A method for inversion of heat transfer parameters in fractured aquifers considering wellbore thermal mixing process

Abstract

The present invention relates to the technical field of geothermal resource assessment, and discloses a method for inverting heat transfer parameters of a fractured aquifer considering a wellbore thermal mixing process, the method comprising: conducting a three-stage single-well injection and pumping test based on target area drilling data and target area hydrogeological data to determine the influencing parameters of the wellbore thermal mixing process; constructing a single-well injection and pumping test mathematical model considering the wellbore thermal mixing process based on the influencing parameters of the wellbore thermal mixing process; solving the single-well injection and pumping test mathematical model considering the wellbore thermal mixing process to generate a three-stage single-well injection and pumping test analytical solution; constructing an optimization objective function based on the three-stage single-well injection and pumping test analytical solution, and using the optimization objective function to perform parameter inversion to generate a heat transfer parameter value of a target fractured aquifer; wherein the heat transfer parameter value of the target fractured aquifer is used to assess geothermal resources. The present invention improves the inversion accuracy and calculation efficiency of geothermal transfer parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of geothermal resource assessment, and in particular to a method for inverting heat transfer parameters of a fractured aquifer taking into account a wellbore thermal mixing process. Background Art

[0002] With the rapid development of the economy, the consumption of fossil energy is increasing, and environmental problems are becoming more and more prominent. At this stage, it is urgent to seek an alternative energy source to alleviate the dual pressure of energy and environment, especially after the "dual carbon" goal is proposed. Geothermal energy mainly comes from the heat generated inside the earth. It has the characteristics of large reserves, little impact on weather changes, good stability, wide distribution range, and its development and utilization will not directly emit carbon dioxide. At the same time, geothermal energy is a renewable clean energy with multiple functions and wide uses. It can not only be used for heating and power generation, but also a precious medical hot mineral water resource. It has great market potential and broad development prospects. The development and utilization of geothermal resources has and will surely occupy a place in the world's new energy map. Fracture aquifers are the main storage space for deep geothermal heat. Heat transfer parameters are the basic parameters for evaluating the mining potential and development and utilization efficiency of geothermal resources. Therefore, the accuracy of the inverse parameters is very important.

[0003] However, the accuracy of the relevant heat transfer parameter inversion methods is low, which in turn reduces the mining potential and development and utilization efficiency of geothermal resources. Summary of the invention

[0004] In view of this, the present invention provides a method for inverting heat transfer parameters of fractured aquifers taking into account the thermal mixing process of the wellbore, so as to solve the problem that the accuracy of related heat transfer parameter inversion methods is low, thereby reducing the mining potential and development and utilization efficiency of geothermal resources.

[0005] In a first aspect, the present invention provides a method for inverting heat transport parameters of a fractured aquifer considering a wellbore thermal mixing process, the method comprising:

[0006] Obtain the target area drilling data and target area hydrogeological data, carry out a three-stage single well injection and pumping test based on the target area drilling data and target area hydrogeological data, and determine the influencing parameters of the wellbore thermal mixing process;

[0007] Based on the influencing parameters of the wellbore thermal mixing process, a mathematical model for single-well injection and pumping test considering the wellbore thermal mixing process is constructed;

[0008] The mathematical model of the single-well injection and pumping test considering the wellbore thermal mixing process is solved to generate the analytical solution of the three-stage single-well injection and pumping test;

[0009] Based on the analytical solution of the three-stage single-well injection and pumping test, an optimization objective function is constructed, and parameter inversion is performed using the optimization objective function to generate the heat transfer parameter values ​​of the target fractured aquifer; among them, the heat transfer parameter values ​​of the target fractured aquifer are used to evaluate geothermal resources.

[0010] The present embodiment provides a method for inverting heat transfer parameters in a fractured aquifer taking into account the thermal mixing process of the wellbore. The method takes into account the thermal mixing process of the wellbore by constructing a mathematical model of a single-well injection and pumping test taking into account the thermal mixing process of the wellbore, and solves the mathematical model of the single-well injection and pumping test taking into account the thermal mixing process of the wellbore, thereby generating an analytical solution of the three-stage single-well injection and pumping test. Furthermore, an optimization objective function is constructed based on the analytical solution of the three-stage single-well injection and pumping test, which can be used to invert and set key parameters in the heat transfer model in a fractured aquifer, can solve the problem of parameter identification in the numerical simulation process of heat transfer in a fractured aquifer, improves the accuracy and calculation efficiency of parameter inversion, and can provide technical support for the spatial distribution evaluation of geothermal resources and the efficient development of geothermal resources.

[0011] In an optional implementation, a three-stage single-well injection and pumping test is carried out based on the target area drilling data and the target area hydrogeological data to determine the influencing parameters of the wellbore thermal mixing process, including:

[0012] Determine the target fractured aquifer and geothermal injection wells based on the target area drilling data and target area hydrogeological data;

[0013] Measure the target fractured aquifer and geothermal injection well to determine the bedrock thickness and wellbore radius;

[0014] obtaining the lithology of the target fractured aquifer, and determining the range of geothermal heat transport parameters based on the lithology of the target fractured aquifer;

[0015] The temperature of the target fractured aquifer is obtained, and based on the temperature of the target fractured aquifer, a three-stage single-well injection and pumping test is carried out to determine the injection flow rate, pumping flow rate, liquid volume in the geothermal injection well, temperature in the geothermal injection well and temperature of the injected water body; wherein, the three-stage single-well injection and pumping test includes single-well injection and pumping tests in injection stage, rest stage and pumping stage.

[0016] This embodiment provides a method for inverting the heat transfer parameters of a fractured aquifer taking into account the thermal mixing process of the wellbore. By calculating the relevant data of the target fractured aquifer and the geothermal injection well, the influencing parameters of the thermal mixing process of the wellbore are determined, which lays a foundation for the subsequent mathematical model of single-well injection and pumping tests taking into account the thermal mixing process of the wellbore, and lays a foundation for the accuracy judgment of the heat transfer parameter value of the target fractured aquifer generated by subsequent inversion through the range of geothermal transfer parameters.

[0017] In an optional embodiment, the geothermal heat transfer parameter in the range of geothermal heat transfer parameters includes:

[0018] Volumetric specific heat capacity of bedrock medium, thermal conductivity coefficient of bedrock medium, volumetric specific heat capacity of target fractured aquifer, porosity of target fractured aquifer, thermal diffusion of target fractured aquifer, width of target fractured aquifer, thermal conductivity coefficient of target fractured aquifer, volumetric specific heat capacity of water.

[0019] This embodiment provides a method for inverting heat transfer parameters in a fractured aquifer taking into account the thermal mixing process in the wellbore. By inverting key parameters of heat transfer, such as the thermal expansion conductivity coefficient and the thermal diffusion coefficient, the problem of parameter identification in the numerical simulation process of heat transfer is solved.

[0020] In an optional embodiment, a mathematical model of a single-well injection and pumping test considering the wellbore thermal mixing process is constructed based on the influencing parameters of the wellbore thermal mixing process, including:

[0021] Based on the influencing parameters of the wellbore thermal mixing process, the injection stage mixing effect model, the rest stage mixing effect model and the extraction stage mixing effect model are constructed respectively;

[0022] The control equation is constructed based on the influencing parameters of the wellbore thermal mixing process; wherein the control equation includes the thermal transfer kinetic equation of the fracture medium and the thermal transfer kinetic equation of the bedrock medium;

[0023] Determine initial and boundary conditions based on the influencing parameters of the wellbore thermal mixing process;

[0024] Determine the effective thermal diffusion coefficient based on the influencing parameters of the wellbore thermal mixing process;

[0025] A mathematical model of single-well injection and extraction test considering the wellbore thermal mixing process is constructed based on the heat transfer kinetic equation, initial conditions, boundary conditions, effective thermal diffusion coefficient, injection stage mixing effect model, rest stage mixing effect model and extraction stage mixing effect model.

[0026] This embodiment provides a method for inverting heat transfer parameters in a fractured aquifer taking into account the thermal mixing process in the wellbore. The existing analytical solution models for three-stage single-well injection and pumping geothermal transfer all assume that the geothermal diffusion process is linearly related to the flow rate. This assumption often violates the actual physical laws. This embodiment takes into account the nonlinearity between heat diffusion and flow rate in the process of constructing a mathematical model of a single-well injection and pumping test taking into account the thermal mixing process in the wellbore, thereby improving the simulation capability of the heat transfer process in the fractured aquifer and the accuracy of the inversion of heat transfer parameters.

[0027] In an optional embodiment, based on the influencing parameters of the wellbore thermal mixing process, a mixed effect model of the injection phase, a mixed effect model of the rest phase, and a mixed effect model of the extraction phase are respectively constructed, including:

[0028] A mixed effect model for the injection phase is constructed based on the volumetric specific heat capacity of water, the liquid volume in the geothermal injection well during the injection phase, the temperature in the geothermal injection well, the injection flow rate, and the temperature of the injected water body.

[0029] A rest phase mixed effects model is constructed based on the temperature in the geothermal injection well and the temperature of the target fractured aquifer;

[0030] A mixed effect model for the extraction phase was constructed based on the pumping flow rate, volumetric specific heat capacity of water, liquid volume in the geothermal injection well during the extraction phase, temperature in the geothermal injection well, width of the target fractured aquifer, bedrock thickness, thermal conductivity of the target fractured aquifer, and temperature of the target fractured aquifer.

[0031] This embodiment provides a method for inverting heat transfer parameters in a fractured aquifer taking into account the thermal mixing process in the wellbore. By constructing a mixed effect model for the injection stage, a mixed effect model for the rest stage, and a mixed effect model for the extraction stage, a corresponding model is constructed for each stage of the single-well injection and extraction test, thereby improving the simulation capability of the heat transfer process in the target fractured aquifer.

[0032] In an optional embodiment, a control equation is constructed based on the influencing parameters of the wellbore thermal mixing process, including:

[0033] The temperature of the bedrock medium and the flow rate of the target fractured aquifer are obtained, and a fractured medium heat transfer kinetic equation is constructed based on the volumetric specific heat capacity of the target fractured aquifer, the temperature of the target fractured aquifer, the thermal conductivity of the target fractured aquifer, the thermal diffusion of the target fractured aquifer, the volumetric specific heat capacity of water, the porosity of the target fractured aquifer, the thermal conductivity of the bedrock medium, the width of the target fractured aquifer, the temperature of the bedrock medium and the flow rate of the target fractured aquifer;

[0034] The bedrock medium heat transfer kinetic equation is constructed based on the volume specific heat capacity of the bedrock medium, the temperature of the bedrock medium and the thermal conductivity coefficient of the bedrock medium.

[0035] This embodiment provides a method for inverting heat transfer parameters of a fractured aquifer taking into account the thermal mixing process in the wellbore, which improves the simulation capability of the heat transfer process in the target fractured aquifer by constructing a kinetic equation for heat transfer in a fractured medium and a kinetic equation for heat transfer in a bedrock medium.

[0036] In an optional embodiment, the initial conditions and boundary conditions are determined based on the influencing parameters of the wellbore thermal mixing process, including:

[0037] obtaining initial temperatures in the fracture and bedrock media, and constructing initial conditions based on the temperature of the target fracture aquifer, the temperature of the bedrock media, and the initial temperatures in the fracture and bedrock media;

[0038] Boundary conditions are constructed based on the temperature of the target fractured aquifer, the temperature of the bedrock medium, the temperature within the geothermal injection well, and the initial temperatures in the fracture and bedrock medium.

[0039] This embodiment provides a method for inverting heat transfer parameters of a fractured aquifer taking into account the thermal mixing process in the wellbore. By constructing initial conditions and boundary conditions, the simulation capability of the heat transfer process in the target fractured aquifer is improved, and the accuracy of subsequent heat transfer parameter inversion is improved.

[0040] In an optional embodiment, determining the effective thermal diffusion coefficient based on the influencing parameters of the wellbore thermal mixing process includes:

[0041] The effective thermal diffusion coefficient is determined based on the thermal conductivity of the target fractured aquifer, the volumetric specific heat capacity of the target fractured aquifer, the thermal dissipation of the target fractured aquifer, the volumetric specific heat capacity of water and the flow velocity of the target fractured aquifer.

[0042] In an optional implementation, an optimization objective function is constructed based on the analytical solution of the three-stage single-well injection and pumping test, and parameter inversion is performed using the optimization objective function to generate heat transfer parameter values ​​of the target fractured aquifer, including:

[0043] Based on the analytical solution of the three-stage single-well injection and pumping test, the optimization objective function is constructed with the minimum fitting value of the three-stage single-well injection and pumping test as the goal;

[0044] The optimization objective function is solved to generate the heat transport parameter values ​​for the target fractured aquifer.

[0045] This embodiment provides a method for inverting heat transfer parameters of fractured aquifers taking into account the thermal mixing process of the wellbore, and combines the optimization objective function to invert key geothermal parameters, which greatly improves the efficiency of parameter inversion. Moreover, compared with existing methods, it is more convenient for engineering promotion and application, and provides technical support for the evaluation of the mining potential and development and utilization efficiency of geothermal resources.

[0046] In an optional implementation, based on the analytical solution of the three-stage single-well injection and pumping test, an optimization objective function is constructed with the goal of minimizing the fitting value of the three-stage single-well injection and pumping test, including:

[0047] The simulation values ​​of the sampling points are determined based on the analytical solution of the three-stage single-well injection and pumping test;

[0048] Obtain the observed values ​​of the sampling points, and determine the mean square error value of the three-stage single-well injection and pumping test based on the simulated values ​​and the observed values ​​of the sampling points;

[0049] The weighted coefficient of the three-stage single-well injection and pumping test is obtained, and the optimization objective function is constructed based on the mean square error value of the three-stage single-well injection and pumping test and the weighted coefficient of the three-stage single-well injection and pumping test.

[0050] This embodiment provides a method for inverting heat transfer parameters of a fractured aquifer taking into account the thermal mixing process of the wellbore, constructing an optimization objective function with the goal of minimizing the fitting value of a three-stage single-well injection and pumping test, thereby improving the efficiency and accuracy of parameter inversion.

[0051] In an optional implementation, an optimization objective function is constructed based on the mean square error value of the three-stage single-well injection and pumping test and the weighted coefficient of the three-stage single-well injection and pumping test. The expression of the optimization objective function is as follows:

[0052]

[0053] In the above formula, F represents the optimization objective function, μ i represents the weighting coefficient of the i-th stage, Δf i represents the mean square error value of the i-th stage, and u represents the number of stages in the single-well injection and pumping test.

[0054] In an optional implementation, it also includes:

[0055] The heat transfer parameter value of the target fractured aquifer is compared with the range of the geothermal heat transfer parameter, and when the heat transfer parameter value of the target fractured aquifer meets the range of the geothermal heat transfer parameter, the heat transfer parameter value of the target fractured aquifer is output.

[0056] In a second aspect, the present invention provides a device for inverting heat transport parameters of a fractured aquifer taking into account a wellbore thermal mixing process, the device comprising:

[0057] An acquisition module is used to acquire the target area drilling data and the target area hydrogeological data, and carry out a three-stage single well injection and pumping test based on the target area drilling data and the target area hydrogeological data to determine the influencing parameters of the wellbore thermal mixing process;

[0058] A construction module is used to construct a mathematical model of a single-well injection and pumping test considering the wellbore thermal mixing process based on the influencing parameters of the wellbore thermal mixing process;

[0059] The solution module is used to solve the mathematical model of the single-well injection and pumping test considering the wellbore thermal mixing process and generate the analytical solution of the three-stage single-well injection and pumping test;

[0060] The inversion module is used to construct an optimization objective function based on the analytical solution of the three-stage single-well injection and pumping test, and use the optimization objective function to perform parameter inversion to generate the heat transfer parameter value of the target fracture aquifer; wherein the heat transfer parameter value of the target fracture aquifer is used to evaluate geothermal resources.

[0061] In a third aspect, the present invention provides a computer device, comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to execute a method for inverting heat transfer parameters of a fractured aquifer taking into account the wellbore thermal mixing process according to the first aspect or any corresponding embodiment thereof.

[0062] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute a method for inverting heat transfer parameters of a fractured aquifer taking into account the thermal mixing process of a wellbore according to the first aspect or any corresponding embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0064] Figure 1 is a flow chart of a method for inverting heat transfer parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention;

[0065] Figure 2 is a flow chart of another method for inverting heat transfer parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention;

[0066] Figure 3 is a flow chart of another method for inverting heat transport parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention;

[0067] Figure 4 is a flow chart of another method for inverting heat transfer parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention;

[0068] Figure 5 is a schematic flow chart of a method for inverting heat transfer parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention;

[0069] Figure 6 is a schematic structural diagram of a target fractured aquifer according to an embodiment of the present invention;

[0070] Figure 7 is a schematic diagram of the fitting effect between the parameter inversion method according to an embodiment of the present invention and the three-stage single well injection and pumping test data;

[0071] Figure 8 is a structural block diagram of a device for inverting heat transfer parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention;

[0072] Fig. 9 It is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0074] Compared with other methods for obtaining heat transfer in aquifers, the three-stage single-well injection and pumping test is often used to invert the geothermal parameters of aquifers because of its low cost and high efficiency. The heat transfer parameter inversion method mainly consists of two models: forward model and optimization model. At present, there are many forward models for geothermal transfer, mainly including analytical solutions and numerical solutions. The advantage of the numerical solution model is that the corresponding mathematical model can describe the complex water flow movement process, but its disadvantages are also obvious, that is, the amount of calculation is relatively large, and when convection is dominant, the numerical error is difficult to eliminate, such as numerical dispersion and numerical fluctuation. The analytical solution model has a small amount of calculation and high accuracy, so the parameter inversion method mainly uses the analytical solution model to simulate the geothermal transfer process. Whether it is an analytical solution or a numerical solution, there are two problems: First, it may be in order to reduce the amount of calculation, assuming that the geothermal diffusion process is linearly related to the flow rate. In fact, for different formation lithologies, the relationship between the two may be nonlinear, resulting in the inability of existing models to accurately describe the heat transfer process in aquifers. Second, the thermal mixing process in the wellbore is weakened, resulting in the inability of the existing model to accurately describe the heat exchange process in the wellbore. These two assumptions may affect the accuracy of the heat transfer parameter inversion method.

[0075] In view of the shortcomings of the above methods, an embodiment of the present invention provides a method for inverting heat transfer parameters of a fractured aquifer taking into account the thermal mixing process of the wellbore.

[0076] According to an embodiment of the present invention, an embodiment of a method for inverting heat transfer parameters of a fractured aquifer considering the thermal mixing process in the wellbore is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in an order different from that shown here.

[0077] In this embodiment, a method for inverting heat transfer parameters of a fractured aquifer considering the thermal mixing process of a wellbore is provided, which can be used in the above-mentioned mobile terminals, such as mobile phones, tablet computers, etc. Figure 1 is a flow chart of a method for inverting heat transport parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention. Figure 1 As shown, the process includes the following steps:

[0078] Step S101, obtaining the target area drilling data and the target area hydrogeological data, and conducting a three-stage single well injection and pumping test based on the target area drilling data and the target area hydrogeological data to determine the influencing parameters of the wellbore thermal mixing process.

[0079] Step S102, constructing a mathematical model of a single well injection and pumping test taking into account the wellbore thermal mixing process based on the influencing parameters of the wellbore thermal mixing process.

[0080] Specifically, the Green's function method is used to derive the analytical solution of the three-stage single-well injection and pumping test considering the wellbore thermal mixing process.

[0081] Step S103, solving the mathematical model of the single-well injection and pumping test considering the wellbore thermal mixing process, and generating an analytical solution for the three-stage single-well injection and pumping test.

[0082] Step S104, constructing an optimization objective function based on the analytical solution of the three-stage single-well injection and pumping test, and using the optimization objective function to perform parameter inversion to generate heat transfer parameter values ​​of the target fractured aquifer; wherein the heat transfer parameter values ​​of the target fractured aquifer are used to evaluate geothermal resources.

[0083] Specifically, the analytical formula is combined with the optimization model, and then the numerical calculation is implemented based on MATLAB (a commercial mathematical software) or Mathematica platform (a scientific computing software that well combines numerical and symbolic computing engines, graphics systems, programming languages, text systems and advanced connections with other applications). By fitting the single-well injection and pumping test, the objective function is minimized, and the inverse geothermal parameters are within a given range. At this time, the inverse value is the parameter of the target aquifer, that is, the heat transfer parameter value of the target fracture aquifer.

[0084] The present embodiment provides a method for inverting heat transfer parameters in a fractured aquifer taking into account the thermal mixing process of the wellbore. The method takes into account the thermal mixing process of the wellbore by constructing a mathematical model of a single-well injection and pumping test taking into account the thermal mixing process of the wellbore, and solves the mathematical model of the single-well injection and pumping test taking into account the thermal mixing process of the wellbore, thereby generating an analytical solution of the three-stage single-well injection and pumping test. Furthermore, an optimization objective function is constructed based on the analytical solution of the three-stage single-well injection and pumping test, which can be used to invert and set key parameters in the heat transfer model in a fractured aquifer, can solve the problem of parameter identification in the numerical simulation process of heat transfer in a fractured aquifer, improves the accuracy and calculation efficiency of parameter inversion, and can provide technical support for the spatial distribution evaluation of geothermal resources and the efficient development of geothermal resources.

[0085] In this embodiment, a method for inverting heat transfer parameters of a fractured aquifer considering the thermal mixing process of a wellbore is provided, which can be used in the above-mentioned mobile terminals, such as mobile phones, tablet computers, etc. Figure 2 is a flow chart of a method for inverting heat transport parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention. Figure 2 As shown, the process includes the following steps:

[0086] Step S201, obtaining the target area drilling data and the target area hydrogeological data, and conducting a three-stage single well injection and pumping test based on the target area drilling data and the target area hydrogeological data to determine the influencing parameters of the wellbore thermal mixing process.

[0087] Specifically, the above step S201 includes:

[0088] Step S2011, determining the target fractured aquifer and geothermal injection well based on the target area drilling data and the target area hydrogeological data.

[0089] Specifically, through the drilling data and hydrogeological data of the target area, we can find out the main strata in the target area and the spatial distribution of these strata. Then, for each formation, we select the aquifer with small thickness variation, intact caprock, and complete fractures penetrated by the wellbore as the target fracture aquifer.

[0090] Furthermore, according to the hydrogeological conditions, complete wells with good caprocks in independent hydrogeological units are selected as geothermal injection wells.

[0091] Step S2012, measuring the target fractured aquifer and geothermal injection well respectively to determine the bedrock thickness and wellbore radius.

[0092] Step S2013, obtaining the lithology of the target fractured aquifer, and determining the range of geothermal heat transfer parameters based on the lithology of the target fractured aquifer.

[0093] Among them, geothermal transfer parameters include: volume specific heat capacity of bedrock medium, thermal conductivity coefficient of bedrock medium, volume specific heat capacity of target fracture aquifer, porosity of target fracture aquifer, thermal diffusion of target fracture aquifer, width of target fracture aquifer, thermal conductivity coefficient of target fracture aquifer, and volume specific heat capacity of water.

[0094] Furthermore, for each set of formations, according to the lithology of the target fractured aquifer, the range of the parameters of geothermal transmission of the formation lithology is determined by consulting literature or conducting indoor experiments.

[0095] Step S2014, obtain the temperature of the target fractured aquifer, and carry out a three-stage single-well injection and pumping test based on the temperature of the target fractured aquifer to determine the injection flow rate, pumping flow rate, liquid volume in the geothermal injection well, temperature in the geothermal injection well and temperature of the injected water body; wherein the three-stage single-well injection and pumping test includes single-well injection and pumping tests in injection stage, rest stage and pumping stage.

[0096] Specifically, before conducting the test, a temperature sensor is installed in the wellbore of the selected geothermal injection well to record the temperature, which represents the temperature of the target fractured aquifer. A certain amount of water is prepared, the volume of which is 30 times higher than the volume of the wellbore, and the temperature can be 10 degrees Celsius higher or lower than the original target fractured aquifer temperature. Then, a three-stage single-well injection and pumping test is carried out to monitor the temperature of the groundwater in the wellbore.

[0097] Furthermore, the steps of the three-stage single-well injection and extraction test include: injection stage: injecting the prepared hot water or cold water into the target fractured aquifer through the selected geothermal injection well, the volume of hot water or cold water injected into the wellbore per unit time through pumps and other equipment is the injection flow rate, and this process is the first stage; rest stage: after all the prepared hot water or cold water is injected, turn off the injection pump, wait for a period of time, and allow the water level in the injection well to recover, this process is the second stage; extraction stage: adjust the injection pump to pump water, and extract the hot water / cold water injected into the target fractured aquifer. When the water temperature of the final extracted water is consistent with the water temperature in the original fractured aquifer, the test is ended, and this process is the third stage.

[0098] Among them, since there is a certain volume of groundwater in the geothermal injection well before the test (i.e., the volume of groundwater before mixing), this part of water will change its temperature at the initial stage of hot water or cold water injection, resulting in the groundwater temperature in the well at the initial stage of the test gradually increasing from the original formation temperature to the temperature value of the injected hot water or cold water. This process is called the wellbore thermal mixing process in this patent.

[0099] This embodiment provides a method for inverting the heat transfer parameters of a fractured aquifer taking into account the thermal mixing process of the wellbore. By calculating the relevant data of the target fractured aquifer and the geothermal injection well, the influencing parameters of the thermal mixing process of the wellbore are determined, which lays a foundation for the subsequent mathematical model of single-well injection and pumping tests taking into account the thermal mixing process of the wellbore, and lays a foundation for the accuracy judgment of the heat transfer parameter value of the target fractured aquifer generated by subsequent inversion through the range of geothermal transfer parameters.

[0100] Step S202: construct a mathematical model of a single well injection and pumping test considering the wellbore thermal mixing process based on the influencing parameters of the wellbore thermal mixing process. Figure 1 Step S102 of the illustrated embodiment will not be described in detail here.

[0101] Step S203, solve the mathematical model of the single well injection and pumping test considering the wellbore thermal mixing process, and generate the analytical solution of the three-stage single well injection and pumping test. Figure 1 Step S103 of the illustrated embodiment will not be described in detail here.

[0102] Step S204, solve the mathematical model of the single well injection and pumping test considering the wellbore thermal mixing process, and generate the analytical solution of the three-stage single well injection and pumping test. Figure 1 Step S104 of the illustrated embodiment will not be described in detail here.

[0103] This embodiment provides a method for inverting heat transfer parameters in a fractured aquifer taking into account the thermal mixing process in the wellbore. By inverting key parameters of heat transfer, such as the thermal expansion conductivity coefficient and the thermal diffusion coefficient, the problem of parameter identification in the numerical simulation process of heat transfer is solved.

[0104] In this embodiment, a method for inverting heat transfer parameters of a fractured aquifer considering the thermal mixing process of a wellbore is provided, which can be used in the above-mentioned mobile terminals, such as mobile phones, tablet computers, etc. Figure 3 is a flow chart of a method for inverting heat transport parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention. Figure 3 As shown, the process includes the following steps:

[0105] Step S301, obtain the target area drilling data and target area hydrogeological data, carry out a three-stage single well injection and pumping test based on the target area drilling data and target area hydrogeological data, and determine the influencing parameters of the wellbore thermal mixing process. Figure 2 Step S201 of the illustrated embodiment will not be described in detail here.

[0106] Step S302: constructing a mathematical model of a single-well injection and pumping test taking into account the wellbore thermal mixing process based on the influencing parameters of the wellbore thermal mixing process.

[0107] Specifically, the above step S302 includes:

[0108] Step S3021, based on the influencing parameters of the wellbore thermal mixing process, a mixed effect model of the injection stage, a mixed effect model of the rest stage, and a mixed effect model of the extraction stage are respectively constructed.

[0109] In some optional implementations, the above step S3021 includes:

[0110] Step a1, constructing a mixed effect model for the injection phase based on the volumetric specific heat capacity of water, the liquid volume in the geothermal injection well during the injection phase, the temperature in the geothermal injection well, the injection flow rate and the temperature of the injected water body.

[0111] Specifically, the expression of the mixed effect model in the injection phase is as follows:

[0112]

[0113] T w (t=0)=T0 (2)

[0114] In the above formula, ρ w c w represents the volume specific heat capacity of water, ρ w represents the density of water, represents the specific heat capacity of water, V w,inj represents the liquid volume in the geothermal injection well during the injection phase, T w (t) represents the temperature in the geothermal injection well, Q inj Indicates the water injection flow rate, T inj represents the temperature of the injected water (i.e. the temperature of the injected hot or cold water), T0 represents the initial temperature in the fracture and bedrock medium, t represents the time, t inj Indicates the time of the injection phase.

[0115] Step a2, constructing a rest phase mixed effect model based on the temperature in the geothermal injection well and the temperature of the target fracture aquifer.

[0116] Specifically, the expression of the mixed effect model in the rest phase is as follows:

[0117]

[0118]

[0119] In the above formula, t res represents the rest period, T f (x, t) represents the temperature of the target fracture aquifer, and x represents the horizontal position.

[0120] Step a3, constructing a mixed effect model for the extraction phase based on the pumping flow rate, the volumetric specific heat capacity of water, the liquid volume in the geothermal injection well during the extraction phase, the temperature in the geothermal injection well, the width of the target fractured aquifer, the bedrock thickness, the thermal conductivity of the target fractured aquifer, and the temperature of the target fractured aquifer.

[0121] Specifically, the expression of the mixed effect model in the extraction stage is as follows:

[0122]

[0123]

[0124] In the above formula, b represents the width of the target fracture aquifer, B represents the thickness of the bedrock, and k f represents the thermal conductivity of the target fractured aquifer, t ext Indicates the time of the extraction phase.

[0125] Step S3022, constructing a control equation based on the influencing parameters of the wellbore thermal mixing process; wherein the control equation includes a fracture medium heat transfer kinetic equation and a bedrock medium heat transfer kinetic equation.

[0126] In some optional implementations, the above step S3022 includes:

[0127] Step b1, obtain the temperature of the bedrock medium and the flow rate of the target fractured aquifer, and construct a fractured medium heat transfer kinetic equation based on the volume specific heat capacity of the target fractured aquifer, the temperature of the target fractured aquifer, the thermal conductivity coefficient of the target fractured aquifer, the thermal diffusion coefficient of the target fractured aquifer, the volume specific heat capacity of water, the porosity of the target fractured aquifer, the thermal conductivity coefficient of the bedrock medium, the width of the target fractured aquifer, the temperature of the bedrock medium and the flow rate of the target fractured aquifer.

[0128] Specifically, the expression of the fracture medium heat transfer kinetic equation is as follows:

[0129]

[0130] In the above formula, ρ f c f represents the volume specific heat capacity of the target fractured aquifer, ρ f represents the density of the target fractured aquifer, c f represents the specific heat capacity of the target fractured aquifer, α represents the thermal dispersion of the target fractured aquifer, v represents the flow velocity of the target fractured aquifer, mm is a constant (its value is 1 to 2), φ f represents the porosity of the target fractured aquifer, T m (x,z,t) represents the temperature of the bedrock medium, k mrepresents the thermal conductivity of the bedrock medium, and z represents the vertical position.

[0131] Furthermore, during the injection phase, the flow rate of the target fracture aquifer is calculated as follows:

[0132]

[0133] In the above formula, Q inj Indicates the water injection flow rate.

[0134] Furthermore, during the extraction phase, the flow rate of the target fracture aquifer is calculated as follows:

[0135]

[0136] In the above formula, Q ext Indicates the extraction flow.

[0137] Step b2, constructing a bedrock medium heat transfer kinetic equation based on the volume specific heat capacity of the bedrock medium, the temperature of the bedrock medium, and the thermal conductivity coefficient of the bedrock medium.

[0138] Specifically, the expression of the bedrock medium heat transfer kinetic equation is as follows:

[0139]

[0140] In the above formula, ρ m c m represents the volume specific heat capacity of bedrock medium, ρ m represents the density of the bedrock medium, c m Represents the specific heat capacity of the bedrock medium.

[0141] Step S3023, determining initial conditions and boundary conditions based on the influencing parameters of the wellbore thermal mixing process.

[0142] In some optional implementations, the above step S3023 includes:

[0143] Step c1, obtaining the initial temperature in the fracture and bedrock medium, and constructing the initial conditions based on the temperature of the target fracture aquifer, the temperature of the bedrock medium and the initial temperature in the fracture and bedrock medium.

[0144] Specifically, the initial conditions are as follows:

[0145] T f (x,t=0)=T m (x,z,t=0)=T0 (11)

[0146] Step c2, constructing boundary conditions based on the temperature of the target fractured aquifer, the temperature of the bedrock medium, the temperature in the geothermal injection well, and the initial temperatures in the fractures and bedrock medium.

[0147] Specifically, the boundary conditions include the outer boundary conditions of the wellbore and the inner boundary conditions of the wellbore, wherein the expression of the outer boundary conditions at the horizontal position of the wellbore is as follows:

[0148] T f (x→∞,t)=T0,t>0 (12)

[0149] Furthermore, the expression of the outer boundary condition of the vertical position of the wellbore is as follows:

[0150] T m (z→∞,t)=T0,t>0 (13)

[0151] Furthermore, the expression of the boundary condition inside the wellbore is as follows:

[0152] T f (x=0,t)=T w (t), t>0 (14)

[0153] T f (x,t)=T m (x,z=0,t), t>0 (15)

[0154] Step S3024, determining the effective thermal diffusion coefficient based on the influencing parameters of the wellbore thermal mixing process.

[0155] Specifically, the effective thermal diffusion coefficient is determined based on the thermal conductivity of the target fracture aquifer, the volume specific heat capacity of the target fracture aquifer, the thermal dissipation of the target fracture aquifer, the volume specific heat capacity of water and the flow rate of the target fracture aquifer; the expression of the effective thermal diffusion coefficient D is as follows:

[0156]

[0157] Step S3025, construct a mathematical model of a single well injection and extraction test considering the wellbore thermal mixing process based on the heat transfer kinetic equation, initial conditions, boundary conditions, effective thermal diffusion coefficient, injection stage mixing effect model, rest stage mixing effect model and extraction stage mixing effect model.

[0158] Step S303, solving the mathematical model of the single-well injection and pumping test considering the wellbore thermal mixing process, and generating an analytical solution for the three-stage single-well injection and pumping test.

[0159] Specifically, the analytical solution of the injection stage in the three-stage single-well injection and pumping test is:

[0160]

[0161]

[0162] Where exp(·) represents the exponential function, represents the temperature in the bedrock medium in Laplace space, represents the temperature in the fracture medium in Laplace space, s represents the Laplace variable, α inj represents the first parameter, β represents the second parameter, δ represents the third parameter, x D represents the dimensionless distance, θ represents the fourth parameter, where

[0163]

[0164]

[0165]

[0166]

[0167]

[0168]

[0169]

[0170]

[0171]

[0172] Furthermore, the analytical solution of the rest phase in the three-stage single-well injection and pumping test is:

[0173]

[0174]

[0175]

[0176] f(η)=θT mD (t injD )-θs(δ1+δ2η) (31)

[0177]

[0178] Where η is the Green function g(z D ,θs;η), χ represents the Green function G1(x D ,s;χ) of the integral variable, z eD represents the distance between the outer boundary of the bedrock and the crack, and f(η) represents g(z D ,θs;η) is a function of the integral variable, δ1 represents the fifth parameter, δ2 represents the sixth parameter, zD represents dimensionless distance, f0(χ) represents G1(x D ,s;χ) function of the integral variable, T mD represents the dimensionless temperature in the bedrock medium, t injD represents the dimensionless injection time, C1, C2 and C3 represent the coefficients of the Green's function (determined by equations 36-37), T fD represents the dimensionless temperature in the fractured medium, where

[0179] f0(χ)=βT fD (t injD ) (33)

[0180]

[0181]

[0182]

[0183]

[0184] Furthermore, the analytical solution of the extraction stage in the three-stage single-well injection and extraction test is:

[0185]

[0186]

[0187]

[0188]

[0189]

[0190]

[0191] in, is the Green function The integral variable, is the Green function The integral variable, and represents two Green's functions with different coefficients and kernel functions, express Function of the integral variable, express The function of the integral variable, a1 represents the seventh parameter, b1 represents the eighth parameter, m represents the ninth parameter, n represents the tenth parameter, D1, D2, D2, D3, E1, E1, E2 and E4 represent the coefficients of the Green's function, t D represents dimensionless time, t resDrepresents the dimensionless rest time, ε represents the eleventh parameter, T fD represents the dimensionless temperature in the fractured medium, where

[0192]

[0193]

[0194] m=-nx eD (46)

[0195]

[0196] D1=-D2 (48)

[0197]

[0198]

[0199] E1=WE2 (51)

[0200]

[0201]

[0202]

[0203] in, Represents the dimensionless temperature of the injection and extraction test.

[0204] Step S304: construct an optimization objective function based on the analytical solution of the three-stage single well injection and pumping test, and use the optimization objective function to perform parameter inversion to generate the heat transfer parameter value of the target fractured aquifer; wherein the heat transfer parameter value of the target fractured aquifer is used to evaluate geothermal resources. Figure 2 Step S204 of the illustrated embodiment will not be described in detail here.

[0205] This embodiment provides a method for inverting heat transfer parameters in a fractured aquifer taking into account the thermal mixing process in the wellbore. The existing analytical solution models for three-stage single-well injection and pumping geothermal transfer all assume that the geothermal diffusion process is linearly related to the flow rate. This assumption often violates the actual physical laws. This embodiment takes into account the nonlinearity between heat diffusion and flow rate in the process of constructing a mathematical model of a single-well injection and pumping test taking into account the thermal mixing process in the wellbore, thereby improving the simulation capability of the heat transfer process in the fractured aquifer and the accuracy of the inversion of heat transfer parameters.

[0206] In this embodiment, a method for inverting heat transfer parameters of a fractured aquifer considering the thermal mixing process of a wellbore is provided, which can be used in the above-mentioned mobile terminals, such as mobile phones, tablet computers, etc. Figure 4is a flow chart of a method for inverting heat transport parameters of a fractured aquifer considering a wellbore thermal mixing process according to an embodiment of the present invention. Figure 4 As shown, the process includes the following steps:

[0207] Step S401, obtain the target area drilling data and target area hydrogeological data, carry out a three-stage single well injection and pumping test based on the target area drilling data and target area hydrogeological data, and determine the influencing parameters of the wellbore thermal mixing process. Figure 3 Step S301 of the illustrated embodiment will not be described in detail here.

[0208] Step S402: construct a mathematical model of a single well injection and pumping test considering the wellbore thermal mixing process based on the influencing parameters of the wellbore thermal mixing process. Figure 3 Step S302 of the illustrated embodiment will not be described in detail here.

[0209] Step S403, solve the mathematical model of the single well injection and pumping test considering the wellbore thermal mixing process, and generate the analytical solution of the three-stage single well injection and pumping test. Figure 3 Step S303 of the illustrated embodiment will not be described in detail here.

[0210] Step S404, constructing an optimization objective function based on the analytical solution of the three-stage single well injection and pumping test, and using the optimization objective function to perform parameter inversion to generate heat transfer parameter values ​​of the target fractured aquifer; wherein the heat transfer parameter values ​​of the target fractured aquifer are used to evaluate geothermal resources.

[0211] Specifically, the above step S404 includes:

[0212] Step S4041, based on the analytical solution of the three-stage single-well injection and pumping test, an optimization objective function is constructed with the goal of minimizing the fitting value of the three-stage single-well injection and pumping test.

[0213] In some optional implementations, the above step S4041 includes:

[0214] Step d1, determining the simulation value of the sampling point based on the analytical solution of the three-stage single-well injection and pumping test.

[0215] Step d2, obtaining the observed values ​​of the sampling points, and determining the mean square error value of the three-stage single-well injection and pumping test based on the simulated values ​​of the sampling points and the observed values ​​of the sampling points.

[0216] Specifically, the calculation formula for the mean square error value of the three-stage single-well injection and pumping test is as follows:

[0217]

[0218] In the above formula, p1~p Lrepresents the parameters to be determined, L represents the number of parameters to be determined, j represents the number of sampling points in the iteration process, i represents the stage, is the observed value or reference value of the jth sampling point, is the simulated value of the jth sampling point, which is calculated by the above formula (17)-formula (54), and N represents the total number of sampling points.

[0219] Step d3, obtaining the weighted coefficient of the three-stage single-well injection and pumping test, and constructing an optimization objective function based on the mean square error value of the three-stage single-well injection and pumping test and the weighted coefficient of the three-stage single-well injection and pumping test.

[0220] Specifically, the expression of the optimization objective function is as follows:

[0221]

[0222] In the above formula, F represents the optimization objective function, μ i represents the weighting coefficient of the i-th stage, Δf i represents the mean square error value of the i-th stage, and u represents the number of stages in the single-well injection and pumping test.

[0223] Step S4042, solving the optimization objective function to generate heat transfer parameter values ​​of the target fractured aquifer.

[0224] Specifically, based on the MATLAB (a commercial mathematical software) or Mathematica (a scientific computing software that well combines numerical and symbolic computing engines, graphics systems, programming languages, text systems, and advanced connections with other applications) platform, the optimization objective function is solved to generate the heat transfer parameter values ​​of the target fractured aquifer.

[0225] Further, the heat transfer parameter value of the target fractured aquifer is compared with the range of the geothermal heat transfer parameter, and when the heat transfer parameter value of the target fractured aquifer meets the range of the geothermal heat transfer parameter, the heat transfer parameter value of the target fractured aquifer is output.

[0226] This embodiment provides a method for inverting heat transfer parameters of fractured aquifers taking into account the thermal mixing process of the wellbore, and combines the optimization objective function to invert key geothermal parameters, which greatly improves the efficiency of parameter inversion. Moreover, compared with existing methods, it is more convenient for engineering promotion and application, and provides technical support for the evaluation of the mining potential and development and utilization efficiency of geothermal resources.

[0227] The following is a specific example to illustrate the steps of a method for inverting heat transfer parameters of a fractured aquifer taking into account the thermal mixing process in the wellbore.

[0228] Embodiment 1:

[0229] like Figure 5As shown in the figure, the steps of the inversion method for heat transport parameters of fractured aquifers considering the thermal mixing process in the wellbore are as follows:

[0230] Step 1: Determine the target fractured aquifer through the drilling data and hydrogeological data of the study area; at the same time, according to the hydrogeological conditions, select complete wells with good caprocks in independent hydrogeological units as geothermal injection wells;

[0231] Step 2: Determine the range of geothermal heat transfer parameters based on the lithology of the target fractured aquifer;

[0232] Step 3: Measure the temperature of the target fracture aquifer, prepare hot water or cold water 30 times higher than the volume of the wellbore, and the temperature of the prepared hot water or cold water is 10 degrees higher or lower than the original target fracture aquifer temperature, carry out a three-stage single well injection and pumping test, and monitor the temperature of the groundwater in the wellbore;

[0233] Step 4: Based on the key parameters affecting the wellbore thermal mixing process obtained in step 3, a mathematical model of the single-well injection and pumping test is constructed that takes into account the wellbore thermal mixing process and the nonlinear relationship between thermal diffusion and flow rate;

[0234] Step 5: Based on step 3, the Green function method is used to derive the analytical solution of the single well injection and pumping test considering the wellbore thermal mixing process;

[0235] Step 6: Combine the analytical formula with the optimization model, and then implement numerical calculation based on MATLAB or Mathematica platform. By fitting the single well injection and pumping test, the objective function is minimized, and the inverse geothermal parameters are within a given range. At this time, the inverse value is the parameter of the target aquifer.

[0236] Embodiment 2:

[0237] In order to verify the accuracy of the inversion method of heat transfer parameters of fractured aquifers considering the wellbore thermal mixing process, it is assumed that the heat transfer parameter values ​​of the target fractured aquifer are known, and then numerical simulation software is used to construct numerical values ​​instead of actual observed data for illustration.

[0238] Build as Figure 6 A numerical model of the fractured aquifer structure shown is constructed, and the three-stage single-well injection and pumping test data are calculated through the constructed numerical model. These calculated data are used as reference benchmark values. Based on the reference benchmark values, the method of the present invention is used to invert the key parameters of heat transfer. Figure 61 in the figure represents the width of the fractured aquifer; X and Z represent the constructed coordinate system; 2 represents the fractured aquifer, which is the flow channel for the hot water or cold water injected into the injection well; 3 represents the flow rate of the hot water or cold water injected during the injection phase and the water flow rate during the extraction phase; 4 represents the injection wellbore, whose main function is to cause the wellbore thermal mixing process; 5 represents the diameter of the wellbore; 6 represents the filter pipe on the well wall, through which the fluid in the wellbore is exchanged with the fractured aquifer; and 7 represents the thickness of the aquifer.

[0239] Build as Figure 6 The fractured aquifer structure shown in FIG. 1 is numerically modeled: This embodiment uses COMSOL numerical simulation software (a multi-physics simulation software) to construct the following Figure 6 The fractured aquifer structure shown in the figure simulates a three-stage single well injection and pumping test. The length, width, and height of the constructed numerical model are 15m, 10m, and 5m respectively, and the wellbore radius r w =0.25m, the thickness of the fractured aquifer is 0.25m, and the thickness of the bedrock medium is 5m. The numerical model divides a total of 882579 grids and the results of 8825790 grids are consistent, and the numerical error can be ignored. The basic thermal parameters used in the numerical model are: ρ w c w =4.2×10 6 J / (m 3 ·℃), ρ f c f =2.65×10 6 J / (m 3 ℃), I m c m =2.38×10 6 J / (m 3 ℃), k f =2.3W / (m·℃), k m =1.8W / (m·℃), α=0.1m, T inj =30℃, T0=10℃, φ f =0.38, Q inj =50m 3 / d,Q ext =45m 3 / d,V w,inj =39m 3 , V w,ext =35m 3 , mm = 2, t ibj =250h, t res =50h,t ext =400h, b=0.25m, B=5.0m. Among them, J / (m 3·℃) is joule / (cubic meter·degrees Celsius), W / (m·℃) is watt / (meter·degrees Celsius), m 3 / d is cubic meters per day, and h is hour.

[0240] In this simulation, the middle position inside the wellbore was selected to obtain the reference benchmark value, and the obtained reference benchmark value was expressed in normalized temperature.

[0241] Based on the results of the three-stage single well injection and pumping test simulated by the numerical model, the specific implementation steps of the technical solution of the present invention are as follows:

[0242] In step 1, the basic parameters of the injection well can be determined based on the constructed numerical model: well radius r w =0.25m, the volume of fluid in the wellbore during the injection and extraction phases: V w,inj =39m 3 and V w,ext =35m 3 ;

[0243] In step 2, the basic parameters of heat transport in fractured aquifers can be determined based on the constructed numerical model: ρ w c w =4.2×10 6 J / (m 3 ·℃), ρ f c f =2.65×10 6 J / (m 3 ·℃), ρ m c m =2.38×10 6 J / (m 3 ℃), k f =2.3W / (m·℃), k m =1.8W / (m·℃), α=0.1m, b=0.25m, B=5.0m, φ f =0.38;

[0244] In step 3, the target fracture aquifer temperature determined based on the constructed numerical model is T0 = 10 °C, and the prepared hot water temperature is T inj =30℃, the flow rate and duration of each stage of the three-stage single well injection and pumping test are: Q inj =50m 3 / d,Q ext =45m 3 / d,t inj =250h, t res =50h,t ext =400h;

[0245] In step 4, the coefficient describing the nonlinear relationship between heat dispersion and flow velocity is set to: mm = 2;

[0246] The optimization objective function is written in MATLAB, and the key thermal attribute parameter k of the target fractured aquifer is inverted by fitting the single well injection and pumping test data (the benchmark reference value calculated by the numerical model). f , α and k m , so that the objective function reaches the minimum value. In this embodiment, when the objective function F≤1E-5, the thermal property parameter k output by the method of the present invention is f , α and k m The value is the inversion result.

[0247] In this embodiment, after optimizing the fitting between the method of the present invention and the reference value calculated by the numerical model, the result of the inversion of the key thermal property parameters is: k f =2.28W / (m·℃), k m =1.81W / (m·℃) and α=0.1m, the fitting results are as follows Figure 7 shown.

[0248] Figure 7 The results show that the parameter inversion method of the present invention can well explain the reference value / observation value, proving that the method of the present invention can effectively invert the key parameters of heat transfer, indicating that the method of the present invention can solve the problem of parameter identification in the process of numerical simulation of heat transfer.

[0249] In this embodiment, a device for inverting heat transfer parameters of fractured aquifers considering the thermal mixing process of the wellbore is also provided. The device is used to implement the above-mentioned embodiments and preferred implementation modes, and the descriptions that have been made will not be repeated. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0250] This embodiment provides a device for inverting heat transfer parameters of fractured aquifers considering the thermal mixing process of the wellbore. Figure 8 As shown, including:

[0251] The acquisition module 801 is used to acquire the target area drilling data and the target area hydrogeological data, and carry out a three-stage single well injection and pumping test based on the target area drilling data and the target area hydrogeological data to determine the influencing parameters of the wellbore thermal mixing process;

[0252] A construction module 802 is used to construct a mathematical model of a single well injection and pumping test considering the wellbore thermal mixing process based on the influencing parameters of the wellbore thermal mixing process;

[0253] A solution module 803 is used to solve the mathematical model of the single-well injection and pumping test considering the wellbore thermal mixing process, and generate an analytical solution for the three-stage single-well injection and pumping test;

[0254] The inversion module 804 is used to construct an optimization objective function based on the analytical solution of the three-stage single-well injection and pumping test, and use the optimization objective function to perform parameter inversion to generate the heat transfer parameter value of the target fracture aquifer; wherein the heat transfer parameter value of the target fracture aquifer is used to evaluate geothermal resources.

[0255] In some optional implementations, the acquisition module 801 includes:

[0256] A first determination submodule is used to determine the target fractured aquifer and geothermal water injection well based on the target area drilling data and the target area hydrogeological data;

[0257] The measurement submodule is used to measure the target fractured aquifer and geothermal injection well respectively to determine the bedrock thickness and wellbore radius;

[0258] A second determination submodule is used to obtain the lithology of the target fractured aquifer and determine the range of the geothermal transport parameter based on the lithology of the target fractured aquifer;

[0259] The test submodule is used to obtain the temperature of the target fractured aquifer, and carry out a three-stage single-well injection and pumping test based on the temperature of the target fractured aquifer to determine the injection flow rate, pumping flow rate, liquid volume in the geothermal injection well, temperature in the geothermal injection well and temperature of the injected water body; among which, the three-stage single-well injection and pumping test includes single-well injection and pumping tests in the injection stage, rest stage and pumping stage.

[0260] In some optional embodiments, the geothermal heat transport parameter in the range of geothermal heat transport parameters includes:

[0261] Volumetric specific heat capacity of bedrock medium, thermal conductivity coefficient of bedrock medium, volumetric specific heat capacity of target fractured aquifer, porosity of target fractured aquifer, thermal diffusion of target fractured aquifer, width of target fractured aquifer, thermal conductivity coefficient of target fractured aquifer, volumetric specific heat capacity of water.

[0262] In some optional implementations, building module 802 includes:

[0263] The first construction submodule is used to respectively construct an injection phase mixing effect model, a rest phase mixing effect model and an extraction phase mixing effect model based on the influencing parameters of the wellbore thermal mixing process;

[0264] The second construction submodule is used to construct a control equation based on the influencing parameters of the wellbore thermal mixing process; wherein the control equation includes a fracture medium heat transfer kinetic equation and a bedrock medium heat transfer kinetic equation;

[0265] A third determination submodule is used to determine initial conditions and boundary conditions based on influencing parameters of the wellbore thermal mixing process;

[0266] a fourth determination submodule, for determining an effective thermal diffusion coefficient based on an influencing parameter of a wellbore thermal mixing process;

[0267] The third construction submodule is used to construct a mathematical model of a single-well injection and extraction test considering the wellbore thermal mixing process based on the heat transfer kinetic equation, initial conditions, boundary conditions, effective thermal diffusion coefficient, injection stage mixing effect model, rest stage mixing effect model and extraction stage mixing effect model.

[0268] In some optional implementations, the first building block includes:

[0269] A first construction unit is used to construct a mixed effect model of the injection phase based on the volumetric specific heat capacity of water, the liquid volume in the geothermal water injection well during the injection phase, the temperature in the geothermal water injection well, the injection flow rate and the temperature of the injected water body;

[0270] A second construction unit is used to construct a rest phase mixed effect model based on the temperature in the geothermal injection well and the temperature of the target fractured aquifer;

[0271] The third construction unit is used to construct a mixed effect model of the extraction stage based on the pumping flow rate, the volumetric specific heat capacity of water, the liquid volume in the geothermal injection well during the extraction stage, the temperature in the geothermal injection well, the width of the target fracture aquifer, the bedrock thickness, the thermal conductivity coefficient of the target fracture aquifer and the temperature of the target fracture aquifer.

[0272] In some optional embodiments, the second building block includes:

[0273] a fourth construction unit, for obtaining the temperature of the bedrock medium and the flow rate of the target fractured aquifer, and constructing a fractured medium heat transfer kinetic equation based on the volumetric specific heat capacity of the target fractured aquifer, the temperature of the target fractured aquifer, the thermal conductivity coefficient of the target fractured aquifer, the thermal diffusion of the target fractured aquifer, the volumetric specific heat capacity of water, the porosity of the target fractured aquifer, the thermal conductivity coefficient of the bedrock medium, the width of the target fractured aquifer, the temperature of the bedrock medium and the flow rate of the target fractured aquifer;

[0274] The fifth construction unit is used to construct a bedrock medium heat transfer kinetic equation based on the volume specific heat capacity of the bedrock medium, the temperature of the bedrock medium, and the thermal conductivity coefficient of the bedrock medium.

[0275] In some optional implementations, the third determining submodule includes:

[0276] a sixth construction unit, for obtaining initial temperatures in the fracture and bedrock medium, and constructing initial conditions based on the temperature of the target fracture aquifer, the temperature of the bedrock medium, and the initial temperatures in the fracture and bedrock medium;

[0277] The seventh construction unit is used to construct boundary conditions based on the temperature of the target fracture aquifer, the temperature of the bedrock medium, the temperature in the geothermal injection well, and the initial temperature in the fracture and bedrock medium.

[0278] In some optional embodiments, the fourth determination submodule is specifically used to determine the effective thermal diffusion coefficient based on the thermal conductivity coefficient of the target fracture aquifer, the volume specific heat capacity of the target fracture aquifer, the thermal diffusion coefficient of the target fracture aquifer, the volume specific heat capacity of water and the flow velocity of the target fracture aquifer.

[0279] In some optional embodiments, the inversion module 804 includes:

[0280] The fourth construction submodule is used to construct an optimization objective function based on the analytical solution of the three-stage single-well injection and pumping test and with the goal of minimizing the fitting value of the three-stage single-well injection and pumping test;

[0281] The solution submodule is used to solve the optimization objective function and generate the heat transfer parameter value of the target fracture aquifer.

[0282] In some optional implementations, the fourth building block includes:

[0283] A first determination unit is used to determine the simulation value of the sampling point based on the analytical solution of the three-stage single well injection and pumping test;

[0284] A second determination unit is used to obtain the observed value of the sampling point, and determine the mean square error value of the three-stage single well injection and pumping test based on the simulated value of the sampling point and the observed value of the sampling point;

[0285] The eighth construction unit is used to obtain the weighted coefficient of the three-stage single-well injection and pumping test, and to construct an optimization objective function based on the mean square error value of the three-stage single-well injection and pumping test and the weighted coefficient of the three-stage single-well injection and pumping test.

[0286] In some optional implementations, the expression of the optimization objective function in the eighth building block is as follows:

[0287]

[0288] In the above formula, F represents the optimization objective function, μ i represents the weighting coefficient of the i-th stage, Δf i represents the mean square error value of the i-th stage, and u represents the number of stages in the single-well injection and pumping test.

[0289] In some optional embodiments, the method further comprises:

[0290] The comparison module is used to compare the heat transfer parameter value of the target fracture aquifer with the range of the geothermal transfer parameter, and when the heat transfer parameter value of the target fracture aquifer meets the range of the geothermal transfer parameter, output the heat transfer parameter value of the target fracture aquifer.

[0291] The further functional description of each of the above modules and units is the same as that of the above corresponding embodiments and will not be repeated here.

[0292] In this embodiment, a device for inverting heat transfer parameters of a fractured aquifer taking into account the thermal mixing process of the wellbore is presented in the form of a functional unit, where the unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that executes one or more software or fixed programs, and / or other devices that can provide the above functions.

[0293] The embodiment of the present invention also provides a computer device having the above Figure 8 A device for inverting heat transport parameters in a fractured aquifer considering the thermal mixing process in the wellbore is shown.

[0294] See also Fig. 9 , Fig. 9 is a schematic diagram of the structure of a computer device provided by an optional embodiment of the present invention, such as Fig. 9 As shown, the computer device includes: one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components are connected to each other using different buses for communication, and can be installed on a common mainboard or installed in other ways as needed. The processor can process the instructions executed in the computer device, including instructions stored in or on the memory to display the graphical information of the GUI on an external input / output device (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple computer devices can be connected, and each device provides some necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Fig. 9 A processor 10 is taken as an example.

[0295] The processor 10 may be a central processing unit, a network processor or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be a dedicated integrated circuit, a programmable logic device or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic or any combination thereof.

[0296] The memory 20 stores instructions executable by at least one processor 10, so that the at least one processor 10 executes the method shown in the above embodiment.

[0297] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the computer device, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely arranged relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0298] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid state drive; the memory 20 may also include a combination of the above types of memory.

[0299] The computer device also includes an input device 30 and an output device 40. The processor 10, the memory 20, the input device 30 and the output device 40 may be connected via a bus or other means. Fig. 9 The example of connecting through bus is taken in the following.

[0300] The input device 30 can receive input digital or character information, and generate key signal input related to the user settings and function control of the computer device, such as a touch screen, a keypad, a mouse, a track pad, a touch pad, an indicator bar, one or more mouse buttons, a trackball, a joystick, etc. The output device 40 may include a display device, an auxiliary lighting device (e.g., an LED) and a tactile feedback device (e.g., a vibration motor), etc. The above-mentioned display device includes but is not limited to a liquid crystal display, a light emitting diode, a display and a plasma display. In some optional embodiments, the display device can be a touch screen.

[0301] The embodiment of the present invention also provides a computer-readable storage medium. The method according to the embodiment of the present invention can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0302] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for inverting heat transfer parameters of fractured aquifers considering the thermal mixing process of wellbore, characterized in that: The method comprises: Obtaining target area drilling data and target area hydrogeological data, and conducting a three-stage single well injection and pumping test based on the target area drilling data and target area hydrogeological data to determine the influencing parameters of the wellbore thermal mixing process; Based on the influencing parameters of the wellbore thermal mixing process, a mathematical model of a single well injection and pumping test considering the wellbore thermal mixing process is constructed; Solving the mathematical model of the single-well injection and pumping test considering the wellbore thermal mixing process, generating an analytical solution for the three-stage single-well injection and pumping test; An optimization objective function is constructed based on the analytical solution of the three-stage single-well injection and pumping test, and parameter inversion is performed using the optimization objective function to generate heat transfer parameter values ​​of the target fractured aquifer; wherein the heat transfer parameter values ​​of the target fractured aquifer are used to evaluate geothermal resources; The single-well injection and pumping test mathematical model considering the wellbore thermal mixing process is constructed based on the influencing parameters of the wellbore thermal mixing process, including: Based on the influencing parameters of the wellbore thermal mixing process, a mixed effect model for the injection stage, a mixed effect model for the rest stage and a mixed effect model for the extraction stage are respectively constructed; Constructing a control equation based on the influencing parameters of the wellbore thermal mixing process; wherein the control equation includes a fracture medium heat transfer kinetic equation and a bedrock medium heat transfer kinetic equation; Determining initial conditions and boundary conditions based on influencing parameters of the wellbore thermal mixing process; determining an effective thermal diffusion coefficient based on influencing parameters of the wellbore thermal mixing process; The mathematical model of the single-well injection and extraction test considering the wellbore thermal mixing process is constructed based on the heat transfer kinetic equation, the initial conditions, the boundary conditions, the effective thermal diffusion coefficient, the injection stage mixing effect model, the rest stage mixing effect model and the extraction stage mixing effect model.

2. The method according to claim 1, characterized in that The three-stage single-well injection and pumping test is carried out based on the drilling data and hydrogeological data of the target area to determine the influencing parameters of the wellbore thermal mixing process, including: Determine a target fractured aquifer and a geothermal water injection well based on the target area drilling data and the target area hydrogeological data; Measuring the target fractured aquifer and the geothermal water injection well respectively to determine the bedrock thickness and the wellbore radius; Obtaining the lithology of the target fractured aquifer, and determining the range of geothermal transport parameters based on the lithology of the target fractured aquifer; The temperature of the target fractured aquifer is obtained, and based on the temperature of the target fractured aquifer, a three-stage single-well injection and pumping test is carried out to determine the injection flow rate, pumping flow rate, liquid volume in the geothermal injection well, temperature in the geothermal injection well and temperature of the injected water body; wherein the three-stage single-well injection and pumping test includes single-well injection and pumping tests in injection stage, rest stage and pumping stage.

3. The method according to claim 2, characterized in that The geothermal heat transfer parameters in the range of geothermal heat transfer parameters include: Volumetric specific heat capacity of bedrock medium, thermal conductivity coefficient of bedrock medium, volumetric specific heat capacity of target fractured aquifer, porosity of target fractured aquifer, thermal diffusion of target fractured aquifer, width of target fractured aquifer, thermal conductivity coefficient of target fractured aquifer, volumetric specific heat capacity of water.

4. The method according to claim 3, characterized in that The injection phase mixed effect model, the rest phase mixed effect model and the extraction phase mixed effect model are respectively constructed based on the influencing parameters of the wellbore thermal mixing process, including: Constructing the mixed effect model of the injection phase based on the volumetric specific heat capacity of the water, the liquid volume in the geothermal water injection well during the injection phase, the temperature in the geothermal water injection well, the water injection flow rate and the temperature of the injected water body; Constructing the rest phase mixed effect model based on the temperature in the geothermal water injection well and the temperature of the target fractured aquifer; The mixed effect model of the extraction stage is constructed based on the pumping flow rate, the volumetric specific heat capacity of the water, the liquid volume in the geothermal injection well during the extraction stage, the temperature in the geothermal injection well, the width of the target fractured aquifer, the bedrock thickness, the thermal conductivity coefficient of the target fractured aquifer and the temperature of the target fractured aquifer.

5. The method according to claim 3, characterized in that: The control equation is constructed based on the influencing parameters of the wellbore thermal mixing process, including: Acquire the temperature of the bedrock medium and the flow rate of the target fractured aquifer, and construct the fractured medium heat transfer kinetic equation based on the volume specific heat capacity of the target fractured aquifer, the temperature of the target fractured aquifer, the thermal conductivity coefficient of the target fractured aquifer, the thermal dispersion of the target fractured aquifer, the volume specific heat capacity of the water, the porosity of the target fractured aquifer, the thermal conductivity coefficient of the bedrock medium, the width of the target fractured aquifer, the temperature of the bedrock medium and the flow rate of the target fractured aquifer; The bedrock medium heat transfer kinetic equation is constructed based on the volume specific heat capacity of the bedrock medium, the temperature of the bedrock medium, and the thermal conductivity coefficient of the bedrock medium.

6. The method according to claim 5, characterized in that The determining of initial conditions and boundary conditions based on the influencing parameters of the wellbore thermal mixing process includes: Acquiring initial temperatures in fractures and bedrock media, and constructing the initial conditions based on the temperature of the target fracture aquifer, the temperature of the bedrock medium, and the initial temperatures in the fractures and bedrock media; The boundary conditions are constructed based on the temperature of the target fractured aquifer, the temperature of the bedrock medium, the temperature within the geothermal injection well, and the initial temperatures in the fractures and bedrock medium.

7. The method according to claim 5, characterized in that The determining of the effective thermal diffusion coefficient based on the influencing parameters of the wellbore thermal mixing process comprises: The effective thermal diffusion coefficient is determined based on the thermal conductivity of the target fractured aquifer, the volumetric specific heat capacity of the target fractured aquifer, the thermal dissipation of the target fractured aquifer, the volumetric specific heat capacity of the water, and the flow velocity of the target fractured aquifer.

8. The method according to claim 1, characterized in that The optimization objective function is constructed based on the analytical solution of the three-stage single well injection and pumping test, and the optimization objective function is used to perform parameter inversion to generate the heat transfer parameter value of the target fractured aquifer, including: Based on the analytical solution of the three-stage single-well injection and pumping test, the optimization objective function is constructed with the goal of minimizing the fitting value of the three-stage single-well injection and pumping test; The optimization objective function is solved to generate heat transfer parameter values ​​of the target fractured aquifer.

9. The method according to claim 8, characterized in that The optimization objective function is constructed based on the analytical solution of the three-stage single well injection and pumping test and with the goal of minimizing the fitting value of the three-stage single well injection and pumping test, including: Determine the simulation value of the sampling point based on the analytical solution of the three-stage single well injection and pumping test; Obtaining the observed value of the sampling point, and determining the mean square error value of the three-stage single well injection and pumping test based on the simulated value of the sampling point and the observed value of the sampling point; The weighting coefficient of the three-stage single-well injection and pumping test is obtained, and the optimization objective function is constructed based on the mean square error value of the three-stage single-well injection and pumping test and the weighting coefficient of the three-stage single-well injection and pumping test.

10. The method according to claim 9, characterized in that The optimization objective function is constructed based on the mean square error value of the three-stage single-well injection and pumping test and the weighted coefficient of the three-stage single-well injection and pumping test. The expression of the optimization objective function is as follows: In the above formula, F represents the optimization objective function, μ i represents the weighting coefficient of the i-th stage, Δf i represents the mean square error value of the i-th stage, and u represents the number of stages in the single-well injection and pumping test.

11. The method according to claim 2, characterized in that Also includes: The heat transfer parameter value of the target fractured aquifer is compared with the range of the geothermal heat transfer parameter, and when the heat transfer parameter value of the target fractured aquifer meets the range of the geothermal heat transfer parameter, the heat transfer parameter value of the target fractured aquifer is output.

12. A device for inverting heat transfer parameters of fractured aquifers considering the thermal mixing process of wellbore, characterized in that: The device comprises: An acquisition module is used to acquire the target area drilling data and the target area hydrogeological data, and carry out a three-stage single well injection and pumping test based on the target area drilling data and the target area hydrogeological data to determine the influencing parameters of the wellbore thermal mixing process; A construction module, used to construct a mathematical model of a single well injection and pumping test considering the wellbore thermal mixing process based on the influencing parameters of the wellbore thermal mixing process; A solution module, used for solving the mathematical model of the single-well injection and pumping test considering the wellbore thermal mixing process, and generating an analytical solution for the three-stage single-well injection and pumping test; An inversion module is used to construct an optimization objective function based on the analytical solution of the three-stage single well injection and pumping test, and use the optimization objective function to perform parameter inversion to generate a heat transfer parameter value of a target fractured aquifer; wherein the heat transfer parameter value of the target fractured aquifer is used to evaluate geothermal resources; Building blocks, including: The first construction submodule is used to respectively construct an injection phase mixing effect model, a rest phase mixing effect model and an extraction phase mixing effect model based on the influencing parameters of the wellbore thermal mixing process; The second construction submodule is used to construct a control equation based on the influencing parameters of the wellbore thermal mixing process; wherein the control equation includes a fracture medium heat transfer kinetic equation and a bedrock medium heat transfer kinetic equation; A third determination submodule is used to determine initial conditions and boundary conditions based on influencing parameters of the wellbore thermal mixing process; a fourth determination submodule, for determining an effective thermal diffusion coefficient based on an influencing parameter of a wellbore thermal mixing process; The third construction submodule is used to construct a mathematical model of a single-well injection and extraction test considering the wellbore thermal mixing process based on the heat transfer kinetic equation, initial conditions, boundary conditions, effective thermal diffusion coefficient, injection stage mixing effect model, rest stage mixing effect model and extraction stage mixing effect model.

13. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for inverting thermal transport parameters of a fractured aquifer considering a wellbore thermal mixing process as described in any one of claims 1 to 11 by executing the computer instructions.

14. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions for causing a computer to execute the method for inverting heat transport parameters of a fractured aquifer considering a wellbore thermal mixing process according to any one of claims 1 to 11.

Images