A method and device for downhole testing under pressure maintenance conditions during CO2 sequestration

Abstract

The application discloses a kind of for CO2 burial stage pressure maintaining condition downhole testing method and device, comprising: to the pre-pressurization process of execution in testing pressure maintaining system device;Based on logging instrument, the testing process of the testing pressure maintaining system device that has been pre-pressurized is executed, ground testing instrument works;The logging instrument and the ground testing instrument are detachably connected with the testing pressure maintaining system device;To the depressurization process of execution in the testing pressure maintaining system device that has been tested.An aspect, wellhead pressure maintaining method suitable for CO2 burial stage pressure logging is invented, not only meet the requirement of overall pressure resistance ability, and have the ability to carry out logging work in high-pressure environment, solve the problem that conventional logging is difficult to effectively carry out, lay the foundation for the monitoring of CO2 long-term burial.On the other hand, a pressure maintaining supporting device is invented, realizes fine control of depressurization process, and the duration of depressurization can reach 15 days, so that the insulating parts and sealing parts of rubber and other materials susceptible to CO2 corrosion are not damaged, and the orderly development of logging work is ensured.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, and particularly to a downhole testing method and apparatus for CO2 storage under pressure-maintaining conditions. Background Technology

[0002] Conventional logging technology is a mature technology; its device diagram is attached. Figure 1 The system includes components such as a blowout preventer (BOP), cable, winch, tubing valves, tubing valves, main valve, casing valve, wellhead assembly, casing, testing tools, surface instruments, and a vehicle-mounted platform. The BOP is installed above the wellhead assembly. One end of the cable is connected to the surface instruments via the winch, and the other end passes through the BOP and connects to the testing tools, suspended inside the casing. The vehicle-mounted platform supports the winch and surface instruments. From top to bottom, the BOP is equipped with tubing valves, tubing valves, main valves, and casing valves. By controlling the opening and closing of these valves, logging instruments are lowered into the low-pressure (<5MPa) wellbore. The surface winch controls the instrument's movement speed, and the testing instruments record test signals on the surface.

[0003] A well logging blowout preventer is a safety device installed on the top of the wellhead during well logging in casing wells to prevent high-temperature, high-pressure fluids (oil, gas, steam, water) from being ejected from the wellhead and to maintain logging under normal pressure in the production well, also known as "closed logging".

[0004] Based on the needs of well logging, well logging blowout preventers are divided into the following three categories: Low-pressure logging blowout preventers (BOPs) are used for logging production wells with wellhead pressures of 3-5 MPa. In annular production profile logging, three types of BOPs are used: deployable BOPs (where the BOP can be laid horizontally during logging), vertical BOPs (standing upright above the eccentric wellhead with an inclination angle not exceeding 30 degrees), and inclined BOPs (equipped with a structure that allows the BOP to be tilted at a 50° angle). All three types of BOPs do not interfere with the operation of the pumping unit during logging.

[0005] High-pressure logging blowout preventers (BOPs) are suitable for logging wells with high wellhead pressure. Their BOP housing contains three flow tubes (smooth steel pipes that allow the logging cable to pass through). The logging cable passes through these tubes with a gap of 0.15-0.30 mm. A grease pump continuously injects high-pressure sealing grease into the flow tubes to seal and lubricate the logging cable under high pressure. High-pressure logging BOPs are available in pressure ratings of 32 MPa, 50 MPa, 70 MPa, and 100 MPa.

[0006] The high-temperature logging blowout preventer is suitable for logging with a combined temperature-pressure-flow logging tool. The blowout preventer contains a high-temperature resistant (370-400℃) sealing box. The operator can use the fastening gear transmission rod on the ground to adjust the tightness of the sealing box and keep it away from the high-temperature wellhead.

[0007] Similar high-pressure testing conditions are achieved by adding a high-pressure blowout preventer (BOP) to the top of the wellhead equipment, with a maximum pressure of up to 100 MPa. The mechanism is the same as that under low-pressure conditions, which relies on the rubber inside the BOP to wrap and seal the cable. The higher the pressure, the more rubber layers there are, and the stronger the wrapping pressure.

[0008] Conventional logging techniques are generally only suitable for ordinary oil and gas wells and water wells, where liquids or gases have minimal corrosive and destructive effects on rubber. However, conventional logging methods are unsuitable when the wellbore is filled with carbon dioxide (CO2) gas. CO2 gas has a high destructive effect on rubber materials, and the higher the pressure, the stronger the damage. Especially when transitioning from high pressure to normal pressure, the CO2 gas that has penetrated deep into the rubber is slowly released, causing blistering on the rubber surface and internal cracking. Consequently, the sealing rubber inside the blowout preventer and the insulation layer of the cable will be damaged. Common solutions to this problem include improving the rubber's resistance to CO2 gas corrosion and slowing down the pressure drop.

[0009] Conventional well logging typically takes about 2 to 3 hours, while the process of non-destructively reducing the pressure of CO2-resistant rubber from 5 MPa also takes 2 to 3 days.

[0010] In CO2 enhanced oil recovery (EOR) development, when logging the injection well, the wellhead pressure should not exceed 3 MPa. Conventional logging methods can be used, but they still cause significant damage to the cables. If CO2 is deposited within the geological body, the pressure inside the injection well will continuously increase, with the wellhead pressure ranging from 10 to 30 MPa. In this case, conventional logging under pressure is no longer feasible.

[0011] CO2 burial is the most effective way to rapidly reduce CO2 emissions, and downhole monitoring during the burial process is an essential safety measure.

[0012] To address the aforementioned problems, this invention employs a wellhead pressure-maintaining method to achieve live logging. The developed device can also create an independent, slow pressure reduction space after testing, ensuring the integrity of logging instruments and equipment. Summary of the Invention

[0013] The purpose of this invention is to provide a downhole testing method and apparatus for CO2 burial stage under pressure-maintaining conditions. On one hand, it invents a wellhead pressure-maintaining method suitable for live logging during the CO2 burial stage, which not only meets the overall pressure resistance requirements but also enables logging operations to be conducted in high-pressure environments, solving the problem of the difficulty in effectively conducting conventional logging and laying the foundation for long-term CO2 burial monitoring. On the other hand, it invents a pressure-maintaining supporting device to achieve precise control of the pressure reduction process, with a pressure reduction period of up to 15 days, ensuring that insulating and sealing components made of materials such as rubber, which are susceptible to CO2 corrosion, remain undamaged, and guaranteeing the orderly conduct of logging operations. To achieve the above objectives, this invention provides the following technical solution: According to a first aspect of the present invention, the present invention relates to a downhole testing method for CO2 storage under pressure-maintaining conditions, the steps of which are as follows: Figure 2 As shown, it includes: Perform a pre-pressurization process within the test pressure holding system device; Based on the logging tool, a test process is performed on the test pressure holding system device that has undergone pre-pressurization, and the test surface instrument works; both the logging tool and the test surface instrument are detachably connected to the test pressure holding system device. A pressure reduction process is performed within the test pressure holding system device that has already undergone the test process; Specifically, the pre-pressurization process performed on the test pressure holding system device includes the following steps: Protective gas is injected at equal pressure through the injection port of the isolation pipe until the pressure inside the isolation pipe is equal to the pressure at the wellhead.

[0014] Specifically, the test process for the pre-pressurized test holding system device includes the following steps: The logging tool is lowered to the bottom of the well. During the descent, data is tested, recorded, and transmitted to test the operation of the surface instruments. The logging tool is pulled up, and during the upward movement, data is continuously tested, recorded, and transmitted to test the operation of the surface instruments. Raise the logging instrument into the isolation pipe to complete the test and shut down the test surface instruments.

[0015] Specifically, the pressure reduction process performed within the test pressure holding system device that has already undergone the test process includes the following steps: Inject inert protective gas into the isolation pipe injection port and open the pressure relief port; Close the injection port and the pressure relief port, and open the connection between the bottom of the isolation pipe and the wellhead device; Open the pressure relief port and control the pressure relief speed until the pressure relief is complete.

[0016] Furthermore, the testing method also includes: Install the aforementioned test pressure holding system device; The pressure holding system device that has undergone the pressure reduction process is disassembled.

[0017] Specifically, the steps for installing the test pressure holding system device are as follows: Determine the installation location of the isolation pipe at the wellhead, close the isolation valve, and open the plug; Install the relevant accessories inside the pressure-resistant cylinder, connect the power supply line, reserve the length of the cable lowering connector, and connect the cable routing interface of the pressure-resistant cylinder to the flange of the isolation pipe; Determine the installation location of the vehicle-mounted platform at the wellhead, and pre-insert the cable lowering connector into the isolation pipe flange; Pull the cable downhole connector out of the isolation pipe, pass it through the suspension block, and connect it to the logging instrument; Tighten the plug at the top of the isolation tube to complete the installation of the test pressure holding system device.

[0018] Furthermore, before installing the test pressure holding system, a device that meets the basic parameters is selected, as follows: Determine the outer diameter, inner diameter, and total length of the pressure-resistant cylinder; determine the length, outer diameter, and inner shaft outer diameter of the drum; determine the total length of the isolation tube; and determine the outer diameter of the cable and the outer diameter of the wire rope.

[0019] Furthermore, the disassembly process includes: removing the logging instrument and disassembling the isolation tube and pressure-resistant cylinder.

[0020] According to a second aspect of the present invention, the present invention relates to a downhole testing apparatus for CO2 storage under pressure-holding conditions, the testing apparatus comprising: a pressure-holding testing system, a logging instrument, and a surface testing instrument; wherein, The logging instrument is suspended on the test pressure holding system device, and both the logging instrument and the test surface instrument are detachably connected to the test pressure holding system device. The test pressure holding system device is used to perform a pre-pressurization process, or to perform a depressurization process within the test pressure holding system device that has already undergone the test process; The logging instrument is used to perform a test process on the test pressure holding system device that has undergone the pre-pressurization process; The ground-based test instrument is used to receive, record, and transmit data.

[0021] Furthermore, the test pressure holding system device includes: a pressure-resistant cylinder, a wiring system, an isolation pipe, and a vehicle-mounted platform, wherein, The pressure-resistant cylinder is connected to the isolation pipe flange, and the wiring system is detachably connected to the vehicle platform. The wiring system is located inside the pressure-resistant cylinder and is detachably connected to the pressure-resistant cylinder.

[0022] The technical effects and advantages of this invention are as follows: First, it is a wellhead pressure-maintaining method suitable for live logging during the CO2 burial stage, and its overall pressure resistance meets the requirements, solving the problem that conventional logging is difficult to carry out effectively. Second, the invented pressure-maintaining device can ensure that the logging device can work in a high-pressure environment. Third, the pressure-holding device enables precise control of the pressure reduction process, allowing for a pressure reduction duration of up to 15 days. During the slow pressure reduction, the compressed state of the insulation and sealing components gradually recovers, avoiding phenomena such as rubber peeling and cracking caused by rapid pressure release, effectively protecting the testing instruments.

[0023] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a conventional well logging device. Figure 2 This is a flowchart of a downhole testing method under pressure-maintaining conditions during the CO2 storage stage, according to the present invention. Figure 3 This is a front view of the installation of the test pressure holding system device of the present invention; Figure 4 This is an installation side view of the test pressure holding system device of the present invention; Figure 5 This is a front view of the pressure-resistant cylinder and circuit system of the present invention; Figure 6 This is a cross-sectional view A-A' of the pressure-resistant cylinder and circuit system of the present invention; Figure 7 This is a side view of the pressure-resistant cylinder and circuit system of the present invention; Figure 8 This is a schematic diagram of the synchronous conductor shaft structure of the present invention; Figure 9 This is a cross-sectional view of the cable structure of the present invention; Figure 10 This is a schematic diagram of the force analysis of the cable guide block of the present invention; Figure 11 This is a schematic diagram of the cable auxiliary power structure of the present invention; Figure 12 This is a schematic diagram of the isolation tube structure of the present invention. Detailed Implementation

[0025] The following will be described with reference to the accompanying drawings and more specifically to the embodiments of the present invention. Figures 3-12 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] In the following description, the terms “upward” and “downward”, “above” and “below”, “above” and “below”, “right” and “left” and other similar terms indicating relative positions above or below a given point or element are used to more clearly illustrate some embodiments of the invention, wherein the same elements may be represented by the same reference numerals for consistency.

[0027] To address the shortcomings of existing technologies, this invention discloses a downhole testing method under pressure-maintaining conditions during the CO2 burial stage. The testing method specifically includes the following steps: Install the aforementioned test pressure holding system device; Perform a pre-pressurization process within the test pressure holding system device; Based on the logging tool, a test process is performed on the test pressure holding system device that has undergone pre-pressurization, and the test surface instrument works; both the logging tool and the test surface instrument are detachably connected to the test pressure holding system device. An internal pressure reduction process is performed on the test pressure holding system device that has already undergone testing. The pressure holding system device that has undergone the pressure reduction process is disassembled.

[0028] The following is a detailed explanation of the working process using the CO2 storage stage as an example of downhole testing. The testing conditions for the storage well are as follows: well depth 2000m, bottom hole temperature 60℃, wellhead pressure 10MPa, and bottom hole pressure 15MPa.

[0029] Specifically, the principle of downhole testing during the CO2 storage phase is as follows: During the initial stage of CO2 storage, CO2 is continuously injected into the well, causing the formation and wellbore pressure to continuously increase. At the designed maximum storage pressure (wellhead pressure of Pin-s), the well enters the storage state. Whether during the injection process or the storage state, it is necessary to monitor the gas state and formation rock properties downhole and in the formation to ensure safe storage. Therefore, a high-pressure environment is a fundamental condition for testing.

[0030] Furthermore, this method involves installing a test pressure holding system at the top of the wellhead device, using an isolation pipe to connect and isolate the wellbore environment from the test device environment, thus maintaining the stability of the wellbore environment during testing or storage.

[0031] Furthermore, the logging line system needs to be installed inside the device. Due to the large size of the line system, the overall size and shape of the device are one of the design challenges. Achieving signal transmission both inside and outside the high-pressure environment is another design challenge, and both challenges need to be addressed simultaneously.

[0032] To address the first challenge, the design difficulty of power-assisted cable routing was solved, enabling long-axial cable routing over short distances. Building upon this, the pressure-holding device was designed with a long cylindrical structure, significantly improving pressure resistance within the same volume.

[0033] To address the second challenge, a synchronous rotation signal transmission method was adopted to achieve unimpeded signal transmission inside and outside the device in a high-voltage environment, ensuring the normal conduct of testing.

[0034] Specifically, the preparatory work before installing the pressure holding system device: Based on the well conditions and testing requirements, the device was selected. Basic parameters are as follows: Pressure cylinder outer diameter 40cm, inner diameter 34cm, total length 250cm. Drum length 200cm, outer diameter 26cm, inner shaft outer diameter 5cm. Isolation pipe total length 4m. Cable outer diameter 1cm, wire rope outer diameter 5mm. The total weight of the device is approximately 2 tons, and the working pressure is 20MPa.

[0035] Next, the installation and testing of the pressure holding system will begin: First, install the isolation pipe above the wellhead device, close the isolation valve, and open the upper plug.

[0036] Next, install the relevant accessories inside the pressure-resistant cylinder, connect the power supply line, and test whether the wiring is properly arranged. After the test is normal, leave a 2m gap for the cable connector in the well.

[0037] Furthermore, the vehicle-mounted system places the platform at a suitable location at the wellhead, with the platform supporting the overall weight of the device. The cable lowering connector is pre-inserted into the isolation pipe flange, and then the pressure-resistant sleeve (cable connector) is connected to the isolation pipe flange. Before connection, it is confirmed that the cable is in the relevant guide wheel groove.

[0038] Next, install the logging tool. Pull the cable downhole connector from above the isolation pipe, pass it through the suspension block, and connect it to the logging tool. Slowly lower the suspension block and logging tool into the isolation pipe. Once the suspension block is stable inside the isolation pipe, slowly tighten the cable and allow the logging tool to suspend naturally inside the isolation pipe. Tighten the plug at the top of the isolation pipe to complete the installation.

[0039] Specifically, the pre-pressurization process within the pressure holding system device is as follows: Nitrogen (N2) is injected at constant pressure through the isolation pipe injection port until the pressure reaches the wellhead pressure of 10 MPa, with a pressurization time of no less than 2 hours. After 1 hour of stable observation, if the pressure gauge shows no change, it indicates that the overall device has good sealing performance.

[0040] Specifically, the testing process for the pressure holding system device is as follows: First, slowly open the main valve of the wellhead device and the valve on the topmost tubing in sequence.

[0041] Next, slowly open the isolation valve on the isolation pipe, and only proceed with the next step after the pressure gauge has stabilized.

[0042] Next, the logging tool is lowered to begin testing, recording, and transmitting data, testing the operation of the surface instruments. The logging tool's descent speed should not exceed 1 m / min, and other operational precautions are the same as for conventional logging operations.

[0043] Furthermore, after the logging tool reaches the bottom of the well, it remains stationary for one hour before entering the upward movement phase. During this phase, data is tested, recorded, and transmitted, and the continuous operation of the surface instruments is tested. The upward speed of the logging tool should not exceed 1 m / min.

[0044] Furthermore, once the logging tool is raised into the isolation tube, the testing operation is completed, and the test surface instruments are shut down. The isolation valve is then closed, maintaining the gas pressure (10 MPa) within the isolation tube and pressure tank. Afterward, the valves on the top tubing of the wellhead assembly and the main valve are closed sequentially.

[0045] Specifically, the internal pressure reduction process of the pressure holding system device is as follows: First, nitrogen gas (10MPa) is injected at equal pressure through the injection port of the isolation tube, while the pressure relief port is opened. This process is maintained at equal pressure for 10 to 30 minutes to ensure that most of the CO2 gas in the isolation tube is replaced by N2.

[0046] Furthermore, after closing the injection port and the depressurization port, the connection between the bottom of the isolation pipe and the wellhead device can be opened, and the vehicle-mounted system can retract the entire device into the vehicle or transport it to the storage room.

[0047] Furthermore, the device is left to stand for 1 to 2 days, allowing the CO2 that has penetrated into components such as cable insulation and logging instruments to be released and exchanged due to concentration differences.

[0048] Next, open the pressure relief port and control the pressure relief rate. When the pressure is greater than 5 MPa, relieve pressure at a rate of 1 MPa / day; then relieve pressure at a rate of 2 MPa / day until pressure relief is complete.

[0049] Specifically, the disassembly process for the pressure holding system device is as follows: The disassembly process mainly involves removing the logging instrument, disassembling the isolation tube and pressure-resistant cylinder, and organizing them for future logging applications.

[0050] On the other hand, this invention discloses a downhole testing device for CO2 storage under pressure-maintaining conditions. The testing device specifically includes: a pressure-maintaining testing system, a logging instrument, and surface testing instruments; wherein... The logging instrument is suspended on the test pressure holding system device, and the test surface instrument is connected to the test pressure holding system device and the logging instrument. The test pressure holding system device is used to perform a pre-pressurization process, or to perform a depressurization process within the test pressure holding system device that has already undergone the test process; The logging instrument is used to perform a test process on the test pressure holding system device that has undergone the pre-pressurization process.

[0051] The ground-based test instrument is used to receive, record, and transmit data.

[0052] Furthermore, the following explanation will be based on a test pressure holding system device used for downhole testing during the CO2 storage stage: Specifically, the pressure holding system device comprises a pressure-resistant cylinder, a wiring system, an isolation pipe, and a vehicle-mounted platform. The pressure-resistant cylinder is connected to the flange of the isolation pipe, and the wiring system is detachably connected to the vehicle-mounted platform. The wiring system is located inside the pressure-resistant cylinder and is detachably connected to the pressure-resistant cylinder.

[0053] See attached diagram for device installation. Figures 3-4 These are, respectively, the front view and side view of the installation of the test pressure holding system device of the present invention, as shown below. Figure 3 As shown, the test pressure holding system device includes a pressure-resistant cylinder, a wiring system, an isolation tube, and a vehicle-mounted platform. The wiring system is located inside the pressure-resistant cylinder, the vehicle-mounted platform is located below and connected to the pressure-resistant cylinder, and the wiring system and pressure-resistant cylinder are located above and connected to the isolation tube. The testing tool is suspended inside the sleeve and used to perform the test process on the pre-pressurized test pressure holding system device. Figure 4 As shown, the testing process of the testing tool is performed by opening and closing the valves on the isolation pipe. The ground test instrument is detachably connected to the pressure tank for receiving, recording, and transmitting data. The vehicle-mounted platform provides support for the entire device.

[0054] Specifically, the pressure-resistant cylinder is made of steel and its function is to form a sealed, pressure-resistant space to stabilize the wiring system. See Appendix. Figures 5-7 These are the front view, cross-sectional view A-A', and side view of the pressure-resistant cylinder and the circuit system of the present invention, respectively. After the pressure-resistant cylinder forms a passage with the well, it ensures that there is no gas leakage.

[0055] Furthermore, such as Figure 5 As shown, the pressure-resistant cylinder consists of two end caps and a pressure-resistant cylinder body. The two end caps are connected to the pressure-resistant cylinder body by flanges. Each end cap has a sealing through hole in the center; one side mates with the synchronous conductor shaft, and the other side mates with the line connection plate, ensuring pressure resistance while leading signal and power lines out of the pressure-resistant cylinder.

[0056] Furthermore, the pressure-resistant cylinder also has a number of fixing plates inside, used to fix the guide rails, motors, gear sets, guide wheels, and rollers of the wiring system.

[0057] likeFigure 6 As shown, the cable is wound around the inner shaft of the drum and passes through the sealing through hole on the pressure-resistant cylinder end cover along the tangential direction of the upper right and lower left guide wheels, respectively.

[0058] like Figure 7 As shown, the pressure-resistant cylinder is also equipped with a cable routing interface. To ensure effective cable routing, the interface is designed with a flat structure. The interface also features multiple cable guide wheels to prevent the cable from scratching the wall surface.

[0059] Specifically, the line system includes winch devices and cables.

[0060] Furthermore, the winch device operates on the same principle as a conventional winch device. Taking the DJ3056 logging 3000-meter cable winch as an example, the principle of a conventional winch device will be explained: Specifically, the DJ3056 3000-meter logging cable winch is a specialized piece of equipment used for geophysical exploration and geological surveys. It is primarily used in conjunction with the JHQ-2D integrated digital logging equipment, but can also be used with other logging equipment. The equipment utilizes variable frequency motors, DC motors, and AC asynchronous motors as power sources, featuring a wide speed range, smooth speed changes, convenient operation, and simple maintenance. It can be used in geophysical exploration and geological surveys in high-altitude (≤5500 meters), onshore, and offshore environments. It includes a depth measuring wheel for automatic depth recording.

[0061] Furthermore, in order to adapt to the pressure resistance characteristics, the layout design and special functional design are carried out, specifically including the following parts: Conventional winch devices use conductive slip rings to transmit electrical signals. Due to space limitations, this invention develops a synchronous conductor shaft, which not only performs the conductive function of a slip ring but also functions as a drum bearing. The synchronous conductor shaft is a key design feature for signal transmission in high-voltage environments.

[0062] A schematic diagram of the synchronous conductor shaft structure of the present invention is attached. Figure 8 This includes components such as the main bearing, sealed shaft, single-pole signal line, insulation layer, conductive bearing, rotating tube, synchronous spring, and roller. For example... Figure 8 As shown, the sealing shaft at the end of the synchronous conductor shaft mates with the sealing hole of the end cap on one side of the pressure-resistant cylinder to form a pressure-resistant seal. The shaft does not rotate and serves to support the roller. A unipolar signal line is installed inside the shaft, which is insulated from the shaft and provides a pressure-resistant seal. The other end of the shaft has an insulating coating and is fitted with two separate conductive bearings.

[0063] Furthermore, the bottom retaining ring of the conductive bearing is connected to the unipolar signal line, and the rotating ring at the other end is connected to the unipolar signal line of the cable. The rotating ring is connected to a spring, the other end of which is fixed to the inner wall of the rotating tube. When the rotating tube rotates, the traction spring causes the rotating ring of the conductive bearing to rotate, transmitting the signal from the rotating cable to the stationary shaft.

[0064] Furthermore, a main bearing is installed on the shaft, which is connected to the rotating tube and drives the drum to rotate synchronously.

[0065] Appendix Figure 9 A cross-sectional view of the cable structure of the present invention is shown below. Figure 9 As shown, the cable includes a steel wire rope, signal lines, an inner insulating filling space, a shielding layer, and an outer insulating layer. The steel wire rope is at the center of the cable and serves as the load-bearing element. Outside the steel wire rope are two signal lines, and further outside is the shielding layer. These three types of cables are kept separate, and the interior is filled with insulating and CO2-corrosion-resistant material. The entire cable is encased in an outer insulating layer made of insulating, CO2-corrosion-resistant, and wear-resistant material.

[0066] The cable routing system differs significantly from that of conventional winches. The long, pressure-resistant cylinder dictates that the drum be designed with a long shaft and a small radius. In conventional winches, cable routing is powered by rollers; cable guidance requires no additional power. Figure 10 This is a force analysis diagram of the cable guide block. (For example...) Figure 10 As shown, when the distance between the cable guide block and the roller is large, that is, S is large. If the length L of the roller remains unchanged, the larger S is, the smaller the angle α between the center of the guide block and the edge of the roller (A or B), and the smaller the resistance of the cable movement to the guide block. Here, S is the vertical distance between the lower edge of the roller and the upper edge of the cable guide block, and L is the straight-line distance between the two ends A and B perpendicular to S.

[0067] Furthermore, please refer to the attached diagram for the schematic diagram of the auxiliary power design structure of the cabling. Figure 11 The system includes components such as cables, cable guide blocks, bearings, guide rails, fixing plates, cable gear sets, gear sets, and motors. The guide rails are fixed to the walls of the pressure-resistant cylinder at both ends via the fixing plate inside the cylinder. The cable guide blocks can move linearly along the guide rails. When the motor starts, it provides power to the gear sets. The gear sets pass through the bearings, and their two ends are connected to the motor and the cable gear set, respectively. One end of the cable is connected to the cable guide block, and the other end passes through a sealed through-hole in the center of the end cap on one side of the pressure-resistant cylinder and connects to the synchronous guide shaft.

[0068] Because the cable routing device of this invention is a long-shaft type, i.e., S is short and L is long, the cable routing guide block experiences significant resistance from the cable movement. Therefore, by utilizing the component force of the gear set, the cable routing gear set obtains auxiliary power to drive the cable routing guide block, causing the cables to be tightly arranged along the roller. The isolation pipe is the connecting component between the wellhead device and the pressure-resistant cylinder. See the attached diagram for its structural schematic. Figure 12 .like Figure 12As shown, the isolation pipe consists of a pressure-resistant pipe, isolation valve, suspension block, connecting flange, plug, connecting joint, and functional interface. Because the isolation pipe needs to accommodate the logging instrument, its length is between 3 and 5 meters. On the upper left side of the pressure-resistant pipe wall, from top to bottom, are the pressure testing port and the injection port. On the lower right side of the pressure-resistant pipe wall, from top to bottom, are the gas concentration measurement port and the pressure relief port. The cable run-in connector connects to the testing instrument through the suspension block from inside the isolation pipe flange to perform the testing process.

[0069] Specifically, during operation, the isolation valve opens, maintaining the same gas pressure in the isolation tube and the pressure-resistant cylinder. The logging tool enters the underground tubing through the isolation valve to conduct testing. Monitoring is performed via the pressure measurement port and gas concentration measurement port in the functional interface.

[0070] After the test is completed, the logging tool is raised into the isolation tube, and then the isolation valve is closed. The gas in the isolation tube and the pressure tank continues to be under high pressure. By controlling the pressure drop rate, the pressure is usually released within 2 to 15 days. The slow pressure drop rate protects the cable insulation material and the logging tool insulation material from damage caused by CO2 pressure drop.

[0071] During the depressurization process, the isolation pipe connection can be disassembled, and the isolation pipe and pressure-resistant cylinder can be moved into the test vehicle as a whole, or placed in the storage room.

[0072] The vehicle-mounted platform is an engineering vehicle platform. Ground testing instruments, pressure-resistant cylinders, and wiring systems are all housed on the platform. When not in use, the retrieved testing tools are also placed on the platform. When measurements are required at different well locations, the vehicle-mounted platform simply moves the instruments to the appropriate location.

[0073] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A downhole testing method for CO2 storage under pressure-maintaining conditions, characterized in that, The testing method includes: Perform a pre-pressurization process within the test pressure holding system device; Based on the logging tool, a test process is performed on the test pressure holding system device that has undergone pre-pressurization, and the test surface instrument works; both the logging tool and the test surface instrument are detachably connected to the test pressure holding system device. The test process for the pre-pressurized test holding system device includes the following steps: The logging tool is lowered to the bottom of the well. During the descent, data is tested, recorded, and transmitted to test the operation of the surface instruments. The logging tool is pulled up, and during the upward movement, data is continuously tested, recorded, and transmitted to test the operation of the surface instruments. Raise the logging instrument into the isolation pipe to complete the testing work, and shut down the test surface instruments. A pressure reduction process is performed within the test pressure holding system that has already undergone testing. The pressure reduction process performed within the test pressure holding system device that has already undergone testing includes the following steps: Inject inert protective gas into the isolation pipe injection port and open the pressure relief port; Close the injection port and the pressure relief port, and open the connection between the bottom of the isolation pipe and the wellhead device; Open the pressure relief port and control the pressure relief speed until the pressure relief is complete.

2. The test method according to claim 1, characterized in that, The specific steps for performing the pre-pressurization process within the test pressure holding system device are as follows: Protective gas is injected at equal pressure through the injection port of the isolation pipe until the pressure inside the isolation pipe is equal to the pressure at the wellhead.

3. The test method according to claim 1, characterized in that, The testing method also includes: Install the aforementioned test pressure holding system device; The pressure holding system device that has undergone the pressure reduction process is disassembled.

4. The test method according to claim 3, characterized in that, The specific steps for installing the test pressure holding system device are as follows: Determine the installation location of the isolation pipe at the wellhead, close the isolation valve, and open the plug; Install the relevant accessories inside the pressure-resistant cylinder, connect the power supply line, reserve the length of the cable lowering connector, and connect the cable routing interface of the pressure-resistant cylinder to the flange of the isolation pipe; Determine the installation location of the vehicle-mounted platform at the wellhead, and pre-insert the cable lowering connector into the isolation pipe flange; Pull the cable downhole connector out of the isolation pipe, pass it through the suspension block, and connect it to the logging instrument; Tighten the plug at the top of the isolation tube to complete the installation of the test pressure holding system device.

5. The test method according to claim 3 or 4, characterized in that, Before installing the test pressure holding system, it is also necessary to select a device that meets the basic parameters, as follows: Determine the outer diameter, inner diameter, and total length of the pressure-resistant cylinder; determine the length, outer diameter, and inner shaft outer diameter of the drum; determine the total length of the isolation tube; and determine the outer diameter of the cable and the outer diameter of the wire rope.

6. The test method according to claim 3, characterized in that, The disassembly process includes: removing the logging instrument and separating the isolation tube and pressure cylinder.

7. A downhole testing device for CO2 storage under pressure-maintaining conditions, characterized in that, The testing apparatus includes: a pressure-holding system, a logging instrument, and surface testing instruments; wherein... The logging instrument is suspended on the test pressure holding system device, and both the logging instrument and the test surface instrument are detachably connected to the test pressure holding system device. The test pressure holding system device is used to perform a pre-pressurization process, or to perform a depressurization process within the test pressure holding system device that has already undergone the test process; The pressure reduction process performed within the test pressure holding system device that has already undergone testing includes the following steps: Inject inert protective gas into the isolation pipe injection port and open the pressure relief port; Close the injection port and the pressure relief port, and open the connection between the bottom of the isolation pipe and the wellhead device; Open the pressure relief port and control the pressure relief speed until pressure relief is complete; The logging instrument is used to perform a test process on the test pressure holding system device that has undergone a pre-pressurization process; The test process for the pre-pressurized test holding system device includes the following steps: The logging tool is lowered to the bottom of the well. During the descent, data is tested, recorded, and transmitted to test the operation of the surface instruments. The logging tool is pulled up, and during the upward movement, data is continuously tested, recorded, and transmitted to test the operation of the surface instruments. Raise the logging instrument into the isolation pipe to complete the testing work, and shut down the test surface instruments. The ground-based test instrument is used to receive, record, and transmit data.

8. The testing apparatus according to claim 7, characterized in that, The test pressure holding system includes: a pressure-resistant cylinder, a wiring system, an isolation pipe, and a vehicle-mounted platform, wherein, The pressure-resistant cylinder is connected to the isolation pipe flange, and the wiring system is detachably connected to the vehicle platform. The wiring system is located inside the pressure-resistant cylinder and is detachably connected to the pressure-resistant cylinder.

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