A method for delineating a fracture-type, zonal thermal reservoir extension concealed geothermal target area

Abstract

The application discloses a fissure type strip-shaped thermal reservoir extension area hidden geothermal target area delineation method, which comprises the following steps: collecting 1:50000 and 1:500000 regional geological survey and previous geothermal exploration data, calculating the temperature increasing rate of three dimensions of whole borehole, 50m and adjacent temperature measuring points respectively according to the borehole temperature measuring data of each geothermal field, finding the geothermal temperature increasing gradient change section, and determining the hot water occurrence section; drawing the temperature field profile value line graph and the temperature plane value line graph of the same depth of the same type of borehole, determining the maximum curvature position of the temperature value line and the extension direction at different depths, and comprehensively identifying the heat control structure in combination with the analysis of the geothermal geological plane distribution characteristics. The application is based on the principles of hydrogeochemistry and hydrogeology, and the hydraulic connection between different geothermal fields on the fracture zone is judged, the lateral runoff circulation type geothermal system is identified, the spatial distribution of the supplement, drainage and discharge is determined, and the favorable geothermal exploration target area is selected through the means of collecting previous geothermal exploration data and supplementing water chemical characteristics and the like.

Description

Technical Field

[0001] This invention relates to the field of exploration technology for fractured geothermal resources, and in particular to a method for delineating concealed geothermal target areas in fractured zone-shaped geothermal reservoir extension areas. Background Technology

[0002] Geothermal water is an important renewable resource, widely used in heating, hot spring therapy, and other applications, and has high development value. my country's southeastern coastal region is rich in geothermal resources, largely controlled by regional deep and large faults. The geothermal water is found in bands within the fissures along the fault extension direction, but its distribution is extremely uneven.

[0003] Currently, the main method for exploring fractured geothermal resources is to locate the geothermal anomalies by conducting geological surveys, geophysical exploration, and shallow-hole thermography in or around the geothermal outcrop area to identify geothermal anomalies and delineate the target exploration area. This method suffers from problems such as high exploration costs and limited geothermal exploration range.

[0004] To address these issues, we propose a method for delineating concealed geothermal target areas within fractured, banded geothermal reservoir extension zones. Summary of the Invention

[0005] The purpose of this invention is to provide a method for delineating concealed geothermal target areas in fractured zone-shaped geothermal reservoir extension areas, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for delineating concealed geothermal target areas in a fractured, banded geothermal reservoir extension zone includes the following steps:

[0008] S1. Collect 1:50,000 and 1:500,000 regional geological survey data and previous geothermal exploration data to determine the distribution of deep faults, secondary faults, and geothermal fields in the study area. Calculate the temperature increase rate of the entire borehole, 50m depth, and adjacent temperature measurement points for each geothermal field to identify geothermal temperature gradient change segments and determine hot water storage segments. Draw temperature field profile maps and temperature plane maps at the same depth for similar boreholes to determine the location of the maximum curvature of the temperature lines and the direction of extension at different depths. Combined with the analysis of geothermal geological plane distribution characteristics, comprehensively identify heat-controlling structures.

[0009] S2. Water chemical samples were collected along the entire thermal control fault zone. The sampling points included geothermal water, rainwater, shallow groundwater, and river water. During the sampling process, a portable ion meter was used to measure pH, water temperature, conductivity, and redox potential data.

[0010] S3. Verification and removal of abnormal indoor data, including:

[0011] S31. Perform ion balance test, TDS test, and SiO2 content test;

[0012] S32. For each abnormal data found after inspection, check and analyze the cause of the abnormality, describe it separately in the cause analysis, and remove the rest of the data.

[0013] S4, transfer the K of hot water from various locations + Na + Mg 2+ The ion mass concentration test results are calculated using the following formula: X Mg Y Na Z K The K-Na-Mg triangular diagram was drawn and compared with the "lower equilibrium limit curve" and "complete equilibrium curve" to determine the hot water equilibrium status in various places. The applicability of temperature scale formulas such as cation temperature scale, quartz temperature scale, and chalcedony temperature scale was analyzed. Reliable temperature scales were selected to calculate the temperature of the geothermal reservoir after mixing. The original geothermal reservoir temperature was calculated using the multi-mineral equilibrium temperature scale and the silicon-enthalpy temperature scale. The distribution characteristics of geothermal reservoir temperature and static water level elevation in the longitudinal direction of the fault zone were combined to identify the lateral runoff circulation type geothermal system and analyze the migration path of hot water in various places.

[0014]

[0015]

[0016]

[0017] S5. Based on the test results, draw the variation law of macro-elements in the transverse and longitudinal directions of the thermal control fracture. Use Piper tri-line diagram to divide the different water bodies into zones, determine the water supply source and terminal water body, and then combine the simplified hydrological information of the geothermal drilling process, the thermal reservoir sealing conditions, the hydrogeological parameters of the pumping test, and the dynamic change characteristics to determine the stage of the hydrogeological cycle process in each zone.

[0018] S6. Screen the hydrochemical calibration components in geothermal water that are positively correlated with the original reservoir temperature and are very different from shallow groundwater. Conduct correlation analysis between the calibration components and different solutes, select solutes with correlation coefficients r≥0.8, summarize the spatial distribution characteristics of minerals, and deduce the source and formation path of minerals by comparing the longitudinal and transverse lithological distribution and ore body characteristics within the fault zone.

[0019] S7. Based on the geochemical temperature scale-calculated reservoir temperature distribution characteristics, the zoning relationships determined by the Piper tri-line map, and the mineral formation processes inferred from solute correlation analysis, comprehensively analyze the recharge, runoff, mixing, and discharge paths between geothermal fields in the distribution area of ​​heat-controlling faults. In the geothermal runoff-discharge section of the heat-controlling fault extension area, select low-lying, elongated valley areas based on satellite imagery. Deploy two left and right geophysical exploration lines in the vertical direction of the heat-controlling fault and the parallel direction of the hanging wall, respectively. Detect the presence of high-angle secondary faults that intersect the heat-controlling fault, and delineate areas where the target depth of the heat-controlling fault exhibits low resistivity as geothermal exploration target areas. Among these, the preferred geophysical methods are combined profiling and controlled-source audio-frequency magnetotelluric sounding, with the point spacing controlled within 20m.

[0020] Furthermore, in step S2, the analysis of the water chemistry sample includes macroelements, total dissolved solids, pH, and special components;

[0021] The macro element is mainly K. + Na + Ca 2+ Mg 2+ Cl - SO4 2- HCO3 - CO3 2- ;

[0022] The special component includes Fe. 2+ Fe 3+ F - NO3 - , SiO2, Ba, Sr, Li, Zn.

[0023] Furthermore, in step S2, the sampling points include:

[0024] ① All geothermal water with a temperature greater than 25℃, groundwater that penetrates different aquifers, different types of river and stream water, and rainwater along the heat-controlling fracture line;

[0025] ② Groundwater, river streams, and rainwater at different altitudes along the vertical heat-controlling fracture;

[0026] Except for geothermal water, other sampling points should be distributed as evenly as possible, with a total number of more than 20 groups.

[0027] Furthermore, in step S3,

[0028] The ion balance test specifically involves: based on K... + Na + Ca 2+ Mg 2+ Four cations and Cl - SO4 2-HCO3 - CO3 2- NO3 - F - The mass concentration test results of the six anions were used to calculate the millimoles of cations and... anion millimoles and The ion balance is assessed according to the following formula. If it does not meet the requirements, the laboratory is arranged to retest. If it still does not meet the requirements, the data of this group is treated as abnormal data.

[0029] when hour,

[0030] when hour, ;

[0031] The TDS test specifically involves evaluating the total dissolved solids (TDS) measured in the laboratory using the groundwater conductivity value (K) determined on-site, according to the following formula. If the TDS does not meet the requirements, the laboratory will retest. If it still does not meet the requirements, the data set will be treated as abnormal data.

[0032] ;

[0033] The SiO2 content test specifically involves: using a portable waterproof photometer to test the silica mass concentration in groundwater on-site, and evaluating the silica mass concentration measured in the laboratory according to the following formula. If the concentration does not meet the requirements, abnormal data is processed:

[0034] .

[0035] Furthermore, in step S5, rainwater, river water, and shallow groundwater with TDS less than 100 mg / L and oxidation potential of -100 to +200 mV are used as recharge water sources. Geothermal water with large geothermal reservoirs, stable impermeable layers above, significant abrupt changes in water level and temperature when the geothermal reservoirs are exposed, TDS greater than 500 mg / L, pumping unit inflow less than 1 L / (s·m), minimal impact on surface water and shallow groundwater, and small dynamic changes in water level over a hydrological year are used as terminal water bodies.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] Based on the principles of hydrogeochemistry and hydrogeology, this method uses methods such as collecting previous geothermal exploration data and supplementing tests on hydrochemical characteristics to determine the hydraulic connections between different geothermal fields along the fault zone, identify lateral runoff circulation geothermal systems, determine the spatial distribution of runoff and discharge, and select favorable geothermal exploration target areas. It features low workload and comprehensive target area delineation, and is widely applicable to geothermal exploration in blind areas such as scenic spots or cities with urgent geothermal needs in fracture-type zonal geothermal reservoir extension areas. Attached Figure Description

[0038] Figure 1 This is the overall flowchart of the present invention;

[0039] Figure 2 This is a schematic diagram of the cyclic process judgment in this invention;

[0040] Figure 3 This is a diagram showing the variation of (Na+K)-(HCO3+CO3) during the dry season in a geothermal field. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Please see Figure 1-2 A method for delineating concealed geothermal target areas in fractured, strip-shaped geothermal reservoir extension zones is proposed. Based on the principles of hydrogeochemistry and hydrogeology, this method utilizes previous geothermal exploration data and supplementary hydrochemical characteristic testing to determine the hydraulic connections between different geothermal fields along the fault zone, identify lateral runoff circulation geothermal systems, determine the spatial distribution of runoff and discharge, and select favorable geothermal exploration target areas. This method features low workload and comprehensive target area delineation, and is widely applicable to geothermal exploration in blind spots in scenic areas or cities with urgent geothermal needs within fractured, strip-shaped geothermal reservoir extension zones. Details are as follows:

[0043] The first step involved collecting data from 1:50,000 and 1:500,000 regional geological surveys and previous geothermal explorations to determine the distribution of deep faults, secondary faults, and geothermal fields in the study area. For borehole temperature measurement data from various geothermal fields, the warming rate was calculated across three dimensions: the entire borehole, 50m depth, and adjacent measurement points, to identify geothermal warming gradient zones and determine hot water storage areas. Contour maps of temperature field profiles from similar boreholes and contour maps of temperature planes at the same depth were drawn to determine the location of maximum curvature of temperature contour lines and their extension direction at different depths. Combined with the analysis of geothermal geological plane distribution characteristics, the heat-controlling structures were comprehensively identified.

[0044] The second step involved collecting water chemical samples along the entire thermally controlled fault zone. Sampling points included geothermal water, rainwater, shallow groundwater (including well water), and river water. During sampling, a portable ion meter was used to measure data such as pH, water temperature, conductivity, and redox potential. Indoor water chemical analysis included macroelements (primarily potassium). + Na + Ca 2+ Mg 2+ Cl - SO4 2- HCO3 - CO3 2- (eight types), total dissolved solids, pH, special components (especially Fe) 2+ Fe 3+ F - NO3 - The sampling points should include: ① all geothermal water with a temperature greater than 25℃ along the heat-controlling fracture line, groundwater penetrating different aquifers, different types of river and stream water, and rainwater; ② groundwater, river and stream water, and rainwater at different altitudes perpendicular to the heat-controlling fracture. Except for geothermal water, other sampling points should be distributed as evenly as possible, with a total number of no less than 20 groups.

[0045] The third step is to review and remove abnormal indoor data.

[0046] ① Perform ion balance test: based on K + Na + Ca 2+ Mg 2+ Four cations and Cl - SO4 2- HCO3 - CO3 2- NO3 - F - Calculate the millimoles of cations and cations based on the mass concentration test results of the six anions (unit: mg / L). anion millimoles and The ion balance was then assessed using the following formula. If the results did not meet the requirements, the laboratory was instructed to retest. If the results still did not meet the requirements, the data set was treated as abnormal data.

[0047] when hour,

[0048]

[0049] when

[0050]

[0051] ② Conduct TDS testing: Evaluate the TDS (total dissolved solids) measured in the laboratory using the groundwater conductivity value K (μS / cm) measured on-site, according to the following formula. If it does not meet the requirements, arrange for the laboratory to retest. If it still does not meet the requirements, the data set should be treated as abnormal data.

[0052]

[0053] ③ Conduct SiO2 content testing: On-site testing was performed using a portable waterproof silica photometer to measure the mass concentration of silica in the groundwater (result: SiO2 content). 2x (unit: mg / L), and the mass concentration of silica determined in the laboratory is expressed by the following formula (result: SiO2). 2s The data (unit: mg / L) will be evaluated, and if it does not meet the requirements, it will be treated as abnormal data.

[0054]

[0055] ④ For each abnormal data found after inspection, check and analyze the cause of the abnormality. If it is caused by local geological or hydrogeological abnormalities at the location of the sampling well, it will be described separately in the cause analysis, and the rest of the data will be removed.

[0056] The fourth step is to measure the K of hot water from different locations. + Na + Mg 2+ The ion mass concentration (unit: mg / L) test results are calculated using the following formula: X Mg Y Na Z K A K-Na-Mg triangular diagram was drawn. By comparing the results with the "lower equilibrium limit curve" and "complete equilibrium curve," the equilibrium state of hot water in various locations was determined. The applicability of temperature scale formulas such as the cation temperature scale, quartz temperature scale, and chalcedony temperature scale was analyzed, and reliable temperature scales were selected to calculate the temperature of the geothermal reservoir after mixing. The original geothermal reservoir temperature was calculated using the multi-mineral equilibrium temperature scale and the silicon-enthalpy temperature scale. By combining the distribution characteristics of geothermal reservoir temperature and static water level elevation along the longitudinal direction of the fault zone, lateral runoff circulation geothermal systems were identified, and the migration paths of hot water in various locations were analyzed.

[0057]

[0058]

[0059]

[0060] The fifth step involves drawing a map showing the variation patterns of macro-elements in the transverse and longitudinal directions of the thermal control fracture based on the test results. Combining this with the temperatures of various water sources, a Piper trilinear diagram is used to zone different water bodies, determining the recharge water source and the terminal water body. The hydrogeological cycle process of each zone is determined by comprehensively considering simplified hydrological information from the geothermal drilling process, reservoir sealing conditions, hydrogeological parameters from pumping tests, and dynamic change characteristics. Generally, rainwater, river water, and shallow groundwater with a TDS of less than 100 mg / L and an oxidation potential of -100 to +200 mV are used as recharge water sources. Geothermal water with large reservoirs, a stable impermeable layer above, significant abrupt changes in water level and temperature upon reservoir exposure, a TDS greater than 500 mg / L, a pumping unit inflow of less than 1 L / (s·m), minimal impact on surface water and shallow groundwater, and small dynamic changes in water level over a hydrological year are used as the terminal water body.

[0061] The sixth step involves screening hydrochemical calibration components in geothermal water that are positively correlated with the original reservoir temperature and significantly different from those in shallow groundwater. Correlation analysis is conducted between the calibration components and different solutes, selecting solutes with a correlation coefficient r ≥ 0.8. The spatial distribution characteristics of minerals are summarized, and the origin and formation pathways of minerals are deduced by comparing the longitudinal and lateral lithological distribution and ore body characteristics within the fault zone.

[0062] Step 7: Based on the geochemical temperature scale-calculated reservoir temperature distribution characteristics, the zoning relationships determined by the Piper tri-line map, and the mineral formation processes inferred from solute correlation analysis, a comprehensive analysis of the recharge, runoff, mixing, and discharge paths between geothermal fields in the heat-controlling fault distribution area is conducted. In the geothermal runoff-discharge section of the heat-controlling fault extension area, low-lying, elongated valley areas are selected based on satellite imagery. Two geophysical exploration lines are deployed vertically to the heat-controlling fault and parallel to the hanging wall, respectively. Areas with high-angle secondary faults intersecting the heat-controlling fault and exhibiting low resistivity at the target depth of the heat-controlling fault are designated as geothermal exploration target areas. Among these, the preferred geophysical methods are combined profiling and controlled-source audio-frequency magnetotelluric sounding, with point spacing controlled within 20m.

[0063] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0064] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for delineating concealed geothermal target areas in a fractured, banded geothermal reservoir extension zone, characterized in that: Includes the following steps: S1. Collect and analyze geological survey data and historical geothermal exploration data of the target area, calculate the temperature increase rate of borehole temperature measurement data in different dimensions, identify the geothermal temperature gradient change segment to determine the hot water occurrence segment, draw temperature field profile and plane contour map, determine the location of the maximum curvature of temperature contour lines and the direction of extension, and combine the geothermal geological plane distribution characteristics for comprehensive analysis to identify heat-controlling structures. S2. Water chemical samples were collected along the entire thermal control fault zone. The sampling points included geothermal water, rainwater, shallow groundwater, and river water. During the sampling process, a portable ion meter was used to measure pH, water temperature, conductivity, and redox potential data. S3. Verification and removal of abnormal indoor data, including: S31. Perform ion balance test, TDS test, and SiO2 content test; S32. For each abnormal data found after inspection, check and analyze the cause of the abnormality, describe it separately in the cause analysis, and remove the rest of the data. S4, transfer the K of hot water from various locations + Na + Mg 2+ The ion mass concentration test results are calculated using the following formula: X Mg Y Na Z K The K-Na-Mg triangular diagram was drawn and compared with the "lower equilibrium limit curve" and "complete equilibrium curve" to determine the hot water equilibrium status in various places. The applicability of temperature scale formulas such as cation temperature scale, quartz temperature scale, and chalcedony temperature scale was analyzed. Reliable temperature scales were selected to calculate the temperature of the geothermal reservoir after mixing. The original geothermal reservoir temperature was calculated using the multi-mineral equilibrium temperature scale and the silicon-enthalpy temperature scale. The distribution characteristics of geothermal reservoir temperature and static water level elevation in the longitudinal direction of the fault zone were combined to identify the lateral runoff circulation type geothermal system and analyze the migration path of hot water in various places. S5. Based on the test results, draw the variation law of macro-elements in the transverse and longitudinal directions of the thermal control fracture. Use Piper tri-line diagram to divide the different water bodies into zones, determine the water supply source and terminal water body, and then combine the simplified hydrological information of the geothermal drilling process, the thermal reservoir sealing conditions, the hydrogeological parameters of the pumping test, and the dynamic change characteristics to determine the stage of the hydrogeological cycle process in each zone. S6. Screen the hydrochemical calibration components in geothermal water that are positively correlated with the original reservoir temperature and are very different from shallow groundwater. Conduct correlation analysis between the calibration components and different solutes, select solutes with correlation coefficients r≥0.8, summarize the spatial distribution characteristics of minerals, and deduce the source and formation path of minerals by comparing the longitudinal and transverse lithological distribution and ore body characteristics within the fault zone. S7. Based on the geochemical temperature scale-calculated reservoir temperature distribution characteristics, the zoning relationships determined by the Piper tri-line map, and the mineral formation processes inferred from the correlation analysis between solutes, comprehensively analyze the recharge, runoff, mixing, and discharge paths between geothermal fields in the distribution area of ​​the heat-controlling fault. In the geothermal runoff-discharge section of the heat-controlling fault extension area, select low-lying, elongated valley areas based on satellite imagery. Deploy two left and right geophysical exploration lines in the vertical direction of the heat-controlling fault and the parallel direction of the hanging wall, respectively. Detect the presence of high-angle secondary faults that intersect the heat-controlling fault, and delineate areas where the target depth of the heat-controlling fault shows low resistivity as geothermal exploration target areas. Among these, the geophysical exploration methods should preferentially select the combined profile and controlled-source audio-frequency magnetotelluric sounding methods, and the point spacing should be controlled within 20m.

2. The method for delineating concealed geothermal target areas in fracture-type strip-shaped geothermal reservoir extension areas according to claim 1, characterized in that: In step S2, the analysis of the water chemistry sample includes macroelements, total dissolved solids, pH, and special components. The macro element is mainly K. + Na + Ca 2+ Mg 2+ Cl - SO4 2- HCO3 - CO3 2- ; The special component includes Fe. 2+ Fe 3+ F - NO3 - , SiO2, Ba, Sr, Li, Zn.

3. The method for delineating concealed geothermal target areas in fracture-type strip-shaped geothermal reservoir extension zones according to claim 1, characterized in that: In step S2, the sampling points include: ① All geothermal water with a temperature greater than 25℃, groundwater that penetrates different aquifers, different types of river and stream water, and rainwater along the heat-controlling fracture line; ② Groundwater, river streams, and rainwater at different altitudes along the vertical heat-controlling fracture; Except for geothermal water, other sampling points should be distributed as evenly as possible, with a total number of more than 20 groups.

4. The method for delineating concealed geothermal target areas in fracture-type strip-shaped geothermal reservoir extension zones according to claim 1, characterized in that: In step S3 The ion balance test specifically involves: based on K... + Na + Ca 2+ Mg 2+ Four cations and Cl - SO4 2- HCO3 - CO3 2- NO3 - F - The mass concentration test results of the six anions were used to calculate the millimoles of cations and... anion millimoles and The ion balance is assessed according to the following formula. If it does not meet the requirements, the laboratory is arranged to retest. If it still does not meet the requirements, the data of this group is treated as abnormal data. when hour, when hour, ; The TDS test specifically involves evaluating the total dissolved solids (TDS) measured in the laboratory using the groundwater conductivity value (K) determined on-site, according to the following formula. If the TDS does not meet the requirements, the laboratory will retest. If it still does not meet the requirements, the data set will be treated as abnormal data. ； The SiO2 content test specifically involves: using a portable waterproof photometer to test the silica mass concentration in groundwater on-site, and evaluating the silica mass concentration measured in the laboratory according to the following formula. If the concentration does not meet the requirements, abnormal data is processed: 。 5. The method for delineating concealed geothermal target areas in fracture-type strip-shaped geothermal reservoir extension areas according to claim 1, characterized in that: In step S5, the terminal water body must meet the following conditions: deep geothermal reservoir burial, stable water-proof layer above, significant sudden change in water level and temperature when exposed, total dissolved solids > 500 mg / L, unit inflow < 1 L / (s·m), small impact on shallow water and small annual dynamic change. The water supply sources include rainwater, river water, and shallow groundwater with total dissolved solids <100mg / L and oxidation-reduction potential between -100 and +200mV.

6. The method for delineating concealed geothermal target areas in fracture-type strip-shaped geothermal reservoir extension areas according to claim 1, characterized in that: In step S1, the temperature increase rate includes the temperature increase rate of the entire hole, the temperature increase rate of the 50-meter section, and the temperature increase rate of adjacent temperature measurement points.

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