Local karst water storage system detection system and method based on well-ground multi-parameter combination

Abstract

The invention discloses a local karst water storage system detection system and method based on well-ground multi-parameter combination, belonging to the technical field of karst groundwater detection, innovatively combining two-dimensional profile resistivity, one-dimensional vertical resistivity, one-dimensional vertical natural potential, one-dimensional vertical video image, one-dimensional vertical well water conductivity and multiple key geophysical parameters to characterize the relevant information of the local karst water storage system; and proposes a set of delayed detection schemes and data interpretation methods combined with brine tracers, based on the complementary advantages and result feedback between the measured parameters of different dimensions, different scales and different principles, jointly realize the refined detection of the spatial distribution characteristics of the local karst water storage system and the hydrodynamic characteristics such as the groundwater flow layer, direction, intensity, etc., the detection results are more comprehensive and accurate, and the local karst water storage system advanced prediction technology suitable for urban environment is provided, which provides technical support for underground engineering construction and ecological environment protection in karst areas.

Description

Technical Field

[0001] The present invention belongs to the technical field of karst groundwater detection, and in particular relates to a local karst water storage system detection system and method based on well-ground multi-parameter combination. Background Art

[0002] With the acceleration of urban modernization, the development and utilization of underground space has become a necessary means of construction for urban development, such as subway tunnels, underground shopping malls, underground parking lots, etc., and the construction layers are mostly located in strata shallower than 50m. Studies have shown that for strata with extremely developed underground karst, groundwater is mainly stored and transported through the crack-pipeline network in the rock strata, forming a complex karst groundwater runoff channel, and its spatial distribution is highly anisotropic and random. The shallow karst crack-pipeline network within the 100-meter scale of the stratum where the channel is located is defined as a local karst water storage system with good water richness. In addition, some strata with relatively developed karst and good connectivity can also form relatively isolated local karst water storage systems, but the hydrodynamic characteristics are different from the former.

[0003] The widely distributed local karst water storage system brings huge safety risks to the construction of urban underground projects. For example, its strong water-richness may cause engineering problems such as tunnel water inrush and foundation pit water gushing. At the same time, drainage during the construction and operation of underground projects may seize the karst water supply source, leading to ecological and environmental problems such as reduced flow of downstream karst springs and loss of surface water. Therefore, it is of great significance to ensure the safety of underground projects in karst areas by conducting geological advance forecasts for the planned construction areas of underground projects such as subway tunnels and basements, and to identify the spatial distribution characteristics and related hydrodynamic characteristics of local karst water storage systems.

[0004] At present, the investigation methods for local karst water storage systems mainly include electromagnetic methods, acoustic methods and geophysical logging methods. For example, the principle of transient electromagnetic method (TEM) is to emit a pulsed primary electromagnetic field into the ground, and identify the abnormal distribution characteristics of the underground medium by monitoring the spatiotemporal distribution characteristics of the secondary electromagnetic field generated by the underground eddy current field induced by the pulsed electromagnetic field. However, when applied to the detection of local karst water storage systems, it has the defects of low spatial resolution and limitations in shallow detection blind areas. The ground penetrating radar method (GPR) is mainly based on the abnormal changes of high-frequency radio waves caused by the significant electrical differences between karst cavities, water-filled or clay-filled karst formations and the surrounding formation media to determine the distribution of underground karst. The hyperbolic reflection anomaly, phase axis displacement, Analysis of image anomaly features such as reflected wave waveform distortion can identify the distribution of karst in the formation. However, the widespread existence of geological anomalies such as pipelines, formation fractures, sand bodies, karst cavities, and water-filled caves in urban formations makes it difficult to accurately interpret the abnormal features of radar images. The data quality is greatly affected by urban electromagnetic noise and has poor applicability. In addition, electrical resistivity tomography (ERT) is mainly based on the resistivity difference between dry caves (higher resistivity) or saturated karst development areas (lower resistivity) and bedrock, and reveals the karst distribution of the formation by obtaining the spatial distribution of resistivity in the detection area. However, the detection depth of this method is controlled by the length of the survey line, the detection depth is limited, and the deep resolution is poor. In addition, it is difficult to implement in an urban environment and has strong electromagnetic background interference.

[0005] In summary, the existing survey methods cannot simultaneously characterize the hydrodynamic characteristics of karst spatial distribution, groundwater flow process, stratum permeability, groundwater runoff direction and intensity, and it is also difficult to achieve the refined detection of the spatial distribution and hydrodynamic characteristics of local karst water storage systems. Therefore, it is necessary to develop a local karst water storage system advance prediction technology that can be non-destructive, fast, accurate, and suitable for urban environments, to provide technical support for underground engineering construction and ecological environmental protection in karst areas. Summary of the invention

[0006] In order to solve the problem that existing detection methods are difficult to comprehensively investigate the spatial distribution characteristics of local karst water storage systems and the hydrodynamic characteristics of groundwater flow layers, direction, intensity, etc., the present invention proposes a local karst water storage system detection system and method based on the combination of well and ground multi-parameters, so as to detect the hydrodynamic characteristics such as the spatial distribution range, permeability, groundwater runoff direction and intensity of local karst water storage systems that may exist in the planned construction areas of underground projects such as subway tunnels.

[0007] The present invention is implemented by adopting the following technical scheme: a local karst water storage system detection system based on well-ground multi-parameter combination, including a host module, a multi-channel data relay module, a measurement module, a salt water injection module and a downhole video acquisition module;

[0008] The host module includes a power module, a main control machine, a data storage module, a data remote transmission module, a central control unit and various acquisition circuit modules, all of which are placed in the main box; the power module is a 64V high-power DC lithium battery, which is connected to the main control machine through a dedicated connecting line, and supplies power to each power unit through the main control machine; the main control machine is connected to the data storage module, the data remote transmission module, the central control unit and each acquisition circuit module to control the operating status, parameter setting, data storage and remote transmission of each module; the data remote transmission module is connected to the main control machine and the data storage module, and establishes communication with the indoor workstation through a 4G wireless network to perform real-time remote data transmission; the data storage module includes a 128G high-speed SD card and a data reading and writing module; the central control unit is connected to each acquisition circuit module, and controls each acquisition circuit module to perform data acquisition after receiving instructions from the main control machine.

[0009] The multi-channel data relay module includes four 48-core data interfaces, one vertical electrode system data interface, one conductivity sensor array data interface, one remote N interface and one communication interface, which are respectively used to connect four 48-pole ground potential parallel acquisition cables, a 50-pole in-well vertical electrode system, a 50-channel in-well conductivity sensor array, an infinite potential sampling electrode and a main control computer, and are used to establish data communication and power supply between each measuring electrode, sensor and host module.

[0010] The measuring module comprises a ground electrode array, an infinite potential sampling electrode N, an in-well vertical electrode system and an in-well vertical conductivity sensor array. The ground electrode array is composed of 4 48-pole parallel potential acquisition cables with a pole spacing L2 of 5m. Different electrode numbers, line lengths, and array shapes (such as cross type, straight line type, arc type, etc.) can be formed according to measurement requirements for parallel acquisition of ground potential information; the infinite potential sampling electrode N is a stainless steel electrode rod, inserted into the formation at a distance of not less than 2km from the host, and connected to the multi-channel data relay module through a wire to collect the potential reference value at infinity; the vertical electrode system in the well is composed of 50 annular stainless steel electrode rings with a pole spacing L1 of 1m. Each stainless steel electrode is connected to an independent micro-relay switch and connected to the 50-core data interface of the multi-channel data relay module through a dedicated cable. The switch state of any electrode can be controlled by the main control machine for well power supply and well potential signal acquisition; the vertical conductivity sensor array in the well is composed of 50 conductivity sensors with a spacing of 1m, which are connected to the 50-core data interface of the multi-channel electrode conversion module through a dedicated cable for well water stratification conductivity data acquisition. The ground electrode array adopts a parallel acquisition design, that is, the potential acquisition unit synchronously collects all electrode potential signals and uploads them to the upper-level unit. Compared with the traditional serial acquisition method, parallel acquisition obtains potential data under the same power supply electric field, which effectively avoids data disturbances caused by background noise and dynamic changes of underground media. In addition, the parallel acquisition efficiency is extremely high, which can significantly improve the overall detection efficiency.

[0011] The brine injection module includes a water storage device, a flow meter, a water injection pipe, and a water injection pump, and is used to inject a brine tracer into the hole and record the flow rate and volume of the injected brine.

[0012] The downhole video acquisition module includes a downhole camera module and a 50m video signal line, and is used to collect video image data of the well wall in the hole.

[0013] The present invention also proposes a detection method for a local karst water storage system detection system based on well-ground multi-parameter combination, comprising the following steps:

[0014] Step A: Select the key water-rich karst strata within the scope of the project construction as the planned survey area, set up a salt injection measurement well in the center of the planned survey area, and collect video images in the well:

[0015] Among them, the salt injection measurement well is required to be no less than 50m deep and 150-300mm in diameter. No casing is set on the well wall. The core information is recorded, and existing boreholes that meet the conditions can also be used.

[0016] Step B: arranging the surface measurement line, the well measurement line, the host and other system devices with the selected salt injection measurement well as the center, and deploying the salt water injection module;

[0017] Specifically, a cross-type ground electrode array is arranged with the salt injection measurement well as the center. The array consists of four 48-pole parallel acquisition cables and an infinite pole N. Each electrode is connected to the ground through a stainless steel electrode rod. A well measurement cable with two functions of an integrated vertical electrode system and a vertical conductivity sensor array is arranged in the well to connect the ground electrode array, the well measurement cable, the multi-channel data relay module, and the host module.

[0018] Before placing the measuring cable in the well, the downhole video acquisition module of the system is used to measure the downhole video image data of the salt injection measurement well, and the formation information of the drilling location and the karst development around the well are preliminarily identified;

[0019] Step C: collect multiple key geophysical parameters, including well-ground resistivity profile data collection, one-dimensional resistivity logging data collection, one-dimensional natural potential logging data collection and one-dimensional conductivity logging data collection, specifically including:

[0020] (1) The host computer controls the well-ground resistivity data acquisition module, performs the measurement work of powering the well electrodes and collecting the ground potential data in parallel with the 192-pole ground + infinite potential sampling electrode N according to a specific acquisition method, obtains multiple sets of power supply position-power supply current-ground potential data, calculates the apparent resistivity of the measurement area based on the above data, and further performs inversion calculation to obtain the true resistivity profile of the measurement area;

[0021] (2) The host controls the one-dimensional resistivity data acquisition module, and controls the 50 stainless steel electrode rings (P1-P50) of the vertical electrode system in the well to collect one-dimensional resistivity data based on the Wenner arrangement measurement principle. In each measurement, Pi and Pi+3 correspond to the external power supply electrodes A and B, and Pi+1 and Pi+2 correspond to the internal measurement electrodes M and N (i is the number of measurements). Each measurement records the potential difference ΔU and the current I, and calculates the distribution curve of the resistivity of the sediment object with the depth;

[0022] (3) The host computer controls the one-dimensional natural potential logging data acquisition module to control the 50 stainless steel electrode rings (P1-P50) of the vertical electrode system in the well to perform serial potential measurement. Each measurement uses Pi+1 and Pi+2 as the corresponding measuring electrodes M and N (i is the number of measurements), records the natural potential difference ΔU, and obtains the distribution curve of the sediment natural potential with depth;

[0023] (4) The host controls the one-dimensional conductivity data acquisition module to control the vertical conductivity sensor array in the well of the measuring cable in the well to measure the well water conductivity, and collects 50 well conductivity data points in parallel, with a data interval of 1m;

[0024] Step D, injecting a salt water tracer into the salt injection measurement well, and collecting time-lapse data at specific intervals;

[0025] After completing the measurement of well-ground resistivity profile data, one-dimensional resistivity data, one-dimensional natural potential data and one-dimensional conductivity data of the background time in the proposed area, the brine injection module controls the water injection pump to inject water at a speed of 10m 3 The prepared brine was injected into the injection well at a water injection rate of / h. The salinity of the brine was 102.4ppt, the conductivity was 204.7ms, and the resistivity was about 0.05Ω·m (about 2.5×10 -4 times and 2.5×10 of groundwater -3 times), the total volume of injected brine is 10m 3 , the salt injection time is 1 hour;

[0026] And at 1h, 24h, 48h, and 72h of brine injection, step C is repeatedly executed to complete the continuous collection of well-ground resistivity profile data, one-dimensional resistivity data, one-dimensional natural potential data, and one-dimensional conductivity data. The above data can be transmitted to the indoor workstation in real time through the remote data transmission module for data interpretation, and whether to continue to add measurement time can be determined according to the brine diffusion process obtained by the interpretation;

[0027] Step E: Complete all measurement work, recover the measurement equipment, and interpret the results based on the detection data.

[0028] Compared with the prior art, the advantages and positive effects of the present invention are:

[0029] This scheme takes the salt injection measurement well as the center, and deploys multi-parameter joint measurement systems such as measurement modules and brine injection modules. It can respectively realize the refined description of the static distribution range and dynamic hydrodynamic process of the local karst water storage system based on the time-lapse detection results of multiple parameters and multiple dimensions. Based on the coupled brine tracing and well-ground multi-parameter joint time-lapse detection, the spatial distribution range, main runoff layer, runoff direction, runoff velocity and other hydrodynamic characteristics of the local karst water storage system are determined according to the low-resistance anomaly area and high-potential anomaly characteristics in the pseudo-three-dimensional well-ground resistivity profile and the one-dimensional natural potential logging curve.

[0030] By using one-dimensional resistivity, conductivity logging data and downhole video imaging data as means of data correction and result verification, the detection effect and interpretation accuracy can be further improved; compared with the previous regional exploration and monitoring methods used in shallow karst areas, the detection results are more comprehensive and accurate, which greatly improves the detection capability of local karst water storage systems in shallow karst areas, and effectively solves the problem of effective detection of the spatial distribution range, main runoff layers, water movement direction, speed and other hydrodynamic characteristics of local karst water storage systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1This is a schematic diagram of the layout structure of the detection system according to an embodiment of the present invention;

[0032] Figure 2 for Figure 1 Schematic diagram of the structure of the measuring cable in the well;

[0033] Figure 3 for Figure 1 A schematic diagram of the structure of one of the acquisition cables in the ground electrode array (including four 48-pole parallel potential acquisition cables);

[0034] Figure 4 Schematic diagrams of the modules of the system of the embodiment of the present invention; wherein (a) is a schematic diagram of the main control module; (b) is a schematic diagram of the well-ground resistivity data acquisition module; (c) is a schematic diagram of the natural potential logging data acquisition module; (d) is a schematic diagram of the resistivity logging data acquisition module; (e) is a schematic diagram of the conductivity logging data acquisition module;

[0035] Figure 5 It is a schematic flow chart of a detection method for a local karst water storage system according to an embodiment of the present invention;

[0036] Figure 6 Based on Figure 5 Schematic diagram of pseudo three-dimensional resistivity profile of well and ground at different times before and after salt injection obtained by the method;

[0037] Figure 7 Based on Figure 5 Partial downhole video images, one-dimensional resistivity logging data and one-dimensional natural potential logging data at different times before and after salt injection obtained by the method;

[0038] Among them: 1. Host module; 2. Multi-channel data relay module; 3. Ground electrode array (consisting of 3-1, 3-2, 3-3, 3-44 48-pole parallel potential acquisition cables); 4. In-well measurement cable; 5. In-well video acquisition module; 6. Infinite potential sampling electrode N; 7. Brine storage barrel; 8. Water injection pump; 9. Water injection pipe; 100. Salt injection measurement well; 200. Local karst water storage system; 300. Ground; P1~P50, ring switch electrode; E1~E50, conductivity sensor; M1~M48, parallel potential acquisition electrode. DETAILED DESCRIPTION

[0039] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and therefore, the present invention is not limited to the specific embodiments disclosed below.

[0040] Example 1. This example proposes a local karst water storage system detection system based on the combination of well and ground multi-parameters. The detection system can obtain video images inside the borehole, the vertical distribution of the natural potential of the borehole points, the vertical distribution characteristics of the resistivity, the vertical distribution characteristics of the water body conductivity, and the well-ground resistivity profile distribution characteristics, so as to achieve the detection target of the spatial distribution range of the local karst water storage system and the hydrodynamic characteristics such as the groundwater runoff layer, direction, intensity, and speed.

[0041] like Figure 1-3 As shown, the detection system includes a salt-dosing measurement well, a host module, a measurement module and a brine injection module; the salt-dosing measurement well is arranged at the center of the intended measurement area, the measurement module includes a ground electrode array 3, an infinite potential sampling electrode N6, and a well measurement cable 4, the well measurement cable 4 is provided with a well vertical electrode system and a well vertical conductivity sensor array, with the salt-dosing measurement well as the center, the well vertical electrode system and the well vertical conductivity sensor array are vertically arranged in the salt-dosing measurement well, and the ground electrode array is laid in a cross shape around the ground of the salt-dosing measurement well. In this embodiment, the number of electrode rings and sensors arranged on the ground electrode array and the well measurement cable can be adjusted according to the detection requirements, and no excessive restrictions are made here. Among them, the ground electrode array 3 includes 4 48-pole parallel potential acquisition cables (3-1, 3-2, 3-3, 3-4), the brine injection module is connected to the salt injection measurement well, including a brine storage tank 7, an injection pump 8 and an injection pipe 9 to inject brine into the salt injection measurement well. A downhole video acquisition module is also provided in the salt injection measurement well. The host module 1 is connected to the measurement module through a multi-channel data relay module 2.

[0042] Combination Figure 4 As shown, the host module includes a power module, a main control machine, a data storage module, a data remote transmission module, a central control unit and various acquisition circuit modules. The power module is a 64V high-power DC lithium battery, which is connected to the main control machine through a dedicated connection line and supplies power to each power unit through the main control machine; the main control machine is connected to the data storage module, the data remote transmission module, the central control unit and each acquisition circuit module to control the operating status, parameter setting, data storage and remote transmission of each module; the data remote transmission module is connected to the main control machine and the data storage module, and establishes communication with the indoor workstation through a 4G wireless network for real-time remote transmission of measurement data; the data storage module includes a 128G high-speed SD card and a data reading and writing module; the central control unit is connected to each acquisition circuit module, and controls each acquisition circuit module to perform data acquisition after receiving instructions from the main control machine.

[0043] Each acquisition circuit module includes a well-ground resistivity data acquisition module, a one-dimensional natural potential data acquisition module, a one-dimensional resistivity data acquisition module, and a one-dimensional conductivity data acquisition module:

[0044] Among them, the well-ground resistivity data acquisition module is controlled by the central processing unit to control the serial 50-pole electrode switch control unit to make two specific electrodes of the well electrode system in the on state, and the other 48 poles are in the off state. The switch function of the electrode is realized by a micro relay, and then the variable frequency square wave electrical signal transmitting unit transmits current (pole A and pole B) to the two specific electrodes to establish an artificial electric field. The current sensor and current measurement A / D module measure the power supply current intensity I and feed it back to the central processing unit; the specific process is: after receiving the transmission instruction, the variable frequency square wave electrical signal transmitting unit supplies power to the surrounding formations from the well electrode according to the set duty cycle, frequency, current value and power supply duration. In this process, a pseudo-random signal can be generated by compiling a specific duty cycle and frequency for the acquisition unit to extract effective signals. The application of this technology effectively solves the problem of receiving tiny signals in the complex electromagnetic environment of the city. After the artificial electric field is established, the central processing unit controls the 193-pole potential signal parallel acquisition unit to synchronously obtain the potential signal of each electrode in the ground electrode array, and after the potential sensor, amplifier, and filter are sorted and calculated, the potential measurement A / D module converts it into a digital signal to obtain the measured potential value U m1 ~U m192 and reference potential value U n Finally, the central processing unit uploads the data to the main control computer and stores it in the data storage module. The central processing unit automatically replaces the power supply electrode according to the specific power supply scheme proposed by the present invention, repeats the above current and potential measurement process, obtains a set of power supply electrode-power supply current-measurement potential data sets, and performs inversion calculation based on the data sets to obtain the well-ground resistivity profile of the measurement area.

[0045] By adjusting the pole spacing and power supply position of the power supply electrode pair, it is possible to establish an artificial electric field with different field strengths and influence ranges, and further obtain a rich ground potential data set to calculate the required well-ground resistivity profile. Theoretically, any two electrodes in the well electrode system can be used as power supply poles A and B to establish an artificial electric field, so up to 2450 power supply combinations can be generated, but using all power supply combinations will generate a huge amount of data calculation and a long acquisition time, and the improvement in detection effect is not significant. Through computer simulation calculations of theoretical detection profiles of multiple power supply schemes, the present invention finally determined the optimal power supply scheme consisting of four power supply pair arrangement modes with fixed pole spacings of 1m, 10m, 20m and variable pole spacings of 1 to 50m, specifically:

[0046] ① The pole distance is 1m, the pole A is P1, the pole B is P2, and the pole A is P2, and the pole B is P3, and so on, until the last electrode; ② The pole distance is 10m, the pole A is P1, the pole B is P11, and the pole A is P2, and the pole B is P12, and so on, until the last electrode; ③ The pole distance is 20m, the pole A is P1, the pole B is P21, and the pole A is P2, and the pole B is P22, and so on, until the last electrode; ④ The pole distance is changed from 1 to 50m, the pole A is P1, the pole B is P50, and the pole A is P2, and the pole B is P50, and so on, until the last electrode. This scheme only uses 165 power supplies, and the data obtained covers all types of electric fields more comprehensively, which significantly improves the efficiency of data acquisition and inversion while ensuring the profile effect.

[0047] Table 1 Power supply scheme for well-ground resistivity measurement

[0048]

[0049]

[0050] The one-dimensional natural potential data acquisition module is controlled by the central processing unit to control the serial 50-pole electrode switch control unit to make two specific electrodes of the well electrode system in the on state and the other 48 poles in the off state. Then the 50-pole potential signal serial acquisition unit measures the natural potential signals of the two specific electrodes (M pole and N pole), and after being sorted and calculated by the potential sensor, amplifier, and filter, it is converted into a digital signal by the potential measurement A / D module to obtain the measured potential value U m and U n , further difference calculation is performed to obtain the gradient potential ΔU. Each measurement uses Pi+1 and Pi+2 as the measuring electrodes M and N (i is the number of measurements). Finally, the central processing unit uploads the data to the main control computer and stores it in the data storage module. The central processing unit automatically replaces the potential measuring electrodes in a downward movement, repeats the above potential measurement process, and obtains the gradient natural potential data ΔU at different positions in the borehole. i , based on the data, the one-dimensional natural potential distribution curve at the borehole is drawn.

[0051] The one-dimensional resistivity data acquisition module is controlled by the central processing unit to control the serial 50-pole electrode switch control unit to make 4 specific electrodes in the 50 stainless steel electrode rings (P1-P50) of the well electrode system in the on state, and the remaining 46 poles are in the off state. Then the variable frequency square wave electric signal transmitting unit transmits current (pole A and pole B) to two specific electrodes to establish an artificial electric field. The current sensor and current measurement A / D module measure the power supply current intensity I and feed it back to the central processing unit. After the artificial electric field is established, the central processing unit controls the 50-pole potential signal serial acquisition unit to synchronously obtain the potential signals of the remaining two electrodes (pole M and pole N), and after the potential sensor, amplifier, and filter are sorted and calculated, the potential measurement A / D module converts it into a digital signal to obtain the measured potential value U m , U n , and finally the central processing unit uploads the data to the main control machine and stores it in the data storage module.

[0052] The present invention performs measurement according to the Wenner arrangement measurement principle. In each measurement, Pi and Pi+3 are used as external power supply electrodes A and B, and Pi+1 and Pi+2 are used as internal measurement electrodes M and N (i is the number of measurements). The potential difference ΔU and the current I are recorded in each measurement. The electrode ring radius b is 0.02m, and the pole distance a is 1m. The distribution curve of the resistivity of the deposited object with depth is calculated based on the following formula.

[0053]

[0054] The one-dimensional conductivity data acquisition module is controlled by the central processing unit. The 50-channel conductivity signal parallel acquisition unit collects 50 conductivity sensor signals in the well in parallel, and then converts them into digital signals through the conductivity measurement A / D module to obtain the well water conductivity value σ 1～50 , the distribution curve of conductivity with depth can be further plotted.

[0055] The downhole video image acquisition module is controlled by the main control machine to acquire video images using the dedicated downhole camera module. The video image data of the wellbore wall is transmitted back to the main control machine via a 50m video signal line and stored in an SD card.

[0056] The multi-channel data relay module 2 consists of four 48-core data interfaces, one vertical electrode system data interface, one conductivity sensor array data interface, one remote N interface, and one communication interface, which are respectively used to connect four 48-pole ground potential parallel acquisition cables, a 50-pole in-well vertical electrode system, a 50-way in-well conductivity sensor array, an infinite potential sampling electrode, and a main control computer, and are used to establish data communication and power supply between each measuring electrode, sensor, and host module. Each connector of the multi-channel data relay module is designed to be waterproof to adapt to complex outdoor use conditions.

[0057] The 48-pole parallel potential acquisition cable consists of 48 stainless steel measuring electrodes, such as Figure 3 As shown, the electrode spacing L2 is 5m. In actual use, the electrode rod inserted into the soil is grounded to the measuring electrode. Each stainless steel electrode is connected to a wire to form a 48-core parallel acquisition cable. The cable is wrapped with a wear-resistant and waterproof polyvinyl chloride sheath, and has a built-in signal shielding layer to isolate external electrical signal interference. The cable end is encapsulated with a 48-core watertight plug. Each core corresponds to an electrode, which is connected using the four 48-core data interfaces of the multi-channel data relay module 2, and communication is established with the host through the multi-channel data relay module 2.

[0058] The well measurement cable 4 includes two measurement modules, a 50-pole vertical electrode system and a 50-channel well conductivity sensor array. Figure 2 As shown: (1) The electrode system consists of 50 stainless steel electrode rings, with an electrode ring radius b of 0.02m and an electrode spacing of 1m. Each stainless steel electrode ring is connected to a micro serial relay, which controls the connection status between the electrode and the upper-level acquisition module. The micro serial relay adopts the 485 communication protocol. All relays are connected in series and set to the normally open mode. They are energized when needed and are controlled by the upper-level serial 50-pole electrode switch control unit through the signal line; (2) The conductivity sensor array consists of 50 conductivity sensors, with a spacing of 1m, arranged at intervals with the electrode rings. The sensor model can be selected as the TFE-1 high-precision multi-parameter water quality sensor, which can perform real-time sampling of well water conductivity (EC). The conductivity sensor array is connected to the 50-channel conductivity signal parallel acquisition unit through a dedicated cable to acquire EC signals, and the analog signals are sent to the conductivity measurement A / D module for conversion into digital signals. The above-mentioned stainless steel electrode rings, micro relays, conductivity sensors and connecting cables are all integrated into a main measuring cable. The outer layer of the main measuring cable is a wear-resistant and waterproof polyvinyl chloride sheath, with a built-in tensile lining for strength, and the inner layer is a signal shielding layer to isolate external electrical signal interference. Each sensor probe and stainless steel electrode ring is embedded in the outside of the cable, and the connection is designed to be watertight. The power supply line, signal line, and relay switch are all placed in the internal space of the main measuring cable.

[0059] Among them, the well measurement cable 4 adopts a one-cable four-purpose design, which makes full use of the narrow space in the well. The whole consists of two parts: an electrode system and an EC sensor array. Any electrode in the electrode system can be independently switched, so that it can be used for underground power supply, natural potential data measurement and resistivity data measurement of well-ground resistivity profile measurement respectively. There is no need to repeatedly replace cables during the measurement of the three methods, and the environmental disturbance caused by repeated cable replacement to subsequent continuous monitoring is avoided. In addition, the EC sensor array integrated on the cable can synchronously obtain the conductivity data of the well water, which can provide the most direct evidence support for the interpretation of well-ground resistivity profile data, natural potential data and resistivity data at the same time.

[0060] The salt water injection module consists of a water storage device, a flow meter, a water injection pipe, and a water injection pump. The water storage device is a 4m 3 Water storage tank, can store up to 12m 3 Brine tracer; flow meter is set at the outlet of injection pipe for injection rate; injection pump uses 2 5m 3 / h high-flow booster pump draws brine from the water storage device in parallel at a rate of 10m 3 Brine is injected into the salt injection measurement well at an injection rate of / h.

[0061] Example 2: Based on the local karst water storage system detection system based on well-ground multi-parameter combination proposed in Example 1, this example proposes a corresponding time-lapse detection method, combined with Figure 5 As shown, the following steps are included:

[0062] Step A: Select the key water-rich karst strata within the scope of the project construction as the planned survey area, set up a salt injection measurement well in the center of the planned survey area, and collect video images in the well:

[0063] According to the underground engineering construction plan and the results of the preliminary water-rich survey, the planned survey area is selected, and a salt injection measurement well is set in the center of the planned survey area. The depth is required to be no less than 50m, the diameter is 150-300mm, and no casing is set on the well wall. The corresponding core information is obtained for later data interpretation, and existing boreholes that meet the conditions can also be used. Then the high-concentration brine tracer prepared in advance is transported to the survey area and temporarily stored in a water storage device. The salinity of the brine is 102.4ppt, the conductivity is 204.7ms, the resistivity is about 0.05Ω·m, and the total volume of the brine is 10m 3 , connect the water injection pump, water injection pipe, flow meter and power supply, place the outlet of the water injection pipe into the salt injection measuring well, and prepare for injecting brine.

[0064] Step B: arranging the surface measurement line, the well measurement line, the host and other system devices with the selected salt injection measurement well as the center, and deploying the salt water injection module;

[0065] With the selected salt injection measurement well as the center, a cross-shaped ground electrode array is arranged, such as Figure 1As shown in the figure, the array consists of four 48-pole parallel acquisition cables and one far-pole N placed 2 km away. Each electrode is grounded by a stainless steel electrode rod inserted 20 cm into the formation. Then the well measurement cable is placed vertically in the salt measurement well. The well power supply electrode spacing is 1 m, the EC sensor spacing is 1 m, the cable depth is 50 m, the ground potential measurement electrode spacing is set to 2 m, and the length of the measurement line in each direction is 96 m. Then the ground electrode array, well measurement cable, multi-channel data relay module, and host module are connected and operated. It should be noted that before laying the well measurement cable, the downhole TV module is used to complete the collection of downhole video image data to avoid the well measurement cable from having an adverse effect on the camera module and imaging effect.

[0066] Step C: collect multiple key geophysical parameters, including well-ground resistivity profile data collection, one-dimensional resistivity logging data collection, one-dimensional natural potential logging data collection and one-dimensional conductivity logging data collection, specifically including:

[0067] Step C1, the host controls the well-ground resistivity data acquisition module, performs the measurement work of the well electrode power supply and the ground potential data parallel acquisition of 192 ground electrodes + remote electrodes N according to the specific power supply scheme provided by the present invention, obtains 165 groups of power supply position-power supply current-ground potential data, including 165×192 data points in total, and completes all data information collected once as shown in Table 2;

[0068] The center of the wellhead of the salt injection measurement well is defined as the coordinate origin, the horizontal line where the ground electrode arrays 3-1 and 3-2 are located is the X-axis, the horizontal line where the ground electrode arrays 3-3 and 3-4 are located is the Y-axis, and the wellhead downward is the Z-axis. Based on this setting, corresponding x, y, and z coordinates are assigned to each ground electrode, well electrode, and sensor. M1-1 It refers to the relative potential value at the ground electrode M1 when the power is first supplied. The specific formula is U M1 =V1-Vn, V1 is the absolute potential value measured at the position of M1, and Vn is the reference potential value measured at the position of the far pole N;

[0069] Calculate the apparent resistivity corresponding to each data point. Taking the first group of power supply as an example, the power supply electrodes are A1 and B1, the measuring electrodes are M1 to M192, the power supply electrode pair is A1-B1, and the measuring electrode pair is M1-M2. The corresponding apparent resistivity ρ 1、2 The calculation formula is:

[0070]

[0071] Where A1M1 is the distance from A1 to M1, and the distances of other electrodes can be deduced based on this naming rule. In addition, ΔU = U M1 -U M2Based on the above algorithm, the measuring electrode pairs are adjusted to M2M3, M3M4, ..., M191M192 in sequence, and all apparent resistivities of the group are calculated. The above steps are repeated to complete the apparent resistivity calculation of all power supply groups. Further, the calculated apparent resistivity data set is inverted to obtain the true resistivity profile of the measuring area. This embodiment can be implemented by relying on AGIEarthImager2D software, which is one of the more mature commercial software in the existing resistivity data processing field.

[0072] After the inversion is completed, two true well-ground resistivity profiles with a length of 190m and a depth of 50m in the X and Y directions are obtained. The two profiles can be further visualized in three-dimensional space to form pseudo three-dimensional detection results;

[0073] The pseudo three-dimensional resistivity profile of the well and the ground obtained in the above steps focuses on interpreting the spatial distribution range of the karst water storage system. In view of the shortcomings of the traditional electrical profile that the resolution decreases with depth, the detection depth is insufficient, and the detection efficiency is low, the present invention uses a special cable to perform downhole power supply and parallel acquisition of ground potential, so that the detection effect is not affected by the burial depth of the karst water storage body, and has a good characterization ability of its top and bottom interfaces. In addition, the parallel acquisition method greatly shortens the acquisition time, and makes the potential data set obtained each time generated by the same power supply electric field at the same time, ensuring the accuracy of the potential data, while avoiding the influence of background noise changes on the data.

[0074] Table 2 Original data set of well-surface resistivity imaging method

[0075]

[0076]

[0077] Step C2, the host controls the one-dimensional resistivity logging data acquisition module to control 50 stainless steel electrode rings (P1-P50) of the electrode system in the well to perform serial data acquisition according to the Wenner arrangement measurement principle, and calculate the distribution curve of the formation body resistivity at the center of the measurement area with depth. Furthermore, the two-dimensional resistivity profile of the well is numerically corrected through the one-dimensional resistivity logging data, and the formation lithology and karst distribution at the borehole are delineated;

[0078] Specifically, the resistivity values ​​obtained by this method have high accuracy and can be used as true resistivity values ​​to input into the inversion program to constrain the inversion process of the two-dimensional resistivity profile of the well and the ground, which can significantly improve the numerical accuracy of the two-dimensional resistivity profile of the well and the ground.

[0079] Step C3, the host controls the one-dimensional natural potential logging data acquisition module to control the 50 stainless steel electrode rings (P1-P50) of the electrode system in the well to perform serial potential measurement to obtain the distribution curve of the natural potential of the formation at the center of the measurement area with depth.

[0080] Step C4: The host computer controls the one-dimensional conductivity logging data acquisition module to control 50 conductivity sensor arrays (E1-E50) in the well to perform parallel conductivity measurement to obtain a distribution curve of groundwater conductivity with depth in the well.

[0081] Then, the measurement of various parameters under background conditions was completed, providing a comparative basis for the analysis of subsequent time-lapse measurement results after salt injection.

[0082] Step D, injecting a salt water tracer into the salt injection measurement well, and simultaneously performing time-lapse data acquisition at specific intervals;

[0083] Start two large-flow injection pumps at 10m 3 The prepared brine was injected into the injection well at a water injection rate of / h. The salinity of the brine was 102.4ppt, the conductivity was 204.7ms, and the resistivity was about 0.05Ω·m (about 2.5×10 -4 times and 2.5×10 of groundwater -3 times), the total volume of injected brine is 10m 3 The salt injection time is 1 hour. The huge electrical difference makes the runoff path and storage location of the brine reflected as an obvious low-resistance anomaly in the resistivity profile. The present invention solves the difficult problem of distinguishing high-permeability karst and filling-type low-permeability karst by locating the low-resistance anomaly change characteristics after salt injection.

[0084] At 1h, 24h, 48h, and 72h of brine injection, step C is repeated to complete the continuous acquisition of well-ground resistivity profile data, one-dimensional resistivity logging data, one-dimensional natural potential logging data, and one-dimensional conductivity logging data. The above data can be transmitted to the indoor workstation in real time through the remote data transmission module for data interpretation, and whether to continue to add measurement time can be determined based on the brine diffusion process obtained by the interpretation;

[0085] Traditional detection methods can locate karst distribution areas, but due to the complex distribution patterns and filling types of karst, its internal connectivity, water movement process, permeability and other hydrodynamic characteristics are difficult to characterize. A single measurement method can only detect a certain attribute of the karst water storage system. The data generated by mechanically combining multiple methods often cannot correspond to each other, making it difficult to achieve the detection goal.

[0086] The present invention innovatively couples the brine tracer test with a variety of geophysical methods. The injection of brine introduces a time variable into the originally static detection process, and acts as a "developer" to highlight the water flow path inside the rock mass. The one-dimensional resistivity, natural potential, and conductivity data changes in the well are used to reflect the movement of brine along the well after injection. The well-ground resistivity profile is used to continuously track the movement of brine in the karst water storage system, thereby solving the measurement problem of dynamic information such as the internal connectivity of the karst water storage system, the water movement process, permeability, flow velocity, and flow direction.

[0087] Step E: Complete all measurement work, recover the measurement equipment, and interpret the results based on the detection data.

[0088] The interpretation method of the well-ground multi-parameter time-lapse detection data generated in this embodiment is:

[0089] ① First, determine whether there is a relatively low-resistance area in the well-ground resistivity profile. A relatively low-resistance area refers to an area where the overall resistivity is lower than that of the adjacent position. If there is a low-resistance area, the low-resistance abnormal area in the formation is defined as the spatial distribution range of the local karst water storage system. The well-ground resistivity profile is tested and corrected by using the real information of karst distribution such as formation fractures, caves, and fragmentation reflected by downhole video images and the accurate value of the resistivity distribution of the formation around the well reflected by the one-dimensional resistivity logging curve, which can greatly improve the accuracy and reliability of data interpretation;

[0090] ② Further, the main runoff layer and intensity of groundwater are delineated by the natural potential logging curve. Specifically, when groundwater flows through the karst channel in the formation, the charged water molecules rub against the surface of solid particles, resulting in an abnormal potential difference along the flow direction, which is usually manifested as a large negative offset high potential feature on the natural potential curve, corresponding to a strong water flow in the aquifer. Based on this theoretical basis, the abnormal position of the negative offset high potential fluctuation in the natural potential logging curve is first determined, and the formation is delineated as the main runoff layer. The relative size of the runoff intensity is determined by the amplitude of the abnormal potential fluctuation. The larger the amplitude of the abnormal potential fluctuation, the relatively larger the runoff intensity. Conversely, the smaller the amplitude of the abnormal potential fluctuation, the smaller the runoff intensity.

[0091] ③ Further, after the injection of salt water, the water inside the karst fracture-cavern network with good connectivity and permeability will be replaced by salt water, which will be shown as an abnormal decrease in resistivity on the resistivity profile. By comparing the resistivity profiles at different times after salt injection with the initial background profile, the area with reduced resistivity is identified as the salt water diffusion area. The main runoff layer is determined according to the distribution position of the salt water diffusion area. The salt water diffusion direction is inferred by the low-resistance anomaly changes in different directions of the pseudo-three-dimensional profile formed by the cross-line survey. The salt water diffusion distance is depicted by the range of the low-resistance anomaly area at different times, and the salt water diffusion speed is further calculated;

[0092] ④ The main runoff layers and brine-rich areas in the formations around the wells are interpreted by using the continuous changes of one-dimensional resistivity, natural potential, and conductivity logging data after salt injection. Specifically, after salt water injection, due to the rapid influx of brine at the main runoff layer and the subsequent preferential runoff flushing of fresh water, the logging data of the main runoff layer show the following characteristics: the amplitude of abnormal fluctuation of the high potential of the natural potential first increases and then decreases, the resistance first decreases and then increases, and the conductivity first increases and then decreases; and the karst with poor fluidity can store brine, so the logging data show the following characteristics: the amplitude of abnormal fluctuation of the high potential of the natural potential first increases and then decreases, the resistivity decreases and then maintains a low level, and the conductivity decreases and then maintains a low level. Based on the above characteristics, the main runoff layers and brine-rich areas of the formations near the salt injection wells can be determined. The detection range of this group of data is limited to the formations around the wellbore, but the data has high accuracy and is sensitive to brine changes. It can be used as a verification and supplement for the interpretation of well-ground resistivity profile data.

[0093] The interpretation process of the well-ground multi-parameter time-lapse detection data of the above-mentioned coupled brine tracer test is based on pseudo-three-dimensional well-ground resistivity profile data and one-dimensional natural potential logging data, with one-dimensional resistivity, conductivity logging data and downhole video imaging data as means of data correction and result verification. It ultimately solves the problem of effectively detecting the spatial distribution range, main runoff layers, water movement direction, speed and other hydrodynamic characteristics of the local karst water storage system. The detection results are detailed, comprehensive and highly reliable.

[0094] Figure 6 , 7 The in-situ detection results obtained by the actual application of the system and method of the present invention are shown in FIG. Figure 6Figure 1 shows the pseudo three-dimensional resistivity profile of the well before and after salt injection at different times. The area with resistivity lower than 100Ω·m is delineated as the karst development area. After the injection of salt water, the resistivity of the low-resistance anomaly area in the profile drops rapidly as a whole. The range of the lower low-resistance anomaly area expands and shows a trend of extending to the right in the subsequent monitoring results. The range of the upper low-resistance anomaly area does not change much. Based on the initial low-resistance anomaly distribution characteristics of the well-ground resistivity profile and the profile change characteristics after salt injection, it is inferred that the local karst water storage system shallower than 50m in the survey area is an upper and lower double-layer structure. The karst water storage system is about 90m long from east to west, about 35m long to the south of the salt injection well, and about 15m thick. The water storage body in this layer has good internal connectivity, but poor permeability with the surrounding strata. It is speculated to be an isolated water storage system; the lower karst water storage body is about 45m long from east to west, about 30m long to the south of the salt injection well, and about 10m thick. It has good connectivity with the surrounding strata and is speculated to be the main runoff layer, consisting of a dynamically open and closed, fast-flowing west runoff channel and a continuously open, slow-flowing east runoff channel. The arrows in the figure indicate the direction of water flow.

[0095] Figure 7 The following are some downhole video images, one-dimensional resistivity logging data and one-dimensional natural potential logging data at different times before and after salt injection. According to the distribution characteristics of low-resistance anomalies in the resistivity curve and negative-shifted high-potential fluctuation anomalies in the natural potential curve, combined with the characteristics of downhole video images, it is inferred that there are two karst development zones, upper and lower, in the strata shallower than 50 m in the survey area, located in the sections with elevations of 74.5-58.0 m and 49.0-39.0 m, respectively. Only a small part of the brine enters the upper karst development zone after injection, and the salinity drops rapidly after the salt injection is stopped, and gradually returns to the background level, reflecting that the permeability of this karst layer and the surrounding strata is poor, and it is an isolated water storage system; in the lower karst development zone, the brine diffuses violently at the beginning of the cessation of salt injection, and then gradually slows down, and the salt content remains at a high level, reflecting that the lower karst development zone is the main groundwater runoff layer during salt injection, and after the salt injection is stopped, it manifests as a water movement process in which salt is retained and slowly released. The red box in the figure indicates the main runoff layer in the stratum.

[0096] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A detection method for a local karst water storage system detection system based on a combination of well and ground multi-parameters, characterized in that: The detection system comprises a salt injection measurement well, a host module, a measurement module and a salt water injection module. The salt injection measurement well is arranged at the center of the intended measurement area. The host module and the measurement module are connected via a multi-channel data relay module. The salt water injection module is connected to the salt injection measurement well to inject salt water therein. The host module includes a main control machine, a data storage module, a data remote transmission module, a central control unit and various acquisition circuit modules. The main control machine is connected with the data storage module, the data remote transmission module, the central control unit and the acquisition circuit modules to control the operation status, parameter setting, data storage and remote transmission of each module. The central control unit is connected with each acquisition circuit module to control each acquisition circuit module to perform data acquisition after receiving the instruction of the main control machine. Each acquisition circuit module includes a well-ground resistivity data acquisition module, a one-dimensional natural potential data acquisition module, a one-dimensional resistivity data acquisition module and a one-dimensional conductivity data acquisition module; The measuring module includes a ground electrode array, an infinite potential sampling electrode N and a well measuring cable, on which a well vertical electrode system and a well vertical conductivity sensor array are arranged. With the salt injection measuring well as the center, the well vertical electrode system and the well vertical conductivity sensor array are vertically arranged in the salt injection measuring well, and the ground electrode array is laid in a cross shape around the ground of the salt injection measuring well; The ground electrode array includes 4 parallel potential acquisition cables, each of which is provided with a plurality of stainless steel measuring electrodes, each of which is connected to a wire; the vertical electrode system in the well includes a plurality of stainless steel electrode rings, each of which is connected to a corresponding micro serial relay, through which the corresponding electrode is connected to the upper acquisition module, and all micro relays are connected in series; the vertical conductivity sensor array in the well includes a plurality of conductivity sensors, which are arranged at intervals with the stainless steel electrode rings; the stainless steel electrode rings, micro relays and conductivity sensors are all integrated on the measuring cable in the well; The detection method comprises the following steps: Step A: Select the key water-rich karst strata within the scope of the project construction as the planned survey area, set up a salt injection measurement well in the center of the planned survey area, and collect video images in the well; Step B, arranging the host module, the measurement module and the brine injection module with the selected salt injection measurement well as the center; Step C, collecting multiple key geophysical parameters, including well-ground resistivity profile data collection, one-dimensional resistivity logging data collection, one-dimensional natural potential logging data collection and one-dimensional conductivity logging data collection; Step C1, the host module controls the well-ground resistivity data acquisition module, and performs the measurement work of the vertical electrode system in the well, the ground electrode array + the infinite potential sampling electrode N to collect the ground potential data in parallel according to the specific power supply scheme, and obtains several groups of power supply position-power supply current-ground potential data; calculates the apparent resistivity corresponding to each data point, and performs inversion calculation on the calculated apparent resistivity data set to obtain the well-ground resistivity profile of the measurement area, and then performs three-dimensional spatial visualization on the profile to form a pseudo three-dimensional detection result; Step C2, the host module controls the one-dimensional resistivity logging data acquisition module to control the multiple stainless steel electrode rings of the electrode system in the well to perform serial data acquisition according to the Wenner arrangement measurement principle, obtain one-dimensional resistivity logging data, and calculate the distribution curve of the formation body resistivity at the center of the measurement area with depth, correct the value of the well-ground resistivity profile through the one-dimensional resistivity logging data, and delineate the formation lithology and karst distribution at the borehole; Step C3, the host module controls the one-dimensional natural potential logging data acquisition module to control multiple stainless steel electrode rings of the vertical electrode system in the well to perform serial potential measurement to obtain the natural potential logging curve of the formation at the center of the measurement area; Step C4, the host module controls the one-dimensional conductivity logging data acquisition module to control a plurality of conductivity sensor arrays in the well to perform parallel conductivity measurement, and obtain a distribution curve of groundwater conductivity in the well with respect to depth; Step D, injecting a brine tracer into the salt injection measurement well through a brine injection module, and performing time-lapse data acquisition at specific time intervals; Step E: Complete all measurement work and interpret the results based on the detection data.

2. The detection method of the local karst water storage system detection system based on well-ground multi-parameter combination according to claim 1 is characterized in that: In step D, the salinity of the brine is 102.4 ppt, the conductivity is 204.7 ms, and the resistivity is 0.05 Ω·m. Step C is repeated at 1 h, 24 h, 48 h, and 72 h after the brine is injected.

3. The detection method of the local karst water storage system detection system based on well-ground multi-parameter combination according to claim 1 is characterized in that: In step E, when interpreting the results, the following method is specifically used: ① First, determine whether there is a relatively low-resistance area in the well-ground resistivity profile. A relatively low-resistance area means that the resistivity in this area is lower than that of the adjacent positions as a whole. If there is a relatively low-resistance area, the low-resistance abnormal area in the formation is defined as the spatial distribution range of the local karst water storage system; ② Delineate the main groundwater runoff layer and intensity through the natural potential logging curve: First, determine the negative offset high potential fluctuation anomaly position in the natural potential logging curve, delineate the stratum as the main runoff layer, and determine the relative magnitude of the runoff intensity through the magnitude of the potential anomaly fluctuation amplitude. If the potential anomaly fluctuation amplitude is large, the runoff intensity is relatively large. On the contrary, if the potential anomaly fluctuation amplitude is small, the runoff intensity is small. ③ By comparing the well-ground resistivity profile at different times after salt injection with the initial background profile, the area with reduced resistivity is identified as the salt water diffusion area, and the main runoff layer is determined according to the distribution position of the salt water diffusion area. The low-resistance anomaly changes in different directions of the well-ground pseudo three-dimensional resistivity profile formed by cross-line survey are used to infer the salt water diffusion direction. The salt water diffusion distance is depicted by the range of the low-resistance anomaly area at different times, and the salt water diffusion speed is further calculated. The flow velocity and direction of the salt water actually indicate the flow velocity and direction of the groundwater, and then the groundwater runoff velocity of the runoff layer is obtained; ④ The main runoff layers and brine-rich areas in the formations around the wells are interpreted by using the continuous changes in the one-dimensional resistivity, natural potential, and conductivity logging data after salt injection. Specifically, the main runoff layers and brine-rich areas in the formations near the salt injection measurement wells are determined based on the following characteristics: After the injection of brine, the logging data of the main runoff layers show the following characteristics: the abnormal fluctuation amplitude of the natural potential high potential first increases and then decreases, the resistance first decreases and then increases, and the conductivity first increases and then decreases; and the karst with poor fluidity can store brine, so the logging data show the following characteristics: the abnormal fluctuation amplitude of the natural potential high potential first increases and then decreases, the resistivity decreases and then maintains a low level, and the conductivity decreases and then maintains a low level.

4. The detection method of the local karst water storage system detection system based on well-ground multi-parameter combination according to claim 1 is characterized by: The well-ground resistivity data acquisition module is controlled by the central processing unit to connect two specific electrodes of the vertical electrode system in the well, the two specific electrodes are marked as pole A and pole B, and the other electrodes are disconnected, and current is emitted to the two specific electrodes to establish an artificial electric field; After the artificial electric field is established, the central processing unit controls the synchronous acquisition of the potential signal of each electrode of the ground electrode array; The one-dimensional natural potential data acquisition module is controlled by the central processing unit to connect two specific electrodes of the vertical electrode system in the well, the two specific electrodes are recorded as M pole and N pole, and the other electrodes are disconnected, and then the natural potential signals of the two specific electrodes are measured, each measurement uses Pi+1 and Pi+2 as the measuring electrode M and electrode N, i is the number of measurements, and finally the central processing unit uploads the data to the main control computer and stores it in the data storage module; The one-dimensional resistivity data acquisition module is controlled by the central processing unit to connect four specific electrodes in all stainless steel electrode rings of the well electrode system, the four specific electrodes are recorded as pole A, pole B, pole M and pole N, and the other electrodes are disconnected, and current is emitted to the two specific electrodes of pole A and pole B to establish an artificial electric field; After the artificial electric field is established, the central processing unit controls the synchronous acquisition of the potential signals of the remaining two electrodes, the M pole and the N pole, and finally the central processing unit uploads the data to the main control computer and stores it in the data storage module; The one-dimensional conductivity data acquisition module is controlled by the central processing unit to collect signals from all conductivity sensors in the well in parallel to obtain the conductivity value of the well water and further draw a distribution curve of conductivity with depth.

5. The detection method of the local karst water storage system detection system based on well-ground multi-parameter combination according to claim 1 is characterized by: When collecting in-well resistivity data through the well-ground resistivity data acquisition module, the following methods are used: The power supply scheme consists of four power supply pair arrangement modes: fixed pole spacing of 1m, 10m, 20m and variable pole spacing of 1-50m, specifically: ① The pole spacing is 1m, pole A is P1 and pole B is P2, moving to pole A P2 and pole B P3, and so on, until the last electrode; ② The pole spacing is 10m, pole A is P1 and pole B is P11, moving to pole A P2 and pole B P12, and so on, until the last electrode; ③ The pole spacing is 20m, pole A is P1 and pole B is P21, moving to pole A P2 and pole B P22, and so on, until the last electrode; ④ Variable pole spacing is 1-50m, pole A is P1 and pole B is P50, moving to pole A P2 and pole B P50, and so on, until the last electrode.

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