A microfluidic device and experimental method for in-situ observation of phase change of solvent in thermal recovery of heavy oil

Abstract

The application discloses a microfluidic device and experimental method for in-situ observation of phase change of a solvent in thermal recovery of heavy oil. The device comprises a hot fluid supply unit, a solvent supply unit, a metering and phase state adjusting assembly, a heating, mixing, and heat preservation and delivery assembly, a microfluidic chip, a partition temperature adjusting assembly, a back pressure adjusting assembly, a temperature, pressure, and flow rate detecting assembly, a microscopic dynamic imaging assembly, a data acquisition and control unit, and a safety recovery assembly. The microfluidic chip is provided with a continuous main flow channel, a heavy oil porous medium simulation zone, and a transparent phase observation zone, and a microscope is correspondingly arranged opposite the transparent phase observation zone. The hot fluid and the solvent are continuously flowed through the microfluidic chip after metering, gasification or preheating, mixing, and heat preservation and delivery, the temperature of the transparent phase observation zone, the outlet back pressure, the injection flow rate, and the solvent ratio are adjusted, so that the solvent is condensed, vaporized, droplet nucleated, grown, coalesced, broken, migrated, and re-vaporized in the field of view of the microscope, and the interface change of the heavy oil is recorded synchronously. The application can continuously obtain microscopic images of the whole process of phase change and corresponding temperature, pressure, and flow rate data, and is suitable for pore scale research on phase state evolution and oil displacement of a solvent under thermal recovery conditions of heavy oil.

Description

Technical Field

[0001] This invention relates to the fields of heavy oil thermal recovery experimental simulation, high-temperature and high-pressure microfluidics, and multiphase flow microscopic visualization technology. Specifically, it relates to a microfluidic device and experimental method that enables solvent-containing thermal recovery fluid to continuously pass through a simulated zone of porous heavy oil media and allows in-situ observation of solvent condensation, vaporization, droplet or bubble evolution and their interaction with heavy oil under a microscope. Background Technology

[0002] Heavy oil has high viscosity and poor flowability. Typically, steam, hot water, or other hot fluids are used to raise the reservoir temperature, while solvents such as light hydrocarbons, carbon dioxide, and dimethyl ether are used to reduce the crude oil viscosity. During injection, migration, and production, the solvent may transform between gaseous, free liquid, and dissolved states, and steam may also condense simultaneously. These processes alter local heat and mass transfer patterns, the degree of heavy oil expansion and viscosity reduction, the stability of the displacement front, flow resistance within the pore throat, and solvent recovery efficiency.

[0003] While macroscopic autoclaves, windowed phase analyzers, and core displacement devices can obtain overall information such as system volume, pressure, and production, they are difficult to directly present the continuous processes of droplet nucleation, growth, coalescence, fragmentation, migration, and disappearance at the pore scale. Microfluidic chips, with their transparency, controllable pore structure, and small sample volume, are suitable for studying the dynamic behavior of fluids in heavy oil thermal recovery at the pore throat scale.

[0004] Existing microfluidic phase observation devices still have several shortcomings. First, solvents or water may prematurely condense in the vaporizer, connectors, valves, and delivery pipelines due to localized cold spots, resulting in an unclear true phase state upon entering the microarray. Second, some devices employ overall heating or cooling, making it difficult to simultaneously maintain upstream thermal recovery conditions and stably confine phase changes within the microscope's field of view. Third, temperature, pressure, flow rate, and images are often recorded separately, failing to accurately correspond to the initial appearance of droplets, interface abrupt changes, or revaporization moments. Fourth, ordinary static photography can only obtain several discrete states, failing to fully reflect the temporal relationship between phase changes and heavy oil mobilization under continuous flow conditions.

[0005] Therefore, there is a need for a microfluidic device and experimental method that can clearly control the phase state of the supply path, establish an adjustable temperature and pressure environment in a transparent observation area under continuous flow conditions, and continuously record the entire process of solvent phase changes using a microscope. Summary of the Invention

[0006] The purpose of this invention is to provide a microfluidic device and experimental method for in-situ observation of phase changes in solvents used in heavy oil thermal recovery, in order to solve the problems of unexpected phase changes in the supply path, difficulty in independently adjusting the temperature and pressure conditions in the observation area, easy deviation of the phase change location from the microscopic field of view, and asynchrony between the image and the temperature, pressure, and flow rate data.

[0007] To achieve the above objectives, this invention provides two independent supply channels for the heat transfer fluid and the solvent. Each medium, after metering and phase adjustment, enters the heating mixer and then flows into the microfluidic chip through a fully heated and insulated delivery pipeline. Depending on the target system and experimental conditions, the heat transfer fluid and solvent can be adjusted to a gaseous, superheated, liquid, or gas-liquid mixture state before entering the chip. Temperature detection and compensation heating are installed at the vaporizer, mixer, connector, valve body, and chip inlet to reduce the risk of cold spots forming at connection points.

[0008] The microfluidic chip features a continuous main channel that sequentially passes through an inlet buffer, a heavy oil porous media simulation zone, a transparent phase observation zone, and an outlet buffer. The heavy oil porous media simulation zone is used to reconstruct the reservoir pore and throat structure and pre-fill with heavy oil; the transparent phase observation zone is located directly below the microscope objective, through which the solvent-containing thermal recovery fluid flows continuously.

[0009] The chip employs zoned temperature control. The heavy oil porous medium simulation zone maintains the target thermal recovery temperature, while the transparent phase observation zone is individually heated or cooled via a thin-film heater, a semiconductor cooling chip, or a circulating heat exchanger. Combined with chip outlet back pressure regulation, the local temperature and pressure in the transparent phase observation zone can be made to cross the condensation or vaporization boundary of the target system, thereby allowing phase changes to occur within the microscope's field of view.

[0010] The dynamic microscopic imaging module consists of a microscope, a light source, a high-speed camera, and an adjustable stage. It can continuously record the nucleation, growth, coalescence, breakup, migration, and disappearance of droplets or bubbles using bright-field, dark-field, phase-contrast, or fluorescence methods. It also records the wetting and spreading, oil phase expansion, interface deformation, oil film shrinkage, and redistribution of residual oil caused by solvent contact with heavy oil. Temperature, pressure, flow rate, heating or cooling power, back pressure setpoint, and microscopic images are saved synchronously over a unified timeframe.

[0011] Compared with existing technologies, this invention has the following advantages: First, the entire process of hot fluid and solvent control, from metering, phase regulation, and mixing to chip inlet, can reduce unexpected phase changes in the supply path and improve the repeatability of the inlet phase. Second, the continuous flow in the main channel allows direct observation of the dynamic process of phase change with flow, heat transfer, and mass transfer, rather than just obtaining the static state before and after the phase change. Third, the synergistic effect of zoned temperature regulation and outlet back pressure can stably arrange the condensation, vaporization, or revaporization processes within the microscope field of view. Fourth, the simultaneous acquisition of microscopic images and local temperature, pressure, and flow rate data enables quantitative acquisition of parameters such as the dynamic phase change initiation point, droplet or bubble size, and interface migration. Fifth, the device can study the relationship between solvent phase evolution and changes in heavy oil viscosity reduction, mobilization, and residual oil distribution by changing the solvent type, injection ratio, flow rate, and temperature and pressure. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the system connection of the microfluidic device of the present invention;

[0013] Figure 2 This is a schematic diagram of the planar structure of the microfluidic chip of the present invention;

[0014] Figure 3 This is a partial cross-sectional schematic diagram of the transparent phase observation area and the microscopic dynamic imaging component of the present invention.

[0015] Reference numerals: 1-Hot fluid supply unit; 2-Solvent supply unit; 3-Hot fluid metering and phase regulation component; 4-Solvent metering and phase regulation component; 5-Heating, mixing, and heat preservation conveying component; 6-Microfluidic chip; 7-Back pressure regulation component; 8-Gas-liquid separation and solvent recovery component; 9-Microscopic dynamic imaging component; 10-Temperature, pressure, and flow rate detection and data acquisition control unit; 11-Zoned temperature regulation component; 12-Safety component; 13-Inlet buffer zone; 14-Heavy oil porous media simulation zone; 15-Transparent phase observation zone; 16-Outlet buffer zone; 17-Porous media zone heating component; 18-Observation zone heating / cooling component; 19-Transparent pressure-resistant cover plate; 20-Continuous main channel; 21-Microscope; 22-Light source; 23-Chip mounting stage; 24-Local temperature sensor; 25-Pressure detection interface. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are used to illustrate the technical concept and implementation of the present invention, and are not intended to limit the scope of protection of the present invention. Materials, dimensions, and control parameters not specifically mentioned can be determined based on solvent properties, target temperature and pressure, and equipment rated conditions.

[0017] Example 1: Device Structure and Working Principle

[0018] like Figure 1 As shown, the hot fluid supply unit 1 and the solvent supply unit 2 are respectively connected to the hot fluid metering and phase adjustment component 3 and the solvent metering and phase adjustment component 4. The hot fluid can be water vapor, hot water, nitrogen, carbon dioxide or a combination thereof; the solvent can be light hydrocarbons such as propane, butane, n-pentane, and n-hexane, or it can be dimethyl ether, carbon dioxide or other volatile fluids suitable for reducing the viscosity of heavy oil.

[0019] The liquid medium is preferably first precisely metered by a high-pressure metering pump at a lower temperature before entering a small-volume continuous flow vaporizer or preheater. The gaseous medium can be metered by a mass flow controller. The two media streams are combined in the heating, mixing, and heat-insulating conveying assembly 5, and then transported to the microfluidic chip 6 via a heated pipeline. Heating elements and temperature sensors are respectively installed in the vaporizer, mixer, connector, valve body, and chip inlet, and the temperature is controlled based on the real-time local pressure and the target phase state.

[0020] The outlet of the microfluidic chip 6 is connected to the back pressure regulation component 7, and downstream of the back pressure regulation component 7 is the gas-liquid separation and solvent recovery component 8. The temperature, pressure, and flow rate detection and data acquisition control unit 10 is used to read the temperature and pressure near the inlet, outlet, and transparent phase observation area, as well as the two injection flow rates, and to control the zone temperature regulation component 11, the back pressure regulation component 7, and the microscopic dynamic imaging component 9. The safety component 12 includes a check valve, an overpressure relief valve, an inert gas purging port, and a leak detector.

[0021] Example 2: Microfluidic chip and microscopic dynamic observation structure

[0022] like Figure 2 As shown, the microfluidic chip 6 includes an inlet buffer zone 13, a heavy oil porous media simulation zone 14, a transparent phase observation zone 15, and an outlet buffer zone 16, with each zone sequentially connected by a continuous main channel 20. The heavy oil porous media simulation zone 14 can be a regular or random micropillar array, a pore-throat network, a fracture-pore network, or a replaceable real core section. The microchannel depth can be 20–500 μm, and the equivalent pore-throat size can be 10–500 μm, with the specific dimensions determined based on microscope resolution, target flow rate, and allowable pressure difference.

[0023] The microfluidic chip 6 can be made of glass-silicon, quartz-silicon, heat-resistant glass-metal, or other transparent, heat- and pressure-resistant materials. A transparent, pressure-resistant cover plate 19 is provided above the transparent phase observation area 15, and its surface flatness and thickness meet the working distance requirements of the microscope objective 21. To reduce the obstruction of bubbles or droplets by the flow channel height, the transparent phase observation area 15 can adopt a constant-depth flow channel, or a gradually expanding observation channel can be set to reduce the local flow velocity and extend the observation time.

[0024] like Figure 3 As shown, the microscope objective 21 is positioned above the transparent pressure-resistant cover plate 19 and aligned with the transparent phase observation area 15. The light source 22 is positioned above or below the chip. The chip stage 23 is used to limit the chip's displacement during heating, cooling, and pressurization processes. The porous media region heating assembly 17 is used to maintain the thermal recovery temperature of the heavy oil porous media simulation region 14, and the observation area heating / cooling assembly 18 is used to change the local temperature of the transparent phase observation area 15. The local temperature sensor 24 is arranged close to the transparent phase observation area 15, and the pressure detection interface 25 is located upstream or downstream of the transparent phase observation area 15 to estimate or measure the actual pressure in that area.

[0025] Example 3: Heavy Oil Pre-conditioning, System Calibration, and Control Test

[0026] Before the formal test, the flow path was sequentially cleaned using a cleaning agent compatible with the chip material, deionized water, and inert gas, followed by vacuum drying. The device was then subjected to airtightness and pressure tests, ensuring the pressure did not exceed the allowable operating pressure of any component. The temperature sensor, pressure sensor, flow meter, back pressure regulator, and microscopic imaging timestamp were calibrated.

[0027] The heavy oil is heated to an injectable state and slowly injected from the chip outlet side or a dedicated saturation port until the heavy oil porous medium simulation zone 14 reaches the target saturation. If simulating the original water content conditions is required, bound water can be established first before injecting the heavy oil. After the heavy oil is pre-set, it is allowed to stand at the target initial temperature until the oil phase distribution and device pressure in the image stabilize.

[0028] At least three types of control experiments should be set up. A solvent-free thermal fluid control is used to identify vapor condensation and pure heat effects; a heavy oil-free chip control is used to obtain gas-liquid phase transition images of the solvent in air channels or porous media; and a solvent-only phase transition control is used to establish image characteristics of the gas phase, droplets, and bubbles under different temperatures and pressures. If necessary, a known fluorescent tracer can be added, or the autofluorescence of crude oil can be used to establish an oil phase boundary identification baseline.

[0029] Example 4: Observation of dynamic phase change under continuous flow conditions

[0030] Taking the n-pentane-steam-heavy oil system as an example, the target temperature and pressure range is first determined based on phase equilibrium calculations, pre-experimentation in a high-pressure reactor, or publicly available physical property data. The porous media heating component 17 and the heat tracing system are then activated to bring the heavy oil porous media simulation zone 14 to the target thermal recovery temperature; the back pressure regulating component 7 is then set to stabilize the system pressure. Subsequently, the hot fluid and n-pentane injection are initiated, and the flow rates of both are gradually adjusted to the target ratio.

[0031] In the initial stage, the transparent phase observation zone 15 is maintained at a temperature where the solvent is unlikely to condense, confirming that the fluid entering the microscopic field of view is in a stable state. The high-speed camera begins continuous recording, and the data acquisition and control unit 10 synchronously records the time, inlet and outlet temperatures, local observation zone temperature, system pressure, pressure difference, and injection flow rate.

[0032] During condensation observation, the outlet back pressure can be kept relatively stable while gradually decreasing the temperature of the transparent phase observation area 15, or the observation area temperature can be kept relatively stable while gradually increasing the outlet back pressure. As the local temperature and pressure conditions cross the dynamic condensation boundary, tiny droplets or liquid films first appear in the microscope's field of view. Subsequently, the nucleation location of droplets, the increase in number, the growth in size, the coalescence of adjacent droplets, the deformation or breakage caused by flow shear, and the migration of droplets along the orifice wall or flow channel can be observed.

[0033] During vaporization or revaporization observation, the temperature of the transparent phase observation zone 15 is increased or the outlet back pressure is decreased in the opposite direction. The microscope continuously records the processes of droplet shrinkage, interface retreat, bubble formation, bubble expansion, and the eventual disappearance of the liquid phase. By adjusting the temperature and pressure in both directions, the dynamic differences between the condensation and vaporization processes can be compared.

[0034] When heavy oil is present in the transparent phase observation zone 15, the following should be recorded: the spreading and penetration of the solvent condensate after contact with the heavy oil; the expansion of the oil phase boundary; the reduction of the oil film thickness; the desorption of crude oil from the pore wall; the stretching and migration of oil droplets; and the changes in the distribution of local residual oil. These phenomena, combined with synchronous temperature, pressure, and flow rate data, can be used to analyze the impact of solvent phase changes on the viscosity reduction and mobility of heavy oil.

[0035] Between different operating conditions, the initial temperature and pressure should be restored first, and injection should continue until the microscopic field of view and pressure difference stabilize again before changing the solvent ratio, total flow rate, temperature change rate, or back pressure change rate. To reduce errors caused by thermal inertia, each temperature step is maintained until the local temperature sensor reading 24 stabilizes, and the measured local temperature, rather than the heater set temperature, is used as the basis for phase analysis.

[0036] Example 5: Image Processing and Phase Transition Criteria

[0037] Microscopic image processing includes distortion correction, background subtraction, brightness normalization, phase segmentation, and target tracking. Gas, liquid, and oil phases can be identified based on grayscale, color, texture, fluorescence intensity, and interface morphology. For droplets or bubbles, their number, area, perimeter, equivalent diameter, roundness, aspect ratio, and centroid position are calculated, and their migration velocity and trajectory are obtained through adjacent frame matching.

[0038] The dynamic phase transition initiation point is preferably determined using a continuous image criterion. When a new liquid or gaseous target exists in three or more consecutive images, and the target area exceeds a pre-calibrated noise threshold, the phase change is considered to have begun. The measured temperature and pressure of the transparent phase observation area 15 at that moment are defined as the apparent dynamic phase transition initiation conditions. This condition reflects the dynamic response under specific flow rates, channel dimensions, and temperature and pressure change rates, and is not equivalent to the thermodynamic phase boundary under infinite equilibrium time.

[0039] Based on the image sequence, the generation frequency, number density, scale distribution, coalescence frequency, breakup frequency, area ratio, interface migration rate, and phase transition region propagation rate of droplets or bubbles can be further calculated. For heavy oil systems, the changes in oil phase area, oil phase centroid displacement, oil film thickness, number of oil droplet desorptions, and remaining oil area can be calculated, and their correlations with local temperature, pressure, pressure difference, and solvent injection volume can be established.

[0040] Example 6: Replaceable Structures and Applicable Scope

[0041] The transparent phase observation area 15 can be located downstream of the heavy oil porous media simulation area 14, or it can be directly located inside the porous media simulation area. When it is necessary to compare changes along the flow path, two or more transparent observation windows can be set along the continuous main flow channel 20, and the microscopic field of view can be moved sequentially by an electric stage, or multiple microscopic imaging channels can be configured for simultaneous observation. All of the above observation windows are part of the continuous main flow channel.

[0042] The zoned temperature control component 11 can employ unilateral heating or cooling, top and bottom clamping heat exchange, micro-circulating flow channel heat exchange, or thin-film resistance heating. The back pressure control component 7 can employ a mechanical back pressure valve or an electronic back pressure regulator. Microscopic dynamic imaging can employ ordinary high-speed bright-field imaging, or it can combine dark-field, phase contrast, or fluorescence imaging as needed for phase region identification.

[0043] This invention is applicable not only to steam-light hydrocarbon solvent systems, but also to hot water-solvent, non-condensable gas-solvent, multi-solvent blends, and carbon dioxide-assisted thermal recovery systems. For media that may reach a supercritical state, temperature and pressure paths can be set according to the corresponding physical property boundaries, and state changes can be characterized by density differences, interface disappearance, and oil phase response.

[0044] The above embodiments are used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Any equivalent substitutions or combinations made based on the concept of the present invention regarding the medium supply method, chip aperture structure, observation window position, temperature and pressure regulation method, microscopic imaging method, and data processing method shall fall within the scope of protection of the present invention.

Claims

1. A microfluidic device for in-situ observation of solvent phase changes in heavy oil thermal recovery, characterized in that, The system includes a hot fluid supply unit, a solvent supply unit, a metering and phase regulation component, a heating, mixing, and heat preservation conveying component, a microfluidic chip, a zoned temperature regulation component, a back pressure regulation component, a temperature, pressure, and flow detection component, a microscopic dynamic imaging component, a data acquisition and control unit, and a safety recovery component. The microfluidic chip has a continuous main channel that sequentially connects to an inlet buffer zone, a heavy oil porous media simulation zone, a transparent phase observation zone, and an outlet buffer zone. The zoned temperature regulation component is used to adjust the temperature of the heavy oil porous media simulation zone and the transparent phase observation zone respectively. The back pressure regulation component is connected to the outlet of the microfluidic chip. The microscope objective of the microscopic dynamic imaging component is correspondingly positioned to the transparent phase observation zone. During the continuous flow of the solvent-containing thermally recovered fluid through the transparent phase observation zone, the solvent undergoes a phase change within the microscope's field of view by adjusting the temperature of the transparent phase observation zone and / or the outlet back pressure, and the microscopic dynamic imaging component continuously acquires images of this phase change.

2. The microfluidic device according to claim 1, characterized in that, The hot fluid supply unit is used to supply steam, hot water, non-condensable gas or a combination thereof; the solvent supply unit is used to supply light hydrocarbon solvent, carbon dioxide, dimethyl ether or a combination thereof; the metering and phase regulation assembly includes one or more of the following: liquid metering pump, gas mass flow controller, continuous flow vaporizer, preheater and temperature controller.

3. The microfluidic device according to claim 1, characterized in that, The heating, mixing, and heat preservation delivery assembly includes a heating mixer, a heat tracing pipeline, an insulation layer, and compensating heating elements disposed at the joint, valve body, and microfluidic chip inlet. The heating, mixing, and heat preservation delivery assembly is used to maintain the hot fluid and solvent in a set injection phase state before entering the microfluidic chip, reducing unexpected condensation or vaporization in the supply path.

4. The microfluidic device according to claim 1, characterized in that, The microfluidic chip includes a transparent pressure-resistant cover plate, a substrate, and a continuous main channel formed between the two; the heavy oil porous medium simulation region is composed of a regular or random micropillar array, a pore throat network, a crack-pore combination network, or a combination thereof; and the transparent phase observation region is provided with a transparent observation window corresponding to the optical path of the microscope objective.

5. The microfluidic device according to claim 1, characterized in that, The microscopic dynamic imaging assembly includes a microscope, a transmitted light source or a reflected light source, a high-speed camera, and an adjustable stage; the microscope employs one or more of bright-field, dark-field, phase-contrast, or fluorescence imaging modes, and the high-speed camera is used to continuously record the nucleation, growth, coalescence, breakup, migration, disappearance, and changes in the oil phase interface of droplets or bubbles.

6. The microfluidic device according to claim 1, characterized in that, The temperature, pressure and flow detection component includes a temperature sensor, a pressure sensor and a flow sensor disposed on the inlet and outlet sides of the microfluidic chip, as well as a local temperature sensor disposed near the transparent phase observation area; the data acquisition and control unit synchronously records temperature, pressure, flow, heating or cooling power, back pressure setpoint and microscopic image with a unified timestamp.

7. The microfluidic device according to claim 1, characterized in that, The safety recovery assembly includes a check valve, an overpressure relief assembly, an inert gas purging assembly, a leak detection assembly, and a gas-liquid separation and solvent recovery assembly located downstream of the back pressure regulating assembly; the pipelines, joints, valve bodies, and microfluidic chips that come into contact with the solvent are made of materials that are temperature-resistant, pressure-resistant, and compatible with the solvent used.

8. An experimental method for in-situ observation of solvent phase changes in heavy oil thermal recovery using the microfluidic device according to any one of claims 1 to 7, characterized in that, The process includes the following steps: cleaning, airtightness checking, and temperature and pressure calibration of the microfluidic device; pre-placing heavy oil in the heavy oil porous medium simulation zone of the microfluidic chip and establishing initial temperature and pressure; metering and adjusting the hot fluid and solvent to the set injection phase, and continuously injecting them into the microfluidic chip after heating, mixing, and heat preservation; adjusting the zone temperature regulation component and back pressure regulation component to make the temperature and pressure of the transparent phase observation zone change according to the set path; while the solvent-containing thermally recovered fluid continuously passes through the transparent phase observation zone, continuously acquiring phase change images using a microscopic dynamic imaging component, and simultaneously acquiring temperature, pressure, and flow rate data; determining the solvent phase change and its relationship with the heavy oil interface evolution based on the microscopic images and synchronous data.

9. The experimental method according to claim 8, characterized in that, The temperature and pressure regulation methods for the transparent phase observation zone include maintaining a basically stable outlet back pressure while lowering or raising the observation zone temperature, maintaining a basically stable observation zone temperature while raising or lowering the outlet back pressure, or simultaneously changing the observation zone temperature and outlet back pressure. Continuous injection is maintained under each temperature and pressure path, and forward and reverse adjustments are made to observe solvent condensation, vaporization, and their reversible changes.

10. The experimental method according to claim 8, characterized in that, By changing one or more of the following: solvent type, solvent-to-thermal fluid ratio, total injection flow rate, temperature change rate, back pressure change rate, and initial saturation of heavy oil, dynamic phase state image sequences under different operating conditions are obtained. Background correction, phase region segmentation, and target tracking are performed on the image sequences to obtain the initial phase change position, apparent phase change initiation temperature and pressure, droplet or bubble number density, equivalent diameter, generation frequency, coalescence or breakup frequency, migration speed, gas-liquid area ratio, and oil phase interface displacement.

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