Microscopic percolation model preparation method

Abstract

The application provides a preparation method of a micro seepage model, comprising the following steps: a) sequentially performing surface cleaning, laser engraving and channel cleaning on a PMMA base material to obtain a micro seepage model bottom plate; b) performing mineral cementation on the surface of pores of the micro seepage model bottom plate obtained in step a) by using a mineral cementing agent, and finally performing model packaging by using a packaging adhesive to obtain a micro seepage model; the mineral cementing agent is prepared from raw materials comprising the following components: 8-15 parts by weight of MMA powder; 3-10 parts by weight of alpha-cyanoethyl acrylate; 50-80 parts by weight of dichloromethane; and 3-10 parts by weight of p-methylbenzenesulfonic acid. Compared with the prior art, the preparation method provided by the application jointly cements the acrylic seepage model by physical and chemical processes, can realize high-strength integrated cementation between the bottom plate and the cover plate, has strong complete transparency and visibility and has no seepage influence, and meanwhile, the preparation method has a small influence on the pore geometry.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, and more specifically, to a method for preparing a microscopic permeation model. Background Technology

[0002] Microscopic flow modeling technology involves etching pre-designed pores and flow channels onto a substrate, followed by bonding and encapsulation processes. This technology is used in environmental monitoring, biopharmaceuticals, and medical testing, and is particularly important in oil and gas field development. To better understand the reservoir characteristics and fluid flow patterns of oil reservoirs, scholars both domestically and internationally have proposed various microscopic physical flow models for laboratory experimental research, including real core sections, glass etching models, and acrylic etching models. (1) The real core model is mainly made of real core thin slices cast with epoxy resin or encapsulated with materials such as glass and organic polymers as clamps. It can simulate the seepage law and the oil-water-rock reaction mechanism. Usually, the core thin slices are bonded to the substrate by bonding the upper cover plate, core thin slices and lower cover plate in sequence, and then the surrounding area is sealed with adhesive. In this manufacturing method, the adhesive is easy to penetrate into the pores and block the core pores, affecting the study of seepage law in the pores. At the same time, in the displacement experiment, dyes are usually used to dye water and oil. However, due to the poor light transmittance of the real core, even with the above auxiliary operations, it is still difficult to observe the fluid distribution and transport state in the pores. (2) Glass etching models are usually made by acid etching or photolithography. The glass with etching channels and the glass cover plate are bonded together by heating or applying liquid adhesive. Glass etching models are generally used to simulate the seepage law and mechanism in sandstone reservoirs, but it is difficult to simulate the seepage law in carbonate reservoirs. Although glass etching models have good observability, the sintering method requires high control. High temperature causes the channels to melt and block, and the controllable width of the channels is low. The liquid adhesive bonding method is affected by the thickness of the adhesive coating, and usually the phenomenon of thinner top and thicker bottom is observed, which affects the bonding effect. At the same time, liquid adhesive is easy to block the etching channels, which affects the study of seepage law. (3) Acrylic etching model uses organic polymer acrylic material as substrate. The pre-designed simulated channels are etched on the surface of the substrate by laser. Then, the model is encapsulated and bonded with a cover plate. Common methods include hot pressing encapsulation and adhesive encapsulation. Hot pressing encapsulation requires high temperature and high pressure, which can easily lead to deformation and blockage of the seepage channels. During adhesive encapsulation, the adhesive is easily embedded in the microchannels and has poor chemical heat resistance. The adhesive is easily soluble in oil, which can not only block the channels but also cause the etching model to fail and leak. At the same time, the surface of acrylic material is oleophilic. Although it can simulate the wettability of carbonate rock reservoirs, it cannot study its reaction mechanism.

[0003] Chinese patent CN106338889A discloses a method for preparing a microscopic visual etching low-permeability model. The main steps of the preparation process of the microscopic pore etching model are to expose a glass slide coated with photoresist to transfer the designed pattern to the glass slide coated with photoresist, and then obtain the microscopic pore model through development, etching, and photoresist removal processes. The specific steps are as follows: (1) Cleaning process. Boil a mixture of H2O2:H2SO4 with a mass ratio of 2.5:7.5, and clean the surface impurities with tap water, alcohol, and distilled water; then dry. (2) Photolithography process. Adsorb the glass slide on a rotating stage, apply the base film liquid to the glass slide, spread it evenly, bake it, spin-coat the photoresist, and then bake it again to fix the photoresist; transfer the drawn pattern to the glass slide coated with photoresist through exposure, and after exposure, place the glass slide in the developing solution and develop for 5 minutes to dissolve the photoresist in the exposed area and reveal the photolithography part. (3) Acid etching process. The photolithographically etched glass slide is placed on a baking tray to fix the adhesive. Uncoated portions are sealed with wax and then acid-etched using a 40% hydrofluoric acid and ammonium fluoride buffer solution. The wax on the glass slide surface is scraped off with a blade, and the slide is placed in a desizing solution for desizing, followed by repeated cleaning with alcohol and distilled water. The preparation is complete. However, this technique uses a 40% hydrofluoric acid and ammonium fluoride buffer solution to etch pore channels into the glass surface. The longer the acid etching process, the larger the pores; the shorter the time, the smaller the pores. Therefore, the depth and width of the pores cannot be precisely controlled, affecting not only the repeatability of the experiment but also the results of seepage patterns in real core samples. This makes it difficult to distinguish between different phases under a microscope during displacement experiments, especially when multiphase fluids are flowing, thus preventing accurate observation of fluid flow characteristics. Furthermore, this technique uses glass as the substrate. Since the main component of glass is silicon dioxide, which is water-wettable, it can only simulate sandstone reservoirs and not oil-wet carbonate reservoirs.

[0004] Chinese patent CN 109827822A discloses a high-temperature and high-pressure visualized real rock seepage model and its manufacturing method. The manufacturing process is mainly divided into four parts: bonding one side of the rock sheet, building the inlet channel and the dam, bonding the other side of the rock sheet, and injection molding. (1) Bonding one side of the rock sheet. Grind the treated rock sheet flat, and then use an adhesive to evenly bond the flattened side to the glass plate, and open the fluid inlet and fluid outlet. (2) Building the inlet channel and the dam. Use an adhesive to build inlet channels around the two short sides of the rock sheet, and grind the rock sheet and the dam at the same time. (3) Bonding the other side of the rock sheet. Bond the other side of the rock sheet to the center of the second glass plate. (4) Injection molding. Fill the area between the two glass plates and the two ends of the rock sheet with adhesive, and the preparation is completed after curing. However, this technology uses a potting molding method for encapsulation. During the potting process, the glue can easily seep into the pores, causing pore blockage and affecting the oil and water seepage process within the pores. At the same time, although this technology uses core thin sections for simulation, which provides visibility, the disordered internal channels and poor light transmittance make it difficult to observe experimental phenomena.

[0005] In summary, there is currently no effective method for preparing a microscopic seepage model that can simulate the seepage law and mechanism of oil reservoirs without affecting the structure and function of the microflow channels. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for preparing a microscopic seepage model. The preparation method provided by the present invention uses physical and chemical processes to bond the acrylic seepage model, which can achieve a high-strength integral bonding between the base plate and the cover plate, and is completely transparent with strong visibility and no leakage. At the same time, the preparation method has little impact on the pore geometry.

[0007] This invention provides a method for preparing a microscopic seepage model, comprising the following steps:

[0008] a) The PMMA substrate is sequentially cleaned, laser-engraved, and cleaned to obtain a micro-permeation model base plate;

[0009] b) The micro-flow model base plate obtained in step a) is mineral cemented with mineral cement on the pore surface, and finally the model is encapsulated with encapsulating adhesive to obtain the micro-flow model;

[0010] The mineral binder is prepared from raw materials comprising the following components:

[0011] 8-15 parts by weight of PMMA powder;

[0012] 3-10 parts by weight of ethyl α-cyanoacrylate;

[0013] 50-80 parts by weight of dichloromethane;

[0014] 3-10 parts by weight of p-toluenesulfonic acid.

[0015] This invention provides a novel method for preparing and applying a micro-seepage model, including the design of a micro-seepage model that can simulate the oil-water-rock coupling mechanism, and the technical content of the formulation design of the surface mineral binder and encapsulating adhesive used therein.

[0016] In this invention, the surface cleaning process described in step a) is preferably as follows:

[0017] The PMMA substrate was ultrasonically cleaned with alcohol and deionized water 2-4 times each, for 4-6 minutes each time; then dried at room temperature.

[0018] In this invention, the laser engraving process described in step a) is preferably as follows:

[0019] a1) Wax sealing: Place the dried substrate sheet on the rotating table of the spin coater, set the temperature to 60℃~70℃, use the dropper to apply molten paraffin wax to the surface of the substrate, so that the entire surface of the substrate is covered, turn on the spin coater to spread the paraffin wax evenly, then remove the substrate and cool it at room temperature, so that the paraffin wax adheres to the substrate sheet to form a smooth, thin wax film with a thickness of less than 1μm.

[0020] a2) Preparation of microscopic pore structure patterns: The pore patterns are taken from scanned images of actual rock core sections, with the porosity of the scanned images ranging from 10% to 30%;

[0021] a3) Processing of the micro model: Using a laser engraving machine, the PMMA substrate is processed according to the prepared geometric pattern of the real rock core pores to obtain the engraved micro seepage model base plate.

[0022] In this invention, the laser power of the laser engraving machine described in step a3) is preferably 35%~40%, and the moving speed is preferably 250mm / min~300mm / min.

[0023] In this invention, the channel cleaning process described in step a) is preferably as follows:

[0024] First, clean the surface of the pores with alcohol and a brush 2-4 times, 4-6 minutes each time; then, ultrasonically clean the PMMA substrate with alcohol and deionized water 2-4 times each, 4-6 minutes each time; dry at room temperature to obtain the micro-permeation model substrate.

[0025] In this invention, the mineral binder described in step b) is prepared from raw materials comprising the following components:

[0026] 8-15 parts by weight of PMMA powder;

[0027] 3-10 parts by weight of ethyl α-cyanoacrylate;

[0028] 50-80 parts by weight of dichloromethane;

[0029] 3-10 parts by weight of p-toluenesulfonic acid;

[0030] Preferably prepared from the following components:

[0031] 8-12 parts by weight of PMMA powder;

[0032] 3-5 parts by weight of ethyl α-cyanoacrylate;

[0033] 60-70 parts by weight of dichloromethane;

[0034] 3-7 parts by weight of p-toluenesulfonic acid.

[0035] In this invention, the preferred method for preparing the mineral cementing agent is as follows:

[0036] PMMA powder, ethyl α-cyanoacrylate, dichloromethane and p-toluenesulfonic acid are mixed and stirred continuously for 1 min to 5 min at a speed of 150 r / min to 250 r / min under air-isolated conditions. After standing, a mineral binder is obtained.

[0037] In this invention, the mineral cementation process on the pore surface described in step b) is preferably as follows:

[0038] Take 0.5 mL to 1 mL of mineral binder and apply it evenly to the pore surface of the micro-percolation model substrate, waiting for 1 to 3 minutes. Use nitrogen to purge the surface pores and remove any residual mineral binder. Then, take nano-CaCO3 powder or nano-SiO2 powder and spray it evenly onto the substrate surface, with a thickness exceeding the pore depth of the substrate by 0.5 mm to 1.5 mm. Place the sprayed substrate into a tablet press and press it at a pressure of 0.5 MPa to 1 MPa, a temperature of 20℃ to 30℃, and a pressing time of 5 to 15 minutes. After removing the substrate, clean the surface and pores of the substrate with alcohol and deionized water to remove any residual mineral powder, cleaning 2 to 4 times each, for 4 to 6 minutes each time. Then, dry at room temperature to complete the surface mineral bonding.

[0039] In this invention, the encapsulating adhesive described in step b) is preferably prepared from raw materials comprising the following components:

[0040] PMMA powder 0.75~4 parts by weight;

[0041] Formic acid 2-4 parts by weight;

[0042] 2-4 parts by weight of methanol;

[0043] 3-10 parts by weight of dichloromethane;

[0044] More preferably, it is prepared from the following components:

[0045] PMMA powder 0.75~1.25 parts by weight;

[0046] Formic acid 2-4 parts by weight;

[0047] 2-4 parts by weight of methanol;

[0048] 3-7 parts by weight of dichloromethane.

[0049] In this invention, the preferred method for preparing the encapsulating adhesive is as follows:

[0050] PMMA powder, formic acid, methanol and dichloromethane are mixed and stirred continuously for 1 min to 5 min at a speed of 150 r / min to 250 r / min under air-isolated conditions. After standing, the encapsulating adhesive is obtained.

[0051] In this invention, the model encapsulation process described in step b) is preferably as follows:

[0052] Wipe away the residual wax layer on the surface of the engraved base plate 2-4 times with alcohol at 40℃~60℃, each time for 4-6 minutes; take 2mL~3mL of encapsulation adhesive and apply it evenly to the surfaces of the cover plate and base plate, let it stand for 2-5 minutes to allow the encapsulation adhesive to fully react with the surfaces of the cover plate and base plate respectively; align and fix the cover plate and base plate, place them in the tablet press, and apply uniform pressure at 0.2MPa~0.7MPa; then immediately place the tablet press in a vacuum drying oven at 10℃. -1 Pa~10 -5 Under vacuum conditions of Pa, the encapsulating adhesive retained in the pores is discharged into the permeation model. The vacuum environment is set at a temperature of 50℃~80℃ for 10min~20min to obtain the micro-permeation model.

[0053] This invention proposes a novel PMMA binder and bonding method that uses both physical and chemical processes to bond an acrylic seepage model. This achieves a high-strength, integrated bond between the base plate and the cover plate, with complete transparency and high visibility, and no leakage. Furthermore, this bonding method has minimal impact on the pore geometry. Specifically:

[0054] (1) Chemical process: This binder controls the bonding effect by adding and reducing reactants to promote and inhibit hydrolysis. Equation (1) is the esterification reaction equation of MMA monomer, which is usually catalyzed by heating with concentrated H2SO4 to accelerate the reaction rate. This reaction process is reversible. MMA monomer is... It is easily hydrolyzed by strong acids. and Therefore, based on this reversible reaction, methanol and a volatile acid (formic acid) are added to the solution to promote the hydrolysis reaction. During the cementation process, formic acid, methanol, and dichloromethane gradually volatilize, and the MMA esterification reaction restarts, thus completing the integrated cementation.

[0055] (1).

[0056] (2) Physical process: Since dichloromethane has a strong solubility for MMA monomers, MMA is dissolved in a mixed solution of dichloromethane, methanol and formic acid. When dichloromethane, methanol and formic acid evaporate, the dissolved MMA solidifies, completing the micro-percolation model cementation.

[0057] Most current seepage models can only study the fluid transport laws within the rock pore system. This invention proposes a novel PMMA surface mineral (nano SiO2 or CaCO3 powder) binder and cementation method, which can solve the problem that micro-seepage models cannot study the oil-water-rock coupling mechanism.

[0058] This binder primarily consists of ethyl α-cyanoacrylate and MMA. Ethyl α-cyanoacrylate is highly sensitive to H₂O and can polymerize rapidly under its catalysis. p-Toluenesulfonic acid is commonly used as a stabilizer in polymerization reactions and as a catalyst, stabilizer, and curing agent in organic synthesis (esters, etc.), exhibiting strong water extraction properties. Adding p-Toluenesulfonic acid to the solution can reduce the polymerization rate of ethyl α-cyanoacrylate, prolong the bonding time with minerals, enhance the bonding effect on mineral powder, and simultaneously reduce the impact of the mineral bonding process on pore depth.

[0059] To address the shortcomings of current microfluidic modeling technology, such as high research thresholds and high costs of related equipment and processing environments, this invention utilizes low-cost PMMA material for engraving and encapsulation. Compared with traditional microfluidic technology, this invention is expected to significantly reduce chip processing costs and the requirements for precision equipment and environments during the processing. Attached Figure Description

[0060] Figure 1 A technical roadmap for the preparation method of the microscopic seepage model provided in the embodiments of the present invention;

[0061] Figure 2 The microscopic seepage model pore pattern in this embodiment of the invention includes (a) a base plate and (b) a cover plate.

[0062] Figure 3 This is a photograph of the base plate after engraving on the PMMA substrate in an embodiment of the present invention.

[0063] Figure 4The following are actual images of the base plate in an embodiment of the present invention, wherein (a) is the base plate without surface minerals, (b) is the base plate during the mineral bonding process, and (c) is the base plate after mineral bonding.

[0064] Figure 5 This is a microscopic image of the cross-section of the micro-permeation model after encapsulation in an embodiment of the present invention;

[0065] Figure 6 This is a schematic diagram of mineral cementation on the pore surface.

[0066] Figure 7 The diagram shows a microscopic seepage model and application examples after saturating crude oil. Detailed Implementation

[0067] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0068] Example

[0069] (1) PMMA surface cleaning:

[0070] PMMA substrate surface cleaning: This process removes as much residual organic contaminants as possible from the PMMA surface. The PMMA substrate was ultrasonically cleaned three times each with alcohol and deionized water, for 5 minutes each time; it was then dried at room temperature.

[0071] (2) Laser engraving:

[0072] ① Wax sealing:

[0073] Place the dried substrate sheet on the rotating table of the spin coater, set the temperature to 65℃, use the dropper to apply molten paraffin wax to the surface of the substrate, ensuring complete coverage, turn on the spin coater to spread the paraffin wax evenly, then remove the substrate and allow it to cool to room temperature, allowing the paraffin wax to adhere to the substrate sheet, forming a smooth, thin wax film with a thickness of less than 1μm.

[0074] ② Preparation of microscopic pore structure patterns:

[0075] The pore patterns were obtained from scanned images of actual core sections. The porosity of the core scan images can range from 10% to 30%. In this experiment, the porosity of the core scan images was approximately 20.37%. Figure 2 As shown.

[0076] ③ Processing of microscopic models:

[0077] A laser engraving machine was used to process PMMA substrates according to the pre-designed geometric pattern of the actual core boreholes. As shown in Table 1, the laser power and engraving speed were adjusted and set; the effect of etching the boreholes was determined by both laser power and movement speed. Based on different design analyses, a movement speed of 250 mm / min and laser power of 35% and 40% could achieve the basic borehole depth requirements. The optimal engraving effect was selected based on a comparison of the final results. Therefore, the preferred engraving parameters for the PMMA board were a laser power of 35% and a movement speed of 250 mm / min. Figure 3 The microscopic permeation model base plate of PMMA material after engraving under these parameters shows the engraved channels on the surface. The channels are evenly distributed, the substrate is flat without melting or burn-through, and the channel depth is about 100μm.

[0078] Table 1. Effects of Laser Power on Engraving Rate

[0079]

[0080] (3) Cleaning of the channel:

[0081] Because the surface is laser-engraved, debris remains on the surface of the etched pores. First, clean the pore surface three times with alcohol and a brush, 5 minutes each time; then, ultrasonically clean the PMMA substrate three times each with alcohol and deionized water, 5 minutes each time; dry at room temperature to remove as many PMMA particles as possible from the surface.

[0082] (4) Mineral cementation on the pore surface:

[0083] ①Preparation of mineral binder:

[0084] PMMA powder, ethyl α-cyanoacrylate, dichloromethane, and p-toluenesulfonic acid were mixed in the proportions shown in Table 2 below. The mixture was stirred continuously at 200 rpm for 3 minutes in the absence of air until fully dissolved, and then allowed to stand. A higher mass fraction of PMMA and a lower mass fraction of dichloromethane resulted in higher viscosity and poorer flowability of the mineral binder; a higher mass fraction of ethyl α-cyanoacrylate resulted in faster bonding; and a higher mass fraction of p-toluenesulfonic acid resulted in lower bonding strength. Preferably, the mass fractions of PMMA, ethyl α-cyanoacrylate, dichloromethane, and p-toluenesulfonic acid were 8-15, 3-10, 50-80, and 3-10, respectively, with the optimal ratio being 10, 5, 65, and 5, achieving the best mineral bonding effect.

[0085] Table 2. Mass proportions of mineral cementing agent solution

[0086]

[0087] ② Surface mineral cementation:

[0088] Take 0.8 mL of the mineral binder solution prepared in step ① above, and apply it evenly to the pore surface of the etched substrate. Wait for 2 minutes. Use nitrogen to purge the surface pores and remove any residual mineral binder. Take nano-CaCO3 powder and spray it evenly onto the surface of the substrate, with a thickness exceeding the pore depth of the substrate by approximately 0.5 mm to 1.5 mm. Place the sprayed substrate into a tablet press, set the pressure to 0.5 MPa to 1 MPa, 25°C, and the pressing time to 5 to 15 minutes. After removing the substrate, clean the surface and pores of the substrate with alcohol and deionized water, respectively, three times each for 5 minutes each time. Then dry at room temperature to complete the surface mineral bonding. If the thickness of the nano-CaCO3 powder is too large or too small, it cannot effectively embed into the pore surface and complete the bonding under the pressure of the tablet press, resulting in a poorer effect. The lower the tablet press pressure, the poorer the embedding effect, while higher pressure can easily cause deformation and damage to the substrate. Therefore, the optimal effect can be achieved by uniformly spraying nano-CaCO3 powder with a thickness exceeding the pore thickness by about 1 mm, applying pressure of 0.7 MPa, at 25°C, and for 10 minutes.

[0089] (5) Preparation of encapsulating adhesive:

[0090] PMMA powder, formic acid, methanol, and dichloromethane were mixed according to the proportions shown in Table 3. The mixture was stirred continuously at 200 rpm for 3 minutes in the absence of air to ensure complete dissolution, and then allowed to stand for later use. Methanol reduces the corrosiveness and solubility of dichloromethane on PMMA, and its volatility during bonding minimizes its impact on the bonding effect. Furthermore, as a reactant, it promotes esterification. Formic acid promotes the hydrolysis of PMMA. A lower mass fraction of dichloromethane results in a weaker physical dissolution effect on the PMMA substrate; a higher mass fraction results in a stronger physical dissolution effect and a greater impact on pore depth. Excessive or insufficient methanol and formic acid content directly affects the chemical solubility of MMA. Therefore, the preferred mass fractions of PMMA powder, formic acid, methanol, and dichloromethane are 0.75–4, 2–4, 2–4, and 3–10, with the optimal ratio of 1, 3, 3, and 5 achieving the best results and having almost no impact on pore depth.

[0091] Table 3 Adhesive mass parts ratio

[0092]

[0093] (6) Encapsulation of microscopic seepage model:

[0094] Table 4 shows the effect of different bonding conditions on pore depth. The main factors affecting the bonding effect of the micro-flow model include bonding time, bonding temperature, and applied pressure. The longer the bonding time, the better the bonding effect; excessively high or low bonding temperatures will cause the adhesive to fail; higher bonding pressure has a greater impact on the pore depth, while insufficient pressure will prevent the micro-model from being fully bonded, easily leading to leakage.

[0095] Remove the remaining wax layer from the engraved base plate surface three times with 50°C alcohol, 5 minutes each time, ensuring complete removal of the wax layer. Apply 2.5 mL of adhesive evenly to the surfaces of the cover and base plates, and let stand for 3 minutes to allow the adhesive to fully react with the surfaces. Align and fix the cover and base plates, place them in a tablet press, and apply uniform pressure at 0.2 MPa to 0.7 MPa. Immediately afterwards, place the tablet press in a vacuum drying oven at 10°C. -3 Under vacuum conditions of 0.5 MPa, the encapsulating adhesive trapped in the pores can be expelled from the percolation model. The vacuum environment is set at a temperature of 50℃~80℃ for 10min~20min. The preferred bonding pressure is 0.5 MPa, the bonding temperature is 70℃, and the bonding time is 15min. The micro-percolation model after bonding shows no swelling or cracking, and has minimal impact on the pore size, approximately 1μm. See the microscopic cross-sectional image of the encapsulated micro-percolation model in this embodiment of the invention. Figure 5 As shown.

[0096] Table 4. Reduction in pore thickness under different bonding conditions

[0097]

[0098] The beneficial effects of the technical solution provided by this invention are as follows:

[0099] (1) The encapsulating adhesive formulation proposed in this invention uses a preferred encapsulating adhesive to bond the acrylic base plate and cover plate to form a seepage model. This adhesive can avoid strong corrosion of the base plate and cover plate, thus affecting the geometry of the channel.

[0100] (2) The micro-flow model prepared by the pore surface mineral cementing agent and cementing method proposed in this invention can realize the simulation of oil-water-rock interaction in the pore space, which is difficult to achieve in existing methods. The coupling mechanism between oil, water and rock can be directly analyzed through this micro-flow model. Figure 6 This is a schematic diagram of surface mineral cementation.

[0101] (3) The encapsulation technology process proposed in this invention can minimize the impact of the encapsulation process on the pore depth by controlling the pressure, temperature, and duration of the tablet press, while ensuring that the microscopic permeation model after encapsulation is free from swelling, cracking, and whitening. Figure 7 This is a screenshot showing the application effect.

[0102] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a microscopic seepage model, comprising the following steps: a) The PMMA substrate is sequentially cleaned, laser-engraved, and cleaned to obtain a micro-permeation model base plate; b) The micro-flow model base plate obtained in step a) is mineral cemented with mineral cement on the pore surface, and finally the model is encapsulated with encapsulating adhesive to obtain the micro-flow model; The process of mineral cementation on the pore surface described in step b) is specifically as follows: Take 0.5 mL to 1 mL of mineral binder and apply it evenly to the pore surface of the micro-percolation model substrate, waiting for 1 to 3 minutes. Use nitrogen to purge the surface pores and remove any residual mineral binder. Then, take nano-CaCO3 powder or nano-SiO2 powder and spray it evenly onto the substrate surface, with a thickness exceeding the pore depth of the substrate by 0.5 mm to 1.5 mm. Place the sprayed substrate into a tablet press and press it at a pressure of 0.5 MPa to 1 MPa, a temperature of 20℃ to 30℃, and a pressing time of 5 to 15 minutes. After removing the substrate, clean the surface and pores of the substrate with alcohol and deionized water, 2 to 4 times each, for 5 minutes each time. Then, dry at room temperature to complete the surface mineral bonding. The mineral binder is prepared from raw materials comprising the following components: 8-15 parts by weight of PMMA powder; 3-10 parts by weight of ethyl α-cyanoacrylate; 50-80 parts by weight of dichloromethane; 3-10 parts by weight of p-toluenesulfonic acid.

2. The preparation method according to claim 1, characterized in that, The surface cleaning process described in step a) is as follows: The PMMA substrate was ultrasonically cleaned with alcohol and deionized water 2-4 times each, for 4-6 minutes each time; then dried at room temperature.

3. The preparation method according to claim 1, characterized in that, The laser engraving process described in step a) is as follows: a1) Wax sealing: Place the dried substrate sheet on the rotating table of the spin coater, set the temperature to 60℃~70℃, use the dropper to apply molten paraffin wax to the surface of the substrate, so that the entire surface of the substrate is covered, turn on the spin coater to spread the paraffin wax evenly, then remove the substrate and cool it at room temperature, so that the paraffin wax adheres to the substrate sheet to form a smooth, thin wax film with a thickness of less than 1μm. a2) Preparation of microscopic pore structure patterns: The pore patterns are taken from scanned images of actual rock core sections, with the porosity of the scanned images ranging from 10% to 30%; a3) Processing of the micro model: Using a laser engraving machine, the PMMA substrate is processed according to the prepared geometric pattern of the real rock core pores to obtain the engraved micro seepage model base plate.

4. The preparation method according to claim 3, characterized in that, The moving speed of the laser engraving machine mentioned in step a3) is 250mm / min~300mm / min.

5. The preparation method according to claim 1, characterized in that, The process of cleaning the channel described in step a) is as follows: First, clean the surface of the pores with alcohol and a brush 2-4 times, 4-6 minutes each time; then, ultrasonically clean the PMMA substrate with alcohol and deionized water 2-4 times each, 4-6 minutes each time; dry at room temperature to obtain the micro-permeation model substrate.

6. The preparation method according to claim 1, characterized in that, The specific method for preparing the mineral cementitious agent described in step b) is as follows: PMMA powder, ethyl α-cyanoacrylate, dichloromethane and p-toluenesulfonic acid are mixed and stirred continuously for 1 min to 5 min at a speed of 150 r / min to 250 r / min under air-isolated conditions. After standing, a mineral binder is obtained.

7. The preparation method according to claim 1, characterized in that, The encapsulating adhesive described in step b) is prepared from raw materials comprising the following components: PMMA powder 0.75~4 parts by weight; Formic acid 2-4 parts by weight; 2-4 parts by weight of methanol; 3-10 parts by weight of dichloromethane.

8. The preparation method according to claim 7, characterized in that, The preparation method of the encapsulating adhesive is as follows: PMMA powder, formic acid, methanol and dichloromethane are mixed and stirred continuously for 1 min to 5 min at a speed of 150 r / min to 250 r / min under air-isolated conditions. After standing, the encapsulating adhesive is obtained.

9. The preparation method according to claim 1, characterized in that, The model encapsulation process described in step b) is specifically as follows: Wipe away the residual wax layer on the surface of the engraved base plate 2-4 times with alcohol at 40℃~60℃, each time for 4min~6min; take 2mL~3mL of encapsulation adhesive and apply it evenly to the surface of the cover plate and the base plate, let it stand for 2min~5min to allow the encapsulation adhesive to fully react with the surface of the cover plate and the base plate respectively; align and fix the cover plate and the base plate, put them into the tablet press, and apply pressure evenly at 0.2MPa~0.7MPa; The tablet press was then immediately placed in a vacuum drying oven at 10°C. -5 Pa~10 -1 Under vacuum conditions of Pa, the encapsulating adhesive retained in the pores is discharged into the permeation model. The vacuum environment is set at a temperature of 50℃~80℃ for 10min~20min to obtain the micro-permeation model.

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