Hot spring mixing proportion and heat storage temperature calculation method

Abstract

The invention discloses a hot spring mixing proportion and thermal storage temperature calculation method, which comprises the following steps: selecting hot spring samples, testing representative parameters of all the selected hot spring samples, analyzing error values, determining a representative water sample according to the analysis error values, performing hydrochemical analysis on the representative water sample to determine a geothermal temperature scale, and calculating the mixing proportion and thermal storage temperature of the hot spring according to a hydrochemical analysis result. And carrying out end member mixing analysis on the determined representative water sample, calculating a cold and hot water mixing ratio, finally correcting the SiO2 concentration according to the cold and hot water mixing ratio, and calculating to obtain the final heat storage temperature. According to the method, the influence of mixing of the thermal spring water and shallow cold water in the process of exposing the thermal spring water out of the earth surface is reduced, hydrochemistry, isotope and thermal storage characteristics are comprehensively considered, determination of the thermal spring water mixing proportion and accurate calculation of the thermal storage temperature are achieved, and a basis is provided for dividing cause types of a geothermal system and evaluating geothermal energy resource potential.

Description

Technical Field

[0001] The invention relates to a method for calculating a hot spring mixing ratio and a heat storage temperature, and belongs to the technical field of hot spring water detection. Background Art

[0002] Hot springs, defined as natural outcrops of hot groundwater, are one of the most important geothermal features on the Earth's surface. Their hydrochemical and isotopic compositions can reflect the hydrogeological characteristics of a geothermal system. The reservoir temperature, the temperature of the groundwater within the reservoir, reflects the maximum temperature it can reach during its underground circulation. It is an effective method for classifying the genetic type of geothermal systems and assessing the potential of geothermal energy resources.

[0003] Generally, the thermal reservoir temperature cannot be measured directly, and geothermal temperature scales are usually used to calculate this parameter. Geothermal temperature scales mainly include the SiO2 temperature scale, the cation temperature scale, the gas temperature scale, and the isotope temperature scale. In practical applications, traditional geothermal temperature scales, such as the SiO2 temperature scale and the cation temperature scale, rely on the assumption of water-rock chemical equilibrium. However, hot spring water mixes with shallow cold water during its exposure to the surface. The SiO2 concentration is diluted by the cold water mixing, and the direct application of the temperature scale will lead to an underestimation of the thermal reservoir temperature. In addition, existing technologies mainly use the silicon enthalpy equation method and the silicon enthalpy diagram method to determine the mixing ratio of hot and cold water. Therefore, a single tracer or temperature scale calculation method fails to comprehensively consider the water chemistry, isotope and thermal reservoir characteristics, cannot accurately determine the mixing ratio of hot spring water and calculate the thermal reservoir temperature, and cannot provide a basis for classifying the genetic type of geothermal systems and evaluating the potential of geothermal energy resources. Summary of the Invention

[0004] In response to the problems existing in the above-mentioned prior art, the present invention provides a method for calculating the mixing ratio of hot springs and the heat storage temperature. This method can comprehensively consider the water chemistry, isotope and heat storage characteristics, realize the determination of the mixing ratio of hot spring water and the accurate calculation of the heat storage temperature, and provide a basis for classifying the genetic types of geothermal systems and evaluating the potential of geothermal energy resources.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for calculating hot spring mixing ratio and heat storage temperature, comprising the following steps:

[0006] S1. Obtain the geological structure characteristics, lithologic characteristics and underground hot water outcrop characteristics in the study area, and select hot spring samples;

[0007] S2. Test the representative parameters of all selected hot spring samples, including total dissolved solids (TDS), major ion concentrations, and hydrogen and oxygen stable isotope content δ 2 H and δ 18 O, obtain the analytical error value through data inspection, and determine the representative water sample based on the analytical error value;

[0008] S3. Performing hydrochemical analysis on the determined representative water sample, and selecting an appropriate hydrochemical geothermal temperature scale to calculate the initial heat storage temperature based on the hydrochemical analysis results;

[0009] S4. Based on the results of the water chemical analysis, perform end-member mixing analysis on the representative water samples identified, including data preprocessing and principal component analysis, and calculate the mixing ratio of hot and cold water;

[0010] S5. According to the mixing ratio of cold and hot water, the SiO2 concentration is corrected and the final heat storage temperature is calculated.

[0011] Furthermore, the method for selecting hot spring samples in S1 is specifically as follows:

[0012] S1.1. Set the target number of hot springs and select hot springs with different surrounding rock types in the study area, such as sandstone, limestone, basalt, granite, and gneiss, to ensure that the number of hot springs exposed in each major rock type is balanced;

[0013] S1.2. Collect samples of target hot springs, adjacent artificial geothermal wells, and surrounding rainwater and surface water;

[0014] S1.3. Record the latitude and longitude, altitude, water temperature, Eh value, pH value, and free CO2 concentration of each sampling point;

[0015] S1.4. Standard sampling procedures were used. All water samples were filtered through membrane filters and stored in pre-cleaned high-density polyethylene bottles to avoid contamination.

[0016] S1.5. A portion of the collected water samples is acidified for subsequent cation analysis, while the other portion is not acidified for indoor testing and analysis of anions, hydrogen and oxygen stable isotopes, TDS, and metasilicic acid.

[0017] Furthermore, the main ions in S2 include K + 、Na + , Ca 2+ Mg 2+ NH4 + OH - 、NO3 - 、Cl - 、HCO3 - 、CO3 2- and SO4 2- The process of obtaining the analytical error value and determining the representative water sample is as follows:

[0018] S2.1. Calculate the analytical error value based on the percentage difference. The formula is:

[0019] θ=max(δ1,δ2,δ3);

[0020] In the formula, θ represents the analysis error value, which is used to measure the accuracy of water sample data analysis, and the smaller the data is, the more reliable the data is; δ1 represents the percentage difference of the total number of milliequivalents of cations and anions, reflecting the size of the imbalance relative to the average concentration of cations and anions; δ2 represents the percentage difference of the total number of charges, reflecting the size of the imbalance relative to the average charge of cations and anions; δ3 represents the percentage difference between the calculated value and the measured value of TDS, reflecting the size of the imbalance relative to the average value of TDS;

[0021] In the formula, the calculation formula of the percentage difference is:

[0022]

[0023] In the formula, δ represents the percentage difference, σ represents the absolute difference, and μ represents the mean value;

[0024] S2.2, according to the TDS and the concentration of the main ions of each water sample, the total number of milliequivalents of cations and anions, the number of charges, and the absolute difference and mean value between the measured value and the calculated value of TDS are calculated, and the formula is:

[0025]

[0026] In the formula, ∑Cations represents the total number of milliequivalents of main cations, ∑Anions represents the total number of milliequivalents of main anions, and ∑Cations and ∑Anions are in units of meq / L; ∑Z Cations is the number of charges of cations, and ∑Z Anions is the number of charges of anions, in units of mol / L;

[0027] S2.3, eliminate water sample data with analysis error value θ>5%, and obtain representative water samples.

[0028] Further, the step of performing water chemical analysis on the determined representative water samples in S3 is:

[0029] S3.1, using a multiple rectangle graphic method for water chemical classification to identify the differences in water chemical components between different water samples, specifically:

[0030] S3.1-1, calculating the milliequivalent percentage of each ion in all representative water samples, including cations Ca 2+ , Mg 2+ , Na + , K + and anions HCO3 - , CO3 2- , SO4 2- , Cl - ;

[0031] S3.1-2, nine adjacent small rectangles are used to form a multi-rectangular coordinate system, the horizontal and vertical coordinate axes are divided into three adjacent but independent small coordinate axes, representing the milliequivalent percentage of anions and cations; the percentage of cations is projected on the horizontal coordinate axis, and the percentage of anions is projected on the vertical coordinate axis, and each water sample point is marked in the multi-rectangular coordinate system;

[0032] S3.1-3, the water chemical type is identified according to the position of the data distributed in different rectangles, and the possible mixing source of the underground hot water is preliminarily judged, that is, adjacent data may have the same source;

[0033] S3.2, the balance state of each water sample is determined by the Na-K-Mg triangular diagram, and the water chemical geothermal temperature scale is determined in combination with the saturation index, specifically:

[0034] The water sample data points are plotted in the Na-K-Mg triangular diagram, and the water-rock balance state is judged according to the distribution area, including the completely balanced area, the partially balanced area and the immature water area;

[0035] For the water sample located in the completely balanced area or the partially balanced area, the cation geothermal temperature scale is used to estimate the initial heat reservoir temperature;

[0036] For the water sample located in the immature water area, the saturation index SI of the water sample to SiO2 mineral is calculated by using the geochemical simulation software, when the saturation index SI≈0, it indicates that the mineral is close to equilibrium with the water body, and the corresponding SiO2 geothermal temperature scale is applicable, when the saturation index SI>0 or SI<0, it indicates that the mineral is in a supersaturated or unsaturated state, then the mineral with a saturation index closer to 0 is selected as the geothermal temperature scale;

[0037] S3.3, according to the determined applicable temperature scale, the initial heat reservoir temperature of all representative water samples is calculated.

[0038] Further, the step of calculating the mixing ratio of cold and hot water in S4 is:

[0039] S4.1, by standardizing the input data for pretreatment, a conservative tracer is selected:

[0040] S4.1-1, the input data is standardized for pretreatment, and the expression is:

[0041]

[0042] In the formula, X ij and respectively represent the water chemical data matrix of the water sample and the standardized value matrix thereof, wherein i is the i-th sample, and j is the j-th solute; is the average value of the j-th solute, and S j is the standard deviation of the j-th solute;

[0043] S4.1-2. Based on the hydrochemical data of all water samples, principal component analysis is used to obtain the eigenvectors and project the standardized data. The expression is:

[0044]

[0045] Where, It is standardized data The projection of , V1 represents the eigenvector, and the superscripts T and -1 represent the transposed matrix and the inverse matrix respectively;

[0046] S4.1-3. Evaluate the accuracy of data processing and analysis based on the residuals and relative root mean square errors between the predicted and measured values, and select a conservative tracer. The expression is:

[0047]

[0048] Where E represents the residual, r j represents the relative RMS error of solute j, Represents non-normalized data;

[0049] S4.1-4. Calculate the residual distribution between the predicted concentration and the measured concentration in one-dimensional, two-dimensional, and three-dimensional mixed spaces, and its random pattern, i.e., the correlation coefficient R 2 A value close to 0 indicates the suitability of the mixing space and tracer;

[0050] S4.2. Use principal component analysis to reduce the dimensionality of hydrochemical and isotopic data, identify the main variation directions, and determine mixed endmembers based on the geological and hydrological background, such as deep hot water endmember, shallow cold water endmember, atmospheric precipitation endmember, and surface water endmember. The number of potential endmembers, n, satisfies n ≤ m-1, where m is the number of conservative tracers. The specific process is as follows:

[0051] S4.2-1. Perform orthogonal projection on the original data and the eigenvector. The expression is:

[0052]

[0053] Where U is the orthogonal projection data matrix, i.e., the principal component score, is the matrix of normalized values, where i is the i-th sample, p is the number of conservative tracers, and V2 is the eigenvector extracted from the correlation matrix of p conservative tracers;

[0054] The U-space projection is used to calculate the proportion of end-member contributions to groundwater, assuming that the principal component score of a component in the mixed water sample is the linearly weighted sum of the principal component scores of each end-member component;

[0055] S4.2-2. Use the hybrid projection space model in conjunction with hydrochemical analysis to determine the hydrogeological significance of different end members and calculate the mixing ratio, specifically:

[0056] S4.2-21. Determine the endmembers of groundwater in U-space based on the geometrical figure formed by the endmember members. Assume that there are n potential endmembers, representing n-1 principal components:

[0057] PC1=EM1X1+EM2X2+…+EM n X n ;

[0058] PC2=EM1Y1+EM2Y2+…+EM n Y n ;

[0059] …

[0060] PC 1-n =EM1Z1+EM2Z2+…+EM3Z n ;

[0061] EM1+EM2+…+EM n =1;

[0062] Where PC is the principal component score of the water sample, EM is the proportion of end members, Xn, Yn…Zn is the principal component score of the nth end member;

[0063] S4.2-22. Determine the water source based on the principal component scores of different conservative tracers at each end member and their corresponding hydrochemical parameters. That is, when the principal component score of a tracer is positive and greater than 0.5, it indicates that the tracer is positively correlated with the principal component and is the main factor affecting the principal component, indicating that hydrochemical processes related to the tracer are predominant.

[0064] S4.2-23. Combine the conservative tracer concentration and end member composition, and use the mass balance equation to calculate the proportion of cold water, i.e. shallow groundwater or surface water, in the hot spring water. cold , then the hot water end member ratio Y hot =1-Y cold .

[0065] Furthermore, the step S5 is specifically as follows:

[0066] S5.1, according to the calculated cold water mixing ratio Y cold and the measured SiO2 concentration C in the cold water end member cold,SiO2 , calculate the undiluted SiO2 concentration C in the original groundwater before mixing hot,SiO2 , the formula is:

[0067]

[0068] Where, is the measured SiO2 concentration in the hot spring mixed water sample;

[0069] S5.2. According to the applicable SiO2 geothermal temperature scale determined in S3, the corrected SiO2 concentration C obtained in S5.1 is converted to hot,SiO2 Substitute the corresponding temperature scale equation to calculate the final heat storage temperature T final .

[0070] The present invention obtains the geological structure characteristics, lithological characteristics and underground hot water outcrop characteristics in the study area, selects hot spring samples, and tests the representative parameters of all the selected hot spring samples, including total dissolved solids (TDS), main ion concentrations, hydrogen and oxygen stable isotope content δ 2 H and δ 18 O, obtain an analytical error value through data verification, determine a representative water sample based on the analytical error value, then perform hydrochemical analysis on the determined representative water sample, select an appropriate hydrochemical geothermal temperature scale based on the hydrochemical analysis results to calculate the initial thermal reservoir temperature, and then perform end-member mixing analysis on the determined representative water sample based on the hydrochemical analysis results, including data preprocessing and principal component analysis, and calculate the cold and hot water mixing ratio. Finally, based on the cold and hot water mixing ratio, correct the SiO2 concentration and calculate the final thermal reservoir temperature. The present invention determines the geothermal temperature scale through hydrochemical analysis and combines the geothermal temperature scale with the end-member mixing analysis method to calculate the thermal reservoir temperature. This reduces the impact of hot spring water mixing with shallow cold water during its exposure to the surface, comprehensively considers hydrochemical, isotopic and thermal reservoir characteristics, and achieves the determination of the hot spring water mixing ratio and the accurate calculation of the thermal reservoir temperature, providing a basis for classifying the genetic types of geothermal systems and evaluating the potential of geothermal energy resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0072] The present invention will be further described below with reference to the accompanying drawings.

[0073] like Figure 1 As shown, a method for calculating hot spring mixing ratio and heat storage temperature includes the following steps:

[0074] S1. Obtain the geological structure characteristics, lithologic characteristics and underground hot water outcrop characteristics in the study area, and select hot spring samples;

[0075] S2. Test the representative parameters of all selected hot spring samples, including total dissolved solids (TDS), major ion concentrations, and hydrogen and oxygen stable isotope content δ 2 H and δ 18O, obtain the analytical error value through data inspection, and determine the representative water sample based on the analytical error value;

[0076] S3. Performing hydrochemical analysis on the determined representative water sample, and selecting an appropriate hydrochemical geothermal temperature scale to calculate the initial heat storage temperature based on the hydrochemical analysis results;

[0077] S4. Based on the results of the water chemical analysis, perform end-member mixing analysis on the representative water samples identified, including data preprocessing and principal component analysis, and calculate the mixing ratio of hot and cold water;

[0078] S5. According to the mixing ratio of cold and hot water, the SiO2 concentration is corrected and the final heat storage temperature is calculated.

[0079] Example:

[0080] (1) Obtain the geological structure characteristics, lithologic characteristics, and underground hot water outcrop characteristics within the study area, and select hot spring samples:

[0081] 1.1. Set the target number of hot springs and select hot springs with different surrounding rock types in the study area, such as sandstone, limestone, basalt, granite, and gneiss, to ensure that the number of hot springs exposed in each major rock type is balanced;

[0082] 1.2. Collect samples of target hot springs, adjacent artificial geothermal wells, and surrounding rainwater and surface water;

[0083] 1.3. Record the latitude and longitude, altitude, water temperature, Eh value, pH value and free CO2 concentration of each sampling point;

[0084] 1.4. Standard sampling procedures were used. All water samples were filtered using a 0.45 μm filter membrane and stored in pre-cleaned high-density polyethylene bottles to avoid contamination.

[0085] 1.5. A portion of the collected water samples were acidified for subsequent cation analysis, while the other portion was not acidified for indoor testing and analysis of anions, hydrogen and oxygen stable isotopes, TDS, and metasilicic acid.

[0086] (2) The representative parameters of all selected hot spring samples were tested, including total dissolved solids (TDS), major ion concentrations, and hydrogen and oxygen stable isotope content δ 2 H and δ 1 8O, the analytical error value is obtained through data verification, and the representative water sample is determined according to the analytical error value. The main ions of the hot spring sample include K + 、Na + , Ca 2+ Mg 2+ NH4 + OH - 、NO3 -、Cl - 、HCO3 - 、CO3 2- and SO4 2- The process of obtaining the analytical error value and determining the representative water sample is as follows:

[0087] 2.1. Calculate the analytical error value based on the percentage difference. The formula is:

[0088] θ=max(δ1,δ2,δ3);

[0089] Wherein, θ represents the analytical error value, which is used to measure the accuracy of water sample data analysis. The smaller the data, the more reliable the data. δ1 represents the percentage difference of the total number of anion and cation milligram equivalents, which reflects the degree of imbalance relative to the average concentration of anions and cations. δ2 represents the percentage difference of the total number of charges, which reflects the degree of imbalance relative to the average charge of anions and cations. δ3 represents the percentage difference between the calculated TDS value and the measured value, which reflects the degree of imbalance relative to the average TDS value.

[0090] The percentage difference is calculated as follows:

[0091]

[0092] In the formula, δ represents the percentage difference, σ represents the absolute difference, and μ represents the mean;

[0093] 2.2. Based on the TDS and main ion concentrations of each water sample, calculate the total anion and cation milligram equivalents, charge number, and the absolute difference and mean between the measured and calculated TDS values. The formula is:

[0094]

[0095] Where ∑Cations represents the total number of milligram equivalents of the main cations, ∑Anions represents the total number of milligram equivalents of the main anions, and the units of ∑Cations and ∑Anions are meq / L; ∑Z Cations is the cation charge number, ∑Z Anions is the anion charge number, in mol / L;

[0096] 2.3. Eliminate water sample data with analytical error value θ>5% to obtain representative water samples.

[0097] (3) Performing hydrochemical analysis on the determined representative water sample, and selecting an appropriate hydrochemical geothermal temperature scale to calculate the initial heat storage temperature based on the hydrochemical analysis results; the steps for performing hydrochemical analysis on the determined representative water sample are as follows:

[0098] 3.1. Use the multi-rectangle diagram method to classify water chemistry to identify the differences in water chemical components between different water samples. Specifically:

[0099] 3.1-1. Calculate the ions in all representative water samples, including the cation Ca 2+ ,Mg 2+ ,Na + ,K + and anion HCO3 - ,CO3 2- ,SO4 2- ,Cl - The milligram equivalent percentage;

[0100] 3.1-2. Use nine adjacent small rectangles to form a multi-rectangular coordinate system. Divide the horizontal and vertical axes into three adjacent but independent small axes, representing the milligram equivalent percentages of anions and cations respectively. Project the cation percentage onto the horizontal axis and the anion percentage onto the vertical axis. Mark each water sample point in the multi-rectangular coordinate system.

[0101] 3.1-3. Identify the hydrochemical type based on the data distribution in different rectangles, and preliminarily determine the possible mixed sources of groundwater, that is, adjacent data may have the same source;

[0102] 3.2. The equilibrium state of each water sample is determined by the Na-K-Mg triangle diagram, and the hydrochemical geothermal temperature scale is determined in combination with the saturation index. Specifically,

[0103] The water sample data points are plotted on the Na-K-Mg triangle diagram, and the water-rock equilibrium state is determined based on their distribution areas, including the complete equilibrium area, partial equilibrium area, and immature water area;

[0104] For water samples located in the complete equilibrium zone or partial equilibrium zone, the cation geothermal temperature scale is used to estimate the initial heat reservoir temperature;

[0105] For water samples located in immature water areas, geochemical simulation software, such as Phreeqc, is suitable for calculating the saturation index SI of water samples for SiO2 minerals, such as quartz and chalcedony. When the saturation index SI≈0, it indicates that the mineral is close to equilibrium with the water body, and the corresponding SiO2 geothermal temperature scale, such as the quartz temperature scale and the chalcedony temperature scale, is applicable. When the saturation index SI>0 or SI<0, it indicates that the mineral is in an oversaturated or unsaturated state, and the SiO2 geothermal temperature scale is not applicable. The mineral with a saturation index closer to 0 is selected as the geothermal temperature scale.

[0106] S3.3. Calculate the initial thermal reservoir temperature for all representative water samples based on the determined applicable temperature scale.

[0107] The Na-K-Mg triangle diagram is a method used to study the equilibrium state of underground hot water and minerals. The triangle diagram is divided into complete equilibrium, partial equilibrium and immature water areas. The triangle diagram is usually drawn using AquaChem software. The saturation index is an important indicator reflecting the degree of water-rock interaction reaction. It can be used to determine whether the water-rock system has reached an equilibrium state, and then to select a more appropriate SiO2 geothermal temperature scale.

[0108] (4) Based on the results of the water chemical analysis, end-member mixing analysis is performed on the representative water samples identified, including data preprocessing and principal component analysis, and the cold and hot water mixing ratio is calculated; the steps for calculating the cold and hot water mixing ratio are as follows:

[0109] 4.1. Select conservative tracers by standardizing the input data:

[0110] 4.1-1. Standardize and preprocess the input data. The expression is:

[0111]

[0112] Where, X ij and represent the water sample hydrochemical data matrix and its standardized value matrix, respectively, where i is the i-th sample and j is the j-th solute; is the average value of the jth solute, S j is the standard deviation of the jth solute;

[0113] 4.1-2. Based on the hydrochemical data of all water samples, principal component analysis is used to obtain the eigenvectors and the standardized data is projected. The expression is:

[0114]

[0115] Where, It is standardized data The projection of , V1 represents the eigenvector, and the superscripts T and -1 represent the transposed matrix and the inverse matrix respectively;

[0116] 4.1-3. Evaluate the accuracy of data processing and analysis based on the residuals and relative root mean square errors between the predicted and measured values, and select a conservative tracer. The expression is:

[0117]

[0118] Where E represents the residual, r j represents the relative RMS error of solute j, Represents non-normalized data;

[0119] 4.1-4. Calculate the residual distribution between the predicted concentration and the measured concentration in one-dimensional, two-dimensional, and three-dimensional mixed spaces, and its random pattern, i.e., the correlation coefficient R 2 A value close to 0 indicates the applicability of the mixing space and the tracer; this example calculates R according to the Origin software 2 <0.3, select conservative tracer;

[0120] 4.2. Principal component analysis was used to reduce the dimensionality of the hydrochemical and isotopic data, identify the main variation directions, and determine the mixed endmembers, such as deep hot water endmember, shallow cold water endmember, atmospheric precipitation endmember, and surface water endmember, based on the geological and hydrological background. The number of potential endmembers, n, satisfies n≤m-1, where m is the number of conservative tracers. The specific process is as follows:

[0121] 4.2-1. Perform orthogonal projection on the original data and the eigenvector. The expression is:

[0122]

[0123] Where U is the orthogonal projection data matrix, i.e., the principal component score, is the matrix of normalized values, where i is the i-th sample, p is the number of conservative tracers, and V2 is the eigenvector extracted from the correlation matrix of p conservative tracers;

[0124] The U-space projection is used to calculate the proportion of end-member contributions to groundwater, assuming that the principal component score of a component in the mixed water sample is the linearly weighted sum of the principal component scores of each end-member component;

[0125] 4.2-2. Use the hybrid projection space model combined with hydrochemical analysis to determine the hydrogeological significance of different end members and calculate the mixing ratio, specifically:

[0126] 4.2-21. Determine the endmembers of groundwater in U-space based on the geometrical figure formed by the endmember members. Assuming there are n potential endmembers, representing n-1 principal components:

[0127] PC1=EM1X1+EM2X2+…+EM n X n ;

[0128] PC2=EM1Y1+EM2Y2+…+EM n Y n ;

[0129] …

[0130] PC 1-n =EM1Z1+EM2Z2+…+EM3Z n ;

[0131] EM1+EM2+…+EM n = 1;

[0132] In the formula, PC is the principal component score of the water sample, EM is the proportion of the end member, Xn, Yn…Zn is the principal component score of the nth end member;

[0133] 4.2-22, according to the principal component score of each end member of different conservative tracers and its corresponding hydrochemical parameters, the water source is determined, that is, when the tracer principal component score is positive and greater than 0.5, it indicates that the tracer is positively correlated with the principal component and is the main factor affecting the principal component, indicating that the water chemical process related to the tracer mainly occurs; for example, PC1 and Ca 2+ , Mg 2+ , SO4 2- are positively correlated and the scores are greater than 0.5, indicating that gypsum dissolution is the main hydrogeochemical process, and end members with high PC1 scores represent bedrock groundwater dominated by gypsum dissolution;

[0134] 4.2-23, combined with the concentration of conservative tracers and end member components, the mass balance equation is used to calculate the proportion Y of cold water, i.e. shallow groundwater or surface water end member in hot spring water cold , then the proportion Y of hot water end member is hot = 1-Y cold .

[0135] (5) According to the mixing ratio of cold and hot water, the SiO2 concentration is corrected, and the final geothermal reservoir temperature T is calculated:

[0136] 5.1, according to the calculated cold water mixing ratio Y cold and the measured SiO2 concentration C cold,SiO2 in the cold water end member, the SiO2 concentration C hot,SiO2 in the original underground hot water before dilution is calculated, and the formula is:

[0137]

[0138] In the formula, is the measured SiO2 concentration in the hot spring mixed water sample;

[0139] 5.2, according to the applicable SiO2 geothermal temperature scale determined in S3, the corrected SiO2 concentration C hot,SiO2 obtained in 5.1 is substituted into the corresponding temperature scale equation to calculate the final geothermal reservoir temperature T final .

[0140] This embodiment is applicable to a quartz temperature scale without steam loss (0-250℃), and the final geothermal reservoir temperature T final is obtained:

[0141]

Claims

1. A method for calculating hot spring mixing ratio and heat storage temperature, characterized in that: The steps include: S1. Obtain the geological structure characteristics, lithologic characteristics and underground hot water outcrop characteristics in the study area, and select hot spring samples; S2. Test the representative parameters of all selected hot spring samples, including total dissolved solids (TDS), major ion concentrations, and hydrogen and oxygen stable isotope contents. Analytical error values ​​are obtained through data verification, and representative water samples are determined based on the analytical error values. S3. Performing hydrochemical analysis on the determined representative water sample, and selecting an appropriate hydrochemical geothermal temperature scale to calculate the initial heat storage temperature based on the hydrochemical analysis results; S4. Based on the results of the water chemical analysis, perform end-member mixing analysis on the representative water samples identified, including data preprocessing and principal component analysis, and calculate the mixing ratio of hot and cold water; S5. According to the mixing ratio of cold and hot water, the SiO2 concentration is corrected and the final heat storage temperature is calculated.

2. The method for calculating hot spring mixing ratio and heat storage temperature according to claim 1, characterized in that: The method for selecting hot spring samples in S1 is specifically as follows: S1.

1. Set the target number of hot springs and select hot springs with different surrounding rock lithologies in the study area to ensure that the number of hot springs exposed for each major rock type is balanced; S1.

2. Collect samples of target hot springs, adjacent artificial geothermal wells, and surrounding rainwater and surface water; S1.

3. Record the latitude and longitude, altitude, water temperature, Eh value, pH value, and free CO2 concentration of each sampling point; S1.

4. Standard sampling procedures were used. All water samples were filtered through membrane filters and stored in pre-cleaned high-density polyethylene bottles to avoid contamination. S1.

5. A portion of the collected water samples is acidified for subsequent cation analysis, while the other portion is not acidified for indoor testing and analysis of anions, hydrogen and oxygen stable isotopes, TDS, and metasilicic acid.

3. The method for calculating hot spring mixing ratio and heat storage temperature according to claim 1, characterized in that: The main ions in S2 include K + 、Na + , Ca 2+ Mg 2+ NH4 + OH - 、NO3 - 、Cl - 、HCO3 - 、CO3 2- and SO4 2- The process of obtaining the analytical error value and determining the representative water sample is as follows: S2.

1. Calculate the analytical error value based on the percentage difference. The formula is: θ=max(δ1,δ2,δ3); Wherein, θ represents the analytical error value, which is used to measure the accuracy of water sample data analysis. The smaller the data, the more reliable the data. δ1 represents the percentage difference of the total number of anion and cation milligram equivalents, which reflects the degree of imbalance relative to the average concentration of anions and cations. δ2 represents the percentage difference of the total number of charges, which reflects the degree of imbalance relative to the average charge of anions and cations. δ3 represents the percentage difference between the calculated TDS value and the measured value, which reflects the degree of imbalance relative to the average TDS value. The percentage difference is calculated as follows: In the formula, δ represents the percentage difference, σ represents the absolute difference, and μ represents the mean; S2.

2. Calculate the total milligram equivalents of anions and cations, the charge number, and the absolute difference and mean between the measured and calculated TDS values ​​for each water sample based on the TDS and major ion concentrations. The formula is: Where ∑Cations represents the total number of milligram equivalents of the main cations, ∑Anions represents the total number of milligram equivalents of the main anions, and the units of ∑Cations and ∑Anions are meq / L; ∑Z Cations is the cation charge number, ∑Z Anions is the anion charge number, in mol / L; S2.

3. Eliminate water sample data with analytical error values ​​θ>5% to obtain representative water samples.

4. The method for calculating hot spring mixing ratio and heat storage temperature according to claim 1, characterized in that: The steps of performing water chemical analysis on the determined representative water sample in S3 are: S3.

1. Use the multi-rectangle diagram method to classify water chemistry to identify differences in water chemical composition between different water samples. Specifically: S3.1-1. Calculate the milligram equivalent percentage of each ion in all representative water samples; S3.1-2. Use nine adjacent small rectangles to form a multi-rectangular coordinate system. Divide the horizontal and vertical axes into three adjacent but independent small axes, each representing the milligram equivalent percentages of anions and cations. Project the cation percentage onto the horizontal axis and the anion percentage onto the vertical axis. Label each water sample point in the multi-rectangular coordinate system. S3.1-3. Identify the hydrochemical type based on the data distribution in different rectangles, and preliminarily determine the possible mixed sources of groundwater, that is, adjacent data may have the same source; S3.

2. Determine the equilibrium state of each water sample using the Na-K-Mg triangle diagram and determine the hydrochemical geothermal temperature scale based on the saturation index. Specifically, The water sample data points are plotted on the Na-K-Mg triangle diagram, and the water-rock equilibrium state is determined based on their distribution areas, including the complete equilibrium area, partial equilibrium area, and immature water area; For water samples located in the complete equilibrium zone or partial equilibrium zone, the cation geothermal temperature scale is used to estimate the initial heat reservoir temperature; For water samples located in immature water areas, geochemical simulation software is used to calculate the saturation index SI of the water sample for SiO2 minerals. When the saturation index SI≈0, it indicates that the mineral is close to equilibrium with the water body, and the corresponding SiO2 geothermal temperature scale is applicable. When the saturation index SI>0 or SI<0, it indicates that the mineral is in an oversaturated or unsaturated state, and the SiO2 geothermal temperature scale is not applicable. The mineral with a saturation index closer to 0 is selected as the geothermal temperature scale. S3.

3. Calculate the initial thermal reservoir temperature for all representative water samples based on the determined applicable temperature scale.

5. The method for calculating hot spring mixing ratio and heat storage temperature according to claim 1, characterized in that: The step of calculating the mixing ratio of hot and cold water in S4 is: S4.

1. Select conservative tracers by standardizing the input data: S4.1-1. Standardize and preprocess the input data. The expression is: Where, X ij and represent the water sample hydrochemical data matrix and its standardized value matrix, respectively, where i is the i-th sample and j is the j-th solute; is the average value of the jth solute, S j is the standard deviation of the jth solute; S4.1-2. Based on the hydrochemical data of all water samples, principal component analysis is used to obtain the eigenvectors and project the standardized data. The expression is: Where, It is standardized data The projection of , V1 represents the eigenvector, and the superscripts T and -1 represent the transposed matrix and the inverse matrix respectively; S4.1-3. Evaluate the accuracy of data processing and analysis based on the residuals and relative root mean square errors between the predicted and measured values, and select a conservative tracer. The expression is: Where E represents the residual, r j represents the relative RMS error of solute j, Represents non-normalized data; S4.1-4. Calculate the residual distribution between the predicted concentration and the measured concentration in one-dimensional, two-dimensional, and three-dimensional mixed spaces, and its random pattern, i.e., the correlation coefficient R 2 A value close to 0 indicates the applicability of the mixing space and tracer. S4.

2. Use principal component analysis to reduce the dimensionality of the hydrochemical and isotopic data, identify the main variation directions, and determine the mixing end members based on the geological and hydrological background. The number of potential end members, n, satisfies n≤m-1, where m is the number of conservative tracers. The specific process is as follows: S4.2-1. Perform orthogonal projection on the original data and the eigenvector. The expression is: Where U is the orthogonal projection data matrix, i.e., the principal component score, is the matrix of normalized values, where i is the i-th sample, p is the number of conservative tracers, and V2 is the eigenvector extracted from the correlation matrix of p conservative tracers; S4.2-2. Use the hybrid projection space model in conjunction with hydrochemical analysis to determine the hydrogeological significance of different end members and calculate the mixing ratio, specifically: S4.2-21. Determine the endmembers of groundwater in U-space based on the geometrical figure formed by the endmember members. Assume that there are n potential endmembers, representing n-1 principal components: PC1=EM1X1+EM2X2+…+EM n X n ; PC2=EM1Y1+EM2Y2+…+EM n Y n ; … PC 1-n =EM1Z1+EM2Z2+…+EM3Z n ; EM1+EM2+…+EM n =1; Where PC is the principal component score of the water sample, EM is the proportion of end members, Xn, Yn…Zn is the principal component score of the nth end member; S4.2-22. Determine the water source based on the principal component scores of different conservative tracers at each end member and their corresponding hydrochemical parameters. That is, when the principal component score of a tracer is positive and greater than 0.5, it indicates that the tracer is positively correlated with the principal component and is the main factor affecting the principal component, indicating that hydrochemical processes related to the tracer are predominant. S4.2-23. Combine the conservative tracer concentration and end member composition, and use the mass balance equation to calculate the proportion of cold water, i.e. shallow groundwater or surface water, in the hot spring water. cold , then the hot water end member ratio Y hot =1-Y cold .

6. The method for calculating hot spring mixing ratio and heat storage temperature according to claim 1, characterized in that: The steps of S5 are specifically as follows: S5.1, according to the calculated cold water mixing ratio Y cold and the measured SiO2 concentration C in the cold water end member cold,SiO2 , calculate the undiluted SiO2 concentration C in the original groundwater before mixing hot,SiO2 , the formula is: Where, is the measured SiO2 concentration in the hot spring mixed water sample; S5.

2. According to the applicable SiO2 geothermal temperature scale determined in S3, the corrected SiO2 concentration C obtained in S5.1 is converted to hot,SiO2 Substitute the corresponding temperature scale equation to calculate the final heat storage temperature T final .

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