A test apparatus and method for stress corrosion testing of tubular columns

Abstract

This application relates to the field of oil well tubing performance testing technology, and discloses a tubing stress corrosion testing device and method. The tubing stress corrosion testing device includes a reaction system and a fluid circulation system. The reaction system includes a reaction vessel, a tubing string to be tested, and a sealing cap. The reaction vessel includes a hollow vessel body and an axial loading structure disposed on the upper part of the vessel body. The axial loading structure is connected to the sealing cap and extends out of the vessel body. The tubing string to be tested is coaxially arranged with the reaction vessel, and the outer wall of the tubing string to be tested, the inner wall of the reaction vessel, and the sealing cap form a sealed tubing annulus. The fluid circulation system includes an internal fluid circulation structure and an annulus fluid circulation structure, which are respectively used to fill the interior of the tubing string to provide internal pressure with corrosive fluid and to inject corrosive fluid into the annulus of the tubing string to provide confining pressure for the tubing string to be tested. The device can simultaneously apply axial stress, internal pressure of the tubing string, and annulus confining pressure to the tubing string, accurately simulating the stress corrosion environment and conducting stress corrosion testing experiments on the inner and outer walls of the tubing string.

Description

Technical Field

[0001] This application belongs to the field of oil well tubing performance testing technology, specifically relating to a tubing stress corrosion testing device and method. Background Technology

[0002] Carbon capture, utilization, and storage (CCUS) is one of the few key technologies currently capable of achieving large-scale carbon emission reductions from fossil fuel facilities, playing a crucial role in addressing climate change. Research by the International Energy Agency (IEA) indicates that CCUS technology needs to contribute approximately 15% of the cumulative emission reductions to achieve the climate goal of limiting global warming to 1.5°C. In major carbon-emitting countries, CCUS technology is a vital technological support for achieving carbon neutrality. However, during CO2 geological storage, the injection well tubing is subjected to a prolonged acidic corrosive environment formed by the dissolution of corrosive media such as CO2 and H2S. Simultaneously, it bears multiple mechanical forces, including axial loads from the tubing's own weight, injection pressure, and annular fluid column confining pressure, leading to a significant mechanical-chemical corrosion coupling effect. Specifically, corrosion defects exacerbate stress concentration, while multiaxial stress fields accelerate the metal corrosion process, forming a self-excited destructive cycle. This synergistic effect allows stress corrosion cracking (SCC) to occur even under conditions far below the material's yield stress, causing sudden fracture accidents, seriously threatening the safe production of oil and gas fields and hindering the large-scale application of CCUS technology.

[0003] Current research methods for stress corrosion mainly suffer from the following technical limitations: Finite element models and experimental setups for surface gas pipelines are mostly based on the coupling effect of internal pressure and external load in soil environments, making them difficult to directly apply to complex downhole conditions; while in-situ testing methods for downhole tubing can detect corrosion in real environments, they are limited by wellbore space and can only apply simple tensile or bending loads to sheet-like samples, failing to reproduce the actual composite stress state experienced by the tubing; indoor simulation experiments have a double defect: on the one hand, existing devices can only apply a single type of stress, such as pure tension or pure bending, to sheet-like parent material samples, which differs significantly from the multiaxial stress field in downhole, and sheet-like samples differ fundamentally from real tubing in material properties; on the other hand, although some scholars have attempted to develop tubular sample testing devices, they have not considered the effects of annular fluid corrosion and confining pressure on external wall stress corrosion, resulting in experimental conditions that deviate significantly from the actual service environment of CCUS well tubing.

[0004] It is evident that existing stress corrosion research systems suffer from significant technical bottlenecks, failing to accurately characterize the damage evolution of CCUS well tubing under the combined effects of acidic corrosive media and multiaxial composite stress. In particular, for key factors such as simultaneous corrosion of the inner and outer walls of the tubing, the dynamic effects of annular fluid, and the actual mechanical response of the tubing material, an experimental evaluation system capable of simultaneously reproducing the complex mechanical-chemical coupling conditions downhole has not yet been established. This technological gap results in insufficient accuracy in predicting the stress corrosion life of the tubing, severely restricting the design of high-reliability injection wellbores and the safety assessment of CCUS projects. There is an urgent need to develop a comprehensive simulation testing device and method capable of applying axial-circumferential-radial composite stress to real tubular samples and coupling it with the dynamic effects of annular fluid corrosive media. Summary of the Invention

[0005] In view of at least one of the above-mentioned defects or deficiencies in the prior art, this application provides a tubular stress corrosion testing device and method, which can conduct stress corrosion research in a precise simulation of different stress and corrosion environments.

[0006] To achieve the above objectives, this application provides a tubular stress corrosion testing device, comprising: a reaction system including a reaction vessel, a test tubular column disposed inside the reaction vessel, and sealing caps respectively connected to the upper and lower ends of the test tubular column; the reaction vessel includes a hollow vessel body and an axial loading structure disposed on the upper part of the vessel body; the axial loading structure is connected to the sealing cap and extends through the vessel body; the test tubular column is coaxially arranged with the reaction vessel, and the outer side wall of the test tubular column, the inner side wall of the reaction vessel, and the sealing cap constitute a sealed tubular annulus; a fluid circulation system including an internal fluid circulation structure and an annular fluid circulation structure; the internal fluid circulation structure is in communication with the interior of the test tubular column and is used to fill the interior of the test tubular column with corrosive fluid and provide internal pressure; the annular fluid circulation structure is in communication with the tubular annulus and is used to inject corrosive fluid into the tubular annulus and provide confining pressure for the test tubular column.

[0007] In some embodiments, the sealing cap includes an upper sealing cap and a lower sealing cap, the upper part of the lower sealing cap being threadedly connected to the test column, and the lower part of the lower sealing cap being threadedly connected to the reaction vessel.

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

[0009] The vessel body has an annular injection port and an annular discharge port, and the annular fluid circulation structure is connected to the annular injection port through a pipeline.

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

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

[0012] The driving rod includes a first end connected to a stress loading head, which is fitted and connected to the stress loading disk. The second end of the driving rod passes through the stress loading disk and the reaction vessel and is placed outside the reaction vessel.

[0013] In some embodiments, the stress loading disk has a rectangular groove, and the stress loading head has cylindrical rollers;

[0014] The stress loading head is connected by a cylindrical roller and a rectangular groove in the stress loading disk.

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

[0016] 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.

[0017] The cylindrical boss is placed in the axial movement groove at the top of the reactor and is threadedly connected to the axial movement groove.

[0018] The drive rod has a mounting hole on its body outside the reactor, and the force-applying rod passes through the mounting hole.

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

[0020] The pipe-mounted fluid control device, pipe-mounted gas control device, and pipe-mounted venting device are connected in sequence to the bottom liquid flow hole via pipelines.

[0021] 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 connected in sequence.

[0022] The in-pipe gas control device includes a first high-pressure gas cylinder, a pressure reducing valve, and an in-pipe gas control valve connected in sequence, and the output end of the in-pipe gas control valve is connected to the bottom liquid flow hole.

[0023] The in-pipe drainage device is connected to the bottom liquid flow hole via a pipeline.

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

[0025] Annular fluid control device and annular venting device;

[0026] The annular fluid control device includes an annular fluid storage bottle, a second dual-plunger pump, and an annular fluid control valve connected in sequence, with the output end of the annular fluid control valve connected to the annular injection port.

[0027] The drainage device is connected to the annular drain hole via a pipeline.

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

[0029] The first back pressure loading device and the 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;

[0030] 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;

[0031] The outlet end of the back pressure valve of the second back pressure loading device is connected to the annular drain hole via a pipeline.

[0032] In some embodiments, the tubular stress corrosion testing apparatus further includes:

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

[0034] The temperature sensor is connected to the annular injection hole and the bottom liquid flow hole respectively, and is used to monitor the temperature of the corrosive fluid in the annular space of the injection string and the temperature of the corrosive fluid injected into the test string.

[0035] The pressure sensors are respectively connected to the back pressure valves of the first back pressure loading device and the second back pressure loading device, and are used to monitor the back pressure values ​​applied to the fluid circulation structure in the pipe and the annular fluid circulation structure.

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

[0037] A second aspect of this application provides a method for testing the stress corrosion of a tubing string, employing the tubing stress corrosion testing apparatus as described above, and comprising the following steps:

[0038] S1: Configure the corrosive fluid injected into the test tubing and the annulus of the tubing;

[0039] S2: Connect and install the reactor, the test column, the axial loading structure, the in-pipe fluid circulation structure, and the annular fluid circulation structure;

[0040] S3: Adjust the axial loading structure to apply stable axial tensile or compressive stress to the test tubing;

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

[0042] S5: Adjust the fluid circulation structure inside the tube, pump corrosive fluid into the tube string to be tested, maintain the pressure inside the tube string, and apply back pressure to the internal pressure value required for the test;

[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, the test tube was removed, processed, and the overall corrosion rate of the tube was calculated.

[0045] The stress corrosion testing device and method for tubing described in this application can be used to test tubing of various specifications, restore the actual size and shape of the downhole tubing, and conduct experiments using full-size tubing. This eliminates the influence of differences in processing and manufacturing processes between the sheet-like base material and the actual tubing on stress corrosion. It can accurately simulate the stress corrosion environment experienced by the tubing and conduct stress corrosion experiments on the inner and outer walls of the tubing to study the stress corrosion behavior of the tubing.

[0046] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0047] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without any inventive effort. In the drawings:

[0048] Figure 1 This is a schematic diagram of the structure of the tubular stress corrosion testing device of the present invention;

[0049] Figure 2 This is a cross-sectional view of the reaction vessel in the tubular stress corrosion testing device of the present invention;

[0050] Figure 3 This is a schematic diagram of the axial stress loading structure in the tubular stress corrosion testing device of the present invention;

[0051] Figure 4 This is a cross-sectional view of the axial stress loading structure in the tubular stress corrosion testing device of the present invention;

[0052] Figure 5 This is a schematic diagram of the drive rod in the tubular stress corrosion testing device of the present invention;

[0053] Figure 6 This is a cross-sectional view of the drive rod in the tubular stress corrosion testing device of the present invention;

[0054] Figure 7This is a structural diagram of the stress loading disk in the tubular stress corrosion testing device of the present invention;

[0055] Figure 8 This is a structural diagram of the stress loading head in the tubular stress corrosion testing device of the present invention;

[0056] Figure 9 This is a flowchart of the stress corrosion testing method for tubular columns according to the present invention;

[0057] Explanation of reference numerals in the attached figures

[0058] 1. Reactor body

[0059] 111 Insulation sleeve; 112 Axial motion groove

[0060] 12. Internal cavity of the test tube string 121

[0061] 13 Axial Loading Structure 131 Stress Loading Disc

[0062] 132 Drive rod 133 Stress loading head

[0063] 134 Rectangular groove 135 Cylindrical roller

[0064] 136 Intermediate rod 137 Cylindrical boss

[0065] 138 Mounting hole 139 Extension rod

[0066] 14. Tube string annulus 15. Upper sealing cap

[0067] 151 Annular rubber sleeve 152 Sealing cover plate

[0068] 16 Lower sealing cap 161 Annular rubber sealing gasket

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

[0070] 18 Annular injection port 19 Annular drainage port

[0071] 2. Fluid circulation structure inside the tube 21. Fluid storage bottle inside the tube

[0072] 22 First double plunger pump 23 In-pipe liquid control valve

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

[0074] 26. In-pipe gas control valve 27. In-pipe vent valve

[0075] 3. Annular Fluid Circulation Structure 31. Annular Fluid Storage Bottle

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

[0077] 34 Annular relief 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

[0082] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

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

[0084] like Figure 1 As shown, a tubular stress corrosion testing device includes a reaction system, which includes a reaction vessel 1, a test tubular column 12 disposed inside the reaction vessel 1, and sealing caps connected to the upper and lower ends of the test tubular column 12 respectively; the reaction vessel 1 includes a hollow vessel body 2 and an axial loading structure 112 disposed on the upper part of the vessel body 2; the axial loading structure 112 is connected to the sealing cap and extends out of the vessel body 2; the test tubular column 12 is coaxially arranged with the reaction vessel 1, and the outer side wall of the test tubular column 12, the inner side wall of the reaction vessel 1, and the sealing cap constitute a sealed tubular annulus 14; a fluid circulation system includes an internal fluid circulation structure 2 and an annular fluid circulation structure 3; the internal fluid circulation structure 2 is connected to the interior of the test tubular column 12 and is used to fill the interior of the test tubular column 12 with corrosive fluid and provide internal pressure; the annular fluid circulation structure 3 is connected to the tubular annulus 14 and is used to inject corrosive fluid into the tubular annulus 14 and provide confining pressure for the test tubular column 12.

[0085] This invention proposes a column stress corrosion testing device. This device can precisely simulate the actual stress and corrosion environment of CCUS well downhole tubing, enabling stress corrosion research on full-size tubing with its inner and outer walls under different stress and corrosion environments. Based on this device, stress corrosion tests can be conducted to study the stress corrosion of the inner and outer walls of the tubing under complex corrosive media conditions, measuring the corrosion rate, crack propagation rate, and predicting the tubing wall thickness variation, thus achieving stress corrosion evaluation of the tubing. Simultaneously, by adjusting the parameter values ​​of various influencing factors, the impact of key variable factors on the stress corrosion rate, crack initiation, and propagation patterns can be systematically explored, leading to a deeper understanding of the stress corrosion mechanism of the tubing. This not only fills the current gap in research on downhole tubing stress corrosion in the oil and gas well field but also provides more accurate and comprehensive guidance for the selection of CCUS well construction parameters, tubing materials, and annulus protection fluids.

[0086] like Figure 2 As shown, in some embodiments, the sealing cap includes an upper sealing cap 15 and a lower sealing cap 16. The upper part of the lower sealing cap 16 is threadedly connected to the test column 12, and the lower part of the lower sealing cap 16 is threadedly connected to the reactor 1. An annular rubber sealing gasket 161 is placed between the lower sealing cap 16 and the reactor body 2 of the reactor 1. A circular rubber sealing gasket 162 is adhered to the lower sealing cap 16. The circular rubber sealing gasket 162 contacts the bottom of the test column 12, together achieving the sealing between the inner cavity 121 of the test column 12 and the column annulus 14 under high temperature and high pressure conditions. The lower part of the upper sealing cap 15 is threadedly connected to the test column 12 through a threaded sealing plug. The upper part of the upper sealing cap 15 has a sealing cover plate 152. An annular rubber sleeve 151 is installed on the outer side of the sealing cover plate 152 to ensure the sealing of the column annulus 14.

[0087] The lower sealing cap 16 has a bottom liquid flow hole 17, and the internal fluid circulation structure 2 is connected to the bottom liquid flow hole 17 through a pipeline; the vessel body 2 has an annular injection hole 18 and an annular discharge hole 19, and the annular fluid circulation structure 3 is connected to the annular injection hole 18 through a pipeline. The corrosive fluid in the inner cavity 121 of the test column 12 flows in and out through the bottom liquid flow hole 17 on the lower sealing cap 16 via the internal fluid circulation structure 2; the corrosive fluid in the annular column flows in through the annular injection hole 18 on the vessel body 2 via the annular fluid circulation structure 3, and flows out through the annular discharge hole 19 on the vessel body 2 during discharge.

[0088] like Figure 3 and Figure 4As shown, in some embodiments, the axial loading structure 112 includes a stress loading disk 131 and a drive rod 132. The stress loading disk 131 is threadedly connected to the threaded joint of the upper sealing cover 15. A stress loading head 133 is connected to the first end of the drive rod 132, and the stress loading head 133 is fitted into the stress loading disk 131. The second end of the drive rod 132 passes through the stress loading disk 131 and the reaction vessel 1, and is located outside the reaction vessel 1. Specifically, as shown... Figure 7 and Figure 8 As shown, the stress loading disk 131 has a rectangular groove 134, and the stress loading head 133 has a cylindrical roller 135; the stress loading head 133 is connected to the rectangular groove 134 in the stress loading disk 131 by the cylindrical roller 135. The function of the axial loading structure 112 is to apply stable axial tensile or compressive stress to the test column 12. In actual operation, the axial tensile or compressive stress is applied to the test column 12 by the drive rod 132.

[0089] like Figure 5 and Figure 6 As shown, in some embodiments, the drive rod 132 further includes an intermediate rod 136, a cylindrical boss 137, a mounting hole 138, and a force-applying rod 139; the first end of the intermediate rod 136 is connected to the stress loading head 133, and the second end is threadedly connected to the cylindrical boss 137; the cylindrical boss 137 is placed in the axial movement groove 112 at the top of the reactor 1 and is threadedly connected to the axial movement groove 112; the drive rod 132 has a mounting hole 138 on its rod body outside the reactor 1, and the force-applying rod 139 passes through the mounting hole 138.

[0090] Specifically, the stress loading head 133, connected to the first end of the drive 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 itself and the axial movement groove 112, causing a change in the displacement of the axial loading structure 112, thereby applying compressive stress to the test column 12. The cylindrical boss 137 rotates in the opposite direction through the thread between itself and the axial movement groove 112, causing a change in the displacement of the axial loading structure 112. At this time, the stress loading head 133 is engaged with the cylindrical roller 135 and the rectangular groove 134 in the stress loading disk 131, thereby applying tensile stress to the test column 12. Therefore, this application applies axial stress to the test column 12 by changing the relative rotation direction between the cylindrical boss 137 and the axial movement groove 112, causing the axial loading structure 112 to displace axially. The intermediate rod 136 passes through the vessel body 2 of the reactor 1 and is sealed to the vessel body 2 by an annular rubber sleeve 151. The intermediate rod 136 is connected to the cylindrical boss 137 by threads for easy installation and disassembly. The drive rod 132 has a mounting hole 138 on its rod body outside the vessel body 2. The force-applying rod 139 passes through the mounting hole 138 to facilitate rotating the cylindrical boss 137 to a designated position to apply stress. After the cylindrical boss 137 reaches the designated position, the force-applying rod 139 can be removed to prevent accidental alteration of 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 drain device connected in sequence to the bottom liquid flow hole 17 via 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 connected in sequence; 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 connected in sequence, with the output end of the in-pipe gas control valve 26 connected to the bottom liquid flow hole 17; the in-pipe drain device is connected to the bottom liquid flow hole 17 via pipelines.

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

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

[0094] Specifically, the corrosive fluid stored in the annular fluid storage bottle 31 is pumped into the annulus 14 of the tubing through the annular injection port 18 by the second double plunger pump 32; the annular fluid control valve 33 controls the inflow of the corrosive fluid into the annulus 14 of the tubing; during drainage, the corrosive fluid in the annulus 14 of the tubing flows out through the annular drain port 19; the annular venting device is the annular venting valve 34, which controls the outflow of the corrosive fluid from the annulus 14 of the tubing.

[0095] In some embodiments, 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 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 annular drain 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 back pressure for the fluid circulation structure 2 inside the pipe, and the back pressure gas control valve 42 controls the opening and closing of the second high-pressure gas cylinder 41. The second high-pressure gas cylinder 41 provides a stable gas source pressure to the back pressure valve 43 to control and realize the pressure loading inside the pipe column; the second back pressure loading device provides back pressure for the annular circulation structure, and the back pressure gas control valve 42 controls the opening and closing of the second high-pressure gas cylinder 41. The second high-pressure gas cylinder 41 provides a stable gas source pressure to the back pressure valve 43, and the annular confining pressure loading is realized through the annular venting valve 34.

[0097] In some embodiments, the tubing stress corrosion testing device further includes a monitoring system 5, which includes a temperature sensor 51, a pressure sensor 52, and a data monitoring computer 53. The temperature sensor 51 is connected to the annular injection port 18 and the bottom flow port 17, respectively, and is used to monitor the temperature of the corrosive fluid injected into the annulus 14 of the tubing and the corrosive fluid injected into the tubing 12 under test. The pressure sensor 52 is connected to the back pressure valves 43 of the first back pressure loading device and the second back pressure loading device, respectively, and is used to monitor the back pressure value applied to the fluid circulation structure 2 in the tubing and the fluid circulation structure 3 in the annulus. The data monitoring computer 53 is connected to the temperature sensor 51 and the pressure sensor 52.

[0098] The monitoring system 5 is used to monitor the temperature and pressure 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 tubing. 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 connected to the annular injection port 18 and the bottom fluid flow port 17, respectively, to monitor the temperature of the corrosive fluid injected into the annulus 14 of the tubing and the corrosive fluid injected into the tubing 12 under test. The pressure sensor 52 is connected to the two back pressure valves 43, respectively, to monitor the back pressure values ​​applied to the fluid circulation structure 2 and the annular fluid circulation structure 3, i.e., the tubing internal pressure and the annular confining pressure. The temperature sensor 51 and the pressure sensor 52 are connected to the data monitoring computer 53 to monitor the changes of each parameter throughout the process and maintain parameter stability.

[0099] The tubing stress corrosion testing device provided in this application is applicable to full-size tubing strings and can accurately simulate the actual stress state and complex corrosion environment of CCUS well tubing strings. It simultaneously performs stress corrosion tests on the inner and outer walls of the tubing string to assess stress corrosion, eliminating the influence of differences in processing and manufacturing processes between the sheet-like base material and the actual tubing string on stress corrosion. Considering the actual stress state of the tubing string, the tubing stress corrosion testing device provided in this application can simultaneously apply axial stress, internal tubing pressure, and annular confining pressure to the tubing string under test, overcoming the shortcomings of existing devices that can only apply a single stress or simple stress combination and cannot simulate the complex mechanical environment of downhole tubing strings. Considering the downhole... The inner and outer walls of the tubing are exposed to different stress corrosion environments. The tubing stress corrosion testing device provided in this application can simultaneously investigate the stress corrosion of the inner and outer walls of the tubing in a single test, studying the stress corrosion of the tubing 12 under test from a holistic perspective. This eliminates the problem that stress corrosion experiments conducted on only one side of the tubular sample do not match reality. In addition, the tubing stress corrosion testing device provided in this application is highly applicable and fully functional. The fluid injected into the tubing 12 under test can switch between corrosive gas and corrosive liquid. It can not only conduct stress corrosion studies on tubing or casing, but can also be simplified to conduct stress corrosion studies on only one side of the tubing wall, thus having the advantage of multiple uses for one device.

[0100] like Figure 9 As shown, the second aspect of this application provides a method for testing the stress corrosion of a tubing string, employing the tubing string stress corrosion testing apparatus as described above, and including the following steps:

[0101] S1: Prepare the corrosive fluid to be injected into the test tubing 12 and the annulus 14;

[0102] In the preliminary preparation, the temperature parameters of the corrosive fluid injected into the test string 12 and the annulus 14, as well as the parameters of the internal pressure, annular confining pressure, and axial stress on the test string 12, were determined based on the field data of the CCUS well. The corrosive fluid injected into the test string 12 and the annulus 14 was prepared according to the actual downhole fluid. The dimensions of the test string 12 were recorded, and the mass of the test string was weighed using a high-precision balance.

[0103] S2: Connect and install the reactor 1, the test tube 12, the axial loading structure 112, the in-tube fluid circulation structure 2, and the annular fluid circulation structure 3.

[0104] Connect the fluid pipeline and monitoring line, store the prepared corrosive fluid in the designated sealed and insulated storage tank, adjust to the designated temperature, and check that all valves, pumps, sensors, and monitoring systems are in good working order and that the gas cylinder pressure is sufficient.

[0105] S3: Adjust the axial loading structure 112 to apply stable axial tensile or compressive stress to the test tube 12;

[0106] Depending on the magnitude of the axial stress on the tubing, adjust the thread of the force-applying rod to screw in or out to the specified displacement, and apply the corresponding stress to the tubing 12 to be tested. After adjustment, remove the force-applying rod 139 to prevent accidental changes to the axial stress.

[0107] S4: Adjust the annular fluid circulation structure 3 to pump corrosive fluid into the annulus 14 of the tubing to maintain the annular confining pressure;

[0108] Open the back pressure gas control valve 42 in the second back pressure loading device to open the second high-pressure gas cylinder 41, open the annular vent valve 34, and load the back pressure of the back pressure valve 43 to the annular confining pressure value required for the experiment; open the annular liquid control valve 33 and the second double plunger pump 32 to pump the annular corrosion fluid into the annulus 14 of the tubing. When fluid is observed flowing out of the annular vent valve 34, close the second double plunger pump 32 and close the annular liquid control valve 33. At this time, stop pumping and maintain the annular confining pressure.

[0109] S5: Adjust the fluid circulation structure 2 inside the tube to pump corrosive fluid into the test tube 12, maintain the pressure inside the tube, and apply back pressure to the internal pressure value required for the test.

[0110] Open the back pressure gas control valve 42 in the first back pressure loading device to open the second high-pressure gas cylinder 41, close the in-tube drain valve 27, and load the back pressure of the back pressure valve 43 to the required column pressure value for the experiment; open the in-tube liquid control valve 23 and the first double plunger pump 22 to pump the corrosive fluid into the column 12 to be tested. When fluid is observed flowing out from the other end of the back pressure valve 43, close the first double plunger pump 22 and the in-tube liquid control valve 23; or control the in-tube gas control valve 26 to open the first high-pressure gas cylinder 24 to inject corrosive gas into the column 12 to be tested. When fluid is observed flowing out from the other end of the back pressure valve 43, control the in-tube gas control valve 26 to close the first high-pressure gas cylinder 24 and maintain the column 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] Throughout the test, the temperature of the fluid injected into the annulus 14 and the test column 12, as well as the pressure at the back pressure valve 43, were monitored to ensure that the experimental temperature and pressure values ​​remained stable within the preset values.

[0113] S7: After the experiment, the test tube 12 was removed, processed, and the overall corrosion rate of the tube was calculated.

[0114] If the test tube 12 breaks during the test, it proves that the test tube 12 has suffered stress corrosion failure, and the sample should be removed. If the test tube 12 does not break during the test, the test experiment should be carried out according to the predetermined cycle, such as 30 days, 60 days, etc., and the test tube 12 should be removed after the experiment.

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

[0116] After drying, the change in diameter of the inner and outer walls of the test tube 12 is measured every 1 cm along the axial direction; the final mass of the tube is measured, and the overall corrosion rate of the tube is calculated using the following formula:

[0117]

[0118] Among them, C R The corrosion rate of the test string 12 is represented by mm / a; ΔW is the mass loss of the test string 12 before and after the test, in g; A is the exposed area of ​​the material of the test string 12, in cm². 2 T represents the time it takes for corrosion to occur in the test tubing 12, in hours; ρ represents the density of the material in the test tubing 12, in g / cm³. 3"87600" is a unit conversion constant, which is obtained by converting the time unit from hours to years (365×24 hours) and the area unit from square centimeters to square meters.

[0119] In addition, SEM scanning electron microscopy can be used to observe the corrosion defects and cross-sectional micromorphology of the test column 12, X-ray diffraction can be used to identify the composition of corrosion products, and EDS energy dispersive spectroscopy can be used to analyze the elemental composition of the corrosion area, so as to conduct a more in-depth study on the stress corrosion behavior and mechanism of the inner and outer walls of the test column 12.

[0120] The proposed method for testing tubing stress corrosion in CCUS wells enables stress corrosion testing experiments using a tubing stress corrosion testing device. This allows for the study of stress corrosion on the inner and outer walls of the tubing, measurement of corrosion rate and crack propagation rate, and prediction of tubing wall thickness variation, thus achieving stress corrosion evaluation. Furthermore, by adjusting the parameters of various influencing factors, the method systematically explores the impact of key variables on stress corrosion rate, crack initiation, and propagation, providing in-depth research into the stress corrosion mechanism of tubing. This not only fills the current gap in research on downhole tubing stress corrosion in the oil and gas well field but also provides more accurate and comprehensive guidance for the selection of CCUS well construction parameters, tubing materials, and annular protective fluids.

[0121] This application provides a tubing stress corrosion testing device and method capable of testing tubing of various specifications, restoring the actual size and shape of the downhole tubing, and using full-size tubing for experiments. This eliminates the influence of differences in processing and manufacturing processes between sheet-like base materials and actual tubing on stress corrosion. Considering the actual stress state of CCUS injection well tubing, the device can simultaneously apply axial stress, internal tubing pressure, and annular confining pressure to the tubing, overcoming the shortcomings of existing devices that can only apply single stress or simple stress combinations and cannot simulate the complex mechanical environment of downhole tubing. Considering that the inner and outer walls of the downhole tubing are in different stress corrosion environments, the device simultaneously investigates stress corrosion on both the inner and outer walls of the tubing during a single test, studying the stress corrosion of the tubing from a holistic perspective, eliminating the problem of inconsistencies between stress corrosion experiments conducted on only one side of the tubular sample and reality. Depending on whether the tubing to be tested (12) is tubing or casing, and the different corrosive media on the inner and outer walls, corrosive gases or liquids can be injected into the tubing to accurately simulate the stress corrosion environment and conduct stress corrosion experiments on the inner and outer walls of the tubing to study the stress corrosion behavior of the tubing. Furthermore, the invention can perform stress corrosion tests on the inner wall, outer wall, or both walls simultaneously. It can also conduct sensitivity analyses on key influencing factors such as temperature, axial pressure, internal pressure, annular confining pressure, and the properties of the corrosive fluid inside the pipe and in the annulus.

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

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

[0124] In one embodiment, the tubular stress corrosion testing device of this application can investigate the effect of temperature on stress corrosion. Specifically, in actual operation, the axial stress, tubular internal pressure, annular confining pressure, and properties of the corrosive fluid inside and in the annulus of the tubular column 12 are kept constant, the temperature of the corrosive fluid stored in the storage tank is adjusted, and multiple tests are conducted to investigate the effect of temperature on stress corrosion.

[0125] In one embodiment, the tubular stress corrosion testing device of this application can investigate the effect of axial pressure on stress corrosion. Specifically, in actual operation, the tubular internal pressure, annular confining pressure, properties of the corrosive fluid inside the tubular tube and in the annular space, and temperature are kept constant. The displacement of the axial loading structure 112 is adjusted, and multiple tests are conducted to investigate the effect of axial pressure on stress corrosion.

[0126] In one embodiment, the tubular stress corrosion testing device of this application can investigate the effect of annular confining pressure on stress corrosion. Specifically, in actual operation, the axial stress, tubular internal pressure, properties of the corrosive fluid inside the tubular tube and in the annular space, and temperature are kept constant. The back pressure value in step S4 is adjusted to control the magnitude of the annular confining pressure. Multiple tests are conducted to investigate the effect of annular confining pressure on stress corrosion.

[0127] In one embodiment, the tubing stress corrosion testing device of this application can investigate the influence of tubing internal pressure on stress corrosion. Specifically, in actual operation, the axial stress, annular confining pressure, properties of the corrosive fluid inside the tubing and the annular space, and temperature of the tubing to be tested 12 are kept constant. The back pressure value in step S5 is adjusted to control the magnitude of the tubing internal pressure. Multiple tests are conducted to investigate the influence of tubing internal pressure on stress corrosion.

[0128] In one embodiment, the tubular stress corrosion testing device of this application can investigate the influence of the properties of the corrosive medium on stress corrosion. Specifically, in actual operation, the axial stress, tubular internal pressure, annular confining pressure, and temperature of the corrosive fluid inside and in the annulus of the tubular column 12 are kept constant. The properties of the corrosive fluid inside the tubular column and the corrosive fluid in the annulus configured in step S1 are adjusted, and multiple tests are conducted to investigate the influence of the properties of the corrosive medium on stress corrosion.

[0129] The tubular stress corrosion testing device described in this application can also perform other testing experiments, which will not be elaborated here.

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

[0131] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0132] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0133] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

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

Claims

1. A tubular stress corrosion testing device, characterized in that, include: A reaction system includes a reaction vessel, a test tube column disposed inside the reaction vessel, and sealing caps connected to the upper and lower ends of the test tube column respectively. The reaction vessel includes a hollow vessel body and an axial loading structure disposed on the upper part of the vessel body. The sealing cap includes an upper sealing cap. The axial loading structure is connected to the sealing cap and extends out of the vessel body. The axial loading structure includes an umbrella-shaped stress loading head and a stress loading disk threadedly connected to the upper sealing cap. The stress loading disk has a rectangular groove, and the stress loading head has a cylindrical roller. The stress loading head is fitted and connected to the rectangular groove in the stress loading disk through the cylindrical roller. The test column is coaxially arranged with the reaction vessel, and the outer wall of the test column, the inner wall of the reaction vessel, and the sealing cap form a sealed column annulus. The fluid circulation system includes an internal fluid circulation structure and an annular fluid circulation structure; the internal fluid circulation structure is connected to the interior of the test tube and is used to fill the interior of the test tube with corrosive fluid and provide internal pressure; the annular fluid circulation structure is connected to the annulus of the tube and is used to inject corrosive fluid into the annulus of the tube and provide confining pressure for the test tube.

2. The tubular stress corrosion testing device according to claim 1, characterized in that: The sealing cap includes a lower sealing cap, the upper part of which is threadedly connected to the test column, and the lower part of which is threadedly connected to the reaction vessel. The lower sealing cap has a bottom liquid flow hole, and the internal fluid circulation structure is connected to the bottom liquid flow hole through a pipeline; The vessel body has an annular injection port and an annular discharge port, and the annular fluid circulation structure is connected to the annular injection port through a pipeline.

3. The tubular stress corrosion testing device according to claim 2, characterized in that, The axial loading structure includes: The driving rod includes a first end connected to a stress loading head, which is fitted and connected to the stress loading disk. The second end of the driving rod passes through the stress loading disk and the reaction vessel and is placed outside the reaction vessel.

4. The tubular stress corrosion testing device according to claim 3, characterized in that, The drive rod also includes: Intermediate rod, cylindrical boss, mounting hole and force-adding 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 reactor and is threadedly connected to the axial movement groove. The drive rod has a mounting hole on its body outside the reactor, and the force-applying rod passes through the mounting hole.

5. The tubular stress corrosion testing device according to claim 2, characterized in that, The fluid circulation structure inside the pipe includes: The pipe-mounted fluid control device, pipe-mounted gas control device, and pipe-mounted venting device are connected in sequence to the bottom liquid flow hole via 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 connected in sequence. The in-pipe gas control device includes a first high-pressure gas cylinder, a pressure reducing valve, and an in-pipe gas control valve connected in sequence, and the output end of the in-pipe gas control valve is connected to the bottom liquid flow hole. The in-pipe drainage device is connected to the bottom liquid flow hole via a pipeline.

6. The tubular stress corrosion testing device according to claim 2, characterized in that, The annular fluid circulation structure includes: Annular fluid control device and annular venting device; The annular fluid control device includes an annular fluid storage bottle, a second dual-plunger pump, and an annular fluid control valve connected in sequence, with the output end of the annular fluid control valve connected to the annular injection port. The drainage device is connected to the annular drain hole via a pipeline.

7. The tubular stress corrosion testing device according to claim 2, characterized in that, The fluid circulation system also includes: The first back pressure loading device and the 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 drain hole via a pipeline.

8. The tubular stress corrosion testing apparatus according to claim 7, characterized in that, Also includes: A monitoring system, comprising a temperature sensor, a pressure sensor, and a data monitoring computer; The temperature sensor is connected to the annular injection hole and the bottom liquid flow hole respectively, and is used to monitor the temperature of the corrosive fluid in the annular space of the injection string and the temperature of the corrosive fluid injected into the test string. The pressure sensors are respectively connected to the back pressure valves of the first back pressure loading device and the second back pressure loading device, and are used to monitor the back pressure values ​​applied to the fluid circulation structure in the pipe and the annular fluid circulation structure. The data monitoring computer is connected to temperature and pressure sensors.

9. A method for testing stress corrosion of tubular columns, characterized in that, The tubular stress corrosion testing apparatus as described in any one of claims 1-8 comprises the following steps: S1: Configure the corrosive fluid injected into the test tubing and the annulus of the tubing; S2: Connect and install the reactor, the test column, the axial loading structure, the in-pipe fluid circulation structure, and the annular fluid circulation structure; S3: Adjust the axial loading structure to apply stable axial tensile or compressive stress to the test tubing; S4: Adjust the annular fluid circulation structure to pump corrosive fluid into the annular space of the tubing to maintain the annular confining pressure; S5: Adjust the fluid circulation structure inside the tube, pump corrosive fluid into the tube string to be tested, maintain the pressure inside the tube string, and apply back pressure to the internal pressure value required for the test; 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, the test tube was removed, processed, and the overall corrosion rate of the tube was calculated.

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