Hydrate-containing sediment ring shear-electrical property combined test device and method

Abstract

According to the hydrate-containing sediment ring shear-electrical property combined test device and method, the successful experience of an existing three-axis shear combined test system is used for reference, a complex resistivity test and research method is introduced, an existing ring shear device is redesigned and improved, and an inner and outer box rotary shear mode is innovatively provided; according to the electrical auxiliary ring shear testing system, the requirements of failure characteristic testing under the large deformation condition of hydrate-containing sediments and deformation rule testing under the shear slip condition are met, the ring shear comprehensive testing system high in testing accuracy and diverse in monitoring means is formed, and the complex resistivity testing and the ring shear testing are combined to provide the electrical auxiliary ring shear testing system. The irregular electrode is introduced to test the complex resistivity, so that the hydrate saturation and the electrical property change rule of the sediment can be accurately reflected, and the problems of single test means and low test precision of the existing hydrate-containing sediment ring shear test device are solved in a targeted manner; and a new thought is provided for sea area natural gas hydrate area seabed slope stability evaluation and landslide mechanism analysis.

Description

Technical Field

[0001] The invention relates to the technical field of marine natural gas hydrate resource exploration and development engineering, and in particular to a device and method for jointly testing the ring shear and electrical characteristics of hydrate-containing sediments. Background Art

[0002] Accurate evaluation and prediction of mechanical parameters of hydrate-containing sediments is the basis and prerequisite for reservoir stability during research and development, and is also a necessary condition for the safe and efficient development of natural gas hydrates. The exploration and development of natural gas hydrates is closely related to engineering geological risks, such as wellbore instability, well leakage and blowout, sand production, formation subsidence, submarine landslides, etc. At present, researchers mainly obtain the strength parameters and deformation characteristics of hydrate-containing sediments through triaxial shear tests, but it is difficult to support subsequent research on submarine landslides in hydrate areas by exploring the behavior and destruction mechanism of hydrate sediments under large deformation conditions.

[0003] In order to study the failure characteristics under large deformation conditions and the deformation law under long-distance shear slip conditions, researchers proposed the ring shear test technology to explore the stability of formation slopes and landslide mechanisms. However, the above method cannot simulate the temperature and pressure environment of natural gas hydrate synthesis and decomposition and the influence of hydrate content on landslides, which limits the application of conventional ring shear tests in the hydrate field.

[0004] In response to the above problems, the Chinese invention patent with publication number CN114252351B announced a ring shear test device and method suitable for hydrate-containing sediments, and explained the difference between the ring shear test of hydrate-containing sediments and conventional soil tests. The Chinese invention patent application with publication number CN118746504A also proposed a ring shear test device and method for hydrate sediments, which provides an effective means for the mechanical properties of hydrate-containing sediments under large deformation. Both of the above methods use the upper and lower shear boxes to rotate in an offset manner for shearing, and the torsional loading friction is large, which affects the accuracy of the mechanical test of hydrate-containing sediments. There is a lack of effective monitoring means for the hydrate synthesis process in sediments, making it difficult to accurately determine the hydrate saturation. At the same time, a single testing method cannot effectively characterize the destruction process of hydrate-containing sediments, limiting subsequent research on the destruction mechanism.

[0005] At present, the combination of mechanical property testing of hydrate-containing sediments with acoustics and electricity has been initially carried out, especially in triaxial shear testing, and good results have been achieved. The Chinese invention patent with publication number CN103323352A introduces an experimental device and method for dynamic triaxial mechanical-acoustic-electrical synchronous testing of natural gas hydrate sediments, providing a feasible method for realizing mechanical-acoustic-electrical combined testing of hydrate-containing sediments. The Chinese invention patent with publication number CN108776071A combines the undrained shear strength test of hydrate-containing sediments with electrical resistance tomography, which can realize the analysis of the hydrate content in the sediment and the deformation of the sediment during shearing.

[0006] In summary, the current ring shear test device for hydrate-containing sediments has the following two shortcomings: (1) there is a lack of effective monitoring means for the synthesis process of natural gas hydrates in sediments, and it is impossible to evaluate the quality of sample preparation; (2) the detection means during the shear process are single, and there is a lack of effective parameters that can characterize the destruction process of hydrate-containing sediments. Summary of the invention

[0007] Based on the above technical problems, the present invention provides a ring shear-electrical properties joint testing device and method for hydrate-containing sediments. Drawing on the successful experience of the existing triaxial shear joint testing system, the present invention introduces complex resistivity testing and research methods, redesigns and improves the existing ring shear device, and forms a comprehensive ring shear testing system with high testing accuracy and diverse monitoring methods.

[0008] The present application combines complex resistivity testing with ring shear testing to propose an electrically assisted ring shear testing system. Compared with conventional resistivity testing, the complex conductivity method can perform high-density measurements in the frequency domain and simultaneously obtain multiple parameters such as complex conductivity amplitude, phase angle, real part and imaginary part. The complex conductivity spectrum or complex dielectric constant spectrum can better reflect the hydrate saturation and sediment microstructure changes. An innovative method of inner and outer box rotational shearing is proposed to meet the requirements of testing the destruction characteristics of hydrate-containing sediments under large deformation conditions and the deformation laws under shear slip conditions. The introduction of irregular electrodes to test complex resistivity can accurately reflect the hydrate saturation and the laws of changes in the electrical properties of the sediments, and specifically solves the problems of single testing means and low testing accuracy of existing ring shear testing devices for hydrate-containing sediments, providing new ideas for the evaluation of submarine slope stability and landslide mechanism analysis in marine natural gas hydrate areas.

[0009] The technical solution adopted by the present invention is: A combined test device for annular shear and electrical properties of hydrate-containing sediments, including a high-pressure reactor system, a shear box system, a complex resistivity test system, an axial loading system, a rotation system, a gas supply system, a temperature control system and a data processing system, etc., can provide the high-pressure and low-temperature conditions required for the preparation of hydrate-containing sediment samples, the simulation of internal and external rotational shear of samples under stress, and the complex resistivity test conditions. The shear box system innovatively adopts an internal and external rotational shear mode, and is arranged in the middle position inside the high-pressure reactor system. It cooperates with the high-pressure reactor system to form a flat annular column structure cavity to place hydrate-containing sediment samples, reducing torsional loading friction and making the test results more accurate; its lower part is connected to the rotation system, which can simulate the rotational shear process of the sample; its upper part is provided with the axial loading system, which applies an axial load to the sample, and can simulate the influence of reservoir stress at different depths on the rotational shear process; electrodes are installed on both the shear box system and the high-pressure reactor system, and can be used to test the synthesis of natural gas hydrates in cooperation with the complex resistivity test system. The resistivity / conductivity of the sample during the process and the ring shear process is detected; the reactor chamber in the high-pressure reactor system is connected to the gas supply system, which can provide the gas and high-pressure environment required for the hydrate-containing sediment sample; in addition, the high-pressure reactor system, shear box system, complex resistivity test system, axial loading system, and rotation system are placed as a whole inside the temperature control system to provide a suitable temperature environment for natural gas hydrate synthesis and inhibit hydrate decomposition during the ring shear process; the test devices and control devices arranged in the above systems are all connected to the data processing system to provide control for the ring shear and electrical test process of the natural gas hydrate-containing sediment and to collect and process data.

[0010] Furthermore, the high-pressure reactor system includes a sample, a reactor body, a reactor cavity, an upper flange, a lower flange, bolts, a flow channel, etc., which are used to realize the synthesis of hydrate-containing sediment samples, the sample rotation shear test and electrical characteristics test; the system body is the reactor body, and the upper and lower ends are respectively connected to the upper flange and the lower flange, and are fixed by the bolts, forming the reactor cavity inside; its inner side cooperates with the shear box system to form the flat circular column structure cavity to place the sample; in addition, the upper flange is provided with the flow channel, the lower end of which is connected to the reactor cavity, and the upper end is connected to the gas supply system, which can assist the high-pressure gas in the gas supply system to enter the reactor cavity and form a high-pressure environment.

[0011] Furthermore, the shear box system can cooperate with the high-pressure reactor system to realize the synthesis of hydrate-containing sediment samples and the simulation of rotational shearing, including an inner shear box, a lower insulating layer, a sealing ring, and a centralizer. The outer part is the high-pressure reactor system, the upper part is the axial loading system, and the lower part is connected to the rotation system. Its main body is the inner shear box, which is a rotatable columnar body. Its outer side cooperates with the reactor body to form a flat annular column structure cavity to place the sample. The lower insulating layer is arranged between the lower part of the sample and the inner shear box, which can provide an insulating environment to assist the complex resistivity test; its lower part passes through the center of the lower flange and is connected to the rotation system to realize the rotation of the inner shear box to complete the ring shear test of the sample; the sealing ring and the centralizer are arranged in sequence from top to bottom between the inner shear box and the lower flange, which can realize the normal rotation of the inner shear box and prevent the leakage of high-pressure gas during the rotation process.

[0012] Furthermore, the complex resistivity test system mainly includes electrodes, electrode protection sleeves, resistance measurement components, and resistivity analyzer, which can monitor the resistivity / conductivity of the sample in real time during hydrate synthesis and rotational shearing. The electrodes are arranged in pairs on both sides of the sample, fixed to the inner shear box system through the electrode protection sleeves, connected to the resistivity analyzer through the resistance measurement component, and the resistance measurement component passes through the inner shear box and the reactor body into the reactor cavity to monitor the resistivity / conductivity changes of the sample between the electrodes.

[0013] In order to adapt to the ring shear device and prevent the complex resistivity test system from affecting the ring shear test process of hydrate-containing sediments, the shape of the electrode is innovatively designed according to the side shapes of the inner shear box and the reactor body, so that its special-shaped electrode fits the sample better. At the same time, the upper insulating layer and the lower insulating layer are added to the upper and lower sides of the sample to provide a complete insulating environment for the complex resistivity test without affecting the ring shear test. The introduction of the complex resistivity test system here is not a simple reorganization of the device structure, but to achieve ring shear-electrical combined testing. Both parts have been redesigned and improved to ensure that the two can be organically combined to achieve better testing results.

[0014] Furthermore, the axial loading system is located on the upper part of the high-pressure reactor system and contacts with the internal shear box system. It mainly includes an axial loading device, an axial displacement meter, a balancing shaft, an upper pressure plate, an upper insulating layer, a straightening rod, a sliding sleeve, a sealing ring, and a straightening sleeve, which can apply a certain axial load to the sample; the main body is the axial loading device, on which the axial displacement meter is designed, which can record the corresponding displacement while axially loading; its lower end is connected to the upper pressure plate via the balancing shaft to compress the sample and maintain stability; the balancing shaft passes through the middle of the upper flange, and is provided with the sealing ring and the straightening sleeve to assist the axial loading process; the upper insulating layer is provided at the lower end of the upper pressure plate to directly contact the sample, and the straightening rod is designed on its side, and by cooperating with the sliding sleeve, it assists the up and down movement of the upper pressure plate during the axial loading process.

[0015] Furthermore, the main function of the rotating system is to provide power and control for the rotating shearing process, and mainly includes a servo motor, a reducer, a coupling, a torque sensor, a transmission shaft, a straightening bearing, and a straightening sleeve, and its upper part is directly connected to the inner shear box. The servo motor is connected to the reducer, the coupling, the torque sensor, and the transmission shaft from bottom to top, and finally cooperates with the inner shear box, so that the lower rotating system monitors the output power, torque, and angle of rotation in real time during the process of providing ring shearing power; the straightening bearing and the straightening sleeve are arranged on the outside of the transmission shaft in sequence, which can ensure that no lateral deviation occurs during the transmission process.

[0016] Furthermore, the main function of the gas supply system is to provide a gas source for the synthesis of hydrate-containing sediments and maintain a high-pressure environment for the reaction chamber and the sample, and mainly includes accessories such as gas cylinders, valves, flow meters, pressure gauges and high-pressure pipelines; the gas cylinders are connected to the valves, flow meters and pressure gauges in sequence through high-pressure pipelines, and finally connected to the flow channel.

[0017] Furthermore, the temperature control system mainly includes a constant temperature box and a temperature controller, etc., which can provide a suitable temperature environment for the natural gas hydrate synthesis and rotational shear experiment process. The high-pressure reactor system, shear box system, complex resistivity test system, axial loading system, and rotation system are all located inside it.

[0018] Furthermore, the data processing system mainly includes a data processor, a computer, and auxiliary accessories and connecting cables, etc., which are mainly used to collect and record data during the experiment and to monitor and control the test in real time.

[0019] Furthermore, sealing rings are provided on the contact surfaces of the upper flange and the lower flange with the reactor to prevent gas leakage, and a proper amount of lubricating oil can be applied during the installation process.

[0020] Furthermore, the bolt fixing position can prevent gaskets or sealing rings from being used for sealing and protecting the device.

[0021] Furthermore, the inner shear box is provided with accessories and fixtures required for installing the complex resistivity test system, and is provided with space for placing connecting wires to realize the transmission of test signals and the control of the test device.

[0022] Furthermore, the upper pressure plate is located inside the cavity formed by the reaction kettle body and the inner shear box, and directly applies an axial load to the sample. The cooperation of the three needs to meet the requirement of rotational shear of the sample.

[0023] Furthermore, the inner shear box passes through the reactor body and the lower flange in sequence, and a seal is provided in the middle to prevent gas leakage. At the same time, in order to facilitate installation, a proper amount of lubricating oil and other materials are applied to the side.

[0024] Furthermore, the upper insulating layer is generally a coating or an adhesive protective layer, which needs to meet the insulation requirements during the complex resistivity test, and the upper insulating layer cannot be defective or damaged.

[0025] Furthermore, the flow meter and pressure gauge in the gas supply system also require necessary protective covers, fixtures and accessories at the installation position of the high-pressure pipeline, and the installation positions of the two can be swapped.

[0026] Furthermore, a connection device and accessories are provided at the connection between the fluid channel and the gas supply system, which can ensure that the high-pressure gas in the gas supply system can smoothly enter the interior of the reactor chamber.

[0027] Furthermore, the data processor is connected to the monitoring device via a data line and a connector.

[0028] Furthermore, the skeleton filler of the sample can be quartz sand, clay, glass balls, aluminum balls, etc.

[0029] Furthermore, the gas required for sample synthesis may be methane, ethane, carbon dioxide or other gases, or a suitable alkane mixed gas.

[0030] Furthermore, the water required for synthesizing the hydrate is distilled water or deionized water, and a proper amount of a hydrate promoter such as sodium dodecyl sulfate (SDS) can be added to accelerate the synthesis rate.

[0031] Based on the above device, the present invention also discloses a combined ring shear-acoustic testing method for hydrate-containing sediments, which mainly includes the following steps: S1. Equipment air tightness inspection and calibration: After the whole device is connected, the air tightness is checked, the axial loading module and the rotation drive module are calibrated for module resistance, and the initial values ​​of the initial longitudinal motion module resistance and the rotation module resistance are determined; S2. Sample preparation: A certain mass of sediment and water are mixed thoroughly and placed in the annular space formed between the reactor body and the inner shear box, and fully compacted; S3. Pre-consolidation: The axial loading device is adjusted to apply a certain axial stress to the sample, the stress of the axial loading device and the displacement of the axial displacement meter are recorded in real time, the stress and displacement changes are monitored in real time, the axial stress on the sample is maintained unchanged, and the pre-consolidation process of the sample is completed; S4. Hydrate synthesis: Keeping the effective axial stress of the sample in step S3 unchanged, injecting methane gas into the reactor chamber, operating the temperature controller to set the temperature and keep it constant, and keeping the temperature and pressure conditions to meet the hydrate synthesis phase equilibrium conditions until the hydrate synthesis process is completed; during the hydrate synthesis process, testing the sample through the electrode and monitoring it in real time through the resistivity analyzer, analyzing the relationship between the hydrate content and the complex resistivity; S5, Ring shear test: The output power and rotation speed of the servo motor are adjusted to drive the inner shear box to rotate, and a ring shear test is performed on the sample. The torque and rotation angle data are recorded in real time by the torque sensor, and the ring shear test is stopped when the rotation angle reaches a set value; S6, complex resistivity test: During the ring shearing process, the complex impedance spectrum of the sample is tested by the electrode, and the complex resistivity or complex conductivity can be further calculated; the changes in the complex resistivity or complex conductivity of the sample before, during and after the ring shearing are compared to explore the intrinsic relationship between the complex resistivity and the damage and destruction of the hydrate-containing sediment sample; S7. End of the experiment: Release the gas in the reactor chamber, adjust the axial loading device to release the load of the sample, control the temperature controller to raise the temperature in the constant temperature box to room temperature, disassemble the upper flange and the lower flange in the high-pressure reactor system, take out the inner shear box, observe the shear surface shape of the sample, disassemble the device and organize the equipment.

[0032] Furthermore, the shear stress τ and the shear strain γ in step S5 can be expressed by the following formula: (1); (2); Where r1 and r2 are the inner and outer diameters of the hollow ring; h is the height of the specimen, M is the torque, and θ is the angular displacement.

[0033] Furthermore, the complex conductivity σ in step S6 is * It can be calculated by the following formula: (3); In the formula, ρ * is the complex resistivity, Z is the complex impedance, L and S are the equivalent geometric parameters of the test sample.

[0034] Compared with the existing ring shear simulation device and test method for natural gas hydrate-containing sediments, the functions and technical effects that can be achieved by this invention are as follows: In view of the unique physical properties of natural gas hydrates and engineering requirements, a special internal and external rotating shear box system is designed, and a high-precision low-frequency complex conductivity spectrum testing system is introduced for the first time. In coordination with the high-pressure reactor system, axial loading system, and rotation system, the mechanical behavior and complex resistivity change law of hydrate-containing sediments before, during, and after rotational shear are analyzed to meet the requirements of the joint shear-electrical testing of natural gas hydrates. Combined with shear stress, shear strain, complex conductivity and other parameters, quantitative evaluation of the damage and destruction process of hydrate-containing sediments is realized, providing technical support for the evaluation and prediction of submarine landslides in marine natural gas hydrate areas.

[0035] In addition, the present invention has the following beneficial effects: (1) The innovative use of internal and external shear modes to simulate the ring shear process of hydrate-bearing sediments reduces the torsional loading friction and makes the test results more accurate. This provides another available mode for ring shear testing in the hydrate field and promotes the development of ring shear testing technology for hydrate-bearing sediments. (2) By designing irregular-shaped electrodes and adding insulating layers, high-precision low-frequency complex resistivity testing was performed for the first time in the hydrate field. This enabled analysis of resistivity changes during the hydrate synthesis process and the sediment ring shear failure process, providing an effective monitoring method for the ring shear failure process of hydrate-bearing sediments. (3) By combining the device and method described in the present invention, the relationship between shear stress, strength and other parameters and hydrate saturation can be measured with high test accuracy, which is closer to the field test of natural gas hydrate reservoir exploration and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the ring shear-electrical combined testing device for hydrate-containing sediments described in the present invention.

[0037] Figure 2 for Figure 1 Schematic diagram of the structure of the device section AA.

[0038] In the figure: 11, sample; 12, reactor body; 13, reactor chamber; 14, upper flange; 15, lower flange; 16, bolt; 17, flow channel; 21, inner shear box; 22, lower insulation layer; 23, sealing ring; 24, centralizer; 31, axial loading device; 32, axial displacement meter; 33, balance shaft; 34, upper pressure plate; 35, upper insulation layer; 36, centralizer rod; 37, sliding sleeve; 38, sealing ring; 39, centralizer 1. Straightening sleeve; 41. Servo motor; 42. Reducer; 43. Coupling; 44. Torque sensor; 45. Drive shaft; 46. Straightening bearing; 47. Straightening sleeve; 51. Gas cylinder; 52. Valve; 53. Flow meter; 54. Pressure gauge; 61. Electrode; 62. Electrode protection sleeve; 63. Resistance measurement assembly; 64. Resistivity analyzer; 71. Constant temperature box; 72. Temperature controller; 81. Data processor; 82. Computer. DETAILED DESCRIPTION

[0039] To facilitate those skilled in the art to understand the present invention, the specific implementation of the present invention is described below in conjunction with the accompanying drawings. Under the premise of no conflict, the embodiments described in this patent application and the features described in the embodiments can be combined with each other arbitrarily, in order to make the technical effect of this patent more perfect.

[0040] In addition, the present invention can also be implemented in other ways different from those described in the following examples. Therefore, the protection scope of the present invention is not limited by the specific implementation examples disclosed below.

[0041] like Figure 1As shown, a combined test device for annular shear and electrical characteristics of hydrate-containing sediments includes a high-pressure reactor system, a shear box system, a complex resistivity test system, an axial loading system, a rotation system, a gas supply system, a temperature control system, and a data processing system, etc., which can provide the high-pressure and low-temperature conditions required for the preparation of hydrate-containing sediment samples, the simulation of internal and external rotational shear of samples under stress, and the complex resistivity test conditions. The shear box system innovatively adopts an internal and external rotational shear mode, which is set in the middle position inside the high-pressure reactor system, and cooperates with the high-pressure reactor system to form a flat annular column structure cavity to place hydrate-containing sediment samples, reducing torsional loading friction and making the test results more accurate; its lower part is connected to the rotation system, which can simulate the rotational shear process of the sample; its upper part is provided with an axial loading system to apply axial load to the sample, which can simulate the influence of reservoir stress at different depths on the rotational shear process; electrodes are installed on the shear box system and the high-pressure reactor system, and can be used to test the synthesis of natural gas hydrates in cooperation with the complex resistivity test system. The resistivity / conductivity of the sample during the process and the ring shear process is detected; the reactor chamber in the high-pressure reactor system is connected to the gas supply system, which can provide the gas and high-pressure environment required for the hydrate-containing sediment sample; in addition, the high-pressure reactor system, the shear box system, the complex resistivity test system, the axial loading system, and the rotation system are placed inside the temperature control system as a whole, providing a suitable temperature environment for the synthesis of natural gas hydrates and inhibiting the decomposition of hydrates during the ring shear process; the test devices and control devices arranged in the above systems are all connected to the data processing system, providing control for the ring shear and electrical test process of the natural gas hydrate-containing sediment and collecting and processing the data.

[0042] Specifically, the high-pressure reactor system includes a sample 11, a reactor body 12, a reactor chamber 13, an upper flange 14, a lower flange 15, bolts 16, a flow channel 17, etc., which are used to realize the synthesis of hydrate-containing sediment samples, sample rotation shear testing and electrical characteristics testing; the main body of the high-pressure reactor system is the reactor body 12, and the upper and lower ends are respectively connected to the upper flange 14 and the lower flange 15, and are fixed by bolts 16, and a reactor chamber 13 is formed inside; its inner side cooperates with the shear box system to form a flat annular column structure cavity to place the sample 11; in addition, the upper flange is provided with a flow channel 17, the lower end of which is connected to the reactor chamber 13, and the upper end is connected to the gas supply system.

[0043] The shear box system includes an inner shear box 21, a lower insulating layer 22, a sealing ring 23, and a stabilizer 24. The outside of the shear box 21 is a high-pressure reactor system, the upper part is an axial loading system, and the lower part is connected to the rotation system; the inner shear box 21 is a rotatable columnar body, and its outer side cooperates with the reactor body 12 to form a flat annular column structure cavity to place the sample 11, and a lower insulating layer 22 is arranged between the lower part of the sample 11 and the inner shear box 21; the lower part of the inner shear box 21 is connected to the rotation system through the lower flange center 15, and the contact surfaces of the two are provided with sealing rings 23 and stabilizers 24 from top to bottom.

[0044] During the rotary shearing process, the rotary system provides power to drive the inner shear box 21 to rotate, while the reactor body 12 is fixed, and the two cooperate to form a rotary shearing effect on the sample 11; in addition, the sealing ring 23 and the stabilizer 24 ensure the normal rotation of the inner shear box 21 during the shearing process and prevent the gas in the sample 11 and the reaction chamber 13 from leaking out along the contact surface.

[0045] The axial loading system is located at the upper part of the high-pressure reactor system and is in contact with the internal shear box system. It mainly includes an axial loading device 31, an axial displacement meter 32, a balancing shaft 33, an upper pressure plate 34, an upper insulating layer 35, a straightening rod 36, a sleeve 37, a sealing ring 38, and a straightening sleeve 39. The axial loading body is the axial loading device 31, on which an axial displacement meter 32 is arranged, and the lower end of which is connected to the upper pressure plate 34 via the balancing shaft 33; the balancing shaft 33 passes through the middle of the upper flange 14, and is provided with a sealing ring 23 and a straightening sleeve 24 to assist the axial loading process; the lower end of the upper pressure plate 34 is provided with an upper insulating layer 35 in direct contact with the sample 11, and a straightening rod 36 is arranged on its side, which cooperates with the sleeve 37 to assist the upper pressure plate 34 to move up and down during the axial loading process.

[0046] The rotating system mainly includes a servo motor 41, a reducer 42, a coupling 43, a torque sensor 44, a transmission shaft 45, a centering bearing 46, and a centering sleeve 47, and its upper part is directly connected to the inner shear box 21. The servo motor 41 is connected to the reducer 42, the coupling 43, the torque sensor 44, and the transmission shaft 45 in sequence from bottom to top, and finally cooperates with the inner shear box 21. The outer side of the transmission shaft 45 is sequentially provided with a centering bearing 46 and a centering sleeve 47.

[0047] The main function of the gas supply system is to provide a gas source for the synthesis of hydrate-containing sediments and maintain a high-pressure environment in the reactor chamber 13 and the sample 11. The gas supply system mainly includes accessories such as a gas cylinder 51, a valve 52, a flow meter 53, a pressure gauge 54 and a high-pressure pipeline; the gas cylinder 51 is connected to the valve 52, the flow meter 53 and the pressure gauge 54 in sequence through a high-pressure pipeline, and finally connected to the flow channel 17.

[0048] The complex resistivity test system mainly includes electrodes 61, electrode protection covers 62, resistance measuring components 63, and resistivity analyzer 64. The electrodes 61 are placed in pairs on both sides of the sample 11 and close to the sample 11. They are fixed to the inner shear box 21 and the reactor body 12 through the electrode protection covers 62, and are connected to the resistivity analyzer 64 through the resistance measuring components 63. The resistance measuring components 63 pass through the inner shear box 21 and the reactor body 12 and enter the reactor cavity 13.

[0049] In order to adapt to the ring shear device and prevent the complex resistivity test system from affecting the ring shear test process of hydrate-containing sediments, the shape of the electrode 61 is innovatively designed according to the side shapes of the inner shear box 21 and the reactor body 12, so that its special-shaped electrode fits the sample 11 more closely. At the same time, an upper insulating layer 35 and a lower insulating layer 22 are added to the upper and lower sides of the sample 11 to provide a complete insulating environment for the complex resistivity test without affecting the ring shear test. The introduction of the complex resistivity test system here is not a simple reorganization of the device structure, but to achieve a ring shear-electrical combined test. Both parts have been redesigned and improved to ensure that the two can be organically combined to achieve better test results.

[0050] During the ring shear test, the electrode 61 installed on the inner shear box 21 rotates accordingly, and the electrode 61 installed on the reactor body 12 remains fixed accordingly. The resistivity change of the sample 11 can be monitored and controlled in real time by the resistivity analyzer 64.

[0051] The temperature control system mainly includes a constant temperature box 71 and a temperature controller 72, etc., and the high-pressure reactor system, shear box system, complex resistivity test system, axial loading system, and rotation system are all located inside it.

[0052] The data processing system mainly includes a data processor 81, a computer 82, and auxiliary accessories and connecting cables, etc., which are mainly used to collect and record data during the experiment and to monitor and control the test in real time.

[0053] In conjunction with the hydrate-containing sediment ring shear-electricity combined testing device, the present invention also discloses a hydrate-containing sediment ring shear-acoustic combined testing method, which mainly includes the following steps: Step S1: Equipment air tightness inspection and calibration: After the whole device is connected, an air tightness check is performed, the axial loading module and the rotation drive module are calibrated for module resistance, and the initial values ​​of the initial longitudinal motion module resistance and the rotation module resistance are determined.

[0054] Step S2: Sample preparation: A certain mass of sediment is mixed with water and placed in the annular space formed between the reactor body 12 and the inner shear box 21 to be fully compacted.

[0055] Step S3: Pre-consolidation: The axial loading device 31 is adjusted to apply a certain axial stress to the sample, and the change rules of the stress of the axial loading device 31 and the displacement of the axial displacement meter 32 are recorded in real time. The changes of stress and displacement are monitored in real time, and the axial stress on the sample 11 is maintained unchanged to complete the pre-consolidation process of the sample 11.

[0056] Step S4, hydrate synthesis: Keep the effective axial stress of the sample 11 in step S3 unchanged, inject methane gas into the reactor chamber 13, operate the temperature controller 72 to set the temperature and keep it constant, and keep the temperature and pressure conditions to meet the hydrate synthesis phase equilibrium conditions until the hydrate synthesis process is completed; during the hydrate synthesis process, the sample 11 is tested by the electrode 61 and monitored in real time by the resistivity analyzer 64 to analyze the relationship between the hydrate content and the complex resistivity.

[0057] Step S5: Ring shear test: The output power and rotation speed of the servo motor 41 are adjusted to drive the inner shear box 21 to rotate, and a ring shear test is performed on the sample 11. The torque and rotation angle data are recorded in real time by the torque sensor 44. When the rotation angle reaches a set value, the ring shear test is stopped; Among them, the shear stress τ and shear strain γ can be expressed by the following formula: (1); (2); Where r1 and r2 are the inner and outer diameters of the hollow ring; h is the height of the specimen, M is the torque, and θ is the angular displacement.

[0058] Step S6: Complex resistivity test: During the ring shearing process, the complex impedance spectrum of the sample 11 is tested by the electrode 61, and the complex resistivity or complex conductivity can be further calculated; Among them, the complex conductivity σ * It can be calculated by the following formula: (3); In the formula, ρ * is the complex resistivity, Z is the complex impedance, L and S are the equivalent geometric parameters of the test sample; By comparing the changes in complex resistivity or complex conductivity of sample 11 before, during and after ring shearing, the intrinsic relationship between complex resistivity and the damage and destruction of hydrate-containing sediment samples was explored.

[0059] Step S7, end the experiment: Release the gas in the reactor chamber 13, adjust the axial loading device 31 to release the load of the sample 11, control the temperature controller 72 to raise the temperature in the constant temperature box 71 to room temperature, disassemble the upper flange 14 and the lower flange 15 in the high-pressure reactor system, take out the inner shear box 21, observe the shear surface shape of the sample 11, disassemble the device and organize the equipment.

[0060] The relevant technical contents not mentioned in the above methods can be realized by adopting or drawing on existing technologies.

[0061] The above-described embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A combined test device for ring shear and electrical properties of hydrate-containing sediments, comprising a high-pressure reactor system, a shear box system, an axial loading system, a rotation system, a gas supply system, a temperature control system and a data processing system, characterized in that: It also includes a complex resistivity test system; the shear box system adopts an internal and external rotation shear mode, the shear box system is arranged in the middle position inside the high-pressure reactor system, and cooperates with the high-pressure reactor system to form a flat annular column structure cavity to place the sample (11) containing hydrate sediments, thereby reducing the torsional loading friction resistance; the lower part of the shear box system is connected to the rotation system to realize the simulation of the rotation shear process of the sample (11); the upper part of the shear box system is provided with the axial loading system to apply axial load to the sample (11) to simulate the influence of reservoir stress at different depths on the rotation shear process; electrodes (61) are installed on the shear box system and the high-pressure reactor system, so that the complex resistivity test system can detect the resistivity / conductivity of the sample (11) during the natural gas hydrate synthesis process and the annular shear process; the reactor chamber (13) in the high-pressure reactor system is connected to the gas supply system to provide the gas and high-pressure environment required by the hydrate sediment sample (11); The high-pressure reactor system, the shear box system, the complex resistivity test system, the axial loading system, and the rotation system are integrally placed inside the temperature control system to provide a suitable temperature environment for natural gas hydrate synthesis and inhibit hydrate decomposition during the ring shear process; the test devices and control devices provided in the above systems are all connected to the data processing system to provide control for the ring shear and electrical testing process of natural gas hydrate-containing sediments and to collect and process data.

2. The testing device according to claim 1, characterized in that: The high-pressure reactor system comprises a sample (11), a reactor body (12), a reactor chamber (13), an upper flange (14), a lower flange (15), bolts (16) and a flow channel (17), and is used to realize the synthesis of a hydrate-containing sediment sample (11), a rotational shear test of the sample (11), and an electrical characteristic test; the upper and lower ends of the reactor body (12) are respectively connected to the upper flange (14) and the lower flange (15), and are fixed by the bolts (16), and the reactor chamber (13) is formed inside; the reactor chamber (13) is also provided with a flat annular column structure chamber whose inner side cooperates with the shear box system to place the sample (11); the upper flange (14) is provided with the flow channel (17), the lower end of the flow channel (17) is connected to the reactor chamber (13), and the upper end is connected to the gas supply system, so as to assist the high-pressure gas in the gas supply system to enter the reactor chamber (13) and form a high-pressure environment.

3. The testing device according to claim 1, characterized in that: The shear box system comprises an inner shear box (21), a lower insulating layer (22), a sealing ring (38) and a centralizer (24); the inner shear box (21) is a rotatable columnar body, and a flat annular column structure cavity is arranged on the outer side of the inner shear box (21) to place the sample (11), and the lower insulating layer (22) is arranged between the lower part of the sample (11) and the inner shear box (21) to provide an insulating environment to assist the complex resistivity test; the lower part of the inner shear box (21) passes through the center of the lower flange (15) and is connected to the rotating system to realize the rotation of the inner shear box (21) to complete the ring shear test of the sample (11); the sealing ring (38) and the centralizer (24) are arranged in sequence from top to bottom between the inner shear box (21) and the lower flange (15) to realize the normal rotation of the inner shear box (21) and prevent the leakage of high-pressure gas during the rotation process.

4. The testing device according to claim 1, characterized in that: The complex resistivity testing system comprises an electrode (61), an electrode protection sleeve (62), a resistance measuring component (63) and a resistivity analyzer (64), and is used for real-time monitoring of the resistivity / conductivity of the sample (11) during hydrate synthesis and rotational shearing. The electrodes (61) are located in pairs on both sides of the sample (11), fixed to the inner shear box system via the electrode protection sleeve (62), and connected to the resistivity analyzer (64) via the resistance measuring component (63). The resistance measuring component (63) passes through the inner shear box (21) and the reactor body (12) and enters the reactor chamber (13) to monitor the resistivity / conductivity changes of the sample (11) between the electrodes (61).

5. The testing device according to claim 1, characterized in that: The axial loading system is located at the upper part of the high-pressure reactor system and is in contact with the inner shear box (21) system, and comprises an axial loading device (31), an axial displacement meter (32), a balancing shaft (33), an upper pressure plate (34), an upper insulating layer (35), a straightening rod (36), a sliding sleeve (37), a sealing ring (38) and a straightening sleeve (39), and is used to apply an axial load to the sample (11); the axial displacement meter (32) is arranged at the upper part of the axial loading device (31) and is used to record the corresponding displacement while axially loading; The balancing shaft (33) is connected to the upper pressure plate (34) for compressing the sample (11) and maintaining stability; the balancing shaft (33) passes through the middle of the upper flange (14) and is provided with the sealing ring (38) and the straightening sleeve (39) to assist the axial loading process; the upper insulating layer (35) is provided at the lower end of the upper pressure plate (34) and is in direct contact with the sample (11); the straightening rod (36) is provided on the side and cooperates with the sliding sleeve (37) to assist the upper and lower movement of the upper pressure plate (34) during the axial loading process.

6. The testing device according to claim 1, characterized in that: The rotary system is used to provide power and control for the rotary shearing process, and comprises a servo motor (41), a reducer (42), a coupling (43), a torque sensor (44), a transmission shaft (45), a straightening bearing (46) and a straightening sleeve (47); the servo motor (41), the reducer (42), the coupling (43), the torque sensor (44), the transmission shaft (45) and the inner shear box (21) are connected in sequence from bottom to top, so that the lower rotary system monitors the output power, torque and rotation angle in real time during the process of providing the ring shearing power; the straightening bearing (46) and the straightening sleeve (47) are arranged in sequence on the outer side of the transmission shaft (45) to ensure that no lateral deviation occurs during the transmission process.

7. The testing device according to claim 2, characterized in that: The gas supply system is used to provide a gas source for hydrate-containing sediment synthesis and maintain a high-pressure environment in the reaction kettle chamber (13) and the sample (11), and comprises a gas cylinder (51), a valve (52), a flow meter (53), a pressure gauge (54) and a high-pressure pipeline; the gas cylinder (51) is connected to the valve (52), the flow meter (53) and the pressure gauge (54) in sequence through the high-pressure pipeline, and is finally connected to the flow channel (17).

8. The testing device according to claim 1, characterized in that: The temperature control system comprises a constant temperature box (71) and a temperature controller (72), which are used to provide a suitable temperature environment for the natural gas hydrate synthesis and rotational shear experiment process; the high-pressure reactor system, shear box system, complex resistivity test system, axial loading system, and rotation system are all located inside the constant temperature box (71).

9. The testing device according to claim 1, characterized in that: The data processing system comprises a data processor (81), a computer (82), and auxiliary accessories and connecting cables, and is mainly used to collect and record data during the experiment and to perform real-time monitoring and control of the test.

10. The method for testing a device according to any one of claims 1 to 9, comprising the following steps: S1. Equipment air tightness inspection and calibration: After the whole device is connected, an air tightness check is performed, and the axial loading device (31) and the rotation system are calibrated for the resistance, and the initial values ​​of the initial longitudinal motion resistance and the rotation resistance are determined; S2. Preparation of sample (11): A certain mass of sediment and water are mixed thoroughly and placed in the annular space formed between the reactor body (12) and the inner shear box (21) to be fully compacted; S3. Pre-consolidation: The axial loading device (31) is adjusted to apply a certain axial stress to the sample (11), and the stress of the axial loading device (31) and the displacement of the axial displacement meter (32) are recorded in real time, and the stress and displacement changes are monitored in real time to maintain the axial stress on the sample (11) unchanged, thereby completing the pre-consolidation process of the sample (11); S4. Hydrate synthesis: The effective axial stress of the sample (11) in step S3 is kept constant, methane gas is injected into the reactor chamber (13), the temperature controller (72) is operated to set the temperature and keep it constant, and the temperature and pressure conditions are kept to meet the hydrate synthesis phase equilibrium conditions until the hydrate synthesis process is completed; during the hydrate synthesis process, the sample (11) is tested by the electrode (61) and monitored in real time by the resistivity analyzer (64), and the relationship between the hydrate content and the complex resistivity is analyzed; S5, Ring shear test: Adjusting the output power and rotation speed of the servo motor (41) to drive the inner shear box (21) to rotate, performing a ring shear test on the sample (11), recording torque and rotation angle data in real time through a torque sensor (44), and stopping the ring shear test when the rotation angle reaches a set value; S6, complex resistivity test: During the ring shearing process, the complex impedance spectrum of the sample (11) is tested by the electrode (61), and the complex resistivity or complex conductivity can be further calculated; the changes in the complex resistivity or complex conductivity of the sample (11) before, during, and after the ring shearing are compared to explore the intrinsic relationship between the complex resistivity and the damage and destruction of the hydrate-containing sediment sample (11); S7. End of the experiment: The gas in the reactor chamber (13) is released, the axial loading device (31) is adjusted to release the load of the sample (11), the temperature controller (72) is controlled to raise the temperature in the thermostatic box (71) to room temperature, the upper flange (14) and the lower flange (15) in the high-pressure reactor system are disassembled, the inner shear box (21) is taken out, the shear surface shape of the sample (11) is observed, the device is disassembled and the equipment is arranged.

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