Testing device and method for gas-liquid competitive adsorption under simulated reservoir electric field environment

Abstract

The application provides a kind of test device and method of gas-liquid competitive adsorption under the simulation reservoir electric field environment, it is related to oil and gas field development experimental simulation technical field, the device includes QCM-D host computer, special electric field flow cavity, high voltage power supply, fluid injection system and signal isolation and shielding system;The method comprises: establishing baseline, monitoring crude oil adsorption kinetics, under the application of high voltage electric field, monitoring displacement gas competitive desorption kinetics, and generating evaluation results based on frequency and dissipation dual parameter changes.The application realizes real-time, in-situ, quantitative monitoring of gas-liquid competitive adsorption microprocess on the surface of QCM-D chip under the environment of kilovolt high voltage electric field for the first time through vertical transmission type non-contact electric field loading cavity and high voltage-weak signal isolation circuit, and can distinguish the different effects of electric field on mass desorption and interface rheological change, providing a reliable experimental tool and analysis method for revealing the micro mechanism of electric field enhanced oil displacement.

Description

Technical Field

[0001] This invention relates to the field of experimental simulation technology for oil and gas field development, and in particular to a test device and method for simulating gas-liquid competitive adsorption under a reservoir electric field environment. Background Technology

[0002] As oil and gas field development extends into unconventional, low-permeability reservoirs, the importance of enhanced oil recovery (EOR) technologies is becoming increasingly prominent. Electric field enhanced flooding (EDF), as a potentially highly efficient development method, relies on a high-voltage electric field to alter the microscopic forces between the reservoir rock surface and crude oil and displacing gases (such as CO2), thereby promoting crude oil desorption and migration. To optimize this technology, it is essential to clarify the dynamic influence of the electric field on the competitive adsorption behavior of the rock, crude oil, and gas three-phase interface at the microscopic scale.

[0003] Dissipative quartz crystal microbalances (QCM-D) are instruments capable of real-time, high-sensitivity measurement of nanoscale mass and viscoelastic changes on surfaces, and have been applied to fundamental adsorption research. However, existing standard QCM-D technologies and equipment cannot meet the requirements for simulating and monitoring competitive adsorption processes under high-pressure electric fields in reservoirs. The fundamental reason is that commercially available QCM-D modules lack the ability to apply high-pressure electric fields, while traditional electrochemical QCMs (E-QCMs) are only suitable for weak voltages in the millivolt to volt range, unable to provide the kilovolt (kV / cm) high-pressure electric fields required to simulate real reservoirs. More importantly, if high voltage is forcibly introduced, the resulting strong electromagnetic interference will completely overwhelm the weak nanoampere piezoelectric signals upon which the QCM-D relies for operation, causing the system to malfunction or be damaged. Therefore, existing technologies cannot achieve in-situ, real-time microdynamic monitoring and quantitative analysis of gas-liquid competitive displacement processes while applying reservoir-level high-pressure electric fields, hindering in-depth research and technological optimization of the micro-mechanism of electric field-driven oil recovery. Summary of the Invention

[0004] To address the technical problem of real-time in-situ monitoring of microscopic competitive adsorption processes under high-voltage electric field conditions, as described in the background, this invention provides a testing device and method for gas-liquid competitive adsorption under simulated reservoir electric field conditions. By integrating a specially designed electric field flow cavity with a parallel mesh electrode structure and a high-voltage-weak signal isolation and shielding system, it achieves non-destructive acquisition and analysis of frequency (Δf) and dissipation (ΔD) signals with millisecond-level precision for the adsorption / desorption process on the surface of the QCM-D chip while safely loading a kilovolt-level high-voltage electric field.

[0005] The first aspect of the present invention provides a test device for simulating gas-liquid competitive adsorption under a reservoir electric field environment, comprising: a QCM-D host for generating and receiving high-frequency electrical signals;

[0006] A specially designed electric field flow cavity, the cavity being made of insulating and voltage-resistant material, and having the following internal features:

[0007] The upper electrode is a mesh electrode embedded in the top of the cavity flow channel;

[0008] The lower electrode is a conductive coating disposed on the surface of the QCM-D chip at the bottom of the cavity;

[0009] The upper electrode and the lower electrode are arranged in parallel and opposite directions to form a uniform electric field in the microchannel between them.

[0010] A high-voltage power generator, electrically connected to the upper electrode, is used to provide a controllable electric field with a strength in the kV / cm range;

[0011] A fluid injection system is used to inject crude oil, displacement gas and background fluid into the specially designed electric field flow cavity;

[0012] A signal isolation and shielding system is connected between the QCM-D host and the QCM-D chip.

[0013] Furthermore, the signal isolation and shielding system includes:

[0014] A DC blocking capacitor, connected in series in the signal transmission path, is used to block high DC voltage.

[0015] Radio frequency transformers are used to couple and transmit high-frequency AC signals under electrically isolated conditions.

[0016] A Faraday shielding cage is wrapped around the outside of the specially designed electric field flow cavity to shield against electromagnetic interference.

[0017] Furthermore, the mesh electrode is a platinum mesh or a titanium mesh; the insulating and voltage-resistant material is polyetheretherketone (PEEK) or polytetrafluoroethylene (PTFE).

[0018] Furthermore, the fluid injection system includes at least two independently controllable fluid lines and switching valves, one for injecting crude oil or simulated oil and the other for injecting displacement gas.

[0019] Furthermore, the device also includes a temperature control system for maintaining the specially designed electric field flow cavity at a set reservoir simulation temperature.

[0020] A second aspect of the present invention provides a test method for gas-liquid competitive adsorption under a simulated reservoir electric field environment based on the device described in the first aspect, comprising:

[0021] Acquire the baseline frequency signal and baseline dissipation signal of the QCM-D chip;

[0022] Acquire the real-time frequency change signal and real-time dissipation change signal of the QCM-D chip during the process of injecting crude oil into the device;

[0023] Based on the real-time frequency change signal and the real-time dissipation change signal, the saturated adsorption amount and adsorption rate constant of crude oil on the chip surface are obtained.

[0024] The competitive desorption frequency signal and competitive desorption dissipation signal of the QCM-D chip are acquired during the process of switching the injection of displacement gas into the device and simultaneously applying a preset intensity electric field through the high voltage power generator of the device.

[0025] Based on the competitive desorption frequency signal and the competitive desorption dissipation signal, the desorption rate constant of the displacing gas on crude oil and the oil film viscoelastic evolution information are obtained under electric field assistance.

[0026] Based on the saturated adsorption capacity, adsorption rate constant, desorption rate constant, and viscoelastic evolution information, evaluation results are generated to assess the enhancement effect of the electric field on the gas-liquid competitive adsorption process.

[0027] Furthermore, the process of obtaining the saturated adsorption amount and adsorption rate constant of crude oil on the chip surface based on the real-time frequency change signal and the real-time dissipation change signal includes:

[0028] When the real-time frequency change signal enters the plateau period, the real-time frequency change signal and the real-time dissipation change signal are calculated based on the Sauerbrey equation or the Voigt model to obtain the saturated adsorption amount.

[0029] The adsorption rate constant is obtained by fitting the dynamic decrease process of the real-time frequency change signal.

[0030] Furthermore, the acquisition of the competitive desorption frequency signal and competitive desorption dissipation signal of the QCM-D chip during the process of switching the injection of displacing gas into the device and simultaneously applying a preset intensity electric field through the high-voltage power generator of the device specifically includes:

[0031] After the crude oil adsorption reaches saturation, the injected fluid is switched to supercritical CO2 through the fluid injection system of the device;

[0032] While switching fluids or after a predetermined time, the high-voltage power generator is controlled to apply a DC or pulsed electric field to the specially designed electric field flow cavity, and the competitive desorption frequency signal and competitive desorption dissipation signal are collected simultaneously.

[0033] Furthermore, the applied electric field is a pulsed electric field with a frequency range of 10Hz to 1000Hz and a duty cycle of 20% to 80%.

[0034] Furthermore, the process of obtaining the desorption rate constant and oil film viscoelastic evolution information of the displacing gas on crude oil under electric field assistance, based on the competing desorption frequency signal and the competing desorption dissipation signal, includes:

[0035] The dynamic recovery process of the competing desorption frequency signal is fitted to obtain the desorption rate constant;

[0036] Based on the changing trend and amplitude of the competitive desorption dissipation signal, the viscoelastic evolution information of the oil film is obtained through analysis;

[0037] The oil film viscoelastic evolution information is used to distinguish between the mass desorption effect caused by the electric field and the rheological change effect of crude oil.

[0038] Compared with the prior art, the test device and method for gas-liquid competitive adsorption under simulated reservoir electric field environment provided by the present invention have the following beneficial effects:

[0039] (1) The specially designed electric field flow cavity and high-voltage power generator provided by this invention realize the safe and uniform loading of a kV / cm-level high-voltage electric field within a microchannel. The cavity body is fabricated using an insulating and voltage-resistant material (such as PEEK), and the high-voltage mesh upper electrode and the QCM-D chip, which serves as the grounding lower electrode, are placed parallel to each other to form a vertical transmission-type non-contact electric field loading structure. This structure allows the high-voltage electric field to uniformly penetrate the fluid and act on the adsorption interface, while the electrode body does not directly contact the precision quartz crystal sensor, thereby physically decoupling the electric field loading from the mechanical vibration of the crystal oscillator. This fundamentally avoids the direct impact of high voltage on the core sensing element of the QCM and the mass load interference caused by contact.

[0040] (2) The signal isolation and shielding system provided by this invention solves the technical problem of extracting weak acoustic signals under strong electromagnetic interference environments. The series-connected DC blocking capacitors form a filter that allows high-frequency conduction and DC blocking, enabling lossless passage of MHz-level QCM excitation and response signals while completely isolating kV-level DC high voltage. The RF transformer provides further electrical isolation, and the external Faraday shielding cage effectively suppresses spatial electromagnetic radiation interference. This combined design ensures that weak piezoelectric signals at the nanoampere level can be clearly and stably acquired in a kilovolt high-voltage environment, achieving a signal-to-noise ratio that meets commercial instrument standards, thus eliminating the risk of QCM signals being submerged or instruments being burned out under high-voltage conditions.

[0041] (3) The fluid injection system, temperature control system, and step-by-step testing and dual-parameter analysis method provided by this invention enable in-situ quantitative analysis of the micro-dynamics of the entire gas-liquid competitive adsorption process under electric field assistance. High-precision fluid switching can simulate the transient processes of adsorption and displacement; the temperature control system ensures that the experimental conditions are consistent with the reservoir environment; methodologically, by real-time synchronous monitoring of frequency shift (Δf, reflecting mass change) and dissipation factor (ΔD, reflecting viscoelastic change), not only can the adsorption / desorption rate, saturated adsorption amount, and desorption rate constant under the electric field of crude oil be quantitatively calculated, but the change in ΔD can also be used to analyze whether the oil film hardens (structural damage) or softens (viscosity reduction) after the electric field action. This allows this invention to distinguish and quantify the two major micro-contributions of the electric field to enhanced oil recovery: promoting crude oil desorption and altering crude oil rheology. It provides direct and reliable experimental data and analytical methods for revealing the micro-mechanism of electric field-driven oil recovery and optimizing electric field parameters, filling a gap in the study of micro-mechanisms in this field. Attached Figure Description

[0042] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure. The spacing or dimensions between parts are exaggerated to show the position of each part, and the schematic diagrams are for illustrative purposes only.

[0043] Figure 1 This is a schematic diagram of the test device for gas-liquid competitive adsorption under a simulated reservoir electric field environment provided in Embodiment 1 of the present invention;

[0044] Figure 2 This is a circuit diagram of the signal isolation circuit provided in Embodiment 1 of the present invention;

[0045] Figure 3 This is the original data curve provided in Embodiment 2 of the present invention, showing that Δf increases significantly at the instant the electric field is turned on, while ΔD undergoes a specific change.

[0046] The components include: 1. Insulating cavity; 2. Upper electrode; 3. Lower electrode; 4. Microfluidic channel; 5. High voltage power supply; and 6. QCM-D main unit. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0048] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0049] It should be noted that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. The use of the words "upper," "lower," "left," and "right" in this invention only indicates alignment with the upper, lower, left, and right directions of the drawings themselves and does not limit the structure. They are merely for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0050] Terminology Explanation:

[0051] 1. QCM-D chip: A thin quartz crystal wafer with a conductive coating on its surface.

[0052] Example 1

[0053] This embodiment provides a test device for simulating gas-liquid competitive adsorption under a reservoir electric field environment, including:

[0054] The QCM-D host is used to generate and receive high-frequency electrical signals;

[0055] A specially designed electric field flow cavity, the cavity being made of insulating and voltage-resistant material, and having the following internal features:

[0056] The upper electrode is a mesh electrode embedded in the top of the cavity flow channel;

[0057] The lower electrode is a conductive coating disposed on the surface of the QCM-D chip at the bottom of the cavity;

[0058] The upper electrode and the lower electrode are arranged in parallel and opposite directions to form a uniform electric field in the microchannel between them.

[0059] A high-voltage power generator, electrically connected to the upper electrode, is used to provide a controllable electric field with a strength in the kV / cm range;

[0060] A fluid injection system is used to inject crude oil, displacement gas and background fluid into the specially designed electric field flow cavity;

[0061] A signal isolation and shielding system is connected between the QCM-D host and the QCM-D chip.

[0062] like Figure 1The device includes an insulating cavity 1, with a mesh electrode embedded at its top as an upper electrode 2, and a QCM-D chip mounted at the bottom of the cavity as a lower electrode 3, forming a microfluidic channel 4 between the two. The insulating cavity 1 is made of insulating and voltage-resistant material, the upper electrode 2 is a platinum mesh or titanium mesh, and the lower electrode 3 is a conductive coating on the surface of the chip. The two are parallel to each other to form a uniform electric field.

[0063] The high-voltage power supply 5 is electrically connected to the upper electrode 2 and is used to apply a controllable high-voltage electric field with a strength in the kV / cm range into the cavity. The QCM-D host 6 is connected to the lower electrode 3 through a signal isolation and shielding system and is used to generate a high-frequency excitation signal to drive the quartz crystal resonance and to receive the response signal returned from the chip for real-time analysis.

[0064] Figure 1 In the diagram, the blue line indicates the direction of fluid injection: the fluid enters the microfluidic channel 4 from the left, flows through the microchannel between the upper electrode 2 and the lower electrode 3, and finally flows out from the right, forming a stable flow field. The red line indicates the direction of the electric field: the high-voltage electric field output by the high-voltage power supply 5 points vertically downward from the upper electrode 2 to the lower electrode 3, forming a uniform electric field perpendicular to the adsorption interface, which acts on the adsorption layer on the chip surface.

[0065] Specifically, the mesh electrode is a platinum mesh or a titanium mesh; the insulating and voltage-resistant material is polyetheretherketone (PEEK) or polytetrafluoroethylene (PTFE).

[0066] The specially designed electric field flow cavity provided in this embodiment is made of polyetheretherketone (PEEK) CNC machined. This material has excellent insulation, mechanical strength, and chemical corrosion resistance, and can withstand kV-level voltages without breakdown. For the internal electrode arrangement, the upper electrode is a high-purity platinum or titanium mesh, precisely machined and embedded into the inner side of the flow channel top cover, ensuring the mesh surface is parallel to the bottom surface of the flow channel. The lower electrode is the gold film coating on the surface of a standard QCM-D chip, which is fixed to the bottom of the cavity and well grounded via a mounting bracket. This mesh upper electrode and the flat lower electrode constitute a miniature parallel-plate capacitor. When a high-voltage power supply is connected to the upper electrode, a uniform, strong electric field perpendicular to the adsorption interface is formed within the narrow flow channel space between them (height adjustable from 0.1-0.5 mm). The mesh electrode design allows fluids (crude oil, CO2) to pass freely with almost no interference to the flow field, while ensuring the vertical transmission of the electric field. This non-contact design allows a high-voltage electric field to be applied to the adsorption layer on the surface of the QCM-D chip without any direct electrical connection between the high-voltage conductor and the quartz crystal or its excitation circuit. This perfectly achieves the physical and electrical decoupling of electric field loading and piezoelectric crystal oscillation, solving the technical problem that high-voltage loading can damage or interfere with the QCM sensor.

[0067] Specifically, the signal isolation and shielding system includes:

[0068] A DC blocking capacitor, connected in series in the signal transmission path, is used to block high DC voltage.

[0069] Radio frequency transformers are used to couple and transmit high-frequency AC signals under electrically isolated conditions.

[0070] A Faraday shielding cage is wrapped around the outside of the specially designed electric field flow cavity to shield against electromagnetic interference.

[0071] like Figure 2 The signal isolation circuit comprises three parts: a low-voltage control and detection terminal, a signal isolation barrier, and a high-voltage experimental terminal. The circuit integrates core components such as an input capacitor Cin, a DC blocking capacitor C1, an RF transformer, a DC blocking capacitor Cblock, an isolation capacitor Ciso, a resonant inductor L1, RF inductors L2 / L3, a damping resistor R, a matching capacitor C2, a feed-through capacitor, and a high-voltage source injection terminal HV+. These components work together to achieve high-voltage isolation and lossless transmission of high-frequency signals. The specific structure and function are as follows:

[0072] QCM-D Main Unit (Low-voltage Control and Detection Terminal): This is the core control unit of the system, containing an RF source, detector, and low-voltage control circuit. The RF source generates a high-frequency AC signal (usually 5MHz or its odd harmonics) to drive the quartz crystal resonance. The detector receives and analyzes the high-frequency signal returned from the QCM-D chip. The low-voltage control circuit provides a stable low-voltage power supply to each module and completes data processing.

[0073] Signal isolation barrier (protection and bridging terminal): This is the core component for achieving high and low voltage isolation. Figure 2 The core components of the circuit are divided into the following parts:

[0074] The input capacitor Cin and the DC blocking capacitor C1 are connected in series to form a high-pass filter structure, which serves as the first barrier for signal input. It allows radio frequency signals to enter, blocks low-frequency interference, and only allows AC radio frequency signals to enter the radio frequency transformer to protect the radio frequency source.

[0075] Radio frequency transformers convert unbalanced input signals into balanced differential signals and perform circuit impedance matching to ensure signal transmission efficiency.

[0076] The DC blocking capacitor Cblock further blocks the DC component, preventing the charge at the high-voltage end from penetrating back into the RF transformer;

[0077] The isolation capacitor Ciso is a core protection component for high-voltage safety isolation. It utilizes the characteristic of "passing AC and blocking DC" to isolate external high voltage while transmitting high-frequency signals.

[0078] The resonant inductor L1 and the capacitor in the circuit form a resonant circuit, ensuring low-loss signal transmission at the QCM-D operating frequency.

[0079] RF inductors L2 and L3, together with nearby isolation capacitor Ciso, form an impedance matching network at the QCM-D resonant frequency, ensuring that the signal is loaded onto the sensor chip with maximum power.

[0080] The damping resistor R consumes excess resonant energy, smooths the frequency response curve, and assists in completing circuit impedance matching;

[0081] Matching capacitor C2 adjusts the complex impedance at the output terminal, enabling the RF signal to be efficiently loaded onto the final QCM-D electrode;

[0082] Transient protection circuits (such as TVS diodes) clamp unexpected high-voltage transients to protect the host, while the internal shielding ground layer is used to suppress electromagnetic interference within the circuit.

[0083] High-voltage experimental terminal: This terminal is located in a high-voltage environment and includes a QCM-D electrode, a high-voltage positive electrode (HV+), and a feed-through capacitor. The surface of the QCM-D electrode is modified with a kerogen-like layer, which serves as both a piezoelectric sensor and the working electrode for the high-voltage electric field. The connection point between the high-voltage positive electrode (HV+) and the floating ground provides high voltage to the experimental area and ensures electrical isolation from the host ground. The feed-through capacitor serves as the physical connection structure inside and outside the shielded box, filtering out high-frequency noise and also acting as a safe physical interface for high-voltage output.

[0084] The flow direction and working principle of the system signals, high voltage, and shielding are as follows:

[0085] (1) Bidirectional flow path for radio frequency signals

[0086] Excitation process: The high-frequency signal emitted by the QCM-D host RF excitation source is filtered by the input capacitor Cin and the DC blocking capacitor C1 and then enters the RF transformer. After being converted into a balanced signal, it is coupled to the high-voltage experimental terminal node through the isolation capacitor Ciso and the DC blocking capacitor Cblock. Finally, it is applied to the QCM-D electrode through the feedthrough capacitor to drive the crystal oscillation.

[0087] Detection process: The frequency and attenuation changes (impedance changes) of the QCM-D electrode due to gas-liquid adsorption are reversed along the original excitation path and analyzed by the signal demodulator; by utilizing the series and parallel resonance characteristics of inductors and capacitors at the specific operating frequency of QCM-D, high-fidelity bidirectional transmission of high-frequency signals is achieved.

[0088] (2) High voltage electrostatic unidirectional bias path

[0089] An external high-voltage source outputs a DC high voltage through the HV+ terminal, which is directly applied to the output node of the high-voltage experimental terminal via a damping resistor R. This keeps the QCM-D electrode at a high potential, generating a strong electric field in the test chamber required to simulate the reservoir environment, thereby affecting the competitive adsorption behavior of gas-liquid molecules. This high voltage is only effective from the feedthrough capacitor to the QCM-D chip segment and is not conducted to the signal isolation barrier or the low-pressure control and detection terminal.

[0090] (3) Safety shielding and DC blocking principle

[0091] The impedance of the isolation capacitor Ciso, the DC blocking capacitors C1 and Cblock, and the input capacitor Cin to DC current tends to infinity, completely blocking the high voltage HV+ at the high voltage test terminal on the right side of the shielded box, forming a DC barrier. At the same time, the entire cavity and the high voltage test terminal of the signal isolation circuit are wrapped in a grounded copper mesh Faraday shielding cage. The shielded box (GND) completely isolates the internal sensitive detection circuit from the complex external electromagnetic environment, ensuring that the tiny adsorption signal at the nanoampere level is not overwhelmed by high voltage noise, and ensuring the safety of the operator and the QCM-D host.

[0092] The 5MHz high-frequency excitation signal generated by the QCM-D host achieves lossless coupling through frequency domain filtering and impedance matching of the aforementioned signal isolation barrier. The high-voltage DC electric field is stably applied to the chip electrodes through the HV+ terminal via an EMC filter. During this process, the signal isolation barrier and the Faraday shielding cage work together to ensure that the high-voltage DC signal and noise are completely blocked outside the QCM-D host, thereby achieving safe and pure acquisition of weak piezoelectric signals in a strong electric field environment.

[0093] Specifically, the fluid injection system includes at least two independently controllable fluid lines and switching valves. One line is used to inject crude oil or simulated oil, and the other line is used to inject displacement gas. The fluid injection system consists of two high-precision plunger pumps, an intermediate container, and a two-position three-way solenoid valve, forming two independent flow paths that can pump simulated crude oil and supercritical CO2 respectively. The valves enable millisecond-level switching, simulating the transient process of oil phase being displaced by gas in the reservoir.

[0094] Specifically, the device also includes a temperature control system to maintain the specially designed electric field flow cavity at a set reservoir simulation temperature. The temperature control system employs a jacketed heating / cooling system, coupled with a high-precision PID temperature controller, to ensure precise and stable cavity temperature within a range from room temperature to 150°C, simulating reservoir temperature environments at different depths. These subsystems collectively provide a controllable and realistic physicochemical environment for microscopic dynamics research.

[0095] In one specific embodiment, the device further includes the following implementation details:

[0096] 1. Chip Preprocessing and System Assembly: Select an AT-cut quartz crystal chip with a fundamental frequency of 5MHz (or 10MHz). Coat its surface with a 50~200nm thick layer of kerogen-like material (such as amorphous carbon or specific organic extracts) using physical vapor deposition (PVD) or self-assembled monolayer technology. Mount the modified chip into a QCM-D fluidic cell with a transparent conductive window. Connect a high-voltage DC power supply, and lead out the chip surface as the working electrode. Place a metal plate on the opposite side of the fluidic cell as the counter electrode, maintaining a spacing of 1~5mm. Parameter Preset: Set the QCM-D sampling frequency and monitor the 1st, 3rd, 5th, 7th, 9th, 11th, and 13th order overload frequencies (Δf) and dissipation factors (ΔD).

[0097] 2. Fluid system configuration: Two independent fluid pipelines are connected to the crude oil / simulated oil and CO2 / displacement gas storage tanks respectively, and the injection sequence and timing are controlled by a high-precision switching valve.

[0098] 3. Temperature control system: The system adopts a PID temperature control module and a jacketed heating / cooling structure to maintain the chamber temperature at an adjustable range of 25~80°C, simulating reservoir temperature conditions.

[0099] Example 2

[0100] This embodiment provides a test method for gas-liquid competitive adsorption under a simulated reservoir electric field environment based on the device described in Embodiment 1, including:

[0101] Acquire the baseline frequency signal and baseline dissipation signal of the QCM-D chip;

[0102] Acquire the real-time frequency change signal and real-time dissipation change signal of the QCM-D chip during the process of injecting crude oil into the device;

[0103] Based on the real-time frequency change signal and the real-time dissipation change signal, the saturated adsorption amount and adsorption rate constant of crude oil on the chip surface are obtained.

[0104] The competitive desorption frequency signal and competitive desorption dissipation signal of the QCM-D chip are acquired during the process of switching the injection of displacement gas into the device and simultaneously applying a preset intensity electric field through the high voltage power generator of the device.

[0105] Based on the competitive desorption frequency signal and the competitive desorption dissipation signal, the desorption rate constant of the displacing gas on crude oil and the oil film viscoelastic evolution information are obtained under electric field assistance.

[0106] Based on the saturated adsorption capacity, adsorption rate constant, desorption rate constant, and viscoelastic evolution information, evaluation results are generated to assess the enhancement effect of the electric field on the gas-liquid competitive adsorption process.

[0107] The aforementioned testing method enables in-situ tracking of the complete kinetic process from adsorption to electric field-assisted desorption. By using both frequency and dissipation parameters, information on mass change and structural evolution can be obtained simultaneously. This provides direct, multi-dimensional experimental evidence for the study of electric field-assisted oil displacement mechanisms.

[0108] Specifically, the process of obtaining the saturated adsorption amount and adsorption rate constant of crude oil on the chip surface based on the real-time frequency change signal and the real-time dissipation change signal includes:

[0109] When the real-time frequency change signal enters the plateau period, the real-time frequency change signal and the real-time dissipation change signal are calculated based on the Sauerbrey equation or the Voigt model to obtain the saturated adsorption amount.

[0110] The adsorption rate constant is obtained by fitting the dynamic decrease process of the real-time frequency change signal.

[0111] Based on the standardized data processing methods described above, the quantification of the adsorption process becomes repeatable and has clear physical meaning, establishing a reliable benchmark for subsequent comparisons of the effects of the electric field.

[0112] Specifically, the acquisition of the competitive desorption frequency signal and competitive desorption dissipation signal of the QCM-D chip during the process of switching the injection of displacing gas into the device and simultaneously applying a preset intensity electric field through the high-voltage power generator of the device is as follows:

[0113] After the crude oil adsorption reaches saturation, the injected fluid is switched to supercritical CO2 through the fluid injection system of the device;

[0114] While switching fluids or after a predetermined time, the high-voltage power generator is controlled to apply a DC or pulsed electric field to the specially designed electric field flow cavity, and the competitive desorption frequency signal and competitive desorption dissipation signal are collected simultaneously.

[0115] Based on the above operational steps, the timing control and data synchronization of the electric field-assisted displacement process were achieved, ensuring the repeatability of experimental conditions and the reliability of data. This provides an experimental basis for studying the synergistic effect of electric field and gas.

[0116] Specifically, the applied electric field is a pulsed electric field with a frequency range of 10 Hz to 1000 Hz and a duty cycle of 20% to 80%. The pulsed electric field generates electrophoretic and dielectrophoretic forces through periodically changing directions. These forces exert an oscillatory effect on the adsorbed oil droplets. The oscillation helps overcome the adsorption energy barrier. At the same time, the pulsed electric field can reduce energy consumption and avoid electrode polarization.

[0117] Specifically, the process of obtaining the desorption rate constant and oil film viscoelastic evolution information of the displacing gas on crude oil under electric field assistance, based on the competing desorption frequency signal and the competing desorption dissipation signal, includes:

[0118] The dynamic recovery process of the competing desorption frequency signal is fitted to obtain the desorption rate constant;

[0119] Based on the changing trend and amplitude of the competitive desorption dissipation signal, the viscoelastic evolution information of the oil film is obtained through analysis;

[0120] The oil film viscoelastic evolution information is used to distinguish between the mass desorption effect caused by the electric field and the rheological change effect of crude oil.

[0121] In one specific embodiment, the specific implementation steps and parameters are as follows:

[0122] S1: Baseline Establishment and Environmental Balancing

[0123] A background solution (such as n-decane or high-purity nitrogen) is pumped into the fluid pool at a flow rate of 50–100 μL / min, maintaining the temperature at 25–80°C (simulating reservoir temperature) and the pressure at 0.1–20 MPa. The process is continued until the frequency fluctuation Δf < 0.2 Hz / h and the dissipation fluctuation ΔD < 0.1 × 10⁻⁶. -6 When / h, record the current state as the baseline zero point.

[0124] S2: Monitoring of crude oil saturated adsorption kinetics

[0125] Switch to a simulated crude oil solution (such as a component oil containing polar components) and maintain the same flow rate. Record the decrease in frequency Δf in real time. When the frequency plateaus, calculate the adsorption mass per unit area of ​​crude oil using the Sauerbrey equation (for rigid films) or the Voigt model (for viscoelastic oil films). The adsorption rate was fitted using the following formula:

[0126] ;

[0127] in, is the adsorption rate constant.

[0128] S3: CO2 competitive displacement experiment assisted by electric field

[0129] After crude oil adsorption saturation, the fluid is rapidly switched to supercritical CO2 or high-pressure CO2 gas. Simultaneously with (or after a specific time delay) the fluid switching, a high-voltage DC electric field or pulsed electric field (frequency 10–1000 Hz, duty cycle 20%–80%) is applied via a power source. The recovery rate of Δf and the changing trend of ΔD are monitored in situ to analyze the desorption kinetics and oil film structure evolution.

[0130] S4: Displacement Efficiency Evaluation and Model Fitting

[0131] Define electric field driving efficiency: .

[0132] Comparison of different field strengths The desorption rate constant at the following conditions A functional relationship between electric field strength and desorption efficiency was established to determine the critical electric field strength that causes significant desorption of crude oil.

[0133] The shear modulus and viscosity of the oil film were calculated using the QCM-D multi-order frequency characteristics, and the influence of the electric field on the rheology of the oil film was analyzed.

[0134] Verification Example:

[0135] refer to Figure 3 The experiment was divided into three stages:

[0136] 1. Static adsorption equilibrium phase (0-5 min): Simulated crude oil reaches adsorption equilibrium on the kerogen chip surface, with the frequency shift Δf stabilizing around -150 Hz and the dissipation factor ΔD maintained at 10 × 10⁻⁶. -6 This indicates the formation of a viscoelastic oil film with a thickness of approximately 2.6 μm.

[0137] 2. Conventional gas-driven phase (5-15 min): When supercritical CO2 is introduced, Δf only rises slowly to -140 Hz, indicating that the pure molecular competitive adsorption effect is limited.

[0138] 3. Electric field-enhanced phase displacement (starting from 15 min): A 150V high-voltage DC electric field is turned on, and Δf increases in a stepwise manner to around -50Hz, with the fitted desorption rate constant being 0.0684 min. - ¹, which is 8.05 times that of the pure gas-driven stage; at the same time, ΔD rapidly decreases to 2.5×10 -6 This indicates a morphological evolution of the oil film from overall connectivity to discrete detachment. This data demonstrates the high sensitivity and effectiveness of the device of this invention in monitoring the mechanism of electric field-assisted oil displacement.

[0139] The working principle of this invention is as follows:

[0140] This invention utilizes a specially designed electric field flow cavity in conjunction with a signal isolation and shielding system. This system enables in-situ monitoring of the microscopic competitive adsorption process under a high-voltage electric field environment. Its core working principle can be divided into the following three levels.

[0141] 1. Electric field loading level:

[0142] The specially designed electric field flow cavity employs a parallel plate structure. The upper electrode of this cavity is a mesh electrode, connected to a high-voltage power generator. The lower electrode is a conductive coating on the surface of the QCM-D chip, grounded. The upper and lower electrodes are arranged parallel to each other, forming a uniform high-voltage electric field within the microchannel between them. The mesh electrode allows fluid to flow freely, avoiding interference with the flow field. Simultaneously, the mesh electrode ensures that the electric field lines penetrate the fluid layer perpendicularly, directly acting on the adsorption film on the chip surface. This non-contact loading method physically decouples the high-voltage electric field from the mechanical vibration of the quartz crystal, avoiding both the damping effect of traditional contact electrodes on the crystal oscillator and the risk of high-voltage breakdown.

[0143] 2. Signal isolation level:

[0144] The QCM-D host generates a high-frequency excitation signal. This signal is transmitted to the QCM-D chip through a signal isolation and shielding system. The signal isolation and shielding system includes a DC blocking capacitor, an RF transformer, and a Faraday shielding cage. The DC blocking capacitor is connected in series in the signal transmission path. It presents low impedance to high-frequency signals, allowing the signal to pass through. It presents high impedance to DC high voltage, blocking the DC path. The RF transformer transmits the high-frequency signal through electromagnetic induction coupling. It achieves complete electrical isolation between the input and output terminals, further blocking DC. The Faraday shielding cage surrounds a specially designed electric field flow cavity. It confines the high-voltage electric field within the cavity to a local space. It prevents electromagnetic radiation from interfering with external detection circuits. These three components work together to completely isolate the high-voltage DC signal from the QCM-D host. The high-frequency piezoelectric signal is transmitted without loss. Therefore, this system achieves safe and stable acquisition of nanoampere-level weak signals in kilovolt-level high-voltage environments.

[0145] 3. Dual-parameter analysis level:

[0146] The QCM-D chip outputs two key parameters in real time. The first parameter is the frequency offset Δf, which mainly reflects the mass change of the adsorbed material on the chip surface. The second parameter is the dissipation factor ΔD, which mainly reflects the viscoelasticity of the adsorbed layer. During the crude oil adsorption stage, a decrease in Δf indicates an increase in mass, while an increase in ΔD indicates that the oil film is viscoelastic. During the electric field-assisted displacement stage, a rebound in Δf indicates a decrease in mass, i.e., crude oil desorption. Changes in ΔD reveal the structural evolution of the oil film, such as rupture, hardening, or softening. By establishing an adsorption kinetic model, the adsorption rate constant can be extracted. By establishing a desorption kinetic model, the desorption rate constant can be extracted. These constants enable a quantitative evaluation of the efficiency of electric field-assisted oil displacement. Combining the evolution characteristics of ΔD, the essential role of the electric field can be further distinguished. One role is to promote mass desorption. Another role is to change the rheological properties of crude oil. This reveals the role of the electric field at the microscopic mechanism level.

[0147] In summary, through the synergistic operation of the three levels mentioned above, this invention achieves for the first time real-time, in-situ, multi-parameter microscopic monitoring of the gas-liquid competitive adsorption process under a kilovolt-level high-voltage electric field. It provides a powerful experimental tool for the research of electric field-enhanced oil displacement technology.

[0148] In the description of this specification, the terms "connection", "installation", "fixing", "setting", etc. are interpreted broadly. For example, "connection" can be a fixed connection or an indirect connection through an intermediate component without affecting the relationship between components and the technical effect. It can also be an integral connection or a partial connection. In such cases, those skilled in the art can understand the specific meaning of the above terms in this invention or invention according to the specific circumstances.

[0149] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A test device for simulating gas-liquid competitive adsorption under a reservoir electric field environment, characterized in that, include: The QCM-D host is used to generate and receive high-frequency electrical signals; A specially designed electric field flow cavity, the cavity being made of insulating and voltage-resistant material, and having the following internal features: The upper electrode is a mesh electrode embedded in the top of the cavity flow channel; The lower electrode is a conductive coating disposed on the surface of the QCM-D chip at the bottom of the cavity; The upper electrode and the lower electrode are arranged in parallel and opposite directions to form a uniform electric field in the microchannel between them. A high-voltage power generator, electrically connected to the upper electrode, is used to provide a controllable electric field with a strength in the kV / cm range; A fluid injection system is used to inject crude oil, displacement gas and background fluid into the specially designed electric field flow cavity; A signal isolation and shielding system is connected between the QCM-D host and the QCM-D chip; The signal isolation and shielding system includes: A DC blocking capacitor, connected in series in the signal transmission path, is used to block high DC voltage. Radio frequency transformers are used to couple and transmit high-frequency AC signals under electrically isolated conditions. A Faraday shielding cage is wrapped around the outside of the specially designed electric field flow cavity to shield against electromagnetic interference.

2. The apparatus as claimed in claim 1, characterized in that, The mesh electrode is a platinum mesh or a titanium mesh; the insulating and pressure-resistant material is polyetheretherketone (PEEK) or polytetrafluoroethylene (PTFE).

3. The apparatus as described in claim 1, characterized in that, The fluid injection system includes at least two independently controllable fluid lines and switching valves, one for injecting crude oil or simulated oil and the other for injecting displacement gas.

4. The apparatus as claimed in claim 1, characterized in that, The device also includes a temperature control system for maintaining the specially designed electric field flow cavity at a set reservoir simulation temperature.

5. A test method for gas-liquid competitive adsorption under a simulated reservoir electric field environment based on the device described in any one of claims 1-4, characterized in that, The method includes: Acquire the baseline frequency signal and baseline dissipation signal of the QCM-D chip; Acquire the real-time frequency change signal and real-time dissipation change signal of the QCM-D chip during the process of injecting crude oil into the device; Based on the real-time frequency change signal and the real-time dissipation change signal, the saturated adsorption amount and adsorption rate constant of crude oil on the chip surface are obtained. The competitive desorption frequency signal and competitive desorption dissipation signal of the QCM-D chip are acquired during the process of switching the injection of displacement gas into the device and simultaneously applying a preset intensity electric field through the high voltage power generator of the device. Based on the competitive desorption frequency signal and the competitive desorption dissipation signal, the desorption rate constant of the displacing gas on crude oil and the oil film viscoelastic evolution information are obtained under electric field assistance. Based on the saturated adsorption capacity, adsorption rate constant, desorption rate constant, and viscoelastic evolution information, evaluation results are generated to assess the enhancement effect of the electric field on the gas-liquid competitive adsorption process.

6. The method according to claim 5, characterized in that, The process of obtaining the saturated adsorption amount and adsorption rate constant of crude oil on the chip surface based on the real-time frequency change signal and the real-time dissipation change signal includes: When the real-time frequency change signal enters the plateau period, the real-time frequency change signal and the real-time dissipation change signal are calculated based on the Sauerbrey equation or the Voigt model to obtain the saturated adsorption amount. The adsorption rate constant is obtained by fitting the dynamic decrease process of the real-time frequency change signal.

7. The method according to claim 5, characterized in that, The acquisition of the competitive desorption frequency signal and competitive desorption dissipation signal of the QCM-D chip during the process of switching the injection of displacing gas into the device and simultaneously applying a preset intensity electric field through the high-voltage power generator of the device is specifically as follows: After the crude oil adsorption reaches saturation, the injected fluid is switched to supercritical CO2 through the fluid injection system of the device; While switching fluids or after a predetermined time, the high-voltage power generator is controlled to apply a DC or pulsed electric field to the specially designed electric field flow cavity, and the competitive desorption frequency signal and competitive desorption dissipation signal are collected simultaneously.

8. The method according to claim 7, characterized in that, The applied electric field is a pulsed electric field with a frequency range of 10Hz to 1000Hz and a duty cycle of 20% to 80%.

9. The method according to claim 5, characterized in that, The process of processing the competitive desorption frequency signal and the competitive desorption dissipation signal to obtain the desorption rate constant of the displacing gas on crude oil and the viscoelastic evolution information of the oil film under electric field assistance includes: The dynamic recovery process of the competing desorption frequency signal is fitted to obtain the desorption rate constant; Based on the changing trend and amplitude of the competitive desorption dissipation signal, the viscoelastic evolution information of the oil film is obtained through analysis; The oil film viscoelastic evolution information is used to distinguish between the mass desorption effect caused by the electric field and the rheological change effect of crude oil.

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