A method for testing downhole tools in an aggressive solution environment

Abstract

The application discloses a kind of corrosion solution environment under downhole tool testing method, belong to petroleum engineering experimental technical field.The method uses heat conducting oil as the multifunctional medium of heat transfer and pressure transmission, including steps: heat conducting oil is heated and maintains experimental temperature;With the experiment casing of tool and corrosive medium is immersed in hot oil to quickly heat;The pressure generated by pressure control system is transmitted to the medium in experimental casing by a pressure transmission system, wherein the pressure transmission system realizes the physical isolation of pressure control system and corrosive medium with heat conducting oil as the intermediate;After testing, the casing is removed, cooled and simultaneously depressurized;Finally, the waste heat conducting oil mixed with corrosive medium is recycled and treated, realizing the harmless of medium and the recycling of heat conducting oil.The application realizes the simulation of downhole high temperature and high pressure strong corrosion environment on conventional experimental device by the collaborative design of heat conducting oil intermediate and pressure transmission system, which is safe, low cost and high fidelity.

Description

Technical Field

[0001] This invention relates to the field of downhole tool testing technology, and in particular to a method for testing downhole tools in a corrosive solution environment. Background Technology

[0002] In the process of oil and gas extraction, downhole tools need to operate for extended periods in high-temperature, high-pressure, and corrosive environments. Therefore, performance testing of downhole tools in corrosive solution environments is of great significance. Traditional downhole tool testing methods typically involve direct heating, immersing the tool directly in the corrosive test medium for testing.

[0003] In the prior art, CN107421878B discloses a corrosion test device and method for simulating continuous operating conditions. This device includes a media displacement unit, a corrosion test unit, a temperature and pressure control unit, and a waste liquid recovery unit, capable of realistically simulating the fluid corrosion of oil casing under high temperature and high pressure conditions during continuous operation. CN209261531U discloses a rapid-cooling downhole tool simulation test well, which accelerates the cooling rate of the test well body by continuously replacing the heat transfer oil through a cooling box and corresponding pipes and valves in the circulation pipeline. However, existing downhole tool testing methods and devices have the following technical problems: First, current domestic simulation test equipment, due to the use of conventional alloy steel materials, only meets the temperature and pressure resistance tests in neutral environments such as oil and water, and cannot conduct complete downhole tool tests in acidized environments. Furthermore, highly corrosion-resistant test devices are expensive, costing millions of yuan. Second, in existing downhole tool testing methods, the tool is immersed in the test medium throughout the heating and cooling process, which cannot meet the experimental requirements for soluble materials with strict immersion time requirements. Furthermore, acidic and alkaline test media are highly volatile and corrosive, and their pressure increases significantly under high temperatures, posing safety hazards. These issues severely limit the accuracy of performance evaluation and safety testing of downhole tools in corrosive environments. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for testing downhole tools in a corrosive solution environment, which can use a temperature and pressure simulation device made of conventional materials to test the performance of downhole tools in a corrosive environment.

[0005] The technical solution of this invention is:

[0006] A method for testing downhole tools in a corrosive solution environment, using heat transfer oil as the medium, includes the following steps:

[0007] The heat transfer oil is heated using a heat transfer oil heating device to reach and maintain the predetermined experimental temperature.

[0008] The test casing, which is sealed and contains downhole tools and corrosive test media, is immersed in heat transfer oil at the test temperature to raise the internal temperature of the test casing to the test temperature.

[0009] At this temperature, the pressure control system applies a predetermined experimental pressure to the corrosive experimental medium inside the experimental casing through a pressure transmission system connected to the experimental casing.

[0010] After the predetermined test time has elapsed, the heat-conducting oil is removed from the test sleeve, and the sleeve is cooled.

[0011] While cooling, the pressure inside the experimental sleeve and pressure transmission system is released;

[0012] Collect and dispose of heat transfer oil that has become contaminated with corrosive experimental media during the testing process.

[0013] Furthermore, the pressure transmission system is divided into a first chamber and a second chamber by a piston; the first chamber is connected to the pressure control system via a high-pressure pipeline, and the second chamber is connected to the experimental sleeve via a high-pressure pipeline; the first chamber is filled with heat-conducting oil.

[0014] Furthermore, the volume of the first chamber is larger than that of the second chamber, and the volume ratio is greater than 20:1.

[0015] Furthermore, a temperature measuring module is installed inside the experimental sleeve to monitor the actual temperature inside the experimental sleeve in real time; when the temperature measuring module detects that the internal temperature has reached the experimental temperature, it starts to calculate the predetermined test time.

[0016] Furthermore, the immersion operation is achieved by a lifting device; the cooling operation is achieved by a spray device installed on the lifting device.

[0017] Furthermore, a pressure relief pipeline is also provided on the first chamber; the pressure relief pipeline includes a main pressure relief pipeline and an auxiliary pressure relief pipeline arranged in parallel;

[0018] The main pressure relief pipeline is equipped with a first electrically controlled valve and a safety valve connected in series; the auxiliary pressure relief pipeline is equipped with a second electrically controlled valve.

[0019] Furthermore, during the heating process, the first electrically controlled valve remains open, so that the pressure transmission system and the pressure inside the experimental sleeve are controlled by the safety valve.

[0020] Furthermore, the step of releasing pressure within the test sleeve and pressure transmission system includes:

[0021] While the pressure control system is depressurizing, the first and second solenoid valves are opened, and the system is depressurized through the parallel main depressurization line and the auxiliary depressurization line. The pressure in the test line is monitored in real time by the pressure control system, which is continuously connected to the system, until the pressure is released to atmospheric pressure.

[0022] Furthermore, the specific steps for collecting and processing the heat transfer oil mixed with corrosive experimental media during the testing process include:

[0023] The heat transfer oil mixed with corrosive experimental medium components after testing is introduced into the heat transfer oil heating device;

[0024] Use a plug to seal the heat transfer oil storage device and connect the connecting pipe to the neutralization container;

[0025] The mixture inside the heating device is heated and maintained above 100°C, causing the corrosive experimental medium components to evaporate into vapor;

[0026] The corrosive experimental medium vapor is introduced into the neutralization liquid in the neutralization container through the connecting conduit, where it is neutralized and recovered;

[0027] The purified heat transfer oil, after the corrosive experimental medium components have been separated, is returned to the heat transfer oil storage device for recycling in subsequent experimental operations.

[0028] The beneficial effects of this invention are:

[0029] A temperature and pressure simulation device made of conventional materials is used to test the temperature and pressure resistance of downhole tools under acidic and alkaline conditions, solving the problem that it is currently impossible to effectively test the performance of downhole tools under corrosive media conditions; it can directly reduce the cost of experimental equipment and avoid the use of expensive, highly corrosive materials; the use of dual pressure relief plus rapid cooling and uninterrupted pressure testing greatly reduces safety hazards. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the experimental framework;

[0031] Figure 2 This is a schematic diagram of the experimental medium recovery;

[0032] Figure 3 This is a diagram illustrating the rapid cooling phase. Detailed Implementation

[0033] The following is in conjunction with the appendix Figure 1-3 The embodiments of the present invention will be further described below. The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0034] Example 1

[0035] Currently, domestic simulation test equipment, due to the use of conventional alloy steel materials, only meets the requirements for temperature resistance and pressure bearing tests in neutral environments such as oil and water, and cannot conduct tests on a complete set of downhole tools in corrosive environments, especially acidic environments. Test equipment with strong corrosion resistance is expensive, costing millions of yuan. In existing downhole tool test methods, the tools are immersed in the test medium throughout the heating and cooling process, which cannot meet the test requirements of soluble materials and other materials that have strict requirements on immersion time. Acidic and alkaline test media are highly volatile and corrosive, and the pressure will rise significantly under high temperature conditions, posing safety hazards.

[0036] This invention provides a method for testing downhole tools in a corrosive solution environment. Using heat transfer oil as the medium, it effectively avoids corrosive damage to the pressure control system and high-pressure pipelines caused by the corrosive experimental medium, while simultaneously achieving precise temperature and pressure control. The method includes:

[0037] The heat transfer oil is heated using a heat transfer oil heating device to reach and maintain the predetermined experimental temperature.

[0038] Specifically, the heating process in this invention is mainly achieved through an experimental casing, a heat transfer oil heating tank, a lifting system, and a temperature sensor inside the casing. First, an external heat source is prepared and controlled; in this embodiment, a heat transfer oil heating tank is selected as the heating device. The volume of the heat transfer oil heating tank is selected based on the experimental scale (e.g., 50L to 500L, the tank volume is generally more than 10 times that of the experimental casing), and the tank is made of stainless steel to ensure pressure resistance and heat resistance. The tank is filled with sufficient synthetic aromatic heat transfer oil, with its initial liquid level at least covering the heating elements inside the tank. The heat transfer oil inside the tank is heated by an electric heater in the tank. The heating process uses a preset experimental target temperature as the set point. This target temperature is determined based on the actual operating conditions of the downhole tool and can be selected within the range of room temperature to 300°C (e.g., common set values ​​are 120°C, 150°C, 177°C, or 200°C). The system uses its built-in temperature control unit to monitor the temperature of the heat transfer oil in the tank in real time and adjusts the power output of the electric heater to ensure that the heat transfer oil temperature reaches the target experimental temperature and is automatically maintained at that temperature. Its steady-state control accuracy is within the range of ±2℃ to ±5℃. The heat transfer oil has stable chemical properties (high flash point, low volatility) and good thermal conductivity within the set operating temperature range, ensuring its effectiveness and safety as a heat transfer medium.

[0039] The test casing, which is sealed and contains downhole tools and corrosive test media, is immersed in heat transfer oil at the test temperature to raise the internal temperature of the test casing to the test temperature.

[0040] Specifically, after the heat transfer oil in the heat transfer oil tank reaches and stabilizes at the predetermined experimental temperature, an immersion step is performed. This step uses a mechanical lifting device, such as an electric hoist, hydraulic lift, or servo motor-driven hoist; in this embodiment, a servo motor-driven hoist is used for immersion. The pre-sealed test casing is smoothly and vertically immersed below the liquid surface of the heat transfer oil tank. The test casing is a pressure-resistant tube sealed at one end and at the other end through a high-pressure plug. It contains the downhole tool to be tested and a sufficient amount of corrosive experimental medium, such as a 15%-28% hydrochloric acid solution. The test casing is made of alloy structural steel. After immersion, the high-temperature heat transfer oil coats the outer wall of the test casing, and heat is continuously transferred inward through the alloy structural steel wall of the test casing via thermal conduction, causing the temperature of the internal space of the casing and the contained medium and tool to gradually rise. To accurately monitor this internal heating process, a temperature measuring module is integrated or fixed inside the test casing during sealing. The temperature measuring module consists of a sealed short-circuit made of a corrosion-resistant alloy. In this embodiment, the temperature measuring module is made of Hastelloy. The short-circuit is filled with a small amount of heat-conducting oil and encapsulates a temperature sensing element, which in this embodiment is a type K thermocouple. The signal line of the sensing element is led out through a sealed joint on the sleeve and connected to an external data acquisition instrument or control system. The system reads the actual internal temperature of the sleeve fed back by the temperature measuring module in real time. When the temperature reaches and stabilizes at the predetermined experimental temperature (e.g., the deviation from the set temperature of the heat-conducting oil tank is within ±3℃), thermal equilibrium is considered to be completed. At this time, the control system records this time point as the starting zero point of the experimental test cycle and begins the subsequent pressurization steps and the accumulation of test time. In this way, precise control of the effective heating time of the tool in the corrosive medium is achieved, eliminating the additional exposure time error caused by the slow overall system heating in traditional methods.

[0041] At this temperature, the pressure control system applies a predetermined experimental pressure to the corrosive experimental medium inside the experimental casing through a pressure transmission system connected to the experimental casing.

[0042] Specifically, a pressure-bearing closed loop is formed by sequentially connecting a pressure control system, a first high-pressure connection pipeline, a pressure transmission system, a second high-pressure connection pipeline, and an experimental sleeve. The main body of the pressure transmission and isolation system is a high-pressure resistant cylinder. In this embodiment, an 8mm high-pressure metal pipe is used, capable of withstanding an output pressure of 400MPa. Internally, it is divided into a first chamber and a second chamber with a volume ratio greater than 20:1 by a piston with a bidirectional seal. The first chamber is connected to the pressure control system via the first high-pressure metal pipe and is filled with pure heat transfer oil. The second chamber is connected to the experimental sleeve via a second high-pressure metal pipe of the same specification. The function of the pressure transmission system is to completely physically isolate the pressure control system from the corrosive experimental medium, thereby achieving the goal of completing high-pressure testing in corrosive environments using conventional, low-cost equipment. During operation, the pressure control system drives the heat transfer oil to push the piston, transmitting pressure without attenuation to the medium inside the experimental sleeve. In this structure, the corrosive medium is completely confined within a closed loop consisting of the second chamber, the second high-pressure pipe, and the experimental sleeve. The viscosity of the heat transfer oil and the path resistance of the slender high-pressure pipe work together to effectively prevent the medium from diffusing to the pressure control system side, thus achieving safe, reliable, and low-cost high-pressure experiments with conventional materials and equipment.

[0043] After the predetermined test time has elapsed, the heat-conducting oil is removed from the test sleeve, and the sleeve is cooled.

[0044] Specifically, after the preset test duration is reached, the experiment is terminated and a rapid cooling step is executed. This step involves operating the mechanical lifting device to remove the experimental sleeve from the high-temperature heat transfer oil, and then using a spray cooling device to continuously spray the outer wall of the experimental sleeve to achieve rapid cooling. In this embodiment, the spray cooling operation is achieved through a fluid spray device consisting of a liquid source, pump, pipeline, and nozzles. This device is configured to automatically or manually activate when the lifting device is removed from the experimental sleeve, spraying a cooling medium (such as room temperature water) onto the outer wall of the experimental sleeve to achieve a rapid and uniform forced cooling effect. This spray cooling utilizes the contact between a room temperature liquid (such as water) and the high-temperature sleeve surface, carrying away a large amount of heat through evaporation and convection. The primary purpose of this operation is to reduce the temperature of the experimental sleeve to a safe operating range within a short time, thereby allowing for rapid tool disassembly and significantly shortening the experimental cycle. More importantly, this active cooling process synergizes with the system's pressure relief steps: the rapid temperature drop effectively inhibits the continued evaporation of the corrosive experimental medium, thereby accelerating the decrease in internal system pressure and creating the necessary conditions for subsequent safe pressure relief and disassembly. Cooling operations can continue until the temperature measurement module confirms that the internal temperature has dropped to a safe threshold or the predetermined cooling time has been reached.

[0045] While cooling, the pressure inside the experimental sleeve and pressure transmission system is released;

[0046] Specifically, the pressure relief step is performed simultaneously with cooling. Because corrosive experimental media (such as 20% hydrochloric acid) are highly volatile at high temperatures (e.g., 177°C), the main pressure relief of the pressure control system alone cannot quickly and completely release the system pressure, posing a safety hazard. Therefore, this method employs an active multi-stage pressure relief mode. The core of this mode is the parallel dual-path pressure relief control valve group integrated into the pressure transmission system. More specifically, while the pressure control system begins main pressure relief, the first and second solenoid valves are opened. This allows the system pressure to be released not only through the main loop of the pressure control system but also through two parallel channels: the main pressure relief pipeline (via the first solenoid valve and the safety valve) and the auxiliary pressure relief pipeline (via the second solenoid valve), thereby greatly increasing the pressure relief flow rate and speed. During this process, the pressure control system maintains continuous connection with the pressure transmission system, monitoring the pressure value within the test loop in real time. When the pressure drops below the set trigger pressure of the safety valve, the auxiliary pressure relief pipeline can continue to operate, ensuring that the pressure is completely released. The entire depressurization process continues until the monitoring system confirms that the pressure within the loop has completely dropped to atmospheric pressure, thereby avoiding any residual pressure risk during subsequent disassembly operations. It should be noted that this active depressurization process is synchronized with the aforementioned rapid cooling step of the test casing by spraying. The cooling operation rapidly reduces the temperature of the test casing, effectively inhibiting the continuous evaporation of corrosive media and fundamentally reducing the pressure source; while the multiple depressurization channels quickly release existing pressure. The combined operation of both ensures that the system pressure can be safely and rapidly reduced to atmospheric pressure, constituting a complete and reliable safety terminal control link in this method.

[0047] Collect and dispose of heat transfer oil that has become contaminated with corrosive experimental media during the testing process.

[0048] Specifically, because a small amount of experimental medium may diffuse or leak into the heat transfer oil in the pressure transmission system and the experimental casing during the experiment, this portion of heat transfer oil needs to be specially treated. After the entire testing process is completed, the heat transfer oil that may have been contaminated by corrosive experimental media is safely recovered and recycled. This step is based on the principle of boiling point difference separation of the equipment, using the heat transfer oil storage device in the main experimental process as the core processing container, and is carried out according to the following procedure: all the heat transfer oil that may have been mixed with corrosive experimental media (such as hydrochloric acid) in the pressure transmission system and the experimental casing circuit is introduced into the heat transfer oil storage device and mixed with the original heat transfer oil in the device; a special sealing plug is used to seal the top opening of the heat transfer oil storage device. Subsequently, one end of a connecting pipe is sealed to the interface on the plug, and the other end is inserted below the surface of the neutralizing liquid (such as sodium bicarbonate solution for hydrochloric acid) contained in an independent neutralization container to form a liquid seal. Thus, a closed gas guide channel is formed from the storage device to the neutralization container. The original heating device of the heat transfer oil storage device is activated to heat the mixed oil in the device and precisely maintain it within a temperature range above 100°C but far below the flash point of the heat transfer oil (e.g., 120°C-180°C). Utilizing the significant boiling point difference between the corrosive experimental medium and the heat transfer oil (e.g., 20% hydrochloric acid has a boiling point of approximately 110°C, while the flash point of synthetic heat transfer oil is typically above 250°C), the corrosive medium component (e.g., HCl) is evaporated into gas, while the main body of the heat transfer oil remains liquid. Under the pressure within the system, the evaporated corrosive gas is completely discharged through the connecting conduit and bubbled through the neutralizing liquid in the neutralization container, undergoing a vigorous neutralization reaction and transforming into a harmless or usable salt solution (e.g., sodium chloride solution). Heating is stopped when the evaporation process is complete (usually indicated by the absence of further gas production). At this point, the remaining liquid in the heat transfer oil storage device is the regenerated pure heat transfer oil. Once its temperature is suitable, it can be directly stored in the device or returned to the main system circulation for reuse in subsequent experiments. Meanwhile, the salt solution generated in the neutralization container can be used as raw material for other experiments (such as solubility testing), realizing the secondary utilization of resources. This step reuses the main experimental equipment in the waste liquid treatment process, simultaneously achieving the harmless treatment of hazardous waste liquid, the recycling of expensive media, and the resource utilization of by-products without significantly increasing the amount of specialized equipment, thus combining safety, economy, and environmental protection.

[0049] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for testing downhole tools in a corrosive solution environment, characterized in that, Using heat transfer oil as the medium, this method includes the following steps: The heat transfer oil is heated using a heat transfer oil heating device to reach and maintain the predetermined experimental temperature. The test casing, which is sealed and contains downhole tools and corrosive test media, is immersed in heat transfer oil at the test temperature to raise the internal temperature of the test casing to the test temperature. At this temperature, the pressure control system applies a predetermined experimental pressure to the corrosive experimental medium inside the experimental casing through a pressure transmission system connected to the experimental casing. After the predetermined test time has elapsed, the heat-conducting oil is removed from the test sleeve, and the sleeve is cooled. While cooling, the pressure inside the experimental sleeve and pressure transmission system is released; Collect and dispose of heat transfer oil that has become contaminated with corrosive experimental media during the testing process.

2. The method according to claim 1, characterized in that, The pressure transmission system is divided into a first chamber and a second chamber by a piston; the first chamber is connected to the pressure control system via a high-pressure pipeline, and the second chamber is connected to the experimental sleeve via a high-pressure pipeline; the first chamber is filled with heat-conducting oil.

3. The method according to claim 2, characterized in that, The volume of the first chamber is larger than that of the second chamber, and the volume ratio is greater than 20:

1.

4. The method according to claim 1, characterized in that, The experimental sleeve is equipped with a temperature measuring module for real-time monitoring of the actual temperature inside the experimental sleeve; when the temperature measuring module detects that the internal temperature has reached the experimental temperature, it begins to calculate the predetermined test time.

5. The method according to claim 1, characterized in that, The immersion operation is achieved by a lifting device; the cooling operation is achieved by a spray device installed on the lifting device.

6. The method according to claim 2, characterized in that, A pressure relief pipeline is also provided on the first chamber; the pressure relief pipeline includes a main pressure relief pipeline and an auxiliary pressure relief pipeline arranged in parallel. The main pressure relief pipeline is equipped with a first electrically controlled valve and a safety valve connected in series; the auxiliary pressure relief pipeline is equipped with a second electrically controlled valve.

7. The method according to claim 6, characterized in that, During the heating process, the first electrically controlled valve is kept open, so that the pressure transmission system and the pressure inside the experimental sleeve are controlled by the safety valve.

8. The method according to claim 7, characterized in that, The steps for releasing pressure within the test sleeve and pressure transmission system include: While the pressure control system is depressurizing, the first and second solenoid valves are opened, and the system is depressurized through the parallel main depressurization line and the auxiliary depressurization line. The pressure in the test line is monitored in real time by the pressure control system, which is continuously connected to the system, until the pressure is released to atmospheric pressure.

9. The method according to claim 1, characterized in that, The specific steps for collecting and processing the heat transfer oil that has become mixed with corrosive experimental media during the testing process include: The heat transfer oil mixed with corrosive experimental medium components after testing is introduced into the heat transfer oil heating device; Use a plug to seal the heat transfer oil storage device and connect the connecting pipe to the neutralization container; The mixture inside the heating device is heated and maintained above 100°C, causing the corrosive experimental medium components to evaporate into vapor; The corrosive experimental medium vapor is introduced into the neutralization liquid in the neutralization container through the connecting conduit, where it is neutralized and recovered; The purified heat transfer oil, after the corrosive experimental medium components have been separated, is returned to the heat transfer oil storage device for recycling in subsequent experimental operations.

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