Coupling characterization method for multi-component variable mass fluid in shaft

Abstract

The invention discloses a coupling characterization method for multi-component variable mass fluid in a shaft. The coupling characterization method comprises the following steps: establishing a gas component-thermophysical property dynamic incidence matrix; through thermodynamic coupling calculation, the influence of the reaction process on the flow in the shaft is dynamically reflected; establishing a three-dimensional shaft control body, and simultaneously establishing a variable mass continuity equation, a momentum conservation equation and an energy conservation equation; boundary conditions are set, meanwhile, distributed heat source items are embedded in catalytic reaction sites, local component mass source items are synchronously updated, and a constraint system conforming to actual working conditions is provided for equation solving; and adopting an SIMPLER algorithm, carrying out iterative calculation through an iterative strategy until the residual error of the energy equation and the component transport equation meets the requirement, outputting the on-way temperature field and pressure field data of the shaft, and generating a dynamic map. According to the method, the complex conditions of variable temperature, variable pressure and variable components in the shaft can be responded in real time, and high-fidelity depiction of the real physical and chemical process can be achieved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and in particular to a method for characterizing multi-component variable mass fluid coupling in a wellbore. Background Technology

[0002] In advanced processes such as catalytic cracking for enhanced oil production, carbon dioxide injection for enhanced oil recovery and storage, enhanced geothermal systems (EGS), and downhole in-situ conversion, the wellbore is not only a conduit for fluids but also a critical site for complex multiphase chemical reactions and energy exchange. Accurately predicting the temperature, pressure, and component concentration distribution along the wellbore is crucial for optimizing process design, improving reaction efficiency, assessing equipment safety, and accurately predicting production capacity.

[0003] Traditionally, simplified or decoupled models are often used for the analysis of wellbore flow and heat transfer. In terms of implementation methods, they mainly include: (1) Empirical formulas and steady-state analytical models: Based on simple energy balance equations and Darcy flow formulas, average physical property parameters are used for estimation, which cannot handle dynamic processes where physical properties change drastically with temperature, pressure and composition. (2) Computational fluid dynamics (CFD) single-field or dual-field simulation: Although some studies use CFD software to simulate wellbore flow or heat transfer, fluid physical properties are usually set as constants, or only the simple effects of temperature and pressure are considered, failing to deeply couple chemical reactions as mass and energy source terms into the governing equations. (3) Segmented or separate simulation: The flow, heat transfer and chemical reaction processes are calculated separately, or only the chemical reaction is regarded as a simple heat source addition term, ignoring the real-time and interactive effects of the reaction process on fluid composition, physical properties and flow state, and the ability to handle multiple discrete heat sources is insufficient. Summary of the Invention

[0004] The purpose of this invention is to provide a coupling characterization method for multi-component variable-mass fluids within wellbores, addressing the core technical problem in existing technologies where the complex flow, heat transfer, and mass transfer coupling processes of multi-component variable-mass fluids under the influence of multiple chemical reaction heat sources are inaccurately characterized due to model simplification, incomplete coupling, and insufficient verification. Specifically, it overcomes the shortcomings of traditional methods, which use fixed physical property parameters leading to low fidelity under variable temperature and pressure conditions. It also solves the problem of incomplete physical mechanism characterization caused by the failure to uniformly construct multi-field coupling control equations that include chemical reaction mass and energy source terms. Furthermore, it compensates for the insufficient reliability of prediction results due to the lack of systematic gradient experimental verification loops.

[0005] This invention is achieved using the following technical solution: a method for characterizing multi-component variable-mass fluid coupling in a wellbore, comprising the following steps: Establish a dynamic correlation matrix between gas components and thermophysical properties; Thermodynamic coupling calculations are used to dynamically reflect the impact of the reaction process on the flow inside the wellbore. Establish a three-dimensional wellbore control volume and simultaneously solve the variable mass continuity equation, momentum conservation equation, and energy conservation equation; By setting boundary conditions and embedding distributed heat source terms at the catalytic reaction sites and updating local component mass source terms simultaneously, a constraint system that conforms to actual working conditions is provided for solving the equations. The SIMPLER algorithm is adopted, and through an iterative strategy, the residuals of the energy equation and the component transport equation are calculated until they meet the requirements. The temperature and pressure field data along the wellbore are output and dynamic maps are generated, so as to realize efficient simulation and accurate prediction of the coupled process in the wellbore.

[0006] Furthermore, the establishment of the dynamic correlation matrix between gas components and thermophysical properties specifically involves: real-time acquisition of wellhead injection parameters and chemical reaction parameters, combined with experimental measurements or correlation of thermophysical property parameters of each component under varying temperature and pressure conditions using a property database, to establish the dynamic correlation matrix between gas components and thermophysical properties.

[0007] Furthermore, the wellhead injection parameters include one or more of the following: initial gas component mole fraction, mass flow rate, temperature, and pressure; The chemical reaction parameters include the activation energy, the rate constant, the heat source intensity distribution at each catalytic reaction site, and the mapping relationship of the reaction product components.

[0008] Furthermore, the method of dynamically reflecting the impact of the reaction process on the flow within the wellbore through thermodynamic coupling calculations specifically involves: calculating the fugacity and compressibility factor of the mixed gas based on the actual gas state equation and mixing rules, correcting the equivalent density and viscosity of the multi-component fluid, introducing reaction process variables, dynamically updating the reaction heat source term according to the Arrhenius equation, calculating the rate of change of component mole fraction, and simultaneously solving for the vapor partial pressure and latent heat transfer of phase change, thereby dynamically reflecting the impact of the reaction process on the flow within the wellbore.

[0009] Furthermore, the calculation formula for the variable mass continuity equation is: ; in, Where A is the equivalent density and A is the flow cross-sectional area. The component mass source term resulting from chemical reaction, For local time derivative, It is a divergence operator.

[0010] Furthermore, the equation for the conservation of momentum is calculated as follows: ; in, Where is the equivalent density, and u is the fluid velocity. For divergence operators, For the viscosity of mixed fluids, For the momentum source term of chemical reaction, Let be the velocity tensor.

[0011] Furthermore, the energy conservation equation is calculated as follows: ; in, For equivalent density, For divergence operators, This is a viscous dissipation term. The mole fraction of steam. For latent heat of phase transition, For the heat source term of the reaction, Let T be the thermal conductivity of the mixed fluid, and T be the fluid temperature.

[0012] Furthermore, the setting of boundary conditions, and the embedding of distributed heat source terms at the catalytic reaction site while simultaneously updating local component mass source terms to provide a constraint system that conforms to actual operating conditions for solving the equations, specifically involves: based on the constructed multi-field coupled control equations, setting the wellbore inlet to a Dirichlet condition with fixed temperature, pressure, and component mole fraction, and setting the outlet to a Neumann condition where pressure, temperature, and component concentration gradients are all 0; simultaneously embedding distributed heat source terms at the catalytic reaction site while simultaneously updating local component mass source terms to provide a constraint system that conforms to actual operating conditions for solving the equations.

[0013] Furthermore, the iterative strategy includes a finite volume scheme for discrete equations, a second-order upwind scheme for spatial grids, pressure correction to incorporate the actual gas compressibility factor, and an adaptive time step for the chemical reaction site grid.

[0014] Furthermore, the iterative calculation until the residuals of the energy equation and the component transport equation meet the requirements specifically means: iterative calculation until the residuals of the energy equation are satisfied. Component transport equation residuals Finally, the temperature field, pressure field, component concentration distribution, and vapor partial pressure along the wellbore are output, generating a dynamic spectrum of flow-heat and mass transfer under multi-heat source coupling.

[0015] The beneficial effects of this invention are as follows: This invention establishes a dynamic correlation matrix between gas components and thermophysical properties through dynamic acquisition and preprocessing of multi-source data and coupled calculation of thermodynamic parameters, and introduces reaction process variables. Its effect is that it completely changes the limitations of traditional models using fixed property parameters, enabling real-time response to complex conditions of varying temperature, pressure, and composition within the wellbore. This provides a dynamic parameter basis for the accuracy of the core flow-heat transfer model, achieving a high-fidelity characterization of real physicochemical processes.

[0016] This invention constructs a multi-field coupled control equation system that includes a variable mass continuity equation, a momentum conservation equation, and an energy conservation equation, and innovatively sets mixed boundary conditions (inlet Dirichlet, outlet Neumann) that conform to physical reality. It mathematically and uniformly describes the coupling mechanism of "flow-heat transfer-mass transfer-chemical reaction". In particular, it accurately embeds distributed heat source terms and component mass source terms, which solves the key technical bottleneck that traditional single or dual-field models cannot predict the influence of reaction heat sources on flow and mass transfer in principle.

[0017] This invention employs the SIMPLER algorithm combined with advanced numerical strategies such as actual gas compressibility factor correction and adaptive time step. This significantly improves the solution stability and convergence speed of strongly nonlinear coupled equations. The final output, high-resolution temperature field, pressure field, and component concentration distribution maps, provides a quantitative and visualized accurate prediction tool for engineering design (such as reactor placement and injection / production parameter optimization), reducing the trial-and-error costs and risks of field experiments. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0019] Figure 1 This is a flowchart of the present invention; Figure 2 Construct a logical relationship diagram for the multi-field coupled control equations; Figure 3 This is a graph showing the temperature change with and without a reactor. Figure 4 A graph showing the effect of displacement on the temperature inside the tube, in the tubing, and in the annulus. Figure 5 This is a graph showing the effect of reactor length on the temperature inside the tube, in the tubular column, and in the annulus. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] See Figure 1 , Figure 2 A method for characterizing multi-component variable-mass fluid coupling in a wellbore includes the following steps: Step 1: By collecting wellhead injection parameters and chemical reaction parameters in real time, and combining experimental measurements or physical property databases to associate the thermophysical parameters of each component under variable temperature and pressure conditions, a dynamic correlation matrix of gas components and thermophysical properties is established. Step 2: Based on the actual gas state equation and mixing law, calculate the fugacity and compressibility factor of the mixed gas and correct the equivalent density and viscosity of the multi-component fluid. Introduce reaction process variables, dynamically update the reaction heat source term according to the Arrhenius equation, calculate the change rate of component mole fraction, and simultaneously solve the vapor partial pressure and latent heat transfer of phase change to dynamically reflect the influence of the reaction process on the flow in the wellbore. Step 3: Based on the preprocessed basic data and the thermodynamic parameters calculated in Step 2, establish a three-dimensional wellbore control volume and simultaneously establish the variable mass continuity equation, momentum conservation equation, and energy conservation equation. Step 4: Based on the constructed multi-field coupled control equations, the wellbore inlet is set to the Dirichlet condition with fixed temperature, pressure and component mole fraction, and the outlet is set to the Neumann condition with pressure, temperature and component concentration gradients of 0. At the same time, a distributed heat source term is embedded in the catalytic reaction site and the local component mass source term is updated synchronously to provide a constraint system that conforms to the actual working conditions for solving the equations. Step 5: Using the SIMPLER algorithm, the equations are discretized using a finite volume scheme, a second-order upwind scheme for spatial grids, pressure correction to introduce the actual gas compressibility factor, and an adaptive time step for the chemical reaction site grid. The calculation is iterated until the residuals of the energy equation and the component transport equation meet the requirements. Key data such as the temperature field and pressure field along the wellbore are output and dynamic maps are generated, achieving efficient simulation and accurate prediction of the coupled processes within the wellbore.

[0024] In this embodiment, the wellhead injection parameters include the initial gas component mole fraction. mass flow rate ,temperature ,pressure Chemical reaction parameters include the activation energy of the reaction. Reaction rate constant Heat source intensity distribution at each catalytic reaction site The mapping relationship between the reaction product components was also established. In the experiment, the density of each component under varying temperature and pressure conditions was determined by measurement or correlated with a physical property database. Specific heat capacity thermal conductivity and latent heat of phase transition Using these data, a dynamic correlation matrix of gas components and thermophysical properties is established, thereby providing time-varying parameter inputs for subsequent variable mass flow equations and ensuring the model's response to physical properties under varying temperature and pressure conditions.

[0025] By acquiring wellhead injection parameters (initial gas component mole fraction, mass flow rate, temperature, pressure, etc.) and chemical reaction parameters (reaction activation energy, reaction rate constant, etc.) in real time, and combining experimental measurements or correlation with thermal property parameters such as density and specific heat capacity of each component under variable temperature and pressure conditions with physical property databases, a dynamic correlation matrix of gas components and thermal properties is established. This provides time-varying parameter input for subsequent variable mass flow equations, ensuring that the model can accurately respond to changes in physical properties under variable temperature and pressure environments. It also provides reliable and comprehensive basic data support for the coupled characterization of flow-heat and mass transfer in the wellbore of a multi-component variable mass multi-point heat source well.

[0026] In this embodiment, step two specifically involves: thermodynamic parameter coupling calculation, based on the actual gas law, to calculate the fugacity of the mixed gas. and compression factor By combining the mixing principle, the equivalent density of multi-component fluids is corrected. and viscosity Introducing reaction process variables It is used to characterize the direction along the well depth. The extent of the chemical reaction. Based on the Arrhenius equation, the reaction heat source term is dynamically updated. And calculate the rate of change of component mole fraction. Simultaneously, the vapor partial pressure is calculated. And the latent heat transfer of phase change. Through these thermodynamic coupling calculations, the influence of the reaction process on the flow inside the wellbore can be dynamically reflected, ensuring accurate simulation of temperature, pressure and reactants.

[0027] Based on the actual gas state equation and mixing rules, the fugacity and compressibility factor of the mixed gas are accurately calculated, the equivalent density and viscosity of the multi-component fluid are corrected, and reaction process variables are introduced. The reaction heat source term is dynamically updated according to the Arrhenius equation, the change rate of component mole fraction is calculated, and the vapor partial pressure and latent heat transfer of phase change are solved simultaneously. In this way, the influence of the degree of chemical reaction along the well depth on the flow in the wellbore is dynamically captured.

[0028] In this embodiment, step three specifically involves: constructing multi-field coupled control equations, establishing a three-dimensional wellbore control volume, and simultaneously solving the following set of partial differential equations: Equation of continuity with varying mass: .

[0029] Momentum conservation equation: .

[0030] Energy conservation equation: .

[0031] Where t is time, a time variable in state simulation, characterizing the instantaneous nature of the process, and its unit is seconds (s). z represents the well depth, a spatial coordinate along the wellbore axis, and its value range in the experimental scheme is 0-1000m. The density of the mixed fluid is the equivalent density of the multi-component gas mixture, which is obtained by combining the actual gas law and mixing rules in step two. A is the flow cross-sectional area, the effective cross-sectional area for fluid flow inside the wellbore, with fixed geometric parameters; u represents the fluid velocity, the velocity vector of the mixed fluid along the wellbore axis; P is the fluid pressure, the static pressure of the mixed fluid inside the wellbore; The viscosity of the mixed fluid is the equivalent dynamic viscosity of the multi-component gas mixture, which is corrected by the mixing rule in step two. Specific heat capacity at constant pressure for a mixed fluid; specific heat capacity of a multi-component mixture under constant pressure conditions. T represents the fluid temperature, specifically the thermodynamic temperature of the mixed fluid inside the wellbore. The thermal conductivity of the mixed fluid is the equivalent thermal conductivity of a multi-component mixture, which is obtained by relating it to the thermophysical parameters of the components. The component mass source term is caused by chemical reaction, and the component mass change rate caused by catalytic reaction in the wellbore is the core parameter characterizing the variable mass characteristics. For velocity tensor, the outer product of fluid velocities, used to describe the spatial distribution characteristics of the velocity field; The momentum source term of a chemical reaction refers to the force exerted on fluid flow by the momentum change generated during a chemical reaction. This refers to the heat source term, which is the heat source term released or absorbed by the catalytic reaction; This is a viscous dissipation term, where energy generated by viscous friction during fluid flow is dissipated and converted into heat; It is the mole fraction of steam; Latent heat of phase change is the latent heat of the vapor phase components when they undergo a phase change (condensation or vaporization). The local time derivative represents the instantaneous rate of change of a physical quantity over time; It is a divergence operator.

[0032] By establishing a three-dimensional wellbore control volume and simultaneously establishing the variable mass continuity equation, momentum conservation equation, and energy conservation equation, key physical processes such as mass change, flow momentum transfer, heat transfer, and chemical reaction effects of multi-component fluids are incorporated into a unified partial differential equation system. The system integrates the basic data preprocessed in step one with the thermodynamic parameters calculated in step two, accurately characterizing the interaction mechanism between variable mass characteristics, fluid flow, heat and mass transfer, and chemical reactions within the wellbore, thus achieving a comprehensive and accurate description of the complex coupled processes of multi-component variable mass multi-point heat source wellbores.

[0033] In this embodiment, step four specifically involves: setting the boundary conditions and heat source coupling, and setting the wellbore inlet boundary as a Dirichlet condition: ; The exit boundary location is defined as the well depth z=L (L=1000m in the experimental scheme, the general form is z=L), and the Neumann conditions for each key physical quantity are as follows: Pressure boundary conditions: ; The rate of change of pressure at the outlet along the well depth is 0, meaning the outlet pressure remains stable and there is no additional pressure gradient driving it.

[0034] Temperature boundary conditions: ; The energy conservation equation involves multiple couplings such as heat conduction, viscous dissipation, and latent heat of phase change. The outlet temperature is determined by the heat transfer-reaction coupling process in the wellbore, without the need for additional mandatory constraints. Setting the temperature gradient to 0 means that the outlet temperature no longer changes along the well depth, which is consistent with the "steady state" logic of the pressure boundary conditions and avoids the abrupt change in outlet temperature from disrupting the coupled solution of the energy equation.

[0035] Component concentration boundary conditions: ; ( (These are the various gaseous components, such as CO2, CH4, etc.) The component concentration is determined by the reaction process variables in step two, the rate of change of component mole fraction, and the transport equation in step three. The chemical reaction at the outlet has stabilized, and the component concentration no longer changes along the well depth. Setting the concentration gradient to 0 matches the gradient constraint nature of the Neumann condition and forms a complete constraint with the Dirichlet condition at the inlet, ensuring the convergence of the component transport equation.

[0036] At the catalytic reaction site ( At this location, a distributed heat source item is embedded. And simultaneously update the local component quality source items. .

[0037] The purpose of setting the boundary conditions and heat source coupling in step four is to provide a scientific and practical constraint system for the multi-field coupled control equations constructed in step three. By setting the wellbore inlet to a Dirichlet condition with fixed temperature, pressure, and component mole fraction, the initial input boundary is clarified. The outlet is set to a Neumann condition where the pressure, temperature, and component concentration gradients are all zero, which fits the actual scenario where the chemical reaction and physical quantities at the outlet tend to be stable. At the same time, a distributed heat source term is embedded in the catalytic reaction site and the local component mass source term is updated synchronously to achieve a precise connection between the reaction heat source and the physical model, ensuring both the convergence and mathematical rationality of the partial differential equation solution.

[0038] In this embodiment, step 5 specifically involves: numerical solution of the coupled equations and generation of the temperature and pressure field. The SIMPLER algorithm is used for pressure-velocity coupled solution, and the following iterative strategy is introduced: The equations from step three are discretized into a finite volume scheme, and a second-order upwind scheme is used on the spatial grid; the pressure correction stage incorporates the actual gas compressibility factor. Correct the continuity equation residuals; employ an adaptive time step in the chemical reaction site grid to capture reaction mutations; iterate until the energy equation residuals are corrected. Component transport equation residuals Temperature field along the output shaft Pressure field Component concentration distribution and vapor partial pressure This process generates dynamic flow-heat and mass transfer maps under multi-heat source coupling. Through these steps, the heat transfer, mass transfer, and reaction processes of flow within the wellbore can be efficiently simulated and predicted, providing more accurate analysis for engineering applications.

[0039] To verify the effectiveness of the coupling characterization method proposed in this scheme, a comparative experiment on wellbore flow-heat transfer with and without a downhole reactor was designed. The specific experimental procedure is as follows: S1. Experimental Preparation: Match the input parameters of the scheme. According to the multi-source data acquisition requirements of step 1 of the scheme, the wellhead injection parameters are fixed in the experiment: initial gas component mole fraction (xi), mass flow rate G0=20kg / s, inlet temperature T0=250℃, and inlet pressure P0=30MPa; obtain the thermophysical parameters such as ρi, cp,i of each component (such as CO2 and CH4) under variable temperature and pressure through the physical property database, and establish the component-thermal property correlation matrix; install the catalytic reactor in the 600-900m well section, and set the reaction activation energy Ea=80kJ / mol and the heat source intensity distribution of the reaction site Qreact(z).

[0040] S2. Experimental Condition Setup: Based on the boundary and heat source coupling of the control scheme, and following the boundary and heat source setup in step four of the control scheme, two experimental conditions are set up: Condition 1 (no reactor): No heat source is embedded in the wellbore; the inlet is under Dirichlet conditions (T|z=0=250℃, P|z=0=30MPa); the outlet is under Neumann conditions. Operating Condition 2 (with reactor): Embed a distributed heat source project in the 600-900m well section. The remaining boundary conditions are the same as in case 1.

[0041] S3. Experimental Data Acquisition: Corresponding to the numerical solution output items of the scheme, temperature sensors were deployed along the well depth (0-1000m) to collect real-time data on the fluid temperature inside the tubing and the annulus fluid temperature; a component analyzer and pressure sensor were set at the bottom of the well (1000m) to record the final temperature and component concentration distribution—the collected results are compiled into Appendix Figure 3 (Including temperature profiles with and without reactor, and wellbore temperature and pressure field diagrams).

[0042] S4. Experimental Results Verification: The accuracy of the scheme coupling method is verified by experimental results as follows: Figure 3 As shown: Referring to the "Reaction Heat Source Term Sh(z,t)" in step two of the control scheme: In operating condition 2, the 600-900m reactor well section... The release of heat raises the bottom-hole temperature from 174℃ in operating condition 1 to 248℃, a temperature difference of 74℃, which is consistent with the plan. The calculation rules for the heat source term driven by the reaction process are completely consistent.

[0043] Compare the multi-field coupling equations in step three of the scheme: (Appendix) Figure 3 The coordinated change in the temperature of the tubing and annulus matches the coupling effect of the "continuity equation-momentum equation-energy equation" in the scheme. In comparison with the "generation of temperature and pressure field" in step five of the scheme, the temperature field map of the wellbore in the attached figure is completely consistent with the distribution trend and quantification results of the temperature field T(z) along the friction path output by the numerical solution of the scheme.

[0044] like Figure 3 As shown, the rationality of the entire process from "data acquisition - parameter coupling - equation construction - numerical solution" is verified: the reaction heat source term in the scheme The dynamic calculation, multi-field coupled control equations, and multi-point heat source boundary settings can accurately reproduce the flow-heat and mass transfer laws of actual wellbores, providing experimental support for the engineering application of multi-component variable mass multi-point heat source wellbores.

[0045] To verify the accuracy of this scheme in characterizing the coupling law of wellbore heat and mass transfer under different reaction intensities in a multi-component variable mass system, a wellbore flow-heat transfer comparison experiment under gradient reaction intensities was designed. The specific experimental procedure is as follows: S11. Experimental Preparation: Match the parameter system and experimental conditions of the scheme. According to the "dynamic acquisition of multi-source data" requirement in step 1 of the scheme, the basic parameters of the experiment are fixed: mole fraction of gas components injected at the wellhead (such as CO2, CH4 and other components), inlet temperature 250℃, and inlet pressure 30MPa; obtain the density, specific heat capacity and other thermophysical parameters of each component under variable temperature and pressure through the physical property database, and establish a "component-thermal property correlation matrix"; retain a reactor with a fixed heat source intensity in the 600-900m well section to ensure that the heat source conditions are consistent and only the injection displacement variable is changed.

[0046] S12. Control test under gradient displacement: Refer to step four of the scheme for boundary condition settings. Set up 3 groups of gradient displacement conditions in the experiment: Operating condition 1: Injection displacement 100t / d, inlet condition is Dirichlet condition, outlet condition is Neumann condition; Operating Condition 2: Injection displacement 150t / d, other boundary and heat source conditions are the same as those in Operating Condition 1; Operating Condition 3: Injection rate 200t / d, maintaining constant boundary and heat source conditions. By controlling a single variable (discharge rate), the independent impact on the wellbore temperature field is focused.

[0047] S13. Experimental Data Acquisition: The output requirements of the synchronous matching scheme are as follows: Temperature sensors are deployed along a 1000m well depth to collect the temperature distribution along the pipe, tubing string, and annular fluid. A high-precision temperature probe is set at the bottom of the well (1000m) to record the bottom-hole fluid temperature at different discharge rates. Simultaneously, radial temperature field data corresponding to different discharge rates is obtained through radial temperature measuring points in the wellbore. All collected data, after preprocessing, are organized into the appendix. Figure 4 The “Temperature Curves of the Tube / Tube Column / Annulus” and “Radial Temperature Field Map” are shown.

[0048] S14. Experimental results, such as Figure 4As shown, when the discharge rate increases from 100 t / d to 200 t / d, the bottom hole fluid temperature rises from 248℃ to 249℃, which is consistent with the coupling law of "the influence of mass flow rate G0 on ρmix and u in the variable mass continuity equation and the change of the transport term of ρmixcp,mixu・∇T in the energy conservation equation" in this scheme; at the same time, the "coordinated change trend of in-pipe-pipeline-annulus temperature" in the attached figure matches the response characteristics of the multi-field coupled control equation of the scheme to the discharge rate parameter, proving the accuracy of the scheme's characterization of the correlation law of "injection discharge rate-heat and mass transfer".

[0049] To verify the accuracy of this scheme in characterizing the coupling between reactor length gradient change and wellbore heat and mass transfer in a multi-component variable mass system, a comparative experiment on wellbore flow-heat transfer under gradient reactor length was designed. The specific experimental procedure is as follows: S21. Experimental Preparation: Anchoring Scheme Parameter System and Fixed Variables Based on the "multi-source data acquisition requirements" in step one of the scheme, the experiment fixed the core basic parameters: mole fraction of the injected gas components at the wellhead, inlet temperature of 250℃, inlet pressure of 30MPa, and injection rate of 150t / d; the thermal properties of each component under varying temperature and pressure were obtained through the physical property database, and a "component-thermal property dynamic correlation matrix" was established; the upper end of the reactor was fixed at a well depth of 600m, and only the reactor length was adjusted as the experimental variable to ensure that other operating conditions were consistent with the settings in step four of the scheme.

[0050] S22. Experimental Design: Comparative Test of Gradient Reactor Length. Referring to Step 4 of the scheme, "Multi-point Heat Source Coupling Setup", the experiment sets up 3 groups of gradient reactor length conditions: Operating Condition 1: Reactor length 100m (covering a 600-700m well section), embedded with a distributed heat source project. ; Operating Condition 2: Reactor length 200m (covering a 600-800m well section), maintaining the same heat source intensity distribution as in Operating Condition 1; Operating Condition 3: Reactor length 300m (covering a well section of 600-900m), heat source intensity distribution remains constant. By controlling a single variable, namely the reactor length, the focus is on its spatial regulation effect on the wellbore temperature field.

[0051] S23. Experimental Data Acquisition: Output Requirements of the Synchronous Matching Scheme An array of temperature sensors was deployed along a 1000m well depth to collect the temperature variations of the fluid inside the pipe, the tubing string, and the annular fluid. A high-precision temperature probe was installed at the bottom of the well at 1000m to record the bottom fluid temperature for different reactor lengths. Simultaneously, radial temperature field data for each operating condition was obtained through radial temperature measurement points in the wellbore. The collected data, after preprocessing, were organized into the appendix. Figure 5The “Temperature Curves of the Tube / Tube Column / Annulus” and “Radial Temperature Field Map” are shown.

[0052] S24. Experimental Results Verification: Coupling Law of Matching Schemes Experimental results, such as Figure 5 As shown, when the reactor length increases from 100m to 300m, the bottom fluid temperature rises from 232℃ to 248℃, an increase of 6.9%, which is consistent with the "reactor length expansion → heat source item" in the plan. The coupling law of "extending the well section → increasing the cumulative contribution of Sh in the energy conservation equation" is completely consistent with the above. At the same time, the "coordinated increase trend of temperature in the tube-tube string-annulus" in the attached figure matches the response characteristics of the "multi-field coupling control equation" of the scheme to the spatial distribution of heat source, proving the accuracy of the scheme's characterization of the correlation law of "reactor length-heat and mass transfer".

[0053] For the foregoing embodiments, in order to simplify the description, they are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to this application.

[0054] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the invention should be within the protection scope of the appended claims.

Claims

1. A method for characterizing multi-component variable-mass fluid coupling within a wellbore, characterized in that, Includes the following steps: Establish a dynamic correlation matrix between gas components and thermophysical properties; Thermodynamic coupling calculations are used to dynamically reflect the impact of the reaction process on the flow inside the wellbore. Establish a three-dimensional wellbore control volume and simultaneously solve the variable mass continuity equation, momentum conservation equation, and energy conservation equation; By setting boundary conditions and embedding distributed heat source terms at the catalytic reaction sites and updating local component mass source terms simultaneously, a constraint system that conforms to actual working conditions is provided for solving the equations. The SIMPLER algorithm is adopted, and through an iterative strategy, the residuals of the energy equation and the component transport equation are calculated until they meet the requirements. The temperature and pressure field data along the wellbore are output and dynamic maps are generated, so as to realize efficient simulation and accurate prediction of the coupled process in the wellbore.

2. The method for characterizing multi-component variable-mass fluid coupling in a wellbore as described in claim 1, characterized in that, The establishment of the dynamic correlation matrix between gas components and thermophysical properties is specifically achieved by: collecting wellhead injection parameters and chemical reaction parameters in real time, and combining experimental measurements or property databases to correlate the thermophysical parameters of each component under varying temperature and pressure conditions, thereby establishing the dynamic correlation matrix between gas components and thermophysical properties.

3. The method for characterizing multi-component variable-mass fluid coupling in a wellbore as described in claim 2, characterized in that, The wellhead injection parameters include one or more of the following: initial gas component mole fraction, mass flow rate, temperature, and pressure; The chemical reaction parameters include the activation energy, the rate constant, the heat source intensity distribution at each catalytic reaction site, and the mapping relationship of the reaction product components.

4. The method for characterizing multi-component variable-mass fluid coupling in a wellbore as described in claim 1, characterized in that, The method of dynamically reflecting the impact of the reaction process on the flow inside the wellbore through thermodynamic coupling calculations is as follows: Based on the actual gas state equation and mixing law, the fugacity and compressibility factor of the mixed gas are calculated, and the equivalent density and viscosity of the multi-component fluid are corrected. The reaction process variable is introduced, and the reaction heat source term is dynamically updated according to the Arrhenius equation. The change rate of component mole fraction is calculated, and the vapor partial pressure and latent heat transfer of phase change are solved simultaneously to dynamically reflect the impact of the reaction process on the flow inside the wellbore.

5. The method for characterizing multi-component variable-mass fluid coupling in a wellbore as described in claim 1, characterized in that, The formula for calculating the variable mass continuity equation is: ； in, Where A is the equivalent density and A is the flow cross-sectional area. The component mass source term resulting from chemical reaction, For local time derivative, It is a divergence operator.

6. The method for characterizing multi-component variable-mass fluid coupling in a wellbore as described in claim 1, characterized in that, The equation for the conservation of momentum is calculated as follows: ； in, Where is the equivalent density, and u is the fluid velocity. For divergence operators, For the viscosity of mixed fluids, For the momentum source term of chemical reaction, Let be the velocity tensor.

7. The method for characterizing multi-component variable-mass fluid coupling in a wellbore as described in claim 1, characterized in that, The formula for calculating the energy conservation equation is: ； in, For equivalent density, For divergence operators, This is a viscous dissipation term. The mole fraction of steam. For latent heat of phase transition, For the heat source term of the reaction, Let T be the thermal conductivity of the mixed fluid, and T be the fluid temperature.

8. The method for characterizing multi-component variable-mass fluid coupling in a wellbore as described in claim 1, characterized in that, The specific steps for setting boundary conditions, embedding distributed heat source terms at the catalytic reaction site, and synchronously updating local component mass source terms to provide a constraint system that conforms to actual operating conditions for solving the equations are as follows: Based on the constructed multi-field coupled control equations, the wellbore inlet is set to a Dirichlet condition with fixed temperature, pressure, and component mole fraction, while the outlet is set to a Neumann condition where pressure, temperature, and component concentration gradients are all 0. Simultaneously, a distributed heat source term is embedded at the catalytic reaction site, and the local component mass source terms are synchronously updated to provide a constraint system that conforms to actual operating conditions for solving the equations.

9. The method for characterizing multi-component variable-mass fluid coupling in a wellbore as described in claim 1, characterized in that, The iterative strategy includes a finite volume scheme for discrete equations, a second-order upwind scheme for spatial grids, pressure correction to incorporate a real gas compressibility factor, and an adaptive time step for the chemical reaction site grid.

10. The method for characterizing multi-component variable-mass fluid coupling in a wellbore as described in claim 1, characterized in that, The iterative calculation until the residuals of the energy equation and the component transport equation meet the requirements specifically means: iterative calculation until the residuals of the energy equation are satisfied. Component transport equation residuals Finally, the temperature field, pressure field, component concentration distribution, and vapor partial pressure along the wellbore are output, generating a dynamic spectrum of flow-heat and mass transfer under multi-heat source coupling.

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