Geothermal water recharge source and its circulation depth calculation and determination method

Abstract

The application relates to the field of geothermal water detection, and discloses a geothermal water supply source and a method for calculating and determining the circulation depth of the geothermal water supply source, which is used for solving the problem that the result is deviated due to the influence of the change of the bottom heat conductivity when the geothermal water source and the depth are determined. The method comprises the following steps: 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, performing water chemical analysis on the final geothermal water sample, performing isotope tracing analysis on the final geothermal water sample according to the water chemical analysis result, regularly measuring hydrogen isotope values of a plurality of precipitation sampling points, obtaining a gradient of the hydrogen isotope with the change of the elevation, calculating the supply elevation of the geothermal water according to the elevation effect of the hydrogen isotope, and optimizing the supply area range by using a distributed hydrological model combined with GIS spatial analysis, so that the scientificity and rationality of geothermal resource development are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of geothermal water detection, and more specifically to a method for calculating and determining the source of geothermal water recharge and its circulation depth. Background Technology

[0002] Geothermal water refers to groundwater deep underground that has been heated by the Earth's internal heat, possessing a certain temperature and rich in minerals. It typically forms through deep circulation or crustal heat conduction and is mainly distributed in volcanic areas, tectonic zones, and sedimentary basins. The primary source of geothermal water is atmospheric precipitation, which infiltrates underground, is heated by geothermal gradients or geothermal anomalies, and then rises to the surface along fault zones or permeable layers, forming hot springs, hot water wells, etc. Due to its rich mineral and trace element content, geothermal water has wide-ranging applications in energy, medicine, agriculture, and tourism.

[0003] Geothermal water is a clean and renewable energy source, and its exploration and development are particularly important in the context of global energy structure adjustment and sustainable development. Current technologies mainly employ geological exploration and geothermal gradient measurement methods to determine the source and circulation depth of geothermal water.

[0004] However, in the process of implementing the inventive technical solution in the embodiments of this application, it was found that the above-mentioned technology has at least the following technical problems:

[0005] In practical applications, traditional geological exploration methods are difficult to accurately identify specific groundwater recharge areas, and the depth of low-temperature gradient calculations is easily affected by changes in the thermal conductivity of the underlying layer, resulting in large deviations in the results. Existing methods mostly use a single hydrochemical or temperature scale calculation method, failing to comprehensively consider hydrogeology, isotope tracing, and thermal reservoir characteristics. Summary of the Invention

[0006] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for calculating and determining the source of geothermal water supply and its circulation depth, so as to solve the problems existing in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for determining the source of geothermal water recharge and its circulation depth includes the following steps: Step 1: Obtain all geothermal wells within the study area, collect initial geothermal water samples from each well, and obtain representative parameters from the initial geothermal water samples. Representative parameters include the main ion concentration, reservoir temperature, and hydrogen and oxygen isotope stability. A representative index is obtained based on the representative parameters, and representative geothermal wells are selected based on 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: Perform hydrochemical analysis on the final geothermal water samples to obtain the hydrochemical analysis results. Step 4: Perform isotope tracer analysis on the final geothermal water samples based on the hydrochemical analysis results. Step 5: Use surface water monitoring points as reference points, and use GPS to measure and obtain the elevation of the reference points to obtain the geothermal water recharge depth. Values ​​and reference points for atmospheric precipitation Value; multiple precipitation sampling points were set up at different elevations, and measurements were taken regularly. Value, Establish The linear relationship between elevation and data is obtained using regression analysis. Gradient as a function of elevation; based on The elevation effect, based on the reference point elevation and geothermal water... Values, reference points for atmospheric precipitation value and The geothermal recharge elevation is calculated based on the gradient of elevation variation; the recharge area is optimized by using a distributed hydrological model combined with GIS spatial analysis.

[0009] Preferably, the representative index acquisition step is as follows: setting a detection time interval, acquiring the main ion concentration of each geothermal well at each detection time point within the detection time interval, and calculating the water chemical stability coefficient based on the main ion concentration of each geothermal well at each detection time point; using... The thermal scale is used to calculate the reservoir temperature for each geothermal well; the stability coefficients of hydrogen and oxygen isotopes are calculated, and the average of these coefficients is used to obtain the hydrogen and oxygen isotope stability coefficients; the water chemical stability coefficient, reservoir temperature, and hydrogen and oxygen isotope stability coefficients are normalized, and a representative index is obtained based on the normalized water chemical stability coefficient, reservoir temperature, and hydrogen and oxygen isotope stability coefficients. The specific steps for obtaining this index are as follows: In the formula, Represented as a representative index, Expressed as the water chemical stability coefficient, Represented as thermal storage temperature, Expressed as the stability coefficient of hydrogen and oxygen isotopes, , , The weighting coefficients represent the water chemical stability coefficient, the thermal storage temperature, and the hydrogen and oxygen isotope stability coefficients.

[0010] Preferably, the step of obtaining the water chemical stability coefficient is as follows: based on the ion concentration at each detection time point, calculate the standard deviation and mean of the ion concentration within the detection time period; calculate the ion variation coefficient by comparing the standard deviation and mean of the ion concentration; obtain the ion stability coefficient based on the ion variation coefficient and the method; and calculate the water chemical stability coefficient based on the ion variation coefficient. The specific steps for obtaining the water chemical stability coefficient are as follows: In the formula, Expressed as the water chemical stability coefficient, where m is the total number of major ions. Let be the ionic stability coefficient of the j-th ion.

[0011] Preferably, the step of selecting representative geothermal wells based on the representative index is as follows: set the number of representative geothermal wells, sort the representative index of each geothermal well from high to low, and select the corresponding number of representative geothermal wells.

[0012] Preferably, the final geothermal water sample acquisition step is as follows: 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; use a standard sampling procedure to store the initial geothermal water samples in pre-cleaned high-density polyethylene bottles; filter the initial geothermal water samples on-site and acidify them to obtain the final geothermal water samples.

[0013] Preferably, the step of performing hydrochemical analysis on the final geothermal water sample is as follows: performing chemical analysis on the final geothermal water sample to obtain the chemical composition of each geothermal well water sample, including principal components, trace elements and other physical parameters; using Piper trilinear plots to classify hydrochemicals and identify differences in chemical composition between different geothermal well water samples; and combining principal component analysis and cluster analysis to obtain the similarity of hydrochemical composition.

[0014] Preferably, the step of using the Piper trilinear diagram for water chemical classification includes: performing water chemical analysis on the final geothermal water sample, determining the concentrations of major cations and anions, and calculating the concentration ratio of each ion, including cations. , , as well as Anions include , as well as Draw cation and anion triangle diagrams, with the cation triangle diagram using... , , as well as A triangular coordinate system is formed, and each water sample point is plotted within it. The anion triangular diagram is based on... , as well as A triangular coordinate system is constructed, and each water sample point is labeled. The data from the two triangular diagrams are projected onto the central rhombus diagram. Different water chemical types are identified, the similarity of each water sample is analyzed, and water sample points with the same recharge source or similar water-rock interaction are found. Combined with principal component analysis or cluster analysis, the water chemical classification is optimized.

[0015] Preferably, the step of performing isotope tracer analysis on the final geothermal water samples is as follows: selecting geothermal water samples from different geothermal wells, and collecting precipitation, groundwater, and surface water samples from the study area; and using gas chromatography-isotope ratio mass spectrometry to determine the isotope tracer analysis results. and The samples were sealed and stored; the values ​​of each water sample were calculated. and Value, in Data points are plotted on a relationship diagram, and the source of geothermal water recharge is determined by referencing the global precipitation line. A deviation threshold is set; if the deviation of a data point from the global precipitation line is greater than or equal to the threshold, the presence of evaporation effects or oxygen drift caused by water-rock interactions is determined in conjunction with water-rock interaction simulations. If the deviation of a data point from the global precipitation line is less than the threshold, it indicates that the main source of geothermal water recharge is local precipitation, and if the data point is enriched... If so, it can be determined that the geothermal water has undergone deep circulation heating or water-rock interaction.

[0016] Preferably, the step of optimizing the recharge area using a distributed hydrological model combined with GIS spatial analysis is as follows: collecting 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; constructing a distributed hydrological model suitable for the study area in hydrological modeling software based on the hydrogeological data; optimizing the recharge area in GIS software based on the calculation results of the hydrological model; verifying whether the recharge area predicted by the model is consistent with the actual area using known geothermal well data, and judging the rationality of the prediction results by combining geothermal gradient and hydrogen and oxygen isotope changes; if there is a deviation between the calculated recharge area and the measured data, adjusting the model parameters and optimizing the model accuracy.

[0017] Preferably, the step of optimizing the recharge area based on the hydrological model calculation results is as follows: using Kriging interpolation to... and Interpolation calculations were performed on the spatial distribution to identify recharge zones. Combined with water chemistry data classified by Piper trilinear maps, the location and boundaries of the recharge zones were further verified. Slope, flow direction, and velocity were calculated based on DEM data to analyze how precipitation enters the recharge zone through surface and subsurface infiltration, determining the presence of fault structures or dissolution channels that affect groundwater recharge patterns. A GIS weighted overlay analysis method was used to comprehensively consider precipitation infiltration rate, geological structure, groundwater recharge rate, and other factors. and Spatial distribution and surface water-groundwater interaction are assigned different weights to calculate geothermal recharge areas and optimize their extent.

[0018] The technical effects and advantages of this invention are as follows:

[0019] The representative index of each geothermal well is calculated, and representative geothermal wells are selected based on the representative index. Final geothermal water samples are collected from these representative wells, and hydrochemical analysis is performed on the final geothermal water samples. Based on the hydrochemical analysis results, isotope tracer analysis is conducted on the final geothermal water samples. Hydrogen isotope values ​​at multiple precipitation sampling points are periodically measured to obtain the gradient of hydrogen isotope variation with elevation. Based on the elevation effect of hydrogen isotopes, the geothermal recharge elevation is calculated. A distributed hydrological model combined with GIS spatial analysis is used to optimize the recharge area, effectively improving the scientific rigor and rationality of geothermal resource development. Attached Figure Description

[0020] Figure 1 A flowchart illustrating a method for calculating and determining the source of geothermal water recharge and its circulation depth, provided in an embodiment of this application. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The geothermal water recharge source and its circulation depth calculation and determination method involved in the present invention are not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a method for calculating and determining the source of geothermal water recharge and its circulation depth, such as... Figure 1 As shown, it includes the following steps:

[0023] Step 1: Obtain all geothermal wells in the study area, collect initial geothermal water samples from each geothermal well, and obtain representative parameters from the initial geothermal water samples. Representative parameters include the main ion concentration, reservoir temperature, and hydrogen and oxygen isotope stability. Evaluate the representative index based on the representative parameters, and select representative geothermal wells based on the representative index.

[0024] In this embodiment, it should be specifically explained that the representativeness index acquisition step is as follows:

[0025] Set a detection time interval to obtain the main ion concentration of each geothermal well at each detection time point within the detection time interval. The main ions include , , , , , as well as The water chemical stability coefficient is calculated based on the main ion concentration of each geothermal well at each detection time point.

[0026] use The temperature scale is used to calculate the reservoir temperature of each geothermal well.

[0027] The stability coefficients of hydrogen isotopes and oxygen isotopes are calculated. The average of the stability coefficients of hydrogen isotopes and oxygen isotopes is used to calculate the stability coefficients of hydrogen and oxygen isotopes. The stability coefficients of hydrogen isotopes and oxygen isotopes are calculated using the water chemical stability coefficient calculation method.

[0028] The water chemical stability coefficient, thermal reservoir temperature, and hydrogen and oxygen isotope stability coefficients were normalized. A representative index was then obtained based on the normalized water chemical stability coefficient, thermal reservoir temperature, and hydrogen and oxygen isotope stability coefficients. The specific steps for obtaining this index are as follows:

[0029] ;

[0030] In the formula, Represented as a representative index, The hydrochemical stability coefficient measures the degree of fluctuation in the concentration of major ions in geothermal water over time. A value closer to 1 indicates a more stable hydrochemical composition and less long-term variation. The representativeness index is used to assess whether a geothermal well accurately reflects the regional geothermal water recharge source and circulation characteristics. Geothermal wells with more stable hydrochemicals are less affected by external disturbances and better represent the true characteristics of underground geothermal reservoirs. Therefore, when selecting representative geothermal wells, wells with high hydrochemical stability coefficients should be given priority. Expressed as reservoir temperature, this reflects the highest heating temperature reached by geothermal water during its underground circulation, and is usually calculated using the geochemical temperature scale. A higher reservoir temperature indicates a deeper circulation path and a longer heat exchange process, thus more accurately representing the true temperature and genetic characteristics of the underground reservoir. This is expressed as the hydrogen and oxygen isotope stability coefficient. Hydrogen and oxygen isotopes are key indicators for determining the source of geothermal water recharge, evaporation effect, and water-rock interaction. A higher hydrogen and oxygen isotope stability coefficient indicates that the geothermal well's isotopic composition is stable over the long term and less affected by short-term precipitation, shallow groundwater mixing, or local environmental changes. , , The weighting coefficients represent the water chemical stability coefficient, the thermal reservoir temperature, and the hydrogen and oxygen isotope stability coefficients. , , , Obtained through the Analytic Hierarchy Process (AHP). , , It can be 0.4, 0.3, or 0.3.

[0031] In this embodiment, it should be specifically explained that the steps for obtaining the water chemical stability coefficient are as follows:

[0032] Based on the ion concentration at each detection time point, the standard deviation and mean of the ion concentration within the detection time period are calculated.

[0033] The coefficient of variation of ions is calculated based on the standard deviation and mean of ion concentrations. The specific steps for obtaining this coefficient are as follows:

[0034] ;

[0035] In the formula, It is expressed as the coefficient of variation of ions. Expressed as standard deviation, Expressed as the mean;

[0036] The ion stability coefficient is calculated based on the ion variation coefficient. The specific steps for obtaining this coefficient are as follows:

[0037] ;

[0038] In the formula, It is expressed as the ionic stability coefficient. Expressed as the ion variation coefficient;

[0039] The chemical stability coefficient of water is calculated based on the ion variation coefficient. The specific steps for obtaining this coefficient are as follows:

[0040] ;

[0041] In the formula, Expressed as the water chemical stability coefficient, where m is the total number of major ions. Let be the ionic stability coefficient of the j-th ion.

[0042] In this embodiment, it should be specifically explained that the step of selecting representative geothermal wells based on the representative index is as follows:

[0043] Set a representative number of geothermal wells, sort the representative index of each geothermal well from high to low, and select the representative geothermal wells corresponding to the number of representative geothermal wells.

[0044] Step 2: Collect initial geothermal water samples from 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.

[0045] In this embodiment, it should be specifically explained that the final geothermal water sample acquisition step is as follows:

[0046] Initial geothermal water samples were collected from each representative geothermal well.

[0047] Record the wellhead elevation, water temperature, pH value, and electrical conductivity of each geothermal well to analyze the basic characteristics of the water body;

[0048] Standard sampling procedures were adopted, and initial geothermal water samples were stored in pre-cleaned high-density polyethylene bottles or glass bottles to avoid sample contamination.

[0049] The initial geothermal water sample is filtered on-site, typically using a 0.45 μm filter membrane, to remove suspended particles, and then acidified to fix dissolved metal elements, resulting in the final geothermal water sample.

[0050] Step 3: Perform hydrochemical analysis on the final geothermal water sample to obtain the hydrochemical analysis results;

[0051] In this embodiment, it should be specifically explained that the steps for hydrochemical analysis of the final geothermal water sample are as follows:

[0052] Chemical analysis was performed on the final geothermal water samples to obtain the chemical composition of each geothermal well water sample, including the main components, trace elements and other physical parameters.

[0053] Piper triline plots were used to classify water chemistry in order to identify differences in chemical composition among water samples from different geothermal wells.

[0054] By combining principal component analysis and cluster analysis, the similarity of water chemical composition can be obtained to determine the water source and evolution process of different wells.

[0055] The Piper tri-line diagram is a triangular diagram used to analyze and classify water chemistry types. It consists of two triangular diagrams representing cation and anion components respectively, and a composite projected rhombus diagram. By comparing the ion concentration distribution of different water samples, this diagram reveals the chemical composition characteristics of geothermal water, which helps in determining the water source, mixing ratio, and water-rock interactions.

[0056] In this embodiment, it should be specifically explained that the steps for water chemical classification using the Piper trilinear plot are as follows:

[0057] Hydrochemical analysis was performed on the final geothermal water samples to determine the concentrations of major cations and anions, and the concentration ratio of each ion was calculated to ensure the correct projection of the data onto the Piper trilinear plot. Cations included... , , as well as Anions include... , as well as wait;

[0058] Draw cation triangle diagrams and anion triangle diagrams. The cation triangle diagram is based on... , , as well as A triangular coordinate system is formed, and each water sample point is plotted within it. The anion triangular diagram is based on... , as well as Establish a triangular coordinate system and label each water sample point;

[0059] The data from the two triangular plots are projected onto the central diamond plot to comprehensively display the chemical characteristics of the water sample;

[0060] Identify different water chemistry types (such as) type, Types, etc., are used to distinguish the source and evolution characteristics of geothermal water, analyze the similarity of various water samples, identify 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 water chemical classification and improve classification accuracy.

[0061] Principal component analysis (PCA) is a dimensionality reduction method used to identify the main variables in data to minimize information loss. It transforms multiple correlated variables into a few independent principal components through linear transformation, which retain most of the data's information. In geothermal chemical classification, PCA can help identify the main factors influencing the chemical composition of geothermal water (such as mineral dissolution, cation exchange, and mixing), and simplify complex hydrochemical data into a few key variable combinations, thereby improving the accuracy and interpretability of hydrochemical classification.

[0062] Cluster analysis is an unsupervised learning method used to group samples in a dataset based on their similarity, ensuring that data points within the same group (cluster) are highly similar, while data points in different groups are significantly different. Common clustering methods include K-means clustering and hierarchical clustering.

[0063] In geothermal chemical classification, cluster analysis can automatically classify different types of geothermal water based on the chemical characteristics of water samples, such as deep circulating geothermal water, mixed geothermal water, and shallow groundwater, thereby optimizing the classification results of Piper trilinear plots and improving the accuracy and scientific rigor of hydrochemical analysis.

[0064] Step 4: Based on the water chemical analysis results, perform isotope tracing analysis on the final geothermal water sample;

[0065] In this embodiment, it should be specifically explained that the isotope tracing analysis steps for the final geothermal water sample are as follows:

[0066] Geothermal water samples were selected from different geothermal wells, and precipitation, groundwater, and surface water samples were collected from the study area.

[0067] Gas chromatography-isotope ratio mass spectrometry was used for determination. and The samples are sealed and stored to avoid isotope fractionation caused by evaporation. Gas chromatography-isotope ratio mass spectrometry (GC-MS / MS) is a high-precision isotope analysis technique mainly used to determine the isotope ratios of light elements (such as hydrogen, carbon, oxygen, and nitrogen). This method first uses gas chromatography to separate the mixture, allowing different compounds to sequentially enter the detection system. Then, they are converted into simple gaseous forms in a combustion or pyrolysis device, and finally, their isotope ratios are determined by isotope ratio mass spectrometry. In geothermal water research, GC-MS / MS is widely used. and The precise measurement is used to determine the source of geothermal water recharge, evaporation and water-rock interaction, providing key data support for water cycle and genetic analysis;

[0068] Calculate the values ​​of each water sample and Value, in Data points are plotted on the relationship diagram, referencing the global atmospheric precipitation line: To determine the source of geothermal water replenishment, the global precipitation line describes the hydrogen and oxygen isotopes in natural precipitation worldwide. and The empirical formula for the relationship between hydrogen and oxygen isotopes in atmospheric precipitation is used to represent the typical variation trend of the hydrogen-oxygen isotope ratio in different climate zones worldwide. It is used to study groundwater recharge sources, evaporation effects, and water-rock interactions. In geothermal research, if the geothermal water... If the relationship falls on the global precipitation line, it indicates that the source is mainly atmospheric precipitation; if it deviates from the global precipitation line, it may be affected by evaporation or deep-circulation geothermal activity.

[0069] A deviation threshold is set. If the deviation of the data point from 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 an evaporation effect or oxygen drift caused by water-rock interaction.

[0070] If the deviation of a data point from the global precipitation line is less than the deviation threshold, it indicates that its main source of replenishment is local precipitation. If the data point is enriched... It may have undergone deep circulation heating or water-rock interaction.

[0071] 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 circulation. This simulation typically relies on geochemical calculation software such as PHREEQC and GWB, inputting water chemistry data (e.g., pH, cation and anion concentrations) and mineral phase composition to calculate changes in water composition under different temperatures and pressures. In geothermal water research, water-rock interaction simulation can help explain why some geothermal sampling points deviate from the global precipitation line, such as due to the dissolution of gypsum and calcite or the hydrolysis of silicate minerals. This method provides an important theoretical basis for the analysis of the formation of geothermal water, the estimation of geothermal reservoir temperature, and the sustainable utilization of resources.

[0072] Step 5: Using the surface water monitoring point as a reference point, use GPS to measure and obtain the elevation of the reference point, and obtain the geothermal water... Values ​​and reference points for atmospheric precipitation value;

[0073] Multiple precipitation sampling points were set up at different elevations, and measurements were taken regularly. Value, Establish The linear relationship between elevation and data is obtained using regression analysis. The empirical formula for the gradient that varies with elevation, and the specific steps to obtain it are as follows:

[0074] ;

[0075] In the formula, for Gradient as elevation changes For precipitation points at different elevations Change value, For the corresponding elevation difference;

[0076] in accordance with The elevation effect, based on the reference point elevation and geothermal water... Values, reference points for atmospheric precipitation value and The specific steps for calculating the geothermal recharge elevation using gradient calculations that vary with elevation are as follows:

[0077] ;

[0078] In the formula, Elevation for geothermal water recharge. For reference point elevation, Geothermal water value, Atmospheric precipitation at the reference point value, for Gradient as elevation changes;

[0079] The recharge area was optimized by using a distributed hydrological model combined with GIS spatial analysis.

[0080] Distributed hydrological models are a type of hydrological simulation method based on spatial grid cells, used to describe water cycle processes such as precipitation, evaporation, infiltration, groundwater recharge, and surface runoff. Unlike traditional empirical or conceptual models, they can finely characterize the spatial heterogeneity of hydrological features within a region. By inputting data such as precipitation, topography, soil type, and land use, they can simulate water flow paths and recharge processes in different areas. In geothermal water research, distributed hydrological models can quantitatively analyze the spatiotemporal distribution of surface water recharge on groundwater and, combined with isotope tracer data, optimize the determination of geothermal recharge areas, thereby improving computational accuracy.

[0081] GIS spatial analysis is a technique that utilizes geographic data for visualization, computation, and prediction. It can be used to study the distribution characteristics of topography, surface water, and groundwater. By integrating digital elevation models, geological maps, hydrological data, and hydrochemical parameters, GIS spatial analysis can perform interpolation calculations, buffer analysis, watershed delineation, and geostatistical analysis on the study area. In geothermal recharge research, GIS spatial analysis can comprehensively process hydrochemical and isotopic data, along with recharge elevation calculation results, thereby optimizing the spatial distribution of the recharge area and ensuring the scientific validity and accuracy of recharge source analysis.

[0082] In this embodiment, it should be specifically explained that the steps for optimizing the recharge area using a distributed hydrological model combined with GIS spatial analysis are as follows:

[0083] Collect hydrogeological data for the study area, including meteorological data, topographic data, land use data, geological and hydrological data, and hydrochemical and isotopic data of geothermal water.

[0084] A distributed hydrological model suitable for the study area was constructed using hydrogeological data in hydrological modeling software.

[0085] In GIS software, the recharge area is optimized by combining the calculation results of the hydrological model;

[0086] Using known geothermal well data, we examine 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.

[0087] If the calculated replenishment area deviates significantly from the measured data, adjust the model parameters to optimize the model accuracy.

[0088] In this embodiment, it should be specifically explained that the optimization steps for the recharge area, based on the hydrological model calculation results, are as follows:

[0089] Using Kriging interpolation, for and Interpolation calculations were performed on the spatial distribution to identify possible recharge zones. Combined with water chemistry data classified by Piper triline plots, the location and boundaries of the recharge zones were further verified.

[0090] Based on DEM data, slope, flow direction, and flow velocity are calculated to analyze how precipitation enters the recharge area through surface and underground seepage, and to determine whether there are fault structures or karst channels that affect the groundwater recharge pattern.

[0091] Using GIS weighted overlay analysis to comprehensively consider precipitation infiltration rate, geological structure, groundwater recharge rate, and Spatial distribution and surface water-groundwater interaction are assigned different weights to calculate the most likely geothermal recharge area and optimize its range.

[0092] In conclusion, the above description is only 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 the present invention should be included within the protection scope of the present invention.

[0093] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A geothermal water recharge source and a method for determining the depth of its circulation, characterized in that, The method comprises the following steps: Step 1: obtaining all geothermal wells in a research area, collecting initial geothermal water samples in each geothermal well, obtaining representative parameters in the initial geothermal water samples, the representative parameters including main ion concentration, heat reservoir temperature and hydrogen and oxygen isotope stability, evaluating a representative index according to the representative parameters, and selecting representative geothermal wells according to the representative index; Step 2: collecting the initial geothermal water samples in the representative geothermal wells, and obtaining final geothermal water samples according to the initial geothermal water samples, the final geothermal water samples including geothermal water samples in each representative geothermal well; Step 3: performing water chemical analysis on the final geothermal water samples to obtain water chemical analysis results; Step 4: performing isotope tracing analysis on the final geothermal water samples according to the water chemical analysis results; Step 5: Take the surface water monitoring point as the reference point, use GPS measurement to obtain the elevation of the reference point, obtain the value of the geothermal water and the value of the atmospheric precipitation of the reference point; Multiple precipitation sampling points were set at different elevations, and the precipitation was measured periodically The value was established The linear relationship with the elevation was obtained by regression analysis The gradient of the change with the elevation in accordance with The elevation effect, based on the reference point elevation and geothermal water... Values, reference points for atmospheric precipitation value and Calculate the geothermal recharge elevation using gradients that vary with elevation. The supply area range is optimized by using a distributed hydrological model combined with GIS spatial analysis; The step of optimizing the supply area range by using the distributed hydrological model combined with GIS spatial analysis comprises the following steps: Collecting hydrogeological data of the research area, the hydrogeological data including meteorological data, topographic data, land use data, geological and hydrological data and water chemical and isotope data of geothermal water; Building a distributed hydrological model suitable for the research area in a hydrological modeling software according to the hydrogeological data; Optimizing the supply area in a GIS software combined with the calculation results of the hydrological model; Verifying whether the predicted supply area of the model is consistent with the actual situation by using known geothermal well data, and judging the rationality of the prediction results combined with the geothermal gradient and the hydrogen and oxygen isotope variation; If there is a large deviation between the calculated supply area and the measured data, adjusting the model parameters and optimizing the model precision.

2. The method according to claim 1, wherein the method comprises the steps of: determining the recharge area of the geothermal water and the depth of the recharge area of the geothermal water. The step of obtaining the representative index comprises the following steps: Setting a detection time interval, obtaining the main ion concentration of each geothermal well at each detection time point in the detection time period, and calculating a water chemical stability coefficient according to the main ion concentration of each geothermal well at each detection time point; Using A temperature scale is used to calculate the temperature of the thermal reservoir for each geothermal well. Calculating the stability coefficients of hydrogen and oxygen isotopes, and calculating the mean value of the stability coefficients of hydrogen and oxygen isotopes to obtain a hydrogen and oxygen isotope stability coefficient; Normalizing the water chemical stability coefficient, the heat reservoir temperature and the hydrogen and oxygen isotope stability coefficient, and evaluating a representative index according to the normalized water chemical stability coefficient, the heat reservoir temperature and the hydrogen and oxygen isotope stability coefficient, and the specific obtaining steps are as follows: ； wherein is represented as a representative index, is represented as a water chemical stability coefficient, is represented as a thermal reservoir temperature, is represented as a hydrogen and oxygen isotope stability coefficient, , , is a weight coefficient of the water chemical stability coefficient, a weight coefficient of the thermal reservoir temperature, and a weight coefficient of the hydrogen and oxygen isotope stability coefficient.

3. The method for calculating and determining the source of geothermal water recharge and its circulation depth according to claim 2, characterized in that, The step of obtaining the water chemical stability coefficient comprises the following steps: According to the ion concentration at each detection time point, calculating the standard deviation and mean value of the ion concentration in the detection time period according to the ion concentration at each detection time point; Calculating the ion variation coefficient by ratio of the standard deviation and mean value of the ion concentration; Obtaining the ion stability coefficient according to the ion variation coefficient; Calculating the water chemical stability coefficient according to the ion variation coefficient, and the specific obtaining steps are as follows: ； wherein is expressed as the hydrochemical stability factor, m is the total number of major ions, is the ion stability factor of the jth ion.

4. The method according to claim 1, wherein, The step of selecting the representative geothermal wells according to the representative index comprises the following steps: Setting the number of representative geothermal wells, sorting the representative indexes of each geothermal well from high to low, and selecting the representative geothermal wells corresponding to the number of representative geothermal wells.

5. The method according to claim 1, wherein the method further comprises: determining the recharge source and the circulation depth of the geothermal water. The step of obtaining the final geothermal water samples comprises the following steps: Collecting initial geothermal water samples from each representative geothermal well, recording the wellhead elevation, water temperature, pH value and conductivity of each geothermal well; Using standard sampling procedures, using pre-cleaned high-density polyethylene bottles to store the initial geothermal water samples; Filtering and acidifying the initial geothermal water samples on site to obtain the final geothermal water samples.

6. The method according to claim 1, wherein the method further comprises: determining the recharge source and the circulation depth of the geothermal water. The water chemistry analysis of the final geothermal water samples is as follows: Chemical analysis of the final geothermal water samples to obtain the chemical composition of each geothermal well water sample, including major components, trace elements and other physical parameters; Using Piper tri-graph to classify water chemistry and identify differences in chemical composition between different geothermal well water samples; Combining principal component analysis and cluster analysis to obtain the similarity of water chemistry composition.

7. The method according to claim 6, wherein the method further comprises the steps of: determining the depth of the recharge area of the geothermal water; and determining the depth of the recharge area of the geothermal water by using the depth of the recharge area of the geothermal water. The water chemistry classification using Piper tri-graph is as follows: The final geothermal water samples are subjected to hydrochemical analysis to determine the concentrations of main cations and anions, and the proportions of the concentrations of various ions are calculated, the cations including , , and , and the anions including , and ; Draw the cation triangle and the anion triangle, the cation triangle is composed of , , and to form a triangular coordinate system, and each water sample point is plotted in the triangular coordinate system, and the anion triangle is composed of , and to form a triangular coordinate system, and each water sample point is marked. Projecting the data of two triangular graphs to the central diamond graph; Identifying different water chemistry types, analyzing the similarity of each water sample, finding out the water sample points with the same recharge source or similar water-rock interaction, combining principal component analysis or cluster analysis, and optimizing water chemistry classification.

8. The method according to claim 1, wherein the method is characterized by: The isotope tracing analysis of the final geothermal water samples is as follows: Selecting geothermal water samples from different geothermal wells and collecting precipitation, groundwater and surface water samples in the study area; Determination of the compound by gas chromatography-isotope ratio mass spectrometry and and the sample is stored sealed; The values of each water sample are calculated and The data points are plotted on a graph, and the source of the geothermal water is determined by reference to the global atmospheric precipitation line. ​ Setting a deviation threshold, if the deviation of the data point from the global atmospheric precipitation line is greater than or equal to the deviation threshold, combining water-rock interaction simulation to determine whether there is 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 value, it indicates that the main recharge source of the geothermal water is local precipitation. If the data point is enriched in 18O, it is determined that the geothermal water has undergone deep circulation heating or water-rock interaction.

9. The method according to claim 1, wherein the method is characterized by: The optimization of the recharge area based on the calculation results of the hydrological model is as follows: Using Kriging interpolation, for and Interpolation calculations were performed on the spatial distribution to identify recharge zones. Combined with water chemistry data classified by Piper triline plots, the location and boundaries of the recharge zones were further verified. Based on DEM data, calculate slope, flow direction and flow rate, analyze how precipitation infiltrates into the recharge area through surface and underground seepage, and determine whether there are fault structures or dissolution channels that affect the recharge mode of groundwater. The GIS weighted overlay analysis method is used to comprehensively consider the precipitation infiltration rate, geological structure, groundwater recharge rate, and spatial distribution, and surface water-groundwater interaction, give different data weights, calculate the geothermal water recharge area, and optimize its range.

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