A method for making a microscopic glass model of heterogeneous rock pores

Abstract

The present invention belongs to the technical field of petroleum development, and specifically relates to a method for making a microscopic glass model of heterogeneous rock pores. The method includes, during the process of making an image negative film, obtaining a pore map with different permeability gradients based on a thin film image of a cast body of a core with different permeabilities to make a negative film; converting the width of the pores in the high permeability zone according to the depth requirements of the design, obtaining a contracted size, and performing photoetching on a chrome plate; etching glass to form three-dimensional channels of different depths, first etching several shallow depth zones, one part as a low permeability zone and one part as a high permeability zone; sealing the channels etched as the low permeability zone portion; and etching the channels etched as the high permeability zone portion a second time to form high permeability zone channels. The model made by the method of the present invention has three-dimensional channels of varying depths, which can simulate the actual situation of fluid migration in the channels, reflecting the difference in permeability not only in the plane but also in the vertical direction.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum development, and in particular relates to a method for manufacturing a microscopic glass model of heterogeneous rock pores. Background Art

[0002] Currently, there are two main types of micromodels used in microscopic flooding simulation experiments in the petroleum industry: glass models and real sandstone models. A classic reference is "Microscopic Seepage Experimental Mechanics and Its Applications" by Huang Yanzhang and Yu Dasen, which details traditional fabrication methods. Based on this, I have subsequently disclosed methods for fabricating real core micromodels (CN103778841A), large-scale micromodels (CN105628577B), and medium-permeability core microglass models (CN110563340A).

[0003] Microscopic glass models emerged in the 1970s and have been widely used in scientific research due to their prominent feature of intuitive visualization. In recent years, with the advancement of equipment precision and research capabilities, research questions have become more precise and detailed, and the requirements for microscopic models have also continued to rise. The innovation of this project is closely related to the high quality of microscopic models. This invention builds on traditional production methods and innovates to produce more targeted and complex three-dimensional channel models, addressing the urgent needs of specialized scientific research.

[0004] Traditional microscopic models are two-dimensional models with uniform vertical heights, meaning all pores within the model have the same depth. This representation is used to characterize the three-dimensional nature of actual reservoirs by analyzing the two-dimensional variations in fluid flow within the model. This representation ignores the effects of fluid gravity and vertical variations, leading to controversy. Although real sandstone microscopic models are three-dimensional models with multiple layers of pores distributed vertically, the overlap of pores within the same field of view severely impacts imaging, making them less intuitive and visually pleasing.

[0005] After searching relevant domestic and foreign patents and literature, no method for making three-dimensional channels of glass models and related explanations were found. Summary of the Invention

[0006] The main purpose of the present invention is to provide a method for making a microscopic glass model of heterogeneous rock pores. The model made by the method of the present invention has three-dimensional channels of varying depths, which can simulate the actual situation of fluid migration in the channels and reflect the difference in permeability not only in the plane but also in the vertical direction.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for making a microscopic glass model of heterogeneous rock pores, which comprises making an image negative film, making a photolithographic chrome plate, etching glass to form three-dimensional pores, and sintering the model; in the process of making the image negative film, a pore map with different permeability gradients is obtained based on a cast thin-section map of a core with different permeability to make the negative film;

[0009] According to the designed depth requirements, the width of the pores in the hyperpermeable zone is converted to obtain the shrinkage size and the photoetched chrome plate is produced;

[0010] Glass is etched to form three-dimensional channels of different depths. First, several shallow depth zones are etched, one part of which serves as a low permeability zone and the other part as a high permeability zone. The channels etched as the low permeability zone are sealed with a film. The channels etched as the high permeability zone are etched a second time to form high permeability zone channels.

[0011] Furthermore, the side erosion effect is eliminated by reducing the size of the deepened portion of the pattern on the photolithographic chrome plate, and the width of the pores in the high permeability zone is reduced to half the depth difference between the high and low permeability zones.

[0012] Furthermore, the width of the throat in the base plate is measured to determine the throat reduction factor.

[0013] Furthermore, the throat reduction ratio is controlled between 1.5-2.5 times.

[0014] Furthermore, during the production of the photolithographic chrome plate, the low permeability zone needs to be exposed twice to increase the size of the photolithographic channel. According to the side etching effect caused by the designed longitudinal depth difference, the secondary exposure time is set to perform secondary photolithography on the low permeability zone.

[0015] Furthermore, the secondary lithography time cannot exceed 10s.

[0016] Furthermore, the exposed glass portion of the photolithography chrome plate after the glue is solidified is sealed with a film, and the sealed photolithography chrome plate is placed horizontally in the etchant with the face facing up for the first etching; after the first etching is completed and the inspection is passed, the low-permeability zone of the chrome plate glass is sealed separately, and then the high-permeability zone is etched separately and overlapped.

[0017] The present invention also provides a microscopic glass model of heterogeneous rock pores prepared by any of the above methods.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The present invention provides a method for making a microscopic glass model of heterogeneous rock pores. The method of the present invention can prepare a model with three-dimensional channels, enhance the intuitive visibility of the model, and meet the needs of existing research on complex heterogeneous rock pore microscopic glass models. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0021] Figure 1 This is a comparison diagram of the conventional model of the heterogeneous rock pore microscopic glass model and the model described in Example 1: A is the conventional model; B is the model described in Example 1.

[0022] Figure 2 Comparison diagram of the cross-sections of the conventional model of the heterogeneous rock pore micro-glass model and the model described in Example 1; a is a cross-section diagram of the model described in Example 1; b is a cross-section diagram of the conventional model;

[0023] Figure 3 This is the bound water saturated oil diagram of the model described in Example 1 with a high permeability depth of 100 μm in the middle and a depth of 40 μm elsewhere.

[0024] Figure 4 This is a 100x100mm large-scale model diagram of "one injection and four production", which includes four permeability difference areas composed of channels with different widths and depths. DETAILED DESCRIPTION

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0026] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations and / or combinations thereof.

[0027] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0028] The glass chrome plate used in the present invention is a Hunan "Shaoguang" chrome plate. The old photolithography machine used in the present invention is an early product produced by the Shanghai Photolithography Machine Factory. All existing photolithography machines are applicable to this method. The laboratory environment temperature is 15-30°C, the ambient humidity is <70%, and the chrome layer thickness of the chrome plate used is 100-150nm, and the average thickness of the photoresist is 500-600nm.

[0029] Example 1

[0030] A method for making a microscopic glass model of heterogeneous rock pores, the method comprising the following steps:

[0031] Step 1: Design and produce the image base: First, create a film base with different permeability gradient pore maps based on thin-section images of cores with different permeabilities. Microscopically inspect the film to ensure that the pore size does not deviate by more than 5μm. Then, measure the width of the pores and throats in the high-permeability zone using a microscope and record the results.

[0032] Step 2: Photolithography chrome plate production:

[0033] (1) After obtaining the heterogeneous core image base, carefully observe the base quality through a microscope. The black and white are clearly distinguished and there is no pore adhesion.

[0034] (2) Calculate the impact of lateral erosion: For example, the design requires that the depth of the large channel in the high permeability zone be 40μm and the depth of the small channel be 10μm, with a difference of 30μm. The measured erosion width is usually 0.5 times the depth. The lateral erosion impact is: 30*0.5=15μm. Therefore, the width of the large channel needs to be reduced by 15μm. Further measure the width of the throat in the base plate and convert it into the corresponding reduction factor to meet the technical requirements of the design. The reduction factor needs to be controlled between 1.5-2.5 times. For example, if the narrowest throat width is 25μm and the designed throat width is 10μm, then it needs to be reduced by 2.5 times.

[0035] (3) Adjust the distance between the concave lens of the photolithography machine and the image base and the glass chrome plate to achieve the required reduction factor. Set the exposure time to 10 seconds. The exposure time in summer is 1-2 seconds shorter than in winter. Set the exposure intensity to the highest level and photolithography onto the glass chrome plate.

[0036] (4) Gently cover the high permeability zone with a black opaque film (be careful when operating, and the original base plate cannot move). According to the side erosion effect caused by the designed longitudinal depth difference (0.5 times the depth), set the secondary exposure time to 4μm / s. For example, if the high and low permeability depth difference is designed to be 40μm, the side erosion effect is 40*0.5=20μm, and the exposure time is 20 / 4=5s. When performing secondary photolithography on the low permeability zone, be careful not to exceed 10s, otherwise the chrome plate will have noise that affects the model quality.

[0037] (5) Chemical chromium removal:

[0038] This step removes the exposed chromium from the chrome plate. First, soak the plate in a 6% sodium hydroxide solution for 5-10 seconds. Rinse it with purified water and then soak it in a 15% ammonium cerium nitrate solution for 40-60 seconds to chemically remove the chromium. Rinse again with purified water and set aside. The chemical reaction time is 5-10 seconds shorter in summer than in winter.

[0039] During the photolithography process, longer exposure times and higher ambient temperatures accelerate the chromium removal reaction, making it less likely to cause channel adhesion and more difficult to control. Higher ambient humidity increases the thickness of the chromium colloid, providing better chromium protection and slower chemical reactions. This makes channel precision easier to achieve, but also increases the risk of channel adhesion. Seasonal changes are also a significant influencing factor.

[0040] (6) Glue

[0041] The qualified photolithographic chrome plate is placed in a high-temperature furnace, heated to 200°C, and held at this temperature for 2-4 hours to cure the adhesive. Then, the edges of the photolithographic image or pattern are inspected under a microscope to ensure they are flat and smooth, meeting design requirements, and ready for use. This step enhances the protective properties of the chrome layer to ensure accuracy.

[0042] Step 3: Etch the glass to form three-dimensional channels of different depths:

[0043] This step targets the two depths designed for the model. The first step etches all the patterns to a shallower depth requirement, and the second step etches the high permeability zone pore patterns separately to a deeper depth, forming a depth difference.

[0044] (1) Select an etchant and determine the etching rate (see patent CN110563340A), for example, an etching rate of 8 μm / m.

[0045] (2) Calculate the etching time based on the designed low permeability zone depth and etching rate. For example, if the low permeability zone depth is 24 μm, the etching time is 24 / 8 = 3 m. Seal the exposed glass portion of the photolithographic chrome plate after the adhesive is solidified. Place the sealed photolithographic chrome plate horizontally in the strong acid etchant with the plate facing upwards and etch for the set time. Quickly remove the plate and rinse it repeatedly in pure water, then dry it. Inspect the low permeability zone under a microscope to see if it meets the design requirements and set aside.

[0046] (3) Etch the high permeability zone separately and in an overlapping manner. Determine the etching time based on the designed depth difference and etching speed. After the first etching is completed and the inspection is qualified, seal the low permeability zone of the chrome plate glass separately. Place it face up and horizontally in the strong acid etchant and etch according to the set time. Quickly remove it and rinse it repeatedly in pure water, and dry it at 35-40℃. Check under a microscope whether the high permeability zone meets the design requirements and set it aside.

[0047] Step 4: Model melting:

[0048] This step can be used in conjunction with model making precision control to achieve 10μm accuracy.

[0049] (1) Punch holes at predetermined locations on the etched and inspected glass chrome plate.

[0050] (2) Carefully clean the finished chrome plate glass, including the reaction impurities in the pores. After cleaning, place it in an oven and heat it to 45°C to dry it for later use.

[0051] (3) Align the glass partition and the matching polishing sheet to form a microscopic model, and gently place it on the tile pad of the high-temperature furnace. Slowly increase the temperature to 200℃ and maintain the temperature for 1.5 hours.

[0052] (4) Perform the first sintering, slowly heating and cooling. Set the temperature to 635°C and keep it constant for 1.5 hours.

[0053] (5) After the first sintering is completed, take out the model and check the size under a microscope.

[0054] (6) If a 10 μm precision model is to be produced, a second sintering is performed as above. After completion, the model is taken out and the dimensions are measured. If the model meets the requirements, the production is completed. For details, see patent application CN110563340A.

[0055] Figure 1 、 Figure 2 This is a comparison between the heterogeneous rock pore micro-glass model described in Example 1 and the conventional model. Figure 3 This is the bound water saturated oil diagram of the model with a high permeability depth of 100 μm in the middle part and a depth of 40 μm in the other parts of the model described in Example 1. Figure 4 shown.

[0056] In summary, the model of the present invention can simulate the actual situation of fluid migration in the pores, reflecting the difference in permeability not only in the plane but also in the vertical direction.

[0057] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for making a microscopic glass model of heterogeneous rock pores, characterized in that: The method comprises the following steps: Step 1. Image base design and production: First, a film negative was created based on the cast thin-section images of cores with different permeabilities to obtain pore maps with different permeability gradients. The pore size of the film was examined under a microscope to ensure that no deviation of more than 5 μm could be observed. The width of the pores and throats in the high permeability zone was then measured and recorded using a microscope. Step 2. Photolithography chrome plate production: (1) After obtaining the heterogeneous core image base, carefully observe the base quality under a microscope to ensure that the black and white are clear and there is no pore adhesion; (2) Calculate the impact of side erosion: Measure the width of the throat in the base plate and convert it into the corresponding reduction factor, which should be controlled within 1.5-2.5 times; (3) Adjust the distance between the concave lens of the photolithography machine and the image base and the glass chrome plate to meet the corresponding reduction factor requirements; set the exposure time to 10s. The exposure time in summer is 1-2s shorter than that in winter. Set the exposure intensity to the highest level and photolithography onto the glass chrome plate; (4) Lightly cover the high permeability zone with a black opaque film and set the secondary exposure time according to the side erosion effect caused by the designed longitudinal depth difference; perform secondary photolithography on the low permeability zone, and the time should not exceed 10s; (5) Chemical chromium removal; (6) Glue solidification; Step 3. Etch the glass to form three-dimensional channels of different depths: The first etching is to etch all the patterns to a shallow depth, and the second etching is to etch the high permeability zone pore patterns to a deeper depth, forming a depth difference; (1) Select the etchant and determine the etching rate; (2) Calculate the etching time based on the designed low permeability zone depth and etching rate, seal the exposed glass portion of the photolithography chrome plate after the glue is solidified, place the sealed photolithography chrome plate facing up in a horizontal position in a strong acid etchant for etching, quickly remove it from the plate, rinse it repeatedly in pure water, and dry it; (3) Etch the high permeability zone separately and in an overlapping manner, and determine the etching time according to the designed depth difference and etching speed; after the first etching is completed and the qualified chrome plate glass low permeability zone is sealed separately, placed face up and horizontally in a strong acid etchant for etching, quickly taken out and repeatedly washed in pure water, and dried; Step 4: Model melting.

2. The heterogeneous rock pore microscopic glass model prepared by the method of claim 1.

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