Hydrothermal terrestrial heat group mining and group irrigation development method

Abstract

The main purpose of the invention is to provide a three-dimensional unsteady-state temperature field distribution model in a one-sampling and one-irrigation mode. Inputting reference parameters, and obtaining a temperature field change distribution diagram through the three-dimensional unsteady-state temperature field distribution model; spline interpolation processing is carried out on the temperature field change distribution diagram for several times; after spline interpolation processing, adaptive threshold binarization segmentation is adopted, a temperature distribution change contour line is extracted, and a cold front migration contour is marked; geometric features of the cold front migration contour are obtained, and a well spacing constraint field is constructed according to the geometric features; according to the well spacing constraint field, a distribution probability density distribution diagram of mining wells and recharge wells during group mining and group irrigation development is determined, so that an optimal well spacing threshold value during group mining and group irrigation development is determined. According to the method, the dynamic temperature field model is established, the cold front features are extracted, and the constraint field is constructed, so that the well spacing is optimally arranged during the group mining and group irrigation development of the hydrothermal terrestrial heat. The method can effectively avoid thermal interference of recharged cold water on the pumping well, and the geothermal exploitation efficiency and sustainability are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geothermal exploitation, and particularly relates to a water-heat type geothermal group extraction and group irrigation development method. BACKGROUND

[0002] In the process of group extraction and group irrigation development of water-heat type geothermal resources, the reasonable arrangement of well spacing is crucial. Unreasonable well spacing may cause thermal interference of recharge cold water on the pumping well, and reduce the efficiency and sustainability of geothermal exploitation. SUMMARY

[0003] Therefore, the present application aims to provide a water-heat type geothermal group extraction and group irrigation development method, in particular a well spacing optimization method based on dynamic temperature field modeling and cold front feature extraction, to solve the problem of reasonable arrangement of well spacing in the water-heat type geothermal group extraction and group irrigation development, and improve the efficiency and sustainability of geothermal exploitation.

[0004] The main purpose of the present application is to provide a three-dimensional unsteady temperature field distribution model under the one extraction and one irrigation mode; input the reference parameters, and obtain the temperature field change distribution map through the three-dimensional unsteady temperature field distribution model; The temperature field change distribution map is subjected to spline interpolation processing several times; after the spline interpolation processing, adaptive threshold binarization segmentation is adopted to extract the temperature distribution change contour, and the cold front migration profile is marked; The geometric features of the cold front migration profile are obtained, and the well spacing constraint field is constructed according to the geometric features: According to the well spacing constraint field, the arrangement probability density distribution map of the extraction well and the recharge well during the group extraction and group irrigation development is determined, so as to determine the optimal well spacing threshold during the group extraction and group irrigation development.

[0005] Further, the method for constructing the three-dimensional unsteady temperature field distribution model under the one extraction and one irrigation mode comprises: The recharge temperature, extraction / recharge water volume, formation thermal conductivity and porosity of the recharge well and the extraction well under the one extraction and one irrigation mode in different regions are collected, the finite element method is used for time series simulation, and the temperature field distribution map in different extraction periods is generated; The temperature field distribution maps of adjacent time spans are superimposed and compared, the temperature front advancing features are extracted, the maximum distance of the front migration is taken as the reference to generate the time-front displacement curve, and the three-dimensional unsteady temperature field distribution model for the space-time evolution prediction of the temperature field is established.

[0006] Further, the method for time series simulation by using the finite element method comprises: Obtain the geothermal reservoir area detection data, construct a geothermal reservoir area model according to the geothermal reservoir area detection data, and set at least one group of pumping wells and recharge wells in the geothermal reservoir area model; The non-steady-state heat conduction-convection equation is constructed to couple the fluid flow and heat transfer to form the configuration of physical fields in the regional model of the geothermal reservoir; The boundary conditions of the pumping well and the recharge well are configured to obtain the formation boundary conditions of the regional model of the geothermal reservoir; the time span and the maximum value of the time span are set; The regional model of the geothermal reservoir is divided into a plurality of finite element units according to the time span, so as to generate the temperature field distribution map of different exploitation periods.

[0007] Further, the method for extracting the temperature front advancing characteristics comprises: The temperature field distribution maps of adjacent time spans are superimposed and compared; the temperature front is defined as the region boundary with a large temperature change rate, and the time-front displacement curve is generated based on the maximum distance of the front migration; The temperature field space-time evolution prediction model is established by fitting the time-front displacement curve, which is used to predict the position and advancing speed of the temperature front at different times, so as to obtain the temperature front advancing characteristics.

[0008] Further, the well spacing constraint field is established according to the following method: The temperature field change distribution map is subjected to a plurality of spline interpolations, The adaptive threshold binary segmentation is adopted to extract the temperature distribution change contour, the temperature reference value is set as the boundary to obtain the temperature distribution change contour, and the cold front migration contour is marked; The well spacing constraint field is constructed based on the geometric characteristics of the cold front contour; the constraint field boundary equation is defined as: ; Wherein, v max is the maximum migration rate of the cold front (m / year), t critical is the allowed safe exploitation period (years), σ T is the spatial variation coefficient of the temperature field, reflecting the degree of change of the temperature field in space; and a is a safety factor, and the value range is 1.2~1.5.

[0009] Further, the method for determining the optimal well spacing threshold in the group exploitation and group irrigation development is as follows: The constraint field boundary is mapped to the geographic coordinate system, and the Voronoi diagram algorithm is adopted to divide the exploitation unit, so as to ensure that the well spacing in each unit is greater than d_min; Combined with the permeability anisotropy of the geothermal reservoir, the well group layout is adjusted to be radial or grid-shaped, so as to minimize the cold front interference area.

[0010] This invention optimizes the well spacing during hydrothermal geothermal group extraction and irrigation by establishing a dynamic temperature field model, extracting cold front characteristics, and constructing a constraint field. This method effectively avoids thermal interference from reinjected cold water to pumping wells, improving geothermal extraction efficiency and sustainability. Attached Figure Description

[0011] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0012] 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.

[0013] Reference Figure 1 A method for developing hydrothermal geothermal mass extraction and irrigation systems includes the following steps: A three-dimensional unsteady temperature field distribution model under the one-sampling-one-irrigation mode is constructed; the baseline parameters are input, and the temperature field change distribution map is obtained through the three-dimensional unsteady temperature field distribution model; The temperature field change distribution map is subjected to several spline interpolation processes; after spline interpolation, adaptive threshold binarization segmentation is used to extract the temperature distribution change contour lines and mark the cold front migration profile. Obtain the geometric features of the cold front migration profile, and construct a well spacing constraint field based on the geometric features: Based on the well spacing constraint field, determine the probability density distribution map of the layout of mining wells and recharge wells during the development of mass mining and irrigation, thereby determining the optimal well spacing threshold during the development of mass mining and irrigation.

[0014] Furthermore, the method for constructing a three-dimensional unsteady temperature field distribution model under the one-sampling-one-irrigation mode includes: Data on reinjection temperature, production / reinjection water volume, formation thermal conductivity, and porosity were collected from reinjection wells and production wells under a single-production-one-injection model in different regions. Time was divided into several discrete time periods t1, t2, ..., tn. A time series simulation was performed using the finite element method to generate data for different production periods (t1, t2, ..., tn). n Temperature field distribution diagram; For adjacent time spans ( ∇ The temperature field distribution maps of t = tᵢ₊1−tᵢ are superimposed and compared to extract the temperature front advancement characteristics. The time-front displacement curve is generated based on the maximum front migration distance, and a three-dimensional unsteady temperature field distribution model for spatiotemporal evolution prediction of the temperature field is established.

[0015] In practice, geological, hydrological, and thermal property parameters of the hydrothermal geothermal area are collected, including formation thermal conductivity, porosity, rock and fluid density, and specific heat capacity. Baseline parameters such as reinjection temperature, extraction water volume, and reinjection water volume are determined. A three-dimensional unsteady-state temperature field distribution model under a one-extraction-one-injection mode is established using finite element software. The above parameters are input for time-series simulation, generating temperature field distribution maps for different extraction periods.

[0016] By overlaying and comparing temperature field distribution maps of adjacent time spans, the characteristics of temperature front advancement are extracted, time-front displacement curves are generated, and a spatiotemporal evolution prediction model for the temperature field is established.

[0017] The above-mentioned method for time series simulation using the finite element method includes: acquiring geothermal reservoir area exploration data, constructing a geothermal reservoir area model based on the geothermal reservoir area exploration data, setting at least one set of pumping wells and reinjection wells in the geothermal reservoir area model; constructing unsteady heat conduction-convection equations, and coupling fluid flow and heat transfer to form the configuration of the physical field in the geothermal reservoir area model; ; Where ρ: density of the rock-fluid mixture ( kg / m 3 ), C p Specific heat capacity of the mixture ( J / kg ⋅ K）， T: Temperature （K）， t: time (s), k: thermal conductivity of the formation (W / (m⋅K)), ρ f Fluid density ( kg / m 3 ), C p,f Specific heat capacity of fluids ( J / kg ⋅ K), v: Fluid seepage velocity vector (m / s) ，Q： heat source item (W / m 3 ），∇T : Value representing temperature difference , ∂T / ∂t : Represents the change of temperature field over time; configures the boundary conditions of pumping wells and reinjection wells to obtain the formation boundary conditions of the geothermal reservoir region model; sets the time span and the maximum value of the time span; divides the geothermal reservoir region model into several finite element elements according to the time span, thereby generating different mining periods (t1, t2, ..., t...). n Temperature field distribution diagram.

[0018] The methods for extracting the advance characteristics of temperature fronts mentioned above include: analyzing adjacent time spans ( ∇TThe temperature field distribution maps of (tᵢ₊1−tᵢ) are overlaid and compared; the temperature front is defined as the boundary of a region with a large rate of temperature change, and the maximum migration distance L of the front is used as the reference. max As a reference, generate the time-frontal displacement curve, and set... L i Let f(t) be the maximum distance the front migrates within the i-th time interval. Then the time-front displacement curve can be expressed as: L=f(t). By fitting the curve, a temperature field spatiotemporal evolution prediction model is established to predict the position and advancing speed of the temperature front at different times, thereby obtaining the temperature front advancing characteristics.

[0019] In the above, the well spacing constraint field is established as follows: cubic spline interpolation is performed on the temperature field variation distribution map to enhance spatial resolution. Cubic spline interpolation function. S ( x ) satisfies the condition in each interval [ xi , xi +1] is a cubic polynomial, and at the node xi Let it have a second continuous derivative. x 0 ，x 1 ，x 2 ⋯ x n For n nodes, y 0 ，y 1 ，y 2 ⋯ y n For the corresponding function values, the cubic spline interpolation function can be obtained by solving the following system of equations: ; Adaptive threshold binarization segmentation is used to extract contour lines of temperature distribution changes. For example, boundaries with ΔT≥5 are set as contour lines of temperature distribution changes to mark the cold front migration profile. A well spacing constraint field is constructed based on the geometric features of the cold front profile. The boundary equation of the constraint field is defined as follows: ; in, v max The maximum migration rate of the cold front (m / year). t critical The permitted safe mining period (in years). σ T α is the spatial variation coefficient of the temperature field, reflecting the degree of variation of the temperature field in space; α is the safety factor, with a value ranging from 1.2 to 1.5. ; Where N is the number of temperature sampling points, T i Let be the temperature at the i-th sampling point, T be the average temperature, and α be the safety factor, ranging from 1.2 to 1.5. The reliability of the constraint field boundary is verified by Monte Carlo simulation. Monte Carlo simulation generates a large number of temperature fields and cold front migration scenarios through random sampling, calculates the well spacing threshold under each scenario, generates a probability density distribution map, and thus determines the optimal well spacing threshold.

[0020] In the above, the method for determining the optimal well spacing threshold during mass production and irrigation development is as follows: map the constraint field boundary to the geographic coordinate system, use the Voronoi diagram algorithm to divide the production units, and ensure that the spacing between pumping and irrigation wells in each unit is greater than dmin; combine the anisotropy of geothermal reservoir permeability, adjust the well group layout to be radial or grid-like, so as to minimize the cold front interference area.

[0021] In some embodiments, the constraint field boundary is mapped to a geographic coordinate system, and the Voronoi diagram algorithm is used to divide the mining units. For a given number of pumping well locations... P 1, P 2,⋯, Pn A Voronoi diagram divides a plane into n regions. V 1, V 2,⋯, Vn This makes region V i Any point inside P i The distance is less than the distance to other points (P) j The distance (j≠i). Ensure the spacing between pumping and injection wells within each unit is greater than dmin. Adjust the well group layout according to the anisotropy of geothermal reservoir permeability, adjusting the well group layout to radial or grid-like. Let the permeability tensor be K, its expression in Cartesian coordinates is: ; The well cluster layout can be adjusted based on the principal direction and magnitude of the permeability tensor to minimize the cold front interference area. For example, when the permeability is large in a certain direction, the well cluster can be arranged radially along that direction to reduce the interference from reinjected cold water.

[0022] The above description is only a part of the embodiments of this application and does not limit the patent scope of this application. All equivalent structural transformations made under the technical concept of this application and using the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A method for developing hydrothermal geothermal mass extraction and irrigation, characterized in that, Includes the following steps: A three-dimensional unsteady temperature field distribution model under the one-sampling-one-irrigation mode is constructed; the baseline parameters are input, and the temperature field change distribution map is obtained through the three-dimensional unsteady temperature field distribution model; The temperature field change distribution map is subjected to several spline interpolation processes; after spline interpolation, adaptive threshold binarization segmentation is used to extract the temperature distribution change contour lines and mark the cold front migration profile. Obtain the geometric features of the cold front migration profile, and construct a well spacing constraint field based on the geometric features: Based on the well spacing constraint field, determine the probability density distribution map of the layout of mining wells and recharge wells during the development of mass mining and irrigation, thereby determining the optimal well spacing threshold during the development of mass mining and irrigation.

2. The method for developing hydrothermal geothermal mass extraction and irrigation according to claim 1, characterized in that, Methods for constructing a three-dimensional unsteady temperature field distribution model under a single-sampling-one-irrigation mode include: The recharge temperature, extraction / recharge water volume, formation thermal conductivity, and porosity of recharge wells and production wells under the one-production-one-injection mode in different regions were collected. The finite element method was used to perform time series simulation to generate temperature field distribution maps for different production periods. By overlaying and comparing temperature field distribution maps of adjacent time spans, the characteristics of temperature front advancement are extracted. Time-front displacement curves are generated based on the maximum front migration distance, and a three-dimensional unsteady temperature field distribution model is established to predict the spatiotemporal evolution of the temperature field.

3. The method for developing hydrothermal geothermal mass extraction and irrigation according to claim 2, characterized in that, Methods for time series simulation using the finite element method include: Obtain geothermal reservoir area exploration data, construct geothermal reservoir area model based on geothermal reservoir area exploration data, and set at least one set of pumping wells and reinjection wells in geothermal reservoir area model; Unsteady heat conduction-convection equations are constructed, and fluid flow and heat transfer are coupled to form the configuration of the physical field in the geothermal reservoir regional model; Configure the boundary conditions for pumping wells and reinjection wells to obtain the formation boundary conditions of the geothermal reservoir region model; set the time span and the maximum value of the time span; The geothermal reservoir area model is divided into several finite element units according to the time span, thereby generating temperature field distribution maps for different mining periods.

4. The method for developing hydrothermal geothermal mass extraction and irrigation according to claim 2, characterized in that, Methods for extracting the propulsion features of temperature fronts include: Overlay and compare temperature field distribution maps of adjacent time spans; define temperature fronts as the boundaries of regions with large temperature change rates, and generate time-frontal displacement curves based on the maximum frontal migration distance. By fitting the time-frontal displacement curve, a spatiotemporal evolution prediction model for the temperature field is established to predict the position and advancing speed of the temperature front at different times, thereby obtaining the advancing characteristics of the temperature front.

5. The method for developing hydrothermal geothermal mass extraction and irrigation according to claim 1, characterized in that, The well spacing constraint field is established as follows: Multiple spline interpolations were performed on the temperature field variation distribution map. Adaptive threshold binarization segmentation is used to extract temperature distribution change contour lines. Temperature reference values ​​are set as boundaries to obtain temperature distribution change contour lines and mark the cold front migration outline. A well spacing constraint field is constructed based on the geometric features of the cold front profile; the boundary equation of the constraint field is defined as follows: d min = v max × t critical +α⋅σ T； in, v max The maximum migration rate of the cold front (m / year). t critical The permitted safe mining period (in years). σ T α is the spatial variation coefficient of the temperature field, reflecting the degree of variation of the temperature field in space; α is the safety factor, with a value ranging from 1.2 to 1.

5.

6. The method for developing hydrothermal geothermal mass extraction and irrigation according to claim 1, characterized in that, The method for determining the optimal well spacing threshold during mass extraction and irrigation development is as follows: The constraint field boundary is mapped to the geographic coordinate system, and the Voronoi diagram algorithm is used to divide the mining units to ensure that the spacing between pumping and injection wells in each unit is greater than d_min. Taking into account the anisotropy of geothermal reservoir permeability, the well group layout is adjusted to be radial or grid-like to minimize the cold front interference area.

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