Device and method for dynamically detecting gravity differentiation of mixed gas under high temperature and high pressure

Abstract

The application discloses a high-temperature and high-pressure mixed gas gravity differentiation dynamic detection device and method, which comprises a mixed gas supply and pressure stabilizing module, a pressurizing and heating module, a long core holder and confining pressure temperature control module, a multi-position sampling module, a component analysis module and a control and data acquisition module. The application can realize stable injection of mixed gas, vertical closed standing and repeated sampling at multiple height positions under a high-temperature and high-pressure environment. In combination with gas chromatography quantitative analysis, the detection device and method form spatial and time component evolution data detection devices and methods to obtain the dynamic differentiation rule of mixed gas under the action of a gravity field, and provide experimental basis for stratified risk assessment of gas storage, injection-production system optimization and safety evaluation of mixed gas storage and transportation.

Description

Technical Field

[0001] This invention relates to the field of experimental testing in oil and gas engineering and research on the mechanism of multi-component gases, and particularly to a device and method for dynamic detection of gravity differentiation of mixed gases under high temperature and high pressure. Background Technology

[0002] In engineering scenarios such as underground gas storage peak-shaving operation, enhanced oil recovery (EGR) of gas reservoirs, carbon dioxide sequestration (CCUS), and multi-component simulated natural gas storage and transportation, the injected or present gas is often a two-component or multi-component mixed gas system, such as CH4-CO2, CH4-N2, or simulated natural gas containing CO2.

[0003] Due to the differences in density, viscosity, compressibility and diffusion coefficient of different components under high temperature and high pressure conditions, in addition to convection and dispersion, the mixed gas in the porous medium may also generate density difference-driven stratification enrichment and concentration gradient formation under the action of gravity field, which in turn causes fluctuations in the composition of the produced gas, changes in local gas properties and phase state, changes in the stability of the displacement front, and key indicators such as gas effective utilization rate and safety evaluation.

[0004] Existing experimental studies on CO2-CH4 mixed gas systems primarily employ sand-filled pipes or core displacement devices to analyze dispersion, mixing, and displacement efficiencies. These studies indicate that under certain reservoir conditions, gravity significantly influences the concentration and degree of mixing of the mixed gas, with the effect becoming even more pronounced in multi-scale porous media (long cores). Furthermore, some studies have utilized vertical long core devices to conduct gravity differentiation-related experiments, demonstrating that sampling location and timing have a significant impact on component measurement results.

[0005] However, the aforementioned existing technologies still have shortcomings when used for dynamic differentiation detection of mixed gases under high temperature and high pressure. For example, they mostly use single-point (outlet end) sampling, making it difficult to form a component profile along the height direction and to quantitatively evaluate the spatial distribution of differentiation intensity. They mostly focus on the injection or displacement stage, lacking a repeatable time-series sampling method for component evolution during the closed settling stage after injection, making it difficult to characterize the entire process of differentiation from occurrence to stabilization. Under high temperature and high pressure (HPHT) conditions, gas density and diffusion properties change significantly, which strongly affects the driving force and rate of differentiation, but there are still insufficient devices and processes to achieve stable vertical settling, multi-point sampling, and safety control under high temperature and high pressure. There is a lack of a unified experimental and data processing system centered on fixed long-scale porous media, vertical gravity direction, multi-point sampling, chromatographic quantitative analysis, and retesting for multiple settling times, making it difficult to systematically compare results under different ratios and conditions.

[0006] Therefore, to address the problems in the existing technologies, such as the difficulty in obtaining the spatial profile of differentiation, the difficulty in tracking the static stage, and the difficulty in achieving multi-point sampling under high temperature and high pressure HPHT conditions, a detection device and method are needed to provide a device and method that can achieve stable injection of mixed gas under high temperature and high pressure, vertical closed static placement, and repeated sampling at multiple height positions, combined with gas chromatography quantitative analysis to form spatial and temporal component evolution data. This is a technical problem that urgently needs to be solved by those skilled in the art to obtain the dynamic differentiation law of mixed gas under the action of gravity field, and to provide experimental basis for the stratified risk assessment of gas storage, the optimization of injection and extraction systems, and the safety evaluation of mixed gas storage and transportation. Summary of the Invention

[0007] In view of this, the present invention provides a device and method for dynamic detection of gravity separation of mixed gas under high temperature and high pressure.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A dynamic detection device for gravity differentiation of mixed gas under high temperature and high pressure includes: a mixed gas supply and pressure stabilization module, a pressurization and heating module, a long core holder and confining pressure and temperature control module, a multi-position sampling module, a component analysis module, and a control and data acquisition module; among which,

[0010] The mixed gas supply and pressure stabilization module is located at the far right of the device. Its outlet is first connected to the heating unit of the heating and pressurization module via a pipeline to heat the gas to a predetermined temperature. The heated gas then flows to the pressurization module, which pressurizes the gas in a hot state to achieve the target experimental pressure. The outlet of the pressurization and heating module is connected to the bottom injection end of the long core holder via a high-temperature and high-pressure resistant pipeline. The long core holder is vertically placed within the control of the confining pressure module to simulate the gravity environment of a vertical stratigraphic profile. The multi-position sampling module contains several micro-adjustment valves, which are connected to sampling holes at different heights on the side wall of the long core holder. The mixed gas from the sampling holes at different heights is collected by a gas collection bag, and the concentration of the mixed gas is tested using the component analysis module. The control and data acquisition module is connected to the pressure sensor, temperature sensor, confining pressure pump, and pressurization pump in the above modules to record system parameters.

[0011] The gas mixture supply and pressure stabilization module is used to provide gas mixtures with different ratios;

[0012] The pressurization and heating module is used to pressurize the gas mixture to the target pressure and heat it to the target temperature, with a maximum heating temperature of 150°C and a pressure of 70MPa.

[0013] The long core holder and the confining pressure and temperature control module enable the long core holder to achieve axial sealing, confining pressure loading, constant temperature maintenance, and vertical placement.

[0014] The multi-location sampling module is equipped with four sampling ports at different heights along the axial direction of the long core sample, with a spacing of 5 to 10 cm between the sampling ports.

[0015] The component analysis module is a gas chromatograph (GC), which can perform quantitative analysis of two components and output mole fraction or volume fraction.

[0016] The control and data acquisition module is used to record and control pressure, confining pressure, temperature, injection end time, settling time, sampling time, and valve opening and closing status.

[0017] Preferably, the mixed gas supply and pressure stabilization module includes two single-component gas cylinders, a gas mixing unit, a pressure regulating valve, and a shut-off valve;

[0018] The mixing unit is used to set and stably output mixed gases of different concentrations;

[0019] The pressure regulating valve is used to adjust the gas output pressure to the required range at the inlet of the pressurization module.

[0020] The shut-off valve is used to achieve isolation and safety control of the system before and after injection;

[0021] To ensure the accuracy of the mixing ratio, a mixing buffer tank is set up and equipped with a pressure sensor, and homogenization is performed before injection.

[0022] Preferably, the pressurization and heating module includes a gas booster pump, an electric heating device, a temperature controller, and a temperature sensor;

[0023] The electric heating device is arranged on the main air inlet pipe into the long core holder. The temperature sensor can be arranged at the heater outlet and the holder inlet respectively to monitor and correct the heat loss of the pipeline and ensure that the temperature of the gas entering the core meets the set value.

[0024] To prevent localized overheating from causing gas decomposition or a decline in the performance of sealing materials, a temperature upper limit protection system is installed.

[0025] Preferably, the clamp includes a built-in core cavity, an end sealing structure, a confining pressure cavity, and a heating and insulation structure;

[0026] The confining pressure cavity is loaded with confining pressure medium by a confining pressure pump, and the confining pressure is stabilized by a closed-loop control of a pressure sensor.

[0027] The clamp is equipped with a vertical fixed support, so that the core axis is aligned with the direction of gravity, thereby promoting the differentiation driven by the density difference of the components under the action of gravity after the injection is completed and sealed.

[0028] Preferably, each sampling port is equipped with an independent high-temperature and high-pressure shut-off valve, a quick connector, and a sampling pipeline connected to the gas collection bag;

[0029] The sampling port is located on the outer shell of the clamp and is connected to the corresponding height position of the core cavity through a pressure-resistant micro-conduit, so as to collect the mixed gas at different heights;

[0030] To reduce the disturbance to the system caused by sampling, a small-volume sampling pipeline and a flow-limiting structure are adopted, and the volume of each sampling is specified to be within a controllable range.

[0031] Preferably, the GC is equipped with a thermal conductivity detector (TCD), a flame ionization detector (FID), and necessary conversion devices;

[0032] To ensure data accuracy, the standard gas was calibrated before the experiment to obtain the response factors of each component.

[0033] Preferably, the control and data acquisition module adopts a PLC control system to record parameters throughout the entire test process and automatically calculate and plot the differentiation index.

[0034] A method for dynamic detection of gravity differentiation of gas mixtures under high temperature and high pressure includes the following steps:

[0035] Step 1: Core assembly and parameter design

[0036] Using a short core splicing method, several cylindrical core segments with a diameter of 2.5 cm and a length of 3–8 cm were selected, with a splicing length greater than 50 cm. Based on the completed permeability measurement experiments, the core segments were arranged in a harmonic mean manner, and the calculation formula is as follows:

[0037] （1）

[0038] The average permeability can be calculated using the above formula. Value, taken from permeability and The closest core sample is placed first at the outlet, followed by the remaining core samples. The value is calculated, and the permeability in the remaining core is taken as a factor of the new value. The core with the closest value is placed second at the outlet end, and so on, to obtain the sorting of the selected cores from the outlet end to the inlet end;

[0039] Step 2: Quantitative analysis by gas chromatography

[0040] For a gas sample collected at sampling point z at φ, the mole fraction or volume fraction of the i-th component is calculated using the following formula:

[0041] （2）

[0042] In the formula: A i F represents the chromatographic peak area. iLet M be the response factor and M be the number of components. This allows us to obtain the responses at the same time along multiple height positions z1, z2, ..., z at the same height. n Component profile ;

[0043] Step 3: Dynamic Differentiation Evaluation Indicators and Dynamic Parameters

[0044] The expressions for differentiation index, differentiation gradient, enrichment coefficient, two-component separation coefficient, theoretical correlation with gravity differentiation, and dynamic characteristic time fitting are as follows:

[0045] Differentiation Index:

[0046] Taking the target component 𝑖 as an example, the differentiation index between the upper and lower ends is defined as follows:

[0047] （3）

[0048] In the formula: Let f be the differentiation index of component 𝑖 at time t. The mole fraction of component i at the top of the highest sampling port. The mole fraction of component i at the lower end of the lowest sampling port. The height of the highest sampling port. The lowest sampling port position height, Let i be the average mole fraction of component i at all sampling points at time t;

[0049] The average value is:

[0050] （4）

[0051] In the formula: The number of sampling ports, The height position of the nth sampling port;

[0052] Differentiated gradient:

[0053] （5）

[0054] In the formula: Let be the differentiation gradient of component i at time t, and the other parameters are the same as above;

[0055] Enrichment coefficient:

[0056] Let the mole fraction of component i in the injected gas mixture be... ,but:

[0057] （6）

[0058] In the formula: Let z be the enrichment coefficient of component i relative to the injection state at time t;

[0059] Separation coefficient of the two components:

[0060] For components a and b:

[0061] （7）

[0062] In the formula: , The mole fractions of components a and b in the injected gas mixture;

[0063] Comparison of Gravitational Differentiation Theories:

[0064] Under conditions of uniform temperature and approximately ideal gas, the relative proportional changes of components a and b at an altitude difference Δz can be represented by a comparison relationship:

[0065] （8）

[0066] The negative sign on the right indicates that if Ma > Mb, ya / yb decreases as the height increases, meaning that the recombinant components tend to be enriched in the lower part.

[0067] Dynamic feature time fitting:

[0068] （9）

[0069] in, This represents the time constant of component i. The smaller the value, the faster the dynamic differentiation and the shorter the time required to reach equilibrium.

[0070] The present invention achieves the following technical effects compared to the prior art:

[0071] This invention enables stable injection of mixed gas under high temperature and high pressure, vertical closed static placement, and repeated sampling at multiple height positions. Combined with gas chromatography quantitative analysis to form spatial and temporal component evolution data, it obtains the dynamic differentiation law of mixed gas under the action of gravity field, providing experimental basis for stratified risk assessment of gas storage, optimization of injection and extraction system, and evaluation of the safety of mixed gas storage and transportation. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of the splicing of short core samples into long core samples according to the present invention;

[0073] Figure 2 This is a graph showing the results of gas chromatograph testing of mixed gas ratios according to the present invention (taking a mixture of CO2 and CH4 as an example).

[0074] Figure 3 This is a schematic diagram of the overall device for detecting dynamic separation of mixed gas under high temperature and high pressure according to the present invention.

[0075] Figure 4This is a partial schematic diagram of the gas injection and gas sampling analysis of the present invention (taking CO2 and CH4 as examples). Detailed Implementation

[0076] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0077] This invention discloses a dynamic detection device for gravity differentiation of mixed gas under high temperature and high pressure, comprising: a mixed gas supply and pressure stabilization module, a pressurization and heating module, a long core holder and confining pressure and temperature control module, a multi-position sampling module, a component analysis module, and a control and data acquisition module; wherein,

[0078] The mixed gas supply and pressure stabilization module is located at the far right of the device. Its outlet is first connected to the heating unit of the heating and pressurization module via a pipeline to heat the gas to a predetermined temperature. The heated gas then flows to the pressurization module, which pressurizes the gas in a hot state to achieve the target experimental pressure. The outlet of the pressurization and heating module is connected to the bottom injection end of the long core holder via a high-temperature and high-pressure resistant pipeline. The long core holder is vertically placed within the control of the confining pressure module to simulate the gravity environment of a vertical stratigraphic profile. The multi-position sampling module contains several micro-adjustment valves, which are connected to sampling holes at different heights on the side wall of the long core holder. The mixed gas from the sampling holes at different heights is collected by a gas collection bag, and the concentration of the mixed gas is tested using the component analysis module. The control and data acquisition module is connected to the pressure sensor, temperature sensor, confining pressure pump, and pressurization pump in the above modules to record system parameters.

[0079] The gas mixture supply and pressure stabilization module is used to provide gas mixtures with different ratios;

[0080] The pressurization and heating module is used to pressurize the gas mixture to the target pressure and heat it to the target temperature, with a maximum heating temperature of 150℃ and a pressure of 70MPa.

[0081] The long core holder and confining pressure temperature control module enable the long core holder to achieve axial sealing, confining pressure loading, constant temperature maintenance, and vertical placement.

[0082] The multi-location sampling module has four sampling ports at different heights along the axis of the long core sample, with a spacing of 5 to 10 cm between the sampling ports;

[0083] The component analysis module is a gas chromatograph (GC), which can perform quantitative analysis of two components and output mole fraction or volume fraction.

[0084] The control and data acquisition module is used to record and control pressure, confining pressure, temperature, injection end time, settling time, sampling time, and valve opening and closing status.

[0085] The mixed gas supply and pressure stabilization module includes two single-component gas cylinders, a gas mixing unit, a pressure regulating valve, and a shut-off valve;

[0086] The mixing unit is used to set and stably output mixed gases of different concentrations;

[0087] The pressure regulating valve is used to adjust the gas output pressure to the required range at the inlet of the pressurization module;

[0088] The shut-off valve is used to achieve isolation and safety control of the system before and after injection;

[0089] To ensure the accuracy of the mixing ratio, a mixing buffer tank is set up and equipped with a pressure sensor, and homogenization is performed before injection.

[0090] The pressurization and heating module includes a gas booster pump, an electric heating device, a temperature controller, and a temperature sensor;

[0091] The electric heating device is arranged on the main air inlet pipe that enters the long core holder. Temperature sensors can be arranged at the heater outlet and the holder inlet to monitor and correct the heat loss of the pipeline and ensure that the temperature of the gas entering the core meets the set value.

[0092] To prevent localized overheating from causing gas decomposition or a decline in the performance of sealing materials, a temperature upper limit protection system is installed.

[0093] The clamp includes a built-in core cavity, an end sealing structure, a confining pressure cavity, and a heating and insulation structure;

[0094] The confining pressure chamber is loaded with confining pressure medium by a confining pressure pump, and the confining pressure is stabilized by a closed-loop control system using a pressure sensor.

[0095] The clamp is equipped with a vertical fixed support to align the core axis with the direction of gravity, thereby promoting the differentiation driven by the density difference of the components under the action of gravity after injection and sealing.

[0096] Each sampling port is equipped with an independent high-temperature and high-pressure shut-off valve, quick connector, and sampling pipeline connected to the gas collection bag;

[0097] The sampling port is located on the outer shell of the clamp and is connected to the corresponding height position of the core cavity through a pressure-resistant micro-conduit to collect the mixed gas at different heights;

[0098] To reduce the disturbance to the system caused by sampling, a small-volume sampling pipeline and a flow-limiting structure are adopted, and the volume of each sampling is specified to be within a controllable range.

[0099] The GC is equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID), as well as necessary conversion devices.

[0100] To ensure data accuracy, the standard gas was calibrated before the experiment to obtain the response factors of each component.

[0101] The control and data acquisition module adopts a PLC control system to record parameters throughout the entire test process and automatically calculate and plot the differentiation indexes.

[0102] This invention also discloses a method for dynamic detection of gravity differentiation of a gas mixture under high temperature and high pressure, comprising the following steps:

[0103] Step 1: Core assembly and parameter design

[0104] Using a short core splicing method, several cylindrical core segments with a diameter of 2.5 cm and a length of 3–8 cm were selected, with a splicing length greater than 50 cm. Based on the completed permeability measurement experiments, the core segments were arranged in a harmonic mean manner, and the calculation formula is as follows:

[0105] （1）

[0106] The average permeability can be calculated using the above formula. Value, taken from permeability and The closest core sample is placed first at the outlet, followed by the remaining core samples. The value is calculated, and the permeability in the remaining core is taken as a factor of the new value. The core with the closest value is placed second at the outlet end, and so on, to obtain the sorting of the selected cores from the outlet end to the inlet end;

[0107] Step 2: Quantitative analysis by gas chromatography

[0108] For a gas sample collected at sampling point z at φ, the mole fraction or volume fraction of the i-th component is calculated using the following formula:

[0109] （2）

[0110] In the formula: A i F represents the chromatographic peak area. i Let M be the response factor and M be the number of components. This allows us to obtain the responses at the same time along multiple height positions z1, z2, ..., z at the same height. n Component profile ;

[0111] Step 3: Dynamic Differentiation Evaluation Indicators and Dynamic Parameters

[0112] The expressions for differentiation index, differentiation gradient, enrichment coefficient, two-component separation coefficient, theoretical correlation with gravity differentiation, and dynamic characteristic time fitting are as follows:

[0113] Differentiation Index:

[0114] Taking the target component 𝑖 as an example, the differentiation index between the upper and lower ends is defined as follows:

[0115] （3）

[0116] In the formula: Let f be the differentiation index of component 𝑖 at time t. The mole fraction of component i at the top of the highest sampling port. The mole fraction of component i at the lower end of the lowest sampling port. The height of the highest sampling port. The lowest sampling port position height, Let i be the average mole fraction of component i at all sampling points at time t;

[0117] The average value is:

[0118] （4）

[0119] In the formula: The number of sampling ports, The height position of the nth sampling port;

[0120] Differentiated gradient:

[0121] （5）

[0122] In the formula: Let be the differentiation gradient of component i at time t, and the other parameters are the same as above;

[0123] Enrichment coefficient:

[0124] Let the mole fraction of component i in the injected gas mixture be... ,but:

[0125] （6）

[0126] In the formula: Let z be the enrichment coefficient of component i relative to the injection state at time t;

[0127] Separation coefficient of the two components:

[0128] For components a and b:

[0129] （7）

[0130] In the formula: , The mole fractions of components a and b in the injected gas mixture;

[0131] Comparison of Gravitational Differentiation Theories:

[0132] Under conditions of uniform temperature and approximately ideal gas, the relative proportional changes of components a and b at an altitude difference Δz can be represented by a comparison relationship:

[0133] （8）

[0134] The negative sign on the right indicates that if Ma > Mb, ya / yb decreases as the height increases, meaning that the recombinant components tend to be enriched in the lower part.

[0135] Dynamic feature time fitting:

[0136] （9）

[0137] in, This represents the time constant of component i. The smaller the value, the faster the dynamic differentiation and the shorter the time required to reach equilibrium.

[0138] The present invention relates to an operation method for a gas mixture dynamic separation detection device under the influence of gravity and high temperature and pressure, comprising the following steps:

[0139] Step 1: Preparation and assembly of long core samples:

[0140] Select several cylindrical rock core segments with a diameter of 2.5 cm and a length of 3 to 8 cm, grind the end faces to ensure good splicing contact; arrange and combine rock cores with different permeability according to the principle of harmonized average equivalent permeability, and splice them into a long rock core with a total length of about 50 cm; calculate the equivalent permeability of the long rock core according to formula (1) to ensure that the target value of the experimental design is met;

[0141] Step 2: Sample loading, sealing, and establishment of confining pressure

[0142] Insert the spliced ​​long core into the long core holder, and complete the end sealing and pipeline connection. Start the confining pressure pump to load the confining pressure medium, gradually increase the pressure to the target pressure and stabilize it, and record the confining pressure value and stabilization time.

[0143] Step 3: Heating and Temperature Stabilization

[0144] Turn on the clamp temperature control system and heat it to the target temperature. Under the monitoring of the temperature sensor, stabilize the system temperature near the target temperature (the allowable fluctuation range can be set according to the experimental requirements).

[0145] Step 4: Inject mixed gases with different proportions and seal the system.

[0146] Set the target injection pressure (set the ratio of injection pressure to confining pressure according to experimental needs); prepare mixed gas of different concentrations through the mixing unit, and inject it into the long core holder to the target pressure through the pressurization and heating module; after injection, close the air inlet valve to put the system into a closed state;

[0147] Step 5: Place vertically and let it settle in a gravitational field

[0148] Keep the long core holder vertical, aligning the direction of gravity with the core axis; allow it to stand under constant temperature and pressure conditions, and begin timing.

[0149] Step 6: Multi-site sampling and component analysis (initial measurement)

[0150] When the pressures of the four gas sampling ports are approximately equal and remain stable, connect gas collection bags to the four different gas outlets (sampling ports) set along the height direction of the clamp; collect mixed gas samples in a uniform order of first low and then high or first high and then low (close the valve immediately after sampling at each sampling port); send the sample into the gas chromatograph to measure the proportion of mixed gas components at the four positions, and obtain the mole fraction of each component according to formula (2);

[0151] Step 7: Retest the settling time

[0152] After standing for different times, gas was taken again and the components of the mixed gas were analyzed by gas chromatography. The differentiation index, gradient, enrichment coefficient and separation coefficient were calculated using equations (3) to (7). The stability of dynamic differentiation was judged by equation (8), and the speed of dynamic differentiation of the mixed gas was quantitatively described by equation (9).

[0153] Step 8: Repeat the test by changing the gas-fuel mixture ratio.

[0154] Change the ratio of the mixed gas (e.g., change the CO2 volume fraction or the ratio of light and heavy components), repeat steps (4) to (7) to form spatial and temporal differential datasets under different ratio conditions; the experimental data provide the basic data required for risk assessment and injection-production parameter optimization for underground gas storage, gas reservoir injection and production, CCUS / EGR and other projects.

[0155] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A dynamic detection device for gravity separation of mixed gas under high temperature and high pressure, characterized in that, include: The system includes a mixed gas supply and pressure stabilization module, a pressurization and heating module, a long core holder and confining pressure and temperature control module, a multi-location sampling module, a component analysis module, and a control and data acquisition module; among which... The mixed gas supply and pressure stabilization module is located at the far right of the device. Its outlet is first connected to the heating unit of the heating and pressurization module via a pipeline to heat the gas to a predetermined temperature. The heated gas then flows to the pressurization module, which pressurizes the gas in a hot state to achieve the target experimental pressure. The outlet of the pressurization and heating module is connected to the bottom injection end of the long core holder via a high-temperature and high-pressure resistant pipeline. The long core holder is vertically placed within the control of the confining pressure module to simulate the gravity environment of a vertical stratigraphic profile. The multi-position sampling module contains several micro-adjustment valves, which are connected to sampling holes at different heights on the side wall of the long core holder. The mixed gas from the sampling holes at different heights is collected by a gas collection bag, and the concentration of the mixed gas is tested using the component analysis module. The control and data acquisition module is connected to the pressure sensor, temperature sensor, confining pressure pump, and pressurization pump in the above modules to record system parameters. The gas mixture supply and pressure stabilization module is used to provide gas mixtures with different ratios; The pressurization and heating module is used to pressurize the gas mixture to the target pressure and heat it to the target temperature, with a maximum heating temperature of 150°C and a pressure of 70MPa. The long core holder and the confining pressure and temperature control module enable the long core holder to achieve axial sealing, confining pressure loading, constant temperature maintenance, and vertical placement. The multi-location sampling module is equipped with four sampling ports at different heights along the axial direction of the long core sample, with a spacing of 5 to 10 cm between the sampling ports. The component analysis module is a gas chromatograph (GC), which can perform quantitative analysis of two components and output mole fraction or volume fraction. The control and data acquisition module is used to record and control pressure, confining pressure, temperature, injection end time, settling time, sampling time, and valve opening and closing status.

2. The dynamic detection device for gravity separation of mixed gas under high temperature and high pressure according to claim 1, characterized in that, The mixed gas supply and pressure stabilization module includes two single-component gas cylinders, a gas mixing unit, a pressure regulating valve, and a shut-off valve; The mixing unit is used to set and stably output mixed gases of different concentrations; The pressure regulating valve is used to adjust the gas output pressure to the required range at the inlet of the pressurization module. The shut-off valve is used to achieve isolation and safety control of the system before and after injection; To ensure the accuracy of the mixing ratio, a mixing buffer tank is set up and equipped with a pressure sensor, and homogenization is performed before injection.

3. The dynamic detection device for gravity separation of mixed gas under high temperature and high pressure according to claim 1, characterized in that, The pressurization and heating module includes a gas booster pump, an electric heating device, a temperature controller, and a temperature sensor; The electric heating device is arranged on the main air inlet pipe into the long core holder. The temperature sensor can be arranged at the heater outlet and the holder inlet respectively to monitor and correct the heat loss of the pipeline and ensure that the temperature of the gas entering the core meets the set value. To prevent localized overheating from causing gas decomposition or a decline in the performance of sealing materials, a temperature upper limit protection system is installed.

4. The dynamic detection device for gravity separation of mixed gas under high temperature and high pressure according to claim 1, characterized in that, The clamp includes a built-in core cavity, an end sealing structure, a confining pressure cavity, and a heating and insulation structure; The confining pressure cavity is loaded with confining pressure medium by a confining pressure pump, and the confining pressure is stabilized by a closed-loop control of a pressure sensor. The clamp is equipped with a vertical fixed support, so that the core axis is aligned with the direction of gravity, thereby promoting the differentiation driven by the density difference of the components under the action of gravity after the injection is completed and sealed.

5. The dynamic detection device for gravity separation of mixed gas under high temperature and high pressure according to claim 1, characterized in that, Each sampling port is equipped with an independent high-temperature and high-pressure shut-off valve, a quick connector, and a sampling pipeline connected to the gas collection bag; The sampling port is located on the outer shell of the clamp and is connected to the corresponding height position of the core cavity through a pressure-resistant micro-conduit, so as to collect the mixed gas at different heights; To reduce the disturbance to the system caused by sampling, a small-volume sampling pipeline and a flow-limiting structure are adopted, and the volume of each sampling is specified to be within a controllable range.

6. The dynamic detection device for gravity separation of mixed gas under high temperature and high pressure according to claim 1, characterized in that, The GC is equipped with a thermal conductivity detector (TCD), a flame ionization detector (FID), and necessary conversion devices. To ensure data accuracy, the standard gas was calibrated before the experiment to obtain the response factors of each component.

7. The dynamic detection device for gravity separation of mixed gas under high temperature and high pressure according to claim 1, characterized in that, The control and data acquisition module adopts a PLC control system to record parameters throughout the entire test process and automatically calculate and plot the differentiation index.

8. A method for dynamic detection of gravity-induced separation of mixed gas under high temperature and high pressure, characterized in that, Includes the following steps: Step 1: Core assembly and parameter design Using a short core splicing method, several cylindrical core segments with a diameter of 2.5 cm and a length of 3–8 cm were selected, with a splicing length greater than 50 cm. Based on the completed permeability measurement experiments, the core segments were arranged in a harmonic mean manner, and the calculation formula is as follows: The average permeability can be calculated using the above formula. Value, taken from permeability and The closest core sample is placed first at the outlet, followed by the remaining core samples. The value is calculated, and the permeability in the remaining core is taken as a factor of the new value. The core with the closest value is placed second at the outlet end, and so on, to obtain the sorting of the selected cores from the outlet end to the inlet end; Step 2: Quantitative analysis by gas chromatography For a gas sample collected at sampling point z at φ, the mole fraction or volume fraction of the i-th component is calculated using the following formula: In the formula: A i F represents the chromatographic peak area. i Let M be the response factor and M be the number of components. This allows us to obtain the response factors along multiple height positions z1, z2, ..., z at the same time t. n Component profile ; Step 3: Dynamic Differentiation Evaluation Indicators and Dynamic Parameters The expressions for differentiation index, differentiation gradient, enrichment coefficient, two-component separation coefficient, theoretical correlation with gravity differentiation, and dynamic characteristic time fitting are as follows: Differentiation Index: Taking the target component 𝑖 as an example, the differentiation index between the upper and lower ends is defined as follows: In the formula: Let f be the differentiation index of component 𝑖 at time t. The mole fraction of component i at the top of the highest sampling port. The mole fraction of component i at the lower end of the lowest sampling port. The height of the highest sampling port. The lowest sampling port position height, Let i be the average mole fraction of component i at all sampling points at time t; The average value is: In the formula: The number of sampling ports, The height position of the nth sampling port; Differentiated gradient: In the formula: Let be the differentiation gradient of component i at time t, and the other parameters are the same as above; Enrichment coefficient: Let the mole fraction of component i in the injected gas mixture be #imgpt19#, then: In the formula: #imgpt21# represents the height z and the enrichment coefficient of component i relative to the injection state at time t; Separation coefficient of the two components: For components a and b: In the formula: #imgpt23# and #imgpt24# are the mole fractions of components a and b in the injected gas mixture; Comparison of Gravitational Differentiation Theories: Under conditions of uniform temperature and approximately ideal gas, the relative proportional changes of components a and b at an altitude difference Δz can be represented by a comparison relationship: The negative sign on the right indicates that if Ma > Mb, ya / yb decreases as the height increases, meaning that the recombinant components tend to be enriched in the lower part. Dynamic feature time fitting: Here, #imgpt27# represents the time constant of component i. The smaller the value, the faster the dynamic differentiation and the shorter the time required to reach equilibrium.

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