Shale oil reservoir core micro-percolation model and preparation method and application thereof

Abstract

The application discloses a shale oil reservoir core micro-percolation model and a preparation method and application thereof, and belongs to the technical field of oilfield development experiment researches.The core micro-percolation model comprises a rock sample and adhesive glass sheets used on two surfaces of the rock sample, and according to the oil-water flow direction in the rock sample, the side surface of the rock sample is set as an inflow end, an outflow end, a first end and a second end respectively, one or two needle heads are arranged close to the inflow end, one needle head is arranged close to the outflow end, and the core micro-percolation model is packaged through glue.The single-needle head and double-needle head micro-percolation models are prepared for different types of shale oil reservoir cores, and oil-water two-phase percolation experiments are carried out on typical rock samples; through the experiments, more accurate understanding of the percolation channels of oil and water in the shale reservoir core is obtained, the distribution states of residual oil and bound water in the core are accurately characterized in a visualized mode, and important references can be provided for the research on percolation curves, the understanding of percolation rules and the compilation of development schemes.

Description

Technical Field

[0001] This invention relates to the field of experimental research technology in oilfield development, specifically to a microscopic seepage model of shale oil reservoir cores, its preparation method, and its application. Background Technology

[0002] With the continuous growth of global energy demand, shale oil, as an important unconventional oil and gas resource, is being explored and developed at an increasingly rapid pace. However, compared with traditional sandstone reservoirs, shale oil reservoirs have smaller storage spaces and more complex flow channels, which poses many challenges to shale oil extraction.

[0003] Traditional flow experiments, while capable of revealing fluid flow characteristics within reservoirs to some extent, struggle to provide a direct and in-depth analysis of the impact of shale oil reservoir space, flow channels, and displacement mechanisms on its extraction effectiveness. This is primarily due to the extremely complex microstructure of shale oil reservoirs, making it difficult for traditional experimental methods to capture these microscopic features.

[0004] To address this issue, numerous invention patents related to microscopic seepage model experiments have emerged in recent years. These patents primarily focus on two aspects: On the one hand, there are methods for preparing different types of microscopic seepage models. These patents provide detailed descriptions of different types of core samples or different preparation methods, aiming to reveal the flow patterns of fluids within shale oil reservoirs by accurately simulating their microstructure. The preparation methods for these models typically involve high-precision imaging technology, three-dimensional reconstruction technology, and micromachining technology, enabling the creation of microscopic models with complex pore structures and seepage channels, thereby more accurately reflecting the actual conditions of shale oil reservoirs.

[0005] On the other hand, there are microscopic seepage experimental device systems. These invention patents provide detailed descriptions of microscopic seepage experimental devices, aiming to offer an experimental platform capable of precisely controlling experimental conditions and monitoring fluid flow in real time. These devices typically include high-precision pressure control systems, flow control systems, and image acquisition and analysis systems, enabling quantitative analysis and visualization of fluid flow behavior within microscopic models.

[0006] However, while these patented inventions have addressed some of the limitations of traditional seepage testing methods in core studies of different types of reservoirs, several issues remain. For example, how to further improve the accuracy and realism of the models to more accurately reflect the microstructure of shale oil reservoirs; how to optimize the design of experimental apparatus to improve experimental efficiency and accuracy; and how to combine the results of microscopic seepage experiments with practical applications to provide more effective guidance for shale oil exploration and development.

[0007] Therefore, future research needs to explore and innovate in these areas to promote the continuous development and improvement of shale oil exploration and development technologies. By continuously optimizing the preparation methods of microscopic seepage models and experimental equipment systems, we can gain a deeper understanding of the microscopic characteristics of shale oil reservoirs, providing strong technical support for the efficient extraction of shale oil. Summary of the Invention

[0008] The purpose of this invention is to provide a microscopic seepage model of shale oil reservoir cores, its preparation method, and its application, in order to solve the problems of small pore volume and poor physical properties in unconventional shale oil reservoirs, and the difficulty in intuitively evaluating seepage channels and fluid occurrence state at the microscopic scale in real core oil-water two-phase seepage experiments.

[0009] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a microscopic seepage model of shale oil reservoir cores, including a rock sample. A glass slide is placed on one side of the rock sample, and a glass cover is placed on the other side. According to the experimental design, the oil and water flow direction in the rock sample is designed. The sides of the rock sample are divided into an inflow end, an outflow end, a first end, and a second end. One or two needles are placed near the inflow end, and one needle is placed near the outflow end. The inflow end and the outflow end are sealed with glue at a predetermined distance from the inflow end and the first end and the second end are sealed with glue.

[0010] The rock sample has a thickness of 0.3~0.5mm, a length of 2.0~2.5cm, a width of 2.0~2.5cm, and a compressive strength of 0~1.0MPa.

[0011] Seal with glue at a distance of 2-3mm from the inlet and outlet ends.

[0012] The length of the glass slide is 6.0~6.5cm and the width is 4.5~5.0cm. The length of the glass cover is 4.0~4.5cm and the width is 3.0~3.5cm.

[0013] The diameter of the needle is 0.45~0.5mm.

[0014] This invention also provides a method for preparing a microscopic seepage model of a shale oil reservoir core, comprising: Shale oil reservoir cores from the study block were selected as rock samples. The crude oil in the rock samples was completely washed out and dried to obtain prepared rock samples. The prepared rock sample is blasted to the preset length and width, and the blasted surface is ground flat to obtain the first surface of the rock sample; Apply glue to the first surface of the rock sample, cover the first surface of the rock sample with a glass slide, and bond the first surface of the rock sample and the glass slide together with glue. After the first side of the rock sample is pasted, let it stand for 24 to 30 hours. Then cut the prepared rock sample. The thickness of the prepared rock sample after cutting is 0.8 to 1 mm. Grind the cut surface to reduce the thickness of the prepared rock sample to 0.3 to 0.5 mm to obtain the second side of the rock sample. Apply glue to the second side of the rock sample, cover the second side of the rock sample with a glass cover, and bond the second side of the rock sample and the glass cover with glue. After the second side of the rock sample is pasted, fill the first and second ends of the rock sample with glue evenly until the first and second ends of the rock sample are completely sealed with glue. Place needles at the inflow and outflow ends of the rock sample, leaving a gap of 1-2 mm between the needles and the inflow or outflow ends. Fill the inflow and outflow ends of the rock sample with glue evenly, keeping the distance between the glue and the inflow and outflow ends 2-3 mm during the glue filling process. After bonding the glass slide, glass cover plate, and needle, let it stand for 24-30 hours, and then seal the sides of the rock sample with adhesive again. After standing for 24-30 hours, a micro-permeability model of the shale oil reservoir core is obtained.

[0015] When two needles are used, the distance between the two needles should be 0.8~1.2cm.

[0016] The adhesive is prepared by mixing two types of adhesive in a certain proportion, and then letting it stand for 20-30 minutes after preparation.

[0017] This invention also provides an application of a shale oil reservoir core micro-flow model in displacement experiments, including: The microscopic seepage model of the shale oil reservoir core was photographed under a microscope to preserve the original state of the microscopic seepage model of the shale oil reservoir core. Simulated formation water with added methylene blue and simulated kerosene with added oil red were added to different intermediate containers, which were connected to the displacement pump via pipelines. The needle at the inflow end of the micro-permeability model of the shale oil reservoir core is connected to the intermediate container through a pipeline, and the needle at the outflow end is connected to the metering container through a pipeline. Pump pressure parameters are set. The process is carried out sequentially as follows: water drive, oil drive water, and water drive oil. During the experiment, photos were taken at preset times to record the seepage of oil and water in the micro-seepage model of the shale oil reservoir core, observe the occurrence state of residual oil and bound water in the core, and record the amount of produced fluid.

[0018] The pump pressure during water-driven processes is 0.02~0.50 MPa; the pump pressure during oil-driven water processes is 0.02~0.80 MPa; and the pump pressure during water-driven oil processes is 0.02~0.80 MPa.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention prepared single-needle and double-needle micro-flow models for different types of shale oil reservoir cores, and successfully conducted oil-water two-phase flow experiments using typical rock samples. The micro-flow model can be equipped with one or two needles at the inflow end, depending on experimental requirements. The double-needle configuration not only increases the initial sweep area of ​​the fluid entering the core, making the flow process closer to actual formation conditions, but also allows for a more in-depth study of flow patterns by comparing the flow conditions under different needles. The single-needle configuration is suitable for simplifying experimental conditions. Displacement experiments conducted using the micro-flow model of this invention provide a more accurate understanding of the oil and water flow channels in the reservoir core. Simultaneously, it provides a precise and visualized representation of the distribution of residual oil and bound water in the core, offering important references for the study of flow curves, understanding of flow patterns, and the formulation of development plans.

[0020] This invention provides a method for constructing a microscopic seepage model of shale oil reservoir cores. By selecting shale oil reservoir cores from the study block as samples and ensuring their representativeness, the model can accurately reflect the actual situation of the shale oil reservoir, improving the accuracy and reliability of experimental results. The bonding surfaces of the rock samples and glass slides undergo rigorous grinding and cleaning to remove impurities and unevenness that may affect the adhesive effect, improving the strength and sealing of the bond. This invention allows for the setting of single or double needles as needed, meeting the requirements of different types of experiments and improving the applicability and flexibility of the model. The reserved gaps between the needle and the inflow and outflow ends, as well as the distance control during the glue filling process, ensure smooth fluid flow in the rock samples and the accuracy of experimental results. The high-quality model and precise control of experimental conditions make the experimental results more reliable and convincing, providing strong technical support for the development and related research of shale oil reservoirs.

[0021] Furthermore, a specially formulated adhesive was selected, and its flowability and curing effect were optimized through a static treatment process to avoid the generation of air bubbles and ensure the transparency of the bond and the experimental results.

[0022] This invention provides a microscopic seepage model of shale oil reservoir cores for displacement experiments. Through processes such as waterflooding, oil-water flooding, and water-oil flooding, the seepage mechanisms of oil and water in the reservoir core can be studied in depth, including the formation of seepage channels and the distribution of residual oil and bound water. During the experiment, the seepage of oil and water is recorded by microscopic photography, allowing for intuitive observation and analysis of the seepage process, providing an empirical basis for theoretical research. By recording experimental data such as the amount of produced fluid, the seepage process can be quantitatively analyzed, such as calculating parameters like seepage velocity and permeability, providing data support for reservoir engineering calculations and development scheme design. Through the analysis of experimental results, development schemes for shale oil reservoirs can be optimized to improve development efficiency and economic benefits.

[0023] Furthermore, the stability of pump pressure during the experiment helps to more accurately study the seepage behavior of oil and water in the reservoir. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the shale oil reservoir core micro-permeability model of the present invention; Figure 2 This is a schematic diagram of the dual-needle model of the shale oil reservoir core micro-permeability model of the present invention; Figure 3 This is a side view of the shale oil reservoir core micro-permeability model of the present invention; Figure 4 This is a physical image of a single needle in the shale oil reservoir core micro-permeability model of the present invention; Figure 5 This is a physical image of the double-needle head of the shale oil reservoir core micro-permeability model of the present invention; Figure 6 This is a diagram of the seepage channel during the water drive process in the embodiment; Figure 7 This is a diagram showing the state of bound water in the embodiment; Figure 8 This is a typical feature diagram of the water-driven oil recovery process in the microscopic model of the embodiment; Figure 9 This is a diagram showing the state of residual oil in the examples; In the figure, 1 is the rock sample; 2 is the glass slide; 3 is the glass cover plate; 4 is the needle; 5 is the inlet end; 6 is the outlet end; 7 is the first end; and 8 is the second end. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0027] In the following embodiments, unless otherwise specified, all materials used can be obtained through ordinary channels; the testing methods used are conventional methods in the art.

[0028] The micro-permeability model proposed in this invention is developed by processing real core samples to preserve the original pore structure, physical properties, and lithological characteristics of shale oil reservoirs. This model is used to simulate the seepage of fluids in shale oil reservoirs. The micro-permeability model can more realistically reflect the seepage law of shale oil reservoirs and provide a basis for the development of oil and gas fields.

[0029] like Figures 1 to 3 As shown, the present invention provides a micro-permeability model of shale oil reservoir core, including a rock sample 1. A glass slide 2 is placed on one side of the rock sample 1, and a glass cover 3 is placed on the other side. According to the pore flow direction of the rock sample 1, the side of the rock sample 1 is divided into an inflow end 5, an outflow end 6, a first end 7, and a second end 8. One or two needles are placed near the inflow end 5, and one needle is placed near the outflow end 6. The inflow end 5 and the outflow end 6 are sealed with glue at a distance of 2-3 mm from the inflow end 5 and the outflow end 6. The first end 7 and the second end 8 are sealed with glue.

[0030] In this invention, the rock sample is the core component of the micro-flow model. Fluid flow is simulated within the rock sample to study the seepage mechanism of shale oil in the reservoir. The rock sample maintains the original structure and properties of the shale oil reservoir, making the simulation results closer to reality. The rock sample is sealed with a glass slide, a glass cover plate, and adhesive to ensure that fluid can only flow into and out of the micro-flow model through the end face, preventing fluid leakage and ensuring the accuracy of the seepage model. The glass slide needs good transparency to observe the fluid seepage process within the rock sample. The inlet needle connects the seepage model to the fluid supply system to inject fluid. By adjusting the number and position of the inlet needles, fluid flow in different directions can be simulated. The outlet needle connects the seepage model to the displaced fluid collection device.

[0031] Rock sample 1 has a thickness of 0.3–0.5 mm, a length of 2.0–2.5 cm, and a width of 2.0–2.5 cm. The moderate size of the rock sample allows for faster attainment of experimental conditions while ensuring accuracy, thus shortening the experimental cycle and improving efficiency. Furthermore, the moderate size facilitates the observation and analysis of the rock's microstructure, enabling the observation of fluid movement and distribution within the rock pores. This allows for a deeper understanding of the rock's pore structure, mineral composition, and other characteristics, ensuring the accuracy of the seepage simulation experiment.

[0032] The pressure bearing capacity of the rock samples is between 0 and 1.0 MPa; the pressure bearing capacity of the rock samples can simulate the seepage process under various pressures, providing guidance for actual mining.

[0033] The length of the glass slide is 6.0~6.5cm and the width is 4.5~5.0cm. The length of the glass cover is 4.0~4.5cm and the width is 3.0~3.5cm. The dimensions of the glass slide and glass cover are set according to the size of the rock sample. The glass slide and glass cover provide protection for the rock sample.

[0034] In the micro-flow model of shale oil reservoir cores, the diameter of the needle is 0.45~0.5mm; the size of the needle can be selected according to the fluid properties and experimental requirements to ensure smooth fluid flow and accurate measurement. This invention also provides a method for preparing a microscopic seepage model of a shale oil reservoir core, comprising: S1: Preparatory rock sample When preparing rock samples, core samples from shale oil reservoirs in the study block should be selected. It is essential to ensure the representativeness of the samples to accurately reflect the true condition of the shale oil reservoirs. The crude oil in the rock samples should be washed out completely, ensuring all crude oil is extracted from the core. The extracted core samples should then be dried in an oven for later use.

[0035] S2: Preparing the slide and cover plate The slides and cover plates of this invention are made of glass slides. The selected glass slides need to have the following properties: good transparency to facilitate observation of the fluid flow process in the rock sample; high stability to ensure the stability of the micro-flow model during the experiment; and also need to have excellent strength, pressure resistance, flatness and smoothness. The glass slides need to be bonded to the rock sample, so they need to be adhesive.

[0036] Select glass slides as needed and cut them to the required size; prepare two glass slides.

[0037] Preparation of rock samples S3: Cut the prepared rock sample into a predetermined length and width of 2.0~2.5cm and 2.0~2.5cm, and grind the cut surface smooth to obtain the first surface of the rock sample; It should be noted that grinding is an important step before gluing. The surface condition of the rock sample will directly affect the gluing effect and subsequent observation. The polished surface needs to be ground until there are no obvious unevenness or cracks. S4: Clean the glass slide, apply an appropriate amount of glue to the first side of the rock sample, cover the glass slide with the first side of the rock sample, and bond the first side of the rock sample and the glass slide together with the glue. It should be noted that air bubbles must not be generated during the bonding process to avoid affecting the experimental results; at the same time, the amount of glue used needs to be controlled to avoid poor bonding results due to improper amount.

[0038] The selected adhesive must have sufficient bonding strength and should not affect the experimental results after curing. The adhesive used in this invention is prepared by mixing two types of adhesive, A and B, in a certain proportion. After preparation, it should be allowed to stand for 20-30 minutes before bonding the sheets. Letting the adhesive stand after preparation prevents it from being too fluid and clogging the end faces during bonding, and also prevents air bubbles from affecting experimental observation.

[0039] The cleaning process refers to using a lint-free cloth or cotton swab dipped in an appropriate amount of cleaning agent to gently wipe the surface of the glass slide to remove dust, grease and other impurities; after cleaning, wipe the glass slide dry with a clean cloth or paper towel to ensure that there is no residual moisture or cleaning agent on the surface.

[0040] S5: After the first side of the rock sample is pasted, let it stand for 24 to 30 hours. Then, cut the prepared rock sample with a cutting machine. The thickness of the prepared rock sample after cutting is 0.8 to 1 mm. Grind the cut surface and grind the rock sample to 0.3 to 0.5 mm through coarse grinding and fine grinding processes to obtain the second side of the rock sample. S6: Clean the glass cover plate, apply an appropriate amount of glue to the second side of the rock sample, cover the second side of the rock sample with the glass cover plate, and bond the second side of the rock sample and the glass cover plate together with the glue. S7: Use a single-edged thin blade to evenly fill the first and second ends of the rock sample with glue until the first and second ends of the rock sample are completely sealed with glue. S8: Place needles in the middle of the inflow and outflow ends near the rock sample, leaving a 1-2 mm gap between the needles and the inflow or outflow ends.

[0041] It should be noted that when a double needle is installed at the inflow end, a distance of 0.8~1.2cm should be maintained between the two needles; a gap of 1~2mm should be reserved to facilitate the flow of fluid into and out of the rock sample through the end face. This also allows the injected and outflowing fluid to travel along the seepage channels on the end face during the displacement process.

[0042] S9: Use a single-edged thin blade to evenly fill the inflow and outflow ends of the rock sample with glue, keeping a distance of about 2-3 mm between the glue and the inflow and outflow ends during the glue filling process; It should be noted that the double-needle model should not be moved arbitrarily during the glue filling process.

[0043] S10: After bonding the glass slide, glass cover plate and needle, let the rock sample stand for 24-30 hours, then seal the sides of the rock sample with adhesive again; after standing for 24-30 hours, a micro-flow model of the shale oil reservoir core is obtained, which can be used for displacement experiments.

[0044] It should be noted that the purpose of sealing the sides of the rock sample again is to ensure that the fluid can advance along the inflow and outflow ends of the rock sample under certain pressure during the displacement process.

[0045] Application of the micro-permeability model of shale oil reservoir core prepared by this invention The prepared shale oil reservoir core micro-flow model was used for displacement experiments. The required equipment included a microscopic observation system, the shale oil reservoir core micro-flow model, and a power system. The microscopic observation system includes a cold light source, a microscope, and a monitoring system. The microscope is used to observe the microscopic seepage model in the rock core, the monitoring system is used to monitor and observe the experimental process, and it also has a photographic function to record images of the entire experimental process, providing materials for subsequent research. The cold light source serves as illumination in this system.

[0046] The power system includes a power source, a pressure gauge, and a displacement pump. With a nitrogen cylinder as its core power source, the system achieves a continuous and stable driving force supply during the construction of a confined water environment and the simulation of water-driven oil displacement through precise control of the pressure gauge and the coordinated operation of the displacement pump. The precision pressure gauge has a measurement upper limit of up to 0.6 MPa, enabling accurate adjustment and monitoring of pressure levels throughout the displacement experiment, ensuring precise control of experimental conditions.

[0047] The process of using a shale oil reservoir core micro-flow model for displacement experiments includes: The microscopic seepage model of the shale oil reservoir core was photographed under a microscope to preserve the original state of the microscopic seepage model of the shale oil reservoir core. Simulated formation water with added methylene blue and simulated kerosene with added oil red were added to different intermediate containers, which were connected to the displacement pump via pipelines. Connect the inflow needle of the single-needle or double-needle shale oil reservoir core micro-permeability model to the intermediate container via a pipeline, and connect the outflow needle to the metering container via a pipeline, and set the pump pressure parameters.

[0048] The process is carried out sequentially as follows: water drive, oil drive water, and water drive oil. During the experiment, the seepage of oil and water in the shale oil reservoir core was recorded by taking photos at regular intervals, and the occurrence of residual oil and bound water in the core was observed. The amount of produced liquid was also recorded.

[0049] It should be noted that, for ease of differentiation and photography, the two liquids were added to separate intermediate containers and connected to displacement pumps. Different displacement pressures were set according to sample type and displacement time, and displacement was carried out under constant pressure. The pump pressure during water displacement was 0.02~0.50 MPa; the pump pressure during oil-water displacement was 0.02~0.80 MPa; and the pump pressure during water-oil displacement was 0.02~0.80 MPa.

[0050] Example This invention also provides a method for preparing a microscopic seepage model of a shale oil reservoir core, comprising: S1: Select shale oil reservoir cores from the study block as samples, wash the crude oil from the samples, and ensure that the crude oil in the cores is completely washed out. Dry the cores after extracting the crude oil in an oven for later use. S2: Select glass slides as needed, prepare glass slides with dimensions of 6.0×4.5cm and glass coverslips with dimensions of 3×4cm; S3: Cut the prepared rock sample into sections with a length of 2.5cm and a width of 2.5cm, and grind the cut surface smooth to obtain the first surface of the rock sample; S4: Clean the glass slide, apply an appropriate amount of glue to the first side of the rock sample, cover the glass slide with the first side of the rock sample, and bond the first side of the rock sample and the glass slide together with the glue. S5: After the first side of the rock sample is pasted, let it stand for 24 hours. Then, cut the prepared rock sample with a cutting machine. The thickness of the prepared rock sample after cutting is 0.8mm. Grind the cut surface and grind the rock sample to 0.4mm through coarse grinding and fine grinding processes to obtain the second side of the rock sample. S6: Clean the glass cover plate, apply an appropriate amount of glue to the second side of the rock sample, cover the second side of the rock sample with the glass cover plate, and bond the second side of the rock sample and the glass cover plate together with the glue. S7: After the second side of the rock sample is pasted, use a single-edged thin blade to evenly fill the first and second ends of the rock sample with glue until the first and second ends of the rock sample are completely sealed with glue. S8: Place needles in the middle of the inflow and outflow ends near the rock sample, leaving a 1mm gap between the needles and the inflow or outflow ends. The two needles at the inflow end should be 1cm apart, and the needle diameter should be 0.45mm. S9: Use a single-edged thin blade to evenly fill the inflow and outflow ends of the rock sample with glue, keeping the glue about 2mm away from the inflow and outflow ends during the filling process; S10: After bonding the glass slide, glass cover plate and needle, let it stand for 24 hours, then seal the four ends of the rock sample with glue again; after standing for 24 hours, the micro-permeability model of the shale oil reservoir core is obtained, which can be used for displacement experiments.

[0051] In this embodiment, the equipment provided by the present invention is used to conduct displacement experiments on the micro-permeability model of shale oil reservoir cores. The microscope used is a ZSA302 type microscope; the maximum range of the precision pressure gauge is 0.6 MPa.

[0052] The following is the experimental process and phenomena of oil-water two-phase flow in a microscopic seepage model of a double-needle shale oil reservoir core prepared by the method of the present invention: (1) Water drive process: First, a constant pressure of 0.03 MPa was set, and formation water with added methylene blue was slowly injected into the core micro-seepage model. The seepage channel characteristics of different types of core water-drive saturation process were observed under a microscope.

[0053] Experimental phenomena: such as Figure 6 As shown in (a), for a uniformly displaced core: during displacement, the swept area of ​​the injected water gradually expands on the plane, and the water-drive front advances almost slowly in parallel.

[0054] like Figure 6 As shown in (b), in the core of channel-like displacement, in the initial stage of water-driven saturation, it slowly advances along the entire sweep surface, and then rapidly advances along the dominant channels of fractures, advancing in a channel-like manner. The sweep area of ​​the injected water is relatively small, and fractures and microfractures become the main seepage channels.

[0055] (2) Oil-driven water displacement process A constant pressure of 0.06 MPa was set, and simulated kerosene with added oil red was slowly injected into the core micro-flow model after saturated water. This simulated the migration of oil from the source layer to the reservoir after its formation, and the oil-driven water process reflected the reservoir charging process.

[0056] Experimental phenomena: Visual observation of the oil phase flow channels and the bound water at the end of the oil drive showed that the bound water mainly exists in the pores in the following two forms. ① It adheres to the surface of pores in the form of a water film or fills smaller pores in the form of a water column; ②Water at the edges and corners, with the most droplets being water-in-oil.

[0057] like Figure 7 As shown in (a) and (c), water can be seen at the corners of the edges; as Figure 7 As shown in (b), it can be seen that water is trapped in dead pores or pores with small pores, making it difficult for oil to enter.

[0058] (3) Water flooding oil experiment process: A constant pressure of 0.06 MPa was set, and formation water with added methylene blue was slowly injected into the core under saturated oil (bound water) conditions to observe the micro-seepage flow of different types of core seepage channels and the state of residual oil.

[0059] Experimental phenomena: Characteristics of seepage channels: like Figure 8 As shown in (a) to (c), the waterflooding process and the water-driven process are generally similar in their advancement patterns for different types of cores. When oil first enters the model, formation water begins to enter uniformly in the initial displacement stage, and then spreads evenly. It slowly expands along the entire sweep surface and quickly occupies low-resistivity, high-permeability channels. like Figure 8 As shown in (d) to (f), as water flooding proceeds, the pressure gradually increases and water gradually enters the low permeability channels. However, the connectivity between the channels is poor, and only a very small number of channels are connected. The water still breaks through the model along the channels of single-phase water permeation. After the breakthrough, a large amount of injected water flows out along the waterway and does not affect the entire model, especially for the channels occupied by the oil phase. As a result, a large amount of oil is difficult to be displaced, thus forming residual oil.

[0060] Figure 8 As shown in (g) to (i), in the initial stage of displacement, water advances along the entire sweep surface; subsequently, it rapidly advances along the dominant fracture channels of water-drive and oil-drive, expanding the sweep surface; a large amount of residual oil remains in the final stage. During displacement, water advances along channels with lower resistance, exhibiting a fingering phenomenon in the plane, with a rapid breakthrough at its exit end. For laminated cores, the water-drive front area is small, and even increasing the displacement pressure makes it difficult to generate new channels. In the initial stage of displacement, water initially expands, occupies the dominant channels, and some oil is quickly driven out along the dominant channels; subsequently, water diffuses outwards along the main channels, increasing the number of oil-drive channels, and a large amount of oil film-like residual oil remains in the final state of water-drive oil.

[0061] Residual oil characteristic types: like Figure 9 As shown in (a), residual oil in the fractures can be observed: the fractures are the main seepage channels, and the crude oil stored in the fractures is the first to be displaced.

[0062] like Figure 9 As shown in (b), residual oil in pores adjacent to fractures can be observed: Since the fractures are first occupied by injected water and form high-permeability channels, the oil in the large pores adjacent to the fractures with good connectivity is then displaced by formation water. However, due to the heterogeneity of the micropore structure, the large-area poorly connected small pore groups and vertical pores are bypassed by injected water, forming sheet-like and cluster-like residual oil. This method generally results in a large amount of residual oil in the formation. like Figure 9As shown in (c) and (d), residual oil and oil film can be observed at the corners: microscopic observation shows that there are large areas of oil film in the layered cores, and there are also oil films near the fractures in the cores with developed fractures. In addition, there are also a lot of residual oil distributed at the corners after displacement.

[0063] The experimental results show that this invention can intuitively observe the occurrence state and dominant seepage channels of oil and water two-phase fluids in the core. At the same time, the preparation of the micro-seepage model of the core of the double-needle shale oil reservoir can increase the initial sweep area of ​​the fluid entering the core, which is more conducive to accurately characterizing the seepage law under formation conditions.

[0064] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A shale oil reservoir core micro-flow model, characterized in that, The sample includes a rock sample (1), with a glass slide (2) on one side and a glass cover (3) on the other side. According to the experimental design, the oil and water flow direction in the rock sample (1) is such that the sides of the rock sample (1) are the inflow end (5), the outflow end (6), the first end (7), and the second end (8). One or two needles are placed near the inflow end (5) and one needle is placed near the outflow end (6). The inflow end (5) and the outflow end (6) are sealed with glue at a predetermined distance from the inflow end (5) and the outflow end (6). The first end (7) and the second end (8) are sealed with glue.

2. The shale oil reservoir core micro-flow model according to claim 1, wherein, The thickness of rock sample (1) is 0.3~0.5mm, the length is 2.0~2.5cm, the width is 2.0~2.5cm, and the pressure bearing capacity of rock sample (1) is 0~1.0MPa.

3. The microfluidic model of a shale oil reservoir core according to claim 1, wherein, Seal with glue at a distance of 2-3 mm from the inlet end (5) and the outlet end (6).

4. The shale oil reservoir core micro-flow model of claim 1, wherein, The length of the glass slide (2) is 6.0~6.5cm and the width is 4.5~5.0cm. The length of the glass cover plate (3) is 4.0~4.5cm and the width is 3.0~3.5cm.

5. The microfluidic model of a shale oil reservoir core according to claim 1, wherein, The diameter of the needle (4) is 0.45~0.5mm.

6. A method for preparing a microcosmic percolation model of a shale oil reservoir core, characterized in that, include: Shale oil reservoir cores from the study block were selected as rock samples. The crude oil in the rock samples was completely washed out and dried to obtain prepared rock samples. The prepared rock sample is blasted to the preset length and width, and the blasted surface is ground flat to obtain the first surface of the rock sample; Apply glue to the first surface of the rock sample, cover the first surface of the rock sample with a glass slide, and bond the first surface of the rock sample and the glass slide together with glue. After the first side of the rock sample is pasted, let it stand for 24 to 30 hours. Then cut the prepared rock sample. The thickness of the prepared rock sample after cutting is 0.8 to 1 mm. Grind the cut surface to reduce the thickness of the prepared rock sample to 0.3 to 0.5 mm to obtain the second side of the rock sample. Apply glue to the second side of the rock sample, cover the second side of the rock sample with a glass cover, and bond the second side of the rock sample and the glass cover with glue. After the second side of the rock sample is pasted, fill the first and second ends of the rock sample with glue evenly until the first and second ends of the rock sample are completely sealed with glue. Place needles at the inflow and outflow ends of the rock sample, leaving a gap of 1-2 mm between the needles and the inflow or outflow ends. Fill the inflow and outflow ends of the rock sample with glue evenly, keeping the distance between the glue and the inflow and outflow ends 2-3 mm during the glue filling process. After bonding the glass slide, glass cover plate, and needle, let it stand for 24-30 hours, and then seal the sides of the rock sample with adhesive again. After standing for 24-30 hours, a micro-permeability model of the shale oil reservoir core is obtained.

7. The method for preparing a microscopic seepage model of a shale oil reservoir core according to claim 6, characterized in that, When two needles are used, the distance between the two needles should be 0.8~1.2cm.

8. The method for preparing a microscopic seepage model of a shale oil reservoir core according to claim 6, characterized in that, The adhesive is prepared by mixing two types of adhesive in a certain proportion, and then letting it stand for 20-30 minutes after preparation.

9. The use of a shale oil reservoir core micro-flow model in a displacement experiment, characterized in that, include: The microscopic seepage model of the shale oil reservoir core was photographed under a microscope to preserve the original state of the microscopic seepage model of the shale oil reservoir core. Simulated formation water with added methylene blue and simulated kerosene with added oil red were added to different intermediate containers, which were connected to the displacement pump via pipelines. The needle at the inflow end of the micro-permeability model of the shale oil reservoir core is connected to the intermediate container through a pipeline, and the needle at the outflow end is connected to the metering container through a pipeline. Pump pressure parameters are set. The process is carried out sequentially as follows: water drive, oil drive water, and water drive oil. During the experiment, photos were taken at preset times to record the seepage of oil and water in the micro-seepage model of the shale oil reservoir core, observe the occurrence state of residual oil and bound water in the core, and record the amount of produced fluid.

10. The use of a shale oil reservoir core microflow model according to claim 9 in a displacement experiment, characterized in that, The pump pressure during water-driven processes is 0.02~0.50 MPa; the pump pressure during oil-driven water processes is 0.02~0.80 MPa; and the pump pressure during water-driven oil processes is 0.02~0.80 MPa.

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