Deep in-situ rock physics experiment device based on fiber bragg grating

Abstract

The invention relates to the field of deep rock physics in-situ test experiments, and discloses a deep in-situ rock physics experiment device based on a fiber bragg grating. The deep in-situ rock physics experiment device based on the fiber bragg grating comprises a pressure container, the pressure container is provided with a hollow cavity used for containing a rock sample, and the two axial ends of the hollow cavity are provided with a ballast end plug and a measuring end plug which can move in the axial direction respectively; the axial pressure loading module comprises an axial driving piece used for applying axial force to the ballast end plug from the outer side and a pressure sensor axially connected with the outer side of the measuring end plug, and a vibration generating unit is arranged between the axial driving piece and the ballast end plug or between the measuring end plug and the pressure sensor; the detection module comprises a first axial fiber bragg grating sensing element which is attached to the peripheral wall of the rock sample in the axial direction, and the first axial fiber bragg grating sensing element is used for obtaining axial deformation data of the rock sample. The accuracy and the reliability of the dynamic and static elastic parameter measurement experiment of the rock sample can be improved.

Description

Technical Field

[0001] This application belongs to the field of in-situ testing experiments for deep rock physics. Specifically, it relates to a deep in-situ rock physics experimental device based on fiber Bragg grating. Background Art

[0002] In the actual process of seismic exploration and development, the elastic properties and mechanical properties of rocks under in-situ strata are quite important. The static elastic parameters of rocks are crucial for oil and gas exploitation, well and mine evaluation, and hydraulic fracturing; the dynamic elastic parameters can provide very important bases for reservoir quality and fluid detection.

[0003] In existing experimental devices, an acoustic wave source is usually used to vibrate the rock sample, and multiple metal strain gauges or semiconductor strain gauges are pasted to measure the dynamic elastic parameters of the rock sample. The steps are not only cumbersome but also costly. In addition, the existing acoustic wave source is generally arranged in the working cavity. Affected by changes in the working cavity environment, such as high temperature, high pressure, humidity and erosion caused by fluid displacement, the working performance of the acoustic wave source and the metal strain gauges or semiconductor strain gauges will change unpredictably, resulting in inaccurate test data. Summary of the Invention

[0004] The purpose of this application is to provide a deep in-situ rock physics experimental device based on fiber Bragg grating to improve the reliability and accuracy of the dynamic and static elastic parameter measurement experiments of rock samples.

[0005] To achieve the above purpose, this application provides a deep in-situ rock physics experimental device based on fiber Bragg grating. The deep in-situ rock physics experimental device based on fiber Bragg grating includes: A pressure vessel, provided with a hollow cavity for placing a rock sample, and axially movable ballast end plugs and measurement end plugs are respectively arranged at both axial ends of the hollow cavity; An axial compression loading module, including an axial driving member for applying an axial force to the ballast end plug from the outside and a pressure sensor axially connected to the outside of the measurement end plug. A vibration generating unit is provided between the axial driving member and the ballast end plug, or between the measurement end plug and the pressure sensor; A detection module, including a first axial fiber Bragg grating sensing element axially attached to the peripheral wall of the rock sample, and the first axial fiber Bragg grating sensing element is used to obtain the axial deformation data of the rock sample.

[0006] In some embodiments, the axial compression loading module includes a hydraulic cylinder and a hydraulic pump. The piston rod of the hydraulic cylinder is axially connected to the outside of the ballast end plug, and the hydraulic pump is used to supply oil to the hydraulic cylinder.

[0007] In some embodiments, the vibration generating unit includes a piezoelectric ceramic arranged between the piston rod and the ballast end plug. The deep in-situ rock physics experimental device based on fiber Bragg grating further includes: A function generator for generating sinusoidal electrical signals of different frequencies; A power amplifier for amplifying the sinusoidal electrical signal and guiding the amplified sinusoidal electrical signal to a piezoelectric ceramic.

[0008] In some embodiments, the detection module further includes: A laser light source for generating a laser with a periodically varying wavelength; An optoelectronic converter connected to the first axially fiber Bragg grating sensing element through an optical fiber, and the optoelectronic converter is used to convert the optical signal reflected by the first axially fiber Bragg grating sensing element into an electrical signal; A demodulator electrically connected to the optoelectronic converter, and the demodulator is used to demodulate the electrical signal to obtain the deformation data of the first axially fiber Bragg grating sensing element.

[0009] In some embodiments, the detection module further includes a second axially fiber Bragg grating sensing element for axially attaching to the circumferential wall of the ballast end plug, and the laser light source, the second axially fiber Bragg grating sensing element, the optoelectronic converter and the demodulator are connected. The in-situ rock physics experiment device based on fiber Bragg grating further includes a computer configured to: Obtain the axial deformation data of the ballast end plug from the second axially fiber Bragg grating sensing element, and obtain the axial deformation data of the rock sample from the first axially fiber Bragg grating sensing element; Calculate the dynamic Young's modulus of the rock sample according to the axial deformation data of the ballast end plug, the axial deformation data of the rock sample, the preset Young's modulus of the ballast end plug, and the first preset formula; The first preset formula is: , where, is the dynamic Young's modulus of the rock sample, is the axial deformation data of the ballast end plug, is the preset Young's modulus of the ballast end plug, is the axial deformation data of the rock sample.

[0010] In some embodiments, the detection module further includes a circumferential fiber Bragg grating sensing element for circumferentially attaching to the circumferential wall of the rock sample, and the laser light source, the circumferential fiber Bragg grating sensing element, the optoelectronic converter and the demodulator are connected. The computer is further configured to: Obtain the radial deformation data of the rock sample from the circumferential fiber Bragg grating sensing element; Calculate the Poisson's ratio of the rock sample according to the axial deformation data of the rock sample and the radial deformation data of the rock sample and the second preset formula; The second preset formula is: , where, is the Poisson's ratio of the rock sample, is the radial deformation data of the rock sample; Obtain the radial deformation data of the rock sample from the detection module, obtain the axial stress of the rock sample from the pressure sensor, and calculate the static Young's modulus of the rock sample according to the third preset formula; The third preset formula is: , wherein, is the static Young's modulus of the rock sample, is the axial stress of the rock sample.

[0011] In some embodiments, the peripheral wall of the rock sample is wrapped with a rubber sleeve, and the deep in-situ rock physics experimental device based on fiber Bragg grating further includes a confining pressure loading module, and the confining pressure loading module includes a confining pressure loading pump for injecting confining pressure fluid into the rubber sleeve.

[0012] In some embodiments, seepage simulation working channels for communicating with the two axial ends of the rock sample are respectively provided on the ballast end plug and the measurement end plug, and the deep in-situ rock physics experimental device based on fiber Bragg grating further includes a fluid displacement unit, and the fluid displacement unit is used to provide high-pressure fluid to the seepage simulation working channel of one of the ballast end plug and the measurement end plug.

[0013] In some embodiments, seepage simulation working channels for communicating with the two axial ends of the rock sample are respectively provided on the ballast end plug and the measurement end plug, and the vacuum unit is used to evacuate the seepage simulation working channel of one of the ballast end plug and the measurement end plug.

[0014] In some embodiments, the deep in-situ rock physics experimental device based on fiber Bragg grating further includes a temperature control unit for adjusting the temperature of the rock sample, and the temperature control unit includes a heating sleeve for wrapping the pressure vessel and a resistance wire for adjusting the temperature of the heating sleeve.

[0015] Through the above technical solutions, the deep in-situ rock physics experimental device based on fiber Bragg grating provided by the embodiments of the present application has the following beneficial effects: In the technical solution of the present application, the vibration generating unit can be arranged between the axial driving member and the ballast end plug, or between the measuring end plug and the pressure sensor, so that the vibration unit can indirectly drive the rock sample to vibrate through the ballast end plug or the measuring end plug. The setting of the vibration generating unit away from the high temperature, high pressure or humid environment where the rock sample is located ensures the working performance of the vibration generating unit. In addition, the pressure sensor can obtain the axial load applied to the rock by the axial driving member through the ballast end plug. Moreover, since the metal strain gauge or semiconductor strain gauge is vulnerable itself and the required quantity is large, resulting in a high production cost of the rock sample, in the present application, a fiber Bragg grating-based sensing member is used to obtain the axial deformation data of the rock sample. A single fiber Bragg grating sensor can include multiple sensitive members to obtain the strain at different positions of the rock sample, thereby reducing the number of strain gauges required for the rock sample, reducing the workload and difficulty of wiring, and improving the reliability of the detection module in harsh environments. Compared with the method of setting the acoustic wave source in the working cavity in the prior art, the stability and accuracy of the vibration generating unit and the detection module of the present application are better. According to the more stable low-frequency vibration environment and the more accurate measurement results of the pressure sensor and the first axial fiber Bragg grating sensing element, the present application can improve the accuracy and reliability of the dynamic and static elastic parameter measurement experiment of the rock sample.

[0016] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific embodiments section. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings are used to provide a further understanding of the embodiments of the present application, and constitute a part of the specification. They are used together with the following specific embodiments to explain the embodiments of the present application, but do not constitute a limitation to the embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts. In the drawings: Figure 1 is a schematic structural diagram of a fiber Bragg grating-based deep in-situ rock physics experimental device according to a specific embodiment of the present application; Figure 2 is Figure 1 a schematic structural diagram of the rock sample in Figure 3 is an experimental measurement result diagram of the static and dynamic cross-frequency band Young's modulus of dry shale under different confining pressure axial pressures provided by a specific embodiment of the present application; Figure 4 is an experimental measurement result diagram of the static and dynamic cross-frequency band Poisson's ratio of dry shale under different confining pressure axial pressures provided by a specific embodiment of the present application; Figure 5 is a step diagram of a rock sample physical parameter measurement experiment according to a specific embodiment of the present application.

[0018] Description of Reference Numerals DETAILED DESCRIPTION

[0019] The specific implementation of the present application is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present application, and is not used to limit the present application.

[0020] The deep in-situ rock physics experimental device based on fiber Bragg grating according to the present application is described below with reference to the accompanying drawings.

[0021] This application discloses a novel deep in-situ rock physics experimental device based on fiber grating, such as Figure 1 and Figure 2 As shown, a deep in-situ rock physics experimental device based on fiber Bragg grating in a specific embodiment includes: The pressure vessel 100 is provided with a hollow cavity for placing a rock sample R, and axially movable ballast end plugs U and measurement end plugs D are provided at two axial ends of the hollow cavity respectively; The axial pressure loading module includes an axial driving member for applying an axial force to the ballast end plug U from the outside and a pressure sensor 400 axially connected to the outside of the measuring end plug D, and a vibration generating unit 500 is provided between the axial driving member and the ballast end plug U, or between the measuring end plug D and the pressure sensor 400; The detection module 600 includes a first axial fiber Bragg grating sensing element F1 which is axially attached to the peripheral wall of the rock sample R. The first axial fiber Bragg grating sensing element F1 is used to obtain axial deformation data of the rock sample R.

[0022] In the technical solution of the present application, the vibration generating unit 500 can be arranged between the axial driving member and the ballast end plug U, or between the measuring end plug D and the pressure sensor 400, so that after the rock sample is axially compressed, the vibration unit can indirectly drive the rock sample R to vibrate through the ballast end plug U or the measuring end plug D. Since the vibration generating unit 500 is located outside the hollow cavity and away from the high temperature, high pressure or humid environment where the rock sample R is located, the working performance of the vibration generating unit 500 is guaranteed. In addition, the pressure sensor 400 can obtain the axial load applied to the rock by the axial driving member through the ballast end plug U. Moreover, since the metal strain gauge or semiconductor strain gauge is vulnerable itself and the required quantity is large, resulting in a high manufacturing cost of the rock sample R, in the present application, a fiber Bragg grating-based sensing component is used to obtain the axial deformation data of the rock sample R. A single fiber Bragg grating sensor can include multiple sensitive components to obtain the strain at different positions of the rock sample R, thereby reducing the number of strain gauges required for the rock sample R, reducing the workload and difficulty of wiring, and improving the reliability of the detection module 600 in a harsh environment. Compared with the prior art in which the acoustic wave source is arranged in the working cavity, the stability and accuracy of the vibration generating unit 500 and the detection module 600 in the present application are better. According to the more stable low-frequency vibration environment and the more accurate measurement results of the pressure sensor 400 and the first axial fiber Bragg grating sensing element F1, the present application can improve the accuracy and reliability of the dynamic and static elastic parameter measurement experiment of the rock sample R.

[0023] In the present embodiment, as Figure 1 shown, the axial compression loading module includes a hydraulic cylinder 200 and a hydraulic pump 300. The piston rod 210 of the hydraulic cylinder 200 is connected to the axial outer side of the ballast end plug U, and the hydraulic pump 300 is used to supply oil to the hydraulic cylinder 200. Specifically, the axial load required for the rock sample R is large, and the power density of the hydraulic cylinder 200 is high and the anti-impact performance is good, so as to realize the precise control of the axial load of the rock sample R. However, those skilled in the art can understand that the axial compression loading module can also be a driving component such as an electric cylinder, a cylinder, etc., or even a rack and pinion mechanism, etc. These structural forms should also fall within the protection scope of the present application.

[0024] In the present embodiment, as Figure 2 shown, the vibration generating unit 500 includes a piezoelectric ceramic arranged between the piston rod 210 and the ballast end plug U. The deep in-situ rock physics experimental device based on fiber Bragg grating further includes: A function generator for generating sine electrical signals of different frequencies; A power amplifier for amplifying the sine electrical signal and guiding the amplified sine electrical signal to the piezoelectric ceramic.

[0025] The piezoelectric ceramic is arranged to abut between the piston rod 210 and the ballast end plug U. The piezoelectric property of the piezoelectric ceramic enables the piezoelectric ceramic to indirectly drive the rock sample R to vibrate through the ballast end plug U. Specifically, the function generator of the vibration generating unit 500 can generate a sine electrical signal with a frequency between 0 Hz and 10^6 Hz. After being amplified by the power amplifier and directed to the piezoelectric ceramic, the piezoelectric ceramic vibration source can convert the electrical signal into a sine mechanical vibration with the corresponding frequency, thereby indirectly driving the rock sample R to generate the corresponding vibration.

[0026] In this embodiment, the detection module 600 further includes: A laser light source for generating laser light with a periodically changing wavelength; A photoelectric converter connected to the first axial fiber grating sensing element F1 through an optical fiber. The photoelectric converter is used to convert the optical signal reflected by the first axial fiber grating sensing element F1 into an electrical signal; A demodulator electrically connected to the photoelectric converter. The demodulator is used to demodulate the electrical signal to obtain the deformation data of the first axial fiber grating sensing element F1.

[0027] By controlling the change of the driving current of the laser light source, the output optical wavelength can be continuously changed periodically to scan the spectral region of the sensing fiber grating. After the optical signal enters the fiber grating array, due to the wavelength selectivity of the fiber grating, the qualified optical signal is reflected by the grating to the photoelectric converter and generates an electrical signal corresponding to the reflected optical signal. Then, the demodulator demodulates the electrical signal and obtains the deformation data of the fiber grating sensing element. Those skilled in the art can understand that the operator can set additional fiber grating sensitive components to compensate for the temperature to eliminate the influence of the high-temperature environment on the strain measurement.

[0028] Since the force on the ballast end plug U is the same as that on the rock sample R, in this embodiment, as Figure 1 and Figure 2 shown, the detection module 600 further includes a second axial fiber grating sensing element for axially attaching to the peripheral wall of the ballast end plug U. The laser light source, the second axial fiber grating sensing element, the photoelectric converter and the demodulator are connected. The deep in-situ rock physics experimental device based on the fiber grating further includes a computer configured to: Obtain the axial deformation data of the ballast end plug U from the second axial fiber grating sensing element, and obtain the axial deformation data of the rock sample R from the first axial fiber grating sensing element F1; Calculate the dynamic Young's modulus of the rock sample R according to the axial deformation data of the ballast end plug U, the axial deformation data of the rock sample R, the preset Young's modulus of the ballast end plug U and the first preset formula; The first preset formula is: , Where, is the dynamic Young's modulus of rock sample R, is the axial deformation data of the ballast end plug U, is the preset Young's modulus of the ballast end plug U, is the axial deformation data of rock sample R. Specifically, both the first axial fiber Bragg grating sensing element F1 and the second axial fiber Bragg grating sensing element can be four, and are respectively and evenly spaced in sequence on the four sides of the circumferential wall of rock sample R and the ballast end plug U, so as to improve the accuracy of detecting the axial deformation data of the rock sample and the ballast end plug U.

[0029] The first preset formula is applicable to the experiment where rock sample R is in a low-frequency vibration environment, that is, it is necessary to measure the dynamic Young's modulus of rock sample R. In order to better understand the elastic properties of rock sample R, it is also necessary to obtain the Poisson's ratio and the static Young's modulus of rock sample R. In this embodiment, as Figure 2 shown, the detection module 600 further includes a circumferential fiber Bragg grating sensing element F2 that is circumferentially attached to the circumferential wall of rock sample R. The laser light source, the circumferential fiber Bragg grating sensing element F2, the photoelectric converter, and the demodulator are connected. The computer is further configured to: Obtain the radial deformation data of rock sample R from the circumferential fiber Bragg grating sensing element F2; Calculate the Poisson's ratio of rock sample R according to the axial deformation data of rock sample R, the radial deformation data of rock sample R, and the second preset formula; The second preset formula is: , where, is the Poisson's ratio of rock sample R, is the radial deformation data of rock sample R; Obtain the radial deformation data of rock sample R from the detection module, obtain the axial stress of rock sample R from the pressure sensor 400, and calculate the static Young's modulus of rock sample R according to the third preset formula; The third preset formula is: , where, is the static Young's modulus of rock sample R, is the axial stress of rock sample R. In order to ensure the accuracy of the axial deformation data and the radial deformation data of rock sample R obtained by the detection module 600. As Figure 2 shown, multiple pairs of axial strain gauges S1 and circumferential strain gauges S2 can also be arranged on rock sample R as a reference for the fiber Bragg grating sensing element, so as to improve the accuracy of the detection module 600.

[0030] Under different confining pressure environments, the dynamic and static elastic parameters of rock sample R will also change accordingly. In this embodiment, as Figure 1As shown, the peripheral wall of the rock sample R is wrapped with a rubber sleeve 700. The deep in-situ rock physics experimental device based on fiber Bragg grating also includes a confining pressure loading module, and the confining pressure loading module includes a confining pressure loading pump for injecting confining pressure fluid into the rubber sleeve 700. Specifically, an operator can inject the confining pressure fluid (such as pure water, etc.) between the rubber sleeve 700 and the peripheral wall of the rock sample R through a servo pump, and obtain the confining pressure on the rock sample R through a pressure sensor connected to the servo pump, so as to understand how the dynamic and static elastic parameters of the rock sample R change correspondingly under different confining pressure environments. As Figure 3 shown, the deep in-situ rock physics experimental device based on fiber Bragg grating has measured the dynamic Young's modulus of the rock sample under different confining pressures (15 MPa, 10 MPa, 5 MPa) and different frequencies (0 Hz to 10^6 Hz) respectively through strain gauges and Bragg gratings (i.e., fiber Bragg grating sensing elements) for many times, and the measurement results are shown in Figure 3 . (When the frequency is 0 Hz, the dynamic Young's modulus is the static Young's modulus) As Figure 4 shown, the deep in-situ rock physics experimental device based on fiber Bragg grating has measured the Poisson's ratio of the rock sample under different confining pressures (15 MPa, 10 MPa, 5 MPa) and different frequencies (0 Hz to 10^6 Hz) respectively through strain gauges and Bragg gratings (i.e., fiber Bragg grating sensing elements) for many times, and the measurement results are shown in Figure 4 .

[0031] In a real environment, the rocks in the in-situ formation have different liquid saturations. The dynamic and static elastic parameters of the rock sample R with different saturations are also different. In this embodiment, as Figure 1 shown, seepage simulation working channels for communicating with the two axial ends of the rock sample R are respectively provided on the ballast end plug U and the measurement end plug D. The deep in-situ rock physics experimental device based on fiber Bragg grating also includes a fluid displacement unit, and the fluid displacement unit is used to provide high-pressure fluid to the seepage simulation working channel of one of the ballast end plug U and the measurement end plug D. Specifically, a liquid can be pressed into the core of the rock sample R through the seepage simulation working channel of the ballast end plug U by an injection pump to adjust the liquid saturation of the rock sample R. When the liquid flows out from the seepage simulation working channel of the measurement end plug D, it can be judged that the rock sample R is completely saturated, and the injection of the liquid is stopped. Those skilled in the art can understand that in order to obtain the dynamic and static elastic parameters of the rock sample R under different pore pressures, the operator can replace the liquid with gas.

[0032] In a real environment, the core of the rock sample R may also be in a negative pressure state. In this embodiment, as Figure 1As shown, the ballast end plug U and the measurement end plug D are respectively further provided with seepage simulation working channels for communicating with the two axial ends of the rock sample R. The vacuum unit is used to evacuate the seepage simulation working channel of one of the ballast end plug U and the measurement end plug D. In this way, the deep in-situ rock physics experimental device based on fiber Bragg grating of the present application can measure the dynamic and static elastic parameters of the rock sample R under negative pore pressure.

[0033] In the real environment, the dynamic and static elastic parameters of the rock sample R are not only affected by factors such as pore pressure, confining pressure, and liquid saturation, but also the temperature of the rock sample R needs to be considered. In this embodiment, as Figure 1 shown, the deep in-situ rock physics experimental device based on fiber Bragg grating further includes a temperature control unit 800 for adjusting the temperature of the rock sample R. The temperature control unit 800 includes a heating jacket wrapping the pressure vessel 100 and a resistance wire for adjusting the temperature of the heating jacket.

[0034] In summary, the operation steps of the deep in-situ rock physics experimental device based on fiber Bragg grating of the present application can be as Figure 5 shown: S100: Clean, cut, and polish the reservoir rock to prepare the rock sample R; S200: Paste the fiber Bragg grating sensing element on the rock sample R; S300: Adjust the vibration frequency and axial pressure of the rock sample R; S400: Adjust the temperature, pore pressure, confining pressure, and fluid saturation of the rock sample R; S500: Measure the elastic parameters of the rock sample through the detection module.

[0035] Among them, steps S300 and S400 can be executed interchangeably. It should be noted that the confining pressure generated by the servo pump for the rock sample R should not exceed the injection pressure of the injection pump to avoid the liquid being unable to be injected into the core.

[0036] In the description of the present application, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0037] In this application, unless otherwise clearly defined or limited, terms such as "installed", "connected", "coupled", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and may be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0038] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

Claims

1. A deep in-situ rock physics experimental device based on fiber Bragg grating, characterized in that, The deep in-situ rock physics experimental device based on fiber Bragg grating includes: A pressure vessel (100) having a hollow cavity for placing a rock sample (R), and axially movable ballast end plugs (U) and measurement end plugs (D) are respectively provided at both axial ends of the hollow cavity; An axial compression loading module, including an axial driving member for applying an axial force to the ballast end plug (U) from the outside and a pressure sensor (400) axially connected to the outside of the measurement end plug (D), and a vibration generating unit (500) is provided between the axial driving member and the ballast end plug (U) or between the measurement end plug (D) and the pressure sensor (400); A detection module (600), including a first axial fiber Bragg grating sensing element (F1) axially attached to the peripheral wall of the rock sample (R), and the first axial fiber Bragg grating sensing element (F1) is used to obtain axial deformation data of the rock sample (R).

2. The deep in-situ rock physics experimental device based on fiber Bragg grating according to claim 1, characterized in that, The axial compression loading module includes a hydraulic cylinder (200) and a hydraulic pump (300), the piston rod (210) of the hydraulic cylinder (200) is axially connected to the outside of the ballast end plug (U), and the hydraulic pump (300) is used to supply oil to the hydraulic cylinder (200).

3. The deep in-situ rock physics experimental device based on fiber Bragg grating according to claim 2, characterized in that, The vibration generating unit (500) includes a piezoelectric ceramic provided between the piston rod (210) and the ballast end plug (U), and the deep in-situ rock physics experimental device based on fiber Bragg grating further includes: A function generator for generating sinusoidal electrical signals of different frequencies; A power amplifier for amplifying the sinusoidal electrical signals and guiding the amplified sinusoidal electrical signals to the piezoelectric ceramic.

4. The deep in-situ rock physics experimental device based on fiber Bragg grating according to claim 1, wherein The detection module (600) further includes: A laser source for generating a laser with a periodically changing wavelength; An optoelectronic converter connected to the first axial fiber Bragg grating sensing element (F1) through an optical fiber, and the optoelectronic converter is used to convert the optical signal reflected by the first axial fiber Bragg grating sensing element (F1) into an electrical signal; A demodulator electrically connected to the optoelectronic converter, and the demodulator is used to demodulate the electrical signal to obtain deformation data of the first axial fiber Bragg grating sensing element (F1).

5. The deep in-situ rock physics experimental device based on fiber Bragg grating according to claim 4, characterized in that, The detection module (600) further includes a second axial fiber Bragg grating sensing element axially attached to the peripheral wall of the ballast end plug (U), the laser source, the second axial fiber Bragg grating sensing element, the optoelectronic converter and the demodulator are connected, and the deep in-situ rock physics experimental device based on fiber Bragg grating further includes a computer configured to: Obtain axial deformation data of the ballast end plug (U) from the second axial fiber Bragg grating sensing element, and obtain axial deformation data of the rock sample (R) from the first axial fiber Bragg grating sensing element (F1); Calculate the dynamic Young's modulus of the rock sample (R) according to the axial deformation data of the ballast end plug (U), the axial deformation data of the rock sample (R), the preset Young's modulus of the ballast end plug (U) and a first preset formula; The first preset formula is as follows: ,, Among them, is the dynamic Young's modulus of the rock sample (R), is the axial deformation data of the ballast end plug (U), is the preset Young's modulus of the ballast end plug (U), is the axial deformation data of the rock sample (R).

6. The deep in-situ rock physics experimental device based on fiber Bragg grating according to claim 5, characterized in that, The detection module (600) further includes a circumferential fiber Bragg grating sensing element (F2) circumferentially attached to the circumferential wall of the rock sample (R). The laser light source, the circumferential fiber Bragg grating sensing element (F2), the photoelectric converter, and the demodulator are connected. The computer is further configured to: Obtain the radial deformation data of the rock sample (R) from the circumferential fiber Bragg grating sensing element (F2); Calculate the Poisson's ratio of the rock sample (R) according to the axial deformation data and the radial deformation data of the rock sample (R) and a second preset formula; The second preset formula is as follows: ,, wherein, is the Poisson's ratio of the rock sample (R), is the radial deformation data of the rock sample (R); Obtain the radial deformation data of the rock sample (R) from the detection module, obtain the axial stress of the rock sample from the pressure sensor (400), and calculate the static Young's modulus of the rock sample (R) according to a third preset formula; The third preset formula is as follows: , wherein, is the static Young's modulus of the rock sample (R), is the axial stress of the rock sample (R).

7. The deep in-situ rock physics experimental device based on fiber Bragg grating according to claim 6, characterized in that, The circumferential wall of the rock sample (R) is wrapped with a rubber sleeve (700). The deep in-situ rock physics experimental device based on fiber Bragg grating further includes a confining pressure loading module. The confining pressure loading module includes a confining pressure loading pump for injecting confining pressure fluid into the rubber sleeve (700).

8. The deep in-situ rock physics experimental device based on fiber Bragg grating according to any one of claims 1 to 7, characterized in that The ballast end plug (U) and the measurement end plug (D) are respectively further provided with seepage simulation working channels for communicating with the two axial ends of the rock sample (R). The deep in-situ rock physics experimental device based on fiber Bragg grating further includes a fluid displacement unit for providing high-pressure fluid to the seepage simulation working channel of one of the ballast end plug (U) and the measurement end plug (D).

9. The deep in-situ rock physics experimental device based on fiber Bragg grating according to any one of claims 1 to 7, characterized in that, The ballast end plug (U) and the measurement end plug (D) are respectively further provided with seepage simulation working channels for communicating with the two axial ends of the rock sample (R). The vacuum unit is used to evacuate the seepage simulation working channel of one of the ballast end plug (U) and the measurement end plug (D).

10. The deep in-situ rock physics experimental device based on fiber Bragg grating according to any one of claims 1 to 7, characterized in that, The deep in-situ rock physics experimental device based on fiber Bragg grating further includes a temperature control unit (800) for adjusting the temperature of the rock sample (R). The temperature control unit (800) includes a heating jacket wrapping the pressure vessel (100) and a resistance wire for adjusting the temperature of the heating jacket.

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