Stress corrosion evaluation device and stress corrosion evaluation method under simulated dynamic condition

Abstract

The invention discloses a stress corrosion evaluation device and a stress corrosion evaluation method under simulated dynamic conditions, the stress corrosion evaluation device comprises a plurality of mounting plates, a shell and a pipe body, two ends of the shell are respectively connected with a first fixing plate and a second fixing plate, and the first fixing plate and the second fixing plate are connected through a rotating shaft; two ends of each mounting plate are respectively connected with the first fixing plate and the second fixing plate; a plurality of clamps are fixed on each mounting plate; a driving motor is arranged on the first fixing plate or the second fixing plate, and the output end of the driving motor is connected with the rotating shaft; the shell is further provided with a plurality of heating pieces and a temperature measuring instrument. The shell is provided with a feeding port and a discharging port, and a first sealing plug and a second sealing plug are detachably arranged on the feeding port and the discharging port respectively. Different stresses can be loaded / test pieces made of different materials / parallel samples with the same stress and the like can be adopted according to test requirements, one-time experiment under the same working condition is realized, the process is simplified, and the experiment time is shortened.

Description

Technical Field

[0001] The invention relates to the technical field of oil and natural gas exploitation, and in particular to a stress corrosion evaluation device and a stress corrosion evaluation method under simulated dynamic conditions. Background Art

[0002] With the continuous growth of the global natural gas market, countries around the world are paying more and more attention to the development and utilization of unconventional natural gas, especially shale gas. China's shale gas resources are very rich, with recoverable resources reaching 25.0×10 12 m 3 Among them, the recoverable shale gas resources in the Sichuan Basin can reach 4.4×10 12 m 3 It is the region with the richest shale gas resources in China, and southern Sichuan is the main battlefield for shale gas development.

[0003] Research has found that the corrosion caused by the coexistence of carbon dioxide and bacteria in shale gas is the main cause of failure. According to statistics, the failure of a shale gas block station can reach 180 times, of which the failure of the sewage pipeline in the skid accounts for 62.22%, the failure of the gas production pipeline accounts for 25%, and the failure of the buried sewage pipeline accounts for 8.33%. Weld failure accounts for 66.67% of the total failure. From the current characteristics of weld failure, it can be seen that the main characteristics of the failure of the station process pipeline are corrosion pits, pits, cracks, etc. along the welds because the bactericidal corrosion inhibitor was not added in the early stage, while the main characteristics of the failure of the gas gathering pipeline are cracks / cracks along the welds because the bactericidal corrosion inhibitor was fully added, but there are no obvious corrosion characteristics.

[0004] Through the failure analysis of the N214 gas gathering pipeline and the N209H34 gas gathering pipeline, it was determined that there were many factors that caused cracking in the circumferential weld, such as high stress concentration, local high hardness, and high oxide inclusions. However, it is urgent to clarify whether the coupling effect of the on-site working environment containing carbon dioxide and SRB and the weld quality is the cause of the cracking, and whether the main controlling factors of the cracking are needed.

[0005] In order to study the causes of circumferential weld cracking under shale gas conditions, it is necessary to develop a set of test equipment that has stress loading conditions and simulates the dynamic environment of the field to clarify the cracking behavior characteristics of shale gas welds.

[0006] After investigation, the utility model patent application number is CN202222074791.5, which introduces a dynamic high temperature and high pressure supercritical carbon dioxide stress corrosion test device. It is mainly composed of ultra-pure CO2 cylinders, valves, pressure reducing valves, filters, supercritical fluid pumps, mass flow meters, pressure gauges, heat exchangers, thermocouples, preheaters, stress corrosion systems, coolers, cooling water valves, cooling water pressure gauges, circulating water coolers, cooling water thermocouples, back pressure valves, gas handling systems, control systems, etc. The device can meet the needs of stress corrosion tests on samples under dynamic high temperature and high pressure supercritical CO2 conditions, including slow strain rate tensile tests and in-situ measurement tests of stress corrosion crack growth rates. At the same time, important test parameters such as gas flow, temperature, and pressure can be recorded and accurately controlled during the test.

[0007] Invention patent CN202211514563.3 introduces a stress corrosion device under fluid scouring conditions and a method of use. A stress corrosion device under fluid scouring conditions belongs to the field of scouring corrosion test technology, including a frame, a power input device is installed on the bottom plate of the frame, a liquid reservoir and a hydraulic stretcher are installed on the frame, a cover plate is installed on the top of the liquid reservoir, a clamp is installed in the liquid reservoir, and the scouring angle of attack is changed by rotating the clamp. A method of using a stress corrosion device under fluid scouring conditions includes the following steps: connecting the working electrode wire to the top of the sample; installing the treated sample on the clamp; stretching the sample; installing the stretched sample in the liquid reservoir; filling the liquid reservoir with experimental medium; closing the cover and fastening the mechanical lock; starting the motor and the heating rod, and starting the electrochemical test after the flow rate and temperature of the experimental medium are stable. The fixed column is inserted into the fixed slot by rotating the clamp to change the scouring angle of attack, which solves the problem that the previous scouring corrosion experimental device cannot apply tensile stress and change the angle of attack.

[0008] The inventors found that the prior art has at least the following problems:

[0009] ① Existing dynamic stress corrosion test devices all use tensile force as the stress environment for stress corrosion evaluation;

[0010] ② Existing dynamic stress corrosion test equipment cannot meet the needs of evaluating multiple stress states, multiple materials, and multiple samples at the same time;

[0011] ③ The existing dynamic stress corrosion test method is cumbersome to operate and has no visual interface. It is impossible to directly obtain information on bacterial growth under shale gas working conditions. Summary of the invention

[0012] The technical problem to be solved by the present invention is that the existing dynamic stress corrosion test device cannot meet the requirements of simultaneously evaluating multiple stress states, multiple materials, and multiple samples.

[0013] The first object of the present invention is to provide a stress corrosion evaluation device under simulated dynamic conditions, comprising a plurality of mounting plates, a shell and a tube body, wherein the two ends of the shell are respectively connected to a first fixing plate and a second fixing plate, and the first fixing plate and the second fixing plate are connected via a rotating shaft;

[0014] Each of the mounting plates is arranged along the axial direction of the housing, and both ends of each of the mounting plates are respectively connected to the first fixing plate and the second fixing plate; a plurality of clamps are fixed on each of the mounting plates;

[0015] A driving motor is arranged on the first fixing plate or the second fixing plate, and the output end of the driving motor is connected to the rotating shaft; a plurality of heating elements and a temperature measuring instrument are also arranged on the shell;

[0016] The shell body is provided with a feeding port and a discharging port. The feeding port is detachably provided with a first sealing plug, and the discharging port is detachably provided with a second sealing plug.

[0017] Beneficial effects of the present invention: The present invention sets multiple fixtures, and different fixtures can load different stresses, which can meet the technical requirements of evaluating multiple samples, multiple stresses and multiple materials at the same time, and the operation is simple. According to the test requirements, different stresses can be loaded / test pieces of different materials can be used / parallel samples of the same stress can be tested under the same working conditions, and the process and experimental time can be simplified.

[0018] As a possible design, the first fixing plate is provided with a plurality of first slots, the second fixing plate is provided with a plurality of second slots, one end of the mounting plate is fixed in the first slot and the other end is fixed in the second slot. The mounting plate is installed in a detachable manner to facilitate the installation of the fixture.

[0019] As a possible design, at least one first card slot and one second card slot are included on the same vertical line along the axial direction of the rotating shaft, and the two ends of the mounting plate are respectively clamped in the first card slot and the second card slot on the same vertical line, so that the mounting plate is installed along the axial direction of the rotating shaft.

[0020] As a possible design, a visual window is provided on the housing, through which information on bacterial growth can be directly obtained under shale gas working conditions.

[0021] As a possible design, the viewing window and the housing are detachably connected to facilitate installation of the clamp.

[0022] As a possible design, the two ends of the rotating shaft pass through the first fixing plate and the second fixing plate respectively, one end of the rotating shaft is connected to the output end of the motor and the other end is connected to a base. Providing a base is conducive to the stable test process and prevents the stress corrosion evaluation device from tipping over.

[0023] As a possible design, a plurality of support columns are further arranged between the first fixing plate and the second fixing plate, and both ends of each support column are respectively connected to the first fixing plate and the second fixing plate, so as to further enhance the stability of the stress corrosion evaluation device.

[0024] As a possible design, the viewing window includes a flange arranged on the shell, and a transparent sheet is arranged on the flange.

[0025] As a possible design, the transparent sheet is made of tempered glass; preferably, the tempered glass includes organic glass or quartz glass.

[0026] A second object of the present invention is to provide an evaluation method based on the above-mentioned stress corrosion evaluation device, comprising:

[0027] Prepare simulated water according to the anion and cation composition of the on-site flowback fluid or directly use the on-site flowback fluid, wherein: the simulated water and the on-site flowback fluid are deoxygenated and carbon dioxide gas is introduced before use;

[0028] Adjust the loading stress according to the test requirements, install test pieces with different materials on different fixtures, and test pieces with the same stress in parallel;

[0029] The fixture after stress loading is installed on the mounting plate, and then the mounting plate is fixed to the first fixing plate and the second fixing plate;

[0030] The stress corrosion evaluation device is tested for leaks, replaced with air, and filled with simulated water or on-site flowback fluid in sequence;

[0031] Stress corrosion evaluation device for seals, starter motors and heating elements;

[0032] During the test, observe the changes in the test specimen and simulated liquid. If any abnormality is found, stop the experiment in time and repeat the experiment again.

[0033] The beneficial effects of the present invention are as follows: the evaluation method disclosed in the present invention is simple to operate, and can realize simultaneous testing of multiple stresses, multiple materials, and multiple samples as well as parallel testing under the same working conditions, which is beneficial to the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0035] Figure 1 It is a schematic diagram of the overall structure of the stress corrosion evaluation device disclosed in an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of the internal structure of a stress corrosion evaluation device disclosed in an embodiment of the present invention;

[0037] Figure 3 It is a schematic diagram of the structure of the flange in an embodiment of the present invention;

[0038] Figure 4 for Figure 3 Schematic diagram of the C direction;

[0039] Figure 5 It is a schematic diagram of the structure of the flange cover in an embodiment of the present invention;

[0040] Figure 6 It is a structural schematic diagram of a housing in an embodiment of the present invention;

[0041] Figure 7 It is a structural schematic diagram of a mounting plate in an embodiment of the present invention;

[0042] Figure 8 It is a schematic diagram of the structure after the rotating shaft, the first fixing plate and the second fixing plate are assembled in an embodiment of the present invention;

[0043] Fig. 9 It is a schematic structural diagram of the first fixing plate in an embodiment of the present invention;

[0044] Fig.10 is a schematic structural diagram of a rotating shaft in an embodiment of the present invention;

[0045] Fig.11 for Fig.10 Schematic diagram of the middle BB section;

[0046] Fig.12 is a schematic structural diagram of a second fixing plate in an embodiment of the present invention;

[0047] Fig.13 for Fig.12 Schematic diagram of the middle AA section;

[0048] Fig.14 Schematic diagram of the structure of the clamp in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0050] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0051] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0052] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0053] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] Existing devices for stress corrosion evaluation only use tensile force as the stress environment for stress corrosion evaluation, and are unable to test multiple materials, multiple samples, and multiple stress states simultaneously under the same working conditions (i.e., the corrosion liquid flow rate, temperature, and corrosion liquid are all the same).

[0055] like Figure 1-14 As shown, an embodiment of the present invention provides a stress corrosion evaluation device under simulated dynamic conditions. Figure 1-14 As shown, the stress corrosion evaluation device includes a plurality of mounting plates 5, a shell 1 and a tube body, wherein the two ends of the shell 1 are respectively connected to a first fixing plate 2 and a second fixing plate 3, and the first fixing plate 2 and the second fixing plate 3 are connected via a rotating shaft 4;

[0056] Each of the mounting plates 5 is arranged along the axial direction of the housing 1, and both ends of each of the mounting plates 5 are respectively connected to the first fixing plate 2 and the second fixing plate 3; a plurality of clamps 6 are fixed on each of the mounting plates 5;

[0057] A driving motor 7 is disposed on the first fixing plate 2 or the second fixing plate 3, and the output end of the driving motor 7 is connected to the rotating shaft 4; a plurality of heating elements 9 and a temperature measuring instrument 8 are also disposed on the housing 1;

[0058] The shell 1 is provided with a feeding port and a discharging port. The feeding port is detachably provided with a first sealing plug, and the discharging port is detachably provided with a second sealing plug.

[0059] By setting up a plurality of fixtures 6, the samples installed on some of the fixtures 6 can be different, and the stresses applied by some of the fixtures 6 can also be different, wherein: the samples installed on some of the fixtures 6 can be the same, and the stresses applied by some of the fixtures 6 can also be the same, thereby achieving parallel testing of samples under the same working conditions, testing under different stress states, and testing of different samples, the components are simple to operate, and time is saved.

[0060] In actual application, the sample needs to be fixed on the fixture 6 first, and then stress is applied to the fixture 6, and then the fixture 6 is installed on the mounting plate 5. Since it is a corrosion resistance test, it is necessary to prepare corresponding simulated water or directly use the on-site return fluid. Since the return fluid itself contains a large number of bacteria, corresponding bacteria must also be added to the simulated water. To avoid the influence of dissolved oxygen in the simulated fluid and the on-site return fluid on the corrosion results, the oxygen in it needs to be removed before use and carbon dioxide gas needs to be introduced, and the concentration of carbon dioxide needs to meet the test requirements.

[0061] After the fixture 6 is installed, the entire stress corrosion evaluation device is subjected to a leakage test, specifically as follows: first, clean water is introduced into the stress corrosion evaluation device. After the clean water is drained, nitrogen / methane and other gases are injected into the stress corrosion evaluation device through the feed port to replace the air. After the air is completely exhausted, simulated water or on-site return fluid is injected.

[0062] The entire stress corrosion evaluation device is sealed, and the rotation speed of the drive motor 7 and the heating temperature of the simulated fluid or the on-site return fluid are set.

[0063] If it is necessary to describe the crack propagation characteristics under this condition, microcracks can be prefabricated on the sample for testing.

[0064] Since the on-site return fluid or simulated water contains bacteria and other microorganisms, in order to better observe the corrosion situation, such as Figure 1 and 2 As shown, a visual window is provided on the aforementioned shell, through which the survival status of the microorganisms during the test process can be observed.

[0065] In order to facilitate the installation of the mounting plate 5, as Figure 4-7 Shown, the visual window can be set to a detachable mode. The visual window is installed again after the mounting plate 5 is installed.

[0066] The detachable method of the visible window is as follows:

[0067] A window 10 is provided on the housing 1, and a flange assembly 11 is provided on the window 10. The flange assembly 11 includes a flange 12, a flange cover 17, a flange sealing gasket, a transparent sheet, a sealing gasket and a sealing cover which are provided in sequence from the window 10 to the outside of the housing 1. The material of the transparent sheet can be selected according to the requirements of the actual test, such as the test pressure and temperature. The transparent sheet and the sealing gasket of different materials can be replaced according to the test requirements by being arranged in a detachable manner. The transparent sheet can be made of common transparent materials in the art, such as organic glass, quartz glass, etc. The sealing gasket can be made of common rubber materials, such as hydrogenated nitrile rubber, silicone rubber and tetrafluoroethylene, etc.

[0068] The clamp 6 can be a common clamp in the art, or it can be Figure 8 As shown, the fixture 6 is C-shaped, with grooves at both ends of the C-shaped, and the sample test piece is placed in the C-shaped cavity. At the same time, a stopper is set at the opening of the C-shaped to support the sample test piece to prevent it from falling. The two ends of the C-shaped serve as support points for the two ends of the stopper. In order to prevent the stopper from displacement as much as possible during the test, fixed blocks can be set at both ends of the stopper, and the fixed blocks are placed in the grooves during installation.

[0069] The clamp 6 and the mounting plate 5 may be connected by bolts or by fixing pins. The clamp may also be detachably connected to the rotating shaft, for example, by bolts.

[0070] like Figure 2 As shown, the first fixing plate 2 is provided with a plurality of first slots 13, the second fixing plate 3 is provided with a plurality of second slots 14, one end of the mounting plate 5 is fixed in the first slot 13 and the other end thereof is fixed in the second slot 14. Generally, the first fixing plate 2 and the second fixing plate 3 are both circular, and the first slots 13 and the second slots 14 can be provided along the circumference.

[0071] In actual application, according to the sizes of the mounting plate 5 and the fixture 6, a plurality of fixture installation sites can be provided on the mounting plate 5, and as many fixtures 6 as possible can be installed to meet the test of multiple situations at one time.

[0072] like Figure 2 As shown, at least one first card slot 13 and one second card slot 14 are included on the same vertical line along the axial direction of the rotating shaft 4, and both ends of the mounting plate 5 are respectively clamped in the first card slot 13 and the second card slot 14 on the same vertical line, so as to install as many clamps 6 as possible.

[0073] In a possible implementation, in order to facilitate the smooth installation of the clamp, the diameters of the first fixing plate 2 and the second fixing plate 3 are both larger than the diameter of the rotating shaft, and notches can be set at both ends of the mounting plate 5, and the portions at the notches are clamped in the first card slot and the first card slot.

[0074] In one possible implementation, Figure 1 and 2 As shown, both ends of the rotating shaft 4 pass through the first fixing plate 2 and the second fixing plate 3 respectively, one end of the rotating shaft 4 is connected to the output end of the driving motor 7 and the other end of the rotating shaft 4 is connected to the base 15 .

[0075] In actual application, in order to stably fix the first fixing plate 2 and the second fixing plate 3, a plurality of support columns 16 are arranged between the first fixing plate 2 and the second fixing plate 3, and both ends of the support columns 16 are fixedly connected to the first fixing plate 2 and the second fixing plate 3 respectively.

[0076] In actual application, the first fixed plate 2 and the second fixed plate 3 may not be connected to the shell, and both can be connected to the two ends of the rotating shaft 4. Then the upper end of the shell 1 is connected to an end plate and its lower end is connected to the base. A support rod is set between the base and the end plate, and the two ends of the support rod are respectively connected to the two.

[0077] The aforementioned heating element may be a common heating instrument in the art, such as a resistance wire heater. The aforementioned temperature measuring instrument may be a common temperature measuring device in the art, such as a thermocouple.

[0078] In practical application, in order to facilitate temperature control, the stress corrosion evaluation device also includes a data display instrument, which is connected to the temperature measuring instrument. Of course, in practical application, the heating element is connected to an external power supply device to realize power supply.

[0079] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A stress corrosion evaluation device under simulated dynamic conditions, characterized in that: It includes several mounting plates, a shell and a tube body, wherein two ends of the shell are respectively connected with a first fixing plate and a second fixing plate, and the first fixing plate and the second fixing plate are connected via a rotating shaft; Each of the mounting plates is arranged along the axial direction of the housing, and both ends of each of the mounting plates are respectively connected to the first fixing plate and the second fixing plate; a plurality of clamps are fixed on each of the mounting plates; A driving motor is arranged on the first fixing plate or the second fixing plate, and the output end of the driving motor is connected to the rotating shaft; a plurality of heating elements and a temperature measuring instrument are also arranged on the shell; The shell body is provided with a feeding port and a discharging port. The feeding port is detachably provided with a first sealing plug, and the discharging port is detachably provided with a second sealing plug.

2. The stress corrosion evaluation device under simulated dynamic conditions according to claim 1, characterized in that: The first fixing plate is provided with a plurality of first slots, the second fixing plate is provided with a plurality of second slots, one end of the mounting plate is fixed in the first slot and the other end thereof is fixed in the second slot.

3. The stress corrosion evaluation device under simulated dynamic conditions according to claim 2, characterized in that: At least one first clamping slot and one second clamping slot are included on the same vertical line along the axial direction of the rotating shaft, and two ends of the mounting plate are respectively clamped in the first clamping slot and the second clamping slot on the same vertical line.

4. The stress corrosion evaluation device under simulated dynamic conditions according to claim 1, characterized in that: The shell is provided with a viewing window.

5. The stress corrosion evaluation device under simulated dynamic conditions according to claim 4, characterized in that: The viewing window and the shell are detachably connected.

6. The stress corrosion evaluation device under simulated dynamic conditions according to claim 1, characterized in that: Two ends of the rotating shaft penetrate the first fixing plate and the second fixing plate respectively, one end of the rotating shaft is connected to the output end of the motor and the other end thereof is connected to a base.

7. The stress corrosion evaluation device under simulated dynamic conditions according to claim 1, characterized in that: A plurality of support columns are further arranged between the first fixing plate and the second fixing plate, and both ends of each of the support columns are respectively connected to the first fixing plate and the second fixing plate.

8. The stress corrosion evaluation device under simulated dynamic conditions according to claim 4 or 5, characterized in that: The visual window comprises a flange arranged on the shell, and a transparent sheet is arranged on the flange.

9. The stress corrosion evaluation device under simulated dynamic conditions according to claim 8, characterized in that: The transparent sheet is made of tempered glass; preferably, the tempered glass includes organic glass or quartz glass.

10. An evaluation method based on the stress corrosion evaluation device according to any one of claims 1 to 9, characterized in that: The evaluation method includes: Prepare simulated water according to the anion and cation composition of the on-site flowback fluid or directly use the on-site flowback fluid, wherein: the simulated water and the on-site flowback fluid are deoxygenated and carbon dioxide gas is introduced before use; Adjust the loading stress according to the test requirements, install test pieces with different materials on different fixtures, and test pieces with the same stress in parallel; The fixture after stress loading is installed on the mounting plate, and then the mounting plate is fixed to the first fixing plate and the second fixing plate; The stress corrosion evaluation device is tested for leaks, replaced with air, and filled with simulated water or on-site flowback fluid in sequence; Stress corrosion evaluation device for seals, starter motors and heating elements; During the test, observe the changes in the test specimen and simulated liquid. If any abnormality is found, stop the experiment in time and repeat the experiment again.

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