Geothermal transfer multi-field coupling and well cementation material thermal resistance effect analysis method

Abstract

The invention discloses a geothermal transfer multi-field coupling and well cementation material thermal resistance effect analysis method, belongs to the technical field of geothermal energy exploitation, and aims to solve the problem that a prediction result and an actual situation have large deviation due to the fact that the multi-field coupling effect is ignored in the heat transfer process of a geothermal well. A multi-physics field coupling method is introduced, the influence rule of multiple factors on single well heat taking is researched, the thermal conductivity of the well cementing material is analyzed, the thermal resistance effects of different materials in a geothermal well are qualitatively and quantitatively analyzed, and the thermal conductivity of the well cementing material is analyzed; through qualitative and quantitative analysis, the optimal well cementation material combination is selected, the design of the geothermal well is optimized, and a scientific basis is provided for well cementation material selection of the geothermal well; by optimizing the heat-conducting property of the well cementation material, the heat transfer efficiency of the geothermal well is remarkably improved, so that the single-well heat taking capacity is improved, and the energy waste is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of geothermal energy exploitation, and in particular relates to a method for analyzing multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials. Background Art

[0002] As a clean energy, geothermal energy is gaining increasing attention from all over the world. Geothermal energy is stored underground and is not affected by climatic conditions. It can be used as both base load energy and peak load energy. From the perspective of its development and utilization cost, geothermal energy has the characteristics of low cost, small land occupation and good stability, and has greater development potential than other renewable energy sources. Deep high-temperature geothermal resources suitable for power generation are widely distributed in southern Tibet, western Yunnan and western Sichuan in my country. Their development and utilization are of great significance to alleviating the global energy crisis, reducing greenhouse gas emissions and promoting sustainable development. However, the heat transfer process of geothermal wells is extremely complex, involving multiple aspects such as thermal conduction of rocks, convection heat transfer of geothermal fluids, heat exchange between wellbore and formation, and thermal resistance effect of cementing materials. These processes are not only intertwined, but also affected by multiple factors such as formation thermophysical properties, geothermal gradient, well depth, etc., making it difficult to accurately predict the heat transfer efficiency of geothermal wells and the heat extraction of a single well.

[0003] At present, although some progress has been made in the field of geothermal energy development, there are still many challenges in the study of the heat transfer process of geothermal wells. On the one hand, traditional heat transfer models often simplify the heat transfer process of geothermal wells and ignore the multi-field coupling effect, resulting in a large deviation between the predicted results and the actual situation. On the other hand, less attention is paid to the thermal resistance effect of cementing materials. The thermal conductivity of cementing materials in geothermal wells directly affects the efficiency of heat transfer from the formation to the wellbore, affecting the heat extraction efficiency and long-term operation stability of geothermal wells.

[0004] Therefore, a multi-field coupling analysis method for geothermal heat transfer and thermal resistance effect of cementing materials is needed to solve the problem that the heat transfer process of geothermal wells in the prior art ignores the multi-field coupling effect, resulting in a large deviation between the predicted results and the actual situation, and the thermal conductivity of cementing materials in geothermal wells directly affects the efficiency of heat transfer from the formation to the wellbore. Summary of the invention

[0005] The purpose of the present invention is to provide a method for analyzing the multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials to solve the problems raised in the above background technology.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a method for analyzing the multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials, including constructing a thermal fluid-solid coupling unsteady-state heat transfer model;

[0007] Introducing multi-physics field coupling method to study the influence of various factors on the heat extraction of a single well;

[0008] Analyze the thermal conductivity of cementing materials, and qualitatively and quantitatively analyze the thermal resistance effects of different materials in geothermal wells;

[0009] Based on qualitative and quantitative analysis, the influence of various factors on the heat extraction of a single well is explored.

[0010] It should be noted in the scheme that the construction of the thermal-fluid-solid coupled non-steady-state heat transfer model includes establishing the basic control equations of the temperature field, stress field and seepage field based on the mechanics of continuous media, heat conduction theory and fluid dynamics principles, and constructing a three-dimensional non-steady-state heat transfer model including the formation, wellbore, cementing material and well fluid.

[0011] The so-called thermal-fluid-solid coupling refers to the mutual influence between the three in a system composed of fluid, solid and changing temperature field. The interaction includes physical and chemical effects. The thermal-fluid-solid coupling problem is the basic problem when the three fields of seepage, stress and temperature exist at the same time. The thermal-fluid-solid coupling problem is not just to add a condition reflecting the temperature change to the fluid-solid coupling problem, but to regard the quantities reflecting the solid deformation and temperature field change of fluid flow, such as fluid pressure, solid phase particle displacement, and absolute temperature, as basic variables at the same time, and the basic variables are in an equal position. In the thermal-fluid-solid coupling problem, thermal effect and fluid pore pressure cause rock deformation, rock deformation and fluid seepage cause temperature field changes, rock deformation and thermal effect lead to changes in permeability characteristics and pore fluid pressure, thereby affecting fluid seepage. The above three effects occur simultaneously.

[0012] The temperature field equation takes into account heat conduction and convection heat transfer, describes the heat conduction process in the geothermal well, and takes into account the changes in the thermal properties of the formation (such as thermal conductivity, specific heat capacity, density, etc.). The stress field equation takes into account the elastic-plastic deformation of the rock and establishes a contact thermal resistance model between the cementing material and the formation based on the mechanical properties of the formation. The seepage field equation considers the influence of fluid flow in the wellbore on heat transfer, combining the flow characteristics of the geothermal fluid and the heat exchange efficiency.

[0013] It is worth noting that the multi-physics field coupling method is introduced to study the influence of various factors on the heat extraction of a single well, including:

[0014] Introducing multi-field coupling terms into the basic control equations, such as the effect of temperature on stress field, the effect of stress on seepage field, and the effect of seepage on temperature field. The above coupling terms are described by corresponding physical laws and mathematical models, such as the thermoelasticity equation, the relationship between permeability and stress, and the energy equation of fluid flow.

[0015] According to the actual situation of the geothermal well, determine the boundary conditions of the model, such as the temperature and pressure distribution of the formation boundary, the heat flux density and fluid flow rate of the wellbore wall, etc.; set reasonable initial conditions, such as the initial temperature distribution of the formation and wellbore, the initial velocity and pressure of the fluid, etc.;

[0016] The coupled heat-fluid-solid problem is discretized by using the element analysis method. The influence of formation temperature, thermal conductivity, wellbore thermal resistance, fluid flow rate, wellbore heat conduction, wellbore thermal expansion, heat exchange between solid and fluid and other factors on the heat extraction of a single well are analyzed through numerical simulation results.

[0017] It should be further explained that the analysis of the thermal conductivity of cementing materials and the qualitative and quantitative analysis of the thermal resistance effects of different materials in geothermal wells include:

[0018] Qualitative analysis of the thermal conductivity of cementing materials was conducted to explore the thermal resistance effects of different materials in geothermal wells;

[0019] The thermal resistance effect of cementing materials is mainly reflected in the following aspects:

[0020] Low thermal conductivity: Materials with low thermal conductivity (such as certain special cements) will result in slower heat flow, limiting heat exchange between the wellbore wall and the formation.

[0021] Contact thermal resistance: There is thermal resistance at the contact surface between the cementing material and the well wall or formation, which affects the heat transfer efficiency.

[0022] Thermal expansion effect: The expansion of cementing materials due to temperature changes may change the shape of the contact surface, thereby changing the thermal resistance effect.

[0023] By comparing with factors such as formation temperature gradient, well depth, and cementing material thickness, the heat transfer efficiency of cementing materials under different working conditions is quantitatively analyzed.

[0024] As a preferred embodiment, the quantitative analysis of the heat transfer efficiency of cementing materials under different working conditions includes introducing the heat conduction equation when quantitatively analyzing the thermal resistance of the cementing material.

[0025]

[0026] Where T is temperature, t is time, and α is the thermal diffusion coefficient, which reflects the diffusion capacity of the material to thermal disturbance; is the second derivative of temperature, that is, the rate of change of temperature gradient, which represents the driving force of heat conduction;

[0027] For cementing materials, the thermal resistance can be expressed by the thermal conductivity (λ) and the thickness (L) of the material. If the thermal conductivity of the cementing layer is different from that of the formation, the thermal conductivity formula is:

[0028]

[0029] Among them, R is the thermal resistance, L is the thickness of the cementing material, and t is the thermal conductivity of the cementing material, which reflects the ability of the material to conduct heat.

[0030] For the problem of underground heat extraction, heat conduction analysis can be used to explore the heat transfer efficiency. The increase in thermal resistance of cementing materials will lead to a decrease in heat flux density, thus affecting the amount of heat extracted from the well.

[0031] Due to the influence of thermal resistance of cementing materials, the temperature difference between the wellbore wall and the formation will affect the heat transfer rate. A larger thermal resistance leads to a lower heat flow rate.

[0032] The heat extraction is quantitatively calculated according to the heat flow equation, and the change of heat extraction in a single well is obtained. The heat flow rate (Q) can be calculated by the following formula:

[0033]

[0034] Among them, Q is the heat flow, T1 and T2 are the temperatures in the well and the formation respectively, and R is the thermal resistance.

[0035] As a preferred implementation mode, the exploration of the influence of multiple factors on the heat extraction of a single well based on qualitative and quantitative analysis includes combining the above-mentioned numerical simulation to explore the influence of factors such as formation thermal properties, geothermal gradient, well depth and thermal conductivity of cementing materials on the heat extraction of a single well; based on the influence rules, a strategy for optimizing the thermal conductivity of cementing materials under different working conditions is proposed to improve the heat extraction of a single well in geothermal wells.

[0036] Compared with the prior art, the multi-field coupling of geothermal heat transfer and the thermal resistance effect analysis method of cementing materials provided by the present invention have at least the following beneficial effects:

[0037] Through qualitative and quantitative analysis, the best cementing material combination is selected, the design of geothermal wells is optimized, and a scientific basis is provided for the selection of cementing materials for geothermal wells; by optimizing the thermal conductivity of cementing materials, the heat transfer efficiency of geothermal wells is significantly improved, thereby increasing the heat extraction of a single well and reducing energy waste; through the heat-flux-solid coupled non-steady-state heat transfer model, a comprehensive analysis of the coupling effects between multiple physical fields is carried out to help more accurately predict and evaluate the heat transfer performance of geothermal wells; this method is suitable for the analysis of heat flow transfer processes in medium-deep geothermal wells, and can adapt to the working conditions of different formations, different well depths, and different cementing materials, and has strong engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic flow chart of the multi-field coupling of geothermal heat transfer and the thermal resistance effect analysis method of cementing materials of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the embodiments.

[0040] Reference Figure 1 As shown, the present invention provides a method for analyzing the multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials, comprising:

[0041] Construct a thermal-fluid-solid coupling unsteady-state heat transfer model;

[0042] Introducing multi-physics field coupling method to study the influence of various factors on the heat extraction of a single well;

[0043] Analyze the thermal conductivity of cementing materials, and qualitatively and quantitatively analyze the thermal resistance effects of different materials in geothermal wells;

[0044] Based on qualitative and quantitative analysis, the influence of various factors on the heat extraction of a single well is explored.

[0045] It can be understood that the construction of the thermal-fluid-solid coupled unsteady-state heat transfer model includes establishing the basic control equations of the temperature field, stress field and seepage field based on the principles of continuous medium mechanics, heat conduction theory and fluid dynamics, and constructing a three-dimensional unsteady-state heat transfer model including the formation, wellbore, cementing material and well fluid.

[0046] Specifically, the so-called thermal-fluid-solid coupling refers to the mutual influence between the three in a system composed of fluid, solid and changing temperature field. The interaction includes physical and chemical effects. The thermal-fluid-solid coupling problem is the basic problem when the three fields of seepage, stress and temperature exist at the same time. The thermal-fluid-solid coupling problem is not just to add a condition reflecting the temperature change to the fluid-solid coupling problem, but to regard the quantities reflecting the solid deformation and temperature field change of fluid flow, such as fluid pressure, solid phase particle displacement, and absolute temperature, as basic variables at the same time, and the basic variables are in an equal position. In the thermal-fluid-solid coupling problem, thermal effect and fluid pore pressure cause rock deformation, rock deformation and fluid seepage cause temperature field changes, rock deformation and thermal effect lead to changes in permeability characteristics and pore fluid pressure, thereby affecting fluid seepage. The above three effects occur simultaneously.

[0047] The temperature field equation takes into account heat conduction and convection heat transfer, describes the heat conduction process in the geothermal well, and takes into account the changes in the thermal properties of the formation (such as thermal conductivity, specific heat capacity, density, etc.). The stress field equation takes into account the elastic-plastic deformation of the rock and establishes a contact thermal resistance model between the cementing material and the formation based on the mechanical properties of the formation. The seepage field equation considers the influence of fluid flow in the wellbore on heat transfer, combining the flow characteristics of the geothermal fluid and the heat exchange efficiency.

[0048] Temperature field control equation: Using Fourier's law, the expression formula is:

[0049] q=-kA(ΔT / Δx)

[0050] Among them, q is the amount of heat conducted through a given cross section per unit time, also known as heat flux density; k is thermal conductivity, which represents the thermal conductivity of the material; A is the cross-sectional area perpendicular to the direction of heat flow; ΔT / Δx is the rate of temperature change perpendicular to the cross-sectional direction, that is, the temperature gradient; the negative sign indicates that the direction of heat transfer is opposite to the direction of temperature increase.

[0051] Fourier's law reveals the relationship between heat transfer and temperature gradient. In the process of heat conduction, heat always flows from high temperature area to low temperature area, and the transfer rate is proportional to the temperature gradient.

[0052] Stress field control equation: describes the interaction between cementing materials and formations, using elastic mechanics equations, expressed as

[0053] σ ij,j +f i =0

[0054] Among them, σ ij is the stress tensor, f i is an external force (such as formation pressure), and the comma indicates the partial derivative with respect to the corresponding coordinates.

[0055] Seepage field control equation: The Navier-Stokes equation is used to describe the movement and heat exchange of the fluid, and the expression formula is

[0056]

[0057] Where ρ is the fluid density, u is the fluid velocity vector, p is the pressure, μ is the dynamic viscosity, g is the gravitational acceleration, F is the body force (such as electromagnetic force, etc., which is zero if it does not exist), is the gradient operator, is the Laplace operator, which, for a vector field, acts on each component.

[0058] It can be understood that the multi-physics field coupling method is introduced to study the influence of various factors on the heat extraction of a single well, including:

[0059] Introducing multi-field coupling terms into the basic control equations, such as the effect of temperature on stress field, the effect of stress on seepage field, and the effect of seepage on temperature field. The above coupling terms are described by corresponding physical laws and mathematical models, such as the thermoelasticity equation, the relationship between permeability and stress, and the energy equation of fluid flow.

[0060] According to the actual situation of the geothermal well, determine the boundary conditions of the model, such as the temperature and pressure distribution of the formation boundary, the heat flux density and fluid flow rate of the wellbore wall, etc.; set reasonable initial conditions, such as the initial temperature distribution of the formation and wellbore, the initial velocity and pressure of the fluid, etc.;

[0061] The coupled heat-fluid-solid equations are discretized using the element analysis method, and the influence of factors such as formation temperature, thermal conductivity, wellbore thermal resistance, fluid flow rate, wellbore heat conduction, wellbore thermal expansion, and heat exchange between solid and fluid on the heat extraction of a single well is analyzed through numerical simulation results.

[0062] The finite element method (FEM) is a numerical method widely used to solve complex physical problems, especially for engineering problems with complex geometries and boundary conditions. In the thermal-fluid-solid coupling problem, FEM approximates the coupling equations of multiple physical fields such as heat conduction equations, fluid dynamics equations, and stress equations by dividing the continuum into small finite elements.

[0063] Discretize the above control equations into finite element form. Taking the heat conduction equation as an example, the following time and space discretization methods can be used:

[0064] Approximate the temperature field in space by dividing the model into a finite number of elements, such as tetrahedrons or hexahedrons. This step usually uses shape functions to express the continuous solution as a linear combination of node values;

[0065] For non-stationary problems, explicit or implicit time-stepping methods (such as forward Euler method or backward Euler method) are used for time discretization.

[0066] Through this discretization method, we can transform physical problems into a series of linear or nonlinear algebraic equations and solve them using numerical methods.

[0067] For coupling problems, we need to consider the interaction between different physical fields. Common coupling methods include thermal-fluid-solid coupling, thermal-fluid coupling, etc. In FEM, coupling is performed in the following ways:

[0068] Thermal-fluid-solid coupling: There is an interaction between heat conduction and thermal expansion. Temperature changes cause solid expansion, which in turn affects the heat flow path and heat conduction speed.

[0069] Thermal-fluid coupling: The flow rate of the fluid in the well affects the heat transfer because the fluid's heat capacity, flow rate, and heat exchange with solids will change the temperature distribution in the wellbore and surrounding formations.

[0070] Heat exchange coupling: The heat exchange effect between solid and fluid is usually described by boundary conditions.

[0071] It is understandable that the analysis of the thermal conductivity of cementing materials and the qualitative and quantitative analysis of the thermal resistance effects of different materials in geothermal wells include:

[0072] Qualitative analysis of the thermal conductivity of cementing materials was conducted to explore the thermal resistance effects of different materials in geothermal wells;

[0073] The thermal resistance effect of cementing materials is mainly reflected in the following aspects:

[0074] Low thermal conductivity: Materials with low thermal conductivity (such as certain special cements) will result in slower heat flow, limiting heat exchange between the wellbore wall and the formation.

[0075] Contact thermal resistance: There is thermal resistance at the contact surface between the cementing material and the well wall or formation, which affects the heat transfer efficiency.

[0076] Thermal expansion effect: The expansion of cementing materials due to temperature changes may change the shape of the contact surface, thereby changing the thermal resistance effect.

[0077] By comparing with factors such as formation temperature gradient, well depth, and cementing material thickness, the heat transfer efficiency of cementing materials under different working conditions is quantitatively analyzed.

[0078] It is understandable that the quantitative analysis of the heat transfer efficiency of cementing materials under different working conditions includes introducing the heat conduction equation when quantitatively analyzing the thermal resistance of the cementing materials.

[0079]

[0080] Where T is temperature, t is time, and α is the thermal diffusion coefficient, which reflects the diffusion capacity of the material to thermal disturbance; is the second derivative of temperature, that is, the rate of change of temperature gradient, which represents the driving force of heat conduction;

[0081] For cementing materials, the thermal resistance can be expressed by the thermal conductivity (λ) and the thickness (L) of the material. If the thermal conductivity of the cementing layer is different from that of the formation, the thermal conductivity formula is:

[0082]

[0083] Among them, R is the thermal resistance, L is the thickness of the cementing material, and t is the thermal conductivity of the cementing material, which reflects the ability of the material to conduct heat.

[0084] For the problem of underground heat extraction, heat conduction analysis can be used to explore the heat transfer efficiency. The increase in thermal resistance of cementing materials will lead to a decrease in heat flux density, thus affecting the amount of heat extracted from the well.

[0085] Due to the influence of thermal resistance of cementing materials, the temperature difference between the wellbore wall and the formation will affect the heat transfer rate. A larger thermal resistance leads to a lower heat flow rate.

[0086] The heat extraction is quantitatively calculated according to the heat flow equation, and the change of heat extraction in a single well is obtained. The heat flow rate (Q) can be calculated by the following formula:

[0087]

[0088] Among them, Q is the heat flow, T1 and T2 are the temperatures in the well and the formation respectively, and R is the thermal resistance.

[0089] The method based on qualitative and quantitative analysis explores the influence of various factors on the heat extraction of a single well, including combining the above numerical simulation to explore the influence of factors such as formation thermal properties, geothermal gradient, well depth and thermal conductivity of cementing materials on the heat extraction of a single well; based on the influence rules, a strategy for optimizing the thermal conductivity of cementing materials under different working conditions is proposed to improve the heat extraction of a single well in geothermal wells.

[0090] In summary, the advantages of the present invention are: through qualitative and quantitative analysis, the best cementing material combination is selected, the design of geothermal wells is optimized, and a scientific basis is provided for the selection of cementing materials for geothermal wells; by optimizing the thermal conductivity of cementing materials, the heat transfer efficiency of geothermal wells is significantly improved, thereby increasing the heat extraction of a single well and reducing energy waste; through the heat flow-solid coupled non-steady-state heat transfer model, the coupling effect between multiple physical fields is comprehensively analyzed, which helps to more accurately predict and evaluate the heat transfer performance of geothermal wells; this method is suitable for the analysis of heat flow transfer processes in medium and deep geothermal wells, can adapt to the working conditions of different formations, different well depths, and different cementing materials, and has a strong engineering application value.

[0091] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for analyzing the multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials, characterized in that: include: Construct a thermal-fluid-solid coupling unsteady-state heat transfer model; Introducing multi-physics field coupling method to study the influence of various factors on the heat extraction of a single well; Analyze the thermal conductivity of cementing materials, and qualitatively and quantitatively analyze the thermal resistance effects of different materials in geothermal wells; Based on qualitative and quantitative analysis, the influence of various factors on the heat extraction of a single well is explored.

2. The method for analyzing the multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials according to claim 1, characterized in that: The construction of the thermal-fluid-solid coupled unsteady-state heat transfer model includes establishing basic control equations of temperature field, stress field and seepage field based on continuous medium mechanics, heat conduction theory and fluid dynamics principles, and constructing a three-dimensional unsteady-state heat transfer model including formations, wellbores, cementing materials and fluids in the well.

3. The method for analyzing the multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials according to claim 2 is characterized in that: The multi-physics field coupling method is introduced to study the influence of various factors on the heat extraction of a single well, including: Introducing multi-field coupling terms into the basic control equations, such as the effect of temperature on stress field, the effect of stress on seepage field, and the effect of seepage on temperature field. The above coupling terms are described by corresponding physical laws and mathematical models. Determine the boundary conditions of the model based on the actual situation of the geothermal well; The coupled heat-fluid-solid equations are discretized using the element analysis method, and the influence of factors such as formation temperature, thermal conductivity, wellbore thermal resistance, fluid flow rate, wellbore heat conduction, wellbore thermal expansion, and heat exchange between solid and fluid on the heat extraction of a single well is analyzed through numerical simulation results.

4. The method for analyzing the multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials according to claim 3 is characterized in that: The analysis of the thermal conductivity of cementing materials and the qualitative and quantitative analysis of the thermal resistance effects of different materials in geothermal wells include: Qualitative analysis of the thermal conductivity of cementing materials was conducted to explore the thermal resistance effects of different materials in geothermal wells; By comparing with factors such as formation temperature gradient, well depth, and cementing material thickness, the heat transfer efficiency of cementing materials under different working conditions is quantitatively analyzed.

5. The method for analyzing the multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials according to claim 4, characterized in that: The quantitative analysis of the heat transfer efficiency of cementing materials under different working conditions includes introducing the heat conduction equation when quantitatively analyzing the thermal resistance of the cementing materials. Where T is temperature, t is time, and α is the thermal diffusion coefficient, which reflects the diffusion capacity of the material to thermal disturbance; 2 T is the second derivative of temperature, that is, the rate of change of temperature gradient, which represents the driving force of heat conduction; For cementing materials, the thermal resistance can be expressed by the thermal conductivity (λ) and the thickness (L) of the material. If the thermal conductivity of the cementing layer is different from that of the formation, the thermal conductivity formula is: Among them, R is the thermal resistance, L is the thickness of the cementing material, and t is the thermal conductivity of the cementing material, which reflects the ability of the material to conduct heat. The heat extraction is quantitatively calculated according to the heat flow equation, and the change of heat extraction in a single well is obtained. The heat flow rate (Q) can be calculated by the following formula: Among them, Q is the heat flow, T1 and T2 are the temperatures in the well and the formation respectively, and R is the thermal resistance.

6. The method for analyzing the multi-field coupling of geothermal heat transfer and thermal resistance effect of cementing materials according to claim 5, characterized in that: The method based on qualitative and quantitative analysis explores the influence of various factors on the heat extraction of a single well, including combining the above numerical simulation to explore the influence of factors such as formation thermal properties, geothermal gradient, well depth and thermal conductivity of cementing materials on the heat extraction of a single well; based on the influence rules, a strategy for optimizing the thermal conductivity of cementing materials under different working conditions is proposed to improve the heat extraction of a single well in geothermal wells.

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