Physical simulation experimental device and method for fine exploration of water-bearing sections in underground rock strata

Abstract

This invention provides a physical simulation experimental device and method for fine exploration of water-bearing sections in underground rock strata. The device includes a water storage tank connected to a water pump. The water pump is connected to one end of multiple water supply valves via a one-way valve. Each water supply valve has a corresponding rock chamber at its other end. These rock chambers are vertically mounted on the sidewall of a simulated borehole pipe. Flange end caps are installed at both ends of the simulated borehole pipe. A return water inlet sealing head is installed on the flange end cap at the tail end of the simulated borehole pipe. The return water inlet sealing head is connected to the water storage tank via a return water valve. An energy storage and voltage regulator is also installed between the water storage tank and one end of the multiple water supply valves. An armored optical fiber cable for acoustic wave sensing is coaxially installed inside the simulated borehole pipe. This invention can effectively simulate various geological and hydrological conditions in actual underground rock strata environments. By analyzing the variation patterns of acoustic signals, it improves the accuracy of exploration of water-bearing sections, providing reliable technical support for coal mine water hazard prevention and safe production.

Description

Technical Field

[0001] This invention belongs to the field of hydrogeological exploration technology, and relates to aquifer detection, specifically to a physical simulation experimental device and method for fine exploration of aquifer sections in underground rock strata. Background Technology

[0002] In coal mining, the exploration of relatively water-rich sections of aquifers in the roof and floor (underground strata) of coal seams is crucial for ensuring safe production. However, existing exploration methods are significantly inadequate in terms of accuracy, efficiency, and cost, making it difficult to cope with increasingly complex mining environments, especially in critical areas such as the Jurassic coalfields in western China. The roofs of coal seams in this region typically possess unique geological characteristics such as high porosity, well-developed microfractures, and thick sandstone layers, leading to a high risk of water inrush during mining and seriously threatening safe production. Traditional hydrogeological exploration methods, such as core logging and pumping tests, while providing macroscopic geological parameters, are limited in accurately exploring relatively water-rich sections and cannot meet the high-precision requirements of modern mine water control measures such as interception and drainage projects, thus affecting safe and efficient mining.

[0003] To address this issue, the development of Distributed Acoustic Sensing (DAS) technology in recent years has provided a new solution for the precise exploration of aquifers in underground rock strata. DAS technology uses fiber optic sensors to achieve real-time monitoring of continuous acoustic signals over a large area, offering advantages such as high spatial resolution, strong real-time performance, and low cost. It can accurately capture minute acoustic signals caused by groundwater flow and changes in geological structure, thereby detecting relatively water-rich sections in underground rock strata. Compared with traditional exploration methods, DAS technology has significant advantages in monitoring range and sensitivity, making it particularly suitable for exploring relatively water-rich sections and preventing water hazards in complex geological environments. It can significantly improve the accuracy of detecting relatively water-rich sections and the response speed of water hazard prevention. Simultaneously, DAS technology provides reliable data support for the dynamic management of mine water control and intelligent mining in mining areas, helping to optimize mine water control measures, such as the design of water interception and drainage projects, reducing the risk of water inrush in mining areas, and ensuring the safety of miners.

[0004] Although DAS technology has shown great potential in exploring relatively water-rich sections of aquifers, most existing studies rely on field test data, which brings many difficulties in practical operation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a physical simulation experimental device and method for fine exploration of water-bearing sections in underground rock strata, thereby solving the technical problem that existing exploration methods rely on field test data, resulting in a need for further improvement in the accuracy of exploration of water-bearing sections.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A physical simulation experimental device for fine exploration of water-bearing sections in underground rock strata includes a water storage tank connected to a water pump. The water pump is connected to one end of multiple water supply valves via a one-way valve. The other end of each water supply valve is connected to a rock chamber. The multiple rock chambers are vertically installed on the side wall of the simulated borehole pipe.

[0008] The simulated borehole pipe is equipped with flange end caps at both ends. A return water port sealing head is installed on the flange end cap at the tail end of the simulated borehole pipe. The return water port sealing head is connected to the water storage tank for water return through a return water valve.

[0009] The rock chamber includes a hollow rock chamber body, with a rock chamber cap installed at the top of the rock chamber body, and the rock chamber cap is connected to the water supply valve; the bottom of the rock chamber body is detachably installed with the top of a hollow connector, the bottom of the connector is connected to the side wall of the simulated borehole pipe, and a replaceable water outlet plate is installed inside the connector, with a simulated water outlet through the middle of the water outlet plate; the cavity between the water outlet plate, the connector, the rock chamber body and the rock chamber cap is a lithological simulation cavity.

[0010] An energy storage and voltage stabilizer is also installed between the water storage tank and one end of the multiple water supply valves.

[0011] An acoustic wave sensing armored optical cable is coaxially installed inside the simulated borehole pipe, with both ends of the acoustic wave sensing armored optical cable extending out of the flange end caps at both ends of the simulated borehole pipe.

[0012] Each water supply valve and the high-pressure pipeline between the rock chamber is equipped with a liquid turbine flow meter and a pressure transmitter.

[0013] The present invention also has the following technical features:

[0014] The energy storage voltage regulator includes multiple energy storage devices, each including an energy storage tank. The energy storage tank is equipped with an energy storage tank inlet valve, an energy storage tank drain valve, and an overflow valve connected in parallel. A pressure gauge is installed between the energy storage tank and the overflow valve.

[0015] The energy storage voltage regulator also includes a first electromagnetic flow valve and a second electromagnetic flow valve connected in parallel. One end of the first electromagnetic flow valve and one end of the second electromagnetic flow valve are both connected to one end of the plurality of water supply valves. The other end of the first electromagnetic flow valve is connected to the inlet valve of the energy storage tank of the first group of parallel energy storage devices. The drain valve and overflow valve of the energy storage tank of the first group of parallel energy storage devices are connected to the water storage tank. The other end of the second electromagnetic flow valve is connected to the inlet valve of the energy storage tank of the second group of parallel energy storage devices. The drain valve and overflow valve of the energy storage tank of the second group of parallel energy storage devices are connected to the water storage tank.

[0016] One end of the first electromagnetic flow valve and one end of the second electromagnetic flow valve are both connected to one end of the same drain valve, and the other end of the drain valve is connected to the water storage tank.

[0017] It also includes a hydrodynamic parameter acquisition system, which includes a computer terminal. The computer terminal is connected to an analog signal acquisition board via a 485 to USB communication module. The analog signal acquisition board is connected to a 24V power supply module. The analog signal acquisition board is also connected to a liquid turbine flow meter and a pressure transmitter to acquire signals. The liquid turbine flow meter and the pressure transmitter are also connected to the 24V power supply module for power.

[0018] The water pump mentioned is a reciprocating plunger pump.

[0019] The rock chambers are three in number, located at distances of 12.64–12.83 m, 18.47–18.66 m, and 20.54–20.73 m from the beginning of the simulated borehole pipe, respectively.

[0020] The aforementioned acoustic sensing armored optical cable is connected to the flange end cap via an optical fiber sealing head.

[0021] The aforementioned acoustic wave sensing armored optical cable is connected to the distributed acoustic wave sensing system.

[0022] This embodiment protects a physical simulation experimental method for fine exploration of water-bearing sections in underground rock strata, characterized in that the physical simulation experimental method adopts the physical simulation experimental device for fine exploration of water-bearing sections in underground rock strata as described above.

[0023] The sandstones filled in the lithological simulation cavity are fine-grained sandstone, medium-grained sandstone, coarse-grained sandstone, or conglomerate.

[0024] The simulated water outlet is circular or square in shape, and the inner diameter of the circular simulated water outlet is 3mm, 5mm, 7mm or 9mm.

[0025] Compared with the prior art, the present invention has the following technical effects:

[0026] (I) This invention simulates the acoustic wave generation and propagation environment under complex conditions such as varying flow velocities, lithology, and outlet sizes, and combines this with advanced distributed acoustic sensing (DAS) technology to achieve accurate identification of relatively water-rich sections within thick aquifers. This technology can effectively simulate various geological and hydrological conditions in actual underground rock environments, and by analyzing the variation patterns of acoustic signals, it improves the accuracy of detecting water-rich sections, providing reliable technical support for coal mine water hazard prevention and safe production.

[0027] (II) This invention breaks through the technical bottlenecks of traditional hydrogeological exploration methods. Traditional exploration of water-rich sections in the roof of coal mines typically relies on methods such as drilling, geophysical exploration, and geological analysis. However, these methods often suffer from insufficient accuracy, long processing times, and significant susceptibility to environmental influences, especially under complex groundwater conditions. To address this technical bottleneck, this invention provides a multi-condition simulation experimental device that simulates the complex hydrodynamic environment of actual underground aquifers by controlling multiple key factors such as flow velocity, lithology, and outlet size. This innovation overcomes the limitations of traditional exploration methods, providing a more precise and flexible exploration approach for coal mine water hazard prevention.

[0028] (III) Precise Control of the Simulated Water Flow and Sound Wave Propagation Environment. Another innovation of this invention lies in the precise adjustment function of the hydrodynamic control system, particularly in simulating the dynamic changes of water flow under different flow velocities and lithological conditions. The experimental setup, combined with the dynamic environment of sound wave propagation, simulates the flow pattern of groundwater in real time through precise control of multiple parameters such as water pressure, flow velocity, and outlet size. This precise control based on the experimental simulation environment enables this invention to effectively reproduce the real conditions of underground aquifers, solving the problem of data deviation caused by unstable experimental conditions in traditional technologies.

[0029] (IV) This invention utilizes Distributed Acoustic Sensing (DAS) technology for hydrodynamic and lithological analysis. This invention achieves high-precision acquisition and real-time analysis of acoustic signals through DAS technology. DAS technology can sense minute vibration changes via optical fibers, thus accurately capturing the influence of water flow changes, lithological differences, and outlet conditions on acoustic wave propagation. This technique not only solves the problem of insufficient sensitivity in traditional acoustic detection but also significantly improves the identification accuracy of water-rich strata in coal mine roofs, providing strong data support for flood prevention and control.

[0030] (V) This invention realizes experimental data and model inversion technology under multivariate conditions. During the experiment, the experimental conditions are gradually adjusted by combining multiple variables (such as sandstone grain size, flow rate, and outlet size), and the hydrodynamic model is inverted using real-time acquired acoustic signals. This innovative experimental design enables the acquisition of comprehensive hydrogeological data under multiple experimental conditions, thereby further improving the detection accuracy of water-rich strata. This acoustic signal inversion-based analysis method has strong adaptability and universality and can be applied to the exploration of other types of underground aquifers.

[0031] (VI) This invention features an adjustable outlet design. The simulated water flow drilling device designed in this invention, through interchangeable outlets, can simulate outlets of different shapes (such as circles, squares, and rectangles) and sizes, thus reproducing a variety of different groundwater flow environments. Each outlet shape and size can generate different water flow patterns, enabling the experimental device to conduct simulation experiments in a wider range of hydrological environments, thereby improving the adaptability of the experiment and the diversity of experimental data. This design breaks through the limitations of fixed outlet sizes in traditional experimental devices, possessing greater application scalability.

[0032] (VII) This invention enables an intelligent hydrodynamic and acoustic signal monitoring system. The hydrodynamic control system of this invention is combined with a distributed acoustic sensing system to form an intelligent monitoring and data analysis platform. Through data interaction between high-precision flow meters, pressure sensors, and the DAS system, the system can monitor changes in hydrodynamic parameters in real time during experiments and analyze acoustic signals through a signal processing system to deduce the relevant characteristics of groundwater flow. This system not only improves the accuracy of data acquisition but also enables automated data storage and analysis, greatly improving the efficiency and reliability of experiments.

[0033] (VIII) This invention features a highly integrated and modular design. The experimental device of this invention adopts a highly integrated and modular design concept, allowing users to freely combine and adjust various modules (such as the rock chamber (4), water outlet, hydrodynamic control system, acoustic sensor, etc.) according to experimental needs, thereby adapting to the exploration needs of different types of groundwater layers. This flexible configuration design makes the device highly expandable and applicable, and can be widely used in groundwater hydrogeological exploration tasks of different scales and types.

[0034] (IX) This invention not only proposes several novel design concepts for traditional hydrogeological exploration equipment, but also solves the problems of low exploration accuracy and poor environmental adaptability commonly found in existing technologies through multi-condition experimental simulation methods and advanced acoustic technology. This invention has great application potential and market prospects in fields such as coal mine water hazard prevention and water resource utilization, and hydrogeological exploration, significantly improving the exploration accuracy of water-rich strata in coal mine roofs and providing reliable technical support for efficient, safe, and sustainable coal mining. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall connection relationship of the simulation device for detecting the water-bearing capacity of sandstone aquifers.

[0036] Figure 2 This is a schematic diagram of the rock chamber.

[0037] Figure 3 This is a schematic diagram of the energy storage device.

[0038] Figure 4 It is a schematic diagram of the working principle of the energy storage voltage stabilizer.

[0039] Figure 5 It is a schematic diagram of the principle of the hydrodynamic parameter acquisition system.

[0040] The meanings of each label in the figure are as follows: 1 - water storage tank, 2 - water pump, 3 - check valve, 4 - rock chamber, 5 - simulated drilling pipe, 6 - flange end cover, 7 - return water port sealing head, 8 - return water valve, 9 - energy storage voltage stabilizer, 10 - acoustic wave sensing armored optical cable, 11 - optical fiber sealing head, 12 - hydrodynamic parameter acquisition system, 13 - water supply valve, 14 - high-pressure pipeline, 15 - distributed acoustic wave sensing system.

[0041] 401 - rock chamber main body, 402 - rock chamber cap, 403 - connector, 404 - water outlet plate, 405 - simulated water outlet, 406 - lithology simulation cavity.

[0042] 901 - energy storage device, 902 - first electromagnetic flow valve, 903 - second electromagnetic flow valve, 904 - drain valve.

[0043] 90101 - energy storage tank, 90102 - energy storage tank inlet valve, 90103 - energy storage tank drain valve, 90104 - overflow valve, 90105 - pressure gauge.

[0044] 1201 - computer terminal, 1202 - 485 to USB communication module, 1203 - analog signal acquisition board, 1204 - 24V power module, 1205 - liquid turbine flowmeter, 1206 - pressure transmitter.

[0045] The following further elaborates on the specific content of the present invention in combination with embodiments. Specific Embodiments

[0046] It should be noted that all the devices and methods in the present invention, unless otherwise specified, all adopt the devices and methods known in the prior art.

[0047] In the present invention, the thickness range of the extremely thick aquifer is 200m to 500m and above.

[0048] In the present invention, the relatively water-rich layer is divided according to the magnitude of the unit water inflow q: q > 10 L / (s·m) is extremely strong water-richness; 1 < q < 10 L / (s·m) is strong water-richness; 0.1 < q < 1 L / (s·m) is medium water-richness; 0.01 < q < 0.1 L / (s·m) is weak water-richness: q < 0.01 L / (s·m) is extremely weak water-richness.

[0049] To achieve precise exploration of thick aquifers in underground rock strata, it is urgently necessary to establish a physical device for simulation experiments under controlled conditions. This device should be able to simulate the water outflow conditions under different flow rates, lithologies, and outlet sizes, thereby studying the relationship between acoustic signals and the outflow velocity / flow rate of the aquifer's water-rich sections, and constructing an accurate mathematical model of flow rate and acoustic characteristics based on this. The application of this physical simulation experimental device can effectively improve the accuracy of DAS technology in exploring relatively water-rich sections of thick underground aquifers, providing a reliable theoretical basis and technical support for future field applications.

[0050] Therefore, developing a physical simulation experimental device and a method for exploring water-rich strata that combines DAS technology can not only compensate for the shortcomings of traditional technologies but also meet the demand for high-precision exploration technology in coal mine safety production. This innovative technology will provide strong technical support for the prevention and control of water hazards in thick rock aquifers and has broad practical application prospects, providing important support for efficient, safe, and sustainable coal mining.

[0051] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0052] Example 1:

[0053] This embodiment provides a physical simulation experimental device for fine exploration of water-bearing sections in underground rock strata, such as... Figure 1 As shown, it includes a water storage tank 1, which is connected to a water pump 2. The water pump 2 is connected to one end of a plurality of water supply valves 13 through a one-way valve 3. The other end of each water supply valve 13 is connected to a rock chamber 4. The plurality of rock chambers 4 are vertically installed on the side wall of the simulated borehole pipe 5.

[0054] like Figure 1 As shown, flange end caps 6 are installed at both ends of the simulated borehole pipe 5. A return water port sealing head 7 is installed on the flange end cap 6 at the tail end of the simulated borehole pipe 5. The return water port sealing head 7 is connected to the water storage tank 1 through the return water valve 8 for water return.

[0055] like Figure 2 As shown, the rock chamber 4 includes a hollow rock chamber body 401, with a rock chamber cap 402 installed at the top of the rock chamber body 401. The rock chamber cap 402 is connected to the water supply valve 13. The bottom end of the rock chamber body 401 is detachably installed with the top end of a hollow connector 403. The bottom end of the connector 403 is connected to the side wall of the simulated borehole pipe 5. A replaceable water outlet plate 404 is installed inside the connector 403. A simulated water outlet 405 is provided through the middle of the water outlet plate 404. The cavity between the water outlet plate 404, the connector 403, the rock chamber body 401, and the rock chamber cap 402 is a lithological simulation cavity 406.

[0056] like Figure 1 As shown, an energy storage voltage regulator 9 is also installed between the water storage tank 1 and one end of the multiple water supply valves 13.

[0057] like Figure 1 As shown, an acoustic wave sensing armored optical cable 10 is coaxially installed inside the simulated borehole pipe 5, and both ends of the acoustic wave sensing armored optical cable 10 extend out of the flange end caps 6 at both ends of the simulated borehole pipe 5.

[0058] like Figure 4 As shown, a liquid turbine flow meter 1205 and a pressure transmitter 1206 are respectively installed on the high-pressure pipeline 14 between each water supply valve 13 and the rock chamber 4.

[0059] In this embodiment, the various devices are mainly connected via high-pressure pipeline 14. The maximum pressure-bearing capacity of high-pressure pipeline 14 is 34 MPa, which meets the pressure requirements under different experimental conditions.

[0060] In this embodiment, the water storage tank 1 is used to store the water required for the experiment, ensuring a continuous supply of water.

[0061] As a preferred embodiment, the water pump 2 is a reciprocating plunger pump. In this embodiment, the reciprocating plunger pump is used to provide hydrodynamic force for the experiment, and can maintain the uniformity of water flow under different flow rate conditions, ensuring a smooth transition from low flow rate to high flow rate.

[0062] As a preferred embodiment, there are three rock chambers 4, which are respectively placed at distances of 12.64-12.83m, 18.47-18.66m and 20.54-20.73m from the beginning of the simulated borehole pipe 5.

[0063] In this embodiment, rock chamber 4 is used to simulate the acoustic response of groundwater flow under different lithological conditions. Rock chamber 4 has an outer diameter of 80 mm, an inner diameter of 54 mm, and a length of 130 mm, and is made of 20# steel pipe.

[0064] In this embodiment, the water outlet plate 404 is made of 20# steel pipe, the diameter of the circular simulated water outlet 405 is 3-9mm, and the side length of the square simulated water outlet 405 is 3-12mm. Different shapes and sizes of water outlets can generate different hydrodynamic sound waves. The water outlet conditions under actual working conditions are simulated by using simulated water outlets 405 of different shapes and sizes.

[0065] In this embodiment, different sandstones can be loaded inside the lithology simulation cavity 406 to simulate different lithologies.

[0066] In this embodiment, the simulated borehole pipe 5 is used to reproduce the flow of groundwater under different flow velocities, lithologies, and outlet conditions, accurately reproducing the hydrodynamic environment in an actual borehole. The simulated borehole pipe 5 is made of 20# stainless steel, with a diameter of 177.8 mm and a total length of 30.56 meters. It is composed of thirty-one 0.95-meter and three 0.2-meter steel pipes connected by threads. The total length of 30.56 meters for the simulated borehole pipe 5 avoids the influence of sound wave reflections at both ends on the acoustic measurement of the outlet if the simulated borehole is too short.

[0067] As one specific solution in this embodiment, such as Figure 3 As shown, the energy storage regulator 9 includes multiple energy storage devices 901. Each energy storage device 901 includes an energy storage tank 90101. An energy storage tank inlet valve 90102, an energy storage tank drain valve 90103, and an overflow valve 90104 are installed in parallel on the energy storage tank 90101. A pressure gauge 90105 is installed between the energy storage tank 90101 and the overflow valve 90104.

[0068] like Figure 4 As shown, the energy storage regulator 9 also includes a first electromagnetic flow valve 902 and a second electromagnetic flow valve 903 connected in parallel. One end of the first electromagnetic flow valve 902 and one end of the second electromagnetic flow valve 903 are both connected to one end of a plurality of water supply valves 13. The other end of the first electromagnetic flow valve 902 is connected to the inlet valve 90102 of the energy storage tank of the first group of parallel energy storage devices 901. The drain valve 90103 and overflow valve 90104 of the energy storage tank of the first group of parallel energy storage devices 901 are connected to the water storage tank 1. The other end of the second electromagnetic flow valve 903 is connected to the inlet valve 90102 of the energy storage tank of the second group of parallel energy storage devices 901. The drain valve 90103 and overflow valve 90104 of the energy storage tank of the second group of parallel energy storage devices 901 are connected to the water storage tank 1.

[0069] Further preferred, such as Figure 4 As shown, one end of the first electromagnetic flow valve 902 and one end of the second electromagnetic flow valve 903 are both connected to one end of the same drain valve 904, and the other end of the drain valve 904 is connected to the water storage tank 1. The drain valve 904 is used to control the discharge of the remaining water in the energy storage regulator 9 after the experiment.

[0070] In this embodiment, the energy storage regulator 9 is used to maintain the stability of the water flow pressure and avoid water pressure fluctuations affecting the flow rate and experimental results. The energy storage regulator 9 simulates the hydrodynamic condition control link, realizing the initial hydrodynamic conditions of stable water pressure and flow rate in the early stage of the experiment, avoiding the impact of water pressure fluctuation pulses caused by the rapid increase and decrease of water pump 2 on the flow rate and experimental results, as well as the hydrodynamic conditions of a stable decrease in water flow rate in the later stage of the experiment.

[0071] In this embodiment, the capacity of the energy storage tank 90101 is 100L.

[0072] As a further preferred embodiment, such as Figure 5 As shown, it also includes a hydrodynamic parameter acquisition system 12, which includes a computer terminal 1201. The computer terminal 1201 is connected to an analog signal acquisition board 1203 via a 485 to USB communication module 1202. The analog signal acquisition board 1203 is connected to a 24V power supply module 1204. The analog signal acquisition board 1203 is also connected to a liquid turbine flow meter 1205 and a pressure transmitter 1206 to acquire signals. The liquid turbine flow meter 1205 and the pressure transmitter 1206 are also connected to the 24V power supply module 1204 for power.

[0073] In this embodiment, the computer terminal 1201, the 485 to USB communication module 1202, the analog signal acquisition board 1203, and the 24V power supply module 1204 are all devices known in the art.

[0074] As a preferred embodiment of this invention, such as Figure 1 As shown, the acoustic wave sensing armored optical cable 10 is connected to the flange end cover 6 through the optical fiber sealing head 11.

[0075] In this embodiment, the acoustic wave sensing armored optical cable 10 is used for acoustic wave sensing. It adopts a high-precision steel tube armored optical cable to ensure the stability and low noise of signal transmission. The use of a high-performance and durable armored optical cable reduces the maintenance frequency and cost, thereby improving the overall reliability and service life of the system.

[0076] As a preferred embodiment of this invention, such as Figure 1 As shown, the acoustic wave sensing armored optical cable 10 is connected to the distributed acoustic wave sensing system 15.

[0077] In this embodiment, the distributed acoustic wave sensing system 15 adopts a distributed acoustic wave sensing system known in the art. The distributed acoustic wave sensing system 15 is used to collect acoustic wave signals generated by the simulated water flow in the borehole in real time, analyze the acoustic wave signals in real time, extract acoustic wave features and invert flow data, and display the acoustic wave signals and related data in real time.

[0078] Example 2:

[0079] This embodiment provides a physical simulation experimental method for fine exploration of water-bearing sections in underground rock strata. This physical simulation experimental method uses the physical simulation experimental device for fine exploration of water-bearing sections in underground rock strata given in Embodiment 1.

[0080] In this embodiment, the indoor simulation experiment is a key step in verifying the concept and performance of DAS in the water-rich sections of underground sandstone aquifers. This embodiment designs a flow rate variation simulation experiment to simulate the sound wave propagation environment under different flow velocities in the underground aquifer.

[0081] In this embodiment, the flow rate of water into the simulated borehole is controlled by adjusting the injection pressure. The length of the acoustic sensing armored optical cable 10 is 140m, the length of the simulated borehole pipe 5 is 30.56m, the simulated water outlet 405 is at 87m of the optical fiber, and the simulated borehole pipe 5 is between 68.34m and 98.9m of the optical fiber.

[0082] In this example, an initial pressure of 4 MPa and an initial flow rate of 1 m³ / s were used. 3 / h, stop flow 0.1m 3 / h, to simulate the effluent acoustic waves under different flow rates in a steady state.

[0083] In this embodiment, four different types of sandstone are used: fine-grained sandstone, medium-grained sandstone, coarse-grained sandstone, and conglomerate, to simulate the outflow acoustic waves under different lithological aquifer conditions.

[0084] In this embodiment, four different sizes of circular simulated water outlets 405 are used, with inner diameters of φ=3mm, φ=5mm, φ=7mm and φ=9mm, respectively, to simulate the water outlet sound waves under different outlet size conditions.

[0085] In this embodiment, after each replacement of the simulated outlet 405, various different sandstones designed for the experiment are simulated sequentially, and data collection is required for each sandstone under multiple flow rate conditions. This process ensures the completeness of experimental data under each combination of outlet, sandstone, and flow rate conditions, facilitating a comprehensive analysis of the acoustic wave generation and propagation characteristics of relatively water-rich sections in the aquifer, and establishing an accurate flow rate model.

[0086] Specifically, this physical simulation experimental method includes the following experimental steps:

[0087] Step 1: Start the monitoring system:

[0088] Turn on the distributed acoustic wave sensing system 15 (i.e., the DAS system) and set the acquisition parameters, such as the sampling frequency, sampling interval, and data storage length. In this embodiment, the acquisition mode is differential data, the sampling frequency is 4kHz, the sampling interval is 0.5 meters, and the single data storage duration is 30 seconds.

[0089] Simultaneously, the hydrodynamic parameter acquisition system 12 is activated, and the unit of flow rate and sampling frequency are set. In this embodiment, the unit of flow rate is m³ / h, and the acquisition frequency is 1Hz.

[0090] The system time of the synchronous hydrodynamic parameter acquisition system 12 and the distributed acoustic wave sensing system 15 is synchronized to achieve effective data comparison and analysis.

[0091] Step 2, set up the simulated water outlet:

[0092] Install the first type of water outlet plate 404 with simulated water outlet 405 (e.g., circular with a diameter of 3mm) at the bottom of the lithology simulation chamber 406 of the rock chamber 4, ensuring that the installation is firm, and install a screen at the simulated water outlet 405 to prevent sandstone particles from entering the simulated borehole pipe 5, thus ensuring the reliability and continuity of the experiment.

[0093] Step 3, filling with the first type of sandstone:

[0094] Select sandstone of the desired grain size for the first experiment (such as fine-grained sandstone) and fill it evenly into the lithology simulation chamber 406, ensuring that the sandstone is packed tightly and evenly distributed to avoid experimental errors caused by uneven sandstone filling. Connect the connector 403 of the rock chamber 4 to the simulated borehole pipe 5. The rock chamber cap 402 of the rock chamber 4 is connected to the water supply valve 13 through the high-pressure pipe 14 to ensure accurate simulation of experimental conditions.

[0095] Step 4, Water Injection and Pressure Stabilization:

[0096] Start water pump 2 to fill rock chamber 4 and simulated borehole pipe 5 with water through water supply valve 13, then close all water supply valves 13. Water storage tank 1 fills the energy storage regulator 9 with water through water pump 2 and check valve 3 until the maximum experimental pressure is reached (e.g., 1MPa, 2MPa, 3MPa, 4MPa), then turn off water pump 2.

[0097] Open the return water valve 8 and the supply water valve 13 to inject water into the rock chamber 4 and the simulated borehole pipe 5 through the energy storage regulator 9. Control the initial water injection flow rate by adjusting the supply water valve 13, such as setting it to 1m 3 / h, using the energy storage regulator 9 to ensure that the acoustic signal is collected with high quality under stable flow conditions.

[0098] Step 5, Data Collection:

[0099] From an initial stable flow rate, such as 1m 3 / h, start collecting data until the minimum flow rate designed for the flow experiment is reached, such as 0.1m. 3 After / h, data collection will stop.

[0100] Step Six: Replace with other sandstone:

[0101] Replace the sandstone with a second type using the same method as in step three. In this example, the sandstone is medium-grained sandstone. Then repeat steps four and five.

[0102] Replace the sandstone with a third type using the same method as in step three. In this example, the third type is coarse-grained sandstone. Then repeat steps four and five.

[0103] Replace the sandstone with a fourth type using the same method as in step three. In this example, the sandstone is conglomerate. Then repeat steps four and five.

[0104] Step 7: Replace with other simulated water outlets:

[0105] Replace the second type of simulated water outlet 405 with a circular simulated water outlet 405 with a diameter of 5mm using the same method as in step two, and repeat steps three to six.

[0106] Replace the third type of simulated water outlet 405 with a circular simulated water outlet 405 with a diameter of 7mm using the same method as in step two, and repeat steps three through six.

[0107] Replace the third type of simulated water outlet 405 with a circular simulated water outlet 405 with a diameter of 9mm using the same method as in step two, and repeat steps three through six.

[0108] If it is necessary to test simulated water outlets of other shapes (such as squares or rectangles), further experiments should be conducted according to the experimental objectives.

[0109] Step 8: Shut down the device and data processing:

[0110] After the experiment, close the water supply valve 13 and the return valve 8, shut down the hydrodynamic parameter acquisition system 12, and shut down the distributed acoustic wave sensing system 15 to ensure safe shutdown of the equipment. Then, drain the remaining water in the energy storage and voltage regulator 9 through the drain valve 904 and thoroughly clean the equipment to ensure its normal operation in subsequent experiments.

[0111] Next, all collected acoustic data were analyzed in detail. Sensitive acoustic characteristics related to aquifers were extracted by combining different flow rates, sandstone conditions, and simulated outlet conditions. Finally, a mathematical model between acoustic data and flow rate changes was established and validated, thereby improving the accuracy and reliability of exploring aquifers in underground rock formations.

Claims

1. A physical simulation experimental device for fine exploration of aquifer sections in underground rock strata, comprising a water storage tank (1) connected to a water pump (2), characterized in that, The water pump (2) is connected to one end of multiple water supply valves (13) through a check valve (3), and the other end of each water supply valve (13) is connected to a rock chamber (4) in a corresponding manner. Multiple rock chambers (4) are vertically installed on the side wall of the simulated borehole pipe (5). The simulated drilling pipe (5) is equipped with flange end caps (6) at both ends. A return water sealing head (7) is installed on the flange end cap (6) at the tail end of the simulated drilling pipe (5). The return water sealing head (7) is connected to the water storage tank (1) through the return water valve (8) for water return. The rock chamber (4) includes a hollow rock chamber body (401), a rock chamber cap (402) is installed at the top of the rock chamber body (401), and the rock chamber cap (402) is connected to the water supply valve (13); the bottom end of the rock chamber body (401) is detachably installed with the top end of a hollow connector (403), the bottom end of the connector (403) is connected to the side wall of the simulated borehole pipe (5), and a replaceable water outlet plate (404) is installed inside the connector (403), and a simulated water outlet (405) is provided through the middle of the water outlet plate (404); the cavity between the water outlet plate (404), the connector (403), the rock chamber body (401) and the rock chamber cap (402) is a lithological simulation cavity (406). An energy storage regulator (9) is also provided between one end of the water storage tank (1) and one end of the multiple water supply valves (13); The energy storage voltage regulator (9) includes multiple energy storage devices (901), each energy storage device (901) including an energy storage tank (90101), an energy storage tank inlet valve (90102), an energy storage tank drain valve (90103) and an overflow valve (90104) are installed in parallel on the energy storage tank (90101), and a pressure gauge (90105) is provided between the energy storage tank (90101) and the overflow valve (90104). The energy storage regulator (9) also includes a first electromagnetic flow valve (902) and a second electromagnetic flow valve (903) connected in parallel. One end of the first electromagnetic flow valve (902) and one end of the second electromagnetic flow valve (903) are both connected to one end of the plurality of water supply valves (13). The other end of the first electromagnetic flow valve (902) is connected to the energy storage tank inlet valve (90102) of the first group of parallel energy storage devices (901). The energy storage tank drain valve (90103) and overflow valve (90104) of the first group of parallel energy storage devices (901) are connected to the water storage tank (1). The other end of the second electromagnetic flow valve (903) is connected to the energy storage tank inlet valve (90102) of the second group of parallel energy storage devices (901). The energy storage tank drain valve (90103) and overflow valve (90104) of the second group of parallel energy storage devices (901) are connected to the water storage tank (1). One end of the first electromagnetic flow valve (902) and one end of the second electromagnetic flow valve (903) are both connected to one end of the same drain valve (904), and the other end of the drain valve (904) is connected to the water storage tank (1). The simulated drilling pipe (5) is coaxially installed with an acoustic wave sensing armored optical cable (10), and both ends of the acoustic wave sensing armored optical cable (10) pass through the flange end caps (6) at both ends of the simulated drilling pipe (5). A liquid turbine flow meter (1205) and a pressure transmitter (1206) are respectively installed on the high-pressure pipeline (14) between each water supply valve (13) and the rock chamber (4). It also includes a hydrodynamic parameter acquisition system (12), which includes a computer terminal (1201). The computer terminal (1201) is connected to an analog signal acquisition board (1203) via a 485 to USB communication module (1202). The analog signal acquisition board (1203) is connected to a 24V power supply module (1204). The analog signal acquisition board (1203) is also connected to a liquid turbine flow meter (1205) and a pressure transmitter (1206) to acquire signals. The liquid turbine flow meter (1205) and the pressure transmitter (1206) are also connected to the 24V power supply module (1204) for power.

2. The physical simulation experimental device for fine exploration of water-bearing sections in underground rock strata as described in claim 1, characterized in that, The water pump (2) mentioned above is a reciprocating plunger pump.

3. The physical simulation experimental device for fine exploration of water-bearing sections in underground rock strata as described in claim 1, characterized in that, The rock chambers (4) are three in number, located at distances of 12.64–12.83 m, 18.47–18.66 m, and 20.54–20.73 m from the beginning of the simulated borehole pipe (5), respectively.

4. The physical simulation experimental device for fine exploration of water-bearing sections in underground rock strata as described in claim 1, characterized in that, The acoustic wave sensing armored optical cable (10) is connected to the flange end cap (6) through the optical fiber sealing head (11).

5. The physical simulation experimental device for fine exploration of water-bearing sections in underground rock strata as described in claim 1, characterized in that, The acoustic wave sensing armored optical cable (10) is connected to the distributed acoustic wave sensing system (15).

6. A physical simulation experimental method for fine exploration of water-bearing sections in underground rock strata, characterized in that, The physical simulation experimental method uses the physical simulation experimental device for fine exploration of water-bearing sections of underground rock strata as described in any one of claims 1 to 5; The physical simulation experimental method includes the following experimental steps: Step 1: Start the monitoring system: Turn on the distributed acoustic wave sensing system (15) and set the acquisition parameters; the acquisition parameters include the sampling frequency, sampling interval and data storage length. Simultaneously, start the hydrodynamic parameter acquisition system (12) and set the unit of flow rate and sampling frequency; System time between the synchronous hydrodynamic parameter acquisition system (12) and the distributed acoustic wave sensing system (15); Step 2, set up the simulated water outlet: Install the first type of water outlet plate (404) with simulated water outlet (405) at the bottom of the lithological simulation chamber (406) of the rock chamber (4). The first type of simulated water outlet (405) is a circular simulated water outlet (405) with an inner diameter of 3mm. Ensure that the installation is firm and install a screen at the simulated water outlet (405) to prevent sandstone particles from entering the simulated borehole pipe (5). Step 3, filling with the first type of sandstone: Select the first type of sandstone, which is fine-grained sandstone, and fill it evenly into the lithological simulation cavity (406); connect the connector (403) of the rock chamber (4) to the simulated borehole pipe (5), and connect the rock chamber cap (402) of the rock chamber (4) to the water supply valve (13) through the high-pressure pipe (14); Step 4, Water Injection and Pressure Stabilization: Start the water pump (2) and fill the rock chamber (4) and simulated borehole pipe (5) with water through the water supply valve (13), and close all water supply valves (13); fill the water storage tank (1) with water through the water pump (2) and check valve (3) to the energy storage regulator (9) until the maximum experimental pressure is reached, and then turn off the water pump (2). Open the return water valve (8) and the supply water valve (13), and inject water into the rock chamber (4) and the simulated borehole pipe (5) through the energy storage regulator (9). Control the initial water injection flow rate by adjusting the supply water valve (13), and use the energy storage regulator (9) to ensure that the acoustic signal is collected under stable flow conditions and high-quality data. Step 5, Data Collection: Data collection begins from the initial stable flow rate and continues until the minimum flow rate designed for the flow experiment is reached, at which point data collection stops. Step 6: Replace with other sandstone or conglomerate: Replace the second type of sandstone with medium-grained sandstone using the same method as in step three, and repeat steps four and five. Replace the third type of sandstone with coarse-grained sandstone using the same method as in step three, and repeat steps four and five. Replace the conglomerate using the same method as in step three, and repeat steps four and five. Step 7: Replace with other simulated water outlets: Replace the second type of simulated water outlet (405) using the same method as in step two. The second type of simulated water outlet (405) is a circular simulated water outlet (405) with an inner diameter of 5mm. Repeat steps three to six. Replace the third type of simulated water outlet (405) using the same method as in step two. The third type of simulated water outlet (405) is a circular simulated water outlet (405) with an inner diameter of 7mm. Repeat steps three to six. Replace the fourth type of simulated water outlet (405) using the same method as in step two. The fourth type of simulated water outlet (405) is a circular simulated water outlet (405) with an inner diameter of 9mm. Repeat steps three to six. Step 8: Shut down the device and data processing: After the experiment, close the water supply valve (13) and return valve (8), shut down the hydrodynamic parameter acquisition system (12), and shut down the distributed acoustic wave sensing system (15) to ensure safe shutdown of the equipment. Then open the drain valve (904) to drain the remaining water in the energy storage regulator (9) and thoroughly clean the equipment. Next, all the collected acoustic data were analyzed in detail. By combining different flow rates, sandstone and simulated outlet conditions, sensitive acoustic features related to the water-rich layer were extracted. Finally, a mathematical model between acoustic data and flow rate changes was established and verified.

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