Three-dimensional geothermal collecting and mining system based on hydrothermal type mine and well position arrangement method of three-dimensional geothermal collecting and mining system

Abstract

According to the system, one end of a fixed extraction well is arranged on the ground, and the other end of the fixed extraction well extends to a geothermal reservoir; one end of the movable extraction well is arranged in a roadway of a stope face, and the other end extends to a geothermal reservoir; one end of the movable recharge well is arranged in a roadway of a stope face, and the other end extends to a geothermal reservoir; one end of the fixed extraction well and one end of the movable extraction well are connected to the heat exchange station through extraction pipelines, and the heat exchange station is connected to one end of the movable recharge well through a recharge pipeline; high-temperature water in the geothermal reservoir at the position of the stope face is conveyed to the heat exchange station through the extraction pipeline by the fixed extraction well and the movable extraction well, and low-temperature water in the heat exchange station is conveyed to the geothermal reservoir through the recharge pipeline and the movable recharge well. By adopting the distributed mining and irrigation arrangement, the occupied area needed by well site ground construction is reduced, and the utilization rate of underground geothermal resources is increased while the ground occupied area is effectively saved.

Description

Technical Field

[0001] The present invention relates to a mine geothermal centralized mining technology, and in particular to a hydrothermal mine three-dimensional geothermal centralized mining system and a well location arrangement method thereof. Background Art

[0002] With the increasing mining depth of mines, most mines have coal-associated geothermal resources. Therefore, as a new target and key area for geothermal resource research, mines are an important way to achieve multi-resource coordinated mining. At the same time, as a renewable coal-associated resource, mine geothermal has significant economic and social benefits for hydrothermal mines with rich geothermal resources. At present, the utilization of hydrothermal geothermal energy as a clean heating energy source has developed rapidly. The utilization of geothermal resources is mainly for heating in urban residential areas, but it is not easy to arrange a series of geothermal well construction sites in residential areas or production mining areas. On the one hand, there is often a deviation between the ground location selected by the well site and the location of underground geothermal resources. On the other hand, even if the well site is selected, multiple production wells or reinjection wells need to be deployed at the same location to meet the ground's demand for geothermal energy. The common practice now is to set up multiple wellhead positions at a certain interval along a certain direction on the ground of the same well site, and implement multiple geothermal wells with different side drilling directions. Due to the limitation of ground construction space, the spacing between the wellheads of multiple geothermal wells often cannot meet the drilling needs. Therefore, geothermal resources cannot be effectively mined or recharged, which to some extent affects the development and utilization of geothermal energy. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a three-dimensional geothermal collection system based on hydrothermal mines and a method for arranging well locations thereof, which reduces the floor space required for ground construction at the well site by adopting a distributed collection and irrigation arrangement, thereby effectively saving ground space and improving the utilization rate of underground geothermal resources.

[0004] Technical solution: The present invention is a three-dimensional geothermal centralized mining system based on hydrothermal mines, comprising a fixed extraction well, a mobile extraction well, a mobile reinjection well, an extraction pipeline, a reinjection pipeline and a heat exchange station;

[0005] One end of the fixed extraction well is arranged on the ground, and the other end of the fixed extraction well extends to the geothermal reservoir; one end of the mobile extraction well is arranged in the tunnel of the recovery working face, and the other end of the mobile extraction well extends to the geothermal reservoir at the recovery working face; one end of the mobile reinjection well is arranged in the tunnel of the recovery working face, and the other end of the mobile reinjection well extends to the geothermal reservoir at the recovery working face;

[0006] One end of the fixed extraction well and one end of the mobile extraction well are connected to the heat exchange station via an extraction pipeline, and the heat exchange station is connected to one end of the mobile recharge well via a recharge pipeline;

[0007] The fixed extraction well and the mobile extraction well transport the high-temperature water in the geothermal reservoir at the recovery working face to the heat exchange station through the extraction pipeline, and the low-temperature water in the heat exchange station is transported to the geothermal reservoir through the reinjection pipeline and the mobile reinjection well.

[0008] Furthermore, the fixed extraction well includes several stages of casing connected in sequence.

[0009] Furthermore, the outer surfaces of the extraction pipeline and the reinjection pipeline are covered with a thermal insulation layer.

[0010] Furthermore, the pipeline in the extraction pipeline connected to one end of the mobile extraction well is arranged along the transportation lanes and transportation shafts of the mine.

[0011] Furthermore, the mobile reinjection well comprises a reinjection wellbore and a reinjection casing arranged in the reinjection wellbore, and reinforced concrete is filled between the reinjection casing and the reinjection wellbore.

[0012] Furthermore, the heat exchange station includes several stages of heat exchangers and water source heat pumps corresponding to the several stages of heat exchangers one by one. The extraction pipeline is connected to the several stages of heat exchangers in sequence, and the last stage of heat exchanger is connected to the recharging pipeline.

[0013] Based on the same inventive concept, a well location arrangement method of the present invention is used to select the well locations of the mobile extraction wells and the mobile reinjection wells in the above-mentioned hydrothermal mine three-dimensional geothermal centralized mining system. The well location arrangement method includes:

[0014] Establishing a mine geothermal geological model: Based on the mine geological drilling data and the thickness and distribution range of the mine geothermal reservoir, the variogram is used to organize and analyze the discrete drilling data, and a three-dimensional space interpolation algorithm is established based on the Kriging method. The mine geothermal geological model is established by combining the three-dimensional space interpolation algorithm with MATLAB software;

[0015] Exploration of water-rich areas and selection of sweet spots: The distribution of water-rich areas in the study area is determined through transient electromagnetic exploration technology, and the sweet spots of geothermal resources are further clarified to provide a data basis for the selection and layout of geothermal wells. At the same time, the geothermal reservoirs in the study area are divided into mining-affected areas and unaffected areas based on transient electromagnetic exploration data and geological exploration maps of the mine working face. Among them, the water-rich areas in the unaffected areas are initially selected as the sweet spots for the layout of fixed extraction wells for continuous extraction of geothermal resources. The selection of the location of the mobile extraction wells underground needs to be further accurately selected in the tunnels of the mining working face according to the specific conditions of the mining layout of the mine working face and the geological exploration data.

[0016] Determination of geothermal resource usage in the study area: Determine the demand for geothermal resources in the study area. By establishing a big data cloud platform for dynamic monitoring of geothermal resources, real-time monitoring of the daily, monthly, seasonal and annual demand for geothermal resources in the study area is carried out, and an annual geothermal resource usage curve is drawn. Based on this curve, the number of geothermal wells and the extraction volume of a single well are further determined;

[0017] Selection of fixed extraction well locations: Based on transient electromagnetic exploration data in areas not affected by mining, fixed extraction wells are built based on the sweet spots of geothermal resources to extract geothermal resources;

[0018] Mobile extraction well layout design: According to the underground transient electromagnetic exploration data, determine the sweet spot of geothermal resources in the mining face, and preliminarily determine the layout area of ​​mobile extraction wells; determine the number of mobile extraction wells, and design the layout of mobile extraction wells based on the determined layout area and number of mobile extraction wells;

[0019] Design of the position and quantity of mobile reinjection wells: Combined with the mine geothermal geological model, calculate the required number of mobile reinjection wells and determine the optimal position of the mobile reinjection wells.

[0020] Furthermore, based on the transient electromagnetic exploration data in the area not affected by mining, fixed extraction wells are built based on the sweet spot area of ​​geothermal resources to extract geothermal resources; including:

[0021] The in-situ permeability characteristics of the geothermal reservoir are solved through the in-situ permeability test method, the single well water yield of the fixed extraction well is determined through the pumping test, and the well body structure of the fixed extraction well is determined according to the logging data, finally realizing the well site selection and design of the fixed extraction well.

[0022] Furthermore, according to the underground transient electromagnetic exploration data, the sweet spot of geothermal resources in the mining face is determined, and the layout area of ​​the mobile extraction wells is preliminarily determined; the number of mobile extraction wells is determined, and the layout of the mobile extraction wells is arranged based on the determined layout area of ​​the mobile extraction wells and the number of mobile extraction wells, including:

[0023] Based on the underground transient electromagnetic exploration data, the sweet spot of geothermal resources in the mining face is determined, and the layout area of ​​the mobile extraction well is preliminarily determined;

[0024] Hydrological observation holes are arranged in the tunnels in the sweet spots of geothermal resources in the mining face. The in-situ permeability characteristics of the reservoir are solved by the in-situ permeability test method. The changes in reservoir permeability with mining of the working face and the water inflow of the mobile extraction wells are calculated according to the analytical algorithm, and the water inflow calculation formula suitable for the study area is established.

[0025] The curve error fitting method is used to fit the relationship curve between the stable water inflow Q of a single well and the water level drawdown S of a pumping well. The Q=f(S) curve is obtained by fitting the pumping test. The stable water inflow Q of a single well at different water level drawdowns S is calculated. The least squares method is used in the Origin software to calculate the relationship between the stable water inflow Q of a single well and the water level drawdown S.

[0026] The number of mobile extraction wells is determined based on the annual geothermal resource usage curve in the study area, the water yield change curve of fixed extraction wells, and the water yield curve of mobile extraction wells.

[0027] Furthermore, combined with the mine geothermal geological model, the number of required mobile reinjection wells is calculated and the optimal layer position of the mobile reinjection wells is determined, including:

[0028] Based on the mine geothermal geological model, the mine geothermal geological model was gridded by Comsol numerical simulation software. The multi-field coupling function of Comsol numerical simulation software was used to predict and analyze the spatiotemporal evolution characteristics of the thermal reservoir seepage field, temperature field and deformation field under different geothermal development schemes. The formation deformation and heat transfer mechanism during the reinjection process were studied, revealing the development and evolution trend of the thermal reservoir temperature field, seepage field and deformation field under different reinjection conditions, and analyzing the time and temperature effect change law of the thermal reservoir physical property parameters.

[0029] On the basis of clarifying the physical parameters, seepage field, temperature field and deformation field of the thermal reservoir, the reinjection volume of a single geothermal well is determined by considering the seepage field of the thermal reservoir, the reinjection temperature is determined by considering the temperature field, and the well structure is designed based on the deformation field to determine the optimal return water volume and return water temperature of the geothermal well. At the same time, the number of mobile reinjection wells required is calculated in combination with the wastewater return water volume and wastewater temperature in the study area.

[0030] Comsol numerical simulation software is used to determine the damage changes of the working face floor when different reinjection well layers are reinjected, the safety factor of the thermal reservoir during geothermal well reinjection is clarified, and the optimal layer of the mobile reinjection well is determined based on the safety factor condition.

[0031] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows:

[0032] The three-dimensional geothermal collection system based on hydrothermal mines of the present invention makes the construction of geothermal wells not limited by the area of ​​the ground site, fully utilizes the construction technical conditions and production systems in the mining area, and jointly arranges distributed geothermal wells above and below the well to achieve coordinated exploitation of coal resources and geothermal resources; specifically as follows: fixed extraction wells are used for long-term extraction and utilization of geothermal resources to ensure the basic extraction volume of geothermal resources; mobile extraction wells and mobile reinjection wells are arranged in a mobile manner to extract and reinject geothermal resources in a short period of time to ensure that the demand for geothermal resource supply is met; according to the continuous changes in the mining working face of the mine, the mobile extraction wells and mobile reinjection wells are changed according to the layout of the working face. Such an arrangement greatly saves the land resources of the well site and improves the utilization rate and efficiency of the extraction and injection of geothermal resources.

[0033] The well location arrangement method of the present invention is used to determine the optimal arrangement parameters of the mobile extraction wells and the mobile reinjection wells of the hydrothermal mine three-dimensional geothermal centralized mining system of the present invention, so as to realize the continuous and stable heating of the geothermal centralized mining system and extend the service life of the thermal field. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the structure of a three-dimensional geothermal centralized mining system based on a hydrothermal mine disclosed in an embodiment of the present invention;

[0035] Figure 2 A layer layout diagram of a three-dimensional geothermal centralized mining system based on a hydrothermal mine disclosed in an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the structure of a fixed extraction well disclosed in an embodiment of the present invention;

[0037] Figure 4 A schematic diagram of the structure of a mobile recharging well disclosed in an embodiment of the present invention;

[0038] Figure 5 This is a working principle diagram of a heat exchange station disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is described in detail below in conjunction with specific implementation methods and the accompanying drawings of the specification.

[0040] like Figures 1 to 4As shown, the three-dimensional geothermal collection system based on hydrothermal mine of the present invention includes a fixed extraction well 1, a mobile extraction well 2, a mobile reinjection well 3, a reinjection wellbore 31, a reinjection casing 32, reinforced concrete 33, an extraction pipeline 61, a reinjection pipeline 62 and a heat exchange station 9, a primary water source heat pump 91, a secondary water source heat pump 92, a tertiary water source heat pump 93, a primary plate heat exchanger 94, a secondary plate heat exchanger 95, a tertiary plate heat exchanger 96, a heat storage tank 97, a water treatment device 98, and a tail water treatment device 99. Among them, the number of mobile extraction wells 2 is several, and in this embodiment, 15 mobile extraction wells 2 are set.

[0041] like Figure 1 and Figure 2 As shown, one end of the fixed extraction well 1 is arranged at the industrial square 5 on the ground, and the other end of the fixed extraction well 1 passes downward through the overburden stratum 7 and extends to the geothermal reservoir 4. One end of a plurality of mobile extraction wells 2 is arranged in the tunnel of the mining face 8, and the other end of the plurality of mobile extraction wells 2 extends to the geothermal reservoir 4 below the mining face 8. One end of the mobile reinjection well 3 is arranged in the tunnel of the mining face 8, and the other end of the mobile reinjection well 3 extends to the geothermal reservoir 4 below the mining face 8.

[0042] One end of the fixed extraction well 1 and one end of several mobile extraction wells 2 are connected to the heat exchange station 9 via the extraction pipeline 61 , and the heat exchange station 9 is connected to one end of the mobile reinjection well 3 via the reinjection pipeline 62 .

[0043] The fixed extraction well 1 and several mobile extraction wells 2 transport the high-temperature water in the geothermal reservoir at the recovery working face to the heat exchange station 9 through the extraction pipeline 61, and the low-temperature water in the heat exchange station 9 is transported to the geothermal reservoir through the reinjection pipeline 62 and the mobile reinjection well 3.

[0044] The mobile extraction well 2 is arranged in the tunnel of the mining face 8 and is relatively close to the geothermal reservoir 4 . The mobile extraction well 2 is configured as a primary casing and directly extends to the geothermal reservoir 4 .

[0045] The pipeline in the extraction pipeline 61 connected to one end of the mobile extraction well 2 is arranged along the transportation lanes and transportation shafts of the mine to fully utilize the construction technical conditions and production systems in the mining area and reduce the construction workload.

[0046] like Figure 3 As shown, the fixed extraction well 1 includes several levels of casing connected in sequence; in this embodiment, the fixed extraction well 1 is composed of several levels of single-open casing 11 and double-open casing 12 connected in sequence, so as to facilitate the step-by-step arrangement of casing (single-open casing 11 and double-open casing 12) underground in the industrial square 5.

[0047] like Figure 4As shown, the mobile reinjection well 3 includes a reinjection wellbore 31 and a reinjection casing 32. The reinjection casing 32 is arranged in the reinjection wellbore 31. Reinjection casing 32 is filled with reinforced concrete 33 between the reinjection casing 32 and the reinjection wellbore 31 so that the reinjection casing 32 is firmly fixed to the inner wall of the reinjection wellbore 31. The reinjection casing 32 is preferably a HDPE corrugated pipe.

[0048] The outer surfaces of the extraction pipeline 61 and the recharging pipeline 62 are covered with a thermal insulation layer to keep the water in the pipelines warm and reduce heat loss.

[0049] like Figure 5 As shown, the heat exchange station 9 includes several stages of heat exchangers and water source heat pumps corresponding to the several stages of heat exchangers. The extraction pipeline 61 is connected to the several stages of heat exchangers in sequence, and the last stage of heat exchanger is connected to the recharging pipeline 62.

[0050] In this embodiment, the heat exchange station 9 includes three-stage heat exchangers (a primary plate heat exchanger 94, a secondary plate heat exchanger 95, and a tertiary plate heat exchanger 96) and three-stage water source heat pumps (a primary water source heat pump 91, a secondary water source heat pump 92, and a tertiary water source heat pump 93). The extraction pipeline 61 is connected to the three-stage heat exchangers in sequence through the water treatment device 98, and the last stage heat exchanger (the tertiary plate heat exchanger 96) is connected to the recharging pipeline 62 through the tail water treatment device 99. The primary plate heat exchanger 94 corresponds to the primary water source heat pump 91, the secondary plate heat exchanger 95 corresponds to the secondary water source heat pump 92, and the tertiary plate heat exchanger 96 corresponds to the tertiary water source heat pump 93. The primary water source heat pump 91 delivers the heat at the primary plate heat exchanger 94 to the heat storage tank 97, and the heat storage tank 97 supplies the stored hot water to the primary users (such as building heating, bathing, etc.); the secondary water source heat pump 92 delivers the heat at the secondary plate heat exchanger 95 to the secondary users (such as coal preparation plant heating, wellhead antifreeze, industrial heating, etc.); the tertiary water source heat pump 93 delivers the heat at the tertiary plate heat exchanger 96 to the tertiary users (such as geothermal greenhouses, aquaculture, water bath therapy, etc.). The heat exchange station 9 realizes the hierarchical and efficient utilization of geothermal heat.

[0051] The three-dimensional geothermal centralized mining system based on hydrothermal mines of the present invention makes the construction of geothermal wells not limited by the ground site area, fully utilizes the construction technical conditions and production systems in the mining area, and jointly arranges distributed mining and irrigation geothermal wells above and below the well to achieve coordinated mining of coal resources and geothermal resources.

[0052] Example 2

[0053] A well location arrangement method of the present invention is used to select the well locations of the mobile extraction well 2 and the mobile reinjection well 3 in the hydrothermal mine three-dimensional geothermal centralized mining system of Example 1. The well location arrangement method includes:

[0054] S1. Establishment of mine geothermal geological model: Based on the mine geological drilling data and the thickness and distribution range of the mine geothermal reservoir, the variation function is used to organize and analyze the discrete drilling data, and a three-dimensional space interpolation algorithm is established based on the Kriging method. The mine geothermal geological model and visualization are established by combining the three-dimensional space interpolation algorithm with MATLAB software.

[0055] S2. Exploration of water-rich areas and selection of sweet spots: The distribution of water-rich areas in the study area is determined through transient electromagnetic exploration technology, and the sweet spots of geothermal resources are further clarified to provide a data basis for the selection and layout of geothermal wells. At the same time, the geothermal reservoirs in the study area are divided into mining-affected areas and unaffected areas based on transient electromagnetic exploration data and geological exploration maps of the mine working face. Among them, the water-rich areas in the areas unaffected by mining are preliminarily selected as the sweet spots for the layout of fixed extraction wells for continuous extraction of geothermal resources. The selection of the location of the mobile extraction wells underground requires further precise selection in the tunnels of the mining working face based on the mining layout of the mine working face and geological exploration data.

[0056] S3. Determination of geothermal resource usage in the study area: Determine the demand for geothermal resources in the study area. By establishing a big data cloud platform for dynamic monitoring of geothermal resources, monitor the daily, monthly, seasonal and annual demand for geothermal resources in the study area in real time, and draw an annual geothermal resource usage curve. Based on this curve, further determine the number of geothermal wells and the extraction volume of a single well;

[0057] S4. Selection of fixed extraction well locations: Based on the transient electromagnetic exploration data in the area not affected by mining, fixed extraction wells are built based on the geothermal resource sweet spot area to extract geothermal resources.

[0058] In this embodiment, first, the in-situ permeability characteristics of the geothermal reservoir are solved by the in-situ permeability test method, the single well water yield of the fixed pumping well is determined by the pumping test, and the well body structure of the fixed pumping well is determined according to the logging data, and finally the well site selection and design of the fixed pumping well are realized.

[0059] S5, mobile extraction well layout design: According to the underground transient electromagnetic exploration data, determine the geothermal resource sweet spot area of ​​the recovery working face, preliminarily determine the mobile extraction well layout area; determine the number of mobile extraction wells, and design the mobile extraction well layout based on the determined mobile extraction well layout area and the number of mobile extraction wells. The specific steps of step S5 are as follows:

[0060] S5.1. Determine the sweet spot of geothermal resources at the mining face based on the underground transient electromagnetic exploration data, and preliminarily determine the layout area of ​​the mobile extraction wells;

[0061] S5.2. Arrange hydrological observation holes in the tunnels in the sweet spots of geothermal resources in the mining working face, solve the in-situ permeability characteristics of the reservoir by the in-situ permeability test method, calculate the change of reservoir permeability with mining of the working face and the water inflow of the mobile extraction wells according to the analytical algorithm, and establish a water inflow calculation formula suitable for the study area;

[0062] The water volume in the coal-heat co-production geothermal well shows pipe flow characteristics. At this time, the aquifer-geothermal well system can be decomposed into an aquifer seepage subsystem and a geothermal well pipe flow subsystem. The water flow calculation can be coupled through the water flow calculation models of these two subsystems.

[0063] 1) Seepage model

[0064] When the geothermal well is pumped, the groundwater flow in the aquifer presents an obvious confined three-dimensional flow. Without considering the change of groundwater density, the seepage of groundwater in confined aquifer in the three-dimensional space of porous media can be expressed by the following partial differential equation (1):

[0065]

[0066] Where: K xx , K yy , K zz is the permeability coefficient in the xyz axis direction. It is assumed here that the main direction of the permeability coefficient is consistent with the direction of the coordinate axis. The dimension is LT -1 ; h is the water head height [L]; S s is the elastic water release coefficient of porous media [L -1 ]; t is time [T].

[0067] This equation can be solved numerically. The most commonly used tool is MODFLOW software, which is based on the finite difference method of block centers. It divides continuous space and time into a series of discrete points. The continuous partial derivatives are replaced by the head difference formula (2 and 3) to form a linear equation system, which can approximately solve the equation (4).

[0068]

[0069] Where: h i+1 m is the water head at node i+1 at time m; h i m is the water head at node i at time m.

[0070]

[0071] Where: h i m+1 is the water head at node i+1 at time m+1; h i mis the water head at node i at time m.

[0072] [A]{h}=[q] (4)

[0073] Where: [A] is the coefficient matrix; {h} is the head matrix; [q] is the constant term.

[0074] 2) Pipeline flow model

[0075] A geothermal well can be considered as a small pipe. When the pipe is fully saturated, the flow in the pipe can be assumed to be one-dimensional along the axis of the pipe. The general equations for turbulent and laminar flow are:

[0076]

[0077] In the pipeline:

[0078] v=nu n=1 v=u (6)

[0079] At this time, equation (5) can be transformed into:

[0080]

[0081] Where: ΔH is the head loss along the way [L]; f is the friction coefficient, dimensionless; d is the pipe diameter [L]; u is the average flow velocity [LT -1 ]; n is the porosity; v is the flow velocity [LT -1 ]; I is the length along the path [L]; g is the gravitational acceleration [LT -2 ].

[0082] The friction coefficient in equation (7) is a function of the flow rate and the relative roughness of the pipe. Equation (7) is called the Darcy-Weisbach equation. The deformation of (7) is as follows:

[0083]

[0084] The flow rate in the pipe is:

[0085]

[0086] In the formula: K' represents the "equivalent permeability coefficient" in the pipeline, J is the hydraulic gradient in the pipeline, and A is the water-passing cross-sectional area of ​​the pipeline, that is, the flow rate in the pipeline is the same as the flow rate calculation formula in the aquifer seepage. The friction coefficient is related to the Reynolds number, and different Reynolds numbers correspond to different friction coefficients.

[0087] (1) When the water flow with Re < 3000 is laminar, the friction coefficient can be calculated using the following formula:

[0088]

[0089] In the formula, υ is the viscosity coefficient [ML -1 T -1 ].So

[0090]

[0091] Substituting (11) into (9), we obtain:

[0092]

[0093] (2) When the water flow with Re>3000 is turbulent, the friction coefficient can be calculated using the following formula

[0094]

[0095] Then Substituting (13) into (9), we obtain:

[0096]

[0097] In summary, the flow calculation formula for geothermal wells is

[0098]

[0099] Where: K c is the roughness height of the inner wall of the borehole [L]; μ is the viscosity coefficient [ML- 1 T- 1 ]; τ is the roughness of the inner wall of the drill hole.

[0100] The water exchange between the porous medium groundwater seepage zone (aquifer) and the geothermal well can be calculated linearly based on the hydraulic head difference between the two areas:

[0101] Q ex =α*(h p -h i ) (15)

[0102] Where: Q ex is the amount of water exchanged between the aquifer and the pipeline [L 3 T -1 ], negative values ​​indicate that water flows from the aquifer into the pipe; conversely, positive values ​​indicate that water flows from the pipe into the aquifer; α is the hydraulic conductivity of the exchange zone between the aquifer and the pipe [L 2 T -1 ]; hp is the water head in the pipe of the exchange area [L]; hi is the water head in the aquifer of the exchange area [L].

[0103] According to the law of conservation of energy, the amount of groundwater flowing into the pipe is equal to the amount of water in the pipe, that is:

[0104] ΣQex +Q p =0 (16)

[0105]

[0106] In this way, the seepage of groundwater is coupled with the pipe flow in the geothermal well, and equation (17) is the model for calculating the water yield of the geothermal well.

[0107] S5.3. The curve error fitting method is used to fit the relationship curve between the stable water inflow Q of a single well and the water level drawdown S of a pumping well. The Q=f(S) curve is obtained by fitting the pumping test. The stable water inflow Q of a single well at different water level drawdowns S is calculated. The least squares method is used in the Origin software to calculate the relationship between the stable water inflow Q of a single well and the water level drawdown S.

[0108] S5.4. Determine the number of mobile extraction wells based on the annual geothermal resource usage curve in the study area, the water yield change curve of fixed extraction wells, and the water yield curve of mobile extraction wells.

[0109] S6. Design of the position and quantity of mobile reinjection wells: Combined with the mine geothermal geological model, calculate the number of mobile reinjection wells required and determine the optimal position of the mobile reinjection wells. The specific steps are as follows:

[0110] S6.1. Based on the mine geothermal geological model established in step S1, the mine geothermal geological model is gridded by Comsol numerical simulation software, and then the temporal and spatial evolution characteristics of the seepage field, temperature field and deformation field of the thermal reservoir under different geothermal development schemes are predicted and analyzed based on the multi-field coupling function of Comsol numerical simulation software; the formation deformation and heat transfer mechanism during the reinjection process are studied, the development and evolution trend of the temperature field, seepage field and deformation field of the thermal reservoir under different reinjection conditions are revealed, and the time and temperature effect change law of the thermal reservoir physical parameters is analyzed.

[0111] S6.2. On the basis of clarifying the thermal reservoir physical parameters, seepage field, temperature field and deformation field, first consider the thermal reservoir seepage field to determine the reinjection volume of a single geothermal well, then consider the temperature field to determine the reinjection temperature, and finally design the well structure based on the deformation field to determine the optimal return water volume and return water temperature of the geothermal well. At the same time, combined with the basic data such as the wastewater return water volume and wastewater temperature in the study area, calculate the number of mobile reinjection wells required;

[0112] S6.3. Use Comsol numerical simulation software to determine the damage changes of the working face floor when different reinjection well layers are reinjected, clarify the safety factor of the thermal reservoir during geothermal well reinjection, and determine the optimal layer of the mobile reinjection well based on the safety factor condition.

[0113] A well location arrangement method of the present invention is used to determine the optimal arrangement parameters of the mobile extraction wells and the mobile reinjection wells of the three-dimensional geothermal centralized mining system based on the hydrothermal mine of the present invention, so as to realize the continuous and stable heating of the geothermal centralized mining system and extend the service life of the thermal field.

Claims

1. A three-dimensional geothermal centralized mining system based on hydrothermal mines, characterized by: It comprises a fixed extraction well (1), a mobile extraction well (2), a mobile reinjection well (3), an extraction pipeline (61), a reinjection pipeline (62) and a heat exchange station (9); One end of the fixed extraction well (1) is arranged on the ground, and the other end of the fixed extraction well (1) extends downward to the geothermal reservoir (4); the number of the mobile extraction wells (2) is a plurality, one end of the plurality of mobile extraction wells (2) is arranged in the tunnel of the recovery working face (8), and the other end of the plurality of mobile extraction wells (2) extends to the geothermal reservoir (4) below the recovery working face (8); one end of the mobile reinjection well (3) is arranged in the tunnel of the recovery working face (8), and the other end of the mobile reinjection well (3) extends to the geothermal reservoir below the recovery working face (8); One end of the fixed extraction well (1) and one end of a plurality of mobile extraction wells (2) are connected to a heat exchange station (9) via an extraction pipeline (61), and the heat exchange station (9) is connected to one end of a mobile reinjection well (3) via a reinjection pipeline (62); The fixed extraction well (1) and a plurality of mobile extraction wells (2) transport high-temperature water in the geothermal reservoir at the recovery working face to the heat exchange station (9) via an extraction pipeline (61), and the low-temperature water in the heat exchange station (9) is transported to the geothermal reservoir via a reinjection pipeline (62) and the mobile reinjection wells (3).

2. The three-dimensional geothermal centralized mining system based on hydrothermal mines according to claim 1 is characterized by: The fixed extraction well (1) comprises a plurality of stages of casings connected in sequence.

3. The three-dimensional geothermal centralized mining system based on hydrothermal mines according to claim 1 is characterized by: The outer surfaces of the extraction pipeline (61) and the reinjection pipeline (62) are covered with a thermal insulation layer.

4. The three-dimensional geothermal centralized mining system based on hydrothermal mines according to claim 1 is characterized by: The pipeline in the extraction pipeline (61) connected to one end of the mobile extraction well (2) is arranged along the transportation lane and transportation shaft of the mine.

5. The three-dimensional geothermal centralized mining system based on hydrothermal mines according to claim 1 is characterized by: The mobile reinjection well (3) comprises a reinjection wellbore (31) and a reinjection casing (32) arranged in the reinjection wellbore (31), and reinforced concrete (33) is filled between the reinjection casing (32) and the reinjection wellbore (31).

6. The three-dimensional geothermal centralized mining system based on hydrothermal mines according to claim 1 is characterized by: The heat exchange station (9) comprises a plurality of stages of heat exchangers and water source heat pumps corresponding to the plurality of stages of heat exchangers one by one. The extraction pipeline (61) is connected to the plurality of stages of heat exchangers in sequence, and the last stage of heat exchanger is connected to the recharging pipeline (62).

7. A method for well location arrangement, characterized in that: The well location arrangement method is used to select the well locations of the mobile extraction well (2) and the mobile reinjection well (3) in the hydrothermal mine three-dimensional geothermal centralized mining system according to any one of claims 1 to 6, and the well location arrangement method comprises: Establishing a mine geothermal geological model: Based on the mine geological drilling data and the thickness and distribution range of the mine geothermal reservoir, the variogram is used to organize and analyze the discrete drilling data, and a three-dimensional space interpolation algorithm is established based on the Kriging method. The mine geothermal geological model is established by combining the three-dimensional space interpolation algorithm with MATLAB software, thereby realizing the visualization of the three-dimensional geological model; Exploration of water-rich areas and selection of sweet spots: The distribution of water-rich areas in the study area is determined through transient electromagnetic exploration technology, and the sweet spots of geothermal resources are further clarified to provide a data basis for the selection and layout of geothermal wells. At the same time, the geothermal reservoirs in the study area are divided into mining-affected areas and unaffected areas based on transient electromagnetic exploration data and geological exploration maps of the mine working face. Among them, the water-rich areas in the unaffected areas are initially selected as the sweet spots for the layout of fixed extraction wells for continuous extraction of geothermal resources. The selection of the location of the mobile extraction wells underground needs to be further accurately selected in the tunnels of the mining working face according to the specific conditions of the mining layout of the mine working face and the geological exploration data. Determination of geothermal resource usage in the study area: Determine the demand for geothermal resources in the study area. By establishing a big data cloud platform for dynamic monitoring of geothermal resources, real-time monitoring of the daily, monthly, seasonal and annual demand for geothermal resources in the study area is carried out, and an annual geothermal resource usage curve is drawn. Based on this curve, the number of geothermal wells and the extraction volume of a single well are further determined; Selection of fixed extraction well locations: Based on transient electromagnetic exploration data in areas not affected by mining, fixed extraction wells are built based on the sweet spots of geothermal resources to extract geothermal resources; Mobile extraction well layout design: According to the underground transient electromagnetic exploration data, determine the sweet spot of geothermal resources in the mining face, and preliminarily determine the layout area of ​​mobile extraction wells; determine the number of mobile extraction wells, and design the layout of mobile extraction wells based on the determined layout area and number of mobile extraction wells; Design of the position and quantity of mobile reinjection wells: Combined with the mine geothermal geological model, calculate the required number of mobile reinjection wells and determine the optimal position of the mobile reinjection wells.

8. The well location arrangement method according to claim 7, characterized in that: Based on the transient electromagnetic exploration data in the unaffected area, fixed extraction wells are built based on the sweet spot area of ​​geothermal resources to extract geothermal resources; including: The in-situ permeability characteristics of the geothermal reservoir are solved through the in-situ permeability test method, the single well water yield of the fixed extraction well is determined through the pumping test, and the well body structure of the fixed extraction well is determined according to the logging data, finally realizing the well site selection and design of the fixed extraction well.

9. The well location arrangement method according to claim 7, characterized in that: Based on the underground transient electromagnetic exploration data, the sweet spot of geothermal resources in the mining face is determined, and the layout area of ​​the mobile extraction well is preliminarily determined; Determine the number of mobile extraction wells, and perform mobile extraction well layout based on the determined mobile extraction well layout area and the number of mobile extraction wells, including: Based on the underground transient electromagnetic exploration data, the sweet spot of geothermal resources in the mining face is determined, and the layout area of ​​the mobile extraction well is preliminarily determined; Hydrological observation holes are arranged in the tunnels in the sweet spots of geothermal resources in the mining face. The in-situ permeability characteristics of the reservoir are solved by the in-situ permeability test method. The changes in reservoir permeability with mining of the working face and the water inflow of the mobile extraction wells are calculated according to the analytical algorithm, and the water inflow calculation formula suitable for the study area is established. The curve error fitting method is used to fit the relationship curve between the stable water inflow Q of a single well and the water level drawdown S of a pumping well. The Q=f(S) curve is obtained by fitting the pumping test. The stable water inflow Q of a single well at different water level drawdowns S is calculated. The least squares method is used in the Origin software to calculate the relationship between the stable water inflow Q of a single well and the water level drawdown S. The number of mobile extraction wells is determined based on the annual geothermal resource usage curve in the study area, the water yield change curve of fixed extraction wells, and the water yield curve of mobile extraction wells.

10. The well location arrangement method according to claim 7, characterized in that: Combined with the mine geothermal geological model, calculate the number of mobile reinjection wells required and determine the optimal layer for the mobile reinjection wells, including: Based on the mine geothermal geological model, the mine geothermal geological model was gridded by Comsol numerical simulation software. The multi-field coupling function of Comsol numerical simulation software was used to predict and analyze the spatiotemporal evolution characteristics of the thermal reservoir seepage field, temperature field and deformation field under different geothermal development schemes. The formation deformation and heat transfer mechanism during the reinjection process were studied, revealing the development and evolution trend of the thermal reservoir temperature field, seepage field and deformation field under different reinjection conditions, and analyzing the time and temperature effect change law of the thermal reservoir physical property parameters. On the basis of clarifying the physical parameters, seepage field, temperature field and deformation field of the thermal reservoir, the reinjection volume of a single geothermal well is determined by considering the seepage field of the thermal reservoir, the reinjection temperature is determined by considering the temperature field, and the well structure is designed based on the deformation field to determine the optimal return water volume and return water temperature of the geothermal well. At the same time, the number of mobile reinjection wells required is calculated in combination with the wastewater return water volume and wastewater temperature in the study area. Comsol numerical simulation software is used to determine the damage changes of the working face floor when different reinjection well layers are reinjected, the safety factor of the thermal reservoir during geothermal well reinjection is clarified, and the optimal layer of the mobile reinjection well is determined based on the safety factor condition.

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