Method and device for monitoring in situ the salt release capacity of a brine well

Abstract

The application provides a monitoring method and device for monitoring salt release capacity of a brine well in situ, and belongs to the field of hydrogeological monitoring. In view of the problem that the prior art is difficult to distinguish the salt source and release horizon, the application is based on the natural potential detection technology in the well, especially suitable for monitoring the salt release of the weakly permeable layer in the coastal brine mining area, so as to implement the in-situ and layered dynamic monitoring of the salt release of different horizons of the brine well, thereby simplifying the construction means, reducing the monitoring cost and having a good popularization and application prospect. Specifically, an electrical cable is vertically arranged along the well wall in the pumping well, a plurality of electrodes are arranged on the electrical cable at intervals, and the electrical cable is tightly attached to the well wall through a fixing mechanism; the natural potential data on the vertical profile are collected, the electrochemical potential change caused by the salt release is utilized, the potential anomaly at different depths is captured, the dominant horizon of the salt release in the weakly permeable layer is located and identified, and the relative rate of the salt release of each horizon is inversely estimated.

Description

Technical Field

[0001] This application relates to the field of hydrogeological monitoring, specifically proposing a method and device for in-situ monitoring of the salinity release capacity of brine wells based on distributed spontaneous potential. Background Technology

[0002] The underground brine areas distributed along my country's coast are important salt resource producing areas, rich in useful components such as sodium chloride, potassium chloride, and bromine. They are raw material sources for industries such as salt chemical industry and bromine extraction, and have extremely high economic value.

[0003] In recent years, with the continuous large-scale mining activities, shallow brine resources have gradually become depleted, and mining depths and intensity have been continuously increasing. Long-term field exploration and sampling tests have revealed the widespread distribution of low-permeability, weakly permeable layers within brine aquifer systems. While these weakly permeable layers cannot directly produce brine, their porous media contain extremely high concentrations of salt, with a mineralization often significantly higher than adjacent mined aquifers. Under intense mixed mining conditions, the drop in water level in pumping wells creates a vertical hydraulic gradient, driving the slow release of high-salt water from the weakly permeable layers into the mining wells, resulting in dynamic changes in brine concentration. This salt release, driven by the concentration gradient, generates an electrochemical potential anomaly. This potential can be captured non-contactly using downhole electrode arrays, theoretically providing a physical basis for in-situ stratified monitoring.

[0004] However, existing monitoring methods have significant technical limitations: conventional methods often rely on wellhead mixed water sampling and analysis, which can only obtain the overall average concentration of salinity in the mining section. They cannot distinguish whether the salinity originates from the high-permeability main mining layer or from the low-permeability weakly permeable layer, let alone identify which specific weakly permeable layer is contributing salinity. This "source ambiguity" severely restricts the accuracy of brine resource assessment and the optimization of mining strategies.

[0005] While existing technologies utilize spontaneous potential methods to monitor seawater intrusion or groundwater pollution, most employ surface electrode placement, resulting in low spatial resolution and difficulty in achieving downhole stratified positioning. Although some downhole electrode monitoring devices exist, they generally suffer from problems such as difficulty in maintaining stable electrode adhesion to the wellbore during pumping, interference from pumping disturbances in the current potential, and the inability to achieve in-situ aeration for fixation. Furthermore, some existing in-situ measurement devices use conductivity probes to directly measure pore liquid salinity, requiring the liquid to be drawn into the measurement chamber, leading to interlayer liquid mixing and contamination, and making them unsuitable for deep pumping wells.

[0006] Therefore, there is an urgent need to develop a method that can monitor the release of salt from weakly permeable layers in brine wells in situ, in layers, and dynamically, so as to accurately identify the dominant release layers and provide a scientific basis for the sustainable exploitation of coastal brine resources. Summary of the Invention

[0007] In view of this, the purpose of this application is to solve the problem that the existing technology is difficult to distinguish the source and release layer of salt. It proposes an in-situ dynamic monitoring solution based on the in-well spontaneous potential detection technology, which is particularly suitable for the layered salt release of weakly permeable layers in coastal brine mining areas. The aim is to implement in-situ and layered dynamic monitoring of salt release from different layers in brine wells, thereby simplifying construction methods, reducing monitoring costs, and having good prospects for promotion and application.

[0008] To achieve the aforementioned objective, the in-situ monitoring method for the salt release capacity of brine wells involves laying an electrical cable vertically along the well wall in the pumping well, with multiple electrodes spaced apart on the cable, and securing it tightly to the well wall using a fixing mechanism. By collecting natural potential data from the vertical profile, the method utilizes the electrochemical potential changes caused by salt release to capture potential anomalies at different depths, thereby locating and identifying the dominant salt release layers in the weakly permeable layer, and inverting to estimate the relative salt release rate of each layer.

[0009] The monitoring method includes the following implementation process: Step S1: Deployment of monitoring devices; Step S2: Acquisition of natural potential data; The pumping equipment of the pumping well is started. Under stable pumping conditions, the natural potential signals of each electrode are continuously collected through the data acquisition unit to obtain the potential values ​​at different depths. Step S3: Data processing and identification of salinity release layers; The spontaneous potential data is processed to identify the layers where salt is released from the weakly permeable layer based on the potential changes at different depths. The natural potential gradient between adjacent electrodes is calculated, and the gradient value is normalized to eliminate systematic errors caused by different electrode spacings. The gradient value in the aquifer section with no obvious salt release is used as the background baseline. The depth range exceeding the preset threshold is marked as the salt release abnormal layer, and the layer with the strongest abnormal intensity is determined as the dominant release layer. Step S4: Semi-quantitative inversion of salt release rate; Based on the natural potential anomaly amplitude of each layer and combined with the pre-established relationship model, the relative rate of salt release of the corresponding layer is inverted. The relationship model establishes the correspondence between the change in natural potential and the change in ion concentration based on the diffusion-adsorption potential theory, or establishes the correspondence by on-site calibration at strata with known salt concentrations; Chloride ion concentration was used as a characterization index for salt release to assess the salt release intensity at each layer. Step S5: Application of monitoring results; Based on the advantageous release layers identified in the above steps, applications are made to optimize mining plans, accurately locate monitoring points, and conduct resource assessments.

[0010] In step S1, an electrical cable is vertically laid along the well wall inside the pumping well. A fixing mechanism is set between or near every two electrodes on the electrical cable. The fixing mechanism is an inflatable flexible air bladder. When the electrical cable is lowered, all floats are in an uninflated and contracted state. After the electrical cable is lowered into place, compressed air is injected into the air pipe through the control unit at the wellhead, so that all floats are inflated and expanded synchronously. The expanded floats are tightly pressed against the well wall, firmly attaching the electrical cable and its electrodes to the well wall.

[0011] In step S2, the sampling frequency is set to 0.1-10Hz according to the monitoring requirements. The reference electrode set on the wellhead surface or the wellhead casing is used as the reference potential, and the potential difference of each electrode relative to the reference electrode is recorded. The acquisition time is determined according to the monitoring purpose: short-term monitoring can be continuously acquired for several hours to several days; long-term monitoring can be set to periodic acquisition.

[0012] Step S3 includes, Step S3.1: Preprocess the collected natural potential data; High-frequency noise interference is removed by wavelet transform or low-pass filtering; the actual immersion depth of the electrodes is corrected according to the water level change during the pumping process; the potential change of each electrode is calculated with the initial potential value before the start of pumping or after the pumping has stabilized as the baseline. Step S3.2: Plot the curve of the natural potential gradient as a function of depth; According to the spontaneous potential formation mechanism, when high concentrations of salt are released from a weakly permeable layer into the wellbore, an electrochemical potential anomaly is generated under the drive of the concentration gradient, resulting in a significant potential gradient anomaly in that depth range. The specific calculation process and criteria for stratigraphic division include, Step S3.2.1: Standardization of the natural potential gradient; To eliminate systematic errors caused by different electrode spacings, the original potential gradient is normalized, and a standardized gradient is defined: in, For the first Normalized potential gradient at the measuring point, in mV / m; This represents the potential difference between two adjacent electrodes, expressed in mV. For the first With the The vertical distance between electrodes, in meters; Step S3.2.2: Determination of background values ​​and anomaly thresholds; The background mean was calculated using the gradient values ​​of all measuring points located within a pure aquifer zone where no significant salt release was confirmed. Standard deviation of background : ; in, The number of valid measurement points within the reference layer segment. The standardized gradient values ​​for each measuring point in the reference layer; Anomaly detection threshold Set as: When the standardized gradient of a certain depth range Exceed At that time, this region was initially marked as an anomalous salt release layer; Step S3.2.3: Identification and division of advantage release layers; Among all the initially marked anomalous layers, dominant layers are identified and classified.

[0013] In step S3.1, the natural potential gradient between adjacent electrodes is calculated using the following formula: ; in, For the first The first electrode and the second Potential difference between the electrodes and These are the potential values ​​of the corresponding electrodes.

[0014] Step S3.2.3 involves identifying and classifying dominant strata according to the following steps: The first step is to merge consecutive anomaly intervals; anomaly measuring points that are vertically adjacent and have the same gradient sign will be merged into the same candidate layer to avoid artificially dividing the same weakly permeable layer due to large electrode spacing. The second step is to calculate the overall anomaly intensity of each candidate layer. : in, For the first The set of measurement points contained in each candidate layer; This corresponds to the electrode spacing; The cumulative potential anomaly contributed by the stratum across the entire monitoring depth range in a physical sense is expressed in mV and can be used as a relative proxy for the intensity of salt release. The third step is sorting and partitioning; the candidate strata are then sorted according to... Sort from largest to smallest, the layer with the highest comprehensive anomaly intensity is determined as the primary dominant release layer, followed by the secondary dominant release layer, and so on; when two adjacent candidate layers... When the difference is less than 10% of the maximum value, they can be regarded as equal contribution levels, and no distinction is made between strong and weak levels. The fourth step is to define the depth range of the stratigraphic sequence; this is done by reducing the absolute value of the abnormal gradient to a threshold. The corresponding depth is used as the upper and lower boundaries of the advantageous release layer, thus giving the burial depth range and layer thickness of the advantageous layer.

[0015] Step S4 includes inversion using empirical formulas. Based on the diffusion-adsorption potential theory, the following relationship exists between the spontaneous potential difference and the ion concentration difference: ; in, The potential difference is C1 and C2, which are the chloride ion concentrations of well water and pore water in the weakly permeable layer, respectively. K is a coefficient related to temperature, medium properties and ion activity coefficient, which needs to be determined by on-site calibration or experiment. Under the condition of diffusion potential dominance, it is about 58mV at room temperature. C1 is obtained through preliminary hydrogeological surveys or sampling analysis, and ΔV is the measured natural potential difference in the field. By calculating C2 using the above formula, the estimated chloride ion concentration of the corresponding layer can be obtained, and then the salt release intensity can be assessed. Chloride ion concentration is not obtained by direct measurement, but is estimated by inversion of potential data based on the potential theory driven by ion concentration gradient. Its accuracy depends on the accuracy of K value, the dominant mechanism of the potential formation in the field, and the degree of agreement between the field conditions and theoretical assumptions.

[0016] Step S4 includes inversion using the on-site calibration method. By simultaneously collecting water samples at different strata to measure chloride ion concentration and recording spontaneous potential data, a correlation between spontaneous potential difference and chloride ion concentration change is established, forming a calibration curve; Substituting the spontaneous potential data obtained from subsequent monitoring into the calibration curve allows for the calculation of the salt release rate at the corresponding stratum. The calibration curve can be fitted using a linear or logarithmic model, with the coefficient of determination R0. 2 ≥0.90 is the minimum acceptable quality standard for the calibration curve; Salt release rate at each layer The unit is mg / (m 2 ·d), estimated using the following formula: ; in, This represents the change in chloride ion concentration at the j-th layer, expressed in mg / L. For the first The groundwater seepage velocity at the stratum is measured in m / d and can be estimated from pumping test results or Darcy's law. The density of water is expressed in kg / L and is set to 1.0; the relative salt release intensity index is defined. : in, Release the total number of layers for the identified advantages; Indicates the first The percentage of salt release from a given stratum relative to the total salt release from all dominant strata directly reflects the relative contribution of each stratum, providing a quantitative basis for optimizing mining sections.

[0017] Based on the application of the above-mentioned in-situ monitoring method for brine well salinity release capacity, this application also proposes an in-situ monitoring device for brine well salinity release capacity, which includes: Electrical cables are used for vertical installation inside pumping wells; Multiple electrodes are spaced apart on the electrical cable to collect natural potential signals; Multiple fixing mechanisms are installed on the electrical cable, which have a retracted state and an open state, and are used to fix the electrical cable to the well wall in the open state; The control unit is connected to each fixing mechanism and is used to control the switching of the fixing mechanism between the retracted state and the open state; The data acquisition unit is electrically connected to each electrode to acquire and record natural potential data.

[0018] In summary, the beneficial effects and advantages of this application compared with the prior art include: 1. This application proposes an in-situ monitoring scheme that can realize in-situ monitoring of salt release at different depths of pumping wells, accurately locate the dominant layer for salt release in weakly permeable layers, and further invert the relative rate of salt release at each layer. It effectively solves the defects of ambiguous source in existing technologies. The overall scheme is simple to construct, low in cost, and accurate in monitoring results.

[0019] 2. This application achieves in-situ and stratified monitoring of salt release at different depths during pumping by vertically deploying a distributed electrode array in the pumping well and combining it with a fixing mechanism and a fixing technology, thus overcoming the technical defects of the prior art in that the source of mixed water samples is unclear.

[0020] 3. Compared with the existing technology that extracts liquid into the measuring chamber for conductivity detection, this application adopts a non-contact measurement of natural potential without extracting pore liquid, thereby effectively avoiding interlayer liquid mixing and contamination. It is more suitable for long-term dynamic monitoring of deep pumping wells, and the monitoring results are more effective and accurate.

[0021] 4. This application utilizes the natural anomalies caused by salt release. By calculating the natural potential gradient and combining it with normalization and background threshold discrimination, it can accurately locate the dominant layer for salt release in weakly permeable layers, providing a direct basis for optimizing mining sections and controlling mining intensity.

[0022] 5. This application adopts a fixing mechanism design that "contracts during lowering and opens after reaching the target position," which solves the problem of laying underground cables and achieves good adhesion between the electrodes and the well wall, avoiding signal interference caused by pumping disturbances. The device has a simple structure, is easy to construct, and has low economic cost, making it a promising candidate for widespread application.

[0023] 6. This application is not only applicable to the monitoring of salt release from weakly permeable layers in coastal brine mining areas, but can also be extended to the fields of monitoring water quality in underground saline aquifer energy storage and monitoring solute transport in contaminated sites, and has good prospects for promotion and application. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. Some specific embodiments of this application will be described in detail below with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings designate the same or similar parts or components. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale.

[0025] Figure 1 This is a schematic diagram showing the deployment of the monitoring device in the pumping well in the embodiment; Figure 2 This is a schematic diagram of a partial structure of the electrical cable in the embodiment; wherein, Figure 2 (a) is a cross-sectional view of the float in its uninflated state. Figure 2 (b) is a cross-sectional view of the float after it has been inflated and is attached to the well wall. Figure 3 This is a schematic diagram showing the curve of spontaneous potential change with depth and the identification of salt release layers; In the above attached figures, 1-pumping well; 2-electrical cable; 3-electrode; 4-float; 5-aquifer; 6-weakly permeable layer; 7-ground; 8-air inflation control unit; 9-air pipe; 10-data acquisition unit; Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0027] Example 1, as Figures 1 to 3 As shown, this application proposes a novel in-situ monitoring method for the salt release capacity of brine wells. An electrical cable 2 is vertically laid along the well wall in the pumping well 1, with multiple electrodes 3 spaced apart on the cable 2, and secured to the well wall by a fixing mechanism. By collecting natural potential data from the vertical profile, and utilizing the electrochemical potential changes caused by salt release, potential anomalies at different depths are captured, thereby locating and identifying the dominant salt release layer in the weakly permeable layer 6, and estimating the relative salt release rate of each layer. Specifically, the method includes the following implementation process: Step S1: Deployment of monitoring devices; An electrical cable 2 is vertically laid along the well wall inside the pumping well 1. The electrical cable 2 is preferably an armored cable, which integrates power supply wires and signal transmission wires. Multiple electrodes 3 are spaced on the electrical cable 2. The electrode spacing is set to 1.0 meter to 2.0 meter according to the monitoring accuracy requirements. The coverage depth range covers all aquifers 5 and weakly permeable layers 6 exposed by the pumping well. On the electrical cable 2, a fixing mechanism is installed between or near every two electrodes. The fixing mechanism uses an inflatable flexible airbag made of flexible rubber material with anti-slip texture on the surface; When the electrical cable 2 is lowered, all the floats 4 are in an uninflated and retracted state, and the electrical cable 2 is successfully lowered to the predetermined depth by its own weight; After the electrical cable 2 is lowered into place, compressed air is injected into the air pipe 9 through the air inflation control unit 8 at the wellhead, causing all floats 4 to inflate synchronously. The inflated floats 4 press tightly against the well wall, firmly attaching the electrical cable 2 and its electrodes 3 to the well wall to ensure the stability of the electrode position during subsequent pumping. The inflation pressure is preset according to the well diameter and airbag size, usually 0.1-0.3 MPa. Step S2: Acquisition of natural potential data; The pumping equipment of pumping well 1 is started. Under stable pumping conditions, the natural potential signal of each electrode 3 is continuously collected by the data acquisition unit 10 to obtain the potential value at different depths. The sampling frequency is set to 0.1-10Hz according to the monitoring requirements. The reference electrode set on the surface of the wellhead or the wellhead casing is used as the reference potential, and the potential difference of each electrode relative to the reference electrode is recorded. The data collection time is determined based on the monitoring objective: short-term monitoring can be conducted continuously for several hours to several days; long-term monitoring can be set to periodic collection, such as once a month, for 24 hours each time. Step S3: Data processing and identification of salinity release layers; The spontaneous potential data is processed to identify the layers where salt is released from the weakly permeable layer based on the potential changes at different depths. The natural potential gradient between adjacent electrodes is calculated, and the gradient value is normalized to eliminate systematic errors caused by different electrode spacings. The gradient value in the aquifer section with no obvious salt release is used as the background baseline. The depth range that exceeds the preset threshold (such as exceeding the background mean ± 2 times the standard deviation) is marked as the salt release anomalous layer. The layer with the strongest anomalous intensity is determined as the dominant release layer. Specifically, it includes: Step S3.1: Preprocess the collected natural potential data; High-frequency noise interference is removed by wavelet transform or low-pass filtering; the actual immersion depth of the electrodes is corrected according to the water level change during the pumping process; the potential change of each electrode is calculated with the initial potential value before the start of pumping or after the pumping has stabilized as the baseline. The formula for calculating the natural potential gradient between adjacent electrodes is as follows: ; in, For the first The first electrode and the second Potential difference between the electrodes and These are the potential values ​​of the corresponding electrodes; Step S3.2: Plot the curve of the natural potential gradient as a function of depth; According to the spontaneous potential formation mechanism, when high concentrations of salt are released from a weakly permeable layer into the wellbore, an electrochemical potential anomaly is generated under the drive of the concentration gradient, resulting in a significant potential gradient anomaly in that depth range. Specifically, in the salt-releasing layer, the spontaneous potential gradient exhibits significant positive or negative abrupt changes (the direction of the abrupt change depends on the direction of ion migration and the electrode polarity setting); in the pure aquifer or the weakly permeable layer with no obvious salt release, the potential gradient changes gradually with a smaller amplitude. The specific calculation process and criteria for stratigraphic division include, Step S3.2.1: Standardization of the natural potential gradient; To eliminate systematic errors caused by different electrode spacings, the original potential gradient is normalized, and a standardized gradient is defined: in, For the first Normalized potential gradient at the measuring point, in mV / m; This represents the potential difference between two adjacent electrodes, expressed in mV. For the first With the The vertical distance between electrodes, in meters; Step S3.2.2: Determination of background values ​​and anomaly thresholds; The background mean was calculated using the gradient values ​​of all measuring points located within a pure aquifer section (reference section) where no significant salt release was confirmed. Standard deviation of background : ; in, The number of valid measurement points within the reference layer segment. The standardized gradient values ​​for each measuring point in the reference layer; Anomaly detection threshold Set as: When the standardized gradient of a certain depth range Exceed At that time, this region was initially marked as an anomalous salt release layer; Step S3.2.3: Identification and division of advantage release layers; Among all the initially marked anomalous layers, the dominant layers are identified and classified according to the following steps: The first step is to merge consecutive anomaly intervals; anomaly measuring points that are vertically adjacent (with a spacing of no more than 2 electrode spacings) and have the same gradient sign are merged into the same candidate layer to avoid artificially dividing the same weakly permeable layer due to large electrode spacing. The second step is to calculate the overall anomaly intensity of each candidate layer. : in, For the first The set of measurement points contained in each candidate layer; This corresponds to the electrode spacing; The cumulative potential anomaly contributed by the stratum across the entire monitoring depth range in a physical sense is expressed in mV and can be used as a relative proxy for the intensity of salt release. The third step is sorting and partitioning; the candidate strata are then sorted according to... Sort from largest to smallest, the layer with the highest comprehensive anomaly intensity is determined as the primary dominant release layer, followed by the secondary dominant release layer, and so on; when two adjacent candidate layers... When the difference is less than 10% of the maximum value, they can be regarded as equal contribution levels, and no distinction is made between strong and weak levels. The fourth step is to define the depth range of the stratigraphic sequence; this is done by reducing the absolute value of the abnormal gradient to a threshold. The corresponding depth is used as the upper and lower boundaries of the advantageous release layer, thus giving the burial depth range and layer thickness of the advantageous layer. In summary, the examples are as follows: Assuming the monitoring well exposes depths ranging from 0 to 60 meters, the electrode spacing... =1.5m, with a total of 40 electrodes deployed. The 0-20m section is the aquifer (reference layer), and the 20-60m section contains several weakly permeable layers. The calculated background mean value for the reference layer is... =0.8mV / m, background standard deviation =0.6 mV / m, abnormal threshold =2.0 mV / m. If the normalized gradient value reaches 6.5 to 9.2 mV / m in the depth range of 28 to 33 m, and 3.1 to 4.7 mV / m in the depth range of 42 to 45 m, then calculate the comprehensive anomaly intensity of each candidate layer. Afterwards, the 28 to 33m floors The higher the value, the more it is determined to be a first-level dominant release layer; the 42 to 45m layer is determined to be a second-level dominant release layer. Step S4: Semi-quantitative inversion of salt release rate; Based on the natural potential anomaly amplitude of each layer and combined with the pre-established relationship model, the relative rate of salt release of the corresponding layer is inverted. The relationship model is based on the diffusion-adsorption potential theory to establish the correspondence between the change in natural potential and the change in ion concentration, or it can be established by on-site calibration at strata with known salt concentrations. In coastal brine systems, the main component of salt is sodium chloride, with chloride ions being the dominant anion. The concentration of chloride ions is highly positively correlated with the change in total dissolved solids (TDS). Therefore, using chloride ion concentration as a characterization index of salt release can better represent the overall salt release status. To further assess the salt release intensity of each layer, this application employs the following two semi-quantitative inversion methods: Method 1: Empirical Formula Method; Based on the diffusion-adsorption potential theory, the following relationship exists between the spontaneous potential difference and the ion concentration difference: ; in, The potential difference is C1 and C2, which are the chloride ion concentrations of well water and pore water in the weakly permeable layer, respectively. K is a coefficient related to temperature, medium properties and ion activity coefficient, which needs to be determined by on-site calibration or experiment. Under the condition of diffusion potential dominance, it is about 58mV at room temperature. In this method, C1 is obtained through prior hydrogeological surveys or sampling analysis, and ΔV is the measured natural potential difference in the field. Both are known quantities. By back-calculating C2 using the above formula, the estimated value of chloride ion concentration in the corresponding layer can be obtained, thereby assessing the intensity of salt release.

[0028] It should be noted that the chloride ion concentration in this method is not obtained by direct measurement, but is estimated by inversion of potential data based on the potential theory driven by ion concentration gradient. Its accuracy depends on the accuracy of K value, the dominant mechanism of the potential formation in the field, and the degree of agreement between the field conditions and theoretical assumptions.

[0029] Method 2: On-site calibration method; By simultaneously collecting water samples at different strata to measure chloride ion concentration and recording spontaneous potential data, a correlation between spontaneous potential difference and chloride ion concentration change is established, forming a calibration curve; Substituting the spontaneous potential data obtained from subsequent monitoring into the calibration curve allows for the calculation of the salt release rate at the corresponding strata. The calibration curve can be fitted using a linear or logarithmic model (such as one conforming to the Nernst equation form), with the coefficient of determination R0... 2 ≥0.90 is the minimum acceptable quality standard for the calibration curve; Salt release rate at each layer The unit is mg / (m 2 ·d), estimated using the following formula: ; in, This represents the change in chloride ion concentration at the j-th layer, expressed in mg / L. For the first The groundwater seepage velocity at the stratum is measured in m / d and can be estimated from pumping test results or Darcy's law. This is the density of water, expressed in kg / L, and is set to 1.0. To facilitate lateral comparisons across different strata, a relative salt release intensity index is defined. : in, Release the total number of layers for the identified advantages; Indicates the first The percentage of salt release from a given stratum relative to the total salt release from all dominant strata directly reflects the relative contribution of each stratum, providing a quantitative basis for optimizing mining sections.

[0030] Step S5: Application of monitoring results; Based on the advantageous release layers identified in the above steps, the following applications can be made: Optimize the mining plan; for the weakly permeable layer that contributes the most to salt release, appropriately reduce the pumping intensity to avoid excessively stimulating its salt release. Precise monitoring points are established, with advantageous release layers as key monitoring targets, and dynamic changes in their salinity release are regularly assessed. Resource assessment, based on the salt release rate of each layer, calculates the long-term contribution potential of the weakly permeable layer to brine salinity.

[0031] Based on the aforementioned monitoring method for in-situ monitoring of brine well salinity release capacity, this application also proposes an in-situ monitoring device, comprising: Electrical cable 2 is used for vertical installation inside pumping well 1; Multiple electrodes 3 are spaced apart on the electrical cable 2 to collect natural potential signals; Multiple fixing mechanisms are installed on the electrical cable 2, which have a retracted state and an open state, and are used to fix the electrical cable 2 to the well wall in the open state; The control unit is connected to each fixing mechanism and is used to control the switching of the fixing mechanism between the retracted state and the open state; The data acquisition unit 10 is electrically connected to each electrode 3 for acquiring and recording natural potential data; Furthermore, the fixing mechanism is an inflatable flexible airbag, the inflation medium of which is gas or liquid; each airbag can be inflated independently, or all airbags can be inflated in parallel through the same air passage. The control unit is an inflation control unit, which is connected to each airbag via air tube 9; The airbag is preferably a rubber airbag or a composite fiber airbag, and its surface is provided with anti-slip texture or rough layer; The electrical cable 2 is preferably an armored cable, which integrates power supply wires, signal transmission wires and control lines connected to the fixing mechanism. Based on the above-mentioned in-situ monitoring device, it can be applied to monitor the salt release from weakly permeable layers in coastal brine mining areas. Based on the above-mentioned in-situ monitoring device, it can be applied to the dynamic monitoring of salt content in underground brine layers or the monitoring of solute transport in contaminated sites.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for in-situ monitoring the salinity release capacity of brine wells, characterized in that: An electrical cable is laid vertically along the well wall in the pumping well. Multiple electrodes are set at intervals on the cable and are fixed to the well wall by a fixing mechanism. By collecting natural potential data on the vertical profile, the electrochemical potential changes caused by salt release are used to capture potential anomalies at different depths, thereby locating and identifying the dominant salt release layer in the weakly permeable layer, and estimating the relative salt release rate of each layer.

2. The method for monitoring the salinity release capacity of brine wells in situ according to claim 1, characterized in that: The implementation process includes the following steps: Step S1: Deployment of monitoring devices; Step S2: Acquisition of natural potential data; The pumping equipment of the pumping well is started. Under stable pumping conditions, the natural potential signals of each electrode are continuously collected through the data acquisition unit to obtain the potential values ​​at different depths. Step S3: Data processing and identification of salinity release layers; The spontaneous potential data is processed to identify the layers where salt is released from the weakly permeable layer based on the potential changes at different depths. Calculate the natural potential gradient between adjacent electrodes and normalize the gradient values ​​to eliminate systematic errors caused by different electrode spacings; Using the gradient value within the aquifer section with no obvious salt release as the background baseline, the depth range exceeding the preset threshold is marked as the salt release abnormal layer, and the layer with the strongest abnormal intensity is determined as the dominant release layer. Step S4: Semi-quantitative inversion of salt release rate; Based on the natural potential anomaly amplitude of each layer and combined with the pre-established relationship model, the relative rate of salt release of the corresponding layer is inverted. The relationship model establishes the correspondence between the change in natural potential and the change in ion concentration based on the diffusion-adsorption potential theory, or establishes the correspondence by on-site calibration at strata with known salt concentrations; Chloride ion concentration was used as a characterization index for salt release to assess the salt release intensity at each layer. Step S5: Application of monitoring results; Based on the advantageous release layers identified in the above steps, applications are made to optimize mining plans, accurately locate monitoring points, and conduct resource assessments.

3. The method for monitoring the salinity release capacity of brine wells in situ according to claim 2, characterized in that: In step S1, an electrical cable is laid vertically along the well wall inside the pumping well, and a fixing mechanism is set between or near every two electrodes on the electrical cable. The fixing mechanism is an inflatable flexible airbag. When the discharge cable is lowered, all floats are in an uninflated and retracted state; After the electrical cable is lowered into place, compressed air is injected into the air pipe through the control unit at the wellhead, causing all floats to expand synchronously. The expanded floats press tightly against the well wall, firmly attaching the electrical cable and its electrodes to the well wall.

4. The method for monitoring the salinity release capacity of brine wells in situ according to claim 2, characterized in that: In step S2, the sampling frequency is set to 0.1-10Hz according to the monitoring requirements, and the reference electrode or wellhead casing set on the wellhead surface is used as the reference potential to record the potential difference of each electrode relative to the reference electrode. The data collection time is determined based on the monitoring objective: short-term monitoring can involve continuous data collection for several hours to several days. Long-term monitoring can be set up to periodic data collection.

5. The method for monitoring the salinity release capacity of brine wells in situ according to claim 2, characterized in that: Step S3 includes, Step S3.1: Preprocess the collected natural potential data; High-frequency noise interference is removed by wavelet transform or low-pass filtering; the actual immersion depth of the electrodes is corrected according to the water level change during the pumping process; the potential change of each electrode is calculated with the initial potential value before the start of pumping or after the pumping has stabilized as the baseline. Step S3.2: Plot the curve of the natural potential gradient as a function of depth; According to the spontaneous potential formation mechanism, when high concentrations of salt are released from a weakly permeable layer into the wellbore, an electrochemical potential anomaly is generated under the drive of the concentration gradient, resulting in a significant potential gradient anomaly in that depth range. The specific calculation process and criteria for stratigraphic division include, Step S3.2.1: Standardization of the natural potential gradient; To eliminate systematic errors caused by different electrode spacings, the original potential gradient is normalized, and a standardized gradient is defined: in, For the first Normalized potential gradient at the measuring point, in mV / m; This represents the potential difference between two adjacent electrodes, expressed in mV. For the first With the The vertical distance between electrodes, in meters; Step S3.2.2: Determination of background values ​​and anomaly thresholds; The background mean was calculated using the gradient values ​​of all measuring points located within a pure aquifer zone where no significant salt release was confirmed. Standard deviation of background : ； in, The number of valid measurement points within the reference layer segment. The standardized gradient values ​​for each measuring point in the reference layer; Anomaly detection threshold Set as: When the standardized gradient of a certain depth range Exceed At that time, this region was initially marked as an anomalous salt release layer; Step S3.2.3: Identification and division of advantage release layers; Among all the initially marked anomalous layers, dominant layers are identified and classified.

6. The method for monitoring the salinity release capacity of brine wells in situ according to claim 5, characterized in that: In step S3.1, the natural potential gradient between adjacent electrodes is calculated using the following formula: ； in, For the first The first electrode and the second Potential difference between the electrodes and These are the potential values ​​of the corresponding electrodes.

7. The method for monitoring the salinity release capacity of brine wells in situ according to claim 5, characterized in that: Step S3.2.3 involves identifying and classifying dominant strata according to the following steps: The first step is to merge consecutive anomaly intervals; anomaly measuring points that are vertically adjacent and have the same gradient sign will be merged into the same candidate layer to avoid artificially dividing the same weakly permeable layer due to large electrode spacing. The second step is to calculate the overall anomaly intensity of each candidate layer. : in, For the first The set of measurement points contained in each candidate layer; This corresponds to the electrode spacing; The cumulative potential anomaly contributed by the stratum across the entire monitoring depth range in a physical sense is expressed in mV and can be used as a relative proxy for the intensity of salt release. The third step is sorting and partitioning; the candidate strata are then sorted according to... Sort from largest to smallest, the layer with the highest comprehensive anomaly intensity is determined as the primary dominant release layer, followed by the secondary dominant release layer, and so on; when two adjacent candidate layers... When the difference is less than 10% of the maximum value, they can be regarded as equal contribution levels, and no distinction is made between strong and weak levels. The fourth step is to define the depth range of the stratigraphic sequence; this is done by reducing the absolute value of the abnormal gradient to a threshold. The corresponding depth is used as the upper and lower boundaries of the advantageous release layer, thus giving the burial depth range and layer thickness of the advantageous layer.

8. The method for monitoring the salinity release capacity of brine wells in situ according to claim 2, characterized in that: Step S4 includes inversion using empirical formulas. Based on the diffusion-adsorption potential theory, the following relationship exists between the spontaneous potential difference and the ion concentration difference: ； in, The potential difference is C1 and C2, which are the chloride ion concentrations of well water and pore water in the weakly permeable layer, respectively. K is a coefficient related to temperature, medium properties and ion activity coefficient, which needs to be determined by on-site calibration or experiment. Under the condition of diffusion potential dominance, it is about 58mV at room temperature. C1 is obtained through preliminary hydrogeological surveys or sampling analysis, and ΔV is the measured natural potential difference in the field. By calculating C2 using the above formula, the estimated chloride ion concentration of the corresponding layer can be obtained, and then the salt release intensity can be assessed. Chloride ion concentration is not obtained by direct measurement, but is estimated by inversion of potential data based on the potential theory driven by ion concentration gradient. Its accuracy depends on the accuracy of K value, the dominant mechanism of the potential formation in the field, and the degree of agreement between the field conditions and theoretical assumptions.

9. The method for monitoring the salinity release capacity of brine wells in situ according to claim 4, characterized in that: Step S4 includes inversion using the on-site calibration method. By simultaneously collecting water samples at different strata to measure chloride ion concentration and recording spontaneous potential data, a correlation between spontaneous potential difference and chloride ion concentration change is established, forming a calibration curve; Substituting the spontaneous potential data obtained from subsequent monitoring into the calibration curve allows for the calculation of the salt release rate at the corresponding stratum. The calibration curve can be fitted using a linear or logarithmic model, with the coefficient of determination R0. 2 ≥0.90 is the minimum acceptable quality standard for the calibration curve; Salt release rate at each layer The unit is mg / (m 2 ·d), estimated using the following formula: ； in, This represents the change in chloride ion concentration at the j-th layer, expressed in mg / L. For the first The groundwater seepage velocity at the stratum is measured in m / d and can be estimated from pumping test results or Darcy's law. The density of water is expressed in kg / L and is set to 1.0; the relative salt release intensity index is defined. : in, Release the total number of layers for the identified advantages; Indicates the first The percentage of salt release from a given stratum relative to the total salt release from all dominant strata directly reflects the relative contribution of each stratum, providing a quantitative basis for optimizing mining sections.

10. A monitoring device for using the in-situ monitoring method for monitoring the salinity release capacity of brine wells as described in any one of claims 1 to 9, characterized in that: Electrical cables are used for vertical installation inside pumping wells; Multiple electrodes are spaced apart on the electrical cable to collect natural potential signals; Multiple fixing mechanisms are installed on the electrical cable, which have a retracted state and an open state, and are used to fix the electrical cable to the well wall in the open state; The control unit is connected to each fixing mechanism and is used to control the switching of the fixing mechanism between the retracted state and the open state; The data acquisition unit is electrically connected to each electrode to acquire and record natural potential data.

Images