Method and device for testing foam seepage characteristics of heterogeneous porous medium

Abstract

The embodiment of the invention discloses a method and device for testing foam seepage characteristics of a heterogeneous porous medium, electronic equipment and a storage medium, and relates to the technical field of fluid mechanics and nuclear magnetic resonance. The method comprises the steps that a heterogeneous porous medium sample with a clear permeability level difference is prepared, and the permeability level difference of the heterogeneous porous medium sample is determined; setting test parameters according to the permeability level difference of the sample, calibrating imaging parameters of the low-field nuclear magnetic resonance equipment, and setting a weighting mode; performing foam flooding treatment on the sample according to the set injection parameters, acquiring a spectrum of the sample according to the test parameters when foam is injected into a set amount, and acquiring nuclear magnetic imaging of the sample through low-field nuclear magnetic resonance equipment according to imaging parameters and a weighting mode; according to the relaxation characteristic of the spectrum, the main peak endpoint value is used for dividing the pore channel, the foam sweep degree is calculated according to the spectrum peak area of the spectrum, and the foam plugging strength is calculated according to the signal amplitude of nuclear magnetic imaging. According to the method, the problems of poor visualization adaptability and lack of evaluation systems in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the fields of fluid mechanics and nuclear magnetic resonance technology, and in particular to a method and apparatus for testing and evaluating the seepage characteristics of heterogeneous porous media foam. Background Technology

[0002] With the continuous development of fields such as oil extraction, soil remediation and underground engineering, the study of foam infiltration behavior in heterogeneous porous media (such as media with permeability differences, fractured media, etc.) has become increasingly crucial.

[0003] In oilfield foam flooding development, accurately understanding the seepage characteristics of foam in heterogeneous reservoirs is of great significance for improving oil recovery. In soil organic pollution remediation and groundwater pollution seepage prevention, understanding the flow law of foam in complex porous media helps to optimize remediation schemes. In underground engineering grouting, the seepage behavior of foam directly affects the grouting effect.

[0004] However, current foam seepage characteristic testing faces two major challenges. On the one hand, the internal pores of real porous media such as rocks and concrete are invisible, and apparent experiments can only extract external parameters such as flow rate and pressure, making it difficult to determine the true flow state of the internal pores. On the other hand, traditional visualization techniques such as glass etching models and acrylic 3D printing models are mostly two-dimensional thin models, which cannot accurately simulate the heterogeneous three-dimensional real porous environment and the dynamic seepage process of foam, making it difficult to meet practical needs.

[0005] Therefore, there is an urgent need for a testing and evaluation method that can accurately and comprehensively test and evaluate the characteristics of foam seepage in heterogeneous porous media. Summary of the Invention

[0006] The embodiments of this invention provide a testing method for the seepage characteristics of heterogeneous porous media foam, addressing the problems of poor visualization adaptability and difficulty in reproducing real-world environments in existing technologies, as well as the lack of a quantitative evaluation system for foam seepage characteristics leading to large deviations between results and reality. The technical solution is as follows: According to one aspect of the present invention, a method for testing the foam seepage characteristics of a heterogeneous porous medium, the method comprising: preparing a heterogeneous porous medium sample with a defined permeability gradient; preheating and calibrating the basic parameters of a low-field nuclear magnetic resonance (NMR) device; setting test parameters according to the permeability gradient of the sample; calibrating the imaging parameters of the low-field NMR device according to the permeability gradient of the sample, and setting a weighting method; the NMR imaging being used to visualize the seepage characteristics of foam in the high and low permeability layers of the sample; performing foam-driven treatment on the sample according to the set injection parameters; and obtaining the sample's permeability characteristics according to the test parameters at a set foam injection volume. The spectrum is analyzed, and the nuclear magnetic resonance imaging of the sample is acquired using the low-field nuclear magnetic resonance device according to the imaging parameters and weighting method; according to the... The relaxation characteristics of the spectrum are used to divide the channels into small, medium, and large channels using the peak endpoint values. The extent of foam spread is calculated based on the peak area of ​​the spectrum, and the foam sealing strength is calculated based on the signal amplitude of the nuclear magnetic resonance imaging.

[0007] In one embodiment, the preparation of a heterogeneous porous media sample with a clear permeability gradient is achieved through the following steps: selecting non-magnetic quartz sand, calcium carbonate powder, or glass microspheres as the substrate, separating at least two different particle sizes through a sieve, and washing and drying them; the different particle sizes correspond to different homogeneous parts; adding epoxy resin binder to the particles according to a set mass percentage and stirring until uniformly mixed, and laying the mixed particles layer by layer from low permeability layer to high permeability layer in a mold and pressing to obtain an initial sample; baking the initial sample and drilling according to a set pore volume so that the initial sample has high and low permeability regions in the radial direction that meet the set requirements to obtain a heterogeneous porous media sample.

[0008] In one embodiment, the low-field NMR device is preheated and its basic parameters are calibrated. The test parameters are set according to the permeability difference of the sample through the following steps: the low-field NMR device is preheated; the center frequency and radio frequency pulse width of the low-field NMR device are calibrated according to the water sample with known relaxation time; the test parameters are set according to the permeability difference of the sample; the test parameters include echo time, delay time, and number of scans; the number of scans is set to compensate for weak signals in the low-permeability region.

[0009] In one embodiment, the imaging parameters of the low-field NMR device are calibrated based on the permeability difference of the sample, and the weighting method is set through the following steps: the center frequency, automatic homogenization field parameters, and pulse duration of the low-field NMR device are calibrated using a standard sample to ensure the imaging resolution meets the set requirements; the field of view, imaging orientation, and number of slices of the low-field NMR device are adjusted according to the size of the sample; when the permeability difference is less than the set value, a weighting method is adopted. Weighted imaging extends the resampling waiting time and echo time. When the permeability difference is greater than the set value, proton density-weighted imaging is used to extend the resampling waiting time and shorten the echo time.

[0010] In one embodiment, the sample is subjected to foam impregnation treatment according to set injection parameters, and the sample is obtained according to the test parameters when the set amount of foam is injected. The NMR spectrum of the sample, acquired using the low-field NMR device according to the imaging parameters and weighting method, is achieved through the following steps: the sample is dried and vacuumed, then saturated with simulated formation water, and the baseline of the sample at this time is obtained using the low-field NMR device. Spectroscopy and benchmark MRI; The spectrum is used to represent the distribution characteristics of foam in different channels of the sample; foam is prepared and injected into the sample according to set injection parameters, stopping after each set volume is injected, and the sample is acquired by the low-field nuclear magnetic resonance device. The sample was cleaned after spectral and nuclear magnetic resonance imaging until the injection pressure stabilized.

[0011] In one embodiment, after acquiring the nuclear magnetic resonance imaging of the sample, the method further includes the following steps: performing a unified mapping on the nuclear magnetic resonance imaging and adding JET pseudocolor, and acquiring dynamic seepage data; the dynamic seepage data is used to demonstrate the influence of injection parameters on seepage characteristics; the JET pseudocolor is used to enhance the clarity of the gas-liquid interface and intuitively present the seepage distribution characteristics of foam in high and low permeability layers.

[0012] In one embodiment, according to the The relaxation characteristics of the spectrum are determined by dividing the channel into small, medium, and large channels using the peak endpoint values. This is achieved through the following steps: using the aforementioned reference... Based on the main peak endpoint of the spectrum, according to The relaxation time divides the channels in the sample into small channels, medium channels, and large channels.

[0013] In one embodiment, according to the The calculation of foam sweep extent from the spectral peak area is achieved through the following steps: based on the aforementioned benchmark. The peak area of ​​the spectrum and the sample during foam injection. The formula for calculating the peak area of ​​the spectral spectrum and the foam sweep extent E is as follows: ; in, For the sample during foam injection Spectrum The signal amplitude at each sampling point For the benchmark Spectrum The signal amplitude of each sampling point, where n is the total number of sampling points.

[0014] In one embodiment, the foam plugging strength is calculated based on the signal amplitude of the nuclear magnetic resonance imaging (NMR) image through the following steps: calculating the foam plugging strength based on the signal amplitude of the reference NMR imaging acquisition point and the signal amplitude of the NMR imaging acquisition point of the sample during foam injection. The calculation formula is as follows: ; in, For the first nuclear magnetic resonance imaging of the sample during foam injection. The signal amplitude at each sampling point For the reference MRI, the first The signal amplitude of each sampling point, nh is the total number of sampling points in the high-permeability layer, and nl is the total number of sampling points in the low-permeability layer.

[0015] According to one aspect of the present invention, a testing apparatus for the foam seepage characteristics of heterogeneous porous media, the apparatus comprising: a sample preparation and parameter setting module, used for preparing a heterogeneous porous media sample with a defined permeability gradient, preheating and calibrating a low-field nuclear magnetic resonance (NMR) device, and setting test parameters according to the permeability gradient of the sample; an NMR imaging parameter optimization module, used for calibrating the imaging parameters of the low-field NMR device according to the permeability gradient of the sample, and setting a weighting method; the NMR imaging is used to present the seepage characteristics of foam in the high and low permeability layers of the sample; and a foam seepage testing module, used for performing foam-driven treatment on the sample according to set injection parameters, and obtaining the sample's permeability gradient at a set foam injection amount according to the test parameters. The spectrum is analyzed, and nuclear magnetic resonance imaging of the sample is acquired using the low-field nuclear magnetic resonance device according to the imaging parameters and weighting method; the foam seepage effect evaluation module is used to evaluate the foam seepage effect based on the... The relaxation characteristics of the spectrum are used to divide the channels into small, medium, and large channels using the peak endpoint values. The extent of foam spread is calculated based on the peak area of ​​the spectrum, and the foam sealing strength is calculated based on the signal amplitude of the nuclear magnetic resonance imaging.

[0016] According to one aspect of the present invention, an electronic device includes at least one processor and at least one memory, wherein computer-readable instructions are stored on the memory; the computer-readable instructions are executed by one or more of the processors to cause the electronic device to implement the test method for the percolation characteristics of heterogeneous porous media foam as described above.

[0017] According to one aspect of the invention, a storage medium has computer-readable instructions stored thereon, which are executed by one or more processors to implement the test method for the foam seepage characteristics of heterogeneous porous media as described above.

[0018] The beneficial effects of the technical solution provided by this invention are: In the above technical solution, this invention first prepares heterogeneous porous media samples with clear permeability differences and preheats and calibrates a low-field nuclear magnetic resonance (NMR) device, setting test and imaging parameters according to the sample characteristics. Subsequently, the sample is subjected to foam flooding treatment using the set injection parameters, and spectral and NMR images of the sample are acquired at specific injection volumes to present the seepage characteristics of foam in high and low permeability layers. Furthermore, pore types are classified based on the relaxation characteristics of the spectrum, and the foam sweep rate is calculated using the spectral peak area. Simultaneously, the foam plugging strength is evaluated based on the NMR imaging signal amplitude. This method enhances imaging clarity through unified mapping and the addition of JET pseudocolor, intuitively displaying the seepage distribution. Finally, by integrating multi-dimensional data, accurate testing and evaluation of foam seepage characteristics in heterogeneous porous media are achieved, providing an effective technical means for oilfield development, soil remediation, and other fields, significantly improving testing accuracy and practicality. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating a test method for the seepage characteristics of a heterogeneous porous media foam according to an exemplary embodiment; Figure 2 This is a schematic diagram illustrating the sealing effect of different foam injection parameters in an exemplary embodiment; Figure 3 yes Figure 2 A schematic diagram of the different types of channels in the heterogeneous sandstone core in the corresponding embodiment; Figure 4 yes Figure 2 A schematic diagram of the T2 spectrum collected during foam injection into a heterogeneous sandstone core in the corresponding embodiment; Figure 5 yes Figure 2 A schematic diagram of nuclear magnetic resonance imaging acquired during the foam injection process in the corresponding embodiment; Figure 6 yes Figure 2 Schematic diagram of sweep efficiency of large-aperture channels under different injection parameters in the corresponding embodiment; Figure 7 yes Figure 2 The sweep efficiency of the central channel under different injection parameters in the corresponding embodiments; Figure 8 yes Figure 2 The sweep efficiency of the small channel under different injection parameters in the corresponding embodiments; Figure 9This is a block diagram of a test apparatus for the seepage characteristics of a heterogeneous porous media foam, according to an exemplary embodiment. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this disclosure means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or wireless coupling. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0023] This invention provides a testing method for the foam seepage characteristics of heterogeneous porous media. By preparing heterogeneous porous media samples and utilizing low-field nuclear magnetic resonance (NMR) technology for testing and imaging, it achieves precise visualization and quantitative evaluation of foam seepage characteristics, solving the problems of poor visualization adaptability and lack of quantitative evaluation system in traditional methods. This testing method for the foam seepage characteristics of heterogeneous porous media is applicable to testing devices for the foam seepage characteristics of heterogeneous porous media, which can be electronic devices. The testing method for the foam seepage characteristics of heterogeneous porous media in this invention can be applied to various scenarios, such as oilfield foam flooding development, soil organic pollution remediation, groundwater pollution seepage prevention, underground engineering grouting, etc.

[0024] Please see Figure 1 This invention provides a test method for the seepage characteristics of heterogeneous porous media foam, which is applicable to electronic devices.

[0025] In the following method embodiments, for ease of description, the execution subject of each step of the method is an electronic device, but this does not constitute a specific limitation.

[0026] like Figure 1 As shown, the method may include the following steps: Step 110: Prepare heterogeneous porous media samples with a clear permeability difference, preheat the low-field nuclear magnetic resonance equipment and calibrate the basic parameters, and set the test parameters according to the permeability difference of the samples.

[0027] In one possible implementation, non-magnetic quartz sand, calcium carbonate powder, or glass microspheres are selected as the substrate. At least two different particle sizes are separated by sieving, and the particles are washed and dried. Epoxy resin binder is added to the particles according to a set mass percentage and stirred until uniformly mixed. The mixed particles are then laid layer by layer in a mold from low-permeability layer to high-permeability layer and pressed to obtain an initial sample. The initial sample is then baked and drilled according to a set pore volume to create high- and low-permeability regions in the radial direction of the initial sample that meet the set requirements, resulting in a heterogeneous porous medium sample.

[0028] In one possible implementation, the low-field NMR device is preheated, and its center frequency and radio frequency pulse width are calibrated based on water samples with known relaxation times; test parameters are set according to the permeability differences of the samples.

[0029] Different particle sizes correspond to different homogeneous regions; test parameters include echo time, delay time, and number of scans, none of which are specified here; the number of scans is set to compensate for weak signals in low-permeability areas.

[0030] Specifically, non-magnetic quartz sand, calcium carbonate powder, or glass microspheres are first selected as the substrate. These materials have good chemical stability and physical properties, making them suitable for simulating porous media. At least two different particle sizes are separated by sieving, for example, "180~200 mesh" is used for the low-permeability layer and "100~120 mesh" is used for the high-permeability layer, ensuring that different particle sizes correspond to different homogeneous parts.

[0031] Furthermore, according to the set mass percentage (e.g., 1%~15%), epoxy resin is added as a binder to particles of different sizes. A human-machine cross-mixing method is used to mix for 10~30 minutes until the particles are free of agglomerates and are mixed evenly to ensure the bonding effect.

[0032] Furthermore, the mixed particles are laid layer by layer in the mold from low-permeability layer to high-permeability layer, pushed into the press and the pressing parameters are set. After holding the pressure for ≥10 minutes, the pressure is released to ensure that the interlayer interface is continuous and the fluid can flow in both directions. The pressed medium is then dried and drilled according to the set pore volume to create clear high and low permeability regions in the radial direction, thereby obtaining a heterogeneous porous medium sample.

[0033] In the above process, this embodiment of the invention prepares a heterogeneous porous medium sample with a clear permeability gradient by precisely selecting the substrate, particle size separation, and cementation mixing technology. This step provides a realistic and controllable experimental environment for subsequent seepage experiments, ensuring the accuracy and reliability of the experimental results.

[0034] Step 120: Calibrate the imaging parameters of the low-field nuclear magnetic resonance device according to the permeability difference of the sample, and set the weighting method.

[0035] Nuclear magnetic resonance imaging is used to visualize the seepage characteristics of foam in the high and low permeability layers of the sample.

[0036] In one possible implementation, the center frequency, automatic homogenization field parameters, and pulse duration of the low-field NMR device are calibrated using standard samples to ensure the imaging resolution meets the set requirements. The field of view, imaging orientation, and number of slices of the low-field NMR device are adjusted according to the sample size. When the permeability difference is less than the set value, [further details are needed]. Weighted imaging extends the resampling waiting time and echo time. When the permeability difference is greater than the set value, proton density-weighted imaging is used to extend the resampling waiting time and shorten the echo time.

[0037] Specifically, the low-field nuclear magnetic resonance (LF-NMR) equipment is turned on for preheating. A standard sample (such as a water sample with a known relaxation time) is placed in the center of the holder. The center frequency and 90° / 180° radio frequency pulse width are automatically calibrated by the analysis software to ensure that the equipment is in optimal working condition.

[0038] Furthermore, based on the permeability differences of the samples, test parameters such as echo time (TE), delay time (TW), number of echoes (NECH), and number of scans (NS) are set; for example, TW = 1000~3000ms, TE = 5~20ms, NECH = 500~2000ms, and NS = 32~64 scans are set to compensate for the weak signal in the low-permeability area.

[0039] Furthermore, the center frequency, automatic homogenization field parameters, and pulse duration of the low-field NMR equipment were calibrated using standard samples to ensure an imaging resolution ≥0.1 mm. Based on the permeability differences of the samples, [the appropriate parameters were selected]. Weighted imaging or proton density-weighted imaging is used, and the resampling wait time (TR) and echo time (TE) are adjusted to amplify the signal differences between high and low permeability layers or to prevent the signal of low permeability layer from being masked.

[0040] In the above process, the embodiments of the present invention ensure the accuracy and stability of the low-field nuclear magnetic resonance equipment when testing heterogeneous porous media through precise equipment calibration and parameter settings. This step provides reliable technical support for subsequent spectral testing and imaging, improving the quality and reliability of the data.

[0041] Step 130: Perform foam impregnation on the sample according to the set injection parameters, and obtain the sample's concentration based on the test parameters when injecting the set amount of foam. The spectrum is obtained, and the samples are acquired using a low-field nuclear magnetic resonance device for nuclear magnetic imaging based on imaging parameters and weighting methods.

[0042] In one possible implementation, the sample is dried and vacuum-treated to saturate simulated formation water, and a baseline image of the sample at this point is obtained using a low-field nuclear magnetic resonance (NMR) device. Spectroscopy and baseline NMR imaging; foam preparation and injection into the sample according to set injection parameters, stopping after each set volume is injected, and acquiring the sample using a low-field NMR device. The sample was cleaned after spectral and nuclear magnetic imaging continued until the injection pressure stabilized.

[0043] in, The spectrum is used to represent the distribution characteristics of foam in different channels of a sample; In one possible implementation, after acquiring MRI images of the sample, the MRI images are uniformly mapped and JET pseudocolor is added, and dynamic seepage data are acquired.

[0044] Among them, dynamic seepage data is used to demonstrate the impact of injection parameters on seepage characteristics; JET pseudo-color is used to enhance the clarity of the gas-liquid interface and intuitively present the seepage distribution characteristics of foam in high and low permeability layers.

[0045] Specifically, heterogeneous core samples were dried in a 110℃ constant temperature oven for 24 hours, then saturated with simulated formation water after vacuum extraction. The baseline spectrum and baseline NMR images of the samples were obtained using a low-field NMR device, serving as benchmark data for subsequent comparisons. A surfactant solution and nitrogen gas were introduced into a foam generator. After the outlet foam half-life stabilized (e.g., ≥30 minutes), foam was injected into the core samples at a set rate (e.g., 1~5 mL / min). After injecting a certain volume (e.g., 0.5 PV) of foam, the displacement system was turned off, and the spectrum and NMR images of the samples were obtained using a low-field NMR device. The inlet pressure was recorded. The experiment was stopped after the injection pressure stabilized to ensure the integrity and accuracy of the data.

[0046] In the above process, the embodiments of the present invention ensured the controllability of the experimental process and the accuracy of the data through rigorous sample pretreatment, foam preparation and injection procedures, as well as dynamic monitoring and data acquisition technology. This step provides rich and reliable data support for subsequent seepage characteristic analysis.

[0047] Step 140, according to The relaxation characteristics of the spectrum are used to divide the small, medium, and large channels using the peak endpoint values, based on... The extent of foam spread is calculated by the peak area of ​​the spectrum, and the foam plugging strength is calculated based on the signal amplitude of the nuclear magnetic resonance imaging.

[0048] In one possible implementation, based on Based on the main peak endpoint of the spectrum, according to The relaxation time divides the channels in the sample into small channels, medium channels, and large channels.

[0049] Furthermore, based on the benchmark The peak area of ​​the spectrum and the sample during foam injection. The formula for calculating the peak area of ​​the spectral spectrum and the foam sweep extent E is as follows: ; in, For samples during foam injection Spectrum The signal amplitude at each sampling point Based on Spectrum The signal amplitude of each sampling point, where n is the total number of sampling points.

[0050] Furthermore, the foam plugging strength is calculated based on the signal amplitude of the baseline MRI acquisition point and the signal amplitude of the MRI acquisition point of the sample during foam injection. The calculation formula is as follows: ; in, Nuclear magnetic imaging of samples during foam injection The signal amplitude at each sampling point For the benchmark MRI The signal amplitude of each sampling point, nh is the total number of sampling points in the high-permeability layer, and nl is the total number of sampling points in the low-permeability layer.

[0051] Specifically, based on the sample The spectral peak characteristics are analyzed, and the pores in the sample are divided into small, medium, and large pores using the peak endpoint values. This step helps to accurately locate the distribution of foam in pores of different scales. Based on the initial condition of 100% water saturation in the core, the water saturation of different pores is calculated by comparing the peak area of ​​the sample during foam flooding with the peak area in the initial state, thus obtaining the foam sweep efficiency, an indicator reflecting the diffusion capacity of foam in porous media. The sealing strength of foam on the high-permeability layer is calculated based on the gas saturation of high and low permeability layers. The sealing effect is quantified by comparing the signal amplitude of the sample's NMR imaging acquisition points during foam flooding with the signal amplitude of the baseline NMR imaging acquisition points. This indicator reflects the foam's ability to prevent fluid cross-flow.

[0052] In the above process, the embodiments of the present invention achieve precise quantification and analysis of the foam seepage characteristics in heterogeneous porous media through techniques such as pore segmentation, sweep efficiency evaluation, and plugging effect evaluation. This step provides effective data support and theoretical basis for studying multiphase seepage mechanisms and optimizing enhanced oil recovery technologies.

[0053] Through the above process, this invention achieves effective identification and quantitative characterization of fluid dynamics in foam within different permeability zones and pore sizes by means of sample preparation, equipment calibration and parameter setting, foam flooding treatment and data acquisition, and seepage characteristic analysis and evaluation. This method significantly improves the ability to identify fluid behavior in low-permeability zones and pores of different sizes, providing an effective means for optimizing oilfield foam flooding parameters and evaluating the remediation effects of soil organic pollution.

[0054] In an exemplary embodiment, the method for testing the foam seepage characteristics of heterogeneous porous media of the present invention is shown to investigate the influence of injection parameters on the foam seepage characteristics of heterogeneous porous media (permeability difference 8:1, high permeability layer 3.274 μm², low permeability layer 0.416 μm²). The specific experimental parameters are shown in Table 1 below.

[0055] Table 1 Experimental Parameter Table

[0056] Specifically, it may include the following steps: Step S1: Preparation of bilayer heterogeneous porous media.

[0057] Specifically, non-magnetic quartz sand was selected as the substrate, and particles of two different sizes, "180-200 mesh" and "100-120 mesh," were separated using a sieve to represent the low-permeability layer and the high-permeability layer, respectively. After cleaning and drying the particles, epoxy resin was added as a binder at a mass percentage of 5%, and the mixture was stirred manually and mechanically for 20 minutes until homogeneous. The mixed particles were then laid layer by layer in a mold from the low-permeability layer to the high-permeability layer, and pressed into a press for 15 minutes before being released to ensure continuous interlayer interfaces. The pressed medium was then baked, and columnar solids were drilled around the boundary lines to form a heterogeneous porous medium sample with clearly defined high and low permeability regions in the radial direction, with a designed pore volume of 15 mL.

[0058] Furthermore, by precisely controlling the particle size, binder ratio, and pressing parameters, the permeability difference of the samples was ensured to reach the expected 8:1, with the high permeability layer having a permeability of 3.274 μm² and the low permeability layer having a permeability of 0.416 μm².

[0059] In the above process, the embodiments of the present invention successfully prepared heterogeneous porous media samples with clear permeability differences through precise raw material screening, cementation mixing and layer pressing techniques, providing a reliable basis for subsequent experiments.

[0060] Step S2: Spectrum test parameter settings and testing.

[0061] Specifically, the LF-NMR instrument was preheated, and the standard water sample was placed in the center of the holder. The center frequency and 90° / 180° radio frequency pulse width were automatically calibrated using the analysis software. Based on the permeability differences of the samples, the echo time (TE) was set to 10ms, the delay time (TW) to 2000ms, the number of echoes (NECH) to 1000, and the number of scans (NS) to 48, in order to compensate for the weak signal in the low-permeability region.

[0062] Furthermore, the core sample was placed in a holder, and CPMG sequence testing was performed. Inversion parameters were set on the acquired signals to obtain the heterogeneous core. Spectrum. Through analysis The spectrum can identify the distribution of foam in different channels.

[0063] In the above process, the embodiments of the present invention ensured the accuracy of test parameters by optimizing the test parameters. The accuracy and reliability of the spectral tests provide precise data support for subsequent analysis.

[0064] Step S3: Core NMR imaging test parameter setting and imaging.

[0065] Specifically, the center frequency, automatic homogenization field parameters, and 90° / 180° pulse duration of the low-field NMR equipment were calibrated using standard samples to ensure an imaging resolution of 0.1 mm. Due to the large permeability difference between the samples (8:1), proton density-weighted imaging was used, with the repeat sampling wait time (TR) set to 1500 ms and the echo time (TE) set to 6 ms to avoid masking the signal from the low-permeability layer.

[0066] Furthermore, the field of view was adjusted to 80mm × 25mm to match the size of the columnar core, and coronal single-layer imaging was performed to acquire grayscale images. The images were then uniformly mapped, and JET pseudocolor was added to make the gas-liquid interface clearer.

[0067] In the above process, the embodiments of the present invention successfully obtained clear seepage characteristic images of foam in high and low permeability layers by optimizing imaging parameters and weighting methods, providing intuitive visual basis for subsequent analysis.

[0068] Step S4: Foam seepage test procedure and data acquisition.

[0069] Specifically, heterogeneous core samples were dried in a 110°C constant temperature oven for 24 hours, then saturated with simulated formation water after vacuum extraction, and initial tests were performed. Spectroscopy and nuclear magnetic resonance imaging were used as reference data. A surfactant solution (concentration 0.5wt%) and nitrogen gas were introduced into the foam generator. After the outlet foam half-life stabilized (≥30 minutes), the core sample was injected at a rate of 1.0 mL / min.

[0070] Furthermore, after injecting 0.5 PV of foam, the displacement system was turned off, and the test was conducted. Spectroscopic and coronal imaging was performed to record the inlet pressure. After the injection pressure stabilized, the experiment was stopped, a certain volume of isopropanol was injected to eliminate residual foam, and then purified water was injected to wash the core sample.

[0071] like Figure 4 As shown, this presents the samples collected during the foam injection process into heterogeneous sandstone cores. Spectral line changes. Core samples were collected in stages during the experiment. Spectral lines were analyzed to observe the effect of foam injection on fluid distribution within the core. Furthermore, by comparing different stages... Spectral analysis revealed that the injection of foam significantly altered the fluid flow within the core. The spectral relaxation time distribution reflects the distribution of foam in different channels and its trend over time. Specifically, foam preferentially enters larger channels and gradually expands into smaller channels; this process... The spectral lines clearly show this. This is of great significance for a deeper understanding of the permeation behavior of foam in heterogeneous porous media.

[0072] like Figure 5 The image shows nuclear magnetic resonance (NMR) images acquired during foam injection into heterogeneous sandstone cores. Proton density-weighted imaging was employed to obtain clear images. Furthermore, by adjusting imaging parameters such as resampling time and echo time, the seepage characteristics of foam in high- and low-permeability layers were successfully captured. The foam distribution was denser in the high-permeability layer and relatively sparser in the low-permeability layer. This imaging result not only visually demonstrates the foam seepage path but also provides strong evidence for evaluating the foam's sealing effect and sweep efficiency.

[0073] In the above process, the embodiments of the present invention successfully obtained seepage characteristic data of foam under different injection parameters through rigorous experimental procedures and data acquisition methods, providing rich experimental basis for subsequent analysis; through analysis The position and amplitude variations of the main peak in the spectrum provide a direct visual representation of the foam's distribution in different pores and its trend over time. This is crucial for understanding the seepage behavior of foam in heterogeneous porous media. Proton density-weighted imaging clearly demonstrates the seepage characteristics of foam in high and low permeability layers, with distinct gas-liquid interfaces and a clear understanding of foam distribution and flow. This provides a direct visual basis for evaluating the plugging effect and sweep efficiency of foam.

[0074] Step S5: Seepage characteristic analysis and evaluation.

[0075] Specifically, according to The spectral peak characteristics were analyzed, and the pores in the sample were divided into small, medium, and large pores using the peak endpoint values. Based on the initial condition that the core water saturation was 100%, the water saturation of different pores was calculated by comparing the peak area of ​​the sample during foam flooding with the peak area in the initial state, thus obtaining the degree of foam sweep.

[0076] like Figure 3 As shown, the method for classifying different types of pores in heterogeneous sandstone cores is illustrated in detail. In this invention, low-field nuclear magnetic resonance (LF-NMR) technology was first used to obtain the core pores. Spectrum. Further, through analysis... The main peak characteristics of the spectrum determined the basis for pore channel division: that is, based on the heterogeneous core. The peak endpoint values ​​of the spectrum are used to precisely classify the channels into three categories: small channels, medium channels, and large channels. Among them, small channels correspond to lower... The relaxation time range corresponds to a higher relaxation time for larger channels. The relaxation time range is defined as small, while medium-sized channels fall between the two. This classification method is not only scientifically effective but also provides an important foundation for subsequent analysis of the seepage characteristics of foam in different channels. Based on the T2 spectrum distribution characteristics of high- and low-permeability homogeneous cores, the channel range in heterogeneous cores was classified into three types using the endpoint values ​​of the main peak (the signal peak with the highest amplitude). The classification method is as follows: small channels... Central channel large duct .

[0077] Furthermore, based on the gas saturation of the high and low permeability layers, the plugging strength of the foam on the high permeability layer was calculated. The plugging effect was quantified by comparing the signal amplitudes of the sample at the NMR imaging acquisition points and the baseline NMR imaging acquisition points during the foam displacement process.

[0078] like Figures 6 to 8 As shown, Figures 6 to 8The study illustrates the changes in sweep efficiency (SQE) for large, medium, and small channels under different injection parameters. During the experiment, parameters such as foam injection rate, gas-liquid ratio, and surfactant concentration were systematically varied to investigate their impact on foam SQE. Furthermore, by comparing the SQE diagrams under different parameters, it was found that increasing the foam injection rate significantly improved the SQE of large and medium channels, but had a smaller impact on the SQE of small channels. Specifically, increasing the gas-liquid ratio had a positive impact on the SQE of medium and small channels, while changes in surfactant concentration had a complex effect on the SQE of all channels. These findings not only quantify the impact of injection parameters on foam seepage characteristics but also provide important guidance for optimizing foam flooding parameters and improving oil recovery.

[0079] In the above process, the embodiments of the present invention, through techniques such as pore segmentation, sweep efficiency evaluation, and plugging effect evaluation, achieved precise quantification and analysis of foam seepage characteristics in heterogeneous porous media, providing effective data support and theoretical basis for studying multiphase seepage mechanisms and optimizing oil recovery technologies. By comparing the sweep efficiency of different pores under different injection parameters, and the sweep efficiency of foam in small, medium, and large pores, the influence of injection parameters on foam seepage characteristics was quantified. This has important guiding significance for optimizing foam drive parameters and improving oil recovery. Comparing the plugging strength of foam in high-permeability layers under different injection parameters provides important data support for understanding the ability of foam to prevent fluid channeling.

[0080] like Figure 2 As shown, the plugging effect of different experimental schemes (injection parameters) is demonstrated. It can be seen that experimental scheme 2 has the best effect, that is, the faster the injection efficiency, the higher the plugging strength; followed by experimental scheme 4, that is, the lower the concentration of surfactant, the higher the plugging strength; and then experimental scheme 1, that is, the smaller the gas-liquid ratio, the higher the plugging strength.

[0081] Through the above process, this embodiment successfully obtained foam seepage characteristic data under different injection parameters. By dividing the pores, evaluating the sweep efficiency, and evaluating the plugging effect, it achieved accurate quantification and analysis of foam seepage characteristics. This not only improved the ability to identify fluid behavior in low-permeability areas and pores of different sizes, but also provided effective data support and theoretical basis for the optimization of foam drive parameters, and has broad application prospects and practical value.

[0082] The following are embodiments of the apparatus of the present invention, which can be used to perform the test method for the seepage characteristics of heterogeneous porous media foam involved in the present invention. For details not disclosed in the embodiments of the apparatus of the present invention, please refer to the method embodiments of the test method for the seepage characteristics of heterogeneous porous media foam involved in the present invention.

[0083] Please see Figure 9This invention provides a testing device 800 for testing the seepage characteristics of non-homogeneous porous media foam.

[0084] The testing device 800 for the foam seepage characteristics of heterogeneous porous media includes, but is not limited to: a sample preparation and parameter setting module 810, an NMR imaging parameter optimization module 830, a foam seepage testing module 850, and a foam seepage effect evaluation module 870.

[0085] The sample preparation and parameter setting module 810 is used to prepare heterogeneous porous media samples with a clear permeability difference, preheat the low-field nuclear magnetic resonance equipment and calibrate its basic parameters, and set test parameters according to the permeability difference of the samples.

[0086] The nuclear magnetic resonance imaging parameter optimization module 830 is used to calibrate the imaging parameters of the low-field nuclear magnetic resonance device according to the permeability difference of the sample and set the weighting method; nuclear magnetic resonance imaging is used to present the seepage characteristics of foam in the high and low permeability layers of the sample.

[0087] The foam permeation test module 850 is used to perform foam flooding treatment on samples according to set injection parameters, and obtain the sample's permeation rate based on the test parameters when the set amount of foam is injected. The spectrum is obtained, and the samples are acquired using a low-field nuclear magnetic resonance device for nuclear magnetic imaging based on imaging parameters and weighting methods.

[0088] The foam seepage effect evaluation module 870 is used to evaluate the foam seepage effect based on... The relaxation characteristics of the spectrum are used to divide the small, medium, and large channels using the peak endpoint values, based on... The extent of foam spread is calculated by the peak area of ​​the spectrum, and the foam plugging strength is calculated based on the signal amplitude of the nuclear magnetic resonance imaging.

[0089] It should be noted that the above embodiments of testing the seepage characteristics of heterogeneous porous media foam are only illustrated by the division of the above functional modules. In actual applications, the above functions can be assigned to different functional modules as needed. That is, the internal structure of the testing device for the seepage characteristics of heterogeneous porous media foam will be divided into different functional modules to complete all or part of the functions described above.

[0090] Furthermore, the test apparatus for the seepage characteristics of heterogeneous porous media foam provided in the above embodiments and the test method for the seepage characteristics of heterogeneous porous media foam belong to the same concept. The specific way in which each module performs its operation has been described in detail in the method embodiments, and will not be repeated here.

[0091] Compared with related technologies, the beneficial effects of the present invention are: 1. This invention can accurately simulate the foam seepage behavior in heterogeneous porous media; by preparing a double-layer heterogeneous porous media sample with a clear permeability difference, and combining the three-dimensional imaging and non-destructive testing characteristics of low-field nuclear magnetic resonance (LF-NMR) technology, the three-dimensional pore structure and dynamic foam seepage process inside the heterogeneous porous media (such as oil reservoir rocks) are realistically reproduced, solving the problem that traditional two-dimensional models cannot accurately simulate the real environment.

[0092] 2. This invention significantly improves the ability to identify fluid behavior in low-permeability areas; it establishes a pore structure classification method based on NMR relaxation characteristics, utilizing... The main peak characteristics of the spectrum are used to classify small, medium and large pores. Combined with the special parameter settings for heterogeneous porous media (such as adjusting echo time and delay time), the problem of weak signal in low-permeability areas is effectively compensated, and the dynamics of fluid in pores of different scales can be accurately identified and quantitatively characterized.

[0093] 3. This invention can quantitatively evaluate the plugging strength and sweep efficiency of foam in heterogeneous porous media. By combining the gas saturation of high and low permeability layers with the amplitude variation of NMR imaging signals, a quantitative evaluation system for foam seepage characteristics based on NMR is formed. This system not only considers the interlayer differences in heterogeneous media, but also correlates macroscopic seepage characteristics with microscopic pore-scale behavior through specific calculation formulas (such as sweep efficiency and plugging strength formulas), providing an effective means for studying multiphase seepage mechanisms.

[0094] 4. This invention has practical value in optimizing foam flooding parameters and improving oil recovery. The effectiveness of the method was verified through multiple experiments in the implementation case (such as changing surfactant concentration, foam injection rate, gas-liquid ratio, etc.). Experimental results show that this method can quantify the foam seepage characteristics (such as sweep efficiency and plugging effect) under different parameters, providing a scientific basis for parameter optimization and thus helping to improve efficiency.

[0095] 5. This invention has broad application prospects and environmental benefits; the method is applicable to fields such as oilfield foam flooding development, soil organic pollution remediation, groundwater pollution seepage prevention, and underground engineering grouting. By accurately simulating and quantitatively analyzing foam seepage behavior in heterogeneous porous media, it helps to solve environmental pollution problems more efficiently, while reducing the amount of traditional chemical flooding agents used, thus reducing negative environmental impacts and demonstrating good environmental benefits.

[0096] It should be understood that although the steps in the flowcharts of the accompanying figures are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the accompanying figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0097] The above description is only a partial embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A test method for the seepage characteristics of heterogeneous porous media foam, characterized in that, The method includes: Heterogeneous porous media samples with a clear permeability gradient were prepared. The low-field nuclear magnetic resonance equipment was preheated and its basic parameters were calibrated. The test parameters were set according to the permeability gradient of the samples. The imaging parameters of the low-field nuclear magnetic resonance (NMR) device are calibrated according to the permeability difference of the sample, and the weighting method is set; the NMR imaging is used to present the seepage characteristics of foam in the high and low permeability layers of the sample; The sample is subjected to foam impregnation treatment according to the set injection parameters, and the sample is obtained according to the test parameters when the set amount of foam is injected. The spectrum is obtained, and the nuclear magnetic resonance imaging of the sample is acquired through the low-field nuclear magnetic resonance device according to the imaging parameters and weighting method; According to the above The relaxation characteristics of the spectrum are used to divide the channels into small, medium, and large channels using the peak endpoint values. The extent of foam spread is calculated based on the peak area of ​​the spectrum, and the foam sealing strength is calculated based on the signal amplitude of the nuclear magnetic resonance imaging.

2. The test method for the seepage characteristics of heterogeneous porous media foam as described in claim 1, characterized in that, The preparation of heterogeneous porous media samples with clearly defined permeability gradients includes: Non-magnetic quartz sand, calcium carbonate powder, or glass microspheres are selected as the substrate, and at least two different particle sizes are separated by sieving, followed by washing and drying; the different particle sizes correspond to different homogeneous fractions. Epoxy resin binder is added to the particles according to the set mass percentage and stirred until uniformly mixed. The mixed particles are then laid in a mold layer by layer from low permeability layer to high permeability layer and pressed to obtain the initial sample. The initial sample is baked and drilled according to a set pore volume, so that there are high and low permeability regions in the radial direction of the initial sample that meet the set requirements, resulting in a heterogeneous porous medium sample.

3. The test method for the seepage characteristics of heterogeneous porous media foam as described in claim 1, characterized in that, The preheating and basic parameter calibration of the low-field NMR equipment, and the setting of test parameters according to the permeability differences of the samples, include: Start the low-field NMR equipment to preheat, and calibrate the center frequency and radio frequency pulse width of the low-field NMR equipment based on a water sample with a known relaxation time. Test parameters are set according to the permeability differences of the samples; the test parameters include echo time, delay time, and number of scans; the number of scans is set to compensate for weak signals in low-permeability areas.

4. The test method for the seepage characteristics of heterogeneous porous media foam as described in claim 1, characterized in that, The step of calibrating the imaging parameters of the low-field nuclear magnetic resonance device based on the permeability difference of the samples and setting the weighting method includes: The center frequency, automatic homogenization field parameters and pulse duration of the low-field nuclear magnetic resonance equipment are calibrated using standard samples to ensure that the imaging resolution meets the set requirements. The field of view, imaging orientation and number of slices of the low-field nuclear magnetic resonance equipment are adjusted according to the size of the sample. When the permeability difference is less than the set value, use Weighted imaging extends the resampling waiting time and echo time. When the permeability difference is greater than the set value, proton density-weighted imaging is used to extend the resampling waiting time and shorten the echo time.

5. The test method for the seepage characteristics of heterogeneous porous media foam as described in claim 1, characterized in that, The sample is subjected to foam impregnation treatment according to the set injection parameters, and the sample is obtained according to the test parameters when the set amount of foam is injected. The spectrum, acquired by the low-field nuclear magnetic resonance device according to the imaging parameters and weighting method, includes: After drying and vacuuming the sample, it was saturated with simulated formation water. A baseline image of the sample at this point was then obtained using the low-field nuclear magnetic resonance (NMR) equipment. Spectroscopy and benchmark MRI; The spectrum is used to represent the distribution characteristics of foam in different channels of the sample; Foam is prepared and injected into the sample according to set injection parameters, stopping after each set volume is injected. The sample is then acquired using the low-field nuclear magnetic resonance (NMR) device. The sample was cleaned after spectral and nuclear magnetic resonance imaging until the injection pressure stabilized.

6. The test method for the seepage characteristics of heterogeneous porous media foam as described in claim 5, characterized in that, After acquiring the MRI image of the sample, the method further includes: The nuclear magnetic resonance imaging is uniformly mapped and JET pseudocolor is added, and dynamic seepage data is collected; the dynamic seepage data is used to show the influence of injection parameters on seepage characteristics; the JET pseudocolor is used to enhance the clarity of the gas-liquid interface and intuitively present the seepage distribution characteristics of foam in high and low permeability layers.

7. The test method for the seepage characteristics of heterogeneous porous media foam as described in claim 5, characterized in that, According to the The relaxation characteristics of the spectrum are used to divide the channels into small, medium, and large channels using the peak endpoint values, including: Based on the aforementioned benchmark Based on the main peak endpoint of the spectrum, according to The relaxation time divides the channels in the sample into small channels, medium channels, and large channels.

8. The test method for the seepage characteristics of heterogeneous porous media foam as described in claim 5, characterized in that, According to the The calculation of the foam's spread based on the spectral peak area includes: According to the benchmark The peak area of ​​the spectrum and the sample during foam injection. The formula for calculating the peak area of ​​the spectral spectrum and the foam sweep extent E is as follows: ； in, For the sample during foam injection Spectrum The signal amplitude at each sampling point For the benchmark Spectrum The signal amplitude of each sampling point, where n is the total number of sampling points.

9. The test method for the seepage characteristics of heterogeneous porous media foam as described in claim 1, characterized in that, The calculation of foam plugging strength based on the signal amplitude of the nuclear magnetic resonance imaging includes: The foam plugging strength is calculated based on the signal amplitude of the reference MRI acquisition point and the signal amplitude of the sample's MRI acquisition point during foam injection. The calculation formula is as follows: ； in, For the first nuclear magnetic resonance imaging of the sample during foam injection. The signal amplitude at each sampling point For the reference MRI, the first The signal amplitude of each sampling point, nh is the total number of sampling points in the high-permeability layer, and nl is the total number of sampling points in the low-permeability layer.

10. A testing device for the seepage characteristics of heterogeneous porous media foam, characterized in that, The device includes: The sample preparation and parameter setting module is used to prepare heterogeneous porous media samples with a clear permeability difference, preheat the low-field nuclear magnetic resonance equipment and calibrate its basic parameters, and set test parameters according to the permeability difference of the sample. The nuclear magnetic resonance imaging parameter optimization module is used to calibrate the imaging parameters of the low-field nuclear magnetic resonance device according to the permeability difference of the sample, and to set the weighting method; the nuclear magnetic resonance imaging is used to present the seepage characteristics of foam in the high and low permeability layers of the sample; The foam permeation test module is used to perform foam flooding treatment on the sample according to set injection parameters, and to obtain the sample's permeation rate based on the test parameters when the set amount of foam is injected. The spectrum is obtained, and the nuclear magnetic resonance imaging of the sample is acquired through the low-field nuclear magnetic resonance device according to the imaging parameters and weighting method; The foam seepage effect evaluation module is used to evaluate the foam seepage effect based on the following: The relaxation characteristics of the spectrum are used to divide the channels into small, medium, and large channels using the peak endpoint values. The extent of foam spread is calculated based on the peak area of ​​the spectrum, and the foam sealing strength is calculated based on the signal amplitude of the nuclear magnetic resonance imaging.

Images