Geothermal water supply source and circulation depth calculation and determination method thereof

Abstract

The invention relates to the field of geothermal water detection, and discloses a geothermal water supply source and circulation depth calculation and determination method, which is used for solving the problem of result deviation caused by influence of bottom layer heat conductivity change during geothermal water source and depth determination, and comprises the following steps of: calculating a representative index of each geothermal well; selecting a representative geothermal well according to the representative index, collecting a final geothermal water sample of the representative geothermal well, carrying out water chemical analysis on the final geothermal water sample, carrying out isotopic tracing analysis on the final geothermal water sample according to a water chemical analysis result, and regularly measuring hydrogen isotope values of a plurality of rainfall sampling points. The gradient of the hydrogen isotope changing along with the elevation is obtained, the geothermal water supply elevation is calculated according to the elevation effect of the hydrogen isotope, a distributed hydrological model is combined with GIS space analysis, the supply area range is optimized, and the scientificity and rationality of geothermal resource development are effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of geothermal water detection, and more particularly to a method for calculating and determining the recharge source and circulation depth of geothermal water. Background Art

[0002] Geothermal water refers to groundwater that has been heated by the internal heat energy of the earth's deep interior, has a certain temperature, and is rich in minerals. It is usually formed through deep circulation or crustal heat conduction and is mainly distributed in areas such as volcanic activity areas, tectonic activity zones, and sedimentary basins. The recharge source of geothermal water is mainly atmospheric precipitation, which penetrates into the ground, is heated by the geothermal gradient or geothermal anomaly area, and then rises to the surface along fault zones or permeable layers to form hot springs, hot water wells, etc. Geothermal water has extensive application values in energy, medical treatment, agriculture, and tourism due to its rich minerals and trace elements.

[0003] Geothermal water is a clean and renewable energy source. Under the background of global energy structure adjustment and sustainable development, the exploration and development of geothermal resources are particularly important. Existing technologies mainly use geological exploration and geothermal gradient measurement methods to determine the recharge source and circulation depth of geothermal water.

[0004] However, in the process of implementing the inventive technical solution in the embodiments of the present application, it is found that the above technologies have at least the following technical problems: In practical applications, traditional geological exploration methods are difficult to accurately identify the specific recharge area of groundwater, and the calculated depth of the geothermal gradient is easily affected by the change of bottom thermal conductivity, resulting in a large deviation in the results. Existing methods mostly use a single hydrochemical or geothermometer calculation method and do not comprehensively consider hydrogeology, isotope tracing, and reservoir characteristics. Summary of the Invention

[0005] In order to overcome the above defects of the prior art, the present invention provides a method for calculating and determining the recharge source and circulation depth of geothermal water to solve the problems existing in the above background art.

[0006] To achieve the above object, the present invention provides the following technical solutions: A method for determining the recharge source of geothermal water and its circulation depth, comprising the following steps: Step 1: Obtain all geothermal wells within the research area, collect initial geothermal water samples from each geothermal well, and obtain representative parameters in the initial geothermal water samples. The representative parameters include major ion concentrations, reservoir temperatures, and the stability of hydrogen and oxygen isotopes. Evaluate the representative index based on the representative parameters, and select representative geothermal wells according to the representative index; Step 2: Collect initial geothermal water samples from the representative geothermal wells, and obtain final geothermal water samples based on the initial geothermal water samples. The final geothermal water samples include geothermal water samples from each representative geothermal well; Step 3: Conduct hydrochemical analysis on the final geothermal water samples to obtain hydrochemical analysis results; Step 4: Conduct isotope tracer analysis on the final geothermal water samples according to the hydrochemical analysis results; Step 5: Use the surface water monitoring point as a reference point, measure the elevation of the reference point using GPS, and obtain the value of the geothermal water and the value of the atmospheric precipitation at the reference point; Set multiple precipitation sampling points at different elevations, regularly measure the value, establish a linear relationship with elevation, and use regression analysis to obtain the gradient of changing with elevation; Based on the elevation effect of , calculate the recharge elevation of the geothermal water according to the elevation of the reference point, the value of the geothermal water, the value of the atmospheric precipitation at the reference point, and the gradient of changing with elevation; Use a distributed hydrological model combined with GIS spatial analysis to optimize the recharge area range.

[0007] Preferably, the steps for obtaining the representative index are as follows: Set the detection time interval, obtain the major ion concentrations of each geothermal well at each detection time point within the detection time period, and calculate the hydrochemical stability coefficient according to the major ion concentrations of each geothermal well at each detection time point; Use the temperature scale to calculate the reservoir temperature of each geothermal well; Calculate the stability coefficient of hydrogen isotopes and the stability coefficient of oxygen isotopes, and perform mean calculation according to the stability coefficient of hydrogen isotopes and the stability coefficient of oxygen isotopes to obtain the hydrogen-oxygen isotope stability coefficient; Normalize the hydrochemical stability coefficient, reservoir temperature, and hydrogen-oxygen isotope stability coefficient, and evaluate the representative index according to the normalized hydrochemical stability coefficient, reservoir temperature, and hydrogen-oxygen isotope stability coefficient. The specific obtaining steps are as follows: ; In the formula, represents the representative index, represents the hydrochemical stability coefficient, represents the reservoir temperature, represents the hydrogen-oxygen isotope stability coefficient, , , The weighting coefficients of the water chemical stability coefficient, the weighting coefficient of the reservoir temperature, and the weighting coefficient of the hydrogen and oxygen isotope stability coefficient.

[0008] Preferably, the steps for obtaining the water chemical stability coefficient are as follows: According to the ion concentrations at each detection time point, calculate the standard deviation and mean of the ion concentrations within the detection time period; calculate the ratio of the standard deviation to the mean of the ion concentrations to obtain the ion coefficient of variation; obtain the ion stability coefficient based on the ion coefficient of variation and means; calculate the water chemical stability coefficient based on the ion coefficient of variation. The specific obtaining steps are as follows: ; In the formula, represents the water chemical stability coefficient, m is the total number of major ions, is the ion stability coefficient of the j-th ion.

[0009] Preferably, the steps for selecting representative geothermal wells according to the representative index are as follows: Set the number of representative geothermal wells, sort the representative indexes of each geothermal well from high to low, and select the representative geothermal wells corresponding to the number of representative geothermal wells.

[0010] Preferably, the steps for obtaining the final geothermal water sample are as follows: Collect the initial geothermal water samples from each representative geothermal well, record the wellhead elevation, water temperature, pH value, and conductivity of each geothermal well; use a standard sampling procedure and store the initial geothermal water samples in pre-cleaned high-density polyethylene bottles; perform on-site filtration and acidification on the initial geothermal water samples to obtain the final geothermal water samples.

[0011] Preferably, the steps for performing water chemical analysis on the final geothermal water sample are as follows: Perform chemical analysis on the final geothermal water sample to obtain the chemical components of the water samples of each geothermal well. The chemical components include main components, trace elements, and other physical parameters; use the Piper trilinear diagram for water chemical classification to identify the differences in chemical components between different geothermal well water samples; combine principal component analysis and cluster analysis to obtain the similarity of water chemical components.

[0012] Preferably, the steps for performing water chemical classification using the Piper trilinear diagram are as follows: Perform water chemical analysis on the final geothermal water sample, measure the concentrations of major cations and anions, and calculate the proportion of each ion concentration. The cations include , , and , and the anions include , and ; Draw a cation triangular diagram and an anion triangular diagram. The cation triangular diagram uses , , and A triangular coordinate system is formed, and each water sample point is plotted therein. The anion triangular diagram is based on , and to form a triangular coordinate system, and each water sample point is marked; the data of the two triangular diagrams are projected onto the central rhombus diagram; different hydrochemical types are identified, the similarities of each water sample are analyzed, water sample points with the same recharge source or similar water-rock interactions are found, and combined with principal component analysis or cluster analysis, the hydrochemical classification is optimized.

[0013] Preferably, the steps for isotope tracer analysis of the final geothermal water sample are as follows: Select geothermal water samples from different geothermal wells, and collect precipitation, groundwater, and surface water samples in the study area; Use gas chromatography-isotope ratio mass spectrometry to measure and , and store the samples in a sealed manner; Calculate the and values of each water sample, plot data points on the relationship diagram, and refer to the global meteoric water line to judge the recharge source of the geothermal water; Set a deviation threshold. If the deviation value of the data point from the global meteoric water line is greater than or equal to the deviation threshold, then combined with water-rock interaction simulation, judge whether there is an evaporation effect or oxygen drift caused by water-rock interaction; If the deviation value of the data point from the global meteoric water line is less than the deviation threshold, it means that the main recharge source of the geothermal water is local precipitation. If the data point is enriched in , then it is judged that the geothermal water has experienced deep circulation heating or water-rock interaction.

[0014] Preferably, the steps for optimizing the recharge area by using a distributed hydrological model combined with GIS spatial analysis are as follows: Collect hydrogeological data in the study area. The hydrogeological data includes meteorological data, topographic data, land use data, geological and hydrological data, and hydrochemical and isotope data of geothermal water; Build a distributed hydrological model applicable to the study area in hydrological modeling software according to the hydrogeological data; In GIS software, optimize the recharge area in combination with the calculation results of the hydrological model; Use the known geothermal well data to check whether the predicted recharge area by the model is consistent with the actual situation, and judge the rationality of the prediction results in combination with the geothermal gradient and changes in hydrogen and oxygen isotopes; If there is a deviation between the calculated recharge area and the measured data, then adjust the model parameters to optimize the model accuracy.

[0015] Preferably, the steps for optimizing the recharge area in combination with the calculation results of the hydrological model are as follows: Use Kriging interpolation for and Interpolate the spatial distribution to identify the recharge area. Combine the hydrochemical data classified by the Piper ternary diagram to further verify the location and boundary of the recharge area. Calculate the slope, flow direction, and flow velocity based on the DEM data, analyze how precipitation enters the recharge area through surface and subsurface seepage, and determine whether there are fault structures or dissolution channels that affect the groundwater recharge mode. Use the GIS weighted overlay analysis method to comprehensively consider the precipitation infiltration rate, geological structure, groundwater recharge rate, and spatial distribution, and surface water-groundwater interaction. Assign different data weights to calculate the geothermal water recharge area and optimize its scope.

[0016] Technical effects and advantages of the present invention: Calculate the representative index of each geothermal well, select the representative geothermal well according to the representative index, collect the final geothermal water samples of the representative geothermal well, conduct hydrochemical analysis on the final geothermal water samples, conduct isotope tracer analysis on the final geothermal water samples according to the hydrochemical analysis results, regularly measure the hydrogen isotope values of multiple precipitation sampling points to obtain the gradient of hydrogen isotope change with elevation, calculate the recharge elevation of geothermal water based on the elevation effect of hydrogen isotope, and use a distributed hydrological model combined with GIS spatial analysis to optimize the scope of the recharge area, effectively improving the scientificity and rationality of geothermal resource development. Description of the Drawings

[0017] Figure 1 It is a flow chart of a method for calculating and determining the recharge source and circulation depth of geothermal water provided by an embodiment of the present application. Detailed Embodiments

[0018] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the drawings in the present invention. In addition, the forms of the structures described in the following embodiments are merely examples, and a method for calculating and determining the recharge source and circulation depth of geothermal water involved in the present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0019] The present invention provides a method for calculating and determining the recharge source and circulation depth of geothermal water, as Figure 1 shown, including the following steps: Step 1: Obtain all geothermal wells in the study area, collect the initial geothermal water samples in each geothermal well, obtain the representative parameters in the initial geothermal water samples, the representative parameters include the main ion concentration, reservoir temperature, and the stability of hydrogen and oxygen isotopes, evaluate the representative index according to the representative parameters, and select the representative geothermal well according to the representative index; In this embodiment, it should be specifically noted that the steps for obtaining the representative index are as follows: Set the detection time interval, and obtain the main ion concentrations of each geothermal well at each detection time point within the detection time period. The main ions include , , , , , and . Calculate the hydrochemical stability coefficient based on the main ion concentrations of each geothermal well at each detection time point. Use the temperature scale to calculate the reservoir temperature of each geothermal well. Calculate the stability coefficient of hydrogen isotope and the stability coefficient of oxygen isotope. Perform mean calculation based on the stability coefficient of hydrogen isotope and the stability coefficient of oxygen isotope to obtain the hydrogen-oxygen isotope stability coefficient. The stability coefficient of hydrogen isotope and the stability coefficient of oxygen isotope use the hydrochemical stability coefficient calculation method. Normalize the hydrochemical stability coefficient, reservoir temperature, and hydrogen-oxygen isotope stability coefficient, and evaluate the representative index based on the normalized hydrochemical stability coefficient, reservoir temperature, and hydrogen-oxygen isotope stability coefficient. The specific acquisition steps are as follows: ; In the formula, represents the representative index, represents the hydrochemical stability coefficient. The hydrochemical stability coefficient measures the degree of fluctuation of the main ion concentrations in geothermal water over time. The closer the value is to 1, the more stable the hydrochemical composition is and the smaller the long-term change is. The representative index is used to evaluate whether a geothermal well can accurately reflect the recharge source and circulation characteristics of regional geothermal water. The more stable the hydrochemical composition of a geothermal well, the less affected its water quality is by external interference and the more it can represent the true characteristics of the underground reservoir. Therefore, when selecting representative geothermal wells, wells with a high hydrochemical stability coefficient are given priority. represents the reservoir temperature. The reservoir temperature reflects the highest heating temperature reached by geothermal water during the underground circulation process and is usually calculated by geochemical temperature scales. The higher the reservoir temperature, the deeper the circulation path and longer the heat exchange process the geothermal water has experienced, and the more accurately it can represent the true temperature and genetic characteristics of the underground reservoir. represents the hydrogen-oxygen isotope stability coefficient. Hydrogen-oxygen isotopes are key indicators for judging the recharge source, evaporation effect, and water-rock interaction of geothermal water. The higher the hydrogen-oxygen isotope stability coefficient, the more stable the isotope composition of the geothermal well over the long term and the less affected it is by short-term precipitation, mixing of shallow groundwater, or local environmental changes. , , The weight coefficients representing the hydrochemical stability coefficient, the weight coefficient of the reservoir temperature, and the weight coefficient of the hydrogen and oxygen isotope stability coefficient, and , 、 、 are obtained through the analytic hierarchy process, 、 、 can be 0.4, 0.3, 0.3.

[0020] In this embodiment, it should be specifically noted that the steps for obtaining the hydrochemical stability coefficient are as follows: According to the ion concentrations at each detection time point, calculate the standard deviation and mean of the ion concentrations within the detection time period based on the ion concentrations at each detection time point; Calculate the ion coefficient of variation based on the standard deviation and mean of the ion concentrations. The specific acquisition steps are as follows: ; In the formula, represents the ion coefficient of variation, represents the standard deviation, represents the mean; Calculate the ion stability coefficient based on the ion coefficient of variation. The specific acquisition steps are as follows: ; In the formula, represents the ion stability coefficient, represents the ion coefficient of variation; Calculate the hydrochemical stability coefficient based on the ion coefficient of variation. The specific acquisition steps are as follows: ; In the formula, represents the hydrochemical stability coefficient, m is the total number of major ions, is the ion stability coefficient of the jth ion.

[0021] In this embodiment, it should be specifically noted that the steps for selecting representative geothermal wells according to the representative index are as follows: Set the number of representative geothermal wells, sort the representative indexes of each geothermal well from high to low, and select the representative geothermal wells corresponding to the number of representative geothermal wells.

[0022] Step 2: Collect the initial geothermal water samples in the representative geothermal wells, and obtain the final geothermal water samples based on the initial geothermal water samples. The final geothermal water samples include the geothermal water samples in each representative geothermal well; In this embodiment, it should be specifically noted that the steps for obtaining the final geothermal water samples are as follows: Collect the initial geothermal water samples in each representative geothermal well; Record the wellhead elevation, water temperature, pH value, and conductivity of each geothermal well to analyze the basic characteristics of the water body; Adopt the standard sampling procedure and use pre-cleaned high-density polyethylene bottles or glass bottles to store the initial geothermal water samples to avoid sample contamination; Conduct on-site filtration of the initial geothermal water samples, usually using a 0.45 μm filter membrane to remove suspended particles, and acidify to fix the dissolved metal elements to obtain the final geothermal water samples.

[0023] Step 3: Conduct hydrochemical analysis on the final geothermal water samples to obtain the hydrochemical analysis results; In this embodiment, it should be specifically noted that the steps for conducting hydrochemical analysis on the final geothermal water samples are as follows: Conduct chemical analysis on the final geothermal water samples to obtain the chemical composition of the water samples of each geothermal well. The chemical composition includes major components, trace elements, and other physical parameters; Use the Piper trilinear diagram for hydrochemical classification to identify the differences in chemical composition between different geothermal well water samples; Combine principal component analysis and cluster analysis to obtain the similarity of the water chemical composition to determine the water source and evolution process of different wells.

[0024] The Piper trilinear diagram is a triangular graphical method for analyzing and classifying hydrochemical types, consisting of two triangular diagrams representing cation and anion components respectively, and a comprehensive projection rhombus diagram. This diagram reveals the chemical composition characteristics of geothermal water by comparing the ion concentration distributions of different water samples, which helps to judge the water source, mixing ratio, and water-rock interaction.

[0025] In this embodiment, it should be specifically noted that the steps for using the Piper trilinear diagram for hydrochemical classification are as follows: Conduct hydrochemical analysis on the final geothermal water samples, measure the concentrations of major cations and anions, and calculate the proportion of each ion concentration to ensure the correct projection of the data on the Piper trilinear diagram. The cations include , , and etc., and the anions include , and etc.; Draw the cation triangular diagram and the anion triangular diagram. The cation triangular diagram uses , , and to form a triangular coordinate system, and plot each water sample point in it. The anion triangular diagram uses , and Form a triangular coordinate system and mark each water sample point; Project the data of the two triangular diagrams onto the central rhombus diagram to comprehensively display the chemical characteristics of the water samples; Identify different hydrochemical types (such as type, type, etc.) to distinguish the sources and evolution characteristics of geothermal water, analyze the similarities of each water sample, find water sample points that may have the same recharge source or similar water-rock interactions, and combine principal component analysis or cluster analysis to optimize hydrochemical classification and improve classification accuracy.

[0026] Principal component analysis is a dimensionality reduction analysis method used to identify the main variables in the data to minimize information loss. It transforms multiple correlated variables into a few mutually independent principal components through linear transformation, and these principal components can retain most of the information in the data. In geothermal water chemical classification, principal component analysis can help identify the main factors affecting the chemical composition of geothermal water (such as mineral dissolution, cation exchange, mixing, etc.), and simplify complex hydrochemical data into several key variable combinations, thereby improving the accuracy and interpretability of hydrochemical classification.

[0027] Cluster analysis is an unsupervised learning method used to group samples in a dataset according to their similarities, so that the data points within the same group (cluster) have high similarity, while the data points in different groups are quite different. Common clustering methods include K-means clustering, hierarchical clustering, etc.

[0028] In geothermal water chemical classification, cluster analysis can automatically divide different types of geothermal water according to the chemical characteristics of water samples, such as deep-circulation geothermal water, mixed geothermal water, shallow groundwater, etc., thereby optimizing the classification results of the Piper ternary diagram and improving the accuracy and scientificity of hydrochemical analysis.

[0029] Step 4: Conduct isotope tracer analysis on the final geothermal water samples according to the hydrochemical analysis results; In this embodiment, it should be specifically noted that the steps for conducting isotope tracer analysis on the final geothermal water samples are as follows: Select geothermal water samples from different geothermal wells and collect precipitation, groundwater, and surface water samples in the study area; Determine using gas chromatography-isotope ratio mass spectrometry and , and store the samples sealed to avoid isotope fractionation caused by evaporation. Gas chromatography-isotope ratio mass spectrometry is a high-precision isotope analysis technique mainly used to determine the isotope ratios of light elements (such as hydrogen, carbon, oxygen, nitrogen). This method first separates the mixture using gas chromatography, allowing different compounds to enter the detection system in sequence, then converts them into simple gas forms in a combustion or pyrolysis device, and finally determines their isotope ratios using an isotope ratio mass spectrometer. In geothermal water research, gas chromatography-isotope ratio mass spectrometry is widely used for and accurate determination to judge the recharge source, evaporation, and water-rock interaction of geothermal water, providing key data support for water cycle and origin analysis; Calculate the and values of each water sample, plot the data points on the relationship diagram, and refer to the global meteoric water line: , to judge the recharge source of geothermal water. The global meteoric water line is an empirical formula describing the relationship between hydrogen and oxygen isotopes ( and ) in natural precipitation globally. This line represents the typical variation trend of the hydrogen and oxygen isotope ratios in atmospheric precipitation in different climate regions globally. It is used to study groundwater recharge sources, evaporation effects, water-rock interactions, etc. In geothermal water research, if the relationship of geothermal water falls on the global meteoric water line, it indicates that it mainly comes from atmospheric precipitation; if it deviates from the global meteoric water line, it may be affected by evaporation effects or deep circulation geothermal processes; Set a deviation threshold. If the deviation value of the data point from the global meteoric water line is greater than or equal to the deviation threshold, combined with water-rock interaction simulation, judge whether there is oxygen drift caused by evaporation effects or water-rock interactions; If the deviation value of the data point from the global meteoric water line is less than the deviation threshold, it indicates that its main recharge source is local precipitation. If the data point is enriched in , it may have experienced deep circulation heating or water-rock interactions.

[0030] Water-rock interaction simulation is a modeling method based on geochemical thermodynamics and equilibrium calculations, used to study chemical reactions such as dissolution, precipitation, ion exchange, and oxygen isotope drift that occur between groundwater and surrounding rocks during the circulation process. This simulation usually relies on geochemical calculation software such as PHREEQC and GWB, inputs hydrochemical data (such as pH, cation and anion concentrations), and mineral phase compositions, and calculates the compositional changes of the water body at different temperatures and pressures. In geothermal water research, water-rock interaction simulation can help explain why some geothermal water sample points deviate from the global meteoric water line, such as caused by the dissolution of gypsum, calcite, or the hydrolysis of silicate minerals Drift occurs. This method provides an important theoretical basis for the genetic analysis of geothermal water, the estimation of reservoir temperature, and the sustainable utilization of resources.

[0031] Step 5: Take the surface water monitoring point as a reference point, use GPS measurement to obtain the elevation of the reference point, and obtain the value of the geothermal water and the value of the atmospheric precipitation at the reference point; Set multiple precipitation sampling points at different elevations, regularly measure the value, establish the linear relationship with elevation, and use regression analysis to obtain the empirical formula for the gradient of the change with elevation. The specific acquisition steps are as follows: ; In the formula, is the gradient of the change with elevation, is the change value of the precipitation points at different elevations, is the corresponding elevation difference; Based on the elevation effect, calculate the recharge elevation of the geothermal water according to the elevation of the reference point, the value of the geothermal water, the value of the atmospheric precipitation at the reference point, and the gradient of the change with elevation. The specific acquisition steps are as follows: ; In the formula, is the recharge elevation of the geothermal water, is the elevation of the reference point, is the value of the geothermal water, is the value of the atmospheric precipitation at the reference point, is the gradient of the change with elevation; Use a distributed hydrological model combined with GIS spatial analysis to optimize the recharge area.

[0032] A distributed hydrological model is a hydrological simulation method based on spatial grid cells, used to describe water cycle processes such as precipitation, evaporation, infiltration, groundwater recharge, and surface runoff. Different from traditional empirical or conceptual models, it can finely depict the spatial heterogeneity of hydrological characteristics within a region. By inputting data such as precipitation, terrain, soil type, and land use, it can simulate the water flow paths and recharge processes in different regions. In the study of geothermal water, a distributed hydrological model can quantitatively analyze the spatio-temporal distribution of surface water recharge to groundwater, and combined with isotope tracer data, optimize the determination of the geothermal water recharge area and improve the calculation accuracy.

[0033] GIS spatial analysis is a technology that uses geographical data for visualization, calculation, and prediction, and can be used to study the distribution characteristics of terrain, surface water, and groundwater. By integrating digital elevation models, geological maps, hydrological data, and hydrochemical parameters, GIS spatial analysis can perform operations such as interpolation calculation, buffer analysis, watershed delineation, and geostatistical analysis on the study area. In the study of geothermal water recharge, GIS spatial analysis can comprehensively process hydrochemical, isotope data, and recharge elevation calculation results, thereby optimizing the spatial distribution of the recharge area and ensuring the scientificity and accuracy of recharge source analysis.

[0034] In this embodiment, it should be specifically noted that the steps for optimizing the recharge area range by using a distributed hydrological model combined with GIS spatial analysis are as follows: Collect the hydrogeological data of the study area, where the hydrogeological data includes meteorological data, topographic data, land use data, geological and hydrological data, and hydrochemical and isotope data of geothermal water; Construct a distributed hydrological model applicable to the study area in a hydrological modeling software based on the hydrogeological data; In the GIS software, optimize the recharge area in combination with the calculation results of the hydrological model; Use the known geothermal well data to check whether the recharge area predicted by the model is consistent with the actual situation, and judge the rationality of the prediction results in combination with the geothermal gradient and the change of hydrogen and oxygen isotopes; If there is a large deviation between the calculated recharge area and the measured data, adjust the model parameters to optimize the model accuracy.

[0035] In this embodiment, it should be specifically noted that the steps for optimizing the recharge area in combination with the calculation results of the hydrological model are as follows: Adopt Kriging interpolation to perform and interpolation calculation of the spatial distribution to identify possible recharge areas, and further verify the location and boundary of the recharge area in combination with the hydrochemical data classified by the Piper ternary diagram; Based on the DEM data, calculate the slope, flow direction, and flow velocity, analyze how precipitation infiltrates into the recharge area through the surface and underground, and judge whether there are fault structures or dissolution channels affecting the groundwater recharge mode; Use the GIS weighted overlay analysis method to comprehensively consider the precipitation infiltration rate, geological structure, groundwater recharge rate, and spatial distribution, and surface water-groundwater interaction, assign different data weights, calculate the most likely geothermal water recharge area, and optimize its range.

[0036] Finally, the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

[0037] As described above, the above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of changes or replacements, which should all be covered within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims described.

Claims

1. A method for calculating and determining the source of geothermal water recharge and its circulation depth, characterized in that: The following steps are involved: Step 1: Obtain all geothermal wells in the study area, collect initial geothermal water samples from each geothermal well, obtain representative parameters of the initial geothermal water samples, including main ion concentration, heat storage temperature, and hydrogen and oxygen isotope stability, evaluate the representative parameters to obtain a representative index, and select representative geothermal wells based on the representative index; Step 2: Collecting initial geothermal water samples from representative geothermal wells, and obtaining final geothermal water samples based on the initial geothermal water samples, wherein the final geothermal water samples include geothermal water samples from each representative geothermal well; Step 3: Performing water chemical analysis on the final geothermal water sample to obtain water chemical analysis results; Step 4: Based on the results of the hydrochemical analysis, perform isotope tracer analysis on the final geothermal water sample; Step 5: Use the surface water monitoring point as a reference point and use GPS to obtain the reference point elevation and geothermal water Values ​​and atmospheric precipitation at the reference point value; Set up multiple precipitation sampling points at different elevations and measure them regularly. Value, build The linear relationship between the elevation and the height is obtained by regression analysis. gradients that vary with elevation; in accordance with The elevation effect of the geothermal water is Value, reference point atmospheric precipitation Value and Calculate geothermal water recharge elevation with gradients varying with elevation; A distributed hydrological model combined with GIS spatial analysis was used to optimize the scope of the recharge area.

2. A method for calculating and determining the source of geothermal water supply and its circulation depth according to claim 1, characterized in that: The steps for obtaining the representative index are: Setting a detection time interval, obtaining the main ion concentration of each geothermal well at each detection time point within the detection time period, and calculating the water chemical stability coefficient according to the main ion concentration of each geothermal well at each detection time point; use The temperature scale calculates the thermal reservoir temperature of each geothermal well; Calculate the stability coefficient of hydrogen isotope and the stability coefficient of oxygen isotope, calculate the average value of the stability coefficient of hydrogen isotope and the stability coefficient of oxygen isotope, and obtain the stability coefficient of hydrogen and oxygen isotopes; The water chemical stability coefficient, heat storage temperature and hydrogen and oxygen isotope stability coefficient are normalized, and the representative index is obtained according to the normalized water chemical stability coefficient, heat storage temperature and hydrogen and oxygen isotope stability coefficient. The specific acquisition steps are as follows: ； In the formula, Expressed as a representative index, Expressed as the water chemical stability coefficient, is the heat storage temperature, Expressed as the hydrogen and oxygen isotope stability coefficient, , , It represents the weight coefficient of water chemical stability coefficient, the weight coefficient of heat storage temperature and the weight coefficient of hydrogen and oxygen isotope stability coefficient.

3. A method for calculating and determining the source of geothermal water supply and its circulation depth according to claim 2, characterized in that: The steps for obtaining the water chemical stability coefficient are: According to the ion concentration at each detection time point, the standard deviation and mean of the ion concentration within the detection time period are calculated; The coefficient of variation of the ion was calculated by ratioing the standard deviation of the ion concentration to the mean; The ion stability coefficient is obtained based on the ion variation coefficient and means; The water chemical stability coefficient is calculated based on the ion variation coefficient. The specific steps are as follows: ； In the formula, It is expressed as the water chemical stability coefficient, where m is the total number of main ions, is the ion stability coefficient of the jth ion.

4. A method for calculating and determining the source of geothermal water supply and its circulation depth according to claim 1, characterized in that: The steps of selecting representative geothermal wells according to the representative index are as follows: The number of representative geothermal wells is set, the representative index of each geothermal well is sorted from high to low, and the representative geothermal wells corresponding to the number of representative geothermal wells are selected.

5. A method for calculating and determining the source of geothermal water supply and its circulation depth according to claim 1, characterized in that: The final steps of obtaining the geothermal water sample are: Collect initial geothermal water samples from each representative geothermal well and record the wellhead elevation, water temperature, pH value and conductivity of each geothermal well; Standard sampling procedures were used to store initial geothermal water samples using pre-cleaned high-density polyethylene bottles; The initial geothermal water sample was filtered on site and acidified to obtain the final geothermal water sample.

6. A method for calculating and determining the source of geothermal water supply and its circulation depth according to claim 1, characterized in that: The steps of performing water chemical analysis on the final geothermal water sample are: Conduct chemical analysis on the final geothermal water samples to obtain the chemical composition of each geothermal well water sample, which includes main components, trace elements and other physical parameters; Use Piper three-line diagram to classify water chemistry and identify differences in chemical composition between water samples from different geothermal wells; Combining principal component analysis with cluster analysis, the similarity of water chemical composition was obtained.

7. A method for calculating and determining the source of geothermal water supply and its circulation depth according to claim 6, characterized in that: The steps of using the Piper three-line diagram to classify water chemistry are as follows: The final geothermal water sample was subjected to water chemical analysis to determine the concentrations of the main cations and anions and calculate the proportion of each ion concentration. The cations included , , as well as , anions include , as well as ; Draw the cation triangle diagram and the anion triangle diagram. , , as well as The triangular coordinate system is formed and each water sample point is plotted in it. The anion triangle diagram is , as well as Form a triangular coordinate system and mark each water sample point; Project the data of the two triangle graphs onto the central diamond graph; Identify different hydrochemical types, analyze the similarities of water samples, find water sample points with the same recharge source or similar water-rock interactions, and optimize hydrochemical classification by combining principal component analysis or cluster analysis.

8. A method for calculating and determining the source of geothermal water supply and its circulation depth according to claim 1, characterized in that: The steps of performing isotope tracer analysis on the final geothermal water sample are as follows: Select geothermal water samples from different geothermal wells, and collect precipitation, groundwater, and surface water samples from the study area; Gas chromatography-isotope ratio mass spectrometry and , and store the samples in sealed containers; Calculate the water sample and Value, in Plot data points on the relationship graph, refer to the global atmospheric precipitation line, and determine the source of geothermal water recharge; A deviation threshold is set. If the deviation value between the data point and the global atmospheric precipitation line is greater than or equal to the deviation threshold, the water-rock interaction simulation is combined to determine whether there is oxygen drift caused by evaporation effect or water-rock interaction. If the deviation value between the data point and the global atmospheric precipitation line is less than the deviation threshold, it means that the main source of geothermal water recharge is local precipitation. , it is judged that the geothermal water has undergone deep circulation heating or water-rock action.

9. A method for calculating and determining the source of geothermal water supply and its circulation depth according to claim 1, characterized in that: The steps of optimizing the scope of the recharge area by using the distributed hydrological model combined with GIS spatial analysis are as follows: Collect hydrogeological data of the study area, including meteorological data, topographic data, land use data, geological and hydrological data, and hydrochemical and isotopic data of geothermal water; Construct a distributed hydrological model suitable for the study area in the hydrological modeling software based on the hydrogeological data; In GIS software, the recharge area is optimized in combination with the calculation results of the hydrological model; Using known geothermal well data, we can verify whether the recharge area predicted by the model is consistent with the actual situation, and judge the rationality of the prediction results by combining geothermal gradient and hydrogen and oxygen isotope changes; If the calculated recharge area deviates from the measured data, the model parameters are adjusted to optimize the model accuracy.

10. A method for calculating and determining the source of geothermal water supply and its circulation depth according to claim 9, characterized in that: The steps for optimizing the recharge area in combination with the calculation results of the hydrological model are as follows: Using Kriging interpolation, and The spatial distribution of water was interpolated to identify the recharge area, and the location and boundaries of the recharge area were further verified by combining the water chemistry data classified by the Piper three-line diagram; Calculate the slope, flow direction, and flow velocity based on DEM data, analyze how precipitation enters the recharge area through surface and underground seepage, and determine whether there are fault structures or dissolution channels that affect the groundwater recharge pattern; The GIS weighted overlay analysis method is used to comprehensively consider precipitation infiltration rate, geological structure, groundwater recharge rate, and Spatial distribution and surface water-groundwater interaction are considered, different data weights are assigned, geothermal water recharge areas are calculated, and their extent is optimized.

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