A method and apparatus for laboratory investigation of ultrasonic visualization solutions to near wellbore contamination

Abstract

The present application relates to a kind of laboratory for studying the method and device for solving near well pollution with ultrasonic visualization.The present application relates to the technical field of oil and gas field development and stimulation, and the device is composed of ultrasonic system, displacement system, visualization monitoring system and data acquisition and control system;Focused ultrasonic transducer is accurately acted on microfluidic core model in cooperation with three-dimensional displacement platform, displacement system contains annular pressure automatic tracking module to simulate formation pressure, and high-speed camera realizes pore scale dynamic observation.The method comprises the following steps: establishing pollution model, applying controllable ultrasonic wave, in-situ visualizing collecting cavitation bubble and pollutant transport process, synchronously collecting seepage data and correlating and analyzing plugging removal mechanism.The present application can real-time observe the microcosmic dynamics process of ultrasonic plugging removal, quantify the relationship between frequency, power and plugging removal efficiency, and is suitable for mechanism research and parameter optimization of various near well pollution types, and solves the "black box" problem that traditional technology cannot in-situ visualize observation.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development and production enhancement technology, specifically to a laboratory method and apparatus for studying ultrasonic visualization to solve near-wellbore contamination. Background Technology

[0002] In oil and gas field development, the near-wellbore zone is the crucial passage connecting the wellbore to the original formation, and its permeability directly determines the production capacity of the oil and gas well. However, during drilling, completion, workover, and production enhancement operations, phenomena such as solid particle intrusion from foreign working fluids (e.g., drilling fluid, cement slurry, fracturing fluid), emulsification caused by incompatibility between the liquid phase and formation fluids, scaling, and clay mineral expansion and migration can all lead to a significant decrease in near-wellbore permeability, forming "near-well contamination" or the "skin effect." Accurate diagnosis, assessment, and effective removal of near-wellbore contamination are key to restoring and even enhancing oil and gas well productivity, and have long been a research focus and challenge in the field of petroleum engineering.

[0003] Most existing ultrasonic unblocking technologies focus on improving field application tools to enhance operational reliability and effectiveness. For example, patent CN104712292A (published in China on June 17, 2015) discloses an ultrasonic unblocking process and its associated device. This device uses a vehicle-mounted design, transmitting high-power electrical signals generated on the surface to a piezoelectric ceramic electroacoustic transducer installed downhole via cable, thereby radiating the oil layer. While this solution details the macroscopic process flow of ultrasonic unblocking and verifies its practical effectiveness in the field, its key technological aspects lie in the field construction methods and the integration of the complete equipment. However, it lacks a more detailed study of the microscopic mechanism of the interaction between ultrasonic waves and formation blockages. Patents like these and similar field technologies generally share a common flaw: the entire unblocking process is a "black box" from which the internal workings cannot be observed. Researchers can only indirectly evaluate the effects based on changes in macroscopic production data such as water pressure and injection volume before and after construction. However, key scientific questions such as how ultrasonic energy is transmitted in porous media, how cavitation removes pollutants, and the effectiveness of different parameters (such as frequency, power, and duration) in removing various blockages lack direct experimental observation methods and corresponding data to support them.

[0004] To improve the reliability of downhole tools and the efficiency of ultrasonic transmission, subsequent research focused on optimizing the transducer structure. Patent CN223203036U (published in China on August 8, 2025) is an ultrasonic unblocking and injection device that designs the inner bore of the protective tube and the piezoelectric ceramic tube into a conical structure. The axial displacement created by the threaded fastening ensures a tight fit between the two, effectively reducing energy loss during sound wave transmission. Another patent, CN223152028U (published in China on July 25, 2025), successfully solved the problem of obstruction when downhole tools are lowered into wellbores with deposits by installing a helical impeller at the lower end of the ultrasonic unblocking device. It also utilizes a capsule structure filled with silicone oil to protect the transducer, further improving the efficiency of sound wave transmission and reducing energy consumption.

[0005] However, the key improvements of the aforementioned patents (CN223203036U and CN223152028U) in existing technologies still focus on optimizing the structure of on-site construction tools and improving their reliability. These technologies share a common and persistent fundamental flaw: these devices are designed according to the actual needs of downhole operations and lack the capability for real-time, unobservable, and clearly visible research and observation of the unblocking process in a laboratory setting.

[0006] A fundamental flaw shared by existing technologies is their failure to enable real-time, in-situ, and visualized observation of the ultrasonic deblocking process. Researchers can only indirectly assess the effectiveness by comparing changes in permeability before and after treatment, remaining completely unaware of key dynamic processes such as how ultrasonic energy is transmitted in porous media, where cavitation occurs, and how blockage particles are detached and transported with the fluid. This lack of mechanistic research severely hinders the development of ultrasonic deblocking technology from an empirical "black box" operation to a precise, controllable, and predictable "transparent" process. Summary of the Invention

[0007] The purpose of this invention is to provide a laboratory method and apparatus for studying ultrasonic visualization to resolve near-wellbore contamination, thereby addressing the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a laboratory device for studying ultrasonic visualization to solve near-wellbore contamination, comprising an ultrasonic system, a displacement system, a visualization monitoring system, and a data acquisition and control system;

[0009] The ultrasonic system includes an ultrasonic generator, a transmission cable, and an ultrasonic transducer. The ultrasonic transducer is fixed to one side of the microfluidic core model and is used to apply controllable ultrasonic energy to the contaminated area of ​​the core.

[0010] The displacement system includes a horizontal flow pump, a microfluidic core model, and an oil-water metering system. The horizontal flow pump is connected to the inlet of the microfluidic core model via a pipeline, and the outlet of the microfluidic core model is connected to the oil-water metering system. This system is used to simulate the formation fluid seepage environment and to meter the produced fluid in real time.

[0011] The visualization monitoring system includes a high-speed camera, the probe of which is arranged around the microfluidic core model. The high-speed camera is connected to a data acquisition module and is used to collect in real time the transport of pollutants inside the core, the dynamics of cavitation bubbles, and the unblocking process at the pore scale.

[0012] The data acquisition and control system includes a data acquisition module and a terminal console, which are respectively connected to the ultrasonic system, the displacement system and the visualization monitoring system, for centralized control of experimental parameters and synchronous recording of multi-source data.

[0013] Furthermore, the ultrasonic transducer is a focusing transducer with a focal diameter of 10mm to 30mm, and is used in conjunction with a three-dimensional precision electrically controlled displacement platform to achieve precise positioning of the focal point within the core model.

[0014] Furthermore, the displacement system also includes an automatic ring pressure tracking module, which is used to simulate the formation pressure environment in real time and realize the dynamic coupling of the ultrasonic energy field and the formation fluid seepage field.

[0015] Furthermore, the microfluidic core model is a two-dimensional or three-dimensional glass microfluidic chip, which forms pore channels simulating porous media through photolithography or etching processes. Its pressure resistance is not less than 60 MPa and its temperature resistance is not less than 150°C.

[0016] Furthermore, the high-speed camera has a shooting frame rate of no less than 100 frames per second, which is used to achieve sub-micron resolution observation at the pore scale.

[0017] A laboratory method for studying ultrasonic visualization to resolve near-wellbore contamination, characterized by employing the aforementioned apparatus and comprising the following steps:

[0018] S1. Inject contaminants into the microfluidic core model through the advection pump of the displacement system to establish a near-wellbore contamination simulation model and measure the permeability after contamination.

[0019] S2. Start the ultrasonic generator and apply ultrasonic waves to the contaminated area of ​​the microfluidic core model through the ultrasonic transducer. Use cavitation effect, mechanical vibration and thermal effect to promote the removal of contaminants.

[0020] S3. The dynamic process of pollutant transport, cavitation bubble generation and collapse inside the microfluidic core model is collected in real time by a high-speed camera and transmitted synchronously to the terminal console via the data acquisition module. Pressure, differential pressure and permeability data are also recorded simultaneously.

[0021] S4. After the experiment, the core permeability recovery rate was measured, and the unblocking mechanism was analyzed by combining the collected images and data.

[0022] Furthermore, in step S2, the frequency of the ultrasound is adjusted from 18kHz to 50kHz, the power is continuously adjustable, the power density is from 0.5W / cm² to 2.0W / cm², the pulse mode is used, and the duration of a single treatment is from 20 minutes to 120 minutes.

[0023] Furthermore, in step S1, the contaminant is at least one of a solid particle suspension, an inorganic scale solution, an oil-water emulsion, or an organic scale solution.

[0024] Furthermore, in step S4, the acquired images are quantitatively analyzed through the terminal console to obtain the reduction ratio of pollutant coverage area and establish a quantitative relationship between ultrasonic parameters and unblocking efficiency.

[0025] Furthermore, when used to remove organic scale blockages, it is combined with programmed heating and cooling cycles to utilize the synergistic effect of the thermal and mechanical effects of ultrasound to achieve unblocking.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The core technology of this invention lies in combining integrated high-intensity focused ultrasonic technology with a dynamic coupling displacement system. The ultrasonic transducer features an adjustable frequency of 18–50 kHz and continuously adjustable power between 60–1000 W. Through meticulous design, energy is precisely focused within the contaminated area, effectively preventing energy dispersion. The displacement system also innovatively incorporates an automatic annular pressure tracking module, which simulates the real formation pressure environment in real time, ensuring dynamic synergy between the ultrasonic energy field and the formation fluid seepage field. This device achieves groundbreaking transparency in observing the entire ultrasonic unblocking process. It can capture the migration trajectory of contaminants, the dynamic behavior of cavitation bubbles, and the propagation process of microcracks in situ. Furthermore, by correlating and analyzing synchronously acquired high-speed photographic images and core permeability data, it clearly and experimentally demonstrates for the first time the dominant mechanisms of cavitation, mechanical vibration, and thermal effects in the unblocking process, as well as the conditions for their interconversion. The system also has a dynamic data feedback function, which can optimize and adjust key parameters such as ultrasonic power, frequency and action time based on the results obtained from real-time observation, thereby greatly improving the efficiency and targeting of the unblocking effect. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a laboratory device for studying ultrasonic visualization to solve near-wellbore contamination according to the present invention;

[0029] Figure 2 This is a schematic diagram of the experimental process flow of the present invention;

[0030] Figure 3 This is a schematic diagram of the ultrasonic transducer structure of the present invention.

[0031] In the figure: 11. Ultrasonic transducer; 12. Ultrasonic generator; 21. Advection pump; 22. Microfluidic core model; 23. Oil-water metering system; 31. High-speed camera; 41. Data acquisition module; 42. Terminal control console. Detailed Implementation

[0032] Please see Figure 1 —3, a laboratory apparatus for studying ultrasonic visualization to resolve near-wellbore contamination, comprising an ultrasonic system, a displacement system, a visualization monitoring system, and a data acquisition and control system;

[0033] The ultrasonic system includes an ultrasonic generator 12, a transmission cable, and an ultrasonic transducer 11. The ultrasonic transducer 11 is fixed to one side of the microfluidic core model 22 and is used to apply controllable ultrasonic energy to the contaminated area of ​​the core. The displacement system includes a horizontal flow pump 21, a microfluidic core model 22, and an oil-water metering system 23. The horizontal flow pump 21 is connected to the inlet of the microfluidic core model 22 via a pipeline, and the outlet of the microfluidic core model 22 is connected to the oil-water metering system 23 to simulate the formation fluid seepage environment and measure the produced fluid in real time. The visualization monitoring system includes a high-speed camera 31. The probe of the high-speed camera 31 is arranged around the microfluidic core model 22. The high-speed camera 31 is connected to the data acquisition module 41 and is used to collect in real time the transport of contaminants inside the core, the dynamics of cavitation bubbles, and the unblocking process at the pore scale. The data acquisition and control system includes a data acquisition module 41 and a terminal console 42, which are connected to the ultrasonic system, the displacement system, and the visualization monitoring system, respectively, to realize centralized control of experimental parameters and synchronous recording of multi-source data.

[0034] The ultrasonic transducer 11 is a focusing transducer with a focal diameter of 10mm to 30mm, and it is used in conjunction with a three-dimensional precision electrically controlled displacement platform to achieve precise positioning of the focal point within the core model. The displacement system also includes an annular pressure automatic tracking module, which is used to simulate the formation pressure environment in real time and realize the dynamic coupling of the ultrasonic energy field and the formation fluid seepage field. The microfluidic core model 22 is a solid core carrier that can be fitted with a high-temperature and high-pressure transparent clamp for clamping. Its pressure bearing capacity is not less than 60MPa and its temperature resistance is not less than 150℃. The high-speed camera 31 has a shooting frame rate of not less than 100 frames / second, which is used to achieve high-resolution observation at the pore scale.

[0035] Figure 3 As shown, the core internal component of the ultrasonic transducer 11 is a piezoelectric ceramic vibrator. The piezoelectric ceramic vibrator is made of piezoelectric ceramic tubing and, based on the inverse piezoelectric effect, converts the high-frequency electrical signal output from the ultrasonic generator into longitudinal mechanical vibration of the same frequency, serving as the excitation source for the ultrasonic wave. An acoustic matching layer is applied to the radiating end face of the piezoelectric ceramic vibrator to match the acoustic impedance between the transducer and the external coupling medium, reducing sound wave reflection loss at the interface. A concave spherical focusing acoustic lens is provided at the radiating end of the transducer, which can converge the radiated ultrasonic beam into a focusing area with a diameter of 10mm to 30mm. The transducer shell adopts a metal-sealed structure, and the inner cavity of the shell is filled with insulating and thermally conductive silicone oil, which provides insulation and heat dissipation for the piezoelectric ceramic vibrator and ensures stable transmission of sound waves within the transducer.

[0036] A laboratory method for studying ultrasonic visualization to resolve near-wellbore contamination, based on the aforementioned device, includes the following core steps:

[0037] S1. Pollutants are injected into the microfluidic core model 22 through the advection pump 21 of the displacement system to establish a near-wellbore pollution simulation model and measure the permeability after pollution.

[0038] S2. Start the ultrasonic generator 12 and apply ultrasonic waves to the contaminated area of ​​the microfluidic core model 22 through the ultrasonic transducer 11 to promote the removal of contaminants by utilizing cavitation effect, mechanical vibration and thermal effect.

[0039] S3. The dynamic process of pollutant transport, cavitation bubble generation and collapse inside the microfluidic core model 22 is collected in real time by the high-speed camera 31 and transmitted synchronously to the terminal console 42 via the data acquisition module 41, and pressure, pressure difference and permeability data are recorded synchronously.

[0040] S4. After the experiment, the core permeability recovery rate was measured, and the unblocking mechanism was analyzed by combining the collected images and data.

[0041] In step S2, the frequency of the ultrasound is adjusted from 18kHz to 50kHz, the power is continuously adjustable, the power density is from 0.5W / cm² to 2.0W / cm², and it operates in pulse mode with a single treatment time of 20 minutes to 120 minutes. In step S1, the contaminant is at least one of solid particle suspension, inorganic scale solution, oil-water emulsion, or organic scale solution. In step S4, the acquired images are quantitatively analyzed through the terminal control console 42 to obtain the proportion of reduction in contaminant coverage area and establish a quantitative relationship between ultrasonic parameters and unblocking efficiency. When used to remove organic scale blockage, it is combined with programmed heating and cooling cycles to achieve unblocking by utilizing the synergistic effect of the thermal and mechanical effects of ultrasound.

[0042] Example 1: A simplified device for studying specific mechanisms

[0043] This embodiment is applicable to the microscopic mechanism study of single effects of focused ultrasound (such as pure cavitation effect or pure mechanical vibration effect). It replaces and optimizes the core model, focuses on improving the observation resolution, and adapts to mechanism exploration experiments with single variables.

[0044] In this embodiment, the core experimental carrier is replaced in a targeted manner, as follows:

[0045] Core Model Replacement: The physical core (i.e., microfluidic core model 22) is replaced with a two-dimensional / three-dimensional glass microfluidic chip. This chip, through photolithography and etching techniques, fabricates a microchannel network on a glass substrate that can simulate the pore structure of porous media. This structure has a regular pore structure and excellent light transmittance, allowing for observation with higher magnification objectives, improving the observation resolution to the sub-micron level. It can accurately observe the complete process of cavitation bubble generation and collapse at the pore throat, measure the critical conditions for deformation and rupture of a single emulsion droplet under ultrasonic action, and further explore the flow field distribution of acoustic flow in micron-level channels.

[0046] The ultrasonic transducer 11 is fixed to one side of the aforementioned two-dimensional / three-dimensional glass microfluidic chip. The horizontal flow pump 21 is connected to the inlet of the glass microfluidic chip via a pipeline, and the chip outlet is connected to the oil-water metering system 23. The probe of the high-speed camera 31 is arranged around the glass microfluidic chip to ensure that the connection relationship of the experimental system is consistent with the basic device.

[0047] Meanwhile, in this embodiment, the ultrasonic transducer can be replaced with a suitable structural form according to the research purpose, specifically including two optional solutions:

[0048] Planar transducers replace focusing transducers, producing sound field uniformity that is suitable for exploring the uniform effect of ultrasound on a large area and is well-suited for evaluating overall unblocking effects.

[0049] By arranging two or more transducers on opposite sides or in multiple directions of a glass microfluidic chip, and by precisely controlling the phase and power of each transducer, complex sound field distributions or standing wave fields can be constructed to explore the aggregation behavior of particles in the sound field and adapt to the study of unblocking mechanisms in complex sound field environments.

[0050] The remaining system components and connections in this embodiment are consistent with the basic device, enabling visualization studies of the ultrasonic unblocking micromechanism under single-variable control, and eliminating interference from irrelevant variables on the experimental results.

[0051] Example 2: Integrated Ultrasonic Visualization and Unblocking Analysis System

[0052] This embodiment is a fully functional integrated experimental system, suitable for comprehensive research on the entire process of near-wellbore contamination unblocking mechanism, effect evaluation, and parameter optimization. It can completely reproduce the seepage environment and ultrasonic unblocking process in the near-wellbore zone, and realize full-process visual observation and multi-parameter coordinated control.

[0053] The core of this system includes a displacement and simulation module, an ultrasonic wave generation and action module, a real-time observation and recording module, and a central control and data processing module. These modules communicate and coordinate through physical interfaces and data cables, as detailed below:

[0054] Displacement and Simulation Module: The core is a high-temperature and high-pressure transparent glass etched microfluidic core model 22, which has a pressure bearing capacity of not less than 60MPa and a temperature resistance of not less than 150℃; the two ends of the model are connected to high-precision advection pumps 21 to simulate the formation injection fluid and formation pressure environment; the module has a built-in ring pressure automatic tracking module, which can simulate the confining pressure environment of the real formation in real time and realize the dynamic coupling of ultrasonic energy field and formation fluid seepage field.

[0055] Ultrasonic generation and interaction module: The core is a multi-degree-of-freedom adjustable focusing ultrasonic transducer system, including an ultrasonic generator 12, a transmission cable, a focusing ultrasonic transducer 11, a three-dimensional precision electrically controlled displacement platform, and an impedance matching and coupling device. Among them, the focal diameter of the focusing ultrasonic transducer 11 is 10mm to 30mm, and the appropriate specifications can be changed according to experimental requirements. The movement accuracy of the three-dimensional precision electrically controlled displacement platform can reach ±0.01mm, which can accurately position the ultrasonic focal point to any contaminated area of ​​the microfluidic core model 22. The impedance matching and coupling device reduces energy loss during sound wave transmission through an acoustic coupling agent circulation system.

[0056] Real-time observation and recording module: The core is a high-speed microscopic camera system (high-speed camera 31), with a shooting frame rate of no less than 100 frames / second, which can be increased to a higher frame rate according to experimental needs. The high-speed camera 31 is installed on a two-dimensional electrically controlled translation stage, which can continuously scan and capture images of the entire plane of the microfluidic core model 22 or a designated contaminated area, and collect images of the entire unblocking process at the pore scale in real time.

[0057] Central control and data processing module: This module serves as the system's scheduling and information processing hub. The hardware consists of a high-performance industrial computer (terminal console 42), equipped with a dedicated control program and data acquisition module 41. The software interface can centrally manage the operating parameters of the advection pump 21, ultrasonic generator 12, three-dimensional electrically controlled displacement platform, and high-speed camera 31, providing a unified process control entry point. During the experiment, sensor data and video sequences can be collected and recorded simultaneously. It has image processing capabilities and can perform data processing tasks such as flow field analysis and quantification of pollutant degradation processes.

[0058] Work process and operating steps

[0059] This embodiment takes the removal of solid particle blockage as an example to explain the experimental operation steps in detail, as follows:

[0060] Core model preparation and contamination model establishment: Select thin sections of core castings from the target formation, extract pore structure vector diagrams, and prepare glass microfluidic core models 22 using photolithography or acid etching processes; inject simulated formation water into the model using a horizontal flow pump 21, and measure the initial permeability Ki of the core; then inject a solid particle suspension into the model to simulate near-wellbore contamination until the displacement pressure differential stabilizes, and record the permeability Kd of the contaminated core.

[0061] Visualized unblocking experiment: In the control software of the terminal console 42, the experimental sequence is set, and the ultrasonic parameters are set to frequency 40kHz, power density 1.2W / cm², and pulse working mode; at the same time, the high-speed camera 31 is started, the shooting frame rate is set to 400fps, and it is aimed at the middle contaminated area of ​​the core model; under the condition of maintaining low-speed formation water displacement, the ultrasonic system and the three-dimensional electrically controlled displacement platform are started simultaneously. The system runs automatically and records all-dimensional experimental data such as displacement pressure difference, fluid flow rate, ultrasonic power, platform position, and video recording.

[0062] Data post-processing and mechanism analysis: After the experiment, the collected pressure and flow data were converted into instantaneous permeability K(t), and permeability recovery curves were plotted. Analysis of the high-speed video sequence clearly showed that within the ultrasonic scanning area, solid particles first vibrated, and then, under the synergistic effect of cavitation microjets and acoustic flow, detached from the pore walls and migrated with the fluid. Image analysis was used to quantify the reduction rate of pollutant coverage area. The permeability change pattern was correlated with the unblocking phenomenon observed in the video on the time axis to clarify the causal relationship between the two. For example, 3 seconds after the ultrasonic scan was completed, the permeability in the corresponding area showed a significant increase, and the synchronous video clearly showed that the blocking particles in that area had been effectively removed.

[0063] Example 3: Application examples for different near-wellbore contamination types

[0064] The apparatus and method of the present invention have wide applicability. By adjusting the experimental medium, ultrasonic parameters and experimental procedures, they can be adapted to the unblocking research of different types of pollution in the near-wellbore area of ​​oil and gas fields. The following provides specific implementation methods for typical pollution types.

[0065] Application Scenario 1: Relieving Emulsion Blockage

[0066] Experimental procedure: Oil-water emulsion was injected into the microfluidic core model 22 using a horizontal flow pump 21 to establish a stable emulsion lock-blocking model; high-frequency ultrasound was selected to enhance the acoustic flow and mechanical vibration effects by utilizing its short wavelength, which caused the emulsion droplets to collide, merge and break up.

[0067] Experimental results: Through high-speed camera 31, it can be observed in real time that the originally stable fine emulsion droplets oscillate violently under the action of ultrasound, move closer to each other and aggregate, and eventually merge to form large-diameter droplets, effectively reducing the flow resistance in the pores; after the experiment, quantitative detection showed that the relative permeability of the oil phase and water phase in the core was significantly restored.

[0068] Application Scenario 2: Removing organic scale (asphaltite, wax) deposits and blockages

[0069] Experimental procedure: A microfluidic core model 22 with organic scale deposition was constructed. While applying ultrasound, the entire experimental system was subjected to programmed heating and cooling cycles through a constant temperature chamber. The ultrasound parameters were adapted to the low-frequency band to enhance the synergistic effect of mechanical vibration and thermal effect.

[0070] Experimental Results: As observed through the visualization system, the mechanical vibration of ultrasound can effectively disrupt the adhesion between organic scale deposits and pore walls. At the same time, the thermal effect can accelerate heat conduction, promoting the softening and peeling of organic deposits. Compared with the simple hot washing method, this method can significantly reduce the processing temperature and time. For example, simple hot washing requires heating the core to 80°C and continuing for 2 hours to remove the blockage. However, after combining with ultrasonic treatment, it is only necessary to heat to 60°C and process for 30 minutes to achieve the same or even better permeability recovery effect, greatly reducing experimental energy consumption and shortening the process time.

[0071] Application Scenario 3: Removing inorganic scale / solid particles from the blockage

[0072] Experimental procedure: Inorganic scale solution or solid particle suspension was injected into the microfluidic core model 22 through the horizontal flow pump 21 to establish a stable blockage model; the ultrasonic frequency was set to be adjustable from 18kHz to 50kHz and the power density was set to be 0.5W / cm² to 2.0W / cm². Focused ultrasound was used to precisely act on the contaminated area for 20 minutes to 120 minutes, and the visualization monitoring system was turned on simultaneously.

[0073] Experimental Results: The high-speed camera 31 can clearly capture the peeling and transport paths of inorganic scale crystals and solid particles. The cavitation effect and mechanical vibration work together to achieve efficient unblocking. After the experiment, the core permeability recovery rate was significantly improved, and the energy consumption for unblocking a unit volume of core was reduced to 0.8 kWh / L, which is 47% more energy-efficient than traditional experimental methods. The cycle of a single experiment can be controlled within 4 hours, and the experimental efficiency is improved by 50%.

Claims

1. A laboratory apparatus for studying ultrasonic visualization in addressing near-wellbore contamination, characterized in that, This includes ultrasonic systems, displacement systems, visual monitoring systems, and data acquisition and control systems; The ultrasonic system includes an ultrasonic generator (12), a transmission cable and an ultrasonic transducer (11), the ultrasonic transducer (11) being fixed to one side of the microfluidic core model (22). The displacement system includes a horizontal pump (21), a microfluidic core model (22), and an oil-water metering system (23). The horizontal pump (21) is connected to the inlet of the microfluidic core model (22) via a pipeline, and the outlet of the microfluidic core model (22) is connected to the oil-water metering system (23). The visualization monitoring system includes a high-speed camera (31), the probe of which is arranged around the microfluidic core model (22), and the high-speed camera (31) is connected to the data acquisition module (41); The data acquisition and control system includes a data acquisition module (41) and a terminal console (42), which are respectively connected to the ultrasonic system, the displacement system and the visualization monitoring system.

2. The laboratory apparatus for studying ultrasonic visualization in addressing near-wellbore contamination according to claim 1, characterized in that, The ultrasonic transducer (11) is a focusing transducer with a focal diameter of 10mm to 30mm, and is used in conjunction with a three-dimensional precision electronically controlled displacement platform to achieve precise positioning of the focal point within the core model.

3. The laboratory apparatus for studying ultrasonic visualization in addressing near-wellbore contamination according to claim 1, characterized in that, The displacement system also includes an automatic ring pressure tracking module, which is used to simulate the formation pressure environment in real time and realize the dynamic coupling of the ultrasonic energy field and the formation fluid seepage field.

4. The laboratory apparatus for studying ultrasonic visualization in addressing near-wellbore contamination according to claim 1, characterized in that, The microfluidic core model (22) is a two-dimensional or three-dimensional glass microfluidic chip, which forms a pore channel simulating a porous medium through photolithography or etching process. Its pressure resistance is not less than 60MPa and its temperature resistance is not less than 150℃.

5. The laboratory apparatus for studying ultrasonic visualization in addressing near-wellbore contamination according to claim 1, characterized in that, The high-speed camera (31) has a shooting frame rate of no less than 100 frames / second, which is used to achieve submicron resolution observation at the pore scale.

6. A laboratory method for studying ultrasonic visualization to address near-wellbore contamination, characterized in that, The apparatus of claim 1 comprises the following steps: S1. Pollutants are injected into the microfluidic core model (22) through the advection pump (21) of the displacement system to establish a near-well pollution simulation model and measure the permeability after pollution. S2. Start the ultrasonic generator (12) and apply ultrasonic waves to the contaminated area of ​​the microfluidic core model (22) through the ultrasonic transducer (11) to promote the removal of pollutants by using cavitation effect, mechanical vibration and thermal effect. S3. The dynamic process of pollutant transport, cavitation bubble generation and collapse inside the microfluidic core model (22) is collected in real time by a high-speed camera (31), and transmitted synchronously to the terminal console (42) via the data acquisition module (41), and pressure, pressure difference and permeability data are recorded synchronously. S4. After the experiment, the core permeability recovery rate was measured, and the unblocking mechanism was analyzed by combining the collected images and data.

7. The laboratory method for studying ultrasonic visualization to resolve near-wellbore contamination according to claim 6, characterized in that, In step S2, the frequency of the ultrasound is adjusted from 18kHz to 50kHz, the power is continuously adjustable, the power density is from 0.5W / cm² to 2.0W / cm², the pulse mode is used, and the duration of a single treatment is from 20 minutes to 120 minutes.

8. The laboratory method for studying ultrasonic visualization to resolve near-wellbore contamination according to claim 6, characterized in that, In step S1, the contaminant is at least one of solid particulate suspension, inorganic scale solution, oil-water emulsion or organic scale solution.

9. The laboratory method for studying ultrasonic visualization to resolve near-wellbore contamination according to claim 6, characterized in that, In step S4, the acquired images are quantitatively analyzed through the terminal console (42) to obtain the proportion of pollutant coverage reduction and to establish a quantitative relationship between ultrasonic parameters and unblocking efficiency.

10. The laboratory method for studying ultrasonic visualization to resolve near-wellbore contamination according to claim 6, characterized in that, When used to remove organic scale blockages, it is combined with programmed heating and cooling cycles, utilizing the synergistic effect of the thermal and mechanical effects of ultrasound to achieve unblocking.

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