Hydrate sediment large displacement deformation-acoustic-electric integrated characterization device and method

Abstract

The invention relates to the technical field of marine natural gas hydrate exploration and testing, in particular to a hydrate sediment large-displacement deformation-acoustic-electric integrated characterization device and a hydrate sediment large-displacement deformation-acoustic-electric integrated characterization method. Comprising a high-pressure reaction kettle module, a rotary shear box module is arranged in the high-pressure reaction kettle module, the rotary shear box module is connected with a sound wave-resistance testing module, the rotary shear box module comprises an upper rotary shear box and a lower rotary shear box, the upper rotary shear box is connected with an axial loading module, and the lower rotary shear box is connected with a rotary driving module; the axial loading module comprises a pressing plate, a plurality of pressing heads are arranged on the pressing plate, the pressing heads are fixedly connected with the upper rotary shear box, and the pressing plate is in sliding connection with the high-pressure reaction kettle module through a vertically-arranged supporting rod. The monitoring and evaluation requirements of the large-displacement deformation failure process of the hydrate-containing sediment are met, and a new thought is provided for sea area hydrate sediment mechanical behavior prediction and engineering geological risk prevention and control.

Description

Technical Field

[0001] The invention relates to the technical field of marine natural gas hydrate exploration and testing, in particular to a large displacement deformation-acoustic-electrical integrated characterization device and method for hydrate sediments. Background Art

[0002] Natural gas hydrate is an important alternative energy source that has attracted the attention of countries around the world. The analysis of the mechanical properties of marine natural gas hydrate sediments is the basis and prerequisite for evaluating reservoir stability and engineering geological risk prevention and control, and is also the key to achieving safe and efficient development of natural gas hydrates. At present, researchers at home and abroad use triaxial shear, direct shear, cyclic loading and unloading and other testing methods to study the mechanical parameters and deformation characteristics of hydrate-containing sediments, preliminarily revealing the destruction mechanism of hydrate-containing sediments under load and speculating on the reservoir stability control mechanism during hydrate extraction. Existing technologies make it difficult to accurately evaluate the mechanical behavior and destruction characteristics of hydrate-containing sediments under large deformation conditions, and cannot effectively solve the problem of studying the initiation and evolution mechanism of submarine landslides in natural gas hydrate areas.

[0003] At present, in order to study the mechanical response characteristics of hydrate-containing sediments under large displacement deformation conditions, researchers have proposed some ring shear test systems and methods suitable for hydrate-containing sediments. Specifically, patent CN114252351B discloses a ring shear test device and method suitable for hydrate-containing sediments, which provides technical support for the exploration of deformation laws and landslide characteristics under long-distance shear sliding conditions after the destruction of hydrate formations. In addition, patent CN118746504A proposes a ring shear device and a ring shear test method under undrained conditions, enriching the system of large deformation test methods for hydrate-containing sediments. However, the existing ring shear test devices and technologies for hydrate-containing sediments are relatively few, the detection means are single, and they only focus on simple mechanical parameter tests, which cannot meet different detection tasks. Therefore, it is urgent to develop multi-means ring shear test methods according to different testing requirements.

[0004] Existing mechanical property testing devices for hydrate-containing sediments are usually combined with acoustic and electrical testing to achieve the acquisition and analysis of acoustic and electrical parameters under deformation conditions. Patent CN110542617B discloses a method for synchronous measurement of dynamic and static mechanical parameters of hydrate sediments, which realizes the synchronous testing of mechanical and acoustic parameters. CN103323352B proposes an experimental method for dynamic triaxial mechanical-acoustic-electrical synchronous testing of natural gas hydrate sediments, which realizes the combined testing of mechanical-acoustic-electrical under triaxial shear conditions. From the above, it can be seen that hydrate-containing sediments require a combination of multiple means to meet engineering needs, and acoustic and electrical testing are important means combined with mechanical parameter testing.

[0005] According to the above existing technologies, the joint measurement of mechanical, acoustic and electrical parameters of hydrate-containing sediments under small deformation conditions can be realized. However, the related devices and technologies for the multi-means joint testing of hydrate-containing sediments under large displacement deformation conditions have not been reported, and technical breakthroughs are urgently needed to fill this gap. In addition, the existing ring shear device for hydrate-containing sediments has a complex structure and poor stability of the axial loading system, which affects the accuracy of the mechanical, acoustic and electrical parameter testing of sediments under ring shear conditions. Summary of the invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and propose a large displacement deformation-acoustic-electrical integrated characterization device and method for hydrate sediments, which can realize the joint synchronous testing of mechanical, acoustic and electrical parameters under rotational shear conditions, meet the monitoring and evaluation needs of the large displacement deformation and destruction process of hydrate-containing sediments, and provide new ideas for the prediction of mechanical behavior of marine hydrate sediments and the prevention and control of engineering geological risks.

[0007] The technical solution of the present invention is: a large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments, comprising a high-pressure reactor module, wherein a rotating shear box module is arranged in the high-pressure reactor module, the rotating shear box module is connected to the acoustic wave-resistance test module, the rotating shear box module comprises an upper rotating shear box and a lower rotating shear box, the upper rotating shear box is connected to the axial loading module, and the lower rotating shear box is connected to the rotation drive module;

[0008] The axial loading module comprises a pressing plate, on which a plurality of pressing heads are arranged, which are fixedly connected to the upper rotating shear box, and the pressing plate is slidably connected to the high-pressure reactor module via a vertically arranged supporting rod.

[0009] In the rotary shear box module of the present invention, the lower surface of the upper rotary shear box contacts the upper surface of the lower rotary shear box, and the lower surface of the upper rotary shear box and the upper surface of the lower rotary shear box are respectively provided with annular grooves, and the annular grooves of the upper rotary shear box and the annular grooves of the lower rotary shear box form an annular sample cavity;

[0010] An insulating layer is arranged between the sample in the sample cavity and the axial loading module in contact with the sample, the side wall of the upper rotating shear box, and the side wall of the lower rotating shear box.

[0011] The high-pressure reactor module comprises a high-pressure reactor body, wherein a closed reactor chamber is formed between the high-pressure reactor body, an upper end cover at the top, and a lower end cover at the bottom, and the rotating shear box module is arranged in the reactor chamber;

[0012] The lower rotating shear box is rotatably connected to the lower end cover, and a sliding sealing ring is provided at the contact surface between the lower rotating shear box and the lower end cover;

[0013] A fluid channel is provided at the upper end cover, and the connection between the high-pressure reactor module and the gas supply module is realized through the fluid channel. Correspondingly, a plurality of air holes are provided on the upper rotating shear box.

[0014] The acoustic wave-resistance test module includes an array of acoustic wave-resistance probes spaced apart inside the sample, each group of acoustic wave-resistance probes includes two acoustic wave-resistance probes symmetrically arranged up and down, the upper acoustic wave-resistance probe is a transmitting probe installed in an upper rotating shear box, and the lower acoustic wave-resistance probe is a receiving probe installed in a lower rotating shear box;

[0015] The outer side of the acoustic wave-resistance probe is wrapped with a protective sleeve, and the protective sleeve is installed in the upper rotating shear box or the lower rotating shear box through an insulating sleeve.

[0016] The axial loading module also includes a vertically arranged balancing shaft, one end of the balancing shaft located outside the reactor chamber is connected to the loading unit, a displacement meter is provided at the loading unit, one end of the balancing shaft located inside the reactor chamber is fixedly connected to the pressing plate, the balancing shaft passes through the upper end cover, and a balancing chamber and a sealing ring are provided on the contact surface between the balancing shaft and the upper end cover;

[0017] A plurality of through holes are arranged at intervals on the upper rotating shear box, and the pressure heads are arranged in the through holes correspondingly, and the pressure heads are fixedly connected to the upper rotating shear box;

[0018] The pressing plate is connected to the lower end cover through a plurality of support rods, the lower ends of the support rods are fixedly connected to the lower end cover, and the upper ends of the support rods are slidably connected to the pressing plate.

[0019] The high-pressure reactor module is arranged in the temperature control module;

[0020] The temperature control module includes a constant temperature box and a temperature controller.

[0021] It also includes a control and data acquisition module, and the data acquisition module is respectively connected with the axial loading module, the rotation driving module, the air supply module, the axial loading module, and the temperature control module.

[0022] The present invention also discloses a testing method using the above-mentioned hydrate sediment large displacement deformation-acoustic-electrical integrated characterization device, the method comprising the following steps:

[0023] S1. Prepare a sample using a testing device;

[0024] S2, axial loading and pre-consolidation, and hydrate synthesis;

[0025] S3. Performing a ring shear test on the hydrate-containing sediment sample;

[0026] The rotation driving module drives the lower rotation shear box to rotate, and the state of the upper rotation shear box remains unchanged, so as to simulate the rotation shear process of the hydrated sediment samples in the upper rotation shear box and the lower rotation shear box;

[0027] S4. Conducting a combined acoustic wave-resistance test on hydrate-containing sediment samples;

[0028] S5. Arrange the equipment after the experiment.

[0029] S6. Experimental data processing and comprehensive analysis of mechanical-acoustic-electrical parameters.

[0030] In step S1, the sediment and deionized water or distilled water are mixed and stirred, and then placed in layers in the sample cavity of the rotating shear box module and fully compacted;

[0031] In step S2, the sample is axially loaded by an axial loading module so that the sample meets the consolidation requirements for the synthesis of hydrate-containing sediments;

[0032] The gas required for hydrate synthesis is injected into the reactor chamber through the gas supply module, and the high-pressure reactor module and the rotating shear box module are refrigerated through the temperature control module to cool the sample in the reactor chamber so that the ambient temperature and pressure conditions of the sample meet the phase equilibrium conditions for hydrate synthesis, thereby realizing the synthesis process of hydrate-containing sediment samples.

[0033] In step S3, during the ring shear test, the torque and angle parameters are monitored and recorded in real time through the driving motor and the torque sensor. When the angle reaches the set value, the driving motor is turned off, the ring shear test is stopped, and the changes in the shear stress and shear strain of the sample during the ring shear process are calculated;

[0034] P-wave velocity V in hydrate-bearing sediments p and shear wave velocity V s It can be calculated by the following formula:

[0035]

[0036] Where L is the vertical distance between two probes in the same acoustic wave-resistance probe group before the ring shearing begins; T p0 is the initial longitudinal wave propagation time of the probe; T s0 is the initial shear wave propagation time of the probe; T p is the propagation time of the longitudinal wave in the sediment; T s is the propagation time of shear waves in sediments;

[0037] The plane distance D that the acoustic wave-resistance probe moves during the rotational shear process can be calculated by the following formula:

[0038] D=2 sin(α / 2)·r,α≤π,

[0039] The distance L′ between the two rotated probe positions and the original position can be expressed by the following formula:

[0040]

[0041] Among them, α is the rotation angle of the probe, and r is the distance from the probe to the rotation center;

[0042] Combining the above formulas, it can be seen that the longitudinal and transverse wave velocities of hydrate-containing sediments during the ring shear process can be calculated by the following formula:

[0043]

[0044] Resistivity of hydrate-containing sediments * The calculation formula is:

[0045]

[0046] Where Z is the complex impedance, l and S are the equivalent geometric parameters of the test sample.

[0047] In step S6, referring to the quantitative relationship between the strength and acoustic wave velocity of hydrate-containing sediments under small deformation conditions, a strength prediction model based on longitudinal wave velocity / resistivity can be established to unify the mechanical-acoustic-electrical parameters and combine the existing geotechnical engineering field to recommend related functional relationships for shear strength prediction, as shown below:

[0048] τ f =a1+a2exp(V p / b),

[0049] τ f =s1 ln(σ*)+s2,

[0050] In the formula, τ f is the peak shear stress, a1, a2 and b are the model coefficients determined by fitting the acoustic wave test data, and s1 and s2 are the model parameters determined by fitting the resistivity data.

[0051] The beneficial effects of the present invention are:

[0052] (1) By installing embedded acoustic wave-resistance probes in the upper rotating shear box and the lower rotating shear box, the combined test of mechanical, acoustic, and electrical parameters of hydrate-containing sediments under ring shear conditions was achieved. The comprehensive shear stress, shear strain, acoustic wave velocity, waveform, and resistivity data can be used to qualitatively and quantitatively evaluate the damage and destruction process of sediments under large deformation conditions, filling the gap in the field of ring shear testing of hydrate-containing sediments.

[0053] (2) The array-type acoustic wave-resistance probes in the acoustic wave-resistance test module can be used to change the number and location of the probe group according to test needs, thereby achieving detailed monitoring of different areas of hydrate-containing sediments and providing more accurate test results.

[0054] (3) Based on the relationship between the rotation angle and the inner and outer diameters of the ring, the calculation method of the longitudinal and transverse wave velocities during the ring shear process was derived, and the evaluation method of the acoustic wave velocity of hydrate-bearing sediments at different ring shear stages was determined;

[0055] (4) The complexity of the ring shear structure used for hydrate-containing sediments is reduced, the stability of the axial loading system is improved, the influence of the mold resistance during the ring shear process is alleviated, and the accuracy of the ring shear process measurement is improved.

[0056] In summary, the present application can meet the demand for joint testing of mechanical, acoustic and electrical parameters of hydrate-containing sediments under large deformation conditions. Through the cooperation between the annular shear box of the embedded acoustic wave-resistance probe and the rotary drive module and the high-pressure reactor module, the simulation of the ring shear destruction of hydrate-containing sediments and the joint testing of acoustic and electrical parameters during the destruction process are realized. The calculation model of the acoustic wave velocity of hydrate-containing sediments during the ring shear process is derived, and the acoustic wave velocity parameters of hydrate-containing sediments under large deformation conditions can be calculated in real time. The comprehensive mechanical, acoustic and electrical parameter change characteristics can realize the quantitative evaluation of sediment damage and destruction process, providing key support for the study of mechanical properties and engineering geological disasters of marine natural gas hydrate reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a schematic diagram of the connection structure of the device;

[0058] Figure 2 1 is a schematic diagram of the top structural view of the upper rotating shear box;

[0059] Figure 3 Schematic diagram of the position between two probes in the same sonic-resistance probe set during rotational shear.

[0060] In the figure: 101 upper rotating shear box; 102 lower rotating shear box; 103 sample; 104 top insulating layer; 105 upper insulating layer; 106 lower insulating layer; 107 bottom insulating layer; 108 pores; 201 acoustic wave-resistance probe; 202 protective cover; 203 insulating ferrule; 204 resistance analyzer; 205 acoustic wave processor; 206 wiring channel; 301 high-pressure reactor body; 302 upper end cover; 304 lower end cover; 304 screws; 305 reactor chamber; 306 sliding sealing ring ; 307 balancing chamber; 308 sealing ring; 309 fluid channel; 401 balancing shaft; 402 loading unit; 403 displacement meter; 404 pressure plate; 405 pressure head; 406 support rod; 407 sleeve; 501 driving motor; 502 reducer; 503 torque sensor; 504 stabilizer; 505 fixing plate; 601 gas cylinder; 602 valve; 603 pressure sensor; 604 flow meter; 701 constant temperature box; 702 temperature controller; 801 data processor; 802 computer. DETAILED DESCRIPTION

[0061] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0062] In the following description, specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0063] like Figure 1As shown, the large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments of the present invention comprises a high-pressure reactor module, a rotating shear box module, an acoustic wave-resistance test module, an axial loading module, a rotating drive module, a gas supply module, a temperature control module, and a control and data acquisition module. Among them, the rotating shear box module is located in the middle position inside the high-pressure reactor module, the lower part of the rotating shear box module is connected to the rotating drive module, and the rotating shear box module is driven to rotate by the rotating drive module; the upper part of the rotating shear box module is in contact with the axial loading module. Under the joint action of the rotating drive module and the axial loading module, the rotating shear process of the hydrate-containing sediment sample can be simulated. The rotating shear box module is connected to the acoustic wave-resistance test module, and the synchronous measurement of the acoustic and electrical parameters of the hydrate-containing sediment under the ring shear condition can be realized. The high-pressure reactor module is located inside the temperature control module, and the temperature control module controls the ambient temperature of the space where the high-pressure reactor module is located, and provides a temperature environment simulating the synthesis and decomposition of hydrates. The high-pressure reactor module is connected to the gas supply module to provide sufficient gas for the synthesis of natural gas hydrates in the sediment. The control and data acquisition module is respectively connected with the axial loading module, the rotation driving module, the air supply module, the axial loading module and the temperature control module to realize real-time monitoring and data acquisition processing during the test process.

[0064] The rotary shear box module includes an upper rotary shear box 101 and a lower rotary shear box 102. The upper rotary shear box 101 is located above the lower rotary shear box 102, and the lower surface of the upper rotary shear box 101 contacts the upper surface of the lower rotary shear box 102. In this embodiment, the upper rotary shear box 101 and the lower rotary shear box 102 are both cylindrical, and an annular groove is provided at the lower surface of the upper rotary shear box 101, and an annular groove is provided at the upper surface of the lower rotary shear box 102. The annular grooves of the upper rotary shear box 101 and the annular grooves of the lower rotary shear box 102 are interconnected to form an annular sample cavity, and the annular cavity contains the sample 103. The axial loading module directly acts on the upper part of the sample 103. The upper rotary shear box 101 is connected to the axial loading module, the lower rotary shear box 102 is connected to the rotary drive module below it, and the lower rotary shear box 102 is rotatably connected to the high-pressure reactor module.

[0065] A top insulating layer 104 is provided between the top of the sample 103 and the axial loading module in contact with it, an upper insulating layer 105 is provided between the side of the sample 103 and the side of the upper rotating shear box in contact with it, a lower insulating layer 106 is provided between the side of the sample 103 and the side of the lower rotating shear box in contact with it, and a bottom insulating layer 107 is provided between the bottom of the sample 103 and the surface of the lower rotating shear box in contact with it. By providing an insulating layer on the outside of the sample, an insulating environment required for electrical parameter testing can be provided without affecting the synchronous measurement of acoustic parameters.

[0066] The upper rotating shear box 101 is provided with a plurality of air holes 108, which are evenly spaced along the circumference of the upper rotating shear box 101. Methane gas enters the annular cavity of the rotating shear box module through the air holes 108, and reacts with the sample 103 in the annular cavity to synthesize hydrates, thereby ensuring the gas source required for hydrate synthesis.

[0067] The acoustic wave-resistance test module is mainly used for large displacement deformation-acoustic-electrical integrated characterization test of hydrate-containing sediments, and is used to characterize the damage and destruction process of sediments under ring shear conditions. The module includes an array of acoustic wave-resistance probes in contact with the sample, and each group of acoustic wave-resistance probes includes two acoustic wave-resistance probes 201 symmetrically arranged up and down, and the two probes are a transmitting probe and a receiving probe. Among them, the acoustic wave-resistance probe located at the top is a transmitting probe, which is installed in the upper rotating shear box and contacts the upper part of the sample; the acoustic wave-resistance probe located at the bottom is a receiving probe, which is installed in the lower rotating shear box and contacts the lower part of the sample. The array of acoustic wave-resistance probes in the present application is evenly spaced along the circumferential direction of the upper rotating shear box and the lower rotating shear box. The array of acoustic wave-resistance probes constitutes an arranged and combined probe installation mode, which ensures the realization of refined detection goals.

[0068] In this embodiment, the acoustic wave-resistance probes 201 are respectively wrapped in protective sleeves 202 , and the protective sleeves 202 are installed in the upper rotating shear box or the lower rotating shear box through insulating sleeves 203 .

[0069] The acoustic wave-resistance probe is connected to the resistance analyzer 204 and the acoustic wave processor 205 through data lines, respectively, and the electrical parameters are detected, recorded and processed through the resistance analyzer 204, and the acoustic parameters are detected, recorded and processed through the acoustic wave processor 205. In this embodiment, a wiring channel 206 is provided in the upper rotating shear box and the lower rotating shear box, respectively, and the data line is arranged in the wiring channel 206.

[0070] The high-pressure reactor module includes a high-pressure reactor body 301, an upper end cover 302 is provided above the high-pressure reactor body 301, and the upper end cover 302 is fixedly connected to the high-pressure reactor body 301 by screws 304, and a lower end cover 303 is provided below the high-pressure reactor body, and the lower end cover 303 is fixedly connected to the high-pressure reactor body 301 by screws. The high-pressure reactor body 301, the upper end cover 302, and the lower end cover 303 form a closed reactor chamber 305, and the rotary shear box module is arranged in the reactor chamber 305.

[0071] The lower rotary shear box 102 of the rotary shear box module passes through the lower end cover 303 and is connected to the rotary drive module below the rotary shear box module. A sliding sealing ring 306 is provided at the contact surface between the lower rotary shear box 102 and the lower end cover 303 to achieve a sealed connection between the lower rotary shear box and the lower end cover.

[0072] The axial loading module passes through the upper end cover to apply an axial load to the sample in the rotating shear box. A balancing cavity 307 and a sealing ring 308 are provided at the contact surface between the axial loading module and the upper end cover. In this embodiment, sealing rings 308 are provided above and below the balancing cavity 307, respectively. The balancing cavity and the sealing ring can assist the axial loading and play a sealing role, thereby realizing a sealed connection between the axial loading module and the upper end cover.

[0073] The upper end cover is provided with a fluid channel 309, which is connected to the gas supply module. The gas generated by the gas supply module flows into the reactor chamber 305 through the channel and enters the sample through the air hole 108 on the upper rotating shear box to react and generate hydrates in the sediment.

[0074] The axial loading module is used to apply an axial load to the sample to simulate the influence of the bottom stress state at different depths on the annular shear characteristics of hydrate sediments. The module includes a balancing shaft 401 arranged in the vertical direction. The balancing shaft passes through the upper end cover 302, and a balancing cavity and several sealing rings are provided at the contact surface between the balancing shaft 401 and the upper end cover 302. The top end of the balancing shaft 401 is located outside the reactor cavity 305, and the top end of the balancing shaft 401 is connected to the loading unit 402, and the axial loading load is realized through the loading unit. A displacement meter 403 is provided on the loading unit 402, and the displacement meter is used to calculate the displacement corresponding to the axial loading load of the hydrate-containing sediment. The lower end of the balancing shaft 401 is located in the reactor cavity 305, and the lower end of the balancing shaft is connected to the pressure plate 404.

[0075] In this embodiment, the pressing plate 404 is in the shape of a circular plate, and a plurality of pressing heads 405 are connected to the bottom of the pressing plate 404, and the pressing heads 405 are arranged at intervals along the circumferential direction of the pressing plate. The top of the pressing head 405 is fixedly connected to the pressing plate 404, and the lower end of the pressing head 405 passes through the through hole on the upper rotating shear box to contact the sample. A top insulating layer 104 is provided between the bottom surface of the pressing head 405 and the upper surface of the sample.

[0076] like Figure 2 As shown, in this embodiment, the pressure head 405 of the axial loading module and the acoustic wave-resistance probe of the acoustic wave-resistance testing module are arranged alternately at intervals. Therefore, the axial loading module in this embodiment includes four pressure heads arranged evenly at intervals, and the acoustic wave-resistance testing module includes four groups of acoustic wave-resistance probes arranged evenly at intervals. The above four pressure heads and four groups of acoustic wave-resistance probes are arranged alternately in sequence along the circumferential direction of the pressing plate.

[0077] In this embodiment, the upper rotating shear box 101 is fixedly connected to the pressing plate 404 through the pressure head 405, that is, the upper rotating shear box 101 is fixedly connected to the pressing plate 404. At the same time, the lower end cover 303 is connected to the pressing plate 404 through a plurality of support rods 406, and the support rods 406 are arranged at intervals along the circumferential direction of the lower end cover. The bottom end of the support rod 406 is fixedly connected to the lower end cover 303, and the upper end of the support rod 406 is slidably connected to the pressing plate 404 through a sliding sleeve 407. The sliding sleeve 407 is fixedly arranged in the pressing plate 404, and the support rod 406 is slidably connected to the sliding sleeve 407. The sliding sleeve can guide the relative sliding between the support rod and the pressing plate, and also reduce the sliding friction between the support rod and the pressing plate.

[0078] Through the fixed connection between the upper rotating shear box and the pressure plate, and the setting of the support rod, a fixed-support combined ring shear structure is realized. Under the ring shear conditions of hydrate-containing sediment samples, this structure can not only ensure that the upper rotating shear box remains relatively stable and does not affect the rotation of the upper rotating shear box, so as to perform ring shear tests on the samples, but also meet the requirements of the up and down movement of the pressure head to apply a specific axial load, thus realizing the axial loading requirements. At the same time, the ring shear structure can also better maintain the stable state of the upper rotating shear box and the lower rotating shear box during the shearing process, which helps to improve the test accuracy of the acoustic wave-resistance probe.

[0079] The rotation drive module mainly provides driving force for the rotating shear box module to perform the ring shear experiment. The module includes a driving motor 501, the output shaft of the driving motor 501 is connected to the input shaft of the reducer 502, the power output shaft of the reducer 502 is connected to the lower end of the straightener 504, and a torque sensor 503 is provided on the power output shaft of the reducer 502. The upper end of the straightener 504 is connected to the lower rotating shear box 102, and the straightener 504 is installed on the fixed plate 505. The rotational power generated by the driving motor 501 during operation is transmitted to the lower rotating shear box 102 through the reducer 502 and the straightener 504 in turn, driving the lower rotating shear box 102 to rotate. During the rotation process, the torque, angle and other parameters are recorded by the torque sensor 503.

[0080] The gas supply module is connected to the high-pressure reactor module through a high-pressure pipeline. The gas supply module includes a gas cylinder 601, which is connected to the fluid channel 309 on the upper end cover through a high-pressure pipeline. The high-pressure pipeline is provided with a valve 602, a pressure sensor 603 and a flow meter 604 in sequence. The gas supply in the hydrate-containing sediment synthesis process is realized through the gas supply module. The pressure sensor and the flow meter realize real-time monitoring and control of the pressure and flow of the gas.

[0081] The temperature control module includes a thermostat 701, and the rotating shear box module and the high-pressure reactor module are both arranged in the thermostat 701. The thermostat 701 is provided with a temperature controller 702. The temperature of the rotating shear box module and the high-pressure reactor module in the thermostat 701 is accurately adjusted by the temperature controller 702, and the temperature is adjusted to a specific temperature as required. During the hydrate synthesis process, the thermostat uses an air bath to reduce the temperature of the sample in the rotating shear box module and maintain it at a specific temperature to ensure that the hydrate in the sediment does not decompose during the ring shear process. After the test process is completed, the temperature of the rotating shear box module is increased by the thermostat to achieve the decomposition of the hydrate.

[0082] The control and data acquisition module includes a data processor 801 and a computer 802. The computer 802 is used to monitor and control the ring shear test of hydrate-containing sediments; and the data processor 801 is used to record and process data during the test.

[0083] The sample used in this embodiment is a mixture of distilled water or deionized water, sodium dodecyl sulfate and a solid filler, wherein the solid filler can be quartz sand, clay, glass balls, etc. The gas used in this embodiment can be methane, carbon dioxide, etc.

[0084] In this embodiment, the inner wall of the upper rotating shear box, the inner wall of the lower rotating shear box, and the bottom surface of the pressure head that are in contact with the sample need to be roughened or installed with anti-slip sheets to prevent slippage between the sample and the upper rotating shear box and the lower rotating shear box during the ring shear test, thereby affecting the accuracy of the ring shear test results.

[0085] The present application also discloses a method for testing using the above-mentioned hydrate sediment large displacement deformation-acoustic-electrical integrated characterization device, and the method comprises the following steps.

[0086] The first step is to check and calibrate the equipment's air tightness.

[0087] After the device is connected, it is filled with nitrogen and the air tightness of the device is checked by system pressure change and leak detection liquid. The axial loading module and the rotation drive module are calibrated to determine the initial longitudinal motion module resistance and rotation module resistance.

[0088] The second step is sample preparation.

[0089] A certain mass of sediment is mixed with a specific amount of deionized water or distilled water, and then placed in layers in the sample chamber of the rotating shear box module and fully compacted. The required amount of water can be calculated based on the target hydrate saturation.

[0090] The third step is axial loading and pre-consolidation.

[0091] According to the target reservoir depth pressure state, the axial loading module load is set, and the sample is axially loaded. During the loading process, the axial stress on the sample reaches the set value and remains unchanged. The loading unit monitors the change of axial stress in real time, and the displacement meter monitors the displacement change of the sample in real time to ensure that it does not exceed the critical value. The loading unit is adjusted to maintain the axial stress value basically constant, and this state is maintained until the consolidation requirements of the hydrate-containing sediments are met.

[0092] Step 4: Hydrate synthesis.

[0093] The effective axial stress applied to the sample is maintained unchanged by the axial loading module. At the same time, the gas supply module is turned on to inject high-pressure methane gas into the reactor chamber through the fluid channel; the refrigeration temperature of the thermostat 701 is set by the temperature controller 702 to cool the sample in the reactor chamber 305, so that the ambient temperature and pressure conditions of the sample meet the hydrate synthesis phase equilibrium conditions and remain unchanged until the synthesis process of the hydrate-containing sediment sample is completed.

[0094] Step 5: Ring shear test.

[0095] The rotation shearing speed is set by driving the motor 501 to drive the lower rotation shearing box 102 to rotate; meanwhile, the upper rotation shearing box 101 fixedly connected to the pressing plate 404 always keeps its original state unchanged. When the lower rotation shearing box 102 rotates and the upper rotation shearing box 101 is stationary, the rotation shearing process of the hydrate-containing sediment sample is simulated.

[0096] During the shearing process, the parameters such as torque and rotation angle are monitored and recorded in real time through the driving motor 501 and the torque sensor 503. When the rotation angle reaches the set value, the driving motor 501 is turned off, the ring shear experiment is stopped, and the changes in the shear stress and shear strain of the sample during the ring shearing process are calculated.

[0097] The calculation formulas of shear stress τ and shear strain γ are expressed as follows:

[0098]

[0099] Where r1 and r2 are the inner and outer diameters of the specimen; h is the height of the specimen, M is the torque, and θ is the angular displacement.

[0100] Step 6: Acoustic wave-resistance combined test.

[0101] The combined acoustic wave and resistance test of hydrate-containing sediments is divided into two parts. In the first part, during the hydrate synthesis process, the acoustic wave and resistance signals of the hydrate-containing sediment sample are detected by the acoustic wave-resistance probe, the water content and hydrate synthesis amount in the hydrate-containing sediment sample are evaluated and analyzed, and it is determined whether the hydrate saturation reaches the predetermined value; in the second part, during the shear process, the acoustic wave and electrical signals of the hydrate-containing sediment sample are detected by the acoustic wave-resistance probe, and the change law of the wave degree or waveform and resistivity during the shear failure of the hydrate-containing sediment sample is analyzed. Combined with the analysis of the fifth step above, the damage and destruction process of the sediment under the ring shear condition is quantitatively evaluated.

[0102] P-wave velocity V in hydrate-bearing sediments p and shear wave velocity V s It can be calculated by the following formula:

[0103]

[0104] Where L is the vertical distance between two probes in the same acoustic wave-resistance probe group before the ring shearing begins; T p0 is the initial longitudinal wave propagation time of the probe; T s0 is the initial shear wave propagation time of the probe; T p is the propagation time of the longitudinal wave in the sediment; T s is the propagation time of shear waves in sediment.

[0105] The plane distance D that the acoustic wave-resistance probe moves during the rotational shear process can be calculated by the following formula:

[0106] D=2sin(α / 2)·r,α≤π,

[0107] The distance L′ between two probes in the same acoustic wave-resistance probe set after rotational shearing can be expressed by the following formula:

[0108]

[0109] Among them, α is the rotation angle of the probe, and r is the distance from the probe to the rotation center.

[0110] Combining the above formulas, it can be seen that the longitudinal and transverse wave velocities of hydrate-containing sediments during the ring shear process can be calculated by the following formula:

[0111]

[0112] Through the above two formulas, as well as the data such as the rotation angle and acoustic wave duration recorded during the ring shear process, the longitudinal wave velocity and acoustic wave velocity of the hydrate-containing sediment sample at any time can be calculated. Combining the wave velocity and waveform, the damage and destruction of the sample under ring shear conditions can be evaluated.

[0113] This method specifically solves the problem of low accuracy in calculating the acoustic wave velocity during the existing ring shear test of hydrate-containing sediments. The derived calculation formula has fewer parameters and is more suitable for calculating the acoustic wave velocity in indoor tests and field applications. It is of great significance for the stability evaluation of hydrate reservoirs and landslide prediction under large deformation conditions.

[0114] In addition, the resistivity σ of hydrate-containing sediments * It can be calculated by the following formula:

[0115]

[0116] Where Z is the complex impedance, l and S are the equivalent geometric parameters of the test sample.

[0117] Step 7: End the experiment and organize the equipment.

[0118] Release the high-pressure gas in the reactor chamber, unload the axial load acting on the sample by adjusting the loading unit, open the high-pressure reactor module and the rotating shear box module, observe the shear surface shape of the sample, disassemble the device and tidy up the equipment.

[0119] Step 8: Experimental data processing and comprehensive analysis of mechanical, acoustic and electrical parameters.

[0120] First, based on the experimental results, the large displacement deformation characteristics and acoustic and electrical response characteristics of hydrate-containing sediments are analyzed to clarify the variation patterns of physical parameters such as shear strength, cohesion, internal friction angle, longitudinal / transverse wave velocity, and resistivity; then, the quantitative relationship between shear strength and acoustic wave velocity is clarified, and the functional relationship between shear strength and longitudinal wave velocity and resistivity is determined, and then a prediction model for shear strength is established. Here, referring to the existing geotechnical mechanics parameter model, the relevant functional relationship is recommended as an option, as shown in the following formula:

[0121] τ f =a1+a2exp(V p / b),

[0122] τ f =s1ln(σ * )+s2,

[0123] In the formula, τ f is the shear stress peak value, a1, a2 and b are model coefficients, which can be determined by fitting the acoustic wave test data; s1 and s2 are model parameters, which can be determined by fitting the resistivity data.

[0124] In summary, based on the mechanical-acoustic-electrical data of hydrate-containing sediments under large displacement deformation, a shear strength prediction model can be established, which closely links the mechanical-acoustic-electrical parameters and can be further applied to subsequent numerical simulation research or guide field engineering applications. This method can not only analyze the shear strength, but also further establish the prediction and evaluation of mechanical parameters such as elastic modulus, cohesion, and internal friction angle, which has important engineering guidance significance.

[0125] The above is a detailed introduction to the large displacement deformation-acoustic-electrical integrated characterization device and method for hydrate sediments under large deformation conditions provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The above description of the disclosed embodiments enables professional and technical personnel in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to professional and technical personnel in this field, and the general principles defined in this article can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown in this article, but will conform to the widest range consistent with the principles and novel features disclosed in this article.

Claims

1. A large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments, comprising a high-pressure reactor module, characterized in that: The rotating shear box module is arranged in the high-pressure reactor module, the rotating shear box module is connected to the acoustic wave-resistance test module, the rotating shear box module comprises an upper rotating shear box and a lower rotating shear box, the upper rotating shear box is connected to the axial loading module, and the lower rotating shear box is connected to the rotation driving module; The axial loading module comprises a pressing plate, on which a plurality of pressing heads are arranged, which are fixedly connected to the upper rotating shear box, and the pressing plate is slidably connected to the high-pressure reactor module via a vertically arranged supporting rod.

2. The large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments according to claim 1 is characterized in that: In the rotary shear box module, the lower surface of the upper rotary shear box contacts the upper surface of the lower rotary shear box, and the lower surface of the upper rotary shear box and the upper surface of the lower rotary shear box are respectively provided with annular grooves, and the annular grooves of the upper rotary shear box and the annular grooves of the lower rotary shear box form an annular sample cavity; An insulating layer is arranged between the sample in the sample cavity and the axial loading module in contact with the sample, the side wall of the upper rotating shear box, and the side wall of the lower rotating shear box.

3. The large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments according to claim 1 is characterized in that: The high-pressure reactor module comprises a high-pressure reactor body, wherein a closed reactor chamber is formed between the high-pressure reactor body, an upper end cover at the top, and a lower end cover at the bottom, and the rotating shear box module is arranged in the reactor chamber; The lower rotating shear box is rotatably connected to the lower end cover, and a sliding sealing ring is provided at the contact surface between the lower rotating shear box and the lower end cover; A fluid channel is provided at the upper end cover, and the connection between the high-pressure reactor module and the gas supply module is realized through the fluid channel. Correspondingly, a plurality of air holes are provided on the upper rotating shear box.

4. The large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments according to claim 1 is characterized in that: The acoustic wave-resistance test module includes an array of acoustic wave-resistance probes spaced apart inside the sample, each group of acoustic wave-resistance probes includes two acoustic wave-resistance probes symmetrically arranged up and down, the upper acoustic wave-resistance probe is a transmitting probe installed in an upper rotating shear box, and the lower acoustic wave-resistance probe is a receiving probe installed in a lower rotating shear box; The outer side of the acoustic wave-resistance probe is wrapped with a protective sleeve, and the protective sleeve is installed in the upper rotating shear box or the lower rotating shear box through an insulating sleeve.

5. The large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments according to claim 3 is characterized in that: The axial loading module also includes a vertically arranged balancing shaft, one end of the balancing shaft located outside the reactor chamber is connected to the loading unit, a displacement meter is provided at the loading unit, one end of the balancing shaft located inside the reactor chamber is fixedly connected to the pressing plate, the balancing shaft passes through the upper end cover, and a balancing chamber and a sealing ring are provided on the contact surface between the balancing shaft and the upper end cover; A plurality of through holes are arranged at intervals on the upper rotating shear box, and the pressure heads are arranged in the through holes correspondingly, and the pressure heads are fixedly connected to the upper rotating shear box; The pressing plate is connected to the lower end cover through a plurality of support rods, the lower ends of the support rods are fixedly connected to the lower end cover, and the upper ends of the support rods are slidably connected to the pressing plate.

6. The large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments according to claim 3 is characterized in that: The high-pressure reactor module is arranged in the temperature control module; The temperature control module includes a constant temperature box and a temperature controller.

7. The large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments according to claim 6 is characterized in that: It also includes a control and data acquisition module, and the data acquisition module is respectively connected with the axial loading module, the rotation driving module, the air supply module, the axial loading module, and the temperature control module.

8. A testing method using the large displacement deformation-acoustic-electrical integrated characterization device for hydrate sediments according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: S1. Prepare a sample using a testing device; S2, axial loading and pre-consolidation, and hydrate synthesis; S3. Performing a ring shear test on the hydrate-containing sediment sample; The rotation driving module drives the lower rotation shear box to rotate, and the state of the upper rotation shear box remains unchanged, so as to simulate the rotation shear process of the hydrated sediment samples in the upper rotation shear box and the lower rotation shear box; S4. Conducting a combined acoustic wave-resistance test on hydrate-containing sediment samples; S5. Arrange the equipment after the experiment. S6. Experimental data processing and comprehensive analysis of mechanical-acoustic-electrical parameters.

9. The test method according to claim 8, characterized in that: In step S1, the sediment and deionized water or distilled water are mixed and stirred, and then placed in layers in the sample cavity of the rotating shear box module and fully compacted; In step S2, the sample is axially loaded by an axial loading module so that the sample meets the consolidation requirements for the synthesis of hydrate-containing sediments; The gas required for hydrate synthesis is injected into the reactor chamber through the gas supply module, and the high-pressure reactor module and the rotating shear box module are refrigerated through the temperature control module to cool the sample in the reactor chamber so that the ambient temperature and pressure conditions of the sample meet the phase equilibrium conditions for hydrate synthesis, thereby realizing the synthesis process of hydrate-containing sediment samples.

10. The test method according to claim 8, characterized in that: In step S3, during the ring shear test, the torque and angle parameters are monitored and recorded in real time through the driving motor and the torque sensor. When the angle reaches the set value, the driving motor is turned off, the ring shear test is stopped, and the changes in the shear stress and shear strain of the sample during the ring shear process are calculated; The calculation formulas of shear stress τ and shear strain γ are respectively expressed as: Where r1 and r2 are the inner and outer diameters of the specimen; h is the height of the specimen, M is the torque, and θ is the angular displacement; In step S4, the longitudinal wave velocity V of the hydrate-containing sediment is p and shear wave velocity V s Calculated by the following formula: Where L is the vertical distance between two probes in the same acoustic wave-resistance probe group before the ring shearing begins; T p0 is the initial longitudinal wave propagation time of the probe; T s0 is the initial shear wave propagation time of the probe; T p is the propagation time of the longitudinal wave in the sediment; T s is the propagation time of shear waves in sediments; The plane distance D that the acoustic wave-resistance probe moves during the rotational shear process can be calculated by the following formula: D=2sin(α / 2)·r,α≤π, The distance L′ between two probes in the same acoustic wave-resistance probe group after rotational shearing can be expressed by the following formula: Among them, α is the rotation angle of the probe; r is the distance from the probe to the rotation center; The calculation formulas for the longitudinal wave velocity and transverse wave velocity of hydrate-containing sediments during the ring shear process are: Resistivity σ of hydrate-bearing sediments * The calculation formula is: Where Z is the complex impedance, l and S are the equivalent geometric parameters of the test sample; In step S6, referring to the quantitative relationship between the strength and acoustic wave velocity of hydrate-containing sediments under small deformation conditions, a strength prediction model based on longitudinal wave velocity / resistivity is established, the mechanical-acoustic-electrical parameters are unified, and the relevant functional relationship is recommended in combination with the existing shear strength prediction in the field of geotechnical engineering, as shown below: τ f =a1+a2exp(V p / b), t f =s1ln(σ * )+s2, Among them, τ f is the peak shear stress, a1, a2 and b are the model coefficients determined by fitting the acoustic wave test data, and s1 and s2 are the model parameters determined by fitting the resistivity data.

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