A microfluidic chip model, device and preparation method for simulating sand production of a formation

Abstract

This application discloses a microfluidic chip model, device, and fabrication method for simulating formation sand production. The invention involves placing a mask on a model substrate with stacked photoresist and chromium layers, followed by ultraviolet (UV) exposure to transfer the mask's shape onto the model substrate. The model substrate is then cleaned with a photoresist remover to remove UV-damaged photoresist. Exposed chromium is removed using a chromium remover, exposing the model substrate beneath the chromium layer. The model substrate is then wet-etched to create a pore network. A mixture of epoxy resin, quartz sand, and salts of a certain thickness is laid within the micropore throat structure with a certain etching depth. Finally, the model substrate is encapsulated with a cover plate to obtain the microfluidic chip model simulating formation sand production. This invention allows for the direct study of which parts of a simulated reservoir produce sand, how sand is produced, and the entire process of sand particles migrating within the pore network after production.

Description

Technical Field

[0001] This application relates to the field of oil and gas development technology, and in particular to a microfluidic chip model, device and preparation method for simulating formation sand production. Background Technology

[0002] Sand production in oil wells is a widespread problem that plagues production and operations in loose sandstone oilfields. The phenomenon of sand particles being transported out of the oil layer with fluids during oil and gas extraction is a common problem in sandstone reservoir development. In the context of loose sandstone reservoirs, sand production makes it difficult to increase oil production rates. Loose sandstone reservoirs are widely distributed in China, with large reserves and high production rates, and sand production in oil wells is a common problem during development. Some sandstone reservoirs (in water-injection development) do not initially produce sand, but as water content increases, sand production begins and gradually worsens, negatively impacting well production. Existing experimental methods mostly determine the degree of sand production and its impact on the reservoir by measuring the amount of sand produced. However, they cannot observe which parts of the simulated reservoir produce sand, how it occurs, or how the sand particles migrate after production. Therefore, they cannot analyze the specific mechanisms of sand production and cannot adequately meet the needs of oil well development. Summary of the Invention

[0003] In order to solve the above-mentioned technical problems, this application provides a microfluidic chip model, device and preparation method for simulating sand production in formations.

[0004] The present invention is achieved by the following technical solution.

[0005] A method for fabricating a microfluidic chip model simulating sand production in formations includes the following steps:

[0006] S1. Ultraviolet Exposure: The mask is placed on a model substrate with a layer of photoresist and a layer of chromium, and then exposed to ultraviolet light to transfer the shape of the mask onto the model substrate;

[0007] S2. Remove photoresist: Clean the model substrate with a photoresist remover to remove the photoresist damaged by ultraviolet light;

[0008] S3. Chromium removal: Use chromium removal solution to wash away the chromium exposed in step S2, exposing the model substrate under the chromium layer;

[0009] S4. Model Substrate Etching: The model substrate is wet-etched to complete the pore network characterization;

[0010] S5. In a micro-pore throat structure with a certain etching depth, a mixture of epoxy resin, quartz sand and salts of a certain thickness is laid.

[0011] S6. Packaging: The model substrate and cover plate are packaged to obtain a microfluidic chip model simulating sand production in the formation.

[0012] Furthermore, the internal structure and depth of the pore network can be designed according to the parameters of the actual reservoir, with the depth of the pore network structure ranging from 40μm to 90μm.

[0013] Furthermore, the cover plate is provided with multiple injection holes and discharge holes.

[0014] Furthermore, in step S1, the ultraviolet exposure time is 10 seconds.

[0015] Furthermore, in step S2, the washing solution is a sodium hydroxide solution with a concentration of 5‰.

[0016] Furthermore, in step S3, the chromium washing solution includes cerium ammonium nitrate and acetic acid, with a volume ratio of cerium ammonium nitrate to acetic acid of 6:1.

[0017] Furthermore, in step S4, the etching solution used in the wet etching is an aqueous solution of hydrofluoric acid, and the etching time is 27-60 minutes.

[0018] Furthermore, in step S5, the laying thickness is 10-20 μm.

[0019] Furthermore, in step S5, the mass ratio of epoxy resin, quartz sand, and salt is 1:1:1 or 2:2:1.

[0020] A microfluidic chip model for simulating sand production in strata, prepared by the above method.

[0021] A microfluidic chip device for simulating formation sand production includes the aforementioned microfluidic chip model for simulating formation sand production. A liquid storage tank and a simulated screen completion are respectively provided on both sides of the model. The liquid storage tank is connected to the injection fluid channel, and the simulated screen completion is connected to the discharge fluid channel.

[0022] Furthermore, the well completion method zone can be designed according to different well completion methods, such as screen completion, open hole completion, etc.

[0023] Furthermore, the width of the fluid channel is 20μm-100μm and the depth is 40μm-90μm; the depth of the well completion area is 40μm-90μm.

[0024] This application has the following beneficial effects.

[0025] The model channel of this invention is fabricated using a wet etching method with an aqueous solution of hydrofluoric acid (HF). Due to the isotropic etching properties of HF during the etching process of the glass channel, the channel is continuously etched deeper longitudinally and wider laterally. A mixture of epoxy resin, quartz sand, and salts of a certain thickness is then laid inside the etched channel, and finally, a microfluidic chip model simulating formation sand production is fabricated through bonding. This invention further innovates upon existing technologies, allowing for a direct study of which parts of the simulated reservoir produce sand, how sand is produced, and the entire process of how sand particles migrate within the pore network after production. This is of great significance for studying the impact of sand production on reservoir properties and recovery rate during production, as well as for understanding the sand production mechanism. Attached Figure Description

[0026] Figure 1 This is a flowchart of the fabrication process of a microfluidic chip model for simulating sand production in strata.

[0027] Figure 2 This is a schematic diagram of the microfluidic chip device for simulating formation sand production (the inlet section simulates open-hole completion, and the outlet section simulates screen completion).

[0028] Figure 3 This is a schematic diagram of the microfluidic chip device for simulating formation sand production (the inlet section simulates screen pipe completion, and the outlet section simulates screen pipe completion).

[0029] Figure 4 This is a schematic diagram of the pore throat sand-laying of the microfluidic chip model for simulating formation sand production according to the present invention;

[0030] Figure 5 This is a physical image of the microfluidic chip model for simulating sand production in formation according to the present invention;

[0031] Figure 6 This is a magnified microscopic view of the microfluidic chip model for simulating sand production in formation according to the present invention;

[0032] Figure 7 The microfluidic chip model of this invention is used to simulate the sand production of formation particles and the sand production diagram. Detailed Implementation

[0033] The present patent application will be further described below with reference to the embodiments.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used in the following preparation examples and examples are commercially available unless otherwise specified.

[0035] Example 1

[0036] like Figure 2 As shown, a microfluidic chip device for simulating formation sand production includes a simulated sand-producing formation 4, a simulated screen completion 5, a simulated open-hole completion 3, an injection fluid channel 2, and a discharge fluid channel 6; the front end of the injection fluid channel 2 forms a fluid injection port 1, and the end end of the discharge fluid channel 6 forms a fluid discharge port 7. The method for preparing the simulated sand-producing formation 4 includes the following steps:

[0037] S1. Sheet acquisition steps: Take a 1mm thick quartz sheet (3cm long and 3cm wide) as the transparent substrate sheet, and take a 1mm thick quartz sheet (3cm long and 3cm wide) as the transparent substrate cover sheet.

[0038] S2. Photomask Preparation: Prepare a micron-scale channel photomask (commercially available, such as...) Figure 2 As shown, the black areas are translucent, and the rest are opaque.

[0039] S3. Pore Network Characterization: A pore network photomask is stacked on a transparent substrate sheet coated with photoresist. The pore network area is exposed using an exposure machine (10s). Then, the photoresist coating on the exposed pore network area is removed using a 5‰ sodium hydroxide solution. Next, the chromium exposed in the previous step (chromium plate glass with chromium layer) is washed away using a chromium removal solution, exposing the glass under the chromium layer. The glass in the pore network area is removed using a hydrofluoric acid solution. The etching time is 27 minutes (etching rate of 1.5 micrometers per minute), completing the pore network characterization. The pore network etching depth is 40um.

[0040] S4. Photoresist Coating Removal: Use a photoresist removal solution (5% NaOH) to remove the photoresist coating from the surface of the transparent substrate sheet;

[0041] S5. Chromium Coating Removal: The chromium coating on the surface of the transparent substrate sheet is removed using a chromium removal solution, thus obtaining the transparent substrate sheet;

[0042] S6. Sand Laying Inside the Pore Network: Epoxy resin, fine sand, and sodium chloride are uniformly mixed in a 1:1:1 ratio, and then evenly laid inside the pore network to a thickness of 20 micrometers (e.g., ...). Figure 4 As shown), complete the sand laying inside the pore network;

[0043] S7. Transparent substrate cover sheet acquisition steps: The transparent substrate cover sheet is perforated to obtain each injection hole and each discharge hole, thereby obtaining the transparent substrate cover sheet;

[0044] S8. Model encapsulation steps: The transparent matrix cover sheet and the transparent matrix substrate are bonded together by room temperature vacuum hot pressing (180KN) to ensure tight adhesion between the transparent matrix cover sheet and the transparent matrix substrate for 24 hours, thus completing the model encapsulation.

[0045] Example 2

[0046] like Figure 3 As shown, a microfluidic chip device for simulating formation sand production includes a simulated sand-producing formation 4, simulated screen completions 5 on both sides of the simulated sand-producing formation 4, an injection fluid channel 2, and a discharge fluid channel 6; a fluid injection port 1 is formed at the front end of the injection fluid channel 2, and a fluid discharge port 7 is formed at the end of the discharge fluid channel 6. The method for preparing the simulated sand-producing formation 4 includes the following steps:

[0047] S1. Sheet acquisition steps: Take a 1mm thick quartz sheet (3cm long and 3cm wide) as the transparent substrate sheet, and take a 1mm thick quartz sheet (3cm long and 3cm wide) as the transparent substrate cover sheet.

[0048] S2. Photomask Preparation: Prepare the micron-scale channel photomask (commercially available, such as...). Figure 3 As shown, the black areas are translucent, and the rest are opaque.

[0049] S3. Pore Network Characterization: A pore network photomask is stacked on a transparent substrate sheet coated with photoresist. The pore network area is exposed using an exposure machine (10s). Then, the photoresist coating on the exposed pore network area is removed using a 5‰ sodium hydroxide solution. Next, the chromium exposed in the previous step is removed using a chromium removal solution, exposing the glass beneath the chromium layer. The glass in the pore network area is then removed using a hydrofluoric acid solution. The etching time is 27 minutes, completing the pore network characterization. The pore network etching depth is 40µm.

[0050] S4. Photoresist Coating Removal: Use a photoresist removal solution (5% NaOH) to remove the photoresist coating from the surface of the transparent substrate sheet;

[0051] S5. Chromium Coating Removal: The chromium coating on the surface of the transparent substrate sheet is removed using a chromium removal solution, thus obtaining the transparent substrate sheet;

[0052] S6. Sand Laying Inside the Pore Network: Epoxy resin, pulverized sand, and sodium chloride are uniformly mixed in a 1:1:1 ratio, and then evenly laid inside the pore network to a thickness of 20 micrometers (e.g., ...). Figure 4 As shown), complete the sand laying inside the pore network;

[0053] S7. Transparent substrate cover sheet acquisition steps: The transparent substrate cover sheet is perforated to obtain each injection hole and each discharge hole, thereby obtaining the transparent substrate cover sheet;

[0054] S8. Model encapsulation steps: The transparent matrix cover sheet and the transparent matrix substrate are bonded together by room temperature vacuum hot pressing (180KN) to ensure tight adhesion between the transparent matrix cover sheet and the transparent matrix substrate for 24 hours, thus completing the model encapsulation.

[0055] Application examples

[0056] (1) Obtained by photolithography, photoresist removal, chromium removal, etching and bonding. Figure 5 A microfluidic chip model simulating sand production in formations. Figure 6 A magnified microscopic view of a microfluidic chip model simulating sand production in formations.

[0057] (2) Water is injected into the water injection end of the microfluidic model, and the sand is observed under a microscope to see how the sand particles are transported after the sand is released.

[0058] (3) Microscopic observation revealed that with the scouring of the water, some loosely cemented gravel was detached from the microfluidic model and transported within the model as follows: Figure 7 As shown.

[0059] This invention can provide a systematic and in-depth understanding of the sand production patterns of formation particles and their impact on oilfield production. By designing a microfluidic chip model to simulate sand production, a planar displacement simulation experiment is conducted to study the patterns, influencing factors, and consequences of formation particle migration and sand production in loose sandstone reservoirs.

[0060] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for fabricating a microfluidic chip model simulating sand production in formations, characterized in that: Includes the following steps: S1. Ultraviolet Exposure: The mask is placed on a transparent substrate with a photoresist layer and a chromium layer stacked on it, and then exposed to ultraviolet light to transfer the shape of the mask onto the transparent substrate. S2. Remove photoresist: Clean the transparent substrate with a photoresist remover solution to remove the photoresist damaged by ultraviolet light. S3. Chromium removal: Use chromium removal solution to wash away the chromium exposed in step S2, exposing the transparent substrate under the chromium layer; S4. Etching of transparent matrix substrate: Wet etching of transparent matrix substrate is performed to complete the pore network characterization; S5. Photoresist Coating Removal: Use 5% NaOH cleaning solution to remove the photoresist coating from the surface of the transparent substrate sheet; S6. Chromium Coating Removal: The chromium coating on the surface of the transparent substrate sheet is removed using a chromium removal solution, thus obtaining the transparent substrate sheet; S7. In a micro-pore throat structure with a certain etching depth, a mixture of epoxy resin, quartz sand and salts of a certain thickness is laid. S8. Encapsulation: The transparent matrix substrate and the cover plate are encapsulated to obtain a microfluidic chip model that simulates sand emergence from the formation.

2. The method for preparing a microfluidic chip model simulating sand production in formations according to claim 1, characterized in that: The depth of the porous network structure is 40μm-90μm.

3. The method for preparing a microfluidic chip model simulating sand production in formations according to claim 1, characterized in that: The cover plate is provided with multiple injection holes and discharge holes.

4. The method for preparing a microfluidic chip model simulating formation sand production according to claim 1, characterized in that: In step S1, the ultraviolet exposure time is 10 seconds.

5. The method for preparing a microfluidic chip model simulating formation sand production according to claim 1, characterized in that: In step S2, the washing solution used is a sodium hydroxide solution with a concentration of 5‰.

6. The method for preparing a microfluidic chip model simulating formation sand production according to claim 1, characterized in that: In step S3, the chromium washing solution includes cerium ammonium nitrate and acetic acid, with a volume ratio of cerium ammonium nitrate to acetic acid of 6:

1.

7. The method for preparing a microfluidic chip model simulating formation sand production according to claim 1, characterized in that: In step S4, the etching solution used in the wet etching process is an aqueous solution of hydrofluoric acid, and the etching time is 27-60 minutes.

8. The method for preparing a microfluidic chip model simulating formation sand production according to claim 1, characterized in that: In step S5, the laying thickness is 10-20 μm.

9. A microfluidic chip model for simulating sand production in a formation, prepared by the method described in any one of claims 1-8.

10. A microfluidic chip device for simulating formation sand production, characterized in that: The microfluidic chip model for simulating formation sand production as described in claim 9 is provided on both sides of the model, with a simulated open-hole completion (3) and a simulated screen completion (5) respectively. The simulated open-hole completion (3) is connected to the injection fluid channel (2), and the simulated screen completion (5) is connected to the discharge fluid channel (6).

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