A kind of pressure-maintaining core cross plate shear device and shear strength test method

Abstract

The application discloses a kind of pressure-maintaining core cross plate shear device and shear strength test method, device includes sample pressure-maintaining system, test system, control system, data acquisition system;Sample pressure-maintaining system is guaranteed by ball valve to ensure the pressure state, reach the purpose of pressure-maintaining stable before and after testing, test system carries out shear test to test sample shear strength by cross plate, control system realizes the extension and contraction of telescopic rod and the work of torque applicator, ensure that cross plate enters sample and carries out work, data acquisition system is in real time by torque sensor, HX711 module, single-chip microcomputer, RS485 communication serial port acquisition, transport and process data, and save in PC end.The application can carry out the pressure-maintaining core shear test device of testing on ship.It has strong guiding function to study submarine landslide generation mechanism, realize the safe exploitation of flammable ice and ensure the safety of submarine engineering construction.

Description

Technical Field

[0001] This invention belongs to the technical field of shear strength testing of pressure-holding core samples of natural gas hydrates, and in particular relates to a pressure-holding core vane shearing device and method. Background Technology

[0002] Natural gas hydrates are ice-cage-like compounds formed from natural gas and water under high pressure and low temperature conditions, and are widely distributed in near-shore continental slope environments. Exploration and development of natural gas hydrates may cause engineering disasters such as submarine landslides, wellbore collapses, and damage to engineering structures. Research indicates that the development of natural gas hydrate resources, disaster prevention and control, and environmental assessment all rely on a fundamental scientific problem in geotechnical engineering: how to accurately determine the mechanical characteristic parameters of hydrate storage to ensure the long-term stability of hydrate reservoirs. Shear strength testing is an indispensable step in this process.

[0003] Currently, due to both technological and cost limitations, fundamental research on reservoir mechanical properties still primarily relies on artificially prepared natural gas hydrate core samples from laboratory settings. It is difficult to ascertain the extent to which the data, conclusions, and understandings obtained from this approach differ from actual field reservoir conditions. Furthermore, while existing pressure-holding sampling and transfer techniques for seabed sediments are relatively mature, subsequent pressure-holding testing and analysis techniques are still in their infancy, and domestic pressure-holding testing technology is severely lacking. Pressure-holding testing refers to transferring minimally disturbed sediment samples to a laboratory under in-situ pressure conditions for further analysis and testing. Therefore, there is an urgent need for a pressure-holding core vane shearing device and its method to quantify the differences between the two approaches. Summary of the Invention

[0004] The purpose of this invention is to provide a pressure-holding core vane shearing device and method, which is suitable for testing the shear strength of pressure-holding cores of natural gas hydrates.

[0005] This invention provides a pressure-holding core vane shearing device, which includes a sample pressure-holding system, a testing system, a control system, and a data acquisition system;

[0006] The sample pressure holding system includes a pressure holding cylinder, a test hole, a test tube, a ball valve, a first connector, a pushing device, a first pressure maintainer, and a second pressure maintainer. The test tube is vertically arranged on the side of the pressure holding cylinder and is connected to the pressure holding cylinder through the test hole. The ball valve is arranged in the middle of the test tube. The first connector is arranged at the end of the test tube away from the pressure holding cylinder. The pushing device is arranged at one end of the pressure holding cylinder to control the forward movement of the sample inside the pressure holding cylinder. The first pressure maintainer is arranged at the other end of the pressure holding cylinder to adjust the pressure inside the pressure holding cylinder. The second pressure maintainer is arranged at the end of the test tube near the first connector to ensure that the pressure at both ends of the ball valve is consistent.

[0007] The testing system includes an instrument tube and a cross plate. The instrument tube is connected to the test tube via a first connector. The cross plate is arranged inside the instrument tube and connected to one end of the first connector. The cross plate is connected to one end of the torque sensor of the data acquisition system via a second connector.

[0008] The control system includes a telescopic rod, a torque applicator, a motor, and a PC. One end of the telescopic rod is connected to the other end of the torque sensor via a third connector. The motor is connected to the PC via a wire. The telescopic rod is arranged inside the instrument tube. The torque applicator is arranged between the telescopic rod and the motor. The torque applicator can control the rotation of the telescopic rod to apply torque. The motor can control the extension and retraction of the telescopic rod.

[0009] The data acquisition system includes a torque sensor, an HX711 module, a microcontroller, and an RS485 communication serial port. The signal from the torque sensor is transmitted to the HX711 module via a wire passing through a through hole in the third connector. The HX711 module is connected to the microcontroller via a wire, the microcontroller is connected to the RS485 communication serial port via a wire, and the RS485 communication serial port is connected to a PC via a wire.

[0010] According to a preferred embodiment of the present invention, the ball valve is closed before the vane is displaced to ensure that the sample is in a pressure-holding state, and the ball valve is opened after the vane begins to displace to ensure that the vane passes smoothly through into the sample.

[0011] According to a preferred embodiment of the present invention, the through hole is designed to be sealed to ensure that the sample is always under pressure during the test.

[0012] According to a preferred embodiment of the present invention, the instrument tube and the test tube are detachably connected by a first connector. The first connector is a flange structure, and the inner diameter of the first connector is the same as the inner diameter of the instrument tube. The sealing surface is a tongue and groove surface to ensure normal connection and sealing function under high pressure.

[0013] According to a preferred embodiment of the present invention, the cross plate and the torque sensor are detachably connected via a second connector. The second connector is a flange structure and is located inside the instrument tube. Its outer diameter is 0.8 times the inner diameter of the instrument tube. The sealing surface is a tongue and groove surface to ensure normal connection and sealing function under high pressure.

[0014] According to a preferred embodiment of the present invention, the torque sensor is detachably connected to the telescopic rod via a third connector. The third connector is a flange structure and is located inside the instrument tube. Its outer diameter is 0.8 times the inner diameter of the instrument tube. The sealing surface is a tongue and groove surface to ensure normal connection and sealing function under high pressure.

[0015] According to a preferred embodiment of the present invention, the motor only controls the extension and retraction of the telescopic rod, while the rotation of the telescopic rod is controlled separately by a torque applicator.

[0016] According to a preferred embodiment of the present invention, the torque sensor is connected to the HX711 module to convert the torque magnitude into an electrical signal and transmit it to the microcontroller. After receiving the electrical signal, the microcontroller runs preset code to calculate the voltage value, torque magnitude, and shear strength value. The RS485 communication serial port transmits the calculation results to the PC for storage.

[0017] The present invention also provides a method for testing the shear strength of natural gas hydrate pressurized core samples based on the above-mentioned experimental apparatus, which includes the following steps:

[0018] a. Connect the data acquisition system, testing system, and control system;

[0019] b. Place the pressure-holding cylinder flat on a horizontal platform;

[0020] c. Close the ball valve, open the first pressure maintainer and the second pressure maintainer, pressurize the pressure inside the pressure holding cylinder to the preset value, and keep the pressure at both ends of the ball valve consistent.

[0021] d. Open the ball valve, start the data acquisition and control system, and prepare to carry out the vane shear test;

[0022] e. Start the motor and control the telescopic rod to pass the cross plate through the first connector and the ball valve in sequence, and push it into the pressure holding cylinder until it is inserted into the sample to the preset depth;

[0023] f. Control the torque applicator to apply torque evenly at a certain speed until the cross plate twists 90° or 180°, at which point the shearing is completed;

[0024] g. Record the cross-plate shearing process and the data after shearing is completed in real time through a data acquisition system;

[0025] h. Start the motor and control the telescopic rod to pull the cross plate out of the pressure holding cylinder. At this point, the shear test at one location of the sample is completed.

[0026] i. Start the pushing device and push the sample forward a preset distance. Repeat steps e, f, g, and h until the natural gas hydrate pressure-maintaining core shear strength test is completed.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention relates to a pressure-maintaining core vane shearing device for natural gas hydrate reservoirs. The pressure-maintaining system is used to maintain the natural gas hydrate reservoir under high pressure at the seabed, ensuring the reliability of vane shear strength test results for natural gas hydrate resource extraction. The vane shearing test system can be used to conduct tests by connecting the test hole to the pressure-maintaining and heat-insulating cylinder. This design allows sample testing to be carried out on board, greatly reducing the cost of transporting samples to onshore laboratories. Furthermore, the device uses a transmission method to measure torque. A torque sensor converts the strain generated by the torque into a voltage change signal, which is transmitted to a microcontroller. The microcontroller then performs a series of calculations using preset code to obtain the voltage value, torque magnitude, and shear strength value. Finally, the test data is transmitted to a PC for storage.

[0029] This invention provides a pressure-holding core shear testing device that can be used for testing on board a ship. This overcomes the problem of existing technologies requiring samples to be transported ashore for testing. This invention eliminates the cost of pressure-holding transportation and avoids significant disturbances during transport, ensuring testing accuracy. It has strong guiding significance for studying the mechanism of submarine landslides, achieving safe mining of combustible ice, and ensuring the safety of submarine engineering construction. Attached Figure Description

[0030] Figure 1 This is an overall structural diagram of the invention;

[0031] Figure 2 This is a detailed internal view of the instrument tube of the present invention;

[0032] Figure 3 This is a connection diagram of the testing system, control system, and data acquisition system of this invention;

[0033] Explanation of markings in the diagram:

[0034] 1—Pressure holding cylinder; 2—Test hole; 3—Test tube; 4—Ball valve; 5—Connector;

[0035] 6—Instrument tube; 7—Cross plate; 8—Torque sensor; 9—Telescopic rod;

[0036] 10—Torque applicator; 11—Motor; 12—Wire; 13—Wire hole;

[0037] 14—HX711 module; 15—Microcontroller; 16—RS485 communication serial port; 17—PC terminal;

[0038] 18—Pushing device; 19—First pressure maintainer; 20—Second pressure maintainer. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments described below are intended to facilitate understanding of the present invention and are not intended to limit it in any way.

[0040] This embodiment specifically discloses a pressure-holding core vane shearing device, which includes a sample pressure-holding system, a testing system, a control system, and a data acquisition system.

[0041] The sample pressure holding system includes a pressure holding cylinder 1, a test hole 2, a test tube 3, a ball valve 4, a first connector, a pushing device 18, a first pressure maintainer 19, and a second pressure maintainer 20. The test tube 3 is vertically arranged on the side of the pressure holding cylinder 1 and is connected to the pressure holding cylinder 1 through the test hole 2. The ball valve 4 is arranged in the middle of the test tube 3. The first connector is arranged at the end of the test tube 3 away from the pressure holding cylinder. The pushing device 18 is arranged at one end of the pressure holding cylinder 1 to control the forward movement of the sample inside the pressure holding cylinder 1. The first pressure maintainer 19 is arranged at the other end of the pressure holding cylinder 1 to adjust the pressure inside the pressure holding cylinder. The second pressure maintainer 20 is arranged inside the test tube 3 near the first connector to ensure that the pressure at both ends of the ball valve is consistent.

[0042] The testing system includes an instrument tube 6 and a cross plate 7. The instrument tube 6 is connected to the test tube 3 through a first connector. The cross plate 7 is arranged inside the instrument tube 6 and connected to one end of the first connector. The cross plate 7 is connected to one end of the torque sensor 8 of the data acquisition system through a second connector.

[0043] The control system includes a telescopic rod 9, a torque applicator 10, a motor 11, and a PC terminal 17. One end of the telescopic rod 9 is connected to the other end of the torque sensor 8 via a third connector. The motor 11 is connected to the PC terminal 17 via a wire 12. The telescopic rod 9 is arranged inside the instrument tube 6. The torque applicator 10 is arranged between the telescopic rod 9 and the motor 11. The torque applicator 10 can control the rotation of the telescopic rod to apply torque. The motor 11 can control the extension and retraction of the telescopic rod.

[0044] The data acquisition system includes a torque sensor 8, an HX711 module 14, a microcontroller 15, and an RS485 communication serial port 16. The signal from the torque sensor 8 is transmitted to the HX711 module 14 via a wire 12 through a through hole 13 on the third connector. The HX711 module 14 is connected to the microcontroller 15 via the wire 12. The microcontroller 15 is connected to the RS485 communication serial port 16 via the wire 12. The RS485 communication serial port 16 is connected to a PC terminal 17 via the wire 12.

[0045] According to a preferred embodiment of the present invention, the instrument tube and the test tube are detachably connected via a first connector. The first connector is a flange structure, and its inner diameter is the same as that of the instrument tube. The sealing surface is a tongue and groove surface to ensure normal connection and sealing under high pressure. According to a preferred embodiment of the present invention, the cross plate and the torque sensor are detachably connected via a second connector. The second connector is a flange structure, located inside the instrument tube, and its outer diameter is 0.8 times the inner diameter of the instrument tube. The sealing surface is a tongue and groove surface to ensure normal connection and sealing under high pressure. According to a preferred embodiment of the present invention, the torque sensor is detachably connected to the telescopic rod via a third connector. The third connector is a flange structure, located inside the instrument tube, and its outer diameter is 0.8 times the inner diameter of the instrument tube. The sealing surface is a tongue and groove surface to ensure normal connection and sealing under high pressure.

[0046] In this embodiment, the motor only controls the extension and retraction of the telescopic rod; the rotation of the telescopic rod is controlled separately by the torque applicator. The torque sensor is connected to the HX711 module, converting the torque magnitude into an electrical signal and sending it to the microcontroller. After receiving the electrical signal, the microcontroller runs preset code to calculate the voltage value, torque magnitude, and shear strength value. The RS485 communication serial port transmits the calculation results to the PC for storage.

[0047] In a specific embodiment of this invention, the through-hole is designed to be sealed, ensuring that the sample remains under pressure throughout the test. Before the cross-plate moves, the ball valve is closed to maintain sample pressure; after the cross-plate begins to move, the ball valve opens to allow the cross-plate to pass smoothly into the sample. Figure 1 As shown, in a specific embodiment of the present invention, the ball valve 4 remains closed before the cross plate 7 enters the sample, ensuring that the sample is under pressure. The connector 5 is a sealed connection, ensuring that the sample remains under pressure throughout the test. The instrument tube 6 is detachably connected to the test tube 3 via the connector 5.

[0048] like Figure 2 As shown, in a specific embodiment of the present invention, the cross plate 7 is detachably connected to the torque sensor 8 via connector 5. The torque sensor 8 is detachably connected to the telescopic rod 9 via connector 5. The motor 11 controls the extension and retraction of the telescopic rod 9 and the torque application of the torque applicator 10. The wire 12 connects the motor 11 to the PC terminal 17 to control the operation of the motor 11.

[0049] When using, first connect the data acquisition system, testing system, and control system; place the pressure holding cylinder flat on a horizontal platform; close the ball valve, open the first pressure maintainer and the second pressure maintainer, pressurize the pressure inside the pressure holding cylinder to the preset value, and keep the pressure at both ends of the ball valve consistent.

[0050] Then, open the ball valve, activate the data acquisition and control system, and prepare to conduct the vane shearing test; start the motor, control the telescopic rod to pass the vane through the first connector and the ball valve in sequence, and push it into the pressure holding cylinder until it is inserted into the sample to the preset depth; control the torque applicator to apply torque evenly at a certain speed until the vane twists 90° or 180°, at which point the shearing is completed; record the vane shearing process and the data after the shearing is completed in real time through the data acquisition system; start the motor, control the telescopic rod to pull the vane out of the pressure holding cylinder, at which point the shearing test at one location of the sample is completed;

[0051] After the single-location test is completed, the pushing device is activated to push the sample forward a preset distance. The testing steps are repeated until the pressure-maintained core shear strength test of natural gas hydrate is completed. The entire pressure-maintained core shear test process can be carried out on board the ship, which has a strong guiding role in studying the generation mechanism of submarine landslides, realizing the safe mining of combustible ice, and ensuring the safety of submarine engineering construction.

[0052] Matters not covered in this invention are common knowledge.

[0053] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for testing the shear strength of natural gas hydrate core samples under pressure using a core-holding vane shearing device, characterized in that, The pressure-holding core vane shearing device includes a sample pressure-holding system, a testing system, a control system, and a data acquisition system. The sample pressure holding system includes a pressure holding cylinder (1), a test hole (2), a test tube (3), a ball valve (4), a first connector, a pushing device (18), a first pressure maintainer (19), and a second pressure maintainer (20). The test tube (3) is arranged vertically on the side of the pressure holding cylinder (1) and is connected to the pressure holding cylinder (1) through the test hole (2). The ball valve (4) is arranged in the middle of the test tube (3). The first connector is arranged at the end of the test tube (3) away from the pressure holding cylinder. The pushing device (18) is arranged at one end of the pressure holding cylinder (1) to control the forward movement of the sample inside the pressure holding cylinder (1). The first pressure maintainer (19) is arranged at the other end of the pressure holding cylinder (1) to adjust the pressure inside the pressure holding cylinder. The second pressure maintainer (20) is arranged at the end of the test tube (3) close to the first connector to ensure that the pressure at both ends of the ball valve is consistent. The testing system includes an instrument tube (6) and a cross plate (7). The instrument tube (6) is connected to the test tube (3) through a first connector. The cross plate (7) is arranged inside the instrument tube (6) and connected to one end of the first connector. The cross plate (7) is connected to one end of the torque sensor (8) of the data acquisition system through a second connector. The instrument tube and the test tube are detachably connected through the first connector. The first connector is a flange structure, and the inner diameter of the first connector is the same as the inner diameter of the instrument tube. The sealing surface is a tongue and groove surface. The control system includes a telescopic rod (9), a torque applicator (10), a motor (11), and a PC terminal (17). One end of the telescopic rod (9) is connected to the other end of the torque sensor (8) via a third connector. The motor (11) is connected to the PC terminal (17) via a wire (12). The telescopic rod (9) is arranged inside the instrument tube (6). The torque applicator (10) is arranged between the telescopic rod (9) and the motor (11). The torque applicator (10) can control the rotation of the telescopic rod to apply torque. The motor (11) can control the extension and retraction of the telescopic rod. The data acquisition system includes a torque sensor (8), an HX711 module (14), a microcontroller (15), and an RS485 communication serial port (16). The signal from the torque sensor (8) is transmitted to the HX711 module (14) via a wire (12) through a through hole (13) on the third connector. The through hole is a sealed design. The HX711 module (14) is connected to the microcontroller (15) via a wire (12). The microcontroller (15) is connected to the RS485 communication serial port (16) via a wire (12). The RS485 communication serial port (16) is connected to the PC (17) via a wire (12). Before the cross plate moves, the ball valve is closed to ensure that the sample is under pressure. After the cross plate begins to move, the ball valve is opened to ensure that the cross plate passes smoothly into the sample. The method for testing the shear strength of pressure-retaining core samples of natural gas hydrates includes the following steps: a. Connect the data acquisition system, testing system, and control system; b. Place the pressure-holding cylinder flat on a horizontal platform; c. Close the ball valve, open the first pressure maintainer and the second pressure maintainer, pressurize the pressure inside the pressure holding cylinder to the preset value, and keep the pressure at both ends of the ball valve consistent. d. Open the ball valve, start the data acquisition and control system, and prepare to carry out the vane shear test; e. Start the motor and control the telescopic rod to pass the cross plate through the first connector and the ball valve in sequence, and push it into the pressure holding cylinder until it is inserted into the sample to the preset depth; f. Control the torque applicator to apply torque evenly at a certain speed until the cross plate twists 90° or 180°, at which point the shearing is completed; g. Record the cross-plate shearing process and the data after shearing is completed in real time through a data acquisition system; h. Start the motor and control the telescopic rod to pull the cross plate out of the pressure holding cylinder. At this point, the shear test at one location of the sample is completed. i. Start the pushing device and push the sample forward a preset distance. Repeat steps e, f, g, and h until the natural gas hydrate pressure-maintaining core shear strength test is completed.

2. The method for testing the shear strength of natural gas hydrate core samples using the pressure-holding core vane shearing device as described in claim 1, characterized in that: The cross plate and torque sensor are detachably connected via a second connector. The second connector is a flange structure and is located inside the instrument tube. Its outer diameter is 0.8 times the inner diameter of the instrument tube. The sealing surface is a tongue and groove surface to ensure normal connection and sealing under high pressure.

3. The method for testing the shear strength of natural gas hydrate core samples using the pressure-holding core vane shearing device as described in claim 1, characterized in that: The torque sensor is detachably connected to the telescopic rod via a third connector. The third connector is a flange structure and is located inside the instrument tube. Its outer diameter is 0.8 times the inner diameter of the instrument tube. The sealing surface is a tongue and groove surface to ensure normal connection and sealing under high pressure.

4. The method for testing the shear strength of natural gas hydrate core samples using the pressure-holding core vane shearing device as described in claim 1, characterized in that: The motor only controls the extension and retraction of the telescopic rod, while the rotation of the telescopic rod is controlled separately by the torque applicator.

5. The method for testing the shear strength of natural gas hydrate core samples using the pressure-holding core vane shearing device as described in claim 1, characterized in that: The torque sensor is connected to the HX711 module to convert the torque into an electrical signal and send it to the microcontroller. After receiving the electrical signal, the microcontroller runs preset code to calculate the voltage value, torque value, and shear strength value. The RS485 communication serial port sends the calculation results to the PC for storage.

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