Rock core seepage heat exchange dynamic coupling simulation system based on outlet temperature feedback

Abstract

The invention relates to a rock core seepage heat exchange dynamic coupling simulation system based on outlet temperature feedback. The system comprises a multi-medium precise injection system, a gradient temperature control rock core clamping system, an outlet multi-dimensional information sensing system, a dynamic coupling central control system and a pressure compensation and circulation backflow system. The central control system receives feedback signals of the outlet end and adjusts injection power and an axial gradient temperature control area in real time, and deep dynamic coupling of a seepage field, a temperature field and a stress field is achieved. The problems that a traditional experiment is constant in injection temperature and lacks outlet feedback are solved, real stratum temperature scale distribution can be accurately reconstructed, the physical fidelity and data reliability of a heat exchange coupling experiment are remarkably improved, and an advanced experiment supporting platform is provided for basic mechanism research in the field of energy development.

Description

Technical Field

[0001] This invention belongs to the field of petroleum geological exploration and core experiment simulation technology, specifically involving a core seepage heat transfer dynamic coupling simulation system based on outlet temperature feedback. Background Technology

[0002] In the fields of energy development, geothermal extraction, and underground reservoir engineering, core flow experiments are a fundamental method for revealing the transport laws and evolution mechanisms of multiphase fluids in porous media. High-precision experimental simulations can recreate the complex physicochemical processes of underground reservoirs, providing crucial data support for resource assessment and optimization of extraction schemes. With the increasing scale of deep and ultra-deep resource development, the study of fluid transport behavior under extreme temperature and pressure environments is becoming increasingly important. This requires simulation systems to possess high physical fidelity to accurately capture the dynamic evolution characteristics of complex underground flow fields.

[0003] Among these, dynamic coupled simulation of heat transfer during core seepage is a core technical aspect for evaluating thermal oil recovery, geothermal circulation, and the heat response induced by fluid injection. This research focuses on the heat transfer between fluids and the solid framework during fluid flow in porous media and its impact on seepage characteristics. By constructing a controlled temperature field environment, it aims to explore the regulatory role of thermodynamic parameter changes on fluid flow behavior. Accurate coupled heat transfer simulation has crucial academic and engineering significance for understanding energy conversion, pressure decay, and phase evolution processes.

[0004] However, most existing core seepage experimental setups employ a fixed-temperature injection mode and rely on the idealized assumption of an isothermal boundary condition outside the core. Typically, only an external heating jacket or a constant-temperature water bath is used to uniformly heat the clamp. Such systems neglect the widespread natural temperature gradients present in actual formations and fail to reflect the temperature rise or fall effects caused by continuous heat exchange between the injected fluid and the rock during seepage. Due to the lack of real-time sensing and feedback mechanisms for the outlet fluid state, traditional equipment struggles to reproduce the dynamic evolution of fluid properties such as viscosity and density along the flow path, resulting in experimental data often reflecting only the average characteristics under steady-state conditions. Furthermore, existing monitoring methods are mostly limited to isolated data recording; the monitoring signals lack closed-loop control logic with the front-end injection system, making the active regulation of the unsteady-state heat-fluid coupling process a bottleneck. These shortcomings collectively lead to significant deviations between the experimental process and the actual underground physical processes, restricting the depth and accuracy of research on dynamic heat exchange mechanisms under complex conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a dynamic coupling simulation system for core seepage heat transfer based on outlet temperature feedback, so as to solve the problem that the experimental results deviate greatly from the actual geological conditions in existing core seepage experiments due to constant injection temperature, lack of outlet state feedback, and inability to simulate real formation temperature gradients.

[0006] To achieve the above objectives, the technical solution provided by the present invention includes: A multi-media precision injection system is used to continuously supply fluid media with specific temperature and pressure to the end of the core according to preset experimental conditions. The gradient temperature-controlled core clamping system is used to support the core sample and apply radial confining pressure and axial load to it. At the same time, it constructs a non-uniform simulated formation temperature field by distributing multiple independent temperature control zones along the core axis. The multi-dimensional information sensing system at the outlet is used to monitor the temperature, pressure, instantaneous flow rate, and composition information of the fluid flowing out of the core outlet in real time, and converts the monitoring data into electrical signals for transmission. The dynamic coupling central control system, as the logical core of the system, is used to receive feedback signals from the multi-dimensional information sensing system at the outlet, and adjust the output power of the multi-media precision injection system and the heat flux density of each temperature control zone of the gradient temperature control core clamping system in real time according to the built-in heat exchange coupling model. The pressure compensation and recirculation system is used to maintain stable pore pressure inside the core and to cool, separate gas and liquid, and recover the outlet fluid.

[0007] In one embodiment of the present invention, the multi-media precision injection system comprises a high-pressure constant-flow and constant-pressure pump group, a fluid preheating chamber, a gas pressurization and buffer unit, and a multi-way switching valve group. The high-pressure constant-flow and constant-pressure pump group is equipped with a stroke displacement monitoring sensor, and its feeding accuracy reaches 0.001 ml / min. The fluid preheating chamber is heated by a wrapped ceramic electric heating fiber layer and has a spiral heat exchange pipeline inside to increase the residence time and heat exchange area of ​​the fluid in the preheating chamber. A first-stage platinum resistance thermometer is embedded in the inner wall of the preheating chamber to monitor the initial temperature of the fluid before injection and control the temperature fluctuation within ±0.1 degrees Celsius. The multi-way switching valve group adopts a high-temperature and high-pressure resistant six-way valve structure to realize the single-phase or multi-phase alternating injection of gaseous and liquid media.

[0008] Furthermore, the gradient temperature-controlled core clamping system includes a high-strength stainless steel cylinder, a fluororubber sealing sleeve, a segmented electric heating sleeve, and a hydraulic pressurization station. A confining pressure chamber is formed between the inner wall of the high-strength stainless steel cylinder and the fluororubber sealing sleeve. The hydraulic pressurization station injects hydraulic oil into the confining pressure chamber through a high-pressure pipeline to simulate the stress of the overburden. The segmented electric heating sleeve is closely attached to the outer surface of the stainless steel cylinder and is divided into at least 5 independent heating zones at equal intervals along the axial direction. Each heating zone is independently equipped with a proportional-integral-derivative controller and a second-stage platinum resistance thermometer. The second-stage platinum resistance thermometer extends through the cylinder wall to the outside of the fluororubber sealing sleeve to sense the real-time temperature of the corresponding zone. Through the instructions of the central control system, each heating zone can independently set different target temperatures according to the correspondence between formation depth and temperature gradient, thereby reconstructing the true longitudinal temperature scale distribution at the core scale.

[0009] Furthermore, the multi-dimensional information sensing system for the outlet is located at the junction of the outlet pipes of the core holder; it includes a corrosion-resistant measuring chamber, within which a high-sensitivity thermocouple array with a response time of less than 50 milliseconds is integrated; this thermocouple array is distributed at the center and edge of the flow channel cross-section to capture subtle temperature differences in the fluid caused by variations in the seepage path; a high-frequency pressure transmitter and an ultrasonic flow meter are sequentially connected behind the measuring chamber; the sampling frequency of the high-frequency pressure transmitter is not less than 100 Hz, used to capture pressure pulsations during the seepage process; the ultrasonic flow meter obtains the instantaneous flow velocity of the fluid at different temperatures through a non-contact measurement method to avoid scouring and damage to the measuring elements by the high-temperature fluid.

[0010] Furthermore, the dynamic coupling central control system incorporates heat exchange coupling control logic derived from the law of conservation of energy and Darcy's law. This control logic extracts the deviation between the outlet and inlet temperatures in real time and calculates the heat exchange efficiency inside the core in conjunction with the current flow rate. When the outlet temperature is lower than a preset threshold, the central control system automatically increases the compensating heat at the front end of the gradient temperature control core clamping system and simultaneously fine-tunes the heating power of the multi-media precision injection system to achieve advanced dynamic heat compensation. At the same time, the system can automatically calculate the change in seepage resistance based on the fluid viscosity-temperature curve and adjust the output pressure of the high-pressure constant flow and constant pressure pump group to ensure the relative stability of the seepage pressure difference during the dynamic evolution of heat exchange.

[0011] Furthermore, the pressure compensation and circulation system includes an automatic back pressure valve, a multi-stage heat exchange condenser, and a gas-liquid separator collector. The automatic back pressure valve receives pneumatic signals from the central control system and adjusts the needle valve opening to maintain a constant pressure gradient at the core outlet. The multi-stage heat exchange condenser adopts a counter-flow water-cooling structure to rapidly cool the high-temperature fluid at the outlet to the range of 20 to 30 degrees Celsius to prevent fluid flash evaporation from affecting the accuracy of flow measurement. The gas-liquid separator collector utilizes the principles of gravity sedimentation and cyclone separation to measure the produced oil, water, and gas in real time and provide sample collection points for subsequent chemical composition analysis.

[0012] Furthermore, the gradient temperature-controlled core clamping system also includes an axial displacement monitoring unit; the axial displacement monitoring unit acquires the axial deformation of the core under high temperature and high pressure coupling in real time through a laser displacement meter installed at the end of the pressurizing piston; the central control system dynamically adjusts the magnitude of the axial load through the hydraulic pressurizing station according to the acquired displacement data, so as to offset the additional stress generated by thermal expansion and ensure that the core is in the preset effective stress state during the experiment.

[0013] Furthermore, the dynamic coupling central control system also has a data synchronization mapping function, which can perform time stamp alignment processing on the data streams of platinum resistance thermometers, thermocouple arrays, pressure transmitters and flow meters at all levels; the processed data is imported into a preset formation equivalent heat flow model to calculate the apparent permeability, thermal conductivity and thermal dispersion coefficient of the core in real time, and display the spatiotemporal evolution characteristics of the temperature field and pressure field in the form of a three-dimensional trend graph.

[0014] As one embodiment of the present invention, the fluid preheating chamber in the multi-media precision injection system adopts a dual-chamber design. The main chamber is responsible for primary heating, and the secondary chamber is responsible for precise temperature adjustment using a proportional-integral-derivative control algorithm. A shut-off valve is provided between the main chamber and the secondary chamber. When the injected fluid changes from liquid to gas or supercritical state, the system automatically switches the valve to change the heat exchange length through which the fluid flows, ensuring that fluids of different phases reach the target simulated temperature before entering the core.

[0015] Furthermore, the segmented electric heating jacket of the gradient temperature control core clamping system adopts an external insulation layer structure. The insulation layer material is nano-aerogel felt, which has a thermal conductivity of less than 0.02 W / m Kelvin, effectively preventing heat loss to the external environment and improving the response speed and steady-state accuracy of the temperature control system.

[0016] Furthermore, the inner surface of the measuring cavity in the export multidimensional information sensing system is treated with a polytetrafluoroethylene coating to reduce the chemical corrosion of the metal substrate by high-temperature acidic fluids and ensure structural integrity and signal accuracy under long-term experiments.

[0017] Furthermore, the automatic back pressure valve in the pressure compensation and circulation system is driven by a high-precision stepper motor, with a displacement control accuracy of 0.5 micrometers, enabling fine adjustment of pore pressure on the order of 0.01 MPa.

[0018] Furthermore, the multi-media precision injection system is also equipped with a vacuum extraction unit, which performs vacuum treatment on the pipeline and core sample before the experiment begins. The vacuum level can reach below 10 Pa to eliminate the interference of residual air on the seepage and heat exchange process.

[0019] Furthermore, the spacing between the heating zones of each section of the gradient temperature control core clamping system has been optimized, and an active heat dissipation cooling ring is set between the sections to prevent thermal conduction coupling interference between adjacent temperature control zones, thereby ensuring the independence and steepness of the gradient temperature control.

[0020] As one embodiment of the present invention, the system operates in a real-time industrial bus network environment, and the subsystems exchange data through shielded signal lines to ensure the anti-interference capability of sensor signals in complex electromagnetic environments; the sampling cycle of the central control system is set to 10 milliseconds, which can capture the transient thermal response during the seepage jump process.

[0021] Furthermore, the dynamic coupling central control system also integrates a safety early warning module. When the temperature of any heating zone exceeds the set range by 10% or the pressure fluctuation is abnormal, the system will automatically trigger an emergency shutdown procedure and start the cooling circulation pump to physically cool the clamping system.

[0022] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. This invention, by introducing an outlet temperature feedback mechanism and a dynamically coupled central control system, completely changes the static simulation mode of constant injection end temperature in traditional experiments. The system can sense the final state of the fluid after heat exchange with the rock skeleton during the seepage process in real time, and dynamically adjust the power output of the injection end and each temperature control zone according to the feedback signal. This closed-loop control logic can realistically reproduce the unsteady evolution process of underground fluid during its migration due to viscosity-temperature effect, heat dissipation and phase change, significantly improving the physical fidelity of the heat exchange coupling experiment.

[0023] 2. This invention achieves axial segmented temperature control at the core scale through a gradient temperature-controlled core clamping system, which can construct up to five or more independent temperature control zones. This design breaks through the limitation of existing equipment that can only perform uniform heating, and can accurately simulate the real geometric temperature gradient of the formation and the thermal boundary conditions of different depth layers. Through the combination of active heat dissipation and precise proportional-integral-derivative control, the small-sized core simulation in the laboratory can equivalently map the thermodynamic environment of large-scale reservoirs, providing more valuable experimental data for the optimization of geothermal extraction and thermal oil recovery schemes.

[0024] 3. This invention integrates multi-dimensional information perception and automatic compensation mechanisms, enabling it to acquire conventional parameters such as temperature, pressure, and flow rate in real time. Furthermore, it uses axial displacement monitoring and hydraulic dynamic adjustment to offset measurement deviations caused by thermal stress during experiments. The system achieves a high degree of integration and dynamic coupling of the seepage field, temperature field, and stress field, avoiding the limitations of analyzing a single physical quantity. In addition, the fully automated control and multi-stage pressure reduction cooling design improve experimental efficiency while significantly enhancing system safety and operational stability under high pressure and high temperature conditions, providing an advanced experimental support platform for fundamental mechanism research in the field of energy development.

[0025] 4. The pressure compensation and circulation reflux system of this invention ensures extremely high control accuracy of pore pressure and back pressure in complex phase change seepage processes; through the cooperation of gas-liquid separation and real-time metering units, it can finely characterize the fluid production patterns under different temperature gradients, especially for thermodynamic simulation conditions involving the coexistence of multiphase fluids, where the repeatability and reliability of the data are greatly improved; the system's high flexibility enables it to adapt to various experimental needs, from conventional low-pressure seepage to ultra-deep high-pressure heat exchange, and has broad engineering application prospects and academic research value. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall technical solution architecture of the core seepage heat transfer dynamic coupling simulation system based on outlet temperature feedback proposed in this invention. Figure 2 This is a schematic diagram of the core principle framework of the heat exchange dynamic coupling control logic based on outlet temperature feedback in this invention. Figure 3 This is a logic framework diagram of the multi-segment gradient temperature control of the gradient temperature control core clamping system in this invention; Figure 4 This is a schematic diagram of the data interaction relationship and feedback process between the export multi-dimensional information sensing system and the central control system in this invention; Figure 5 This is a logic framework diagram of the high-precision temperature and pressure control and fluid supply of the multi-media precision injection system in this invention. Detailed Implementation Example 1

[0027] Please refer to the attached document. Figure 1 This embodiment discloses a core seepage heat transfer dynamic coupling simulation system based on outlet temperature feedback. This system constitutes a closed-loop experimental platform capable of simulating the fluid flow and heat exchange process within rock pores under high temperature and pressure conditions in deep formations. The system is highly integrated from multiple functional subsystems via pipelines, signal lines, and an industrial control bus. Its core structure includes a multi-media precision injection system, a gradient temperature-controlled core clamping system, an outlet multi-dimensional information sensing system, a dynamic coupling central control system, and a pressure compensation and circulation reflux system. In the overall operating architecture, the multi-media precision injection system is responsible for the front-end preparation and quantitative delivery of fluid; the gradient temperature-controlled core clamping system provides the physical support and multi-gradient thermal boundary environment for the experimental object; the outlet multi-dimensional information sensing system captures the physicochemical state changes of the fluid after it flows through the core in real time; the dynamic coupling central control system acts as the nerve center, executing closed-loop control logic and data processing; and the pressure compensation and circulation reflux system is responsible for the precise control of downstream pressure and the recovery and processing of outputs.

[0028] Please refer to the attached document. Figure 5 The multi-media precision injection system is the power source and heat transfer fluid inlet of the entire simulation system. This system consists of a high-pressure constant-flow / constant-pressure pump group, a fluid preheating chamber, a gas pressurization and buffer unit, and a multi-channel switching valve group. The high-pressure constant-flow / constant-pressure pump group adopts a dual-plunger parallel structure, capable of providing a working pressure of no less than 60 MPa. It integrates a stroke displacement monitoring sensor, accurately calculating the output flow rate by monitoring the real-time displacement of the plungers, achieving a feeding accuracy of 0.001 ml / min. The fluid preheating chamber employs a dual-chamber design. The main chamber is responsible for primary high-power heating, while the secondary chamber uses a proportional-integral-derivative (PID) control algorithm for precise temperature regulation. A shut-off valve is installed between the main and secondary chambers. When the injected fluid changes from a liquid to a gaseous or supercritical state, the system automatically switches the valve to change the heat transfer length the fluid flows through, ensuring that fluids of different phases reach the target simulation temperature before entering the core. The fluid preheating chamber is equipped with a spiral heat exchange pipeline with a total length of no less than 3000 mm to increase the residence time and heat exchange area of ​​the fluid within the chamber. A first-stage platinum resistance thermometer is embedded in the inner wall of the preheating chamber to monitor the initial temperature of the fluid before injection and control temperature fluctuations within ±0.1 degrees Celsius. The multi-way switching valve assembly employs a high-temperature and high-pressure resistant six-way valve structure, enabling single-phase or multi-phase alternating injection of gaseous and liquid media without interrupting the experimental process. The gas pressurization and buffer unit includes a multi-stage air compressor and a high-pressure buffer tank to smooth pressure pulsations caused by piston movement during ultra-low-speed seepage experiments.

[0029] Please refer to the attached document. Figure 3The gradient temperature-controlled core clamping system is the core hardware for constructing a simulated formation temperature gradient. It includes a high-strength stainless steel cylinder, a fluororubber sealing sleeve, a segmented electric heating sleeve, and a hydraulic pressurization station. The high-strength stainless steel cylinder is made of corrosion-resistant 316L stainless steel, with a wall thickness designed according to the maximum confining pressure to ensure sufficient creep resistance even at 200 degrees Celsius. A confining pressure chamber is formed between the inner wall of the stainless steel cylinder and the fluororubber sealing sleeve. The hydraulic pressurization station injects hydraulic oil into the confining pressure chamber through high-pressure pipelines to simulate the stress of the overburden. The segmented electric heating sleeve is tightly attached to the outer surface of the stainless steel cylinder and is divided into five independent heating zones at equal intervals along the axial direction. Each heating zone is independently equipped with a proportional-integral-derivative controller and a second-stage platinum resistance thermometer. The second-stage platinum resistance thermometer extends through the cylinder wall to the outside of the fluororubber sealing sleeve to sense the real-time temperature of the corresponding zone. The segmented electric heating jacket employs an external insulation layer structure made of nano-aerogel felt with a thermal conductivity of less than 0.02 W / m Kelvin, effectively preventing heat loss to the external environment. The spacing between each heating zone is optimized, and active cooling rings are installed between zones to prevent thermal conduction coupling interference between adjacent temperature control zones, thus ensuring the independence and steepness of the gradient temperature control. Through commands from the central control system, each heating zone can independently set different target temperatures based on the correspondence between formation depth and temperature gradient, thereby reconstructing the true longitudinal temperature scale distribution at the core scale. Furthermore, the gradient temperature control core clamping system also includes an axial displacement monitoring unit, which uses a laser displacement gauge installed at the pressurized piston end to acquire the axial deformation of the core under high temperature and high pressure coupling in real time.

[0030] Please refer to the attached document. Figure 4 The multi-dimensional information sensing system for the outlet is located at the junction of the outlet pipes of the core holder. It includes a corrosion-resistant measuring chamber with a PTFE coating on its inner surface to reduce chemical corrosion of the metal substrate by the high-temperature acidic fluid. A high-sensitivity thermocouple array with a response time of less than 50 milliseconds is integrated within the chamber. This thermocouple array is distributed at the center and edges of the flow channel cross-section to capture subtle temperature differences caused by variations in the seepage path. A high-frequency pressure transmitter and an ultrasonic flow meter are connected sequentially behind the measuring chamber. The high-frequency pressure transmitter has a sampling frequency of at least 100 Hz to capture pressure pulsations and fluctuations during the seepage process. The ultrasonic flow meter obtains the instantaneous flow velocity of the fluid at different temperatures through a non-contact measurement method, avoiding direct physical erosion damage to the measuring elements caused by the high-temperature fluid. All sensor signals are transmitted to the signal conditioning module via shielded cables, and after amplification and filtering, are converted into 16-bit resolution digital signals.

[0031] Please refer to the attached document. Figure 2The dynamically coupled central control system is the core of this system. It incorporates heat transfer coupling control logic derived from the law of conservation of energy and Darcy's law. This control logic extracts the deviation between the outlet and inlet temperatures in real time and calculates the heat exchange efficiency inside the core based on the current flow rate. The specific algorithm principle is as follows: First, by calculating the enthalpy difference between the core outlet and inlet, and combining the specific heat capacity of the fluid medium, instantaneous flow rate, and the equivalent thermal conductivity of the core skeleton, the current apparent heat transfer intensity is calculated. Then, this apparent heat transfer intensity is compared with a preset theoretical heat transfer model to extract compensation coefficients for thermal short-circuiting or retention effects caused by seepage inhomogeneity. Finally, power correction commands for each heating zone are dynamically generated based on these coefficients. When the outlet temperature is lower than a preset threshold, the central control system automatically increases the compensation heat at the front of the gradient temperature-controlled core clamping system and simultaneously fine-tunes the heating power of the multi-medium precision injection system, achieving proactive dynamic heat compensation. The system also integrates a safety warning module. When the temperature of any heating zone exceeds the set range by 10% or the pressure fluctuation is abnormal, the system will automatically trigger an emergency shutdown procedure and start the cooling circulation pump to physically cool the clamping system.

[0032] The pressure compensation and circulation system is used to maintain the dynamic balance inside the core. It includes an automatic back pressure valve, a multi-stage heat exchange condenser, and a gas-liquid separator. The automatic back pressure valve receives pneumatic signals from the central control system and uses a high-precision stepper motor to drive the adjustment needle valve opening, achieving a displacement control accuracy of 0.5 micrometers, enabling fine adjustment of pore pressure on the order of 0.01 MPa. The multi-stage heat exchange condenser adopts a counter-flow water-cooling structure, rapidly cooling the high-temperature fluid at the outlet to the range of 20°C to 30°C to prevent fluid flashing from affecting the accuracy of flow measurement. The gas-liquid separator utilizes the principles of gravity sedimentation and cyclone separation to measure the produced oil, water, and gas in real time, providing sample collection points for subsequent chemical composition analysis. During the experimental preparation stage, the multi-media precision injection system is also equipped with a vacuum extraction unit to evacuate the pipeline and core sample, achieving a vacuum level below 10 Pa.

[0033] In describing the core algorithm logic, the system introduces a coupled equation for the conservation of mass and energy in fluid flow within a porous medium. Algorithm Formula 1 is as follows:

[0034] In algorithm formula 1, Q represents the total energy transfer term per unit time, which includes the coupling of seepage mechanical energy conversion and thermal convection term; S represents the core cross-sectional area; k(T) represents the temperature-related permeability function; Represents the pressure gradient vector; This represents the dynamic viscosity of the fluid, and this value is dynamically adjusted according to the real-time temperature feedback from the sensing system. C and C represent the fluid density and specific heat capacity, respectively; v represents the seepage velocity captured in real time by the ultrasonic flow meter. and These represent the outlet temperature fed back by the multi-dimensional information sensing system and the inlet temperature set by the multi-media precision injection system, respectively. The central control system, by solving this equation in real time, can predict and adjust the power output of the gradient temperature-controlled core clamping system in subsequent time periods.

[0035] To further accurately characterize the thermal dispersion properties inside the core, the system also employs a thermal balance correction algorithm. Algorithm formula 2 is as follows:

[0036] In algorithm formula 2, This represents the equivalent thermal conductivity at the core scale. The total heat flux density input from the segmented electric heating jacket to the core represents the total heat flux density; L and A are the length and cross-sectional area of ​​the core, respectively. The temperature of the clamp wall is the monitored temperature. This represents the average temperature of the outlet fluid. This represents the thermal dispersion correction coefficient determined by the seepage Reynolds number. Through real-time calculation of Algorithm Formula 2, the central control system can precisely control the temperature difference between the five axial heating zones, thereby maintaining the preset formation temperature gradient curve without distortion.

[0037] In the system's data synchronization mapping function, the data streams from various platinum resistance thermometers, thermocouple arrays, pressure transmitters, and flow meters undergo timestamp alignment. The processed data is then imported into a pre-defined formation equivalent heat flow model to calculate the apparent permeability, thermal conductivity, and thermal dispersion coefficient of the core sample in real time. The central control system's sampling cycle is set to 10 milliseconds to ensure the capture of transient thermal responses during seepage jumps. Furthermore, the system dynamically adjusts the axial load via a hydraulic pressurization station to counteract the additional stress generated by thermal expansion, ensuring the core sample remains under a pre-defined effective stress state during the experiment. This multi-field coupled control strategy enables small-scale core simulations within the laboratory to effectively map the real thermodynamic environment of large-scale reservoirs. Example 2

[0038] Based on Example 1, this example incorporates specific structural optimizations and process improvements for ultra-deep, high-temperature, high-pressure acidic fluid seepage conditions. Because the environment of ultra-deep formations is much harsher, fluid seepage is often accompanied by complex phase changes and chemical reactions, thus placing higher demands on the system's corrosion resistance and dynamic temperature control response.

[0039] Please refer to the attached document. Figure 1In this embodiment, the multi-media precision injection system, designed for supercritical carbon dioxide injection, replaces the spiral heat exchange pipe material of the fluid preheating chamber with Hastelloy. Hastelloy exhibits excellent resistance to pitting corrosion and stress corrosion cracking under high temperature, high pressure, and acidic conditions. Simultaneously, an electromagnetic induction heating unit is added to the main chamber of the dual-chamber preheating chamber, providing faster thermal power compensation when fluid flow surges. The proportional-integral-derivative (PID) control algorithm of the secondary chamber employs a feedforward decoupling strategy, treating flow fluctuations as feedforward disturbances to pre-adjust the terminal voltage of the heating resistance wire, thereby further compressing the inlet temperature fluctuation range to ±0.05 degrees Celsius. Furthermore, the plunger seal of the high-pressure constant-flow constant-pressure pump unit utilizes self-lubricating carbon fiber-reinforced polytetrafluoroethylene (PTFE) material to counteract the dissolution and extraction effects of supercritical carbon dioxide on conventional grease, ensuring the pump unit's output stability during long-term operation.

[0040] Please refer to the attached document. Figure 3 To address the need for simulating the immense overburden stress in ultra-deep formations, the hydraulic pressurization station of the gradient temperature-controlled core clamping system has been upgraded to an ultra-high-pressure hydraulic unit, with a maximum working pressure of 150 MPa. The high-strength stainless steel cylinder employs a double-layer prestressed sleeve structure; the inner cylinder is specifically designed to handle fluid contact and bear the heat load, while the outer cylinder provides robust radial support. The number of heating zones in the segmented electric heating jacket has increased from five to eight, with a reduction in the length of each zone, significantly improving the spatial resolution of the axial temperature distribution. The thickness of the nano-aerogel felt insulation layer has been increased to 50 mm, and a reflective aluminum foil layer has been added to the outermost layer to reduce radiative heat transfer. The active cooling ring utilizes a microchannel cooling structure, rapidly removing stray latent heat from the boundaries between temperature-controlled zones through circulating refrigerant. This increases the adjustable range of the temperature gradient slope between adjacent temperature-controlled zones to 5 degrees Celsius per centimeter, enabling a more realistic simulation of large-scale temperature step phenomena within the formation.

[0041] Please refer to the attached document. Figure 4 An online infrared spectroscopy monitoring unit has been added to the measurement chamber of the multi-dimensional information sensing system at the outlet. This unit observes the outflowing fluid through a high-pressure resistant sapphire window, analyzing changes in ion concentration and gas composition in the fluid in real time. The number of thermocouple arrays has been increased to 16, arranged in a quincunx pattern within the flow channel. This arrangement allows for a more accurate construction of the temperature field isotherm map of the outlet cross-section. The high-frequency pressure transmitter uses a piezoelectric ceramic sensor with a metal diaphragm isolation structure, increasing its response frequency to 500 Hz, enabling it to capture micron-level air mixing noise generated when fluid passes through micro-cracks. The ultrasonic flow meter integrates a frequency tracking algorithm, automatically adjusting the transducer's transmission frequency based on changes in fluid density and sound velocity, ensuring accurate volumetric flow rate data even when the fluid undergoes a phase change causing drastic fluctuations in acoustic parameters.

[0042] Please refer to the attached document. Figure 2 In this embodiment, the dynamically coupled central control system incorporates a machine learning-assisted prediction module. This module, based on a digital twin model generated from historical experimental data, predicts the heat transfer inertia during the seepage process. When the outlet temperature feedback signal shows a slight downward trend, the system does not need to wait for the deviation to reach a threshold; instead, it directly provides the power increment of the gradient temperature-controlled core clamping system through the prediction module, achieving true predictive control. The real-time industrial bus network of the central control system has been upgraded to a gigabit Ethernet architecture, reducing the data interaction latency between subsystems to less than 1 microsecond. To ensure the long-term operation of the system, a health monitoring unit has also been added. By analyzing the current waveform changes of each heating wire section, it predicts the fatigue life of the heating elements and issues maintenance warnings in advance.

[0043] In this embodiment, a precision three-phase separator is added to the pressure compensation and recirculation system. This separator accurately monitors the oil-water interface and the gas-liquid interface using an ultrasonic level gauge. The automatic back pressure valve adopts a dual-valve parallel mode: a large-diameter valve is responsible for coarse adjustment of the pressure gradient, and a small-diameter needle valve is responsible for fine compensation. This combination solves the contradiction between the adjustment range and adjustment accuracy of a single valve under ultra-deep high pressure differential conditions. The multi-stage heat exchange condenser adds a two-stage liquid nitrogen deep cooling stage, which can condense and recirculate the produced gaseous medium, realizing a closed-loop circulation of the experimental medium.

[0044] In high-pressure heat transfer simulations, the system handles thermal response time with greater precision. Real-time correction based on the finite volume method has been incorporated into the algorithm logic. When calculating heat exchange intensity, the core is no longer treated as a one-dimensional homogeneous rod, but rather divided into thousands of virtual computational units. The dynamically coupled central control system reads measured data from eight heating zones and 16 thermocouples, using an inversion algorithm to deduce the temperature field contour map inside the core. This contour map allows the system to identify heat accumulation or seepage dead zones caused by local heterogeneity. If a seepage dead zone is identified, the system automatically adjusts the axial load and confining pressure ratio of the hydraulic pressurization station, inducing channel reorganization through minor stress disturbances, thereby ensuring the experimental results have broad statistical representativeness. Example 3

[0045] Building upon Example 2, this example further expands the system's application scenarios, with a focus on enhancing the experimental capabilities for simulating steam or fire-driven operations in deep thermal oil recovery. Under these conditions, the phase state of the injected medium is extremely complex, and the temperature range is vast, often extending from room temperature to over 350 degrees Celsius.

[0046] Please refer to the attached document. Figure 5In this embodiment, the multi-media precision injection system includes a steam generation unit and an oxidant injection unit. The steam generation unit utilizes the high-pressure flash evaporation principle to convert ultrapure water into high-temperature saturated steam with adjustable dryness. The internal structure of the preheating chamber is optimized to a multi-stage staggered baffle heat exchanger to accommodate the low thermal conductivity of the steam medium. The first-stage platinum resistance thermometer adopts an armored structure to withstand the mechanical impact of high-speed steam flow. The multi-way switching valve group is upgraded to a ceramic ball valve with active sealing compensation function, solving the problem of thermal jamming of metal valve cores above 350 degrees Celsius. To accurately measure the molar flow rate of the injected gas, a mass flow controller is introduced into the system, and its feedback signal is connected to the central control system to achieve precise locking of the injection end temperature, pressure, and flow rate.

[0047] Please refer to the attached document. Figure 3 The gradient temperature-controlled core clamping system, designed for the high-temperature leading edge zone in fire-drive simulations, increases the single-segment heating power of the segmented electric heating jacket to 3 kW. The insulation layer, based on nano-aerogel, incorporates a layer of high-temperature resistant ceramic fiber blanket, enabling it to withstand internal heat loads of 450 degrees Celsius for extended periods. A heat exchanger is added to the circulating oil circuit of the hydraulic pressurization station, continuously removing heat transferred from the cylinder to the confining oil via cooling water, ensuring the hydraulic system always operates within its rated temperature range below 60 degrees Celsius. The laser displacement gauge in the axial displacement monitoring unit performs non-contact measurements through a quartz optical window, avoiding direct damage to precision optical components from the high-temperature environment. To simulate the actual stress path of the formation, the hydraulic pressurization station supports a stepped pressurization mode, capable of synchronously executing complex temperature and pressure rise curves with the temperature control system.

[0048] Please refer to the attached document. Figure 4 An active temperature-controlled heating tape has been added to the outside of the measuring chamber of the multi-dimensional information sensing system at the outlet. This is to ensure that the high-viscosity heavy oil flowing from the core does not precipitate wax or solidify due to the drop in ambient temperature before entering the flow meter. The ultrasonic flow meter uses a high-temperature transducer, which can operate stably at an ambient temperature of 250 degrees Celsius. The high-frequency pressure transmitter is equipped with a capillary heat dissipation structure to ensure that the electronic components are always kept at a normal temperature, thereby improving the long-term stability of the measurement. An online viscometer is also installed inside the measuring chamber to capture the dynamic viscosity response of the fluid due to thermal decomposition or physical mixing in real time, providing a basis for the central control system to adjust the driving pressure.

[0049] Please refer to the attached document. Figure 2The dynamic coupling central control system introduces nonlinear control logic to address thermal instability caused by phase transitions during thermal oil recovery. This logic monitors the rate of change of outlet temperature, i.e., the first and second derivatives, to determine whether a phase transition front has broken through within the core. When the temperature change slope exceeds a set threshold, the system rapidly increases the cooling intensity of the cooling circulation recirculation system and appropriately reduces the injection power to prevent thermal runaway. The data synchronization mapping function adds a four-dimensional visualization interface, which can simultaneously display the spatiotemporal evolution animations of the pressure field, temperature field, saturation field, and stress field, allowing researchers to intuitively observe the physical landscape of the thermal sweep process.

[0050] In the pressure compensation and recirculation system, a scrubbing tower unit is added downstream of the gas-liquid separator to cope with the acidic flue gas generated by the fire-driven process. This unit uses alkaline absorbent to neutralize hydrogen sulfide and carbon dioxide in the produced gas. The valve core surface inside the automatic back pressure valve is coated with a tungsten carbide hard alloy layer, which greatly improves its resistance to high-speed gas-solid two-phase flow erosion. The multi-stage heat exchange condenser adopts a redundant design combining forced air cooling and water cooling to ensure that even in the event of a water shortage in the laboratory, the safe temperature at the back pressure end can be maintained through the air cooling system.

[0051] In terms of specific algorithm applications, the system focuses on enhancing the dynamic calculation of effective permeability within the core sample. As temperature increases, the pore structure of the rock skeleton may close due to thermal expansion or develop new microcracks due to thermal stress. In this embodiment, Algorithm Formula 1 is extended to a coupled form incorporating the thermal stress tensor. The dynamically coupled central control system performs a global stress balance calculation every 100 milliseconds, converting the axial deformation obtained from the laser displacement gauge into a porosity correction factor, thereby updating the permeability parameter in Darcy's law in real time. In this way, the system can highly simulate the porosity-permeability evolution of the formation during thermal development.

[0052] During system operation, the central control system automatically identifies whether fingering has occurred in the seepage channel based on outlet temperature feedback. If the cross-sectional temperature difference displayed by the outlet thermocouple array is too large, it indicates that the fluid has formed a dominant channel inside the core. At this time, the control system automatically triggers the pulse injection mode, intermittently changing the pump output pressure to disrupt the fingering front using pressure wave disturbance, thereby guiding the fluid to seep into the unaffected area. The realization of this function fully demonstrates the core advantage of this invention—active control based on outlet temperature feedback—making the experimental simulation not only a static observation but also a dynamic control and optimization, providing the most realistic simulation basis for the design of thermal oil recovery construction in oil and gas fields.

[0053] The entire system's communication bus employs a dual-redundant design. Even if one physical link fails, data exchange can automatically switch to the backup link within milliseconds, ensuring the safety of the high-pressure, high-temperature experiment. The system's overall control software features an open interface specification, enabling easy data exchange with third-party formation simulation software, achieving deep integration of laboratory physical simulation and numerical simulation. This comprehensive, multi-dimensional simulation platform has significant technological implications for enhancing my country's research level in the field of deep oil and gas and geothermal energy development.

[0054] In the actual experimental process, operators only need to set the target formation depth, expected temperature gradient curve, injection pressure, and flow sequence on the graphical interface of the dynamically coupled central control system. The system will automatically start the vacuum extraction program, and then the hydraulic pressurization station will apply confining pressure and axial load according to the preset path. After mechanical equilibrium is reached, each heating zone of the gradient temperature-controlled core clamping system begins to heat up according to the preset slope. At the same time, the fluid preheating chamber synchronously preheats the fluid medium. When the temperature and pressure states of each link in the system reach the steady-state equilibrium point, the multi-media precision injection system officially starts injection. Throughout the seepage process, the outlet multi-dimensional information sensing system continuously outputs feedback signals, and the central control system, like an experienced engineer, fine-tunes every heating power and pressure equilibrium point of the entire system at the microsecond level based on these feedback signals. This fully automated, high-precision closed-loop experimental process greatly reduces human interference and improves the repeatability and scientific value of experimental data.

[0055] Furthermore, the pressure compensation and recirculation system in this invention takes into account both environmental protection and economic requirements. For some expensive experimental media, such as special surfactants or rare gases, the gas-liquid separator can achieve efficient component recovery, and through subsequent purification equipment, it can be recirculated back to the multi-media precision injection system. This recycling design not only reduces the operating cost of a single experiment but also aligns with the modern trend of green and environmentally friendly laboratory development. All these details together constitute the technical integrity and leading-edge nature of the system described in this embodiment.

[0056] In summary, this invention, through complex electromechanical integration and intelligent control logic, successfully achieves the ultimate simulation of the dynamic process of seepage and heat transfer in the formation. It not only possesses precise control over first-order physical quantities such as temperature and pressure, but also the ability to deeply map and dynamically intervene in second-order processes such as energy flow and thermodynamic evolution. It is an indispensable high-end scientific research tool in the fields of deep earth exploration and energy development. The widespread application of this system will undoubtedly drive the leapfrog development of related disciplines from qualitative description to quantitative prediction. All descriptions in this embodiment are intended to demonstrate the core principles and specific engineering implementation of this invention. The specific numerical values ​​and material selections are merely examples of optimized schemes and do not constitute a limitation on the scope of protection of the invention. Any equivalent improvements based on the core ideas of this invention should be included within the scope of protection.

Claims

1. A dynamic coupling simulation system for core seepage heat transfer based on outlet temperature feedback, comprising: The system comprises a multi-media precision injection system, a gradient temperature-controlled core clamping system, an outlet multi-dimensional information sensing system, a dynamic coupling central control system, and a pressure compensation and circulation reflux system. The multi-media precision injection system consists of a high-pressure constant-flow / constant-pressure pump group, a fluid preheating chamber, a gas pressurization buffer unit, and a multi-channel switching valve group. The high-pressure constant-flow / constant-pressure pump group is equipped with a stroke displacement monitoring sensor. The fluid preheating chamber adopts a dual-chamber design and has a spiral heat exchange pipeline inside. A first-stage platinum resistance thermometer is embedded in the inner wall of the fluid preheating chamber. The gradient temperature-controlled core clamping system includes a high-strength stainless steel cylinder, a fluororubber sealing sleeve, a segmented electric heating sleeve, a hydraulic pressurization station, and an axial displacement monitoring unit. The segmented electric heating sleeve is tightly attached to the outer surface of the high-strength stainless steel cylinder and is divided into at least five independent heating zones at equal intervals along the axial direction. Each heating zone is independently equipped with a proportional-integral-derivative controller and a second-stage platinum resistance thermometer. The axial displacement monitoring unit uses a laser displacement gauge mounted on the pressurized piston end to acquire the axial deformation of the core under high temperature and high pressure coupling in real time. The outlet multidimensional information sensing system is located at the confluence of the outlet pipes of the core holder and includes a corrosion-resistant measuring chamber. The measuring chamber integrates a thermocouple array with a response time of less than 50 milliseconds. A high-frequency pressure transmitter with a sampling frequency of not less than 100 Hz and an ultrasonic flow meter are connected sequentially behind the measuring chamber. The dynamic coupling central control system has a built-in heat exchange coupling control logic based on the law of conservation of energy and Darcy's law. It is used to receive feedback signals from the outlet multidimensional information sensing system, extract the deviation between the outlet temperature and the inlet temperature in real time, and calculate the heat exchange efficiency inside the core by combining the instantaneous flow rate captured by the ultrasonic flow meter. The pressure compensation and circulation reflux system includes an automatic back pressure valve, a multi-stage heat exchange condenser, and a gas-liquid separator collector.

2. The dynamic coupling simulation system for core seepage heat transfer based on outlet temperature feedback according to claim 1, characterized in that, The operation process of the heat exchange coupling control logic is as follows: by performing integral calculation on the cross-sectional area of ​​the core, the temperature-related permeability function, pressure gradient vector, fluid dynamic viscosity, fluid density, specific heat capacity, and seepage velocity captured in real time by the ultrasonic flow meter are coupled to obtain the total energy transfer including the seepage mechanical energy conversion term and the heat convection term. The apparent heat transfer intensity is calculated by calculating the enthalpy difference between the core outlet and inlet, combined with the specific heat capacity, instantaneous flow rate, and equivalent thermal conductivity of the fluid medium and the core skeleton. The apparent heat transfer intensity is then compared with the preset theoretical heat transfer model to extract the thermal short-circuit compensation coefficient or retention effect compensation coefficient caused by seepage non-uniformity. Power correction commands for each heating zone are then dynamically generated based on the thermal short-circuit compensation coefficient or retention effect compensation coefficient.

3. The dynamic coupling simulation system for core seepage heat transfer based on outlet temperature feedback according to claim 1, characterized in that, The segmented electric heating jacket adopts an external insulation layer structure, and the insulation layer material is a nano-aerogel felt with a thermal conductivity of less than 0.02 W / m Kelvin. An active heat dissipation cooling ring is set between each heating area to prevent thermal conduction coupling interference between adjacent heating areas. The dynamic coupling central control system is also used to dynamically adjust the axial load based on the axial deformation data obtained by the laser displacement meter through the hydraulic pressurization station to offset the additional stress caused by thermal expansion.

4. The dynamic coupling simulation system for core seepage heat transfer based on outlet temperature feedback according to claim 1, characterized in that, The fluid preheating chamber includes a main chamber and a secondary chamber. The main chamber performs primary heating, while the secondary chamber performs temperature regulation using a proportional-integral-derivative (PID) control algorithm. A shut-off valve is installed between the main chamber and the secondary chamber. When the injected fluid changes from a liquid state to a gaseous state or a supercritical state, the dynamic coupling central control system changes the heat exchange length through which the fluid flows by using a multi-way switching valve group. The multi-media precision injection system is also equipped with a vacuum extraction unit, which is used to evacuate the pipeline and core sample before the experiment begins, so that the vacuum level reaches below 10 Pa.

5. The dynamic coupling simulation system for core seepage heat transfer based on outlet temperature feedback according to claim 1, characterized in that, The inner surface of the measuring chamber is coated with polytetrafluoroethylene; the thermocouple array is distributed at the center and edge of the flow channel cross-section of the measuring chamber to capture the temperature difference of the fluid due to the difference in the seepage path; the high-frequency pressure transmitter is used to capture the pressure pulsation during the seepage process; the ultrasonic flow meter obtains the instantaneous flow rate of the fluid at different temperatures through a non-contact measurement method.

6. The dynamic coupling simulation system for core seepage heat transfer based on outlet temperature feedback according to claim 2, characterized in that, The dynamic coupling central control system also incorporates a thermal balance correction algorithm. The calculation process of the thermal balance correction algorithm is as follows: obtain the total heat flux density input from the segmented electric heating jacket to the core, the length and cross-sectional area of ​​the core, the monitored temperature of the high-strength stainless steel cylinder wall, and the average temperature of the outlet fluid; combine the heat dispersion correction coefficient determined by the seepage Reynolds number to calculate the equivalent thermal conductivity at the core scale; the dynamic coupling central control system controls the temperature difference between the five axial heating zones based on the calculated equivalent thermal conductivity.

7. The dynamic coupling simulation system for core seepage heat transfer based on outlet temperature feedback according to claim 1, characterized in that, The automatic back pressure valve receives pneumatic signals from the dynamically coupled central control system and uses a high-precision stepper motor to drive and adjust the opening of the needle valve; the displacement control accuracy of the high-precision stepper motor reaches 0.5 micrometers, realizing the adjustment of pore pressure on the order of 0.01 MPa; the multi-stage heat exchange condenser adopts a counter-flow water-cooling structure to cool the fluid at the outlet end to the range of 20 degrees Celsius to 30 degrees Celsius. The gas-liquid separator uses the principles of gravity sedimentation and cyclone separation to measure and collect samples of the produced oil, water, and gas in real time.

8. The dynamic coupling simulation system for core seepage heat transfer based on outlet temperature feedback according to claim 1, characterized in that, The dynamic coupling central control system also has a data synchronization mapping function, which is used to perform time stamp alignment processing on the data streams of the first-stage platinum resistance thermometer, the second-stage platinum resistance thermometer, the thermocouple array, the high-frequency pressure transmitter, and the ultrasonic flow meter. The processed data is imported into a preset formation equivalent heat flow model to calculate the apparent permeability, thermal conductivity, and thermal dispersion coefficient of the core in real time. The sampling cycle of the dynamic coupling central control system is set to 10 milliseconds. The dynamic coupling central control system also integrates a safety warning module, which is used to trigger an emergency shutdown procedure and start the cooling circulation pump when the temperature of the heating area exceeds the set range by 10% or the pressure fluctuation is abnormal.

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