An alternating load under the reservoir well pipe column stress corrosion evaluation device and method

Abstract

The application provides a device and method for evaluating stress corrosion of a storage well pipe string under alternating load. The device for evaluating stress corrosion of the storage well pipe string under alternating load comprises a base, an extension mechanism, a reaction kettle, a temperature sensor, an internal pressure gauge, a central control system, a heating jacket, a top cover, an upper clamp, a lower clamp, an internal pressure relief valve and a gas supply system. The extension mechanism and the reaction kettle are installed on the base. The top of the reaction kettle is provided with an opening. The top cover is installed at the top opening of the reaction kettle. The upper clamp is slidingly installed on the top cover. The bottom of the upper clamp is located in the reaction kettle. The top of the upper clamp is connected with the extension mechanism. The lower clamp is installed at the bottom of the reaction kettle. The heating jacket is sleeved on the outer sidewall of the reaction kettle. The temperature sensor, the internal pressure gauge, the internal pressure relief valve and the gas supply system are respectively connected with the reaction kettle through pipelines. The central control system is connected with the extension mechanism, the temperature sensor, the internal pressure gauge and the gas supply system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reservoir well shaft integrity evaluation, and particularly relates to a device and method for evaluating stress corrosion of a reservoir well pipe string under alternating load. BACKGROUND

[0002] With the development of economy, the demand for energy such as natural gas continues to grow. As the infrastructure for energy peak regulation and reserve, the construction and safe operation of underground reservoirs have become the focus of attention. The reservoir well, especially the natural gas storage and compressed air energy storage injection and production well, is significantly different from the conventional oil and gas well. It has a long service period and bears alternating load caused by injection and production alternation. The stress and pipe wall wear caused by the load obviously promote corrosion, which is a typical alternating stress corrosion condition. Some reservoirs contain carbon dioxide and other mixed gases in addition to natural gas in the gas injection pipeline, so it is necessary to carry out indoor simulation experiment and evaluation research on the corrosion of the reservoir well shaft.

[0003] At present, the evaluation of well shaft corrosion mainly adopts the field logging method. The field evaluation method mainly evaluates the deformation degree and residual wall thickness of the well shaft pipe string by combining electromagnetic flaw detection and multi-arm caliper logging. The field operation process is complex and the cost is high. SUMMARY

[0004] The present application solves the technical problems of the prior art and provides a device and method for evaluating stress corrosion of a reservoir well pipe string under alternating load.

[0005] The technical solution of the present application to solve the above technical problems is as follows: a device for evaluating stress corrosion of a reservoir well pipe string under alternating load, comprising: a base, an extension mechanism, a reaction kettle, a temperature sensor, an internal pressure gauge, a central control system, a heating jacket, a top cover, an upper clamp, a lower clamp, an internal pressure relief valve, and a gas supply system for supplying corrosive gas and non-corrosive gas to the reaction kettle, the extension mechanism and the reaction kettle are installed on the base, the top of the reaction kettle is provided with an opening, the top cover is installed at the top opening of the reaction kettle, the upper clamp is slidingly installed on the top cover, the bottom of the upper clamp is located in the reaction kettle, the top of the upper clamp is connected with the extension mechanism, the lower clamp is installed at the bottom of the reaction kettle, the heating jacket is sleeved on the outer sidewall of the reaction kettle, the temperature sensor, the internal pressure gauge, the internal pressure relief valve and the gas supply system are connected with the reaction kettle through pipelines respectively, and the central control system is connected with the extension mechanism, the temperature sensor, the internal pressure gauge and the gas supply system respectively.

[0006] The beneficial effect of the technical scheme is that: the sample of the wellbore pipe is fixed in the device by the upper and lower clamps, the telescopic mechanism is used to apply periodic tension to the sample to simulate the stress condition of the storage well under alternating load, the corrosive gas is injected, the mass and thickness of the sample before and after corrosion are measured, the corrosion rate of the sample is evaluated, the corrosion condition and behavior of the storage well pipe can be simulated and evaluated, thereby providing a theoretical basis for exploring the corrosion mechanism of the storage well pipe under alternating stress, and providing guidance for the pipe selection, residual strength and residual life evaluation of the pipe string and the wellbore integrity evaluation of the storage well.

[0007] Further, the telescopic mechanism comprises a push rod, a pair of support rods, an upper cross plate and a lower cross plate, the top of the base is provided with a bottom plate, a pair of columns and a top plate, the bottom plate is installed at the top end of the base, a pair of the columns are installed on the bottom plate, the top plate is connected with the top end of a pair of the columns at both ends, the reaction kettle is installed on the bottom plate and located between a pair of the columns, the push rod is installed at the bottom of the base, the lower cross plate is connected with the top of the push rod, the bottom of a pair of the support rods is connected with the lower cross plate, the top of a pair of the support rods penetrates through the bottom plate and is slidingly installed in a pair of the columns in one-to-one correspondence, the both ends of the upper cross plate are connected with the top of a pair of the support rods in one-to-one correspondence, and the top of the upper clamp is connected with the upper cross plate.

[0008] The beneficial effect of the above further technical scheme is that: by measuring the change of the height of the support rod, the strain of the sample under certain stress condition is reflected, the elastic modulus and other mechanical parameters of the sample under the test condition are calculated in combination with the size of the stress, and the change rule of the mechanical properties of the sample under the corrosion condition is evaluated.

[0009] Further, the push rod is an electric push rod, a hydraulic push rod or a pneumatic cylinder.

[0010] The beneficial effect of the above further technical scheme is that: the material selection of the push rod is facilitated, and the cost is reduced.

[0011] Further, the gas supply system comprises a pressure relief valve, an internal pressure valve, a tee, an acid gas source for providing the corrosive gas, an acid gas source valve, a gas source pressure gauge, a mixer, a flow meter, a non-corrosive gas source for providing the non-corrosive gas, and a non-corrosive gas source valve, the internal pressure valve is connected with the reaction kettle through a pipeline, a first end of the tee is connected with the internal pressure valve through a pipeline, a second end of the tee is connected with the pressure relief valve through a pipeline, a third end of the tee is connected with the flow meter through a pipeline, a first end of the mixer is connected with the flow meter through a pipeline, the gas source pressure gauge is connected with the pipeline between the mixer and the flow meter, a second end and a third end of the mixer are respectively connected with the acid gas source valve and the non-corrosive gas source valve through pipelines, the acid gas source is connected with the acid gas source valve through a pipeline, and the non-corrosive gas source is connected with the non-corrosive gas source valve through a pipeline.

[0012] The beneficial effects of the above further technical solutions are that the gas supply system can change the ratio of the corrosive gas and the non-corrosive gas based on actual needs to prepare the corrosive medium for simulation tests. The corrosive medium is a mixed gas of the acid gas and the non-corrosive gas configured in a certain ratio based on actual needs, the flow into the mixer is controlled by adjusting the acid gas source valve and the non-corrosive gas source valve to adjust the gas ratio, and the flow of the gas into the reaction kettle is controlled by the internal pressure valve.

[0013] Further, the power supply and the amplifier are connected with the telescopic mechanism through the amplifier.

[0014] The beneficial effects of the above further technical solutions are that the power supply supplies power to the device to improve automation.

[0015] Further, the reaction kettle is a cylindrical barrel, the top cover is installed at the top opening of the reaction kettle through a threaded connection, and a sealing piston ring is arranged between the upper clamp and the top cover.

[0016] The beneficial effects of the above further technical solutions are that the sealing piston ring is arranged to ensure the air tightness of the whole device, the top cover and the reaction kettle are connected in an air-tight threaded connection, so that the connection between the top cover and the device is more sealed and firm.

[0017] In addition, the application also provides a stress corrosion evaluation method for a reservoir well pipe string under alternating load, based on the stress corrosion evaluation device for the reservoir well pipe string under alternating load in any one of the above aspects, the stress corrosion evaluation method for the reservoir well pipe string under alternating load comprises:

[0018] S1, record the initial weight, initial size and density of the sample;

[0019] S2. Place the sample inside the reactor and fix it in place using the upper and lower clamps.

[0020] S3. Start the heating jacket to heat the internal temperature of the reactor to the preset temperature.

[0021] S4. Turn on the gas supply system and introduce corrosive gas into the reactor through the gas supply system;

[0022] S5. Activate the telescopic mechanism to apply alternating stress to the sample through the telescopic mechanism;

[0023] S6. After the experiment reaches the preset experimental time, take out the sample and measure the final weight and final dimensions of the sample.

[0024] S7. Calculate the corrosion rate of the sample based on the initial weight, initial size, density, final weight, final size, and preset experimental time.

[0025] The beneficial effects of adopting the technical solution of this invention are as follows: By fixing the wellbore tubing sample in the device with two clamps, and applying periodic tension to the sample using the telescopic mechanism to simulate the stress state of the reservoir well under alternating loads, and then injecting corrosive gas, the corrosion rate of the sample can be evaluated by measuring the mass and thickness of the sample before and after corrosion. This allows for the simulation and evaluation of the corrosion status and behavior of the reservoir well tubing, thus providing a theoretical basis for exploring the corrosion mechanism of the reservoir well tubing under alternating stress, and providing guidance for the selection of tubing materials, assessment of remaining strength and remaining life of tubing, and evaluation of wellbore integrity. Furthermore, under the condition that other parameters are constant, the influence of different loads, temperatures, or corrosive media on the corrosion rate and corrosion behavior can be evaluated by individually adjusting the load, temperature, or corrosive medium ratio.

[0026] Furthermore, step S1 is preceded by:

[0027] S11. Select a metal sample;

[0028] S12. Grind, polish and clean the metal sample with anhydrous ethanol.

[0029] Step S6 includes: S61, after the experiment reaches the preset experimental time, open the internal pressure relief valve to release the waste gas inside the reactor and recycle it.

[0030] S62. Take out the sample and clean it with rust remover, rinse it with tap water, and soak it in anhydrous ethanol to remove corrosion products.

[0031] S63. Measure the final weight and final dimensions of the specimen.

[0032] The beneficial effects of adopting the above-mentioned further technical solution are: to treat the sample before and after the experiment respectively, to prevent the residue of impurities on the sample before the experiment and corrosion products on the sample after the experiment, thereby improving the accuracy.

[0033] Further, step S3 includes:

[0034] S31. Open the gas supply system and the internal pressure relief valve, and introduce non-corrosive gas into the reactor through the gas supply system to discharge the air inside the reactor.

[0035] S32. Close the internal pressure relief valve and check the sealing performance of the reactor by observing the pressure change displayed on the internal pressure gauge.

[0036] S33. Start the heating jacket to heat the internal temperature of the reactor to the preset temperature.

[0037] The beneficial effects of adopting the above-mentioned further technical solution are as follows: After the sample is placed into the reaction vessel of the device, it is fixed by the upper and lower clamps and the top cover is tightened. First, non-corrosive gas is introduced to expel the air inside the reaction vessel. After the venting is completed, the internal pressure relief valve is closed, and the pressure change shown by the internal pressure gauge is observed to check the sealing performance of the device. This ensures that there is no other gas in the device and that the device is well sealed, so as not to affect subsequent tests.

[0038] Further, in step S7, based on the initial weight, initial size, density, final weight, final size, and preset experimental time, the corrosion rate of the sample is calculated using the following formula:

[0039] Among them, C r ΔW is the corrosion rate of the sample, in mm / a; ΔW is the weight loss of the sample before and after corrosion, in g; A is the surface area of ​​the sample, in mm². 2 ρ is the density of the sample, in g / cm³. 3 t represents the test time, measured in days (d).

[0040] The beneficial effects of adopting the above-mentioned further technical solutions are: the corrosion rate is calculated by formula, which improves the accuracy and reliability of experimental data.

[0041] The advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the reservoir well tubing stress corrosion evaluation device under alternating load provided in an embodiment of the present invention.

[0043] Figure 2This is a schematic flowchart illustrating the method for evaluating the stress corrosion of storage well tubing under alternating loads, as provided in an embodiment of the present invention.

[0044] Reference numerals: 1. Push rod; 2. Base; 3. Servo motor; 4. Power supply; 5. Support rod; 6. Reactor; 7. Temperature sensor; 8. Internal pressure gauge; 9. Central control system; 10. Heating jacket; 11. Top cover; 12. Sealing piston ring; 13. Upper clamp; 14. Top plate; 15. Upper horizontal plate; 16. Pressure relief valve; 17. Internal pressure valve; 18. T-junction; 19. Lower clamp; 20. Internal pressure relief valve; 21. Base plate; 22. Lower horizontal plate; 23. Acid gas source; 24. Acid gas source valve; 25. Gas source pressure gauge; 26. Mixer; 27. Flow meter; 28. Non-corrosive gas source valve; 29. ​​Non-corrosive gas source; 30. Telescopic mechanism; 31. Gas supply system; 32. Column. Detailed Implementation

[0045] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0046] like Figure 1 As shown, this embodiment of the invention provides a stress corrosion evaluation device for a storage well casing under alternating loads, comprising: a base 2, a telescopic mechanism 30, a reaction vessel 6, a temperature sensor 7, an internal pressure gauge 8, a central control system 9, a heating jacket 10, a top cover 11, an upper clamp 13, a lower clamp 19, an internal pressure relief valve 20, and a gas supply system 31 for introducing corrosive and non-corrosive gases into the reaction vessel 6. The telescopic mechanism 30 and the reaction vessel 6 are mounted on the base 2. The top of the reaction vessel 6 has an opening, and the top cover 11 is installed at the top opening of the reaction vessel 6. The upper clamp 10... 3. The upper clamp 13 is slidably mounted on the top cover 11. The bottom of the upper clamp 13 is located in the reactor 6. The top of the upper clamp 13 is connected to the telescopic mechanism 30. The lower clamp 19 is mounted on the bottom of the reactor 6. The heating sleeve 10 is fitted on the outer wall of the reactor 6. The temperature sensor 7, the internal pressure gauge 8, the internal pressure relief valve 20, and the gas supply system 31 are respectively connected to the reactor 6 through pipelines. The central control system 9 is respectively connected to the telescopic mechanism 30, the temperature sensor 7, the internal pressure gauge 8, and the gas supply system 31.

[0047] The beneficial effects of adopting the technical solution of this invention are as follows: By fixing the wellbore tubing sample in the device with two clamps, and applying periodic tension to the sample using the telescopic mechanism to simulate the stress state of the reservoir well under alternating loads, and then injecting corrosive gas, the corrosion rate of the sample can be evaluated by measuring the mass and thickness of the sample before and after corrosion. This allows for the simulation and evaluation of the corrosion status and behavior of the reservoir well tubing, thus providing a theoretical basis for exploring the corrosion mechanism of the reservoir well tubing under alternating stress, and providing guidance for the selection of tubing materials, assessment of remaining strength and remaining life of tubing, and evaluation of wellbore integrity. Furthermore, under the condition that other parameters are constant, the influence of different loads, temperatures, or corrosive media on the corrosion rate and corrosion behavior can be evaluated by individually adjusting the load, temperature, or corrosive medium ratio.

[0048] The ratio of acidic carbon dioxide (corrosive gas) to non-corrosive gas can be changed based on actual needs to determine the corrosive medium in the simulation test.

[0049] like Figure 1 As shown, the telescopic mechanism 30 further includes: a push rod 1, a pair of support rods 5, an upper horizontal plate 15, and a lower horizontal plate 22. The top of the base 2 is provided with a bottom plate 21, a pair of columns 32, and a top plate 14. The bottom plate 21 is installed at the top of the base 2, and the pair of columns 32 are installed on the bottom plate 21. The two ends of the top plate 14 are connected to the tops of the pair of columns 32 respectively. The reactor 6 is installed on the bottom plate 21 and is located between the pair of columns 32. The push rod 1 is installed at the bottom of the base 2. The lower horizontal plate 22 is connected to the top of the push rod 1. The bottoms of the pair of support rods 5 are connected to the lower horizontal plate 22. The tops of the pair of support rods 5 penetrate the bottom plate 21 and are slidably installed in the pair of columns 32 respectively. The two ends of the upper horizontal plate 15 are connected to the tops of the pair of support rods 5 respectively. The top of the upper clamp 13 is connected to the upper horizontal plate 15.

[0050] The beneficial effects of adopting the above-mentioned further technical solution are: by measuring the change in the height of the support rod, the strain of the sample under certain stress conditions can be reflected. Combined with the magnitude of the stress, the mechanical parameters such as the elastic modulus of the sample under the test conditions can be calculated, and then the change law of the mechanical properties of the sample under corrosion conditions can be evaluated.

[0051] like Figure 1 As shown, the push rod 1 is further described as an electric push rod, a hydraulic push rod, or a cylinder.

[0052] The advantages of adopting the above-mentioned further technical solutions are: it facilitates the selection of materials for the push rod and reduces costs.

[0053] In this embodiment of the invention, a hydraulic push rod is used, which is connected to a servo motor 3, and the servo motor 3 is connected to a power supply 4.

[0054] By fixing the wellbore sample in the device with two clamps, a servo motor is used to drive a hydraulic push rod to apply periodic tension to the sample to simulate the stress condition of the reservoir well under alternating loads.

[0055] like Figure 1 As shown, the gas supply system 31 further includes: a pressure relief valve 16, an internal pressure valve 17, a three-way valve 18, an acidic gas source 23 for providing corrosive gases, an acidic gas source valve 24, a gas source pressure gauge 25, a mixer 26, a flow meter 27, a non-corrosive gas source 29 for providing non-corrosive gases, and a non-corrosive gas source valve 28. The internal pressure valve 17 is connected to the reaction vessel 6 via a pipeline. The first end of the three-way valve 18 is connected to the internal pressure valve 17 via a pipeline, and the second end of the three-way valve 18 is connected to the pressure relief valve 16 via a pipeline. The third end of the tee 18 is connected to the flow meter 27 via a pipeline. The first end of the mixer 26 is connected to the flow meter 27 via a pipeline. The gas source pressure gauge 25 is connected to the pipeline between the mixer 26 and the flow meter 27. The second and third ends of the mixer 26 are connected to the acid gas source valve 24 and the non-corrosive gas source valve 28 via pipelines. The acid gas source 23 is connected to the acid gas source valve 24 via a pipeline. The non-corrosive gas source 29 is connected to the non-corrosive gas source valve 28 via a pipeline.

[0056] The beneficial effect of adopting the above-mentioned further technical solution is that the gas supply system can change the ratio of corrosive gas to non-corrosive gas according to actual needs to prepare the corrosive medium for the simulated test. The corrosive medium is a mixture of acidic gas and non-corrosive gas configured in a certain proportion based on actual needs. The gas ratio is adjusted by regulating the flow rate into the mixer through the acidic gas source valve and the non-corrosive gas source valve, and the flow rate of gas into the reactor is controlled by the internal pressure valve.

[0057] The flow meter can be a high-pressure flow meter.

[0058] like Figure 1 As shown, it further includes: a power supply 4 and an amplifier, wherein the power supply 4 is connected to the telescopic mechanism 30 through the amplifier.

[0059] The beneficial effects of adopting the above-mentioned further technical solutions are: the power supply provides power to the device, improving automation.

[0060] Among them, power supply 4 can be a DC power supply.

[0061] like Figure 1As shown, the reactor 6 is a cylindrical body, the top cover 11 is threaded onto the top opening of the reactor 6, and a sealing piston ring 12 is provided between the upper clamp 13 and the top cover 11.

[0062] The beneficial effects of adopting the above-mentioned further technical solution are: the setting of the sealing piston ring is used to ensure the overall airtightness of the device, and the top cover and the reactor are connected by an airtight thread, which makes the connection between the top cover and the device more sealed and firm.

[0063] The top cover 11 has a round hole in the center that matches the size of the upper clamp 13. There is a sealing piston ring 12 between the top cover 11 and the clamp (upper clamp) to ensure the overall airtightness of the device. The top cover 11 and the reactor 6 are connected by an airtight thread, which makes the connection between the top cover 11 and the device more sealed and firm.

[0064] The reactor 6 of the stress corrosion evaluation device for well tubing under alternating load is a cylindrical container with an open top and a heating jacket 10 covering the outer wall. It is installed on the base plate 21. The upper part of the reactor is connected to the top cover 11 by a sealing thread. A lower clamp 19 is installed in the center of the bottom surface inside the reactor. There is a pressure relief port at the bottom of the reactor wall connected to the internal pressure relief valve 20. The upper part of the reactor wall is connected to the gas source through a pipeline via the internal pressure valve 17. The reactor 6 is connected to the internal pressure gauge 8 to detect the internal pressure of the reactor. Push rod 1 is mounted on base 2 and powered by power supply 4 connected to amplifier. The upper part of push rod 1 is connected to lower horizontal plate 22. Above lower horizontal plate 22 are two support rods 5, and outside the two support rods 5 are columns 32. Above columns 32 is the top plate 14 of the device. Support rods 5 pass through base plate 21 and connect to upper horizontal plate 15. The upper horizontal plate 15 has an upper clamp 13 in the center, which passes through a circular hole in the center of top cover 11 and is located inside reactor 6. The upper clamp 13 and top cover 11 are sealed by a sealing piston ring 12. The pipeline at the top of reactor 6 is connected to internal pressure valve 17, and then via tee 18 to pressure relief valve 16 and flow meter 27. Flow meter 27 is connected to gas source pressure gauge 25 and mixer 26. Mixer 26 is connected to acid gas source 23 and non-corrosive gas source 29 via acid gas source valve 24 and non-corrosive gas source valve 28, respectively.

[0065] like Figure 2 As shown, in addition, the present invention also provides a method for evaluating the stress corrosion of a reservoir well string under alternating loads. Based on the stress corrosion evaluation device for a reservoir well string under alternating loads described in any one of the above claims, the method for evaluating the stress corrosion of a reservoir well string under alternating loads includes:

[0066] S1. Record the initial weight, initial dimensions, and density of the sample;

[0067] S2. Place the sample inside the reactor and fix it in place using the upper and lower clamps.

[0068] S3. Start the heating jacket to heat the internal temperature of the reactor to the preset temperature.

[0069] S4. Turn on the gas supply system and introduce corrosive gas into the reactor through the gas supply system;

[0070] S5. Activate the telescopic mechanism to apply alternating stress to the sample through the telescopic mechanism;

[0071] S6. After the experiment reaches the preset experimental time, take out the sample and measure the final weight and final dimensions of the sample.

[0072] S7. Calculate the corrosion rate of the sample based on the initial weight, initial size, density, final weight, final size, and preset experimental time.

[0073] The beneficial effects of adopting the technical solution of this invention are as follows: By fixing the wellbore tubing sample in the device with two clamps, and applying periodic tension to the sample using the telescopic mechanism to simulate the stress state of the reservoir well under alternating loads, and then injecting corrosive gas, the corrosion rate of the sample can be evaluated by measuring the mass and thickness of the sample before and after corrosion. This allows for the simulation and evaluation of the corrosion status and behavior of the reservoir well tubing, thus providing a theoretical basis for exploring the corrosion mechanism of the reservoir well tubing under alternating stress, and providing guidance for the selection of tubing materials, assessment of remaining strength and remaining life of tubing, and evaluation of wellbore integrity. Furthermore, under the condition that other parameters are constant, the influence of different loads, temperatures, or corrosive media on the corrosion rate and corrosion behavior can be evaluated by individually adjusting the load, temperature, or corrosive medium ratio.

[0074] The stress corrosion evaluation device for well tubing under alternating loads can simulate and evaluate the corrosion status and behavior of well tubing. It is closely integrated with actual field engineering practices and has strong practicality. Specifically, it includes:

[0075] (1) Apply fixed loads at different levels in a specific ratio of corrosive media, measure the corrosion rate, and explore the effects of different stress levels on corrosion rate and corrosion behavior.

[0076] (2) In a specific ratio of corrosive media, different cycles of alternating axial loads are applied, the corrosion rate is measured, and the effects of the cycles and amplitude of alternating loads on the corrosion rate and corrosion behavior are explored.

[0077] (3) Under specific axial load conditions, adjust the ratio and temperature of the corrosive medium, measure the corrosion rate, and explore the corrosion rate and corrosion behavior of the tubing under the gas storage gas composition and downhole temperature and pressure conditions.

[0078] The various methods can be freely combined and used.

[0079] Furthermore, step S1 is preceded by:

[0080] S11. Select a metal sample;

[0081] S12. Grind, polish and clean the metal sample with anhydrous ethanol.

[0082] Step S6 includes: S61, after the experiment reaches the preset experimental time, open the internal pressure relief valve to release the waste gas inside the reactor and recycle it.

[0083] S62. Take out the sample and clean it with rust remover, rinse it with tap water, and soak it in anhydrous ethanol to remove corrosion products.

[0084] S63. Measure the final weight and final dimensions of the specimen.

[0085] The beneficial effects of adopting the above-mentioned further technical solution are: to treat the sample before and after the experiment respectively, to prevent the residue of impurities on the sample before the experiment and corrosion products on the sample after the experiment, thereby improving the accuracy.

[0086] Further, step S3 includes:

[0087] S31. Open the gas supply system and the internal pressure relief valve, and introduce non-corrosive gas into the reactor through the gas supply system to discharge the air inside the reactor.

[0088] S32. Close the internal pressure relief valve and check the sealing performance of the reactor by observing the pressure change displayed on the internal pressure gauge.

[0089] S33. Start the heating jacket to heat the internal temperature of the reactor to the preset temperature.

[0090] The beneficial effects of adopting the above-mentioned further technical solution are as follows: After the sample is placed into the reaction vessel of the device, it is fixed by the upper and lower clamps and the top cover is tightened. First, non-corrosive gas is introduced to expel the air inside the reaction vessel. After the venting is completed, the internal pressure relief valve is closed, and the pressure change shown by the internal pressure gauge is observed to check the sealing performance of the device. This ensures that there is no other gas in the device and that the device is well sealed, so as not to affect subsequent tests.

[0091] Further, in step S7, based on the initial weight, initial size, density, final weight, final size, and preset experimental time, the corrosion rate of the sample is calculated using the following formula:

[0092] Among them, C r ΔW is the corrosion rate of the sample, in mm / a; ΔW is the weight loss of the sample before and after corrosion, in g; A is the surface area of ​​the sample, in mm². 2ρ is the density of the sample, in g / cm³. 3 t represents the test time, in days (d).

[0093] The beneficial effects of adopting the above-mentioned further technical solutions are: the corrosion rate is calculated by formula, which improves the accuracy and reliability of experimental data.

[0094] Specifically, the sample is placed in the reactor 6 and fixed with clamps (upper clamp and lower clamp). After the top cover 11 is installed, the heating jacket 10 is started to heat until the temperature inside the reactor 6 reaches the test requirements. Then, the valve (internal pressure valve) is opened to introduce corrosive medium gas, and the push rod 1 is started to apply periodic alternating stress to the sample until the test is completed.

[0095] After the metal sample (sample) is placed into the reactor 6 of the device, it is fixed by the upper and lower clamps and the top cover 11 is tightened. First, a non-corrosive gas is introduced to expel the air inside the reactor 6. After the venting is completed, the internal pressure relief valve 20 is closed, and the pressure change shown on the internal pressure gauge 8 is observed to check the sealing of the device. This ensures that there is no other gas in the device and that the device is well sealed, so as not to affect subsequent tests.

[0096] After the heating jacket 10 is activated to bring the reactor 6 to the preset test temperature, carbon dioxide and nitrogen are introduced into the reactor 6 in a predetermined partial pressure ratio. At the same time, the push rod 1 is controlled by the central control system 9 to drive the upper clamp 13 to apply a certain number of cycles of alternating tensile load to the metal sample (test sample) to simulate the stress change conditions of the wellbore steel in the daily injection and production process of the actual reservoir well.

[0097] After the test reaches the set test duration, first open the internal pressure relief valve 20 to discharge the waste gas inside the reactor 6 and recycle it. Then take out the metal sample (sample), clean it with rust remover, rinse it with tap water, soak it in anhydrous ethanol to remove corrosion products, and then dry it. Finally, weigh the metal sample and measure its dimensional changes.

[0098] The corrosion rate calculated by the experiment can evaluate the corrosion resistance of the pipe material and provide data for the assessment of the remaining strength and remaining life of the wellbore tubing in the reservoir well, ultimately guiding the selection of materials and the evaluation of the integrity of the wellbore tubing in the reservoir well.

[0099] The test specimens are metal samples of well casing steel of different grades selected for the test based on actual needs. After the steel is cut from the casing, it is ground, polished, cleaned and dried with anhydrous ethanol to make a 50mm×25mm×2mm specimen and weighed. After the test, the degree of corrosion is determined by the mass loss and dimensional change of the specimen.

[0100] The corrosive medium is a mixture of acidic and non-corrosive gases configured in a certain proportion based on actual needs. The gas ratio is adjusted by regulating the flow rate into the gas mixer by adjusting two gas source valves (acidic gas source valve and non-corrosive gas source valve). The flow rate of gas into the reactor 6 is controlled by the internal pressure valve 17.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for evaluating stress corrosion of well tubing under alternating loads in a storage tank, characterized in that, include: The reactor includes a base, a telescopic mechanism, a reaction vessel, a temperature sensor, an internal pressure gauge, a central control system, a heating jacket, a top cover, an upper clamp, a lower clamp, an internal pressure relief valve, and a gas supply system for introducing corrosive and non-corrosive gases into the reaction vessel. The telescopic mechanism and the reaction vessel are mounted on the base. The top of the reaction vessel has an opening, and the top cover is installed at the top opening. The upper clamp is slidably mounted on the top cover, with its bottom located inside the reaction vessel. The top of the upper clamp is connected to the telescopic mechanism, and the lower clamp is installed at the bottom of the reaction vessel. The heating jacket is fitted over the reaction vessel. On the outer wall of the reactor, the temperature sensor, the internal pressure gauge, the internal pressure relief valve, and the gas supply system are respectively connected to the reactor via pipelines. The central control system is connected to the telescopic mechanism, the temperature sensor, the internal pressure gauge, and the gas supply system. The telescopic mechanism includes: a push rod, a pair of support rods, an upper horizontal plate, and a lower horizontal plate. The top of the base is provided with a bottom plate, a pair of columns, and a top plate. The bottom plate is installed at the top of the base, the pair of columns are installed on the bottom plate, and the two ends of the top plate are connected to the tops of the pair of columns. The reactor is installed on the bottom plate, and the reactor is located on the pair of columns. Between the columns, the push rod is installed at the bottom of the base, the lower horizontal plate is connected to the top of the push rod, the bottom of a pair of support rods is connected to the lower horizontal plate, the top of a pair of support rods penetrates the base plate and is slidably installed in a pair of columns, the two ends of the upper horizontal plate are connected to the top of a pair of support rods, and the top of the upper clamp is connected to the upper horizontal plate; the gas supply system includes: a pressure relief valve, an internal pressure valve, a three-way valve, an acidic gas source for providing corrosive gases, an acidic gas source valve, a gas source pressure gauge, a mixer, a flow meter, a non-corrosive gas source for providing non-corrosive gases, and a non-corrosive gas source valve. An internal pressure valve is connected to the reactor via a pipeline. The first end of the tee is connected to the internal pressure valve via a pipeline. The second end of the tee is connected to the pressure relief valve via a pipeline. The third end of the tee is connected to the flow meter via a pipeline. The first end of the mixer is connected to the flow meter via a pipeline. The gas source pressure gauge is connected to the pipeline between the mixer and the flow meter. The second and third ends of the mixer are connected to the acid gas source valve and the non-corrosive gas source valve respectively via pipelines. The acid gas source is connected to the acid gas source valve via a pipeline, and the non-corrosive gas source is connected to the non-corrosive gas source valve via a pipeline.

2. The device for evaluating stress corrosion of well tubing under alternating loads according to claim 1, characterized in that, The push rod is an electric push rod, a hydraulic push rod, or a cylinder.

3. The device for evaluating stress corrosion of storage well tubing under alternating loads according to claim 1, characterized in that, Also includes: A power supply and an amplifier, wherein the power supply is connected to the telescopic mechanism via the amplifier.

4. The device for evaluating stress corrosion of storage well tubing under alternating loads according to claim 1, characterized in that, The reactor is a cylindrical body, and the top cover is threaded onto the top opening of the reactor. A sealing piston ring is provided between the upper clamp and the top cover.

5. A method for evaluating stress corrosion of well tubing under alternating loads in a storage tank, characterized in that, Based on the stress corrosion evaluation device for reservoir well tubing under alternating load according to any one of claims 1 to 4, the stress corrosion evaluation method for reservoir well tubing under alternating load includes: S1. Record the initial weight, initial dimensions, and density of the sample; S2. Place the sample inside the reactor and fix it in place using the upper and lower clamps. S3. Start the heating jacket to heat the internal temperature of the reactor to the preset temperature. S4. Turn on the gas supply system and introduce corrosive gas into the reactor through the gas supply system; S5. Activate the telescopic mechanism to apply alternating stress to the sample through the telescopic mechanism; S6. After the experiment reaches the preset experimental time, take out the sample and measure the final weight and final dimensions of the sample. S7. Calculate the corrosion rate of the sample based on the initial weight, initial size, density, final weight, final size, and preset experimental time. Before step S1, the following are included: S11. Select a metal sample; S12. Grind, polish and clean the metal sample with anhydrous ethanol. Step S6 includes: S61, after the experiment reaches the preset experimental time, open the internal pressure relief valve to release the waste gas inside the reactor and recycle it. S62. Take out the sample and clean it with rust remover, rinse it with tap water, and soak it in anhydrous ethanol to remove corrosion products. S63. Measure the final weight and final dimensions of the specimen; Step S3 includes: S31. Open the gas supply system and the internal pressure relief valve, and introduce non-corrosive gas into the reactor through the gas supply system to discharge the air inside the reactor. S32. Close the internal pressure relief valve and check the sealing performance of the reactor by observing the pressure change displayed on the internal pressure gauge. S33. Start the heating jacket to heat the internal temperature of the reactor to the preset temperature.

6. The method for evaluating stress corrosion of storage well tubing under alternating loads according to claim 5, characterized in that, In step S7, based on the initial weight, initial size, density, final weight, final size, and preset experimental time, the corrosion rate of the sample is calculated using the following formula: , where C r ΔW is the corrosion rate of the sample, in mm / a; ΔW is the weight loss of the sample before and after corrosion, in g; A is the surface area of ​​the sample, in mm². 2 ρ is the density of the sample, in g / cm³. 3 t represents the test time, measured in days (d).

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