Method, device and medium for calculating heat breakthrough distance of geothermal well

Abstract

The application discloses a method, device, equipment and medium for calculating a thermal breakthrough distance of a geothermal well. The method can comprise: determining a to-be-corrected formula; determining an influencing factor of a correction coefficient according to heterogeneity, and then calculating the correction coefficient; applying the correction coefficient to the to-be-corrected formula to obtain a corrected formula; and calculating the thermal breakthrough distance according to the corrected formula. The application is based on a theoretical formula, and the correction coefficient is corrected according to heterogeneity, so that the corrected formula for calculating the thermal breakthrough distance is obtained, the degree of coincidence with the actual situation is higher, and the efficiency of development and utilization of a geothermal field is improved.

Description

Technical Field

[0001] This invention relates to the field of geothermal energy, and more specifically, to a method, apparatus, equipment, and medium for calculating the thermal breakthrough distance of geothermal wells. Background Technology

[0002] Geothermal energy, as a renewable and clean energy source, causes less environmental pollution compared to conventional energy sources, is beneficial to environmental protection, and features low investment and quick returns. It creates significant economic and social benefits in heating, bathing, and agricultural production. However, once geothermal water is extracted from deep rock strata, it cannot be replenished through natural rainfall as it rarely enters underground water storage. Excessive extraction of geothermal water inevitably creates gaps in water within and beneath rock strata, compromising land stability and potentially triggering earthquakes. Therefore, timely geothermal water reinjection is essential.

[0003] Geothermal water reinjection is a measure to avoid thermal and chemical pollution caused by the direct discharge of geothermal wastewater. It plays an important role in maintaining geothermal reservoir pressure and ensuring the technical conditions for geothermal field exploitation. However, due to differences in geological conditions and reinjection parameters, geothermal water reinjection can easily lead to thermal breakthrough, affecting the service life of geothermal wells. This necessitates selecting appropriate well spacing for different conditions.

[0004] Currently, commonly used methods for determining the distance between production and injection wells include numerical simulation and theoretical formula calculation. Numerical simulation involves model building and numerical simulation calculations, a complex and time-consuming process. The currently used theoretical methods fall into two categories: one considers only the heat exchange and seepage process between the reinjection water and the contacting rock, neglecting the role of the surrounding rock in heat exchange; the other calculates the distance between production and injection wells in homogeneous geothermal fields while considering overall heat exchange, ignoring the influence of heterogeneity on the thermal breakthrough distance.

[0005] Therefore, it is necessary to develop a method, device, equipment, and medium for calculating the thermal breakthrough distance of geothermal wells.

[0006] The information disclosed in the background section of this invention is intended only to enhance the understanding of the general background of this invention, and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] This invention proposes a method, device, equipment, and medium for calculating the thermal breakthrough distance of geothermal wells. Based on theoretical formulas, it performs coefficient corrections for heterogeneity to obtain a corrected formula for calculating the thermal breakthrough distance, which has a high degree of agreement with actual conditions and is conducive to improving the efficiency of geothermal field development and utilization.

[0008] In a first aspect, embodiments of this disclosure provide a method for calculating the thermal breakthrough distance for geothermal well extraction and injection, including:

[0009] Identify the formula to be corrected;

[0010] The factors influencing the correction coefficient are determined based on the heterogeneity, and then the correction coefficient is calculated.

[0011] The correction coefficient is applied to the formula to be corrected to obtain the corrected formula;

[0012] The thermal breakthrough distance is calculated based on the modified formula.

[0013] Preferably, the formula to be corrected is:

[0014]

[0015] Where D is the thermal breakthrough distance, Q is the produced water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

[0016] Preferably, the heterogeneity is characterized by permeability gradients, and the correction coefficient is calculated based on the permeability gradients.

[0017] Preferably, the permeability gradient is calculated according to formula (2):

[0018]

[0019] Where, N φ For permeability grade differences, φ max φ represents the maximum permeability within the layer. min This represents the minimum permeability within the layer.

[0020] Preferably, calculating the correction coefficient based on the permeability gradient includes:

[0021] Calculate the relationship between the effective thickness and the thermal breakthrough distance under different permeability ranges, and then plot the fitting curve;

[0022] Then, regression fitting is performed to obtain the expression for the correction coefficient.

[0023] Preferably, the correction coefficient is:

[0024]

[0025] Among them, D# N is the correction factor. φ For the penetration rate difference, These represent the permeability along the x and y directions on the plane, respectively.

[0026] Preferably, the correction formula is:

[0027]

[0028] Where D is the thermal breakthrough distance, D # Here, Q is the correction factor, Q is the extracted water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρW is the specific heat capacity of the rock, C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

[0029] As one specific implementation of this disclosure,

[0030] Secondly, this disclosure also provides a device for calculating the thermal breakthrough distance of geothermal wells, comprising:

[0031] The module for formula to be corrected has been determined; the formula to be corrected has been identified.

[0032] The correction coefficient calculation module determines the influencing factors of the correction coefficient based on the heterogeneity, and then calculates the correction coefficient.

[0033] The correction module applies the correction coefficient to the formula to be corrected to obtain the corrected formula.

[0034] The calculation module calculates the thermal breakthrough distance according to the modified formula.

[0035] Preferably, the formula to be corrected is:

[0036]

[0037] Where D is the thermal breakthrough distance, Q is the produced water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρW is the specific heat capacity of the rock, CW is the specific heat capacity of water, h is the effective thickness, and K is the density of the rock. R The thermal conductivity of the rock.

[0038] Preferably, the heterogeneity is characterized by permeability gradients, and the correction coefficient is calculated based on the permeability gradients.

[0039] Preferably, the permeability gradient is calculated according to formula (2):

[0040]

[0041] Where, N φ For permeability grade differences, φ max φ represents the maximum permeability within the layer. min This represents the minimum permeability within the layer.

[0042] Preferably, calculating the correction coefficient based on the permeability gradient includes:

[0043] Calculate the relationship between the effective thickness and the thermal breakthrough distance under different permeability ranges, and then plot the fitting curve;

[0044] Then, regression fitting is performed to obtain the expression for the correction coefficient.

[0045] Preferably, the correction coefficient is:

[0046]

[0047] Among them, D # N is the correction factor. φ For the penetration rate difference, These represent the permeability along the x and y directions on the plane, respectively.

[0048] Preferably, the correction formula is:

[0049]

[0050] Where D is the thermal breakthrough distance, D # Here, Q is the correction factor, Q is the extracted water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

[0051] Thirdly, embodiments of this disclosure also provide an electronic device, the electronic device comprising:

[0052] Memory, which stores executable instructions;

[0053] A processor that executes the executable instructions in the memory to implement the method for calculating the thermal breakthrough distance of geothermal wells.

[0054] Fourthly, embodiments of this disclosure also provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method for calculating the thermal breakthrough distance of geothermal well extraction and injection.

[0055] Its beneficial effects are as follows: This invention considers the actual physical properties of geothermal fields based on theory and obtains correction coefficients using least squares regression. In areas where numerical simulations have not been conducted, using the corrected formulas for calculations can reduce workload and dependence on numerical simulations while maintaining accuracy. It also overcomes the problems of limited applicability and low accuracy of theoretical formulas. Furthermore, it can assist in demonstrating the deployment of geothermal well networks and ensure the sustainable development of geothermal fields.

[0056] The methods and apparatus of the present invention have other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0057] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same parts.

[0058] Figure 1 A flowchart illustrating the steps of a method for calculating the thermal breakthrough distance for geothermal well extraction and injection according to an embodiment of the present invention is shown.

[0059] Figure 2 A schematic diagram comparing simulated and calculated thermal breakthrough distances at different effective thicknesses according to an embodiment of the present invention is shown.

[0060] Figure 3 A schematic diagram comparing simulated and calculated thermal breakthrough distances in different regions is shown according to an embodiment of the present invention.

[0061] Figure 4 A schematic diagram illustrating the relationship between the permeability range and the thermal breakthrough distance increment at different effective thicknesses according to an embodiment of the present invention is shown.

[0062] Figure 5 A schematic diagram illustrating the relationship between the permeability range for different permeability levels and the thermal breakthrough distance increment according to an embodiment of the present invention is shown.

[0063] Figure 6 A schematic diagram illustrating the relationship between effective thickness and thermal breakthrough distance increment under different permeability ranges according to an embodiment of the present invention is shown.

[0064] Figure 7 A schematic diagram illustrating the relationship between different permeability ranges and thermal breakthrough distance increments according to an embodiment of the present invention is shown.

[0065] Figure 8 A schematic diagram of the advance of the cold front of the reinjection water under different well spacing conditions according to an embodiment of the present invention is shown.

[0066] Figure 9 A schematic diagram comparing simulated and calculated thermal breakthrough distances in different regions is shown according to an embodiment of the present invention.

[0067] Figure 10 A schematic diagram showing the relative positions of wells 2 and 3 according to an embodiment of the present invention is shown.

[0068] Figure 11a , Figure 11b Schematic diagrams of temperature field distributions for evaluation periods of 41 years and 7 years, respectively, are shown according to an embodiment of the present invention.

[0069] Figure 12a , Figure 12b Schematic diagrams showing the relative positions of the intake and irrigation wells according to an embodiment of the present invention are shown.

[0070] Figure 13 A block diagram of a geothermal well extraction and injection thermal breakthrough distance calculation device according to an embodiment of the present invention is shown.

[0071] Explanation of reference numerals in the attached figures:

[0072] 201. Formula to be corrected module determined; 202. Correction coefficient calculation module; 203. Correction module; 204. Calculation module. Detailed Implementation

[0073] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0074] This invention provides a method for calculating the thermal breakthrough distance of geothermal wells, including:

[0075] Identify the formula to be corrected;

[0076] The factors influencing the correction coefficient are determined based on the heterogeneity, and then the correction coefficient is calculated.

[0077] The correction factor is applied to the formula to be corrected to obtain the corrected formula;

[0078] The thermal breakthrough distance is calculated using the modified formula.

[0079] In one example, the formula to be corrected is:

[0080]

[0081] Where D is the thermal breakthrough distance, Q is the produced water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

[0082] In one example, heterogeneity is characterized by permeability gradients, and a correction factor is calculated based on the permeability gradients.

[0083] In one example, the permeability gradient is calculated according to formula (2):

[0084]

[0085] Where, N φ For permeability grade differences, φ max φ represents the maximum permeability within the layer. min This represents the minimum permeability within the layer.

[0086] In one example, calculating the correction factor based on the permeability gradient includes:

[0087] The relationship between the increase factor of effective thickness and thermal breakthrough distance under different permeability ranges was calculated, and then the fitting curve was plotted.

[0088] Then, regression fitting is performed to obtain the expression for the correction coefficient.

[0089] In one example, the correction factor is:

[0090]

[0091] Among them, D # N is the correction factor. φ For the penetration rate difference, These represent the permeability along the x and y directions on the plane, respectively.

[0092] In one example, the corrected formula is:

[0093]

[0094] Where D is the thermal breakthrough distance, D # Here, Q is the correction factor, Q is the extracted water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

[0095] Specifically, we compare various methods for calculating well spacing to identify their advantages and disadvantages. The main methods currently used include: (1) numerical simulation calculation; and (2) theoretical calculation. The first method is complex but has high accuracy, while the second method is simple but currently only applicable to homogeneous thermal reservoirs. Combining the advantages of the two methods, we compare commonly used theoretical calculation formulas with the theoretical calculation formula for well spacing in homogeneous thermal reservoirs proposed by ACGringarten et al. We select the formula proposed by ACGringarten et al., which involves multi-field coupling, for modification, and determine the formula to be modified as formula (1). Since formula (1) comprehensively considers the coupling of three fields: seepage field, water flow temperature field, and rock temperature field, it provides a more comprehensive consideration of the liquid heat exchange environment.

[0096] Given that the derivation of formula (1) is based on homogeneous conditions, and considering that only the permeability changes in different directions among the three main physical property variables of porosity, effective thickness, and permeability calculated by simulation and formula, heterogeneity is considered to be the main factor causing the large differences. In order to apply formula (1) to production, formula (1) is modified from the aspects of heterogeneity.

[0097] Currently, the main quantitative parameters characterizing the degree of permeability heterogeneity include the coefficient of variation, the surge coefficient, and permeability gradient. Considering the directionality of heterogeneity, and to simplify the formula correction process, permeability gradient is chosen to characterize the permeability heterogeneity of rocks.

[0098] The correction coefficient is calculated based on the permeability difference as formula (3). The correction coefficient is applied to the formula to be corrected to obtain the corrected formula as formula (4). The thermal breakthrough distance is calculated based on the corrected formula.

[0099] This method is useful for calculating the minimum well spacing for geothermal production and irrigation, taking into account the planar heterogeneity of geothermal fields. It can accurately and quickly obtain the corresponding results, optimize the well network and well spacing deployment, and ensure the sustainable development of geothermal fields.

[0100] The present invention also provides a device for calculating the thermal breakthrough distance of geothermal well production and irrigation, comprising:

[0101] The module for formula to be corrected has been determined; the formula to be corrected has been identified.

[0102] The correction coefficient calculation module determines the influencing factors of the correction coefficient based on the heterogeneity, and then calculates the correction coefficient.

[0103] The correction module applies correction coefficients to the formula to be corrected to obtain the corrected formula.

[0104] The calculation module calculates the thermal breakthrough distance based on the modified formula.

[0105] In one example, the formula to be corrected is:

[0106]

[0107] Where D is the thermal breakthrough distance, Q is the produced water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

[0108] In one example, heterogeneity is characterized by permeability gradients, and a correction factor is calculated based on the permeability gradients.

[0109] In one example, the permeability gradient is calculated according to formula (2):

[0110]

[0111] Where, N φ For permeability grade differences, φ max φ represents the maximum permeability within the layer. min This represents the minimum permeability within the layer.

[0112] In one example, calculating the correction factor based on the permeability gradient includes:

[0113] The relationship between the increase factor of effective thickness and thermal breakthrough distance under different permeability ranges was calculated, and then the fitting curve was plotted.

[0114] Then, regression fitting is performed to obtain the expression for the correction coefficient.

[0115] In one example, the correction factor is:

[0116]

[0117] Among them, D # N is the correction factor. φ For the penetration rate difference, These represent the permeability along the x and y directions on the plane, respectively.

[0118] In one example, the corrected formula is:

[0119]

[0120] Where D is the thermal breakthrough distance, D # Here, Q is the correction factor, Q is the extracted water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

[0121] Specifically, we compare various methods for calculating well spacing to identify their advantages and disadvantages. The main methods currently used include: (1) numerical simulation calculation; and (2) theoretical calculation. The first method is complex but has high accuracy, while the second method is simple but currently only applicable to homogeneous thermal reservoirs. Combining the advantages of the two methods, we compare commonly used theoretical calculation formulas with the theoretical calculation formula for well spacing in homogeneous thermal reservoirs proposed by ACGringarten et al. We select the formula proposed by ACGringarten et al., which involves multi-field coupling, for modification, and determine the formula to be modified as formula (1). Since formula (1) comprehensively considers the coupling of three fields: seepage field, water flow temperature field, and rock temperature field, it provides a more comprehensive consideration of the liquid heat exchange environment.

[0122] Given that the derivation of formula (1) is based on homogeneous conditions, and considering that only the permeability changes in different directions among the three main physical property variables of porosity, effective thickness, and permeability calculated by simulation and formula, heterogeneity is considered to be the main factor causing the large differences. In order to apply formula (1) to production, formula (1) is modified from the aspects of heterogeneity.

[0123] Currently, the main quantitative parameters characterizing the degree of permeability heterogeneity include the coefficient of variation, the surge coefficient, and permeability gradient. Considering the directionality of heterogeneity, and to simplify the formula correction process, permeability gradient is chosen to characterize the permeability heterogeneity of rocks.

[0124] The correction coefficient is calculated based on the permeability difference as formula (3). The correction coefficient is applied to the formula to be corrected to obtain the corrected formula as formula (4). The thermal breakthrough distance is calculated based on the corrected formula.

[0125] The present invention also provides an electronic device, comprising: a memory storing executable instructions; and a processor that executes the executable instructions in the memory to implement the above-described method for calculating the thermal breakthrough distance of geothermal wells.

[0126] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for calculating the thermal breakthrough distance of geothermal well extraction and injection.

[0127] To facilitate understanding of the solutions and effects of the embodiments of the present invention, four specific application examples are given below. Those skilled in the art should understand that these examples are merely for the purpose of understanding the present invention, and any specific details therein are not intended to limit the present invention in any way.

[0128] Example 1

[0129] Figure 1 A flowchart illustrating the steps of a method for calculating the thermal breakthrough distance for geothermal well extraction and injection according to an embodiment of the present invention is shown.

[0130] like Figure 1 As shown, the method for calculating the thermal breakthrough distance of geothermal wells includes: step 101, determining the formula to be corrected; step 102, determining the influencing factors of the correction coefficient based on the heterogeneity, and then calculating the correction coefficient; step 103, applying the correction coefficient to the formula to be corrected to obtain the corrected formula; and step 104, calculating the thermal breakthrough distance based on the corrected formula.

[0131] We will use formula (1) as the formula to be corrected to verify the results with examples.

[0132] 1. Homogeneous layer

[0133] The parameters for calculating the thermal breakthrough distance are shown in Table 1.

[0134] Table 1

[0135]

[0136] Figure 2 A schematic diagram comparing simulated and calculated thermal breakthrough distances at different effective thicknesses according to an embodiment of the present invention is shown.

[0137] A numerical simulation model was established using the same geological characteristic parameters. By comparing the simulation results with the calculation results, it can be seen that the error varies between -48m and -21m as the effective thickness changes. The error value is less than the grid step size, so the calculated value is consistent with the actual value. Formula (1) is applicable to the calculation of the well distance of homogeneous formations.

[0138] 2. Actual stratigraphy

[0139] Table 1 shows the results of calculations using actual models from Lankao, Hekou, and other regions, with the results of calculations using theoretical formulas, while keeping the boundary conditions unchanged.

[0140] Figure 3 A schematic diagram comparing simulated and calculated thermal breakthrough distances in different regions is shown according to an embodiment of the present invention.

[0141] In practical applications, the calculated results differed from the actual thermal breakthrough distance by more than 50m (the length of a single grid in the geological model is 50m), exceeding the error range, indicating that formula (1) has poor applicability to actual conditions. Given that the formula derivation is based on homogeneous conditions, and considering that only permeability changes in different directions among the three main physical property variables of porosity, effective thickness, and permeability calculated by the simulation and formula, heterogeneity is considered to be the main factor causing the large difference. In order to apply formula (1) to production, formula (1) is modified from aspects such as heterogeneity.

[0142] Considering that the differences between calculated and actual values ​​are caused not only by heterogeneity (permeability gradients) but also by effective thickness and porosity, the parameters in Table 1 were used as initial conditions to verify the influence of porosity and effective thickness on the calculation results.

[0143] Figure 4 A schematic diagram illustrating the relationship between the permeability range and the thermal breakthrough distance increment at different effective thicknesses according to an embodiment of the present invention is shown.

[0144] Figure 5 A schematic diagram illustrating the relationship between the permeability range for different permeability levels and the thermal breakthrough distance increment according to an embodiment of the present invention is shown.

[0145] The increase in thermal breakthrough distance is basically the same with the increase of permeability grade difference when the effective thickness or porosity is different. Since the influence of thickness and porosity has been considered in formula (1), the main study is on the influence of planar heterogeneity on the correction coefficient.

[0146] Figure 6 A schematic diagram illustrating the relationship between effective thickness and thermal breakthrough distance increment under different permeability ranges according to an embodiment of the present invention is shown.

[0147] Figure 7 A schematic diagram illustrating the relationship between different permeability ranges and thermal breakthrough distance increments according to an embodiment of the present invention is shown.

[0148] when At the same thickness, as the permeability gradient increases, the thermal breakthrough distance increases by the same factor. During geothermal development, the reservoir planar gradient is generally within 100. Therefore, by using the relationship curve between the gradient and the average distance increase factor under different gradients (1-100), a correction coefficient expression is derived through regression, i.e. Similarly, calculate In the case of , the correction coefficient is obtained as formula (3), and then the correction formula is obtained as formula (4).

[0149] The thermal breakthrough distance was calculated using a modified formula, and the predicted results in the early stages of development were compared with the actual results as follows.

[0150] Figure 8 A schematic diagram of the advance of the cold front of the reinjection water under different well spacing conditions according to an embodiment of the present invention is shown.

[0151] Figure 9 A schematic diagram comparing simulated and calculated thermal breakthrough distances in different regions is shown according to an embodiment of the present invention.

[0152] Numerical simulation models were established using corresponding geological characteristic parameters from different regions. The initial conditions of the calculation formula corresponded to the characteristic parameters of different regions. Comparison of simulation and calculation results showed that the error between the simulated and actual calculated values ​​of reasonable well spacing for different regions was within 20m, indicating that the correction formula had high accuracy. The Hekou and Lankao areas consisted of sandstone thermal reservoirs, while the Taiyuan and Qingfeng areas consisted of limestone thermal reservoirs. The results demonstrate that the correction formula is highly adaptable to calculating well spacing for different types of thermal reservoirs.

[0153] The following is a comparison between the evaluation of thermal breakthroughs in production and injection wells during the development process and the actual situation.

[0154] Figure 10 A schematic diagram showing the relative positions of wells 2 and 3 according to an embodiment of the present invention is shown.

[0155] ① Evaluation of the applicability of the modified formula to sandstone, taking Changyuan Xinchang 2 and 3 wells as examples:

[0156] Production well: Xinchang 2 well, pumping capacity 31m³ 3 / h, temperature 47℃; Recharge well: Xinchang 3 well, recharge volume 31m 3 / h, the thermal breakthrough distance calculation parameters are shown in Table 2.

[0157] Table 2

[0158]

[0159] Figure 11a , Figure 11b Schematic diagrams of temperature field distributions for evaluation periods of 41 years and 7 years, respectively, are shown according to an embodiment of the present invention.

[0160] The calculation results of thermal breakthrough distance at different evaluation times are shown in Table 3.

[0161] Table 3

[0162]

[0163] During the 2017-18 heating season, when production and irrigation were balanced, the average reinjection volume per well was 31 m³. 3 / h. Xinchang 2 and 3 wells were reinjected with equal volume of fluid. When the evaluation period was 7 years, the difference between the calculated and simulated thermal breakthrough distances was within the error range (50m), with a thermal breakthrough distance of approximately 90m. When the thermal breakthrough distance was the same as the actual well spacing, the evaluation period was 41 years. Research showed that the water intake section of Xinchang 2 well was between 951.4m and 1270.3m, and the average geothermal gradient was 3.24℃ / 100m, as determined by the test water temperature. The top and bottom temperatures of the water intake section were 45.16℃ and 55.48℃, respectively. The top temperature was basically consistent with the temperature after the reduction, suggesting that sand burial caused the main producing layer to shift upwards, leading to the temperature reduction. Therefore, the temperature reduction in water production wells in the Changyuan area is unrelated to thermal breakthrough.

[0164] ② Evaluation of the applicability of the revised formula to limestone, taking some wells in Xiongxian County as examples:

[0165] Figure 12a , Figure 12b Schematic diagrams showing the relative positions of the intake and irrigation wells according to an embodiment of the present invention are shown.

[0166] Water intake stratum: Wumishan Formation, Jixian System; Production wells: Wangheying 1 and Hutai 1; Recharge wells: Wangkeqiao 1 and Hutai 2. Table 4 shows a comparison between the calculated thermal breakthrough distance parameters and the actual well spacing.

[0167] Table 4

[0168]

[0169] Two groups of production and injection wells with different well spacings were selected for verification. The thermal breakthrough distance of the Wangheying and Wangkeqiao production and injection wells was less than the current actual well spacing during the 100-year evaluation period. For the Hutai 1 and 2 production and injection wells, under current production conditions, the calculated well spacing was less than the actual well spacing, and thermal breakthrough had already occurred. The predicted results showed a high degree of agreement with the actual situation. In summary, the calculated results corresponded to the actual situation, indicating that the modified formula can be applied to limestone geothermal reservoirs.

[0170] This invention optimizes the value of the correction coefficient by comparing the calculated results with the numerical simulation results with high calculation accuracy based on the actual field conditions. Through the evaluation of thermal breakthroughs in geothermal wells of already operational projects, the predicted results show a high degree of agreement with the actual operating conditions, further confirming the rationality of the correction coefficient values.

[0171] Example 2

[0172] Figure 13 A block diagram of a geothermal well extraction and injection thermal breakthrough distance calculation device according to an embodiment of the present invention is shown.

[0173] like Figure 13As shown, the thermal breakthrough distance calculation device for geothermal well production and irrigation includes:

[0174] The module for formula to be corrected is identified as 201, indicating that the formula to be corrected has been determined.

[0175] The correction coefficient calculation module 202 determines the influencing factors of the correction coefficient based on the heterogeneity, and then calculates the correction coefficient.

[0176] The correction module 203 applies the correction coefficient to the formula to be corrected to obtain the corrected formula;

[0177] Calculation module 204 calculates the thermal breakthrough distance according to the modified formula.

[0178] As an alternative, the formula to be modified is:

[0179]

[0180] Where D is the thermal breakthrough distance, Q is the produced water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

[0181] As an alternative, heterogeneity can be characterized by permeability gradients, and a correction coefficient can be calculated based on the permeability gradients.

[0182] As an alternative, the permeability gradient can be calculated according to formula (2):

[0183]

[0184] Where, N φ For permeability grade differences, φ max φ represents the maximum permeability within the layer. min This represents the minimum permeability within the layer.

[0185] As an optional approach, the correction factor calculated based on the permeability gradient includes:

[0186] The relationship between the increase factor of effective thickness and thermal breakthrough distance under different permeability ranges was calculated, and then the fitting curve was plotted.

[0187] Then, regression fitting is performed to obtain the expression for the correction coefficient.

[0188] As an optional solution, the correction factor is:

[0189]

[0190] Among them, D # N is the correction factor. φ For the penetration rate difference, These represent the permeability along the x and y directions on the plane, respectively.

[0191] As an alternative, the revised formula is:

[0192]

[0193] Where D is the thermal breakthrough distance, D # Here, Q is the correction factor, Q is the extracted water volume (i.e., the reinjection water volume), and Δt is the evaluation time. Porosity, ρ R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

[0194] Example 3

[0195] This disclosure provides an electronic device comprising: a memory storing executable instructions; and a processor executing the executable instructions in the memory to implement the above-described method for calculating the thermal breakthrough distance of geothermal wells.

[0196] An electronic device according to an embodiment of the present disclosure includes a memory and a processor.

[0197] This memory is used to store non-transitory computer-readable instructions. Specifically, the memory may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may, for example, include random access memory (RAM) and / or cache memory. The non-volatile memory may, for example, include read-only memory (ROM), hard disk, flash memory, etc.

[0198] The processor may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions. In one embodiment of this disclosure, the processor is used to execute computer-readable instructions stored in the memory.

[0199] Those skilled in the art will understand that, in order to solve the technical problem of how to achieve a good user experience, this embodiment may also include well-known structures such as communication buses and interfaces, and these well-known structures should also be included within the protection scope of this disclosure.

[0200] For a detailed description of this embodiment, please refer to the corresponding descriptions in the foregoing embodiments, which will not be repeated here.

[0201] Example 4

[0202] This disclosure provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method for calculating the thermal breakthrough distance of geothermal well extraction and injection.

[0203] A computer-readable storage medium according to embodiments of the present disclosure stores non-transitory computer-readable instructions. When these non-transitory computer-readable instructions are executed by a processor, all or part of the steps of the methods described in the foregoing embodiments of the present disclosure are performed.

[0204] The aforementioned computer-readable storage media include, but are not limited to: optical storage media (e.g., CD-ROM and DVD), magneto-optical storage media (e.g., MO), magnetic storage media (e.g., magnetic tape or portable hard drive), media with built-in rewritable non-volatile memory (e.g., memory card), and media with built-in ROM (e.g., ROM cartridge).

[0205] Those skilled in the art should understand that the above description of the embodiments of the present invention is only intended to illustrate the beneficial effects of the embodiments of the present invention, and is not intended to limit the embodiments of the present invention to any of the examples given.

[0206] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for calculating the thermal breakthrough distance for geothermal well extraction and injection, characterized in that, include: Identify the formula to be corrected; The factors influencing the correction coefficient are determined based on the heterogeneity, and then the correction coefficient is calculated. The correction coefficient is applied to the formula to be corrected to obtain the corrected formula; Calculate the thermal breakthrough distance according to the modified formula; The heterogeneity is characterized by permeability gradients, and the correction coefficient is calculated based on the permeability gradients. The calculation of the correction coefficient based on the permeability difference includes: Calculate the relationship between the increase factor of the effective thickness and the thermal breakthrough distance under different permeability levels, and then plot the fitting curve; Then, regression fitting is performed to obtain the expression for the correction coefficient.

2. The method for calculating the thermal breakthrough distance for geothermal well extraction and irrigation according to claim 1, wherein, The formula to be corrected is: （1） Where D is the thermal breakthrough distance, Q is the produced water volume (i.e., the reinjection water volume), Δt is the evaluation time, Ø is the porosity, and ρ is the thermal breakthrough distance. R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

3. The method for calculating the thermal breakthrough distance for geothermal well extraction and injection according to claim 1, wherein, Calculate the permeability gradient according to formula (2): （2） in, For the penetration rate difference, The maximum permeability within the layer, This represents the minimum permeability within the layer.

4. The method for calculating the thermal breakthrough distance for geothermal well extraction and injection according to claim 1, wherein, The correction factor is: （3） in, For correction factor, For permeability levels, Ø x Ø y These represent the permeability along the x and y directions on the plane, respectively.

5. The method for calculating the thermal breakthrough distance for geothermal well extraction and injection according to claim 1, wherein, The corrected formula is: （4） Where D is the thermal breakthrough distance. Here, Q is the produced water volume (i.e., the reinjection water volume), Δt is the evaluation time, Ø is the porosity, and ρ is the correction factor. R C is the density of the rock. R ρ is the specific heat capacity of the rock. W C is the density of the rock. W Where is the specific heat capacity of water, h is the effective thickness, and K is the kJ / m³. R The thermal conductivity of the rock.

6. A device for calculating the thermal breakthrough distance of geothermal wells, characterized in that, include: The module for formula to be corrected has been determined; the formula to be corrected has been identified. The correction coefficient calculation module determines the influencing factors of the correction coefficient based on the heterogeneity, and then calculates the correction coefficient. The correction module applies the correction coefficient to the formula to be corrected to obtain the corrected formula. The calculation module calculates the thermal breakthrough distance according to the modified formula; The heterogeneity is characterized by the permeability gradient, and the correction coefficient is calculated based on the permeability gradient. The calculation of the correction coefficient based on the permeability difference includes: Calculate the relationship between the increase factor of the effective thickness and the thermal breakthrough distance under different permeability levels, and then plot the fitting curve; Then, regression fitting is performed to obtain the expression for the correction coefficient.

7. An electronic device, characterized in that, The electronic device includes: Memory, which stores executable instructions; A processor that executes the executable instructions in the memory to implement the method for calculating the thermal breakthrough distance of geothermal wells according to any one of claims 1-5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method for calculating the thermal breakthrough distance for geothermal well extraction and injection as described in any one of claims 1-5.

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