-tube gas control valve is connected to the bottom liquid flow hole;

[0023] The in-tube drain device is connected to the bottom liquid flow hole through a pipeline.

[0024] In some embodiments, the annulus fluid circulation structure includes:

[0025] An annulus fluid control device and an annulus drain device;

[0026] The annulus fluid control device includes an annulus fluid storage bottle, a second double plunger pump and an annulus liquid control valve that are sequentially connected, and the output end of the annulus liquid control valve is connected to the annulus liquid injection hole;

[0027] The flow discharge device is connected to the annulus drain hole through a pipeline.

[0028] In some embodiments, the fluid circulation system further includes:

[0029] A first backpressure loading device and a second backpressure loading device, each backpressure loading device includes a second high-pressure gas cylinder, a backpressure gas control valve, and a backpressure valve connected in sequence;

[0030] The outlet end of the backpressure valve of the first backpressure loading device is connected to the bottom liquid flow hole through a pipeline;

[0031] The outlet end of the backpressure valve of the second backpressure loading device is connected to the annulus drain hole through a pipeline.

[0032] In some embodiments, the tubing string stress corrosion test device further includes:

[0033] A monitoring system, the monitoring system includes a temperature sensor, a pressure sensor, and a data monitoring computer;

[0034] The temperature sensor is respectively connected to the annulus injection hole and the bottom liquid flow hole, and is used to monitor the temperature of the corrosive fluid injected into the annulus of the tubing string and the corrosive fluid injected into the tubing string to be tested;

[0035] The pressure sensor is respectively connected to the backpressure valves of the first backpressure loading device and the second backpressure loading device, and is used to monitor the backpressure value applied to the in-tube fluid circulation structure and the annulus fluid circulation structure;

[0036] The data monitoring computer is connected to the temperature sensor and the pressure sensor.

[0037] The second aspect of the present application provides a tubing string stress corrosion test method, which uses the tubing string stress corrosion test device as described above, and includes the following steps:

[0038] S1: Configure the corrosive fluid injected into the tubing string to be tested and the annulus of the tubing string;

[0039] S2: Connect and install the reaction kettle, the tubing string to be tested, the axial loading structure, the in-tube fluid circulation structure, and the annulus fluid circulation structure;

[0040] S3: Adjust the axial loading structure to apply a stable axial tensile or compressive stress to the tubing string to be tested;

[0041] S4: Adjust the annulus fluid circulation structure to pump the corrosive fluid into the annulus of the tubing string and maintain the annulus confining pressure;

[0042] S5: Adjust the fluid circulation structure in the pipe, pump the corrosive fluid into the pipe string to be tested, maintain the internal pressure of the pipe string, and apply backpressure to the required internal pressure value for testing;

[0043] S6: Monitor and ensure that the temperature and pressure are stable at the preset values, and start the stress corrosion test according to the predetermined test cycle;

[0044] S7: After the experiment is over, take out the pipe string to be tested, process it, and calculate the overall corrosion rate of the pipe string.

[0045] Through the above-mentioned pipe string stress corrosion test device and method of the present application, it is possible to test pipe strings of various specifications, restore the actual size and shape of the downhole pipe string, and be able to conduct experiments using full-size pipe strings, eliminating the influence of the differences between the sheet base material and the actual pipe string due to factors such as processing and preparation processes on stress corrosion; it can accurately simulate the stress corrosion environment received by the pipe string, and conduct stress corrosion experiments on the inner and outer walls of the pipe string to study the stress corrosion behavior of the pipe string.

[0046] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific embodiment part. Brief Description of the Drawings

[0047] The drawings are used to provide a further understanding of the embodiments of the present application, and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present application, but do not constitute a limitation to the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the structures shown in these drawings. In the drawings:

[0048] Figure 1 is a schematic structural diagram of the pipe string stress corrosion test device of the present invention;

[0049] Figure 2 is a sectional view of the reaction kettle in the pipe string stress corrosion test device of the present invention;

[0050] Figure 3 is a schematic structural diagram of the axial stress loading structure in the pipe string stress corrosion test device of the present invention;

[0051] Figure 4 is a sectional view of the axial stress loading structure in the pipe string stress corrosion test device of the present invention;

[0052] Figure 5 is a schematic structural diagram of the driving rod in the pipe string stress corrosion test device of the present invention;

[0053] Figure 6 is a sectional view of the driving rod in the pipe string stress corrosion test device of the present invention;

[0054] Figure 7It is the structural diagram of the stress loading disc in the tubing stress corrosion test device of the present invention;

[0055] Figure 8 It is the structural diagram of the stress loading head in the tubing stress corrosion test device of the present invention;

[0056] Figure 9 It is the flow chart of the tubing stress corrosion test method of the present invention;

[0057] Description of reference numerals

[0058] 1 Reactor 11 Kettle body

[0059] 111 Heat preservation sleeve 112 Axial movement groove

[0060] 12 Tubing to be tested 121 Inner cavity

[0061] 13 Axial loading structure 131 Stress loading disc

[0062] 132 Driving rod 133 Stress loading head

[0063] 134 Rectangular groove 135 Cylindrical roller

[0064] 136 Intermediate rod 137 Cylindrical boss

[0065] 138 Mounting hole 139 Force adding rod

[0066] 14 Tubing annulus 15 Upper sealing cover

[0067] 151 Annular rubber sleeve 152 Sealing cover plate

[0068] 16 Lower sealing cover 161 Annular rubber gasket

[0069] 162 Circular rubber gasket 17 Bottom liquid flow hole

[0070] 18 Annulus liquid injection hole 19 Annulus liquid discharge hole

[0071] 2 Inner tubing fluid circulation structure 21 Inner tubing fluid storage bottle

[0072] 22 First double plunger pump 23 Inner tubing liquid control valve

[0073] 24 First high-pressure gas cylinder 25 Pressure reducing valve

[0074] 26 Inner tubing gas control valve 27 Inner tubing drain valve

[0075] 3 Annulus fluid circulation structure 31 Annulus fluid storage bottle

[0076] 32 Second double plunger pump 33 Annular orifice liquid control valve

[0077] 34 Annular space bleed-off valve

[0078] 41 Second high-pressure gas cylinder 42 Back-pressure gas control valve

[0079] 43 Back-pressure valve

[0080] 5 Monitoring system 51 Temperature sensor

[0081] 52 Pressure sensor 53 Data monitoring computer Detailed implementation manners

[0082] The following will describe in detail the detailed implementation manners of the present application with reference to the accompanying drawings. It should be understood that the detailed implementation manners described herein are only for explaining and illustrating the present application, and are not used to limit the present application.

[0083] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with exemplary embodiments.

[0084] As Figure 1 shown, a tubing string stress corrosion test device includes a reaction system, the reaction system includes a reaction kettle 1, a tubing string to be tested 12 disposed inside the reaction kettle 1, and sealing covers respectively connected to the upper and lower ends of the tubing string to be tested 12; the reaction kettle 1 includes a hollow kettle body 2 and an axial loading structure 112 disposed at the upper part of the kettle body 2; the axial loading structure 112 is connected to the sealing cover and penetrates out of the kettle body 2; the tubing string to be tested 12 is coaxially disposed with the reaction kettle 1, and the outer side wall of the tubing string to be tested 12, the inner side wall of the reaction kettle 1, and the sealing cover form a sealed tubing string annulus 14; a fluid circulation system, including an in-tubing fluid circulation structure 2 and an annulus fluid circulation structure 3; the in-tubing fluid circulation structure 2 is communicated with the inside of the tubing string to be tested 12 and is used for filling corrosive fluid into the inside of the tubing string to be tested 12 and providing internal pressure; the annulus fluid circulation structure 3 is communicated with the tubing string annulus 14 and is used for injecting corrosive fluid into the tubing string annulus 14 and providing confining pressure for the tubing string to be tested 12.

[0085] The present invention provides a column stress corrosion test device, which can finely simulate the actual stress and corrosion environment of the CCUS downhole string, and conduct stress corrosion research on full-scale strings with different stress and corrosion environments on the inner and outer walls. Stress corrosion tests can be carried out based on this device to study the stress corrosion of the inner and outer walls of the string under complex corrosion medium conditions in the field, measure the corrosion rate of the string, the crack propagation rate, predict the change law of the string wall thickness, etc., so as to realize the evaluation of the stress corrosion of the string. At the same time, by adjusting the parameter values of various influencing factors, systematically explore the influence of key factor variables on the stress corrosion rate, crack initiation and propagation law, and deeply explore the stress corrosion mechanism of the string. It not only makes up for the gap in the research on the stress corrosion of downhole strings in the current oil and gas well field, but also can provide more accurate and comprehensive guiding opinions for the selection of construction parameters, string materials, and annulus protection fluids for CCUS wells.

[0086] As Figure 2 shown, in some embodiments, the sealing cover includes an upper sealing cover 15 and a lower sealing cover 16. The upper part of the lower sealing cover 16 is threadedly connected to the test string 12, and the lower part of the lower sealing cover 16 is threadedly connected to the reaction kettle 1; an annular rubber sealing gasket 161 is padded between the lower sealing cover 16 and the kettle body 2 of the reaction kettle 1, and a circular rubber sealing gasket 162 is adhered to the lower sealing cover 16. The circular rubber sealing gasket 162 contacts the bottom of the test string 12 to jointly achieve the sealing between the inner cavity 121 of the test string 12 and the string annulus 14 under high temperature and high pressure conditions; the lower part of the upper sealing cover 15 is threadedly connected to the test string 12 through a threaded sealing plug, and the upper part of the upper sealing cover 15 has a sealing cover plate 152, and an annular rubber sleeve 151 is installed outside the sealing cover plate 152 to ensure the sealing of the string annulus 14.

[0087] The lower sealing cover 16 has a bottom liquid flow hole 17, and the in-tube fluid circulation structure 2 is connected to the bottom liquid flow hole 17 through a pipeline; the kettle body 2 has an annulus injection hole 18 and an annulus drainage hole 19, and the annulus fluid circulation structure 3 is connected to the annulus injection hole 18 through a pipeline. The corrosive fluid in the inner cavity 121 of the test string 12 flows in and out through the bottom liquid flow hole 17 on the lower sealing cover 16 by the in-tube fluid circulation structure 2; the corrosive fluid in the annulus string flows in through the annulus injection hole 18 on the kettle body 2 by the annulus fluid circulation structure 3, and when draining, it flows out through the annulus drainage hole 19 on the kettle body 2.

[0088] As Figure 3 and Figure 4As shown, in some embodiments, the axial loading structure 112 includes a stress loading disk 131 and a driving rod 132. The stress loading disk 131 is threadedly connected to the threaded joint of the upper sealing cover 15. The first end of the driving rod 132 is connected with a stress loading head 133, and the stress loading head 133 is fittedly connected with the stress loading disk 131. The second end of the driving rod 132 passes through the stress loading disk 131 and the reaction kettle 1 and is placed outside the reaction kettle 1. Specifically, as Figure 7 and Figure 8 shown, the stress loading disk 131 has a rectangular groove 134 therein, and the stress loading head 133 has cylindrical rollers 135. The stress loading head 133 is fittedly connected with the rectangular groove 134 in the stress loading disk 131 through the cylindrical rollers 135. The function of the axial loading structure 112 is to apply stable axial tensile or compressive stress to the pipe string 12 to be measured. During actual operation, the axial tensile or compressive stress is applied to the pipe string 12 to be measured through the driving rod 132.

[0089] As Figure 5 and Figure 6 shown, in some embodiments, the driving rod 132 further includes an intermediate rod 136, a cylindrical boss 137, a mounting hole 138 and a force adding rod 139. The first end of the intermediate rod 136 is connected with the stress loading head 133, and the second end is threadedly connected with the cylindrical boss 137. The cylindrical boss 137 is placed in the axial movement groove 112 at the top of the reaction kettle 1 and is threadedly connected with the axial movement groove 112. The rod body of the driving rod 132 placed outside the reaction kettle 1 has a mounting hole 138, and the force adding rod 139 is inserted into the mounting hole 138.

[0090] Specifically, the stress loading head 133 connected to the first end of the driving rod 132 is umbrella-shaped. The top of the stress loading head 133 abuts against the upper sealing cover 15. The cylindrical boss 137 rotates through the thread between it and the axial movement groove 112, causing the displacement of the axial loading structure 112 to change, so as to apply a compressive stress to the pipe string 12 to be tested. The cylindrical boss 137 rotates reversely through the thread between it and the axial movement groove 112, and the displacement of the axial loading structure 112 changes. At this time, the stress loading head 133 is connected in a fitting manner through the cylindrical roller 135 and the rectangular groove 134 in the stress loading disc 131 to apply a tensile stress to the pipe string 12 to be tested. Therefore, in this application, by changing the relative rotation direction between the cylindrical boss 137 and the axial movement groove 112, the axial loading structure 112 is driven to generate displacement in the axial direction to apply an axial stress to the pipe string 12 to be tested. Among them, the intermediate rod 136 passes through the kettle body 2 of the reaction kettle 1 and is sealed with the kettle body 2 through an annular rubber sleeve 151. The intermediate rod 136 is connected to the cylindrical boss 137 through a thread, which is convenient for installation and disassembly. The rod body of the driving rod 132 outside the kettle body 2 has a mounting hole 138, and the force applying rod 139 is inserted into the mounting hole 138, which is convenient for rotating the cylindrical boss 137 to a specified position to apply stress. After the cylindrical boss 137 reaches the specified position, the force applying rod 139 can be removed to prevent accidental touch from changing the axial stress.

[0091] In some embodiments, the in-pipe fluid circulation structure 2 includes an in-pipe fluid control device, an in-pipe gas control device, and an in-pipe drainage device that are sequentially connected to the bottom liquid flow hole 17 through pipelines. The in-pipe fluid control device includes an in-pipe fluid storage bottle 21, a first double plunger pump 22, and an in-pipe liquid control valve 23 that are sequentially connected. The in-pipe gas control device includes a first high-pressure gas cylinder 24, a pressure reducing valve 25, and an in-pipe gas control valve 26 that are sequentially connected. The output end of the in-pipe gas control valve 26 is connected to the bottom liquid flow hole 17. The in-pipe drainage device is connected to the bottom liquid flow hole 17 through a pipeline.

[0092] Specifically, the corrosive fluid stored in the in-pipe fluid storage bottle 21 is pumped into the inner cavity 121 of the pipe string 12 to be tested through the first double plunger pump 22 from the bottom liquid flow hole 17. The gas stored in the first high-pressure gas cylinder 24 is other single or mixed corrosive gases such as CO2. The corrosive gas flows into the inner cavity 121 of the pipe string 12 to be tested through the pressure reducing valve 25 from the bottom liquid flow hole 17. The in-pipe liquid control valve 23 and the in-pipe gas control valve 26 respectively control the inflow of the corrosive fluid and the corrosive gas into the inner cavity 121 of the pipe string 12 to be tested. The in-pipe drainage device is the in-pipe drainage valve 27, and the in-pipe drainage valve 27 controls the outflow of the corrosive fluid and gas in the inner cavity 121 of the pipe string 12 to be tested.

[0093] In some embodiments, the annulus fluid circulation structure 3 includes an annulus fluid control device and an annulus drain device; the annulus fluid control device includes an annulus fluid storage bottle 31, a second double plunger pump 32, and an annulus liquid control valve 33 connected in sequence, and the output end of the annulus liquid control valve 33 is connected to the annulus liquid injection hole 18; the drain device is connected to the annulus liquid discharge hole 19 through a pipeline.

[0094] Specifically, the corrosive fluid stored in the annulus fluid storage bottle 31 is pumped into the pipe string annulus 14 through the second double plunger pump 32 from the annulus liquid injection hole 18; the annulus liquid control valve 33 controls the inflow of the corrosive fluid in the pipe string annulus 14; during drainage, the corrosive fluid in the pipe string annulus 14 flows out through the annulus liquid discharge hole 19; the annulus drain device is an annulus drain valve 34, and the annulus drain valve 34 controls the outflow of the corrosive fluid in the pipe string annulus 14.

[0095] In some embodiments, the fluid circulation system further includes a first back pressure loading device and a second back pressure loading device, and each back pressure loading device includes a second high-pressure gas cylinder 41, a back pressure gas control valve 42, and a back pressure valve 43 connected in sequence; the outlet end of the back pressure valve 43 of the first back pressure loading device is connected to the bottom liquid flow hole 17 through a pipeline; the outlet end of the back pressure valve 43 of the second back pressure loading device is connected to the annulus liquid discharge hole 19 through a pipeline.

[0096] Specifically, the gas in the second high-pressure gas cylinder 41 is N2 gas, and the second high-pressure gas cylinder 41 provides a stable back pressure for the fluid circulation system; the first back pressure loading device provides a back pressure for the in-pipe fluid circulation structure 2, the back pressure gas control valve 42 controls the opening and closing of the second high-pressure gas cylinder 41, and the second high-pressure gas cylinder 41 provides a stable gas source pressure to the back pressure valve 43 to control the realization of in-pipe pressure loading; the second back pressure loading device provides a back pressure for the annulus circulation structure, the back pressure gas control valve 42 controls the opening and closing of the second high-pressure gas cylinder 41, and the second high-pressure gas cylinder 41 provides a stable gas source pressure to the back pressure valve 43, and the annulus confining pressure loading is realized through the control of the annulus drain valve 34.

[0097] In some embodiments, the pipe string stress corrosion test device further includes a monitoring system 5, and the monitoring system 5 includes a temperature sensor 51, a pressure sensor 52, and a data monitoring computer 53; the temperature sensor 51 is respectively connected to the annulus liquid injection hole 18 and the bottom liquid flow hole 17, and is used to monitor the temperature of the corrosive fluid injected into the pipe string annulus 14 and the corrosive fluid injected into the test pipe string 12; the pressure sensor 52 is respectively connected to the back pressure valves 43 of the first back pressure loading device and the second back pressure loading device, and is used to monitor the back pressure values applied to the in-pipe fluid circulation structure 2 and the annulus fluid circulation structure 3; the data monitoring computer 53 is connected to the temperature sensor 51 and the pressure sensor 52.

[0098] The function of the monitoring system 5 is to monitor the temperature and pressure conditions inside the reactor 1 in real time, ensuring that the temperature and pressure conditions during the test are consistent with the downhole temperature and pressure conditions of the pipe string. The monitoring system 5 consists of a temperature sensor 51, a pressure sensor 52, and a data monitoring computer 53. The temperature sensor 51 is respectively connected to the annulus injection hole 18 and the bottom fluid flow hole 17 to monitor the temperature of the corrosive fluid in the annulus 14 of the injection pipe string and the corrosive fluid injected into the pipe string 12 to be tested. The pressure sensor 52 is respectively connected to two backpressure valves 43 to monitor the backpressure values applied to the internal fluid circulation structure 2 and the annulus fluid circulation structure 3, that is, the internal pressure of the pipe string and the annulus confining pressure. The above-mentioned temperature sensor 51 and pressure sensor 52 are connected to the data monitoring computer 53 to monitor the changes of each parameter throughout the process and maintain the parameter stability.

[0099] The pipe string stress corrosion test device provided by this application is applicable to full-size pipe strings, can accurately simulate the actual stress state and complex corrosion environment of CCUS well pipe strings, and conduct stress corrosion tests on the inner and outer walls of the pipe string simultaneously to test the stress corrosion situation of the pipe string, eliminating the influence of the differences between the sheet base material and the actual pipe string due to processing and preparation processes and other factors on stress corrosion. Considering the actual stress state of the pipe string, the pipe string stress corrosion test device provided by this application can apply axial stress, internal pressure of the pipe string, and annulus confining pressure to the pipe string 12 to be tested simultaneously, making up for the shortcomings of existing devices that can only apply single stress or simple stress combinations and cannot simulate the complex mechanical environment of downhole pipe strings. Considering that the inner and outer walls of downhole pipe strings are in different stress corrosion environments, the pipe string stress corrosion test device provided by this application can explore the stress corrosion of the inner and outer walls of the pipe string simultaneously during a single test process, study the stress corrosion of the pipe string 12 to be tested from an overall perspective, and eliminate the problem that the stress corrosion experiment only on the single side wall of the tubular specimen does not conform to the actual situation. In addition, the pipe string stress corrosion test device provided by this application has strong applicability and complete functions. The fluid injected into the pipe string 12 to be tested can be switched between corrosive gases and corrosive liquids. It can not only conduct stress corrosion research on oil pipes or casing pipes, but also be simplified to conduct stress corrosion research on the single side wall of the pipe string, with the advantage of multiple uses of one device.

[0100] As Figure 9 shown, the second aspect of this application provides a pipe string stress corrosion test method, which uses the pipe string stress corrosion test device as described above, including the following steps:

[0101] S1: Prepare the corrosive fluid injected into the pipe string 12 to be tested and the annulus 14 of the pipe string.

[0102] In the preliminary preparation, according to the on-site data of the CCUS well, determine the temperature parameters of the corrosive fluid injected into the test pipe string 12 and the annulus 14 of the pipe string, as well as the internal pressure of the pipe string, the annulus confining pressure, and the axial stress parameters received by the test pipe string 12. And prepare the corrosive fluid injected into the test pipe string 12 and the annulus 14 of the pipe string according to the actual downhole fluid; record the dimensions of the test pipe string 12, and weigh the pipe string mass with a high-precision balance.

[0103] S2: Connect and install the reaction kettle 1, the test pipe string 12, the axial loading structure 112, the internal fluid circulation structure 2, and the annulus fluid circulation structure 3.

[0104] Connect the fluid pipelines and monitoring lines, store the prepared corrosive fluid in a designated sealed and heat-insulated storage tank, adjust it to the designated temperature, and check that the functions of each valve, pump, sensor, and monitoring system 5 are in good condition and the gas cylinder pressure is sufficient.

[0105] S3: Adjust the axial loading structure 112 to apply a stable axial tensile or compressive stress to the test pipe string 12.

[0106] According to the magnitude of the axial stress received by the pipe string, adjust the thread of the force application rod to screw in or out to the specified displacement to apply the corresponding stress magnitude to the test pipe string 12. After the adjustment is completed, remove the force application rod 139 to prevent accidental contact from changing the axial stress.

[0107] S4: Adjust the annulus fluid circulation structure 3 to pump the corrosive fluid into the annulus 14 of the pipe string and maintain the annulus confining pressure.

[0108] Open the backpressure gas control valve 42 in the second backpressure loading device to open the second high-pressure gas cylinder 41, open the annulus bleed valve 34, and load the backpressure of the backpressure valve 43 to the annulus confining pressure value required for the experiment; open the annulus liquid control valve 33 and the second double plunger pump 32 to pump the annulus corrosive fluid into the annulus 14 of the pipe string. When it is observed that there is fluid flowing out at the annulus bleed valve 34, close the second double plunger pump 32 and close the annulus liquid control valve 33. At this time, stop pumping and maintain the annulus confining pressure.

[0109] S5: Adjust the internal fluid circulation structure 2 to pump the corrosive fluid into the test pipe string 12, maintain the internal pressure of the pipe string, and load the backpressure to the internal pressure value required for the test.

[0110] Open the backpressure gas control valve 42 in the first backpressure loading device to open the second high-pressure gas cylinder 41, close the in-pipe bleed valve 27, and load the backpressure of the backpressure valve 43 to the in-pipe pressure value required for the experiment; open the in-pipe liquid control valve 23 and the first double plunger pump 22, and pump the in-pipe corrosive fluid into the test pipe string 12. When fluid flows out from the other end of the backpressure valve 43, close the first double plunger pump 22 and the in-pipe liquid control valve 23; or control the in-pipe gas control valve 26 to open the first high-pressure gas cylinder 24 to inject corrosive gas into the test pipe string 12. When fluid flows out from the other end of the backpressure valve 43, control the in-pipe gas control valve 26 to close the first high-pressure gas cylinder 24 and maintain the in-pipe pressure.

[0111] S6: Monitor and ensure that the temperature and pressure are stable at the preset values, and start the stress corrosion test according to the predetermined test cycle;

[0112] During the whole test process, monitor the temperature of the fluid injected into the annulus 14 of the pipe string and the test pipe string 12, as well as the pressure at the backpressure valve 43, to ensure that the experimental temperature value and pressure value are stable at the preset values.

[0113] S7: After the experiment, take out the test pipe string 12, and calculate the overall corrosion rate of the pipe string after treatment.

[0114] If the test pipe string 12 breaks during the test, it proves that the test pipe string 12 has suffered stress corrosion failure, and then take out the specimen. If the test pipe string 12 does not break during the test, conduct the test experiment according to the predetermined cycle, such as 30 days, 60 days, etc. After the experiment, take out the test pipe string 12.

[0115] After taking out the test pipe string 12, gently brush the surface of the test pipe string 12 with a soft brush, rinse the surface of the test pipe string 12 with clean water, clean the test pipe string 12 with a rust remover, soak it in anhydrous ethanol to remove corrosion products, and dry it for 24 h.

[0116] After drying, measure the change in the inner and outer wall diameters of the test pipe string 12 every 1 cm along the axial direction of the test pipe string 12; measure the final mass of the pipe string, and calculate the overall corrosion rate of the pipe string through the following formula:

[0117]

[0118] Among them, C R represents the corrosion rate of the test pipe string 12, with the unit of mm / a; ΔW is the mass loss of the test pipe string 12 before and after the test, with the unit of g; A is the exposed area of the material of the test pipe string 12, with the unit of cm 2 ; T is the corrosion time of the test pipe string 12, with the unit of h; ρ is the density of the material of the test pipe string 12, with the unit of g / cm 3; "87,600" is a unit conversion constant obtained by converting time units from hours to years (365 × 24 hours) and area units from square centimeters to square meters, etc.

[0119] In addition, the surface corrosion defects and cross-sectional microtopography of the pipe string 12 to be measured can be observed by using a SEM scanning electron microscope, the composition of the corrosion products can be identified by using an X-ray diffractometer, and the elemental composition of the corrosion area can be analyzed by using an EDS energy spectrometer, so as to conduct a more in-depth study on the stress corrosion behavior and mechanism of the inner and outer walls of the pipe string 12 to be measured.

[0120] A pipe string stress corrosion test method proposed in this application can carry out stress corrosion test experiments based on a pipe string stress corrosion test device, study the stress corrosion conditions of the inner and outer walls of the CCUS well pipe string, measure the corrosion rate of the pipe string, the crack propagation rate, predict the change law of the pipe string wall thickness, etc., and realize the evaluation of the pipe string stress corrosion. At the same time, by adjusting the parameter values of various influencing factors, systematically explore the influence of key factor variables on the stress corrosion rate, crack initiation and propagation law, and deeply explore the pipe string stress corrosion mechanism, which not only makes up for the gap in the research on the stress corrosion of downhole pipe strings in the current oil and gas well field, but also can provide more accurate and comprehensive guiding opinions for the selection of construction parameters, pipe string materials, and annulus protection fluids of CCUS wells.

[0121] A pipe string stress corrosion test device and method provided in this application can test pipe strings of various specifications, restore the actual size and shape of downhole pipe strings, and use full-size pipe strings for experiments, eliminating the influence of the differences in processing and preparation processes between sheet base materials and actual pipe strings on stress corrosion; considering the actual stress state of the CCUS well pipe string, the device can simultaneously apply axial stress, internal pressure of the pipe string, and annulus confining pressure to the pipe string, making up for the shortcomings of existing devices that can only apply single stress or simple stress combinations and cannot simulate the complex mechanical environment of downhole pipe strings; considering that the inner and outer walls of downhole pipe strings are in different stress corrosion environments, explore the stress corrosion of the inner and outer walls of the pipe string simultaneously during a single test, and study the stress corrosion of the pipe string from an overall perspective, eliminating the problem that the stress corrosion experiment on only one side wall of a tubular specimen does not conform to the actual situation. It can inject corrosive gas or liquid into the pipe string according to whether the pipe string 12 to be measured is a tubing or a casing and the different corrosion media on the inner and outer walls of the pipe string, accurately simulate the stress corrosion environment, and conduct stress corrosion experiments on the inner and outer walls of the pipe string to study the stress corrosion behavior of the pipe string. In addition, the invention can also conduct stress corrosion experiments on the inner wall, outer wall, or both the inner and outer walls alone. And sensitivity analysis can be carried out on key influencing factors such as temperature, axial pressure, internal pressure, annulus confining pressure, and the properties of corrosive fluids inside the pipe and in the annulus.

[0122] In one embodiment, the tubing stress corrosion test device of the present application can conduct a single outer wall stress corrosion experiment on the tubing 12 to be tested. Specifically, replace the annulus corrosion fluid configured in step S1 with mineral oil, and the remaining steps are the same as the above steps, so that while the outer wall of the tubing 12 does not corrode, an annulus confining pressure can be applied.

[0123] In one embodiment, the tubing stress corrosion test device of the present application can conduct a single inner wall stress corrosion experiment on the tubing 12 to be tested. Specifically, replace the internal corrosion fluid configured in step S1 with mineral oil, and the remaining steps are the same as the above steps, so that while the inner wall of the tubing 12 does not corrode, an internal pressure of the tubing can be applied.

[0124] In one embodiment, the tubing stress corrosion test device of the present application can explore the influence of temperature on stress corrosion. Specifically, during the actual operation process, keep the axial stress, internal pressure of the tubing, annulus confining pressure, and the properties of the internal and annulus corrosion fluids applied to the tubing 12 unchanged, adjust the temperature of the corrosion fluid stored in the liquid storage tank, and conduct multiple tests to explore the influence of temperature on stress corrosion.

[0125] In one embodiment, the tubing stress corrosion test device of the present application can explore the influence of axial pressure on stress corrosion. Specifically, during the actual operation process, keep the internal pressure of the tubing, annulus confining pressure, the properties of the internal and annulus corrosion fluids, and the temperature applied to the tubing 12 unchanged, adjust the displacement of the axial loading structure 112, and conduct multiple tests to explore the influence of axial pressure on stress corrosion.

[0126] In one embodiment, the tubing stress corrosion test device of the present application can explore the influence of annulus confining pressure on stress corrosion. Specifically, during the actual operation process, keep the axial stress, internal pressure of the tubing, the properties of the internal and annulus corrosion fluids, and the temperature applied to the tubing 12 unchanged, adjust the back pressure value in step S4 to control the magnitude of the annulus confining pressure, and conduct multiple tests to explore the influence of annulus confining pressure on stress corrosion.

[0127] In one embodiment, the tubing stress corrosion test device of the present application can explore the influence of internal pressure of the tubing on stress corrosion. Specifically, during the actual operation process, keep the axial stress, annulus confining pressure, the properties of the internal and annulus corrosion fluids, and the temperature applied to the tubing 12 unchanged, adjust the back pressure value in step S5 to control the magnitude of the internal pressure of the tubing, and conduct multiple tests to explore the influence of internal pressure of the tubing on stress corrosion.

[0128] In one embodiment, the tubing stress corrosion test device of the present application can explore the influence of the properties of the corrosive medium on stress corrosion. Specifically, during the actual operation process, while keeping the axial stress, internal pressure of the tubing, annulus confining pressure, and the temperatures of the corrosive fluids inside and outside the tubing applied to the tubing under test 12 unchanged, adjust the properties of the corrosive fluid inside the tubing and the corrosive fluid in the annulus configured in step S1, conduct multiple tests, and explore the influence of the properties of the corrosive medium on stress corrosion.

[0129] The tubing stress corrosion test device in the present application can also conduct other test experiments, which will not be elaborated here.

[0130] Those skilled in the art can understand that the present application is not limited to the specific details in the above embodiments either. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0131] In the description of the present application, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0132] In the present application, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection, or communicable with each other; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0133] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0134] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A tubing string stress corrosion test device, characterized in that, Comprising: A reaction system, which includes a reaction kettle, a test pipe string arranged inside the reaction kettle, and sealing caps respectively connected to the upper and lower ends of the test pipe string; the reaction kettle includes a hollow kettle body and an axial loading structure arranged at the upper part of the kettle body; the axial loading structure is connected to the sealing cap and penetrates out of the kettle body; the test pipe string is coaxially arranged with the reaction kettle, and the outer side wall of the test pipe string, the inner side wall of the reaction kettle, and the sealing cap form a sealed pipe string annulus; A fluid circulation system, including an in-pipe fluid circulation structure and an annulus fluid circulation structure; the in-pipe fluid circulation structure is communicated with the inside of the test pipe string and is used for filling corrosive fluid into the inside of the test pipe string and providing internal pressure; the annulus fluid circulation structure is communicated with the pipe string annulus and is used for injecting corrosive fluid into the pipe string annulus and providing confining pressure for the test pipe string.

2. The pipe string stress corrosion test device according to claim 1, wherein: The sealing cap includes an upper sealing cap and a lower sealing cap. The upper part of the lower sealing cap is connected to the test pipe string by a thread, and the lower part of the lower sealing cap is connected to the reaction kettle by a thread; The lower sealing cap has a bottom liquid flow hole, and the in-pipe fluid circulation structure is connected to the bottom liquid flow hole through a pipeline; The kettle body has an annulus liquid injection hole and an annulus liquid discharge hole, and the annulus fluid circulation structure is connected to the annulus liquid injection hole through a pipeline.

3. The tubing string stress corrosion test device according to claim 2, characterized in that, The axial loading structure includes: A stress loading disc, which is threadedly connected to the upper sealing cap; A driving rod, the first end of the driving rod is connected with a stress loading head, the stress loading head is fitted and connected with the stress loading disc, and the second end of the driving rod passes through the stress loading disc and the reaction kettle and is placed outside the reaction kettle.

4. The pipe string stress corrosion test device according to claim 3, wherein: The stress loading disc has a rectangular groove inside, and the stress loading head has cylindrical rollers; The stress loading head is fitted and connected through the cylindrical rollers and the rectangular groove inside the stress loading disc.

5. The tubing string stress corrosion test device according to claim 3, wherein, The driving rod further includes: An intermediate rod, a cylindrical boss, a mounting hole, and a force applying rod; The first end of the intermediate rod is connected to the stress loading head, and the second end of the intermediate rod is threadedly connected to the cylindrical boss; The cylindrical boss is placed in the axial movement groove at the top of the reaction kettle and is threadedly connected to the axial movement groove; The rod body of the driving rod placed outside the reaction kettle has a mounting hole, and the force applying rod passes through the mounting hole.

6. The tubing string stress corrosion test device according to claim 2, characterized in that, The in-pipe fluid circulation structure includes: An in-pipe fluid control device, an in-pipe gas control device, and an in-pipe drain device that are sequentially connected to the bottom liquid flow hole through pipelines; The in-pipe fluid control device includes an in-pipe fluid storage bottle, a first double plunger pump, and an in-pipe liquid control valve that are sequentially connected; The in-pipe gas control device includes a first high-pressure gas cylinder, a pressure reducing valve, and an in-pipe gas control valve that are sequentially connected. The output end of the in-pipe gas control valve is connected to the bottom liquid flow hole; The in-pipe drain device is connected to the bottom liquid flow hole through a pipeline.

7. The tubing string stress corrosion test device according to claim 2, wherein The annulus fluid circulation structure includes: Annular fluid control device and annular fluid drainage device; The annular fluid control device includes an annular fluid storage bottle, a second double plunger pump, and an annular liquid control valve connected in sequence. The output end of the annular liquid control valve is connected to the annular liquid injection hole; The drainage device is connected to the annular liquid drainage hole through a pipeline.

8. The tubing string stress corrosion test device according to claim 2, characterized in that, The fluid circulation system further includes: A first back pressure loading device and a second back pressure loading device. Each back pressure loading device includes a second high-pressure gas cylinder, a back pressure gas control valve, and a back pressure valve connected in sequence; The outlet end of the back pressure valve of the first back pressure loading device is connected to the bottom liquid flow hole through a pipeline; The outlet end of the back pressure valve of the second back pressure loading device is connected to the annular liquid drainage hole through a pipeline.

9. The tubing string stress corrosion test device according to claim 8, wherein It further includes: A monitoring system, which includes a temperature sensor, a pressure sensor, and a data monitoring computer; The temperature sensor is respectively connected to the annular liquid injection hole and the bottom liquid flow hole, and is used to monitor the temperature of the corrosive fluid in the injection string annulus and the corrosive fluid injected into the test pipe string; The pressure sensor is respectively connected to the back pressure valves of the first back pressure loading device and the second back pressure loading device, and is used to monitor the back pressure values applied to the in-pipe fluid circulation structure and the annular fluid circulation structure; The data monitoring computer is connected to the temperature sensor and the pressure sensor.

10. A method for testing the stress corrosion of a pipe string, characterized in that, Using the pipe string stress corrosion test device according to any one of claims 1-9, comprising the following steps: S1: Configure the corrosive fluid for injecting into the test pipe string and the pipe string annulus; S2: Connect and install the reaction kettle, the test pipe string, the axial loading structure, the in-pipe fluid circulation structure, and the annular fluid circulation structure; S3: Adjust the axial loading structure to apply a stable axial tensile or compressive stress to the test pipe string; S4: Adjust the annular fluid circulation structure to pump the corrosive fluid into the pipe string annulus and maintain the annular confining pressure; S5: Adjust the in-pipe fluid circulation structure to pump the corrosive fluid into the test pipe string, maintain the pipe string internal pressure, and load the back pressure to the required internal pressure value for testing; S6: Monitor and ensure that the temperature and pressure are stable at the preset values, and start the stress corrosion test according to the predetermined test cycle; S7: After the experiment is over, take out the test pipe string, and calculate the overall corrosion rate of the pipe string after processing.

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