A high-temperature and high-pressure gas well corrosion prevention process design method

Abstract

The present disclosure relates to a high-temperature and high-pressure gas well corrosion prevention process design method, which firstly uses full-size and full-flow inhibitor injection experiment to obtain accurate indoor experiment parameters, provides accurate inhibitor type and key parameters such as chemical agent injection valve for field application, effectively solves the problems of large difference between previous indoor evaluation equipment and actual working condition, inaccurate evaluation result, and insufficient consideration of downhole tool factors for injection of corrosion inhibitor, significantly improves the reliability and practicability of indoor evaluation result, and determines the key basis for field test; then, the output fluid monitoring and corrosion coupon monitoring mechanism are set up on the spot, the purpose of accurately mastering the implementation process of the corrosion prevention process under the condition of not closing the well is realized; the present disclosure realizes the dynamic and fine regulation and control of corrosion prevention measures such as inhibitor injection through the effective combination of indoor experiment and field control, and provides important process support for the safe and economic exploitation of high-temperature, high-pressure and high-sulfur wells.

Description

Technical Field

[0001] This disclosure relates to the field of gas well extraction technology in gas field development, specifically to a design method for corrosion prevention process of high-temperature and high-pressure gas wells. Background Technology

[0002] The statements in this section provide only background information in connection with this disclosure and do not constitute prior art.

[0003] Natural gas, characterized by its green and low-carbon nature, is playing an increasingly important role in my country's energy system. To further develop natural gas resources, recent years have seen a shift in development focus towards complex reservoir types such as deep, high-temperature, high-pressure, and high-H2S-content formations. Ensuring the safe extraction of these "three-high" gas wells under harsh downhole conditions is crucial for gas field development. Ensuring the safety of downhole tubing corrosion is a core aspect. In implementing corrosion protection technologies for these "three-high" gas wells, the trade-off between economic efficiency and safety is extremely prominent, especially for the large number of medium- and low-yield gas wells, where nickel-based alloys are used. While high-grade anti-corrosion materials can ensure long-term corrosion safety, the cost is extremely high, reaching up to 10 times that of high sulfur-resistant carbon steel per ton, making widespread application difficult. While direct application of high sulfur-resistant materials such as 110SS is more economical, it requires thorough corrosion risk assessment and suitability evaluation of measures such as corrosion inhibitors. Furthermore, due to the dynamic changes in gas well production parameters, it also relies on precise adjustments to the process regime for corrosion inhibitors during on-site implementation. Otherwise, it can easily lead to problems such as pipe corrosion perforation and breakage after production, seriously affecting the safe and efficient exploitation of the gas field.

[0004] For the design of anti-corrosion processes for "high-temperature, high-volume, and high-efficiency" gas wells, current methods mainly involve adjusting the process after indoor simulation experiments and on-site detection of obvious safety issues. However, both existing evaluation methods and processes have shortcomings. A device and method for evaluating vapor-phase corrosion inhibitors (CN105319142A) can evaluate vapor-phase corrosion inhibitors, but it cannot simulate the chemical injection valve in the tubing or corrosion under high-temperature and high-pressure environments. A device and method for rapidly and accurately evaluating corrosion inhibitor efficiency and analyzing corrosion rates (CN114755167A) can analyze and evaluate the corrosion of multiple steel grades in a single operation under complex corrosive media environments, rapidly analyzing corrosion rates and effectively replacing the traditional mass loss method. However, it cannot simulate the process of the corrosion inhibitor entering the tubing from the annulus. A device and method for evaluating corrosion inhibitor performance (CN111141664B) can simulate the flow environment of a pipeline system, thereby simulating the on-site corrosion environment and screening for the optimal corrosion inhibitor and its concentration that meets the operating conditions. However, it cannot simulate the corrosion inhibitor under high-temperature and high-pressure conditions.

[0005] In summary, current technologies are unable to evaluate the performance of corrosion inhibitors in real high-temperature and high-pressure environments, and cannot be applied in field experiments. As a result, there is a lack of corrosion protection optimization design methods that range from full-process indoor experimental evaluation to refined on-site management, leading to varying degrees of on-site corrosion problems in some gas wells and adversely affecting gas well production management.

[0006] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art. Summary of the Invention

[0007] In view of this, this disclosure provides a corrosion protection process design method for high-temperature and high-pressure gas wells, which solves the problem that the current technology lacks a corrosion protection optimization design method that covers the entire process from indoor experimental evaluation to refined on-site management, resulting in varying degrees of on-site corrosion in some gas wells.

[0008] To achieve the above-mentioned objective, the high-temperature and high-pressure gas well corrosion prevention process design method includes: Based on the target gas well's wellbore environmental parameters, fluid performance parameters, completion string structural parameters, and production parameters, an indoor corrosion inhibitor injection process experiment was conducted to compare the corrosion effects under different chemical agent injection valves, different types of corrosion inhibitors, different injection cycles, and different injection amounts of corrosion inhibitors, as well as the working performance of the chemical agent injection valves, and to complete the preliminary design of the corrosion prevention process. Based on the preliminary design results of the corrosion prevention process, after the target gas well has been put into production and is stable, the first injection of corrosion inhibitor will be carried out, and the ion content will be continuously monitored. Before the second injection of corrosion inhibitor, the corrosion degree will be monitored using the wellhead clip. This cycle will be repeated. After the corrosion degree monitoring reaches the set number of times, the corrosion inhibitor injection cycle and / or the single injection amount and / or the corrosion inhibitor type will be changed and adjusted according to the ion content and the corrosion degree.

[0009] In this disclosure and possible embodiments, the method for monitoring corrosion using wellhead clips includes: A continuous monitoring device for wellhead corrosion parameters is connected to the gas production tree device at the target gas wellhead. A corrosion-coated plate valve is connected between the seventh and eighth valves of the wellhead gas production tree device, and the corrosion-coated plate is installed inside the corrosion-coated plate valve. A bypass branch is installed on the pipeline above the seventh valve and below the eighth valve. The corrosion-coated plate can be replaced without shutting down the well by adjusting the gas production tree flow through the bypass branch. The continuous wellhead corrosion parameter monitoring equipment is used to monitor the corrosion degree of the corrosion-resistant adhesive strips.

[0010] In this disclosure and possible embodiments, a corrosion inhibitor injection device is connected to the annulus production casing valve of the target gas well, and the corrosion inhibitor is injected through the corrosion inhibitor injection device.

[0011] In this disclosure and possible embodiments, the target gas well's wellbore environmental parameters, fluid performance parameters, completion string structural parameters, and production parameters include the target gas well's wellbore temperature, wellbore pressure, gas well production rate, produced gas H2S and CO2 content, and downhole tool type and parameters.

[0012] In this disclosure and possible embodiments, the method for continuous monitoring of ion content includes: A component monitoring instrument is installed on the ground to monitor the iron ion content after corrosion of the completion tubing and the ion content after the coating of coated tubing falls off in real time.

[0013] In this disclosure and possible embodiments, the experimental apparatus used for the corrosion inhibitor application process experiment includes: The downhole tubing module adopts the structural parameters of the completion tubing.

[0014] In this disclosure and possible embodiments, the experimental apparatus further includes: Wellbore module, corrosion inhibitor injection module, and corrosive gas supply module; The wellbore module is used to simulate the downhole casing and formation, and works with the downhole tubing module to form an annular space between the oil casing and the casing. The outer wall of the downhole casing is equipped with an electric heating sleeve, a corrosion inhibitor sampling port and an observation window. The corrosion inhibitor injection module is used to inject liquid corrosion inhibitor at a constant pressure or a constant flow rate; The corrosive gas supply module is used to inject corrosive gas into the wellbore and downhole tubing to simulate gas well production conditions.

[0015] In this disclosure and possible embodiments, the method for conducting the corrosion inhibitor application process experiment includes the following steps: (1) According to the completion string parameters, run in tubing with the same outer diameter and wall thickness, and the tubing includes several short sections for monitoring corrosion rate; (2) A corrosion monitoring device is suspended at the wellhead, and the performance of the corrosion inhibitor and the injection process are evaluated based on the corrosion rate data of the device. (3) Open the N2 gas cylinder to purge the experimental pipeline; (4) Based on the actual wellbore temperature, use an electric heating jacket to heat the wellbore to ensure a constant wellbore temperature; (5) Configure the simulated gas according to the actual gas composition; close the first valve, and mix the above different gases into the gas mixing tank according to the calculated gas volume using H2S, CO2, N2 and CH4 cylinders, and increase the pressure of the pump to make the system pressure reach the target experimental pressure. Open the second valve, the third valve, and the motor to continuously circulate the high-pressure gas in the pipeline using the stirring paddle; The experimental gas flows in from the bottom of the wellbore, passes through the completion tubing, and then circulates continuously through the circulation pipeline to simulate the continuous gas production process in an actual wellbore. (6) Turn on the water tank and corrosion inhibitor injection pump, and use the corrosion inhibitor injection pump to inject corrosion inhibitor from the annulus between the oil casing and the casing. The injection system includes different injection rates, different types of corrosion inhibitors, and different concentrations of corrosion inhibitors. The injection process is evaluated by recording the injection pressure and by using the visual window to evaluate the injection performance of the chemical agent injection valve. (7) After the experiment, turn off the CH4 gas cylinder, CO2 gas cylinder, H2S gas cylinder, water tank and injection pump, open the hydrogen sulfide purification box and high acid resistant storage tank, and open the N2 gas cylinder for gas washing. (8) After the experiment, first remove the corrosion clips, then remove the completion tubing string, and remove the tubing short section. Use measuring equipment to measure the remaining weight, wall thickness, and dimensions of the corrosion clips and tubing short section, calculate the corrosion rate, observe and record the surface corrosion morphology, and analyze the corrosion type and degree under the experimental conditions.

[0016] In this disclosure and possible embodiments, the set number of times for monitoring the degree of corrosion is 3.

[0017] In this disclosure and possible embodiments, the method for adjusting the corrosion inhibitor application cycle and / or the single application amount and / or the type of corrosion inhibitor based on the ion content and the degree of corrosion includes: If the ion content and the degree of corrosion increase, the corrosion inhibitor application cycle should be increased and / or the single application amount of corrosion inhibitor should be increased and / or other types of corrosion inhibitor should be replaced; if the ion content and the degree of corrosion decrease, the corrosion inhibitor application cycle should be extended and / or the single application amount of corrosion inhibitor should be reduced.

[0018] The beneficial effects of this invention are as follows: The present invention realizes the effective combination of indoor experiments and on-site control. Firstly, it innovatively proposes to use the accurate indoor experimental parameters obtained from the full-scale and full-process corrosion inhibitor injection process experimental device to provide the accurate corrosion inhibitor type and key parameters of the chemical agent injection valve for on-site application, effectively solving the problems that the previous indoor evaluation equipment has a large difference from the actual working conditions and the evaluation results are inaccurate, and insufficient consideration of the downhole tool factors for injecting corrosion inhibitors, significantly improving the credibility and practicality of the indoor evaluation results, and determining the key basis for on-site tests. Secondly, it innovatively proposes a on-site produced fluid monitoring and corrosion coupon monitoring mechanism supporting the experimental device, cleverly realizing the accurate grasp of the real effect of the anti-corrosion process implementation under the conditions of not shutting down the well and not affecting production, enabling the dynamic and refined control of anti-corrosion measures such as corrosion inhibitor injection in a timely manner, truly realizing safe, economic and efficient anti-corrosion, and providing an important technological support for the safe and economic exploitation of high-temperature, high-pressure and high-sulfur wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings herein are incorporated into the specification and form a part of this specification. These drawings illustrate embodiments consistent with the present disclosure and, together with the specification, are used to explain the technical solutions of the present disclosure.

[0020] Figure 1 Schematic diagram of the full-scale corrosion inhibitor indoor evaluation experimental device in an embodiment of the present invention; Figure 2 Schematic diagram of the gas production tree device for continuous corrosion monitoring without shutting down the well in an embodiment of the present invention; In the figure: 1 - hydrogen sulfide purification box, 2 - motor, 3 - high-acid-resistant gas storage tank, 4 - first valve, 5 - intermediate container, 6 - stirring paddle, 7 - electric heating jacket, 8 - booster pump, 9 - corrosion coupon, 10 - injection pump, 11 - water tank, 12 - temperature and pressure monitoring device, 13 - H2S gas cylinder, 14 - CO2 gas cylinder, 15 - N2 gas cylinder, 16 - CH4 gas cylinder, 17 - experimental pipe string, 18 - chemical agent injection valve, 19 - second valve, 20 - third valve, 21 - gas mixing tank, 22 - fourth valve, 23 - fifth valve, 24 - sixth valve, 25 - seventh valve, 26 - eighth valve, 27 - ion detection device, 28 - wellhead corrosion coupon valve and supporting coupon, 29 - pressure gauge, 30 - flange. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following describes the present disclosure based on embodiments, but it should be noted that the present disclosure is not limited to these embodiments. In the following detailed description of the present disclosure, some specific details are described in detail. However, those skilled in the art can also fully understand the present disclosure for the parts not described in detail.

[0022] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0023] To address the problems in the background technology, the high-temperature and high-pressure gas well corrosion prevention process design method provided in this disclosure includes the following steps: 1. Collect statistics on the target gas wellbore environmental parameters, fluid performance parameters, completion string structural parameters, and production parameters: In this embodiment of the disclosure, the parameters that need to be statistically analyzed include the target gas wellbore temperature, wellbore pressure, gas well production, content of corrosive gases such as H2S and CO2 in the produced gas, the oil casing string structure used, and the type and parameters of downhole tools, so as to provide basic data for carrying out indoor experimental evaluation and on-site anti-corrosion process implementation.

[0024] 2. Based on the aforementioned completion string structural parameters, conduct full-scale, full-process laboratory experiments on corrosion inhibitor injection technology to determine the optimal corrosion inhibitor, downhole injection tool type, corrosion inhibitor type, and preliminary injection procedure: The embodiments disclosed herein employ Figure 1 The indoor evaluation apparatus for corrosion inhibitors shown here differs from conventional standardized indoor evaluation experiments for corrosion inhibitors. This indoor experiment places greater emphasis on consistency with actual working conditions.

[0025] The experimental setup includes a downhole tubing module, a wellbore module, a corrosion inhibitor injection module, and a corrosive gas supply module. The downhole tubing module includes downhole tubing and a packer, used to simulate the actual downhole tubing structure of a high-temperature, high-pressure, sulfur-containing gas well. The packer forms a closed space between the tubing and the casing outside the downhole tubing. The wellbore module simulates the downhole casing and formation, forming an annular space with the downhole tubing module. The outer wall of the casing is equipped with an electrically heated sleeve, a corrosion inhibitor sampling port, and an observation window. The corrosion inhibitor injection module injects liquid corrosion inhibitor at a constant pressure or flow rate. The corrosive gas supply module injects corrosive gas into the wellbore and downhole tubing to simulate gas well production conditions.

[0026] use Figure 1 The apparatus shown in this disclosure is used to conduct an indoor full-scale, full-process corrosion inhibitor application experiment according to the following steps: (1) Based on the completion string parameters, run tubing of equal outer diameter and wall thickness, including several short sections for monitoring corrosion rate. The chemical injection valve 18 uses actual downhole tools to evaluate and select the best performance from different tools.

[0027] (2) A corrosion monitoring device is suspended on the wellhead plug. The corrosion rate is evaluated by measuring the weight loss of different materials after corrosion. Based on the corrosion rate data of the corrosion plate, the performance of the corrosion inhibitor and the effect of the entire injection process are evaluated.

[0028] (3) Open the N2 gas cylinder to purge the entire experimental pipeline.

[0029] (4) Based on the actual wellbore temperature, the wellbore is heated by the electric heating sleeve 7 on the outer wall of the casing, and the wellbore temperature is kept constant.

[0030] (5) Configure the simulated gas according to the actual gas composition. Close the first valve 4, and mix the different gases from H2S cylinder 13, CO2 cylinder 14, N2 cylinder 15, CH4 cylinder 16 into the gas mixing tank 21 according to the calculated gas volume. The mixture enters the booster pump 8, and the system pressure reaches the target experimental pressure by increasing the pressure of the pump 8.

[0031] Open the second valve 19 and the third valve 20 around the intermediate container 5, and turn on the motor 2. The high-pressure gas is continuously circulated in the pipeline by the agitator 6. The experimental gas flows in from the bottom of the wellbore, passes through the completion tubing, and then circulates continuously through the circulation pipeline to simulate the continuous gas production process in an actual wellbore.

[0032] (6) Open the water tank 11 and the corrosion inhibitor injection pump 10, and use the corrosion inhibitor injection pump 10 to inject corrosion inhibitor from the annulus between the oil casing and the casing. The injection regime includes different injection rates, different types of corrosion inhibitors, and different concentrations of corrosion inhibitors. The injection process is evaluated by recording the injection pressure and by observing the injection performance of the chemical agent injection valve 18 through the viewing window.

[0033] (7) After the experiment, turn off the CH4 gas cylinder, CO2 gas cylinder, H2S gas cylinder, water tank and injection pump, turn on the hydrogen sulfide purification box 1 and the high acid resistant storage tank 3, and turn on N2 to wash the gas.

[0034] (8) Open the simulated wellhead device at the top of the experimental setup, first remove the corrosion bracket 9, then remove the completion tubing string, remove the tubing short section, and use measuring equipment to measure the remaining weight, wall thickness, and dimensions of the corrosion bracket 9 and the tubing short section, calculate the corrosion rate, observe and record the surface corrosion morphology, and analyze the corrosion type and degree under the experimental regime.

[0035] (9) Further compare the corrosion effects under different chemical injection valves, different types of corrosion inhibitors, different injection cycles of corrosion inhibitors, and different injection amounts of corrosion inhibitors, and compare the working performance of chemical injection valves to achieve preliminary design of anti-corrosion process.

[0036] 3. Select wells for implementing the refined on-site anti-corrosion control process, confirm that the downhole temperature, pressure, H2S and CO2 content of the test wells are within the range of indoor experimental conditions, and adopt the tool type selected from indoor experiments for the downhole chemical agent injection valve.

[0037] 4. Install a continuous corrosion monitoring tree device for wellhead gas production without shutting in the well, and configure continuous monitoring equipment for wellhead corrosion parameters.

[0038] First, configure a continuous corrosion rate monitoring device at the wellhead, such as... Figure 2 As shown, unlike conventional gas production trees, a corrosion-resistant flap valve is added between the seventh valve 25 and the eighth valve 26 for installing and removing corrosion-resistant flaps 9. At the same time, bypass pipelines are installed above and below the seventh valve 25 and the eighth valve 26. By adjusting the gas production tree process, corrosion-resistant flaps can be replaced without shutting down the well.

[0039] Secondly, installing a component monitoring instrument on the surface process can monitor the iron ion content after well completion string corrosion and the ion content of substances after coating peeling off coated strings in real time, and further analyze the changes in the amount of corrosion products in the downhole string.

[0040] 5. Field test well annulus production casing valve connection corrosion inhibitor injection equipment.

[0041] 6. After the gas well's production stabilizes, inject a corrosion inhibitor into the annulus once and continuously monitor the ion content. Before the next corrosion inhibitor injection, monitor the corrosion level using a wellhead clamp. Repeat this cycle for three corrosion monitoring periods. If the ion content and corrosion rate increase, increase the frequency of corrosion inhibitor injections, and consider increasing the single injection volume and switching to a different type of corrosion inhibitor. Based on the gas well's production dynamics, if the corrosion rate decreases and the ion content decreases significantly, extend the corrosion inhibitor injection cycle, and consider reducing the single injection volume.

[0042] The following uses a specific block and a specific gas well as an example to illustrate the specific application of the method of this invention. This well is located in a block in the Sichuan Basin, with a target formation of marine facies. The wellbore temperature is 60-127℃, wellbore pressure is 50-72MPa, and daily natural gas production is 10×10⁻⁶. 4 m 3 / d, daily water production 5m 3 / d, the produced gas has a molar content of 1% H2S, 2% CO2, and 96% CH4, and is dry. The production tubing is expected to have an outer diameter of 88.9mm, made of 110SS, and use a tubing structure with a safety valve, chemical injection valve, and permanent packer. The expected casing outer diameter is 177.8mm. The specific steps are as follows:

[0043] Data collection was conducted on the target natural gas well.

[0044] Based on the actual downhole completion string structure and parameters, we conducted a full-scale, full-process laboratory experiment on corrosion inhibitor injection technology to determine the optimal corrosion inhibitor, downhole injection tool type, corrosion inhibitor type, and preliminary injection procedure.

[0045] (1) Based on the actual downhole tubing parameters, tubing with an outer diameter of 88.9 mm and a wall thickness of 6.45 mm was installed. The tubing also included three short sections to facilitate disassembly and corrosion rate measurement after the experiment. Two types of non-injection line tools commonly used in the Sichuan Basin were used for chemical injection valves. The purpose was to evaluate and select the best tools in the experiment to guide the selection of tools.

[0046] (2) A corrosion monitoring device is suspended on the wellhead plug. Three types of commonly used economical anti-sulfur materials, namely 110SS, coating and C110, are installed on the suspension rod of the device. The purpose is to evaluate the corrosion rate of the weight loss of the different materials after corrosion after the experiment.

[0047] (3) Open the N2 gas cylinder to purge the entire experimental pipeline.

[0048] (4) Based on the actual wellbore temperature, use the electric heating sleeve on the outer wall of the casing to heat the wellbore to 127°C and ensure that the wellbore temperature is constant.

[0049] (5) The prepared formation water is injected into the reactor. To ensure experimental accuracy, the maximum gas-liquid ratio is 500 m³ / s. 3 / m 3 Simulated gas was prepared according to the actual gas composition. First valve 4 was closed, and different gases—H2S, CO2, N2, and CH4—were mixed into a gas mixing tank based on calculated gas volumes. The mixture then entered a booster pump, increasing the system pressure to the target experimental pressure of 72 MPa. Second valve 19 and third valve 20 around the intermediate container were opened, and the motor was turned on. A stirring paddle continuously circulated the high-pressure gas within the pipeline. Experimental gas was injected from the lower part of the wellbore, passed through the completion tubing, and then circulated again through the pipeline to simulate the continuous gas production process within an actual wellbore. The gas flow rate was adjusted via a computer-controlled flow rate system to ensure a daily gas flow rate reaching the daily natural gas production of 10 × 10⁻⁶. 4 m 3 / d.

[0050] (5) The corrosion inhibitor was injected into the annulus between the oil casing and the casing using a corrosion inhibitor injection pump. For the type A corrosion inhibitor commonly used in the Sichuan Basin, the injection rate was 100 g / d and the injection cycle was 1 day. The injection process was evaluated by recording the injection pressure and by observing the injection performance of the chemical injection valve through a visual window.

[0051] (6) After the experiment, turn off the CH4, CO2, H2S gas cylinders, water tank and injection pump, turn on the hydrogen sulfide purification box and high acid resistant gas storage tank, and turn on N2 to wash the gas.

[0052] (7) Open the simulated wellhead device at the top of the experimental setup, first remove the corrosion-resistant clips, then remove the completion tubing string, remove the tubing sub, take macroscopic observation and photographs of the sub, cut it open, measure the local corrosion depth using a local corrosion depth sounder, and observe the morphology using a metallographic microscope. Measure and weigh the surface area of ​​the clips and other components, calculate the corrosion rate, observe and record the surface corrosion morphology, and analyze the corrosion type and degree under the experimental conditions.

[0053] (8) If the chemical agent injection valve fails to open normally, or the corrosion inhibitor is not efficient enough, further compare the corrosion effects under different chemical agent injection valves, different types of corrosion inhibitors, different corrosion inhibitor injection cycles, and different amounts of corrosion inhibitors, and compare the working performance of the chemical agent injection valves to achieve the preliminary design of the anti-corrosion process.

[0054] 3. Select wells for implementing refined on-site corrosion prevention and control technology.

[0055] The downhole temperature, pressure, H2S and CO2 content of the test well were confirmed to be within the range of the laboratory test conditions. The downhole chemical agent injection valve adopted the tool type selected in the laboratory test and was equipped with a continuous automatic injection system for corrosion inhibitors.

[0056] 4. Configure continuous monitoring equipment for wellhead corrosion parameters.

[0057] First, configure a continuous corrosion rate monitoring device at the wellhead, such as... Figure 2 As shown, corrosion-resistant pad valve is installed inside. Three 110SS corrosion-resistant inserts of the same material as the downhole tubing were installed. By adjusting the gas production tree process, corrosion-resistant insert replacement can be achieved without shutting in the well. A fluid composition monitor was installed at the outlet of the gas production tree in the surface process. This monitors the iron ion content of the completed tubing after corrosion in real time and stores the results in a storage device.

[0058] 5. Connect the annulus production casing valve of the field test well to the surface corrosion inhibitor injection pump.

[0059] 6. Within two weeks of stable production after well opening, a corrosion inhibitor is injected into the annulus at a rate of 20 kg / month. This is to ensure the injection valve is flexible and easy to use, and to continuously monitor ion content. The next corrosion inhibitor injection cycle is adjusted to one month. Corrosion degree is monitored using wellhead clips. The corrosion rate is 0.127 mm / a, and the iron ion content at the wellhead is 2 mg / l. After three corrosion monitoring cycles, the iron ion content continuously increases to 5 mg / l, and the corrosion rate continuously increases to 0.232 mm / a. The corrosion inhibitor injection cycle is then increased to 15 days, and corrosion monitoring is repeated. The results show that the corrosion rate has returned to 0.122 mm / a, basically meeting the block corrosion control requirements. Production is monitored according to this system.

[0060] This invention effectively combines indoor testing with on-site control. Accurate indoor experimental parameters obtained from full-scale, full-process experiments provide precise information on corrosion inhibitor types and key parameters for chemical injection valves, establishing a crucial foundation for on-site testing. Supplemented by on-site production fluid monitoring and corrosion-resistant coating monitoring, the actual effectiveness of the corrosion prevention process can be accurately grasped without shutting down the well or affecting production. This allows for timely dynamic and refined control of corrosion prevention measures such as corrosion inhibitor injection, truly achieving safe, economical, and efficient corrosion prevention. It provides crucial process support for the safe and economical exploitation of high-temperature, high-pressure, and high-sulfur wells.

[0061] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or technical improvements to the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for designing a corrosion protection process for high-temperature and high-pressure gas wells, characterized in that, include: Based on the target gas well's wellbore environmental parameters, fluid performance parameters, completion string structural parameters, and production parameters, an indoor corrosion inhibitor injection process experiment was conducted to compare the corrosion effects under different chemical agent injection valves, different types of corrosion inhibitors, different injection cycles, and different injection amounts of corrosion inhibitors, as well as the working performance of the chemical agent injection valves, and to complete the preliminary design of the corrosion prevention process. Based on the preliminary design results of the corrosion prevention process, after the target gas well has been put into production and is stable, the first injection of corrosion inhibitor will be carried out, and the ion content will be continuously monitored. Before the second injection of corrosion inhibitor, the corrosion degree will be monitored using the wellhead clip. This cycle will be repeated. After the corrosion degree monitoring reaches the set number of times, the corrosion inhibitor injection cycle and / or the single injection amount and / or the corrosion inhibitor type will be changed and adjusted according to the ion content and the corrosion degree.

2. The high-temperature and high-pressure gas well anti-corrosion process design method according to claim 1, characterized in that, The method for monitoring corrosion using wellhead clips includes: A continuous monitoring device for wellhead corrosion parameters is connected to the gas production tree device at the target gas wellhead. A corrosion-resistant plate valve is connected between the seventh valve (25) and the eighth valve (26) of the wellhead gas production tree device, and a corrosion-resistant plate (9) is installed inside the corrosion-resistant plate valve. A bypass branch is installed on the pipeline above the seventh valve (25) and below the eighth valve (26). The corrosion-resistant plate (9) can be replaced without shutting down the well by adjusting the gas production tree process through the bypass branch. The wellhead corrosion parameter continuous monitoring equipment is used to monitor the corrosion degree of the corrosion clip (9).

3. The high-temperature and high-pressure gas well corrosion prevention process design method according to claim 1 or 2, characterized in that: A corrosion inhibitor injection device is connected to the annulus production casing valve of the target gas well, and the corrosion inhibitor is injected through the corrosion inhibitor injection device.

4. The high-temperature and high-pressure gas well corrosion prevention process design method according to claim 3, characterized in that: The target gas well's wellbore environmental parameters, fluid performance parameters, completion string structural parameters, and production parameters include the target gas well's wellbore temperature, wellbore pressure, gas well production, H2S and CO2 content in the produced gas, and the type and parameters of downhole tools.

5. The high-temperature and high-pressure gas well anti-corrosion process design method according to claim 4, characterized in that, The method for continuous monitoring of ion content includes: A component monitoring instrument is installed on the ground to monitor the iron ion content after corrosion of the completion tubing and the ion content after the coating of coated tubing falls off in real time.

6. The high-temperature and high-pressure gas well anti-corrosion process design method according to claim 4 or 5, characterized in that, The experimental apparatus used in the corrosion inhibitor addition process experiment includes: The downhole tubing module adopts the structural parameters of the completion tubing.

7. The high-temperature and high-pressure gas well anti-corrosion process design method according to claim 6, characterized in that, The experimental apparatus also includes: Wellbore module, corrosion inhibitor injection module, and corrosive gas supply module; The wellbore module is used to simulate the downhole casing and formation, and works with the downhole tubing module to form an annular space between the oil casing and the casing. The outer wall of the downhole casing is equipped with an electric heating sleeve, a corrosion inhibitor sampling port and an observation window. The corrosion inhibitor injection module is used to inject liquid corrosion inhibitor at a constant pressure or a constant flow rate; The corrosive gas supply module is used to inject corrosive gas into the wellbore and downhole tubing to simulate gas well production conditions.

8. The high-temperature and high-pressure gas well anti-corrosion process design method according to claim 7, characterized in that, The method for the corrosion inhibitor application process experiment includes the following steps: (1) According to the completion string parameters, run in tubing with the same outer diameter and wall thickness, and the tubing includes several short sections for monitoring corrosion rate; (2) A corrosion monitoring device is suspended at the wellhead, and the performance of the corrosion inhibitor and the injection process are evaluated based on the corrosion rate data of the device. (3) Open the N2 gas cylinder to purge the experimental pipeline; (4) Based on the actual wellbore temperature, use an electric heating jacket to heat the wellbore to ensure a constant wellbore temperature; (5) Configure the simulated gas according to the actual gas composition; close the first valve (4), and mix the above different gases into the gas mixing tank (21) according to the calculated gas volume from the H2S gas cylinder (13), CO2 gas cylinder (14), N2 gas cylinder (15), and CH4 gas cylinder (16), and increase the pressure of the system by increasing the pressure of the pump (8) to reach the target experimental pressure; Open the second valve (19), the third valve (20) and the motor (2), and use the agitator (6) to make the high-pressure gas circulate continuously in the pipeline; The experimental gas flows in from the bottom of the wellbore, passes through the completion tubing, and then circulates continuously through the circulation pipeline to simulate the continuous gas production process in an actual wellbore. (6) Open the water tank (11) and the corrosion inhibitor injection pump (10), and use the corrosion inhibitor injection pump (10) to inject corrosion inhibitor from the annulus between the oil casing and the casing. The injection system includes different injection rates, different types of corrosion inhibitors, and different concentrations of corrosion inhibitors. The injection process is evaluated by recording the injection pressure and by using the visual window to evaluate the injection performance of the chemical agent injection valve (18). (7) After the experiment, turn off the CH4 gas cylinder, CO2 gas cylinder, H2S gas cylinder, water tank and injection pump, open the hydrogen sulfide purification box (1) and the high acid resistant storage tank (3), and open the N2 gas cylinder (15) for gas washing; (8) After the experiment, the corrosion clip (9) is removed first, the completion string is removed, the tubing section is removed, and the remaining weight, wall thickness, and size of the corrosion clip (9) and tubing section are measured using measuring equipment. The corrosion rate is calculated, and the surface corrosion morphology is observed and recorded to analyze the corrosion type and degree under the experimental conditions.

9. The high-temperature and high-pressure gas well anti-corrosion process design method according to claim 7 or 8, characterized in that: The set number of times for monitoring the degree of corrosion is 3.

10. The high-temperature and high-pressure gas well corrosion prevention process design method according to claim 9, characterized in that, The method for adjusting the corrosion inhibitor injection cycle and / or the single injection volume and / or the type of corrosion inhibitor based on the ion content and the degree of corrosion includes: If the ion content and the degree of corrosion increase, the corrosion inhibitor application cycle should be increased and / or the single application amount of corrosion inhibitor should be increased and / or other types of corrosion inhibitor should be replaced; if the ion content and the degree of corrosion decrease, the corrosion inhibitor application cycle should be extended and / or the single application amount of corrosion inhibitor should be reduced.

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