Karst cave gas reservoir formation and development microscopic dynamic conductivity simulation device and measurement method

Abstract

The invention provides a karst cave gas reservoir formation and development microscopic dynamic conductivity simulation device and a measurement method. In the device, a transparent engraved sample is arranged on a light-emitting plate; the light-emitting plate provides illumination for video recording of the transparent engraved sample; the transparent engraved sample comprises a transparent material substrate, a fluid inlet, a fluid outlet and a conductive metal strip, and a karst cave structure is engraved on the transparent material substrate; the constant fluid pump injects gas or a salt solution into the transparent sculpture sample; the fluid recovery device is used for collecting gas or a salt solution flowing out of the transparent carving sample and recycling the gas or the salt solution; the resistivity measuring device measures the resistivity of the transparent engraved sample; the video recording device records the flowing and distribution conditions of gas and water in the transparent engraved sample in the experiment process. According to the invention, gas-water distribution in different water saturation states and resistivity in corresponding states can be obtained, and research on seepage characteristics of natural gas in reservoir forming and development stages and electric conduction rules corresponding to different two-phase gas-water distribution characteristics can be better simulated.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas exploration and development, and more particularly to a microscopic dynamic conductivity simulation device and a measurement method for the accumulation and development of cave gas reservoirs. Background Art

[0002] In the field of natural gas exploration and development, the development of cave reservoirs is a key goal, especially in deep and ultra-deep natural gas formations. Currently, significant progress has been made in the exploration and development of natural gas in cave reservoirs in areas such as the Sichuan Basin, Tarim Basin, and Ordos Basin, and significant potential remains. During the exploration and development of cave reservoirs, the study of gas-water distribution and electrical conductivity plays a crucial role in determining and deciding on a range of factors, including reservoir delineation, fluid property assessment, gas saturation calculation, and development plan formulation.

[0003] Currently, techniques for studying gas-water distribution and electrical conductivity can be categorized into two main categories: experimental methods and numerical simulations. Experimental methods primarily include gas-water relative permeability experiments, gas-water displacement nuclear magnetic resonance experiments, and rock electrical experiments. However, these methods can only determine gas-water distribution patterns or electrical conductivity patterns, and are unable to simultaneously measure resistivity while simultaneously capturing gas-water distribution. Numerical simulations can determine gas-water distribution and electrical conductivity patterns through sequential gas-water permeability simulations and then gas-water electrical conductivity simulations. However, these simulations consider relatively limited factors and cannot fully reproduce the true subsurface conditions, resulting in significant deviations from reality and less reliable results than experimental results. Furthermore, both existing experimental and numerical simulation techniques ignore the differences in gas-water distribution characteristics between exploration and development, as well as the differences in electrical conductivity corresponding to these distributions. This presents significant challenges for the exploration and development of cave reservoirs. Therefore, there is an urgent need for a technical solution that can simulate the natural gas accumulation and development state in cave reservoirs, dynamically observe gas-water distribution characteristics at a microscopic level, and simultaneously measure electrical conductivity. Summary of the Invention

[0004] The purpose of the present invention is to provide a micro-dynamic conductivity simulation device and measurement method for the formation and development of cave gas reservoirs. By conducting micro-dynamic gas-water displacement experiments on specific samples, the gas-water distribution under different water saturation states and the resistivity under the corresponding states are obtained, so as to better simulate the seepage characteristics of natural gas in the formation and development stages and the conductivity laws corresponding to different two-phase gas-water distribution characteristics.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A microscopic dynamic conductivity simulation device for cave gas reservoir formation and development, comprising: a transparent engraved sample, a light-emitting plate, a constant fluid pump, a resistivity measuring device, a fluid recovery device, and a video recording device;

[0007] The transparent engraved sample is arranged on the light emitting plate;

[0008] The light-emitting panel is used to provide lighting for the video recording of the transparent engraved sample;

[0009] The transparent engraving sample comprises a transparent material substrate and a fluid inlet, a fluid outlet and a conductive metal strip arranged inside the transparent material substrate, wherein the transparent material substrate is used for engraving a cave structure;

[0010] The constant fluid pump is connected to the fluid inlet through a fluid conduit and is used to inject fluid into the transparent engraving sample, wherein the fluid is gas or salt solution;

[0011] The fluid recovery device is connected to the fluid outlet through a fluid conduit, and is used to collect the fluid flowing out of the transparent engraving sample and recycle it;

[0012] The resistivity measuring device is electrically connected to the conductive metal strip via a wire and is used to measure the resistivity of the transparent engraved sample;

[0013] The video recording device is used to record the flow and distribution of air and water in the transparent sculpture sample during the experiment.

[0014] Furthermore, the method for preparing the transparent engraving sample comprises the following steps:

[0015] Extracting the cave network: Obtain microscopic photographs of the cave reservoir to be measured and mercury injection curve data of the same core; Obtain the cave structure through image processing based on the microscopic photographs; Obtain the throat radius distribution based on the mercury injection curve data and determine the main throat radius range; Based on the main throat radius range, connect the cave structure to obtain the cave network;

[0016] Carving the karst cave network: Using the karst cave network as a template, carving is performed on a transparent carving base plate made of transparent material to obtain the karst cave carving area, and carving the fluid inlet, fluid outlet and installation space of the conductive metal strip;

[0017] Installing the conductive metal strip: embedding the conductive metal strip into the installation space;

[0018] Making a transparent upper cover plate: using the same transparent material as the transparent engraving base plate to make a transparent upper cover plate, the transparent upper cover plate has the same length and width as the transparent engraving base plate, and two fluid conduit interfaces are reserved;

[0019] Bonding the bottom plate and the cover plate: Bond the transparent engraving bottom plate and the transparent upper cover plate together to obtain a transparent material substrate. The transparent engraving bottom plate and the non-engraving area of the transparent upper cover plate are completely sealed, there are no bubbles inside, and the connection of the cave engraving area is unobstructed, maintaining a transparent state.

[0020] Furthermore, the microscopic photographs include CT two-dimensional slice images and casting thin section photographs; the method for determining the main throat radius range is: first determine the throat radius peak, and then expand the radius range left and right until the pore volume percentage controlled by the selected range throat exceeds 50%.

[0021] The present invention also provides a method for measuring the microscopic dynamic conductivity of the formation and development of a karst cave gas reservoir, which is applied to the above-mentioned karst cave gas reservoir formation and development microscopic dynamic conductivity simulation device, comprising the following steps:

[0022] Based on the cave structure of the cave reservoir to be measured, a transparent engraved sample is prepared, and a microscopic dynamic conductivity simulation device for the formation and development of cave gas reservoirs is assembled;

[0023] Simulations were carried out in sequence during the initial deposition phase, the natural gas accumulation phase, and the development phase. During the simulations, microscopic dynamic gas-water displacement experiments were conducted on the transparent sculpture samples to obtain images of the transparent sculpture samples under different gas-water displacement states and the resistivity of the corresponding states.

[0024] Based on the images of transparent engraved samples under different gas-water displacement states, the microscopic gas-water distribution state and the corresponding water saturation are obtained. Combined with the resistivity of the corresponding state, the resistivity-water saturation cross-plot is drawn;

[0025] Based on the resistivity-water saturation cross-plot, the conductivity law of each simulation stage was obtained.

[0026] Furthermore, the simulations of the initial deposition stage, the natural gas accumulation stage, and the development stage are sequentially performed. During the simulations, a microscopic dynamic gas-water displacement experiment is conducted on the transparent sculpture sample, specifically including:

[0027] At the beginning of the simulated deposition, salt solution was passed through the transparent engraved sample to prepare a fully saturated sample, which laid the foundation for subsequent experiments.

[0028] Entering the stage of simulating natural gas accumulation, dry gas is used to displace the salt solution to dynamically simulate the accumulation stage. A video device is used to record the gas and water distribution under different states from the initial stage of accumulation in the fully saturated state to the final stage of accumulation in the bound water state. The resistivity under each state is also measured.

[0029] Next, the natural gas development stage was dynamically simulated. The gas was displaced by salt solution, the gas-water distribution from the early to the end of the development was recorded with a video device, and the resistivity of the corresponding state was measured with a resistivity measuring device.

[0030] Furthermore, during the experiment, the light-emitting board was fixed on a horizontal platform and adjusted to a set brightness, and the transparent carved sample was placed in the center of the light-emitting board; a video recording device was installed directly above the transparent carved sample so that the cave carving area of the transparent carved sample was completely in the center of the video field of view and the captured image was clear.

[0031] Furthermore, the dry air and salt solution are used to simulate natural gas and formation water in the natural gas accumulation and development stages, respectively.

[0032] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the present invention provides a micro-dynamic conductivity simulation device and measurement method for the formation and development of cave gas reservoirs, wherein the simulation device includes a transparent engraved sample, a light-emitting plate, a constant fluid pump, a resistivity measuring device, a fluid recovery device and a video recording device, etc., which provides a simple and easy-to-operate device for simulating the formation and development stage of natural gas in cave reservoirs; the simulation device can be used to simulate the microscopic gas-water distribution under different water saturation states in the formation and development stage of natural gas in cave reservoirs, and simultaneously measure and analyze the electrical characteristics under the corresponding states, providing a basis for decisions such as cave reservoir division, fluid property judgment, gas saturation calculation, and development plan formulation.

[0033] The microscopic dynamic conductivity measurement method described in this invention prepares a transparent engraved sample based on the cave structure of the cave reservoir to be measured. Microscopic dynamic gas-water displacement experiments are then conducted on this sample to determine the gas-water distribution and corresponding resistivity at different water saturations. This method better simulates the seepage characteristics of natural gas during its accumulation and development stages, studying the conductivity patterns associated with different two-phase gas-water distribution characteristics. This method provides a stable and simple method for simultaneously obtaining two-phase seepage characteristics and resistivity observations in fields such as underground natural gas resource development. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a schematic structural diagram of the microscopic dynamic conductivity simulation device for cave gas reservoir formation and development according to the present invention;

[0036] Figure 2Schematic diagram of the cave network extraction process of the present invention; wherein A represents the original slice image, B represents the original mercury injection curve, C represents the cave structure obtained by image processing, D represents the throat radius distribution, and E represents the cave network;

[0037] Figure 3 This is a schematic diagram of the transparent engraving sample structure of the present invention;

[0038] Figure 4 Flowchart of the method for measuring microscopic dynamic conductivity of cave gas reservoir formation and development according to the present invention; wherein A represents the simulated initial deposition stage, B represents the simulated gas reservoir formation stage, C represents the simulated gas reservoir development stage, and D represents the data analysis and processing steps;

[0039] Figure 5 The resistivity-water saturation cross-plot and gas-water distribution diagram for the natural gas accumulation and development stages of the present invention are shown. ①, ②, ③, ④, and ⑤ simulate the gas-water distribution at successively lower water saturations during the gas accumulation stage; ⑥, ⑦, ⑧, ⑨, and ⑩ simulate the gas-water distribution at successively higher water saturations during the gas development stage.

[0040] Figure 6 This is a schematic diagram of the process for extracting a cave network from a cave-type carbonate reservoir in a certain region according to an embodiment of the present invention; wherein A represents the original slice image, B represents the original mercury injection curve, C represents the cave structure obtained by image processing, D represents the throat radius distribution, and E represents the cave network;

[0041] Figure 7 Schematic diagram of gas-water distribution in simulated initial deposition stage, simulated gas reservoir formation stage, and simulated gas reservoir development stage of a cave-type carbonate reservoir in a certain region according to an embodiment of the present invention;

[0042] Figure 8 Figure 1 shows a resistivity-water saturation crossplot and a gas-water distribution diagram for the natural gas accumulation and development stages of a karst-type carbonate reservoir in a certain region according to an embodiment of the present invention. (A) shows the simulated gas-water distribution at different water saturations during the gas reservoir formation stage; (B) shows the resistivity-water saturation crossplot; and (C) shows the simulated gas-water distribution at different water saturations during the gas reservoir development stage.

[0043] Explanation of reference numerals: 1. transparent engraved sample; 2. light-emitting plate; 3. constant fluid pump; 4. resistivity measuring device; 5. fluid recovery device; 6. video recording device; 7. fluid pipeline; 8. wire;

[0044] 1-1, transparent engraving base plate; 1-1-1, cave engraving area; 1-1-2, fluid inlet and outlet area; 1-2, conductive metal strip; 1-3, transparent upper cover plate; 1-3-1, fluid conduit interface. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Although existing rock electrical experimental methods can measure core resistivity, they cannot observe the gas and water distribution status within the cave; existing visualization displacement models can observe the gas and water distribution status within the cave, but cannot simultaneously measure resistivity. To solve the problems existing in the existing technology, the present invention proposes a micro-dynamic conductivity simulation device and measurement method for the formation and development of cave gas reservoirs, which can simultaneously observe the gas and water distribution characteristics within the cave while measuring the resistivity.

[0047] The present invention extracts real cave structures, prepares them into transparent sculptured samples, and conducts gas-water displacement and resistivity experiments at the same scale as underground rocks, thereby simulating the relationship between resistivity, water saturation and gas-water distribution characteristics in the natural gas accumulation stage and the natural gas development stage.

[0048] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] like Figure 1 As shown, the microscopic dynamic conductivity simulation device for cave gas reservoir formation and development provided by the present invention includes: a transparent engraved sample 1, a light-emitting plate 2, a constant fluid pump 3, a resistivity measuring device 4, a fluid recovery device 5 and a video recording device 6;

[0050] The transparent engraved sample 1 is set on the light-emitting plate 2;

[0051] The light emitting panel 2 is used to provide lighting for the video recording of the transparent engraved sample 1;

[0052] The transparent engraving sample 1 includes a transparent material substrate and a fluid inlet, a fluid outlet and a conductive metal strip arranged inside the transparent material substrate, wherein the transparent material substrate is used to engrave a cave structure;

[0053] The constant fluid pump 3 is connected to the fluid inlet through a fluid conduit 7 and is used to inject gas or salt solution into the transparent engraving sample;

[0054] The fluid recovery device 5 is connected to the fluid outlet through a fluid conduit 7 and is used to collect the gas or salt solution flowing out of the transparent engraving sample and recycle it;

[0055] The resistivity measuring device 4 is electrically connected to the conductive metal strip via a wire 8 and is used to measure the resistivity of the transparent engraved sample;

[0056] The video recording device 6 is used to record the flow and distribution of air and water in the transparent sculpture sample 1 during the experiment.

[0057] The method for preparing the transparent engraved sample comprises the following steps:

[0058] (1) Extracting the cave network: Prepare a representative microscopic photograph of the cave reservoir to be measured (e.g., CT two-dimensional slice image, casting thin section photo, etc.). Figure 2 As shown in A), the mercury injection curve data of the same core (as shown in Figure 2 Based on the microscopic photos of the cave reservoir, the cave structure (as shown in B) was obtained by image processing. Figure 2 Based on the mercury injection curve data, the throat radius distribution is obtained, and the main throat radius range is determined (first determine the throat radius peak, and then expand the radius range left and right until the pore volume percentage controlled by the selected range throat exceeds 50%, as shown in Figure 2). Figure 2 Referring to the main throat radius range determined by mercury injection curve data, the cave structures obtained by image processing are connected to obtain the final cave network (as shown in Figure 2). Figure 2 (as shown in E).

[0059] (2) Carved cave network: e.g. Figure 3 As shown, on a transparent engraving base plate 1-1 made of transparent material, the final cave network is used as a template and engraving technology (mechanical engraving, laser engraving, chemical engraving) is used to obtain the cave engraving area 1-1-1; the fluid inlet and outlet area 1-1-2 is further engraved, and the installation space of 4 conductive metal strips 1-2 is engraved in this area.

[0060] (3) Install conductive metal strips: Figure 3 As shown, a metal material with strong conductivity (gold, copper, aluminum alloy, etc.) is selected and processed into a conductive metal strip 1-2 with the same height and width as the reserved space but a larger length, which is completely embedded in the installation space reserved in the fluid inlet and outlet area 1-1-2, and ensures that the conductive metal strip 1-2 does not block the inflow and outflow of the fluid.

[0061] (4) Make a transparent upper cover plate: Figure 3 As shown, the transparent upper cover plate 1-3 is made of the same transparent material as the transparent engraving base plate 1-1. The length and width of the transparent upper cover plate 1-3 are exactly the same as those of the transparent engraving base plate 1-1, and two fluid conduit interfaces 1-3-1 are reserved.

[0062] (5) Bonding the base plate and the cover plate: Adopting gluing or high-temperature fusion technology, the transparent engraving base plate 1-1 and the transparent upper cover plate 1-3 are bonded together to obtain a transparent material substrate. The transparent engraving base plate and the non-engraving area of the transparent upper cover plate are completely sealed, there are no bubbles inside, and the connection of the cave engraving area is unobstructed, maintaining a transparent state.

[0063] like Figure 4 As shown, the present invention also provides a method for measuring the microscopic dynamic conductivity of the formation and development of cave gas reservoirs, which is applied to the above-mentioned microscopic dynamic conductivity simulation device for the formation and development of cave gas reservoirs, and includes the following steps:

[0064] Based on the cave structure of the cave reservoir to be measured, a transparent engraved sample is prepared, and a microscopic dynamic conductivity simulation device for the formation and development of cave gas reservoirs is assembled;

[0065] Simulations were carried out in sequence during the initial deposition phase, the natural gas accumulation phase, and the development phase. During the simulations, microscopic dynamic gas-water displacement experiments were conducted on the transparent sculpture samples to obtain images of the transparent sculpture samples under different gas-water displacement states and the resistivity of the corresponding states.

[0066] Based on the images of transparent engraved samples under different gas-water displacement states, the microscopic gas-water distribution state and the corresponding water saturation are obtained. Combined with the resistivity of the corresponding state, the resistivity-water saturation cross-plot is drawn;

[0067] Based on the resistivity-water saturation cross-plot, the conductivity law of each simulation stage was obtained.

[0068] Specifically, the microscopic dynamic conductivity measurement methods for cave gas reservoir formation and development include:

[0069] Before beginning experimental measurements, prepare the fluids required for the simulation phase (e.g., dry air, saline solution, etc.). Connect and build the karst gas reservoir formation and development micro-dynamic conductivity simulation device and confirm its operation. Ensure that the karst engraving area of the transparent engraved sample is completely centered in the video field of view, and the captured image is clear.

[0070] First, during the initial stage of simulated deposition, fully saturated samples were prepared using a saline solution to lay the foundation for subsequent experiments. Entering the simulated natural gas accumulation phase, dry gas was used to displace the saline solution, dynamically simulating the accumulation phase. A video recording device was used to record the gas-water distribution under different states, from the initial stage of accumulation (fully saturated) to the final stage of accumulation (bound water), while simultaneously measuring the resistivity under each state. Next, during the dynamic simulation of the natural gas development phase, saline solution was used to displace the gas, and a video recording device was used to record the gas-water distribution and corresponding resistivity from the initial to the final stage of development. By statistically analyzing the images captured by the video device, different water saturations (Sw or Sw') were obtained based on the images of different gas-water distribution states. Based on the measured resistivity (R or R') corresponding to the corresponding gas-water distribution state, a resistivity-water saturation crossplot (R-Sw crossplot) was plotted.

[0071] like Figure 5 As shown in the figure, based on images of the transparent engraved sample under different displacement states, the microscopic gas-water distribution state is obtained. Simultaneously, based on the images of the transparent engraved sample under different displacement states, the corresponding water saturation (Sw or Sw') is obtained through image processing. Combined with the resistivity (R or R') data measured under different distribution states, a resistivity-water saturation crossplot (R-Sw crossplot or R'-Sw' crossplot) is plotted. Based on the plotted crossplots, the conductivity patterns of each simulation stage are obtained. Here, Sw and R simulate the water saturation and resistivity during the gas reservoir formation stage, respectively, while Sw' and R' simulate the water saturation and resistivity during the gas reservoir development stage, respectively.

[0072] Example

[0073] This invention takes a certain area's karst-type carbonate reservoir as an example to demonstrate the specific implementation of the microscopic dynamic conductivity measurement method for simulating natural gas accumulation and development:

[0074] (1) Overall device structure

[0075] according to Figure 1 As shown, a microscopic dynamic conductivity simulation device for cave gas reservoir formation and development was constructed. A light-emitting panel was fixed to a horizontal platform and adjusted to an appropriate brightness. A transparent engraved sample was placed in the center of the light-emitting panel. A constant fluid pump was connected to the fluid conduit interface at the fluid inlet area of the transparent engraved sample, and a fluid recovery device was connected to the fluid conduit interface at the fluid outlet area of the transparent engraved sample. A resistivity measurement device was connected to a conductive metal strip embedded in the transparent engraved sample. A video recording device was installed directly above the transparent engraved sample, ensuring that the engraved cave area of the transparent engraved sample was completely centered in the video field of view and that the captured image was clear.

[0076] (2) Preparation and structure of transparent engraving samples

[0077] Follow the above 5 steps to complete the preparation of the transparent engraving sample.

[0078] ① Cave network extraction

[0079] Select a representative CT two-dimensional slice image of a cave-type carbonate rock in a certain area, cut out an image area with a length of 3 cm and a width of 2 cm (such as Figure 6 After processing the image, the cave structure (as shown in A) is obtained. Figure 6 Using the mercury injection curve data of the same core (as shown in C). Figure 6 B), and obtain the throat radius distribution (e.g. Figure 6 D). In the throat radius distribution, find the peak value of 200μm of the throat radius and expand the radius range to the left and right. When the left and right boundaries are expanded to 160μm and 240μm respectively, the pore volume percentage controlled by the selected range throat reaches 57% (this value is just over 50%), thus determining the throat radius range to be 160-240μm. Referring to the main throat radius range of 160-240μm determined by the mercury injection curve data, the cave structure obtained by image processing (such as Figure 6 C) to connect and obtain the final cave network (such as Figure 6 Middle E).

[0080] ②Transparent cave network carving

[0081] Transparent resin is selected as the material for transparent engraving samples. Figure 6 Using (E) as a template, an engraving technique was used to create a cave engraving area. The fluid inlet and outlet areas were then engraved, and spaces for four conductive metal strips were carved into this area. The transparent engraving base of the transparent engraving sample was 9 cm long, 3 cm wide, and 0.5 cm thick. The cave engraving area was 3 cm long, 2 cm wide, and 50 μm deep. The four reserved spaces for the conductive metal strips in the fluid inlet and outlet areas were each 2 cm long, 0.5 cm wide, and 50 μm deep, located at the edge of the cave engraving area and 0.7 cm from the edge. Trapezoidal fluid inlet and outlet areas with a depth of 50 μm were engraved on the left and right sides of the cave engraving area. Circular fluid inlet and outlet areas with a radius of 0.5 cm and a depth of 50 μm were engraved, centered 1 cm from each end of the trapezoidal inlet and outlet areas. A fluid channel with a length of 0.5 cm, a width of 0.5 cm, and a depth of 50 μm was engraved between the trapezoidal and circular fluid inlet and outlet areas.

[0082] ③Installation of conductive metal strips

[0083] The conductive metal strip is made of a gold-plated nickel-chromium alloy with a length of 4.5 cm, a width of 0.5 cm, and a height of 10 μm. The conductive metal strip is completely embedded in the installation space reserved for the fluid inlet and outlet areas, ensuring that the conductive metal strip does not block the inflow and outflow of fluid.

[0084] ④Production of transparent upper cover plate

[0085] A transparent upper cover plate is made from the same transparent resin material as the engraving base. The transparent upper cover plate is 9 cm long, 3 cm wide, and 0.5 cm thick (identical to the length and width of the transparent engraving base plate). Two fluid conduit ports are reserved. These are hollow cylinders with a height of 1 cm, an outer diameter of 1 cm, and an inner diameter of 0.6 cm.

[0086] ⑤Bonding of base plate and cover plate

[0087] High-temperature fusion technology is used to bond the base plate and cover plate together, ensuring that the non-engraving areas of the base plate and cover plate are completely sealed without bubbles inside, while the engraving area remains unobstructed and transparent.

[0088] (3) Experimental process

[0089] Prepare the required fluids for the experiment (dry air and a saline solution with the same salinity as the formation water in a specific area). The dry air and saline solution simulate natural gas and formation water during the reservoir formation and development phases, respectively. Ensure that the cave carving area of the transparent carving sample is completely centered in the video field of view, and the captured image is clear.

[0090] First, at the initial stage of simulated deposition, the transparent sculpture sample is completely immersed in a salt solution to achieve a fully saturated state, thus laying the foundation for subsequent experiments. In the dynamic simulation of gas reservoir formation, dry air is injected into the transparent sculpture sample at a constant rate to displace the salt solution. A video device is used to record from the initial stage of formation (fully saturated state). During the displacement process, if a characteristic state appears, it is necessary to capture an image and record the gas-water distribution in that state. At the same time, the resistivity in that state is measured until the gas-water distribution does not change, indicating that the displacement has reached the end of formation (bound water state). The image of the bound water state is recorded, and the resistivity of the bound water state is measured. Then, the second step of the experiment is entered. In the dynamic simulation of gas reservoir development, the salt solution is used to displace the air in the transparent sculpture sample at a constant rate. A video device is used to record from the initial stage of development until the gas-water distribution does not change, indicating that the displacement has reached the end of development (residual gas state). The gas-water distribution at the end is recorded and the resistivity of the corresponding state is measured. Finally, the images of the video device during the experiment are statistically analyzed to obtain the gas-water distribution in different states of the simulated gas reservoir formation stage and the gas reservoir development stage, as shown in the figure. Figure 7As shown in the figure, in the simulated initial deposition stage, the water saturation is 100% in the original state; in the simulated gas reservoir formation stage, the water saturation gradually decreases to 93.2%, 63.4%, and 45.4%; in the simulated gas reservoir development stage, the water saturation gradually increases to 48.5%, 57.3%, and 80.4%.

[0091] (4) Data analysis and processing

[0092] Based on the images of different gas-water distribution states obtained in the experiment, the microscopic gas-water distribution state is obtained; at the same time, based on the images of different gas-water distribution states obtained in the experiment, the water saturation (Sw or Sw') of the corresponding state is obtained through image processing; combined with the resistivity (R or R') data of different gas-water distribution states that have been measured, Sw and R respectively simulate the water saturation and resistivity in the gas reservoir formation stage, and Sw' and R' respectively simulate the water saturation and resistivity in the gas reservoir development stage; draw the resistivity-water saturation cross-plot, such as Figure 8 (C), and obtain the following rules:

[0093] ① Laws in the gas reservoir formation stage: When dry air displaces saline solution, air occupies the dominant channel and part of the saline solution occupies the narrow channel. As the water saturation of the sample decreases, the resistivity of the sample increases rapidly.

[0094] ② Rules in the gas reservoir development stage: When the saline solution displaces the air, the saline solution reoccupies the dominant channel. As the water saturation of the sample increases, the resistivity of the sample slowly decreases.

[0095] ③ Comparison of the patterns between the gas reservoir formation stage and the gas reservoir development stage: The resistivity (R) and water saturation (Sw) trend line in the gas reservoir formation stage is above the resistivity (R') and water saturation (Sw') trend line in the gas reservoir development stage. Under the same water saturation conditions, the greater the resistivity difference between the gas reservoir formation stage and the gas reservoir development stage, the greater the difference in gas-water distribution between the gas reservoir formation stage and the gas reservoir development stage.

[0096] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A microscopic dynamic conductivity simulation device for cave gas reservoir formation and development, characterized in that: include: Transparent engraved sample, luminous plate, constant fluid pump, resistivity measuring device, fluid recovery device and video recording device; The transparent engraved sample is arranged on the light emitting plate; The light-emitting panel is used to provide lighting for the video recording of the transparent engraved sample; The transparent engraving sample comprises a transparent material substrate and a fluid inlet, a fluid outlet and a conductive metal strip arranged inside the transparent material substrate, wherein the transparent material substrate is used for engraving a cave structure; The constant fluid pump is connected to the fluid inlet through a fluid conduit and is used to inject fluid into the transparent engraving sample, wherein the fluid is gas or salt solution; The fluid recovery device is connected to the fluid outlet through a fluid conduit, and is used to collect the fluid flowing out of the transparent engraving sample and recycle it; The resistivity measuring device is electrically connected to the conductive metal strip via a wire and is used to measure the resistivity of the transparent engraved sample; The video recording device is used to record the flow and distribution of air and water in the transparent sculpture sample during the experiment.

2. The microscopic dynamic conductivity simulation device for cave gas reservoir formation and development according to claim 1 is characterized in that: The method for preparing the transparent engraving sample comprises the following steps: Extracting the cave network: Obtain microscopic photographs of the cave reservoir to be measured and mercury injection curve data of the same core; Obtain the cave structure through image processing based on the microscopic photographs; Obtain the throat radius distribution based on the mercury injection curve data and determine the main throat radius range; Based on the main throat radius range, connect the cave structure to obtain the cave network; Carving the karst cave network: Using the karst cave network as a template, carving is performed on a transparent carving base plate made of transparent material to obtain the karst cave carving area, and carving the fluid inlet, fluid outlet and installation space of the conductive metal strip; Installing the conductive metal strip: embedding the conductive metal strip into the installation space; Making a transparent upper cover plate: using the same transparent material as the transparent engraving base plate to make a transparent upper cover plate, the transparent upper cover plate has the same length and width as the transparent engraving base plate, and two fluid conduit interfaces are reserved; Bonding the bottom plate and the cover plate: Bond the transparent engraving bottom plate and the transparent upper cover plate together to obtain a transparent material substrate. The transparent engraving bottom plate and the non-engraving area of the transparent upper cover plate are completely sealed, there are no bubbles inside, and the connection of the cave engraving area is unobstructed, maintaining a transparent state.

3. The microscopic dynamic conductivity simulation device for cave gas reservoir formation and development according to claim 2 is characterized in that: The microscopic photos include CT two-dimensional slice images and casting thin section photos; the method for determining the main throat radius range is: first determine the throat radius peak, and then expand the radius range left and right until the pore volume percentage controlled by the selected range throat exceeds 50%.

4. A method for measuring the microscopic dynamic conductivity of the formation and development of a karst cave gas reservoir, applied to the microscopic dynamic conductivity simulation device for the formation and development of a karst cave gas reservoir according to any one of claims 1 to 3, characterized in that: The steps include: Based on the cave structure of the cave reservoir to be measured, a transparent engraved sample is prepared, and a microscopic dynamic conductivity simulation device for the formation and development of cave gas reservoirs is assembled; Simulations were carried out in sequence during the initial deposition phase, the natural gas accumulation phase, and the development phase. During the simulations, microscopic dynamic gas-water displacement experiments were conducted on the transparent sculpture samples to obtain images of the transparent sculpture samples under different gas-water displacement states and the resistivity of the corresponding states. Based on the images of transparent engraved samples under different gas-water displacement states, the microscopic gas-water distribution state and the corresponding water saturation are obtained. Combined with the resistivity of the corresponding state, the resistivity-water saturation cross-plot is drawn; Based on the resistivity-water saturation cross-plot, the conductivity law of each simulation stage was obtained.

5. The method for measuring microscopic dynamic conductivity of cave gas reservoir formation and development according to claim 4 is characterized in that: The simulations of the initial deposition stage, the natural gas accumulation stage, and the development stage are carried out in sequence. During the simulation process, a microscopic dynamic gas-water displacement experiment is carried out on the transparent sculpture sample, specifically including: At the beginning of the simulated deposition, salt solution was passed through the transparent engraved sample to prepare a fully saturated sample, which laid the foundation for subsequent experiments. Entering the stage of simulating natural gas accumulation, dry gas is used to displace the salt solution to dynamically simulate the accumulation stage. A video device is used to record the gas and water distribution under different states from the initial stage of accumulation in the fully saturated state to the final stage of accumulation in the bound water state. The resistivity under each state is also measured. Next, the natural gas development stage was dynamically simulated. The gas was displaced by salt solution, the gas-water distribution from the early to the end of the development was recorded with a video device, and the resistivity of the corresponding state was measured with a resistivity measuring device.

6. The method for measuring microscopic dynamic conductivity of cave gas reservoir formation and development according to claim 4, characterized in that: During the experiment, the light-emitting board was fixed on a horizontal platform and adjusted to a set brightness, and the transparent carved sample was placed in the center of the light-emitting board; a video device was installed directly above the transparent carved sample so that the cave carved area of the transparent carved sample was completely in the center of the video field of view and the captured image was clear.

7. The method for measuring microscopic dynamic conductivity of cave gas reservoir formation and development according to claim 4, characterized in that: The dry air and salt solution are used to simulate natural gas and formation water in the natural gas accumulation and development stages, respectively.

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