Ultrasonic-enhanced water-oil displacement recovery ratio experiment system based on CT (Computed Tomography) real-time imaging

Abstract

The invention discloses an ultrasonic enhanced water-oil displacement recovery ratio experiment system based on CT real-time imaging, and belongs to the technical field of oil and gas exploitation experiments. The system is composed of a core clamping and pressure control system, an ultrasonic excitation system, an injection and extraction system, a monitoring and data acquisition system and a data analysis and optimization system. A core holder can accurately simulate underground reservoir pressure and fluid conditions. The ultrasonic excitation system reduces the oil-water interfacial tension through the cavitation effect and micro-vibration, and improves the fluidity and release effect of oil drops; the injection and extraction system is used for accurately controlling the injection flow rate and pressure of displacement liquid to form a stable oil displacement gradient; the monitoring system dynamically captures the core internal oil-water leading edge propulsion, residual oil distribution and ultrasonic cavitation bubble evolution process, and visualization of an ultrasonic energy transfer path under the pore scale is achieved for the first time. The system can effectively research the influence of ultrasonic enhancement on the water drive recovery efficiency, and provides experimental basis and technical support for improving the oilfield development efficiency.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas production experimental technology, specifically to a water-flooding oil recovery enhancement experimental system and method based on the synergistic effects of real-time computed tomography (CT) imaging and ultrasound. By integrating high-resolution CT dynamic monitoring with multi-frequency ultrasonic enhancement technology, this invention achieves three-dimensional visualization of the displacement process, intelligent optimization of ultrasonic parameters, and multi-physics field coupling simulation, providing theoretical and experimental support for improving oil recovery. Background Art

[0002] During the development of oil and gas fields, with the increase in the degree of development and the extension of the recovery time, the distribution of remaining oil in the reservoir becomes increasingly complex, the water flooding oil recovery rate gradually decreases, and the remaining oil is difficult to effectively mobilize. At present, traditional chemical flooding and physical production enhancement methods have the problems of high cost, poor adaptability, and large environmental impact. There is an urgent need to explore new technologies to enhance oil recovery. Ultrasonic technology is a green and economical enhancement method. Due to its cavitation effect, micro-vibration effect and acoustic streaming effect, it can reduce the oil-water interfacial tension and improve the fluid flow and displacement efficiency in the core pores. However, the specific enhancement mechanism and parameter optimization of ultrasonic technology in the water flooding process have not been fully revealed. Existing ultrasonic enhancement experiments mostly use fixed frequency and power, lacking adaptability to reservoir heterogeneity and dynamic displacement processes, and easily resulting in energy waste or insufficient local effect. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention provides an ultrasonically enhanced water-flooding oil recovery efficiency improvement experimental system based on CT real-time imaging. CT scanning technology, as a non-destructive testing method, can provide high-resolution internal structure images. Through multi-dimensional monitoring and optimization analysis, the oil displacement process under the action of ultrasound is simulated, and the effects of displacement visualization and ultrasonic parameter optimization are achieved. The mechanism of ultrasonic enhancement on oil recovery efficiency is revealed, providing a scientific basis and practical guidance for oilfield production increase and development.

[0004] To achieve the above objectives, the present invention adopts the following technical solutions: an ultrasonically enhanced water flooding oil recovery enhancement experimental system based on CT real-time imaging, which includes a core holder and an ultrasonic excitation system, an injection and production system, a CT imaging system, a monitoring and data acquisition system, and a data analysis and optimization system;

[0005] The confining pressure pump is connected to the injection end of the core holder through a pipeline provided with a confining pressure sensor, the precision pressure pump is connected to the inlet ends of the liquid phase storage tank and the oil phase storage tank, and the outlet ends of the liquid phase storage tank and the oil phase storage tank are connected to the injection end of the core holder;

[0006] The production end of the core holder is connected to the oil-water separator, on which a production and collection system is installed;

[0007] An injection pressure sensor is provided at the injection end of the core holder, a production pressure sensor is provided at the production end, and a temperature sensor is also provided on the core holder;

[0008] The ultrasonic excitation system uses an ultrasonic generator connected to a waveguide device, which acts on the core holder;

[0009] The monitoring and data acquisition system includes a CT imaging module, which scans the initial core to obtain a three-dimensional model of the pore structure. After the displacement fluid is injected until the core is fully saturated, the initial water saturation is recorded, and the CT grayscale value is calibrated to obtain real-time images of the three-dimensional structure and fluid distribution inside the core. At the same time, the ultrasonic equipment uses pulsed ultrasonic emission, which is staggered with the CT scanning sequence to ensure imaging clarity.

[0010] Furthermore, flow sensors are provided on the pipelines connecting the outlet ends of the liquid phase storage tank and the oil phase storage tank to the injection end of the core holder.

[0011] Furthermore, the experimental system is also provided with a monitoring and data acquisition system, and the data system is electrically connected to the flow sensor, the confining pressure sensor, the injection pressure sensor, the production pressure sensor, and the production collection system.

[0012] The experimental method of the ultrasonic enhanced water flooding oil recovery enhancement experimental system includes the following steps:

[0013] S1. Load the experimental core into the core holder and start the confining pressure pump to increase the confining pressure;

[0014] A precision pressure pump was used to inject displacement fluid at a constant flow rate. Real-time CT scanning was initiated to obtain images of the oil-water front advance. The pressure and flow at the injection end of the core holder were monitored using an injection pressure sensor and a flow sensor, respectively, to maintain the pore pressure gradient required for the experiment. Pressure, temperature, and flow data at the injection and production ends were collected.

[0015] S2. When the recovery rate stabilizes, the ultrasonic generator is activated to generate a high-frequency electrical signal of the set frequency and power. This signal is converted into mechanical vibrations by the transducer, generating ultrasonic waves. The ultrasonic waves are then transmitted to the displacement fluid in the core holder and the core surface via a waveguide, focusing the ultrasonic energy.

[0016] S3. Analyze the oil-residual area based on the CT image, and use the waveguide device to directional radiate and focus the ultrasonic energy on the high-oil-content area. If the CT image shows oil film retention, switch to high-frequency ultrasonic wave to enhance the micro-vibration effect;

[0017] S4. Start the precision pressure pump to control the injection flow rate and pressure of the displacement fluid. The displacement fluid flows from the injection end of the core holder through the core and pushes the oil-water mixture to the production end.

[0018] S5. After the fluid is completely displaced within the core, it flows out of the production port and into the oil-water separator. The oil-water ratio of the produced fluid is recorded for analysis of the displacement effect. The volume and time of the discharged fluid are recorded through the production collection system. CT images of the water flooding and ultrasonic enhancement stages are compared to calculate the recovery factor and evaluate the displacement efficiency.

[0019] This invention introduces CT scanning technology based on the existing ultrasonic enhanced water flooding experimental system. By simulating underground reservoir conditions, the ultrasonic technology is used to reduce the oil-water interfacial tension, improve the release and fluidity of oil droplets, and thus improve the recovery rate of water flooding. At the same time, the system uses real-time CT scanning to obtain the three-dimensional structure and fluid distribution information inside the reservoir, further optimizing the displacement process. The system aims to reveal the mechanism of action of ultrasonic enhanced oil flooding in multiple dimensions, optimize the key parameters of the displacement process, and provide scientific basis and technical support for the application of ultrasonic technology in actual reservoir development. At the same time, by integrating real-time monitoring and data analysis functions, the invention realizes precise control of the experimental process and comprehensive evaluation of the results, providing a set of efficient, economical and green technical solutions for increasing oil field production.

[0020] The beneficial effects of the present invention are: first, the cavitation effect, micro-vibration and acoustic streaming of ultrasound are utilized to reduce the oil-water interfacial tension, improve the fluidity and release efficiency of residual oil, and thus significantly enhance the water-flooding oil recovery rate; second, CT scanning technology provides high-resolution three-dimensional internal structure images, which can intuitively display the oil-water distribution and flow path inside the reservoir. Combining CT images and multidimensional data, the ultrasonic enhancement mechanism can be more accurately evaluated, ultrasonic parameters can be optimized, and real-time monitoring of macroscopic parameters and microscopic phenomena can be achieved, comprehensively revealing the dynamic process and mechanism of action of ultrasonic enhanced displacement; third, through data analysis and optimization system, the displacement effect can be accurately evaluated and experimental parameters can be optimized, providing a reliable basis for the application of ultrasonic enhancement technology under different geological conditions; fourth, the system design is modular, with good experimental flexibility and scalability, laying a solid foundation for the promotion of ultrasonic enhancement technology in oil and gas field development. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an ultrasonic enhanced water flooding oil recovery improvement experimental system based on CT real-time imaging.

[0022] 1. Confining pressure pump, 2. Core holder, 3. Waveguide, 4. Ultrasonic generator, 5. Precision pressure pump, 6. Liquid phase storage tank, 7. Oil phase storage tank, 8. Flow sensor, 9. Confining pressure sensor, 10. Injection pressure sensor, 11. Temperature sensor, 12. Pump, 13. Oil-water separator, 14. Production collection system, 15. Data processing system, 16. Production pressure sensor. 17. Microfocus CT scanner DETAILED DESCRIPTION

[0023] Ultrasonic enhanced water flooding oil recovery enhancement experimental system based on CT real-time imaging, which includes a core clamping and pressure control system, an ultrasonic excitation system, an injection and production system, a monitoring and data acquisition system, and a data analysis and optimization system;

[0024] The core holding and pressure control system simulates the pressure and fluid environment of the underground oil reservoir. The core clamp fixes the artificial core, the confining pressure system applies confining pressure to maintain the reservoir pressure, and the pore pressure control system adjusts the injection and production pressures of the displacement fluid to ensure the stability and controllability of the experimental conditions.

[0025] During the displacement process, the ultrasonic excitation system reduces oil-water interfacial tension through high-frequency vibration and cavitation, promoting the release and flow of residual oil. The ultrasonic generator generates an ultrasonic signal of a set frequency and power. This energy is concentrated through a transducer and waveguide at the fluid-rock interface within the core.

[0026] The injection and production system controls the injection rate and pressure of the displacement fluid, which flows from the injection port through the core, pushing the oil-water mixture to the production port. The production system uses oil-water separation and flow recording devices to collect real-time data on the flow rate and composition of the discharged fluid, providing a basis for calculating displacement efficiency.

[0027] The monitoring and data acquisition system integrates temperature, pressure, and flow sensors and a microfocus CT scanner to dynamically capture the advancement of the oil-water front, residual oil distribution, and ultrasonic cavitation bubble evolution inside the core, achieving for the first time the visualization of the ultrasonic energy transfer path at the pore scale. The data acquisition module transmits the output data of the sensors and CT scanner to the data processing terminal, and performs a comprehensive analysis based on the experimental parameters.

[0028] In some specific embodiments, temperature sensors are distributed in the core holder and the displacement fluid flow path to record temperature changes during the displacement process; pressure sensors are installed at the injection end and the production end to monitor the pore pressure and pressure gradient in real time; flow sensors are used to accurately measure the injection flow rate and production flow rate of the displacement fluid; and a microscopic camera is located at the production end to capture the release and migration behavior of microscopic oil droplets during the displacement process.

[0029] The data analysis and optimization system, comprised of a data processing terminal, analysis software, and a parameter optimization module, is designed to comprehensively process the multidimensional data collected by the monitoring system and provide experimental optimization solutions. The data processing terminal receives raw data on temperature, pressure, flow rate, and the microscope camera. After filtering, calibration, and data fusion, it compares CT images from the waterflooding and ultrasonic enhancement phases, quantifies the increase in recovery, and extracts key metrics such as the rate of change in the oil-water interface area and the uniformity of the displacement front to determine the optimal ultrasonic parameter combination.

[0030] The analysis software quantitatively analyzes the displacement efficiency, recovery rate and oil-water distribution patterns, and combines microscopic images to extract the characteristics of oil droplet migration and interface changes, revealing the mechanism of ultrasonic enhancement. The parameter optimization module optimizes key experimental parameters such as ultrasonic frequency, power, displacement flow rate, etc. based on experimental data through simulation and regression algorithms to determine the optimal displacement conditions.

[0031] The data analysis and optimization system performs multi-dimensional processing on experimental data, quantitatively evaluating the effectiveness of ultrasonically enhanced oil displacement, revealing the mechanisms at work during the displacement process, and outputting the optimal experimental plan and displacement conditions through a parameter optimization module. This entire process enables precise experimental research on ultrasonically enhanced water flooding, providing an important experimental platform and technical support for improving oil recovery and optimizing actual oilfield development.

[0032] The confining pressure pump (such as hydraulic oil or nitrogen) gradually increases the confining pressure at a set rate (0.4 MPa / min) to simulate the confining pressure conditions of the underground reservoir until the experimental target value (8 MPa) is reached;

[0033] During the displacement process, ultrasound reduces oil-water interfacial tension through cavitation, microvibration, and acoustic streaming, promoting the release of oil droplets and improving their fluidity while also increasing the seepage capacity of the displacement fluid. This system studies the impact of ultrasonic parameters on water-flooded oil recovery by adjusting them, providing an experimental basis for optimizing ultrasonic enhancement technology. A precision injection pump injects the displacement fluid into the core holder at a set flow rate (0.5 mL / min), maintaining a stable fluid injection rate and pressure using a flow control device.

[0034] All monitoring equipment transmits real-time data to the processing terminal through the data acquisition module, and conducts comprehensive analysis based on experimental parameters to generate dynamic characteristic curves of temperature, pressure, flow rate and micro-interface changes, providing detailed data support for displacement efficiency evaluation and ultrasonic enhancement mechanism research; the data analysis and optimization system ultimately outputs the optimized experimental plan and prediction results, providing a scientific basis and technical support for the performance improvement and practical application of ultrasonic enhanced water flooding.

[0035] Example 1

[0036] Figure 1This is an ultrasonically enhanced water-flooding oil recovery enhancement experimental system based on real-time CT imaging. The core holding and pressure control system simulates the pressure and fluid environment of the underground reservoir. A core holder 2 secures the artificial core, a confining pressure pump 1 applies confining pressure to maintain reservoir pressure, and a pore pressure control system regulates the injection and withdrawal pressures of the displacement fluid, ensuring the stability and controllability of experimental conditions. During the displacement process, the ultrasonic excitation system reduces the oil-water interfacial tension through high-frequency vibration and cavitation effects, promoting the release and flow of residual oil. An ultrasonic generator 4 generates an ultrasonic signal of a set frequency and power. This signal, through a transducer 4 and a waveguide device 3, concentrates the energy on the fluid-rock interface within the core. The injection and withdrawal system controls the injection rate and pressure of the displacement fluid, which flows from the injection port through the core, pushing the oil-water mixture to the withdrawal port. The recovery system, through an oil-water separator 13 and a flow recording device 14, collects real-time data on the flow and composition of the effluent, providing a basis for calculating displacement efficiency. The monitoring and data acquisition system integrates temperature 11, pressure 10, flow sensors 8, and a microfocus CT scanner 17 to dynamically capture the advancement of the oil-water front, residual oil distribution, and the evolution of ultrasonic cavitation bubbles within the core, achieving for the first time the visualization of ultrasonic energy transfer paths at the pore scale. The data acquisition module transmits the imaging output data from the sensors and CT scanner 17 to the data processing terminal 15 for comprehensive analysis based on experimental parameters. The data analysis and optimization system performs multi-dimensional processing on the experimental data, quantitatively evaluating the effectiveness of ultrasonically enhanced oil displacement and revealing the mechanisms at work during the displacement process. The parameter optimization module then outputs the optimal experimental plan and displacement conditions.

Claims

1. Ultrasonic enhanced water flooding oil recovery enhancement experimental system based on CT real-time imaging, characterized by: The system includes a core holder (2) and an ultrasonic excitation system, an injection and extraction system, a CT imaging system, a monitoring and data acquisition system, and a data analysis and optimization system; The confining pressure pump (1) is connected to the injection end of the core holder (2) through a pipeline provided with a confining pressure sensor (9), the precision pressure pump (5) is connected to the inlet ends of the liquid phase storage tank (6) and the oil phase storage tank (7), and the outlet ends of the liquid phase storage tank (6) and the oil phase storage tank (7) are connected to the injection end of the core holder (2); The production end of the core holder (2) is connected to an oil-water separator (13), on which a production collection system (14) is provided; An injection pressure sensor (10) is provided at the injection end of the core holder (2), a production pressure sensor (16) is provided at the production end thereof, and a temperature sensor (11) is also provided on the core holder (2); The ultrasonic excitation system uses an ultrasonic generator (4) connected to a waveguide device (3), and the waveguide device (3) acts on the core holder (2); The monitoring and data acquisition system includes a CT imaging module (17) to scan the initial core and obtain a three-dimensional model of the pore structure. After the displacement fluid is injected until the core is completely saturated, the initial water saturation is recorded, and the CT grayscale value is calibrated to obtain real-time three-dimensional structure and fluid distribution images inside the core. At the same time, the ultrasonic equipment uses pulsed ultrasonic emission, which is staggered with the CT scanning sequence to ensure imaging clarity.

2. The ultrasonic enhanced water flooding oil recovery efficiency improvement experimental system based on CT real-time imaging according to claim 1 is characterized in that: A flow sensor (8) is provided on the pipeline connecting the outlet ends of the liquid phase storage tank (6) and the oil phase storage tank (7) to the injection end of the core holder (2).

3. The ultrasonic enhanced water flooding oil recovery enhancement experimental system based on CT real-time imaging according to claim 2 is characterized in that: The experimental system is also provided with a monitoring and data acquisition system (15), and the data system (15) is electrically connected to the flow sensor (8), the confining pressure sensor (9), the injection pressure sensor (10), the production pressure sensor (16), and the production collection system (14).

4. The experimental method of the ultrasonic enhanced water flooding oil recovery enhancement experimental system according to claim 3, characterized in that: The following steps are involved: S1. Load the experimental core into the core holder (2) and start the confining pressure pump (1) to increase the confining pressure; The displacement fluid is injected at a constant flow rate through a precision pressure pump (5), and a CT real-time scan is started to obtain an oil-water front advancement image. The pressure and flow rate at the injection end of the core holder (2) are monitored by an injection pressure sensor (10) and a flow rate sensor (8), respectively, to maintain the pore pressure gradient required for the experiment, and the pressure, temperature and flow rate data of the injection end / production end are collected; S2. When the recovery rate tends to be stable, the ultrasonic generator (4) is started to generate a high-frequency electrical signal of a set frequency and power, which is converted into mechanical vibration by the transducer to generate ultrasonic waves; the ultrasonic waves are transmitted to the displacement fluid in the core holder (2) and the core surface through the waveguide device (3), thereby achieving the focusing effect of the ultrasonic energy; S3. Analyze the oil-residual areas based on the CT image, and use the waveguide device to directional radiate and focus the ultrasonic energy on the high-oil-content area. If the CT image shows oil film retention (grayscale value > 10%), switch to high-frequency ultrasonic waves to enhance the micro-vibration effect; S4. Start the precision pressure pump (5) to control the injection flow rate and pressure of the displacement fluid. The displacement fluid flows from the injection end of the core holder (2) through the core to push the oil-water mixture to the production end; S5. After the fluid has been displaced inside the core, it flows out from the production end and enters the oil-water separator (13). The oil-water ratio of the produced fluid is recorded for analyzing the displacement effect. The volume and time of the discharged fluid are recorded through the production collection system (14). The CT images of the water flooding stage and the ultrasonic enhancement stage are compared to calculate the recovery rate and evaluate the displacement efficiency.

Images