Method, apparatus and electronic device for improving fluid flow in a porous medium using pulsatile flow

Abstract

This invention provides a method, apparatus, and electronic device for improving the fluidity of porous media using pulsating flow. The method includes: determining a critical threshold and a subcritical baseline; applying a steady-state displacement with a displacement intensity equal to the subcritical baseline, and superimposing a pulsating drive; using a solution framework to advance the interfacial motion of droplets under pulsating drive over time, adaptively controlling the time step during the advancement process, the time step being jointly limited by multiple physical constraints; determining the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window; obtaining the fluidity index corresponding to the pulsating drive based on the truncated axial net displacement; keeping the amplitude of the pulsating drive constant, changing the frequency of the pulsating drive to obtain a first curve of the fluidity index changing with frequency, and determining a cutoff frequency based on the first curve; changing the amplitude of the pulsating drive to obtain a second curve of the cutoff frequency changing with amplitude. This method is suitable for engineering parameter design and selection and is reproducible.

Description

Technical Field

[0001] This invention relates to the field of multiphase flow and micro-permeation technology of porous media, and in particular to a method, apparatus and electronic device for improving the fluid flow of porous media by pulsating flow. Background Technology

[0002] In oil and gas reservoir development and multiphase flow research in porous media, residual oil clumps or bound droplets are often trapped within the pore throat contraction structures formed between particles due to capillary forces. Engineering methods such as water injection, steam injection, or chemical solvent injection are commonly used to improve the recovery rate of residual oil. However, these methods often suffer from low efficiency, high energy consumption, or environmental problems. In recent years, some new methods have been proposed, such as periodically modulating bottomhole pressure or applying elastic waves to the formation. However, current schemes mostly focus on macroscopic responses, resulting in poor interpretability, lack of engineering reproducibility, and inability to significantly improve oil recovery rates. Summary of the Invention

[0003] This invention provides a method, apparatus, and electronic device for improving the fluidity of porous media by pulsating flow, which solves the technical problem that the prior art focuses on the macroscopic scale and lacks engineering reproducibility, and can improve oil recovery rate.

[0004] This invention provides a method for improving the fluid flowability of porous media using pulsating flow. The method includes: determining a critical threshold for an externally driven droplet to pass through a pore throat contraction structure, and determining a subcritical baseline based on the critical threshold; applying steady-state displacement with a displacement intensity equal to the subcritical baseline to the droplet in the pore throat contraction structure; superimposing pulsating drive on the steady-state displacement, controlling the displacement intensity of the pulse drive to change periodically with time, so that the displacement intensity within one pulsating cycle after the superimposed pulse drive remains unchanged at the subcritical baseline; invoking a pre-determined solution framework, using the solution framework to perform time-history progression of the droplet's interfacial motion under pulsating drive, and solving for the droplet's state information at different times; During the propulsion process, the time step is adaptively controlled based on the current state information, and the time step is jointly limited by multiple physical constraints. Based on the droplet's state information at different times, the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window is determined. Based on the truncated axial net displacement, the flowability index corresponding to the pulsation drive is obtained. The amplitude of the pulsation drive is kept constant, and the frequency of the pulsation drive is changed to obtain the first curve of the flowability index changing with the frequency, and the cutoff frequency is determined based on the first curve. The cutoff frequency is the frequency that causes the flowability index to drop to the preset index threshold. The amplitude of the pulsation drive is changed to obtain the second curve of the cutoff frequency changing with the amplitude.

[0005] In one embodiment, before determining the critical threshold for the external fluid to drive the droplet through the pore throat contraction structure, the method further includes: establishing or importing a geometric model with the pore throat contraction structure, determining the geometric parameters of the pore throat contraction structure and the physical property parameters of the two-phase fluid; wherein the two-phase fluid includes an external fluid and an internal fluid, the internal fluid being a droplet; and the external fluid being a Newtonian fluid.

[0006] In one embodiment, determining the critical threshold for an external fluid to drive a droplet through a pore throat contraction structure includes: under non-pulsating driving conditions, gradually applying steady-state displacement of different intensities to the droplet through the external fluid to determine the minimum displacement intensity capable of driving the droplet through the pore throat contraction structure as the critical threshold; determining the subcritical baseline based on the critical threshold includes: selecting a displacement intensity lower than the critical threshold, with a difference from the critical threshold less than a preset difference, and causing the droplet to be trapped in the pore throat contraction structure as the subcritical baseline.

[0007] In one embodiment, the displacement intensity includes at least one of the velocity, flow rate, or pressure difference of the external phase fluid; the critical threshold is characterized by the displacement intensity or the capillary number; wherein the capillary number is determined based on the interfacial tension, the viscosity of the external phase fluid, and the velocity of the external phase fluid.

[0008] In one embodiment, before adaptively controlling the time step based on the current state information during the propulsion process, the method further includes: determining the minimum grid scale and the element feature edge length; the state information includes the minimum gap between the droplet interface and the solid boundary of the pore throat contraction structure; multiple physical constraints including at least two of minimum gap constraints, grid scale constraints, and tangential distortion constraints; wherein, the minimum gap constraint indicates that the normal propulsion amount of a single time step does not exceed a predetermined proportion of the minimum gap at the current time; the grid scale constraint indicates that the translation amount of a single time step does not exceed a predetermined proportion of the minimum grid scale; and the tangential distortion constraint indicates that the tangential propulsion amount of a single time step does not exceed a predetermined proportion of the element feature edge length.

[0009] In one embodiment, the state information includes the centroid position of the droplet at different times; before determining the truncated net axial displacement of the droplet within the pore-throat contraction structure within a fixed observation time window based on the state information of the droplet at different times, the method further includes: determining a frequency-independent fixed observation time window; the fixed observation time window includes a start time and an end time; determining the truncated net axial displacement of the droplet within the pore-throat contraction structure within the fixed observation time window based on the state information of the droplet at different times includes: calculating the difference between the second centroid position and the first centroid position based on the first centroid position of the droplet at the end time and the second centroid position of the droplet at the start time, and using the difference as the truncated net axial displacement of the droplet within the pore-throat contraction structure within the fixed observation time window.

[0010] In one embodiment, the subcritical baseline is represented by the average velocity of the external phase fluid within a fixed observation time window; based on the truncated axial net displacement, the flow index corresponding to the pulsating drive is obtained, including: calculating the product of the average velocity and the fixed observation time window; and using the ratio of the truncated axial net displacement to the product as the flow index.

[0011] In one embodiment, determining a fixed observation time window independent of frequency includes: determining the minimum cross-section of the pore throat of the pore throat contraction structure; taking the axis of the minimum cross-section as the Z direction; determining the inlet position of the droplet entering the pore throat contraction section and the outlet position of the droplet leaving the pore throat contraction section in the Z direction; taking the time corresponding to the droplet moving to the inlet position as the start time and the time corresponding to the droplet moving to the outlet position as the end time; and taking the time window between the start time and the end time as the fixed observation time window.

[0012] In one embodiment, the method further includes: taking the distance between the inlet and outlet locations in the Z direction as the orifice throat characteristic length; obtaining the orifice throat convection time based on the orifice throat characteristic length and the average displacement intensity; and taking the product of the orifice throat convection time and the angular frequency corresponding to the pulsating drive as the dimensionless frequency.

[0013] In one embodiment, after obtaining the fluidity index corresponding to the pulsation drive, the method further includes: comparing the fluidity index with a preset mobility determination threshold to obtain a mobility prediction result; the mobility prediction result is used to indicate whether the droplet is in a mobile state or a trapped state; after obtaining a second curve of the cutoff frequency changing with the amplitude, the method further includes: generating a chart in a preset format; the chart is used to represent the correspondence between frequency, amplitude and mobility prediction result.

[0014] In one embodiment, the solution framework is a three-dimensional interface solution framework suitable for Stokes flow, which includes at least one of boundary integral method, finite element method, finite volume method or lattice Boltzmann method.

[0015] In one embodiment, the waveform driven by the pulse is selected from at least one of a sine wave, a square wave, a triangle wave, a sawtooth wave, or a pulse train.

[0016] This invention also provides a pulsating flow driving device for porous media fluid flow. The device includes: a subcritical baseline determination module, used to determine the critical threshold for external phase fluid driving droplets through a pore throat contraction structure, and to determine the subcritical baseline based on the critical threshold; a pulsating drive generation module, used to apply steady-state displacement with a displacement intensity equal to the subcritical baseline to the droplets in the pore throat contraction structure, and to superimpose pulsating drive on the steady-state displacement, controlling the displacement intensity of the pulse drive to change periodically with time, so that the displacement intensity within one pulsating cycle after superimposing the pulse drive remains unchanged at the subcritical baseline; and an interface evolution and step size control module, used to call a pre-determined solution framework, and to advance the time history of the interface motion of the droplets under pulsating drive through the solution framework, solving for the droplets at different times... The system includes several modules: a state information module and a cutoff frequency module. The first module provides the state information at each moment. During propulsion, the system adaptively controls the time step based on the current state information, with the time step constrained by multiple physical constraints. The second module calculates the net axial displacement of the droplet within the pore-throat contraction structure within a fixed observation time window, based on the droplet's state information at different times. The third module obtains the flowability index corresponding to the pulsation drive based on the net axial displacement. The fourth module uses a frequency scanning and cutoff frequency identification module to keep the amplitude of the pulsation drive constant, change the frequency of the pulsation drive, obtain a first curve showing the flowability index changing with frequency, and determine the cutoff frequency based on the first curve. The cutoff frequency is the frequency that causes the flowability index to drop to a preset index threshold. The fifth module changes the amplitude of the pulsation drive to obtain a second curve showing the cutoff frequency changing with amplitude.

[0017] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement any of the above-described methods for improving the fluid flow of porous media by pulsating flow.

[0018] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any of the above-described methods for improving the fluid flow of porous media by pulsating flow.

[0019] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements any of the above-described methods for improving the fluid flow of porous media through pulsating flow.

[0020] The present invention provides a method, apparatus, and electronic device for improving the fluidity of porous media using pulsating flow. First, a critical threshold is determined for the external phase fluid to drive a droplet to pass precisely through a pore throat contraction structure. A subcritical baseline is then determined based on this critical threshold. Pulsating drive is superimposed on a steady-state displacement with an intensity equal to the subcritical baseline. The displacement intensity within one pulsation cycle after the superimposed pulse drive remains constant at the subcritical baseline. This ensures that comparisons of pulsating drive schemes with different frequencies and amplitudes are not affected by changes in the average displacement intensity (subcritical baseline). Furthermore, a pre-determined solution framework is invoked to advance the interface motion of the droplet under pulsating drive, solving for the droplet's state information at different times (e.g., position, velocity, minimum gap, etc.). During the advancement process, the subsequent time step is adaptively controlled in real-time under various physical constraints, combined with the current state information. By setting multiple physical constraints, numerical overlap / penetration during advancement can be avoided, interface advancement stability can be ensured, severe droplet stretching / compression can be prevented, and computational interruptions caused by mesh distortion can be avoided. Then, based on the droplet's state information at different times, the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window is determined. Based on this truncated axial net displacement, the flowability index corresponding to the pulsating drive is obtained. Then, the first curve of the flowability index versus frequency under fixed amplitude and different frequency conditions, and the second curve of the cutoff frequency versus amplitude under constant cutoff frequency and changing amplitude conditions are obtained. Thus, the critical threshold for passage / trapping is first determined, and a subcritical baseline slightly below the threshold is selected, allowing different pulsating drives to be compared at the same "trapping starting point," thereby improving the reproducibility and interpretability of the prediction conclusions. While keeping the average displacement intensity at the subcritical baseline and unchanged, time-varying pulsating drives are superimposed, only changing the relevant parameters of the pulsating drive, such as... Varying the amplitude or frequency allows the differences in droplet mobility to primarily originate from the pulsation-driven parameters themselves, making it more suitable for engineering parameter design and screening. It is reproducible and provides valuable parameter data for engineering applications. Furthermore, under pulsation-driven conditions, droplets exhibit rapid deformation and extremely small lubrication gaps within the pore throat. Traditional fixed step sizes or single constraints are prone to interface penetration, numerical overlap, or mesh distortion, thus affecting long-term integration and cutoff frequency identification. This invention employs multiple physical constraints to jointly limit the time step, ensuring physical feasibility and numerical stability. It reduces invalid calculations caused by interface penetration, numerical overlap, or mesh distortion, improving multi-cycle computation efficiency. Ultimately, this helps extract oil remaining in rocks and other media in engineering practice, increasing oil recovery rates. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic flowchart of the method for improving the fluid flow of porous media by pulsating flow provided in an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of a typical three-particle pore throat contraction structure and a curve of bound droplet motion in one embodiment of the method for improving the fluid flow of porous media by pulsating flow provided in this invention.

[0024] Figure 3 This is a schematic diagram of a pulsating flow method for improving the fluid flow of porous media provided in an embodiment of the present invention, maintaining a constant average displacement intensity (S(t) around S). mean (It makes periodic oscillations).

[0025] Figure 4 This is an example of the evolution curve of the droplet centroid displacement over time under representative pulsating parameters in one embodiment of the method for improving the fluid flow of porous media provided by the present invention.

[0026] Figure 5 This is a curve showing the evolution of the closest distance between a droplet and a solid over time under representative pulsating parameters in one embodiment of the method for improving the fluid flow of porous media provided by the present invention.

[0027] Figure 6 This is a schematic diagram of the typical interface morphology evolution of a droplet passing through the pore throat contraction section under pulsating drive in one embodiment of the method for improving the fluid flow of porous media provided by the present invention (selecting several key moments).

[0028] Figure 7 This is an embodiment of the method for improving the fluid flow of porous media using pulsating flow provided in this invention, specifically the difference in mesh quality index. Evolution curve over time.

[0029] Figure 8 This is a frequency-amplitude-mobility prediction result response spectrum in one embodiment of the method for improving the fluidity of porous media by pulsating flow provided in this invention.

[0030] Figure 9 This is a schematic diagram of the module structure of the pulsating flow driving device for porous media fluid flow provided in an embodiment of the present invention.

[0031] Figure 10 A schematic diagram of the structure of the electronic device provided in the embodiment of the present invention.

[0032] Figure label: 901: Subcritical baseline determination module; 902: Pulse drive generation module; 903: Interface evolution and step size control module; 904: Index calculation module; 905: Frequency scanning and cutoff frequency identification module; 1010: Processor; 1020: Communication interface; 1030: Memory; 1040: Communication bus. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] In oil and gas reservoir development and multiphase flow research, under the viscous-capillary dominated Stokes flow conditions, in a typical three-dimensional particle pore throat geometry, there is a relatively clear critical capillary number for steady-state compression: when the capillary number is higher than this threshold, droplets can be driven through the pore throat by steady-state flow; when the capillary number is slightly lower than this threshold, droplets will be trapped near the pore throat for a long time and hardly produce any net displacement, thus significantly limiting the pore-scale transport capacity.

[0035] In related technologies, some schemes apply pressure pulsations or low-frequency vibrations to improve residual oil recovery. For example, periodically modulating bottomhole pressure or applying elastic waves to the formation causes the pressure gradient and velocity field within the pores to oscillate over time. Studies show that pulsations or vibrations often have a certain "effective frequency range," within which the production enhancement effect is more significant, while above or below this range, the production enhancement effect weakens or even disappears. However, research in related technologies mostly focuses on core or macroscopic scale responses, lacking a systematic and quantitative explanation of the pulsation frequency and amplitude response of a single bound droplet at the pore scale in real three-dimensional pore-throat geometry.

[0036] Furthermore, some related technologies employ equivalent permeability or macroscopic yield increase analysis, lacking a readily intuitive pore-scale prediction index centered on the net displacement of droplets within the pore-throat contraction structure. In other words, these technologies lack a pore-scale "prediction process" for engineering applications. Given the geometric parameters, fluid properties, and steady-state average capillary number of the pore-throat contraction structure, currently, no reproducible scheme has been established to achieve the following technical objectives: under steady-state baseline conditions slightly below the critical capillary number, how do the pulsation frequency and amplitude jointly determine whether a droplet passes through the pore throat within a finite operating time, how much axial net displacement can be generated, where the high-frequency cutoff / threshold frequency appears, and how this frequency changes with amplitude.

[0037] In summary, the main technical problems of the existing technology are as follows: The focus is on macroscopic response, and the mapping or logical relationship between macroscopic response and corresponding driving strategy is unclear, resulting in poor interpretability. This means that there is no theoretical support for whether the same driving strategy can be applied to other oil production scenarios, i.e., it lacks engineering reproducibility. The lack of a boundary integral numerical framework suitable for time-varying pulsation drive under three-dimensional resolvable lubrication gap geometry makes it difficult to stably track the interface evolution of bound droplets over multiple pulsation cycles. There is a lack of predictive methods to systematically examine the effects of pulsation frequency and amplitude on the mobility of droplet apertures under steady-state subcritical capillary number baselines, especially the cutoff / threshold frequency and amplitude dependence of the high-frequency ineffective region. The lack of a practical prediction process that uses the net axial displacement of droplets as the core criterion and directly correlates pulsation parameters with "passing / trapped" results makes it difficult to provide a quantitative pore size design basis for pressure pulsation injection or vibration oil production.

[0038] In view of this, embodiments of the present invention propose a method, apparatus, and electronic device for improving the fluid flowability of porous media through pulsating flow. This is a quantitative prediction method for pore size that can be applied to engineering design. Under the condition of applying steady-state displacement with an intensity of subcritical baseline, time-varying pulsating drive is superimposed to simulate the interface evolution process of bound droplets passing through the "throat" of the pore throat contraction structure under pulsating drive. The solution is obtained through a preset solution framework (e.g., three-dimensional time-varying boundary integral numerical value), and adaptive time step control is performed during the evolution process. With the axial net displacement / finite-time fluidity index within a fixed observation time window as the core, a direct mapping between frequency, amplitude, and mobility is established, and the high-frequency cutoff / threshold frequency and its amplitude dependence law are identified, providing pore size basis for the optimization of pulsating injection or vibration oil production parameters.

[0039] The following describes, with reference to the accompanying drawings, a method, apparatus, and electronic device for improving the fluidity of porous media using pulsating flow according to embodiments of the present invention.

[0040] Figure 1This is one of the flowcharts illustrating the method for improving the fluid flow of porous media using pulsating flow provided by the present invention, such as... Figure 1 As shown, the specific process may include the following: Step 101: Determine the critical threshold for external phase fluid to drive droplets through the pore throat contraction structure, and determine the subcritical baseline based on the critical threshold.

[0041] In porous media flow theory, pore-throat contraction structures describe the geometric features encountered by fluids flowing through porous materials such as rocks, soils, and filter media. A pore (or pore body) is a relatively wide space where fluid can temporarily store or flow at a low speed. A throat (or throat passage) is a contracting channel connecting two pores. The microscopic pore network of rocks, soils, and filter media is composed of alternating "wide pores" and "narrow throats." This alternation of "wide-narrow-wide-narrow" forms the pore-throat contraction structure. The throat is the narrowest and most resistance-bearing part of the entire flow path, a crucial bottleneck controlling whether fluid can pass through and at what speed. In the field of oil and gas reservoir development, materials such as sandstone and carbonate rocks are porous media with pore-throat contraction structures at the microscopic level.

[0042] This invention relates to multiphase fluids, such as two-phase fluids. Two-phase fluids include a continuous phase (external phase) and a dispersed phase (internal phase), or in other words, an external phase fluid and an internal phase fluid. The external phase fluid is the outer phase of the two-phase fluid. The external phase fluid can be a Newtonian fluid; for example, the external phase fluid (continuous phase) can be water, which can fill the pore space and flow continuously. The droplets in step 101 are the internal phase, or internal phase fluid. For example, the dispersed phase (internal phase) can be oil, which is encapsulated and driven by water in the form of individual droplets or clumps. This invention investigates how an oil droplet (dispersed phase) passes through a pore throat under the drive of the water flow (continuous phase).

[0043] Before step 101, a geometric model with a pore throat contraction structure can be established or imported to determine the geometric parameters of the pore throat contraction structure and the physical property parameters of the two-phase fluid. The geometric parameters include at least one of the pore throat characteristic length, minimum cross-sectional characteristic length, or particle radius. The physical property parameters include at least one of the following: external phase viscosity, internal phase viscosity, interfacial tension, droplet volume, droplet equivalent radius, droplet initial position, or droplet attitude.

[0044] For example, the geometric model established or imported includes at least: a solid skeleton boundary composed of multiple particles or pore walls; and a pore throat contraction region with the minimum cross-section or minimum gap location.

[0045] The geometric model can be derived from regular particle packing or from digital core / microCT reconstruction models. For example, regular particle packing can be a pore throat contraction structure formed by three or more particles, and the embodiments of the present invention do not limit this.

[0046] The geometric parameters (or characteristic scale parameters of the pore throat contraction structure) include at least one of the following: pore throat characteristic length Lc, minimum cross-sectional characteristic length, particle radius, etc., which are used for dimensionless transformation or as the scale basis for observation window and threshold selection.

[0047] Physical property parameters refer to the inherent physical properties of the fluid (oil, water, etc.) and its interface and solid surface within the pore-throat contraction structure. For two-phase fluids, physical property parameters may specifically include: external phase viscosity μ. o Internal phase viscosity μ i The parameters include interfacial tension σ, droplet volume or equivalent radius, and initial position and orientation of the droplet. Optionally, in other embodiments, the physical properties may also include wettability / contact angle or equivalent boundary conditions.

[0048] It provides calculable geometric parameters of the pore throat contraction structure and physical property parameters of the two-phase fluid, so that the prediction results correspond to the geometric parameters of the specific pore throat contraction structure and the physical property parameters of the two-phase fluid. That is, the prediction results have corresponding microscopic parameter basis, rather than just relying on macroscopic experience fitting, thus enhancing the interpretability of the scheme.

[0049] Specifically, in step 101, the critical threshold for the external phase fluid to drive the droplet through the pore throat contraction structure is determined, and the subcritical baseline is determined based on the critical threshold. This can be achieved in the following way: Under pulsation-free driving conditions, steady-state displacement of varying intensities is gradually applied to the droplet by the external phase fluid to determine the minimum displacement intensity capable of driving the droplet through the pore-throat contraction structure as the critical threshold. Then, a displacement intensity below the critical threshold, with a difference from the critical threshold less than a preset difference, that traps the droplet within the pore-throat contraction structure is selected as the subcritical baseline. The preset difference represents the allowable error range, for example, 0.005-0.01. In other words, a displacement intensity with an average displacement intensity slightly below the critical threshold is selected as the subcritical baseline. The subcritical baseline is the displacement intensity that causes the droplet to exhibit a long-term or near-trapped state (with very small net displacement within a finite time) under pure steady-state displacement, serving as a benchmark for subsequent superimposed pulsations.

[0050] In the microscopic world of oil and gas extraction, steady-state displacement refers to using a stable external phase fluid (Newtonian fluid) to flush and push an oil droplet stuck in a rock crevice, such as using a stable water flow to flush and push an oil droplet stuck in a rock crevice.

[0051] Displacement intensity, also known as the driving force of the external phase fluid, can be expressed by the velocity, flow rate, or pressure difference of the external phase fluid. For example, if the external phase fluid is water, the displacement intensity of the water flow can be one of the velocity, pressure difference, or other equivalent volume force terms. Pressure difference refers to the manifestation of the macroscopic pressure gradient driving fluid flow at the scale of a single pore throat in a porous medium. Pressure difference can act directly on the droplet and is the source of viscous driving force.

[0052] Specifically, in one embodiment, under pulsation-free conditions, steady-state displacement (constant average displacement intensity) of varying intensities is gradually applied, and the ability of the droplet to pass through the pore throat is calculated or evaluated. The critical threshold at which the droplet just barely passes through the pore throat is determined; that is, the critical displacement intensity that marks the boundary between the states of passage and being trapped is used as the critical threshold. This critical threshold is essentially the displacement intensity, and therefore can be represented using the form of displacement intensity.

[0053] It should be noted that the critical threshold is characterized by displacement intensity or capillary number. Displacement intensity includes at least one of the external phase fluid's velocity, flow rate, or pressure difference; in other words, displacement intensity can be expressed using at least one of the external phase fluid's velocity, flow rate, or pressure difference. For example, displacement intensity can be expressed using velocity, flow rate, or pressure difference, such as using an equivalent pressure difference threshold or an equivalent flow rate threshold to represent the critical threshold.

[0054] If capillary number Ca is used crit Characterized by the critical threshold, capillary number Ca crit It can be determined based on interfacial tension, the viscosity of the external phase fluid, and the velocity of the external phase fluid (e.g., the average velocity over a preset time period). In other embodiments, other representations may also be used, and the embodiments of the present invention are not limited thereto.

[0055] Next, a displacement intensity with an average displacement intensity slightly below the threshold is selected as the subcritical baseline, for example, Ca. mean <Ca crit And Ca mean With Ca crit If the difference is less than the preset difference, the subcritical baseline causes the droplet to be in a long-term trapped or near-trapped state under pure steady-state displacement (with very small net displacement within a finite time). The determination and fixation of the subcritical baseline is a prerequisite for the subsequent frequency-amplitude mapping and cutoff frequency identification.

[0056] Step 101 can standardize the typical engineering problem of "insufficient steady-state mobilization of droplets", ensuring that the subsequent evaluation of pulsation effect is comparable and targeted, thereby improving the interpretability of the overall solution.

[0057] Specifically, related technologies often rely on macroscopic responses or empirical frequency bands to assess the effectiveness of pulsation, making it difficult to conduct a unified comparison at the aperture scale of "how to achieve mobilization through pulsation when the steady state is slightly below the mobilization threshold." This invention first determines the pass / trapped critical threshold and selects a subcritical average displacement intensity slightly below the threshold as a baseline, allowing comparison of different pulsation parameter combinations at the same "trapped starting point," thereby improving the reproducibility and interpretability of the prediction conclusions. In this way, the "subcritical steady-state trapped problem" is standardized into a comparable design baseline, enhancing the specificity and reproducibility of the prediction.

[0058] Step 102: Apply steady-state displacement with a displacement intensity of subcritical baseline to the droplets in the pore throat contraction structure. On the basis of steady-state displacement, superimpose pulsating drive and control the displacement intensity of the pulse drive to change periodically with time so that the displacement intensity within one pulsating cycle after superimposing the pulse drive remains unchanged at the subcritical baseline.

[0059] Step 102 proposes a steady-state displacement superposition pulsation driving mechanism to achieve pulsation driving superposition while keeping the average displacement intensity unchanged at the subcritical baseline.

[0060] For example, a pulsating drive can be superimposed on the subcritical baseline steady-state displacement, causing the displacement intensity to vary periodically over time. For example, the average displacement intensity can be expressed as the velocity, flow rate, pressure difference, or other equivalent volumetric forces of the external phase fluid at the inlet and outlet (far field) positions that can characterize the displacement intensity.

[0061] The pulsation drive is characterized by at least two parameters: the pulsation amplitude A and the pulsation frequency (or angular frequency) ω. The waveform of the pulsation drive can be one or more combinations of sine waves, square waves, triangular waves, sawtooth waves, and pulse trains. In one embodiment, a continuous periodic waveform is preferably used to scan the frequency response.

[0062] In this embodiment of the invention, by controlling the superposition method of the pulsating drive, the average value of the displacement intensity in the time dimension is maintained at the subcritical baseline level selected in step 101, that is, the subcritical baseline is used as the average displacement intensity S. mean This achieves "unchanged average and only periodic oscillations", thus ensuring a fair comparison of pulsation drive schemes with different frequencies / amplitudes and reflecting the contribution of the pulsation drive itself.

[0063] Step 102 involves superimposing pulsations while maintaining the average displacement intensity at the subcritical baseline and scanning their effects in subsequent steps. This allows the "periodic disturbance" of the pulsation injection / vibration oil production scheme in engineering to be formalized into controllable parameters (A, ω, waveform) at the borehole scale, providing parameter inputs for subsequent scanning and design.

[0064] The embodiments of the present invention maintain an average displacement intensity of S. meanA constant time-varying pulsation drive, changing only the amplitude A and frequency f (or ω), results in mobility differences primarily stemming from the pulsation parameters themselves, making it more suitable for engineering parameter design and selection. Thus, by superimposing pulsations while maintaining a constant average displacement intensity, the contributions of frequency / amplitude to mobility can be separated, avoiding comparison bias.

[0065] Step 103: Call the pre-determined solution framework and use the solution framework to advance the time history of the droplet's interface motion under pulsation drive, and solve for the state information of the droplet at different times.

[0066] In some embodiments, the solution framework is a three-dimensional interface solution framework suitable for Stokes flow, which includes at least one of the boundary integration method, finite element method, finite volume method, or lattice Boltzmann method. This invention does not limit the specific solution framework; any solution framework capable of outputting the droplet interface kinematics (velocity, position, etc.) and the minimum clearance with the solid boundary under geometric boundary conditions can be used as the solution framework in this invention. For example, in one embodiment, the solution framework is the boundary integration method.

[0067] Boundary integral method is an algorithm that only focuses on the boundary and not the interior. It transforms the complex partial differential equations that need to be solved in the entire three-dimensional space into equations that only need to be integrated on the boundaries such as the droplet surface and the solid wall, thus greatly reducing the amount of computation.

[0068] For example, the boundary integration method may include the following steps: (1) Simplify the equations: Focus the complex equations describing the fluid motion in the entire three-dimensional space on the boundary. Using Green's formula or other mathematical theorems and fundamental solutions, we obtain an integral equation that only involves the velocity and force at each point on the droplet surface and the solid wall.

[0069] (2) Boundary discretization: The continuous droplet surface and the throat wall are discretized using a number of small triangular (or quadrilateral) meshes. Physical quantities (such as velocity and force) are defined and calculated only at the vertices (nodes) of the mesh.

[0070] (3) Assemble the matrix: For each node in the mesh, an integral equation is given. The equation for each node includes the influence of all other nodes. Combine the equations of all nodes to form a huge linear system of equations: [coefficient matrix] × [unknown state information of all nodes (e.g., velocity)] = [vector composed of known parameters such as interface tension]. This matrix is ​​dense because each node is directly related to other nodes. The specific location in the matrix assembly step... When establishing equations for each node, numerical integration is required to calculate the elements of the coefficient matrix. This integration is performed on all boundary cells. Numerical integration can employ singular or near-singular integrals. Singular integrals: When the cell containing the integration point x exactly contains the observation point x0 itself, the Green's function G(x0, x) or T(x0, x) tends to infinity at x = x0 (diverges). Near-singular integrals: When the droplet is very close to the throat wall (the gap is extremely small), even if the observation point x0 is on the droplet and the integration point x is on a nearby solid wall (or vice versa), the distance r = |x0 - x| becomes very small. In this case, although the integrand is not truly infinite, the change is extremely drastic, and conventional numerical integration formulas (such as Gaussian integrals) will fail, leading to severely inaccurate results. If these singular and near-singular integrals are not handled correctly, the assembled coefficient matrix will contain huge errors, causing the entire linear equation system to fail to solve, the calculated interface velocity to be completely wrong, and the simulation to immediately collapse.

[0071] (4) Solve for state information: Solve the above linear equations using numerical methods to obtain the precise velocity vector at each node at the current time. Numerical methods may include LU decomposition or LU factorization or GMRES iterative method (Generalized Minimal Residual method).

[0072] (5) Advance update: Using the state information (e.g. velocity) obtained from the solution, move each node along the normal direction to update the shape of the droplet.

[0073] New position = old position + velocity × time step, then return to step (1), recalculate based on the new shape, enter the next time step, and repeat this cycle to dynamically track the deformation and movement of the droplet.

[0074] Boundary integral methods are particularly well-suited for handling problems involving infinite domains (vast spaces outside the pore throat) and singular interfacial forces (interfacial tensions concentrated on infinitely thin interfaces), which are typical characteristics of pore-scale flows. Boundary integral methods directly address the moving interface as the solution object, and tracking interface deformation is an inherent strength, avoiding the complex interface reconstruction required in volume methods. For the problem of a single droplet in a complex pore throat studied in this embodiment of the invention, the computational domain is mostly solid, while the fluid region is relatively complex but finite. Boundary integral methods only require meshing the droplet interface and the pore throat walls, avoiding filling the complex pore space with a large amount of invalid or difficult-to-generate volume meshes, making it the preferred method for such problems.

[0075] It should be noted that the specific discrete form of the boundary integral equation, the numerical processing of singular and near-singular integrals, the algorithm for solving linear equations, and the implementation of interface stabilization are all examples and are not intended to be necessary limitations on the technical solution of this invention.

[0076] Stokes flow, also known as creep flow or low Reynolds number flow, is characterized by negligible inertial forces compared to viscous forces. The flow is entirely dominated by the instantaneous balance between viscous forces and the pressure gradient. Inertial forces are the forces that maintain or change the state of motion of a fluid. Viscous forces are the forces that impede motion due to friction within the fluid. In Stokes flow, viscous forces >> inertial forces, and the inertial effect is so small as to be completely negligible. For example, when the Reynolds number is much less than 1 (e.g., Re < 0.1), the flow is in a Stokes flow state. Stokes flow can be understood as a low Reynolds number (Re < 0.1) viscous-capillary dominated fluid. The capillary number (or simply capillary) is the most crucial dimensionless number in multiphase flow and interface science, quantitatively characterizing the competition between the viscous forces driving fluid deformation and the interfacial tensions resisting deformation.

[0077] Specifically, an interface evolution solution framework suitable for low Reynolds number (Re<0.1) and viscous-capillary dominant conditions is adopted to advance the time history of droplet deformation and migration in the pore throat, and obtain the droplet interface and centroid position changing with time.

[0078] Time progression is a method that calculates the shape and position of a droplet at each instant, frame by frame, according to chronological order, thereby synthesizing the entire motion process of the droplet as it passes through the pore throat contraction structure. The time interval between adjacent frames (instances) is called the time step.

[0079] Time-propagation is a numerical solution method that discretizes continuous time into a series of tiny time steps and then calculates the state evolution of the system step by step. Starting from the initial moment, the system is calculated step by step according to an adaptively determined time step (Δt) to obtain the position, shape, and velocity of the droplet interface at each discrete time point, thereby reproducing its complete dynamic history under pulsating drive.

[0080] Step 104: During the advancement process, the time step is adaptively controlled based on the current state information. The time step is jointly limited by multiple physical constraints.

[0081] To address the issues of rapid droplet deformation and extremely small lubrication gaps during pulsation cycles, this invention employs adaptive time step control in interface propulsion, with the time step being jointly limited by multiple physical constraints.

[0082] In some embodiments, the state information solved during time-history progression includes the minimum gap between the droplet interface and the solid boundary of the pore throat contraction structure. During progression, adaptively controlling the time step based on the current state information can be achieved in the following manner: First, determine the minimum mesh size and the element characteristic edge length. Under the premise of satisfying at least two of the following constraints: minimum gap constraint, mesh size constraint, and tangential distortion constraint, determine the step size for the next time step. The minimum gap constraint indicates that the normal advance of a single time step does not exceed a predetermined proportion (e.g., 0.1-0.3) of the current minimum gap; the mesh size constraint indicates that the translation of a single time step does not exceed a predetermined proportion (e.g., 0.1-0.2) of the minimum mesh size; and the tangential distortion constraint indicates that the tangential advance of a single time step does not exceed a predetermined proportion (0.2-0.3) of the element characteristic edge length.

[0083] The solution framework can deduce the state information of the next time step based on the current state information obtained and the adaptively determined step size of the next time step.

[0084] In one embodiment, multiple physical constraints may include the three physical constraints described above: Minimum gap constraint: Limits the single-step normal advance to no more than a certain proportion of the current droplet-solid minimum gap to avoid numerical overlap / penetration.

[0085] Mesh Scale-Velocity Constraint: Limits the single-step interface translation to a certain proportion of the minimum mesh scale to ensure stable interface advancement.

[0086] Tangential distortion constraint: Limits the single-step tangential node movement to no more than a certain proportion of the element feature side length in order to maintain mesh quality and avoid severe stretching / compression.

[0087] During the process, the interface mesh is stabilized, for example, by tangential reparameterization / tangential stabilization of velocity, to avoid computational interruptions caused by mesh distortion.

[0088] The minimum mesh scale refers to the smallest characteristic size of all mesh elements in a grid used for discrete computational domains. In droplet interface simulation, the mesh specifically refers to the triangular facet mesh of the discrete droplet surface (i.e., the liquid-liquid interface). For surface triangular meshes, the minimum mesh scale usually refers to the shortest side length among all triangles. The minimum mesh scale can be determined during mesh generation or initial meshing and can be maintained dynamically or statically during computation through mesh optimization techniques (such as adaptive refinement, edge swapping, and node relaxation).

[0089] Mesh scale-velocity constraints are used to prevent interface self-intersection and excessive distortion. Within a time step Δt, the maximum displacement of interface nodes is limited to a predetermined proportion C1 of the minimum mesh scale (e.g., 0.3), ensuring that even in the finest mesh regions, node movement is controllable and will not cross neighboring cells in a single time step, leading to mesh intersections and entanglement (self-intersection) and causing computational crashes.

[0090] The characteristic edge length of a cell is a representative measure of the size of a specific mesh cell. It is not necessarily the shortest edge of the cell, but rather a quantity that characterizes the overall size of the cell. For a triangular mesh, the characteristic edge length L... cell The following methods can be used to determine this: The characteristic side length of a unit is equal to the equivalent side length, which is the side length of a square with the same area as a triangle. Element feature side length = circumradius or incircle diameter; Unit characteristic side length = average side length: the arithmetic mean of the three side lengths.

[0091] The element feature side length represents the average thickness of the mesh in this local region.

[0092] Tangential distortion constraint limits the distance a node can move in the tangential direction (i.e., along the interface direction) to no more than L within a time step. cell A ratio (e.g., 0.2 * L) cell ).

[0093] Minimum gap constraints and mesh scale-velocity constraints focus on the stability of normal motion (preventing penetration and jumping), while tangential distortion constraints are used to ensure the quality of tangential motion and prevent mesh distortion: in strong shear or tensile flows, nodes may be overstretched or compressed tangentially, causing triangles to become extremely flat or elongated. Such distorted meshes severely reduce interpolation and integration accuracy.

[0094] Step 104 solves the problem of long-term stable calculation of "multi-cycle pulsation + close contact + strong deformation", making the subsequent cutoff frequency identification repeatable.

[0095] Specifically, under pulsating drive, droplets undergo rapid deformation and extremely small lubrication gaps within the pore throat. Traditional fixed step sizes or single constraints are prone to interface penetration, numerical overlap, or mesh distortion, thus affecting long-term integration and cutoff frequency identification. This invention employs minimum gap constraints, mesh scale-velocity constraints, and tangential distortion constraints to jointly limit the time step, automatically subdividing the step size during the near-contact phase and automatically increasing the step size during the slow phase. This improves multi-cycle computational efficiency while ensuring physical feasibility and numerical stability. Thus, "three-constraint adaptive step size control" enhances the stability and efficiency of multi-cycle near-contact computation, reducing the risk of penetration / mesh instability.

[0096] Step 105: Based on the state information of the droplet at different times, determine the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window; based on the truncated axial net displacement, obtain the flow index corresponding to the pulsation drive.

[0097] In some embodiments, state information may include the centroid position of the droplet at different times. The subcritical baseline is represented by the average velocity of the external phase fluid within a fixed observation time window.

[0098] Specifically, before determining the truncated axial net displacement, a fixed observation time window independent of frequency needs to be determined. This embodiment of the invention first uses the orifice throat characteristic length... and average displacement rate Define convection timescale Based on this, time is dimensionless and expressed as T' , where t represents the time interval between the current moment and the start moment of the fixed observation time window. The dimensionless length corresponding to the fixed observation time window is denoted as . Its physical duration is That is, given feature length With average displacement intensity Then, it can be directly converted from the above formula to obtain . The selection follows the following empirical principles: First, The magnitude of the magnitude is comparable to the transit time required for a steady-state droplet to pass through at a slightly supercritical capillary number, thus ensuring that the fixed observation time window represents the duration of a typical "effective displacement." Here, the critical capillary number is the critical threshold, and the slightly supercritical capillary number can be greater than the critical threshold but with a difference from the critical threshold less than a preset difference, such as 0.01. Secondly, at the lowest pulsation frequency, this fixed observation time window contains a sufficient number of deformation-relaxation cycles, causing the droplet's centroid displacement to exhibit a stable long-term drift trend, rather than transient fluctuations in individual cycles. Thirdly, in the same... Within, the high-frequency calculation examples still significantly remain in a stagnant state in terms of engineering significance, thus forming a clear passing / stagnation contrast under a unified fixed observation time window. Numerical tests show that on the premise of meeting the above conditions, moderately increasing or decreasing will not change the criteria for passing and stagnation and the overall trend of frequency dependence. Therefore, in subsequent analyses, only by comparing different combinations of frequencies and amplitudes under a unified dimensionless observation time can the comparability of the results be ensured without introducing additional confusion in time scales.

[0099] Specifically, the fixed observation time window includes a start time and an end time; according to the state information obtained by solving, the difference between the first centroid position of the droplet at the end time and the second centroid position of the droplet at the start time is calculated, and this difference is used as the truncated axial net displacement of the droplet within the pore-throat constriction structure within the fixed observation time window. Then, the product of the average velocity and the fixed observation time window is calculated; the ratio of the truncated axial net displacement to the product is used as the fluidity index.

[0100] In this way, by defining the inlet position Xin and the outlet position Xout of the pore-throat constriction region and performing truncation processing on the axial (Z-direction) coordinates of the droplet centroid, only the effective axial advancement of the droplet within the pore-throat constriction region (pore-throat constriction section) is counted, avoiding the meaningless translation of the droplet in the distal channel from affecting the index. Within the fixed observation time window, the effective truncated axial net displacement of the droplet is calculated, and based on this, the fluidity index M within a finite time is constructed. The fluidity index M can be understood as a normalized representation of the effective advancement ability under unit time and unit average displacement intensity.

[0101] After obtaining the fluidity index M, the fluidity index M is compared with a preset mobility determination threshold M'. Specifically, when M≥M', it is determined that the parameter combination (i.e., the amplitude and frequency combination) of this pulsating drive can significantly mobilize the droplet within a finite operation time, and the droplet is in a "movable / effectively advancing" state; when M<M' and the displacement only shows small periodic reciprocation, it is determined as "effectively trapped / pulsation ineffective".

[0102] Step 105 adopts a processing mechanism of fixed observation time window + truncated axial net displacement + fluidity index M to provide an "single comparable index" oriented to engineering, and compress the complex interface evolution results into an output available for design and determination.

[0103] Specifically, analysis shows that using only instantaneous displacement amplitude or equivalent permeability is insufficient to establish a unified criterion at the pore scale, and comparisons are prone to bias due to varying period lengths at different frequencies. This invention employs the same observation time window (Tobs) for all frequency schemes and only counts the effective net displacement between the inlet (Xin) and outlet (Xout) of the contraction section. A finite-time mobility index (M) is constructed, and a threshold (M) is set to determine whether the device is movable or trapped, allowing the output results to be directly used for engineering scheme selection and comparison. Thus, by using a "fixed observation time window + contraction section cutoff displacement + mobility index M," fair cross-frequency comparisons are achieved, providing directly usable movable / trapped determination results.

[0104] Step 106: Keep the amplitude of the pulse drive constant, change the frequency of the pulse drive, obtain the first curve of the flow index changing with the frequency, and determine the cutoff frequency based on the first curve.

[0105] The cutoff frequency is the frequency at which the liquidity indicator drops to the preset threshold.

[0106] For example, under the condition that the above-mentioned geometric parameters, physical property parameters, and average displacement intensity remain unchanged, the amplitude is kept constant, the frequency of the pulsation drive is changed, the frequency of the pulsation drive is scanned, and at each frequency point, the flow index M is calculated according to the operation steps defined in steps 104-105. For each fixed amplitude A, the response curve of M as a function of frequency (the first curve) is obtained. In other words, the frequency corresponding to M=M' is taken as the high-frequency cutoff / threshold frequency, which is simply referred to as the cutoff frequency.

[0107] Step 107: Change the amplitude of the pulsation drive to obtain a second curve showing the change of cutoff frequency with amplitude.

[0108] Next, change the amplitude A and repeat steps 104-105 above to obtain the law of the cutoff frequency changing with the amplitude fc(A), and output the response spectrum (second curve) or recommended parameter band of "frequency-amplitude-flow index M" to guide the selection of pulse injection or vibration oil production parameters in engineering.

[0109] After the above steps, the boundary of the "effective frequency range / high-frequency ineffective region" that is of most concern to the project can be directly given, and quantitative basis for the change with amplitude can be provided.

[0110] It should be noted that while effective frequency bands can sometimes be randomly observed in engineering, comparable cutoff boundaries at the aperture scale are lacking. This embodiment of the invention scans frequencies under fixed geometry / properties / average displacement intensity, and identifies the cutoff / threshold frequency f that causes M to drop below a threshold based on the frequency variation of M. c (A), and f is obtained for different amplitudes. c(A) Curves or response spectra provide quantitative boundaries of the "effective / ineffective zone" for parameter selection in pulsating injection or vibratory oil recovery, reducing blind testing.

[0111] In this way, the cutoff / threshold frequency of the high-frequency invalid region can be identified and its variation with amplitude can be given, providing a quantitative boundary for avoiding the invalid parameter region.

[0112] The aforementioned beneficial effects can be verified under the same orifice-throat geometry, the same fluid properties, and the same subcritical average displacement intensity by comparing the "fixed step size or single-constraint step size strategy" with the "three-constraint adaptive control step size strategy," and by comparing the "non-fixed observation window / non-truncated displacement criterion" with the "fixed observation time window + truncated displacement + flowability index M criterion," respectively, from the perspectives of stability (whether it penetrates / whether it is interrupted), efficiency (number of steps or computation time), and mobility output (M-f curve and fc(A) curve).

[0113] Figure 1 The embodiment shown introduces a steady-state displacement superimposed with a subcritical baseline intensity into the geometric model of the three-dimensional pore throat contraction structure. During the time-history progression, an adaptive time step control based on physical constraints is adopted. The fluidity index and quantitative parameters such as the cutoff frequency are obtained by utilizing the droplet's axial net displacement. This approach is more interpretable, possesses the reproducibility required for engineering, and has practical application value. It helps to extract petroleum or other fluid resources remaining in media such as rocks, thereby improving extraction efficiency.

[0114] The following are some specific embodiments in conjunction with other accompanying drawings.

[0115] This embodiment uses the prediction of pulsation mobility in a typical three-dimensional particle pore throat contraction structure as an example for explanation.

[0116] Step 201: Setting the geometric parameters and physical property parameters of the geometric model.

[0117] First, such as Figure 2 As shown, a typical pore-throat contraction structure formed by the close packing of three spherical particles of equal diameter is selected as a representative model. The radius of the three spheres is taken as R. g The spacing between them is set to the minimum cross-section of the throat that causes it to shrink significantly. Figure 2 In the coordinate system, x, y, and z represent the x-axis, y-axis, and z-axis, respectively. Figure 2 The spheres in the diagram represent spherical particles, and three spherical particles form a pore throat contraction structure. Dark gray represents droplets. T represents time, and Z represents the coordinate of the droplet along the z-axis.

[0118] Define the inlet position X of the orifice throat contraction section with the orifice throat axis (the normal direction of the minimum cross section) as the z-axis direction. in With export location Xout (For example, taking the center of the smallest cross-section as the zero point, and selecting an axial position upstream and downstream sufficient to cover the contraction section), and [X in ,X out This serves as the statistical interval for truncating the net axial displacement.

[0119] Next, take the throat characteristic length L. c For the length of the contraction segment (e.g., L) c =X out -X in ), used to define fixed observation time windows and dimensionless frequencies.

[0120] The external phase fluid and droplet parameters (physical properties) also need to be configured: the external phase is a Newtonian fluid with a viscosity of μ. o The internal phase is a viscous droplet with a viscosity of μ. i Viscosity ratio λ=μ i / μ o The interfacial tension is σ. The droplet volume is taken as V. d or equivalent radius a d The initial centroid of the droplet is placed upstream of the pore throat contraction section, so that it will be blocked by the contraction section when the steady-state displacement is insufficient.

[0121] The geometric parameters and physical property parameters can be taken from typical engineering-related magnitudes, and specific values ​​can be filled in later in the embodiments; the embodiments of the present invention are not listed one by one.

[0122] Step 202: Determination of steady-state critical threshold and selection of subcritical baseline.

[0123] Apply steady-state displacement: Apply non-pulsating steady-state displacement so that the driving intensity at the far field (outlet position) or inlet position is a constant average displacement intensity S0, where S0 can be expressed as any one of the following: average velocity U0, average flow rate Q, or average pressure difference Δp0.

[0124] Critical threshold determination: Under the same geometric and physical parameters, the displacement intensity S0 is gradually changed, and it is calculated whether the droplet can pass through the pore throat contraction section within a preset time. The goal is to ensure that the droplet can pass through the contraction section within a finite time and that its center of mass reaches X. out The minimum displacement intensity is defined as the critical threshold S crit .

[0125] The critical threshold can be characterized by capillary number: Where U0 represents the average velocity, μ o σ represents the viscosity of the external phase fluid, and σ represents the interfacial tension. In other words, Ca corresponding to the passage / trapping boundary of the droplet is defined as Caout.crit .

[0126] Sub - critical baseline selection: Select the average displacement intensity S mean Satisfying S mean <S crit (or Ca mean <Ca crit ), and verify that under this condition, the droplet only has small reciprocating or extremely small net displacement within the observation time window, serving as the "steady - state trapped / near - trapped" baseline condition. This baseline is used for subsequent comparison of pulsation parameters to ensure that the starting points of different frequency schemes are consistent.

[0127] Pulsation - driving structure with constant average: As Figure 3 shown, superimpose a periodic pulsation on the sub - critical average displacement intensity S mean so that the displacement intensity changes with time as: (1) where A is the pulsation amplitude (for example, 0 < A < 1), f is the frequency of the pulsation driving, and g(⋅) is a periodic function. Preferably, g(⋅)=sin(⋅), and square wave, saw - tooth wave, triangular wave or pulse train can also be taken. In this embodiment, a sine waveform is selected for continuous frequency scanning.

[0128] Next, keep the average displacement intensity unchanged. Through the above - mentioned structure, the average value of S(t) in the time dimension within one pulsation period is S mean , thus ensuring that the comparison of different frequency and amplitude schemes is not interfered by the change of the average displacement intensity. [[ID=ID=37]]

[0129] Optionally, in a specific embodiment, the dimensionless frequency can be further calculated according to the previously determined pore - throat characteristic length L c : S mean When characterized by the average velocity U0, the pore - throat convection time (or convection time scale) τ a = L c / U0; Dimensionless frequency: ; As Figure 3 shown, the dimensionless frequency Ω is used to represent the relative relationship between the pulsation period and the pore - throat convection time. The dimensionless frequency Ω here is used to measure how fast the driving force changes relative to how fast the system itself flows, which is different from the frequency of the pulsation driving.

[0130] Step 203, multi - cycle interface advancement and three - constraint adaptive time - step control.

[0131] Combined with Figure 4, Figure 5 , Figure 6 and Figure 7 As shown, the interface evolution solution is first performed.

[0132] Under low Reynolds number and viscous-capillary dominant conditions, the deformation and migration of the droplet interface over time are solved, and the droplet interface position and centroid position X are output. c (t) and the minimum gap g between the droplet interface and the solid boundary. min (t).

[0133] in, Figure 4 The evolution curves of the droplet's center of mass displacement over time are shown under representative pulsation parameters. Figure 4 The horizontal axis represents time T, the vertical axis represents the coordinate of the droplet's center of mass in the Z direction, and A represents the amplitude.

[0134] In this embodiment, the boundary integration method suitable for Stokes flow is preferably used. However, this embodiment of the invention does not limit the solution framework to the boundary integration method, as long as the above output can be obtained under the predetermined boundary conditions.

[0135] Next, we will perform three-constraint adaptive time step control.

[0136] To ensure stable propulsion of the droplet during the rapid deformation and near-contact phases in each pulsation cycle, the time step Δt is adaptively updated, while simultaneously satisfying: a. Minimum clearance constraint: The single-step normal advance amount shall not exceed a predetermined proportion of the current minimum clearance; b. Mesh Scale - Velocity Constraint: The single-step translation amount shall not exceed a predetermined proportion of the minimum mesh scale; c. Tangential distortion constraint: The single-step tangential node motion does not exceed a predetermined proportion of the element feature side length.

[0137] like Figure 5 , Figure 6 and Figure 7 As shown, the above constraints prevent interface numerical penetration or severe mesh distortion, thereby enhancing mesh quality. Figure 5 The curves showing the evolution of the closest distance (minimum gap) between the droplet and the solid over time under representative pulsation parameters are presented. Figure 5 The horizontal axis represents time T, and the vertical axis represents the minimum gap gmin. Figure 6 The diagram illustrates the typical interface morphology evolution of a droplet passing through the pore throat contraction section under pulsating drive, under selected key moment conditions. Figure 6 The horizontal axis represents time T, and the vertical axis represents the coordinate of the droplet's center of mass in the Z-axis direction. Figures 4-7 In this context, A represents amplitude and 2πf represents angular frequency.

[0138] Specifically, the parameter qmin is used to represent the mesh quality, which is the degree to which the triangular facets are not flat: Where l1, l2, and l3 are the three side lengths of any triangular topological unit. Figure 7 The horizontal axis represents T, and the vertical axis is Δqmin, which is the difference between qmin corresponding to the new time step and qmin corresponding to the historical time step (e.g., the previous time step).

[0139] Time-lapse termination condition: For each set of pulsation driving parameters (A,f), advance the interface to the preset observation time window T. obs End, and record the entire process of X. c (t), g min (t) and the necessary interface form.

[0140] Step 204: Fix the observation time window and determine the cutoff displacement and flow index M.

[0141] First, fix the observation time window: select a fixed observation time window T that is independent of the frequency. obs This maintains consistency for all (A,f) combinations. For example, T is preferred. obs Several convection time orders are selected to balance engineering operation time and orifice-scale response.

[0142] Calculate the truncated net axial displacement: First, define the axial coordinates of the droplet: (2) X c (t) represents the position of the droplet's center of mass, X in Indicates the inlet location of the throat contraction segment, X out This indicates the exit position of the throat contraction section. This represents the axial coordinate. This allows us to only count the effective propulsion of the droplet in the Z direction within the contraction zone.

[0143] Calculate the finite-time liquidity indicator: (3) This represents the axial coordinate (first centroid position) of the droplet at the start of the fixed observation time window Tobs. This indicates that the droplet is within a fixed observation time window T. obs The axial coordinate at the end of the time (the position of the second centroid). M represents the liquidity index.

[0144] It should be noted that when the displacement intensity is characterized by flow rate or pressure difference, the flow rate or pressure difference can be used to replace U0 in formula (3). That is, other average displacement intensity scales equivalent to the average velocity are used for normalization to ensure the comparability of the indicators.

[0145] Movable / trapped determination: Set the threshold M' of the mobility index (the threshold for movable determination). When M≥M', it is determined as movable / effective advancement; when M<M' and only shows small-scale periodic reciprocation, it is determined as effectively trapped. The threshold M' can be set according to the pore throat scale and engineering mobilization requirements. For example, M' is preferably taken in the range of 0.05 to 0.1.

[0146] Step 205: Cut-off frequency identification and response spectrum output As Figure 8 shown, on the premise of keeping the amplitude unchanged, perform frequency scanning: At a fixed amplitude A, scan the frequency f from low to high, and repeat steps 203 to 204 to obtain the M(f) curve (the first curve).

[0147] Determine the cut-off / threshold frequency: Define the frequency that makes the mobility index M drop to the threshold M' as the high-frequency cut-off / threshold frequency f c (A) at this amplitude.

[0148] Amplitude dependence law and parameter recommendation: Figure 8 In, the horizontal axis ω represents the angular frequency, and the vertical axis represents the mobility index M. As Figure 8 shown, change the amplitude A and repeat the above frequency scanning to obtain f c (A) curve (the second curve) varying with the amplitude. Then, a chart in a preset format can be generated, and the chart is used to represent the corresponding relationship between frequency, amplitude and the prediction result of movability. For example, a response spectrum or parameter recommendation band of "frequency - amplitude - movability prediction result" is generated. The response spectrum or parameter recommendation band can be used to intuitively guide the parameter selection of pressure pulsation injection or vibration oil production schemes in oil production engineering, and preferably avoid the high-frequency ineffective area or the amplitude insufficient area.

[0149] In practical applications, after the pore medium geometry and fluid properties are given, the response spectrum of Ω (angular frequency) - A - ΔX* (movability prediction result) can be constructed on the representative pore throat geometry by using the method of the embodiment of the present invention. According to the desired net displacement target of the pore scale, select the appropriate pulsation frequency and amplitude range, and then use this to guide the design and optimization of the pressure pulsation injection or vibration oil production scheme.

[0150] The following describes the pulsating flow driving device for porous media fluid flow provided in the embodiments of the present invention. The pulsating flow driving device for porous media fluid flow described below can be referred to in correspondence with the pulsating flow method for improving the fluid flow of porous media fluid described above.

[0151] like Figure 9 As shown in the embodiment of the present invention, a pulsating flow driving device for porous media fluid flow is provided. The device includes: The subcritical baseline determination module 901 is used to determine the critical threshold for external phase fluid-driven droplets to pass through the pore throat contraction structure, and to determine the subcritical baseline based on the critical threshold.

[0152] The pulse drive generation module 902 is used to apply a steady-state displacement with a displacement intensity of subcritical baseline to the droplets in the pore throat contraction structure. The pulse drive is superimposed on the steady-state displacement, and the displacement intensity of the pulse drive is controlled to change periodically with time, so that the displacement intensity within one pulse cycle after the superimposed pulse drive remains unchanged at the subcritical baseline.

[0153] The interface evolution and step size control module 903 is used to call a pre-determined solution framework to advance the interface motion of the droplet under pulsation drive in time and solve the state information of the droplet at different times. During the advancement process, the time step size is adaptively controlled according to the state information at the current time. The time step size is jointly limited by a variety of physical constraints.

[0154] The index calculation module 904 is used to determine the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window based on the state information of the droplet at different times; and to obtain the flow index corresponding to the pulsation drive based on the truncated axial net displacement.

[0155] The frequency scanning and cutoff frequency identification module 905 is used to keep the amplitude of the pulse drive constant, change the frequency of the pulse drive, obtain a first curve of the liquidity index changing with the frequency, and determine the cutoff frequency based on the first curve; the cutoff frequency is the frequency that causes the liquidity index to drop to a preset index threshold; and change the amplitude of the pulse drive to obtain a second curve of the cutoff frequency changing with the amplitude.

[0156] Figure 10 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 10As shown, the electronic device may include a processor 1010, a communications interface 1020, a memory 1030, and a communication bus 1040, wherein the processor 1010, the communications interface 1020, and the memory 1030 communicate with each other via the communication bus 1040. In some embodiments, the processor 1010 may include a processor 10 as described in any of the above embodiments, for example, the processor 1010 may be a processor 10 as described in any of the above embodiments, or the processor 1010 may be a processor array composed of processors 10 as described in any of the above embodiments.

[0157] Furthermore, the logical instructions in the aforementioned memory 1030 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0158] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to perform the method for improving the fluid flow of porous media by pulsating flow provided by the above methods, the method comprising: The critical threshold for external fluid-driven droplets passing through a pore-throat contraction structure is determined, and a subcritical baseline is established based on this threshold. A steady-state displacement with a displacement intensity equal to the subcritical baseline is applied to the droplets within the pore-throat contraction structure. Pulsating drive is then superimposed on this steady-state displacement, controlling the displacement intensity of the pulsed drive to vary periodically over time, ensuring that the displacement intensity remains constant within one pulse cycle after the superimposed pulsed drive. A pre-defined solution framework is invoked to advance the interfacial motion of the droplets under pulsating drive over time, solving for the droplet's state information at different moments. During this advancement process, the state at the current moment is analyzed... The information adaptive control time step is limited by multiple physical constraints. Based on the droplet's state information at different times, the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window is determined. Based on the truncated axial net displacement, the flowability index corresponding to the pulsation drive is obtained. The amplitude of the pulsation drive is kept constant, and the frequency of the pulsation drive is changed to obtain a first curve of the flowability index changing with frequency. The cutoff frequency is determined based on the first curve. The cutoff frequency is the frequency that causes the flowability index to drop to a preset index threshold. The amplitude of the pulsation drive is changed to obtain a second curve of the cutoff frequency changing with amplitude.

[0159] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a method for improving the fluid flow of porous media by pulsating flow as provided in the above methods, the method comprising: The critical threshold for external fluid-driven droplets passing through a pore-throat contraction structure is determined, and a subcritical baseline is established based on this threshold. A steady-state displacement with a displacement intensity equal to the subcritical baseline is applied to the droplets within the pore-throat contraction structure. Pulsating drive is then superimposed on this steady-state displacement, controlling the displacement intensity of the pulsed drive to vary periodically over time, ensuring that the displacement intensity remains constant within one pulse cycle after the superimposed pulsed drive. A pre-defined solution framework is invoked to advance the interfacial motion of the droplets under pulsating drive over time, solving for the droplet's state information at different moments. During this advancement process, the state at the current moment is analyzed... The information adaptive control time step is limited by multiple physical constraints. Based on the droplet's state information at different times, the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window is determined. Based on the truncated axial net displacement, the flowability index corresponding to the pulsation drive is obtained. The amplitude of the pulsation drive is kept constant, and the frequency of the pulsation drive is changed to obtain a first curve of the flowability index changing with frequency. The cutoff frequency is determined based on the first curve. The cutoff frequency is the frequency that causes the flowability index to drop to a preset index threshold. The amplitude of the pulsation drive is changed to obtain a second curve of the cutoff frequency changing with amplitude.

[0160] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0161] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0162] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the fluidity of porous media using pulsating flow, characterized in that, The method includes: Determine the critical threshold for external phase fluid-driven droplets to pass through the pore throat contraction structure, and determine the subcritical baseline based on the critical threshold; A steady-state displacement with a displacement intensity of the subcritical baseline is applied to the droplets in the pore throat contraction structure. A pulsed drive is superimposed on the steady-state displacement, and the displacement intensity of the pulsed drive is controlled to change periodically with time so that the displacement intensity within one pulse cycle after the superimposed pulsed drive remains unchanged at the subcritical baseline. A predetermined solution framework is invoked to advance the interface motion of the droplet under the pulsation drive in time, and the state information of the droplet at different times is solved. During the advancement process, the time step is adaptively controlled according to the state information at the current time, and the time step is jointly limited by multiple physical constraints. Based on the state information of the droplet at different times, the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window is determined; based on the truncated axial net displacement, the flowability index corresponding to the pulsation drive is obtained. The amplitude of the pulse drive is kept constant, and the frequency of the pulse drive is changed to obtain a first curve of the liquidity index changing with the frequency, and the cutoff frequency is determined based on the first curve; the cutoff frequency is the frequency that causes the liquidity index to drop to a preset index threshold. By changing the amplitude of the pulsed drive, a second curve showing the change of cutoff frequency with amplitude is obtained.

2. The method according to claim 1, characterized in that, Before determining the critical threshold for an externally driven droplet to pass through a pore throat contraction structure, the method further includes: Establish or import a geometric model with a pore throat contraction structure, and determine the geometric parameters of the pore throat contraction structure and the physical property parameters of the two-phase fluid; The two-phase fluid includes an external phase fluid and an internal phase fluid, wherein the internal phase fluid is the droplet and the external phase fluid is a Newtonian fluid.

3. The method according to claim 1, characterized in that, Determining the critical threshold for external phase fluid-driven droplets to pass through a pore throat contraction structure includes: Under non-pulsating driving conditions, the droplet is gradually subjected to steady-state displacement of different intensities by the external phase fluid, and the minimum displacement intensity that can drive the droplet through the pore throat contraction structure is determined as the critical threshold. Determining a subcritical baseline based on the critical threshold includes: selecting a displacement intensity that is lower than the critical threshold, has a difference from the critical threshold that is less than a preset difference, and causes the droplet to be trapped in the pore throat contraction structure as the subcritical baseline.

4. The method according to claim 1, characterized in that, The displacement intensity includes at least one of the velocity, flow rate, or pressure difference of the external phase fluid; The critical threshold is characterized by displacement intensity or capillary number; wherein the capillary number is determined based on interfacial tension, viscosity of the external phase fluid, and velocity of the external phase fluid.

5. The method according to any one of claims 1-4, characterized in that, Before adaptively controlling the time step based on the current state information during the advancement process, the method further includes: Determine the minimum grid size and the characteristic side length of the element; The state information includes the minimum gap between the interface of the droplet and the solid boundary of the pore throat contraction structure; The various physical constraints include at least two of the following: minimum gap constraint, mesh scale constraint, and tangential distortion constraint. The minimum gap constraint is used to indicate that the normal advance of a single time step does not exceed a predetermined proportion of the minimum gap at the current time. The grid scale constraint is used to indicate that the translation amount of a single time step does not exceed a predetermined proportion of the minimum grid scale; The tangential distortion constraint means that the tangential advance amount of a single time step does not exceed a predetermined proportion of the element feature side length.

6. The method according to claim 1, characterized in that, The state information includes the centroid position of the droplet at different times; Based on the state information of the droplet at different times, before determining the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window, the method further includes: A fixed observation time window, independent of frequency, is determined; the fixed observation time window includes a start time and an end time. Based on the state information of the droplet at different times, determine the truncated net axial displacement of the droplet within the pore throat contraction structure within a fixed observation time window, including: Based on the first centroid position of the droplet at the end time and the second centroid position of the droplet at the beginning time, the difference between the second centroid position and the first centroid position is calculated, and the difference is used as the truncated axial net displacement of the droplet within the orifice-throat contraction structure within a fixed observation time window.

7. The method according to claim 6, characterized in that, The subcritical baseline is represented by the average velocity of the external phase fluid within the fixed observation time window; Based on the truncated axial net displacement, the flow index corresponding to the pulsation drive is obtained, including: Calculate the product of the average velocity and the fixed observation time window; The ratio of the net axial displacement of the cutoff point to the product is used as the flowability index.

8. The method according to claim 6 or 7, characterized in that, Determine a fixed observation time window that is independent of frequency, including: Determine the minimum cross-section of the throat of the pore throat contraction structure, and take the axis of the minimum cross-section as the Z direction. Determine the inlet position of the droplet entering the throat contraction section and the outlet position of the droplet leaving the throat contraction section in the Z direction. The time when the droplet moves to the inlet position is taken as the start time, and the time when the droplet moves to the outlet position is taken as the end time. The time window between the start time and the end time is used as the fixed observation time window.

9. The method according to claim 8, characterized in that, The method further includes: The distance between the inlet position and the outlet position in the Z direction is taken as the throat feature length; The pore throat convection time is obtained based on the pore throat characteristic length and the average displacement intensity. The product of the pore throat convection time and the angular frequency corresponding to the pulsation drive is taken as the dimensionless frequency.

10. The method according to claim 1, characterized in that, After obtaining the liquidity indicator corresponding to the pulse-driven mechanism, the method further includes: The fluidity index is compared with a preset mobility determination threshold to obtain a mobility prediction result; the mobility prediction result is used to indicate whether the droplet is in a mobile state or a trapped state. After obtaining the second curve of the cutoff frequency as a function of amplitude, the method further includes: Generate a chart in a preset format; the chart is used to represent the correspondence between frequency, amplitude and mobility prediction results.

11. The method according to claim 1, characterized in that, The solution framework is a three-dimensional interface solution framework applicable to Stokes flow, and the three-dimensional interface solution framework includes at least one of the boundary integral method, finite element method, finite volume method or lattice Boltzmann method.

12. The method according to claim 1, characterized in that, The waveform of the pulse drive is selected from at least one of sine wave, square wave, triangle wave, sawtooth wave or pulse train.

13. A device for driving pulsating flow in porous media, characterized in that, The device includes: The subcritical baseline determination module is used to determine the critical threshold for external phase fluid-driven droplets to pass through the pore throat contraction structure, and to determine the subcritical baseline based on the critical threshold. The pulse drive generation module is used to apply a steady-state displacement with a displacement intensity of the subcritical baseline to the droplets in the pore throat contraction structure, and to superimpose a pulse drive on the steady-state displacement, controlling the displacement intensity of the pulse drive to change periodically with time, so that the displacement intensity within one pulse cycle after superimposing the pulse drive remains unchanged at the subcritical baseline. The interface evolution and step size control module is used to call a pre-determined solution framework, and to advance the interface motion of the droplet under the pulsation drive through the solution framework to solve the state information of the droplet at different times. During the advancement process, the time step size is adaptively controlled according to the state information at the current time, and the time step size is jointly limited by multiple physical constraints. The index calculation module is used to determine the truncated axial net displacement of the droplet within the pore throat contraction structure within a fixed observation time window based on the state information of the droplet at different times; and to obtain the flow index corresponding to the pulsation drive based on the truncated axial net displacement. The frequency scanning and cutoff frequency identification module is used to keep the amplitude of the pulse drive constant, change the frequency of the pulse drive, obtain a first curve of the liquidity index changing with the frequency, and determine the cutoff frequency based on the first curve; the cutoff frequency is the frequency that causes the liquidity index to drop to a preset index threshold; and change the amplitude of the pulse drive to obtain a second curve of the cutoff frequency changing with the amplitude.

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