Preparation method of compact stripe stratified rock sample and analysis method and system of fracturing process

Abstract

The embodiment of the invention provides a preparation method of a compact stripe stratified rock sample and an analysis method and system of a fracturing process, and belongs to the field of oil and gas field reservoir fracturing. The preparation method comprises the following steps: placing a target amount of epoxy resin in a sample preparation device; heating and stirring the epoxy resin in a set atmosphere until the epoxy resin expands and fills the sample preparation device and the proportion of bubbles reaching the nano-micron level in the epoxy resin is greater than a set value, so as to obtain a liquid epoxy resin sample; cooling and demolding the epoxy resin sample by setting a mold to obtain a solid epoxy resin plate; and pressurizing and laminating the plurality of epoxy resin plates to obtain the compact stripe layered rock sample comprising the distributed optical fibers. The actual porosity of the prepared rock sample is close to the actual porosity of a reservoir, and a natural bedding seam structure can be simulated. Meanwhile, rock samples with different shapes and sizes can be customized according to experiment requirements, and the universality of the prepared rock samples in experiments is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field reservoir fracturing technology, specifically to a method for preparing dense layered rock samples, an analytical method for the fracturing process, and a system. Background Technology

[0002] With the in-depth development of conventional oil and gas reservoirs, their recoverable reserves are decreasing year by year, and the development of unconventional oil and gas reservoirs has attracted much attention in recent years. In particular, tight layered reservoirs, due to their extremely high degree of natural bedding fracture development, provide a natural advantage for the formation of volumetric fracture networks. However, the mechanisms of fracture initiation and cross-layer deflection during hydraulic fracturing are still unclear, leading to a bottleneck in the study of fracture propagation and proppant migration, which urgently needs to be addressed.

[0003] Hydraulic fracturing physical simulation experiments are a crucial and direct method for studying fracture initiation and propagation mechanisms. However, accurately describing the fracture initiation, propagation, and support migration behavior during the experimental process remains a challenge. Laboratories often employ dynamic CT and acoustic emission techniques to monitor the fracturing process, but these methods are limited by research costs and equipment limitations, preventing precise descriptions of the fracturing process. Additionally, some researchers have begun using CT 3D imaging and 3D printing to "carve" reservoir pore structures within epoxy resin for experimental research. However, this approach is not only costly but also fails to simulate the natural bedding fractures of dense, layered reservoirs. Furthermore, 3D printing technology cannot "carve" nano- or micron-sized pores within epoxy resin. Moreover, the distribution of pores and natural bedding fractures in actual reservoirs exhibits high randomness, making this "replica" rock sample preparation technique unsatisfactory in simulating the actual reservoir fracturing process. Therefore, there is an urgent need to explore a method for preparing visualized dense layered rock samples that can simulate micro- and nano-scale pores and natural bedding fractures, with pores randomly distributed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing dense, layered rock samples, an analytical method for the fracturing process, and a system. The prepared rock samples have a porosity close to that of the actual reservoir and can also simulate the structure of natural bedding fractures. Furthermore, this invention can be customized to produce rock samples of different shapes and sizes according to experimental needs, greatly improving the versatility of the prepared rock samples in experiments.

[0005] To achieve the above objectives, embodiments of the present invention provide a method for preparing a dense layered rock sample. The method includes: placing a target amount of epoxy resin in a sample mixing device, wherein the target amount of epoxy resin is determined based on the volume of the sample mixing device and the target reservoir porosity; heating and stirring the epoxy resin under a set atmosphere until the epoxy resin expands and fills the sample mixing device and the proportion of nano-micron level bubbles in the epoxy resin is greater than a set value, to obtain a liquid epoxy resin sample; cooling and demolding the epoxy resin sample through a set mold to obtain a solid epoxy resin plate, wherein the set mold includes a through hole for placing distributed optical fibers; and pressing and bonding multiple epoxy resin plates together to obtain a dense layered rock sample including the distributed optical fibers.

[0006] Optionally, determining the target amount of epoxy resin includes: determining the target amount of epoxy resin V2 based on the volume V1 of the sample dispenser and the target reservoir porosity θ using the following formula: V2 = V1 × (100% - θ).

[0007] Optionally, the sample preparation device includes a sealing cap, an air inlet, and an exhaust outlet, wherein the set atmosphere is obtained by injecting inert gas into the air inlet and discharging air from the exhaust outlet.

[0008] Optionally, the sample dispenser includes at least one set of annular blades, and the heating and stirring of the epoxy resin under a set atmosphere includes: stirring the epoxy resin at a first rotational speed through the at least one set of annular blades; and / or rotating the sample dispenser at a second rotational speed, wherein the ratio of the first rotational speed to the second rotational speed is 50-80.

[0009] Optionally, the mold is a detachable type, including a sample inlet and an exhaust outlet, and the inner wall of the mold is covered with a heat-resistant film.

[0010] Optionally, before pressing and bonding the plurality of epoxy resin boards, the preparation method further includes: performing surface treatment on each of the plurality of epoxy resin boards.

[0011] Optionally, the pressure bonding of multiple epoxy resin boards includes: placing a sheet adhesive between two adjacent epoxy resin boards; and applying pressure bonding to the multiple epoxy resin boards for a set time under a set pressure, wherein the number of the multiple epoxy resin boards is greater than or equal to 4.

[0012] On the other hand, embodiments of the present invention also provide a system for preparing a dense layered rock sample. The system includes: a sample dispenser for containing a target amount of epoxy resin, and heating and stirring the epoxy resin under a set atmosphere until the epoxy resin expands and fills the sample dispenser and the proportion of nano-micron level bubbles in the epoxy resin is greater than a set value to obtain a liquid epoxy resin sample, wherein the target amount of epoxy resin is determined based on the volume of the sample dispenser and the target reservoir porosity; a setting mold for cooling and demolding the epoxy resin sample to obtain a solid epoxy resin plate, wherein the setting mold includes through holes for placing distributed optical fibers; and a press for pressurizing and bonding multiple epoxy resin plates to obtain a dense layered rock sample including the distributed optical fibers.

[0013] On the other hand, embodiments of the present invention also provide an analysis method for the fracturing process of a dense layered rock sample, characterized in that the analysis method includes: obtaining a dense layered rock sample including a distributed optical fiber using the preparation method of the dense layered rock sample described above; simulating the fracturing process of the dense layered rock sample; and acquiring the electrical signal of the dense layered rock sample during the fracturing process using the distributed optical fiber, so as to analyze the fracture initiation mechanism and fracture propagation law of the dense layered rock sample.

[0014] On the other hand, embodiments of the present invention also provide an analysis system for the fracturing process of a dense layered rock sample, characterized in that the analysis system includes: a dense layered rock sample preparation system as described above, used to obtain a dense layered rock sample including a distributed optical fiber; a fracturing process simulation device, used to simulate the fracturing process of the dense layered rock sample; and a fracturing process analysis device, used to acquire the electrical signal of the dense layered rock sample during the fracturing process through the distributed optical fiber, so as to analyze the fracture initiation mechanism and fracture propagation law of the dense layered rock sample.

[0015] Through the above technical solution, the rock samples prepared by this invention have the same porosity as the actual reservoir and can also simulate structures other than natural bedding fractures. Furthermore, this invention can customize rock samples of different shapes and sizes according to experimental needs, greatly improving the universality of the prepared rock samples in experiments. In addition, this invention achieves low-cost, high-precision, and visualized simulation of the reservoir fracturing process, avoiding the problems of high cost, inability to simulate micro- and nano-level pores and natural bedding fractures, and random pore distribution inherent in conventional methods.

[0016] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 A schematic flowchart illustrating a method for preparing a dense, layered rock sample according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the structure of an epoxy resin sample dispenser provided in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the structure of a special mold provided in an embodiment of the present invention;

[0021] Figure 4 This is a schematic diagram of the structure of an X-plate for a specially made mold provided in an embodiment of the present invention;

[0022] Figure 5 This is a schematic diagram of the structure of a Y-plate for a special mold provided in an embodiment of the present invention;

[0023] Figure 6 This is a schematic diagram of the structure of a Z-plate for a special mold provided in an embodiment of the present invention;

[0024] Figure 7 This is a schematic diagram illustrating a pressing method for an epoxy resin board according to an embodiment of the present invention;

[0025] Figure 8 A schematic diagram of the structure of the prepared dense layered rock sample provided in an embodiment of the present invention;

[0026] Figure 9 A schematic diagram of the structure of a system for preparing a dense, layered rock sample according to an embodiment of the present invention;

[0027] Figure 10 A schematic flowchart illustrating an analytical method for the fracturing process of a dense, layered rock sample, provided in an embodiment of the present invention.

[0028] Figure 11 This invention provides a schematic diagram of the structure of a visualized dense layered rock sample used to simulate triaxial experiments, as provided in an embodiment of the invention.

[0029] Figures 12a-12c A schematic diagram illustrating the experimental results of a simulated triaxial experiment provided in an embodiment of the present invention;

[0030] Figure 13 This is a schematic diagram of the structure of an analysis system for the fracturing process of a dense, layered rock sample, provided in an embodiment of the present invention. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can more clearly understand the solutions disclosed herein. It should be noted that one or more structures of the different implementations described below can be substituted for each other, and the perspective of the present disclosure is not limited to the examples below. Under the above concept, those skilled in the art can also obtain other possible implementations based on the examples below, and these implementations should also be considered as part of the present disclosure.

[0032] It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0033] This invention first provides a method S100 for preparing a dense, layered rock sample, such as... Figure 1 As shown, the preparation method S100 may include steps S110-S140:

[0034] Step S110: Place the target amount of epoxy resin into a sample mixing device. The sample mixing device may include, for example: Figure 2 The sample container shown.

[0035] The target amount of epoxy resin can be determined based on the volume of the sample dispenser and the target reservoir porosity. In one embodiment, the target amount of epoxy resin can be calculated using the following formula:

[0036] V2 = V1 × (100% - θ)

[0037] Where V2 is the target amount of epoxy resin, in L; V1 is the volume of the sample preparation container, in L; and θ is the target reservoir porosity, in %.

[0038] In other words, the target amount of epoxy resin V2 can be determined by the above formula based on the volume V1 of the sampler and the porosity θ of the target reservoir.

[0039] The beneficial effect of step S110 above is that by placing the target amount of epoxy resin in the sample mixing container, it is easier to control the porosity of the heated epoxy resin to reach the target reservoir porosity in subsequent steps, thereby making the prepared visualized dense layered rock sample as close as possible to the actual reservoir conditions.

[0040] Step S120: Heating and stirring the epoxy resin under a set atmosphere until the epoxy resin expands and fills the sample dispenser and the proportion of nano-micron level bubbles in the epoxy resin is greater than the set value, so as to obtain a liquid epoxy resin sample.

[0041] In one embodiment, the set atmosphere can be an inert gas. Additionally, the sample preparation device may include: a sealing cap for sealing the sample preparation container; and two symmetrical through holes, serving as an inlet and an outlet, respectively. Specifically, the set atmosphere can be obtained by injecting inert gas into the inlet and expelling air from the outlet; that is, by the above method, a certain amount of inert gas is present in the remaining space above the sealed sample preparation container.

[0042] Subsequently, during the mixing of the epoxy resin in the sample dispenser, these inert gases enter the epoxy resin and randomly form small bubbles, causing the epoxy resin to expand. When the volume of the epoxy resin expands to the volume of the sample dispenser, it indicates that all the inert gases have entered the epoxy resin, and it also indicates that the total volume of the small bubble pores is consistent with the actual pore volume of the target reservoir. Combining the calculation of the target amount of epoxy resin in step S110 above, the prepared visualized dense layered rock sample can more closely resemble the actual reservoir conditions.

[0043] In one embodiment, the sample preparation device may be equipped with at least one set of annular blades, preferably no less than five sets of annular blades, with the blade length slightly smaller than the inner diameter of the sample preparation container. Furthermore, to ensure that the prepared visualized dense layered rock sample closely resembles the actual reservoir conditions, the small air bubbles in the epoxy resin should primarily be at the nanometer / micrometer level. This can be achieved by using SEM (Scanning Electron Microscopy) to scan the prepared epoxy resin sample until the proportion of nanometer / micrometer-sized air bubbles in the epoxy resin is observed to exceed a set value, such as 70-95%, preferably 90%.

[0044] In one embodiment, step S120 may include step S121 and / or step S122:

[0045] Step S121: Stir the epoxy resin at a first rotational speed using at least one set of annular blades;

[0046] Step S122: Rotate the sample dispenser at a second rotational speed. The ratio of the first rotational speed to the second rotational speed can be 10-100, preferably 50-80. For example, the first rotational speed is not less than 1000 r / min, and the second rotational speed does not exceed 20 r / min.

[0047] The beneficial effects of using steps S121-S122 are: not only can the epoxy resin be thoroughly stirred in the sample mixing container, allowing inert gas to enter the epoxy resin and form bubbles, but the sample mixing device can also be rotated, thereby further accelerating the speed at which air enters the epoxy resin, resulting in more thorough and uniform stirring.

[0048] Specifically, you can refer to Figure 2This is a schematic diagram of an epoxy resin sample preparation device provided in an embodiment of the present invention, used for preparing epoxy resin samples. The sample preparation device structure can consist of a threaded steel sample preparation container, a heating jacket, a steel cap with an annular sealing ring, an annular blade, and a motor.

[0049] In one embodiment, the sample preparation container can be made of stainless steel, such as 304, 316, or 316L alloy. A heating jacket can be wrapped around the outer wall of the sample preparation container and connected to a temperature control system. The steel cap can be a two-layer cylindrical structure, where the larger diameter cylinder matches the outer diameter of the sample preparation container, and the smaller diameter cylinder matches the inner diameter, and has a threaded structure for embedding into the container. Furthermore, the smaller diameter cylinder of the steel cap can have an annular groove on the side near the larger cylinder diameter for placing an annular sealing ring, thus achieving a sealing effect. The sample preparation device can have a through hole at its center for housing a stirrer. Additionally, the sample preparation device can have two symmetrical through holes, serving as an inert gas inlet and an air exhaust outlet, respectively.

[0050] In one embodiment, one end of the sample mixer with annular blades is placed in the sample mixing container, and the other side is connected to a motor through the central hole of a steel cap. The various parts of the sample mixer can form a unified whole, and the entire sample mixer can be placed on another motor to rotate clockwise or counterclockwise. This allows for further rotation of the external components while the internal mixing is being stirred, thereby further accelerating the entry of air into the epoxy resin and resulting in more thorough and uniform mixing.

[0051] The specific operating parameters in step S120 can be found in the following embodiment. First, the calculated target amount of epoxy resin is placed in the sample preparation container and covered with a steel lid. Inert gas is injected, air is expelled, the inlet and outlet are closed, the temperature control system is turned on, and the temperature of the sample preparation container is raised to 95℃~120℃ to soften the epoxy resin. Then, the stirrer motor is turned on to stir the epoxy resin at a first speed of not less than 1000 r / min, and the inert gas begins to enter the epoxy resin. At the same time, another motor is turned on to rotate the sample preparation container at a second speed of not more than 20 r / min, thereby accelerating the fusion speed of the inert gas and epoxy resin. The epoxy resin expands until it fills the sample preparation container, and a sample is taken for SEM scanning. If a large number of nano- or micron-sized small bubbles are not observed, sample preparation continues until bubbles are found to be mainly at the nano- or micron-sized, that is, the proportion of bubbles at the nano- or micron-sized is greater than 90%, at which point sample preparation is stopped.

[0052] The beneficial effect of step S120 above is that after the inert gas enters the epoxy resin, it initially exists in the form of large-volume bubbles. Under the stirring of multiple annular blades in the sample dispenser, the large bubbles are gradually broken down into smaller bubbles until a large number of nano- and micron-sized small bubbles are formed. As long as the stirring time is long enough, the stirring speed is fast enough, and there are enough blades in the sample dispenser, a sufficiently small pore structure can be obtained, and the prepared rock sample has the same porosity as the actual reservoir. This ensures that the formed bubbles are mainly at the nano- and micron level, which allows the prepared visualized dense layered rock sample to closely resemble the actual reservoir conditions.

[0053] Step S130: Cool and demold the epoxy resin sample by setting a mold to obtain a solid epoxy resin board.

[0054] After setting the mold, the shape of the obtained dense layered rock sample is determined by the mold, which can maximize the applicability of the present invention in the simulation experiment of tight reservoir fracturing.

[0055] The mold setup can include through-holes for placing distributed optical fibers. That is, the epoxy resin sample is cooled and demolded through this mold, resulting in an epoxy resin board embedded with through-hole distributed optical fibers. One end of the distributed optical fiber can be connected to an OFDR fiber optic demodulator. The advantage of this setup is that while visualizing the crack initiation and propagation process using a dense, layered rock sample at the start of the experiment provides a direct view of the dynamic process of fracturing, which is helpful for qualitative research on the fracturing dynamics, a precise quantitative description of the fracturing dynamics is still needed. During crack initiation and propagation, the visualized dense, layered rock sample undergoes deformation. These deformation processes are recorded by the OFDR fiber optic demodulator via the distributed optical fibers, allowing for a precise quantitative description of the fracturing dynamics.

[0056] The mold used in this invention is preferably a specially made mold, which can be customized according to specific experimental needs. Please refer to [reference needed]. Figures 3 to 6 This is a schematic diagram of a specially designed mold and its various parts provided in an embodiment of the present invention. Its function is to prepare epoxy resin boards. The mold can be either integral or detachable, and it can include a sample inlet and an vent, allowing the prepared epoxy resin sample to be poured into the mold through the sample inlet until the epoxy resin sample appears at the vent.

[0057] Specifically, when the mold is designed to be detachable, it can be primarily composed of two X-plates, two Y-plates, and two Z-plates. The two X-plates can have two α-grooves and two β-grooves for placing the Y and Z plates, and each of the four grooves can have two symmetrical through-threaded holes for holding fixing rods. Specifically, the top X-plate can have two through holes within its grooves, serving as a sample inlet and an vent, respectively. The two Y-plates can have two γ-grooves for placing the Z-plate, and each of the four right angles of the Y-plate can have through-threaded holes for holding fixing rods. The two Z-plates can have two symmetrical through holes at their top and bottom ends for placing distributed optical fibers. Specifically, two distributed optical fibers can be placed along the through holes in the Z-plates, ensuring they remain taut. In one embodiment, a heat-resistant film can also be attached to the inner wall of the mold, tightly bonded to the inner wall with strong adhesive for easy demolding.

[0058] The beneficial effects of adopting the above-mentioned further solution are as follows: Currently, commonly used rock mechanics testing systems are used for pseudo-triaxial experiments to simulate reservoir fracturing processes, and the commonly used rock sample shape is a large-volume cube. Using the specially designed mold mentioned in this invention, the obtained sheet-like epoxy resin plates can be pressed together, ultimately yielding a large-volume cube-shaped, visualized, dense, layered rock sample. Thus, there is no need to develop new experimental equipment, and existing experimental equipment can be utilized to the greatest extent possible.

[0059] In particular, after step S130 and before step S140, the preparation method S100 of the present invention may further include: performing surface treatment on each of the plurality of epoxy resin boards.

[0060] Specifically, after preparing the epoxy resin sample, it is poured into a specific mold. The mold is then immersed in ice water for rapid cooling, and the mold is subsequently removed to obtain the epoxy resin board. The rapid cooling of the mold in ice water prevents the upward movement of low-density inert gases within the epoxy resin due to slow cooling. After demolding the cooled and cured epoxy resin board, its surface can be repaired using epoxy resin, a utility knife, and a polishing machine to ensure a smooth surface and prevent stress defects (protrusions or depressions) from affecting experimental results. Otherwise, the visualized dense layered rock sample prepared from an epoxy resin board with defects (protrusions or depressions) is likely to have stress defects, and during fracturing, the fractures will mainly initiate or propagate along the direction of the stress defects, resulting in a discrepancy with the actual reservoir conditions.

[0061] The beneficial effects of adopting the above-mentioned further scheme are: the heated epoxy resin is in a fluid state and needs to be cooled and cured in a specific mold to obtain a sheet-like epoxy resin plate, which needs to be repaired to ensure that its surface is smooth before it can be used for subsequent preparation of visualized dense layered rock samples.

[0062] Step S140: Pressurize and bond multiple epoxy resin plates together to obtain a dense, layered rock sample including distributed optical fibers.

[0063] In one embodiment, step S140 may further include steps S121 and S122:

[0064] Step S141: Place sheet adhesive between two adjacent epoxy resin boards; and

[0065] Step S142: Under a set pressure, multiple epoxy resin boards are pressurized and bonded for a set time.

[0066] Please continue to refer to this. Figure 7 Sheet adhesive can be placed between the prepared epoxy resin boards, or a strong adhesive can be applied to one side of the epoxy resin board. The pressure is set, for example, to 2-5 MPa, and the duration is set, for example, to 0.5-1.5 hours. In one embodiment, a press can be used to apply pressure at a set pressure of not less than 3 MPa for a set duration of not less than 0.5 hours. Furthermore, the number of epoxy resin boards is greater than or equal to four, i.e., at least four epoxy resin boards are tightly bonded together. Figure 8 The image shown is a visualized dense layered rock sample structure prepared using distributed optical fiber technology, provided by an embodiment of the present invention. It can be used for subsequent hydraulic fracturing simulation experiments.

[0067] The beneficial effects of adopting the above scheme are: pressing sheet-like epoxy resin plates into large-volume cubic visualized dense layered rock samples, and forming a layered structure between each pair of epoxy resin plates, which can simulate the bedding structure of the actual reservoir to the greatest extent, as well as natural bedding fractures (natural bedding fractures have a lower degree of adhesion).

[0068] In summary, current tight reservoir fracturing simulation experiments often utilize existing rock cores and employ online CT scans and acoustic emission techniques to detect dynamic processes. However, limitations in research costs and equipment performance make it difficult to accurately describe the dynamic fracturing process. Some researchers have also constructed reservoir pore structures using extensive static CT scan results and then used 3D printing technology to "replicate" these pore structures within epoxy resin, preparing visualized rock samples. However, the pore sizes constructed using this 3D printing technology are relatively large, far from reaching the nanometer or micrometer level, and cannot "replicate" the layered structure of laminar reservoirs. Therefore, to accurately describe the dynamic pressure process and clarify the fracture initiation mechanism, fracture propagation and proppant migration patterns, and temporary plugging efficiency, a visualized rock sample preparation technology that can best reflect the actual reservoir conditions is urgently needed.

[0069] To address the aforementioned technical problems, this invention provides a method for preparing visualized dense layered rock samples using distributed optical fiber technology. The method involves calculating the amount of epoxy resin needed based on the sample preparation device volume and the target reservoir porosity, placing it in the sample preparation device, injecting inert gas to purge air, heating and stirring until the epoxy resin expands to fill the sample preparation device, and observing the presence of numerous nano- and micro-sized pores in the sample using SEM scanning. The prepared epoxy resin sample is then poured into a specific mold embedded with distributed optical fibers, cooled, and demolded to obtain sheet-like epoxy resin plates. These plates are then repaired using epoxy resin or a utility knife to ensure a smooth surface. Finally, under pressure, at least four epoxy resin plates are tightly bonded together using strong adhesive to obtain a visualized dense layered rock sample prepared using distributed optical fiber technology.

[0070] The beneficial effects of this invention are: given a sufficiently long stirring time, a sufficiently fast stirring speed, and a sufficient number of sample mixing blades, a sufficiently small pore structure can be obtained, and the prepared rock sample has the same porosity as the actual reservoir. Furthermore, the lamination of sheet-like epoxy resin plates can simulate structures other than natural bedding fractures. Simultaneously, rock samples of different shapes and sizes can be customized according to experimental needs, greatly improving the universality of the rock sample in experiments. This achieves a low-cost, high-precision, and visualized simulation of the reservoir fracturing process, avoiding the problems of high cost, inability to simulate micro- and nano-level pores and natural bedding fractures, and random pore distribution inherent in conventional methods.

[0071] On the other hand, the present invention also provides a system 200 for preparing dense, layered rock samples, such as... Figure 9 As shown, the preparation system 200 may include:

[0072] A sampler is used to hold the target amount of epoxy resin and to heat and stir the epoxy resin under a set atmosphere until the epoxy resin expands and fills the sampler and the proportion of nano-micron level bubbles in the epoxy resin is greater than a set value, so as to obtain a liquid epoxy resin sample. The target amount of epoxy resin is determined according to the volume of the sampler and the target reservoir porosity.

[0073] A mold is set up for cooling and demolding an epoxy resin sample to obtain a solid epoxy resin board, wherein the mold may include through holes for placing distributed optical fibers; and

[0074] A press is used to pressurize and bond multiple epoxy resin boards to obtain a dense, layered rock sample that may include distributed optical fibers.

[0075] For details and beneficial effects of the preparation system for a dense layered rock sample according to this application, please refer to the description of the preparation method for a dense layered rock sample above, and will not be repeated here.

[0076] On the other hand, the present invention also provides an analytical method S300 for the fracturing process of dense layered rock samples, such as... Figure 10 As shown, the analysis method S300 may include steps S310-S330:

[0077] Step S310: Using the method for preparing dense layered rock samples described above, obtain a dense layered rock sample including distributed optical fibers, such as... Figure 11 As shown;

[0078] Step S320: Simulate the fracturing process of the dense, layered rock sample; and

[0079] Step S330: Obtain electrical signals of dense layered rock samples during the fracturing process through distributed optical fibers to analyze the fracturing mechanism and fracturing propagation law of the dense layered rock samples.

[0080] Please continue to refer to this. Figure 11 This is a schematic diagram of a visualized dense layered rock sample structure for pseudo-triaxial experiments provided by an embodiment of the present invention, which is used to carry out pseudo-triaxial experimental research simulating the fracturing process.

[0081] in, Figure 11 The main components include: a visualized dense layered rock sample, an open-hole section, and a steel pipe. The visualized dense layered rock sample is prepared using the method described above. As mentioned above, it contains randomly distributed nano- and micro-sized pores (small air bubbles) and a large number of layered structures. A cylindrical hole can be drilled along the center of the prepared visualized dense layered rock sample to serve as the open-hole section, which can be used to place the steel pipe. For example, a steel pipe with an outer diameter slightly smaller than the open-hole section, a length greater than the open-hole section, and through holes in its sidewalls can be placed in the open-hole section. The steel pipe can be cylindrical, with an outer diameter slightly smaller than the diameter of the open-hole section, a wall thickness preferably not less than 4 mm, and a few through holes in its sidewalls as perforations. Its length must exceed the open-hole section, preferably not less than 5 cm.

[0082] In addition, epoxy resin can be used to consolidate the steel pipe and the visualized dense layered rock sample to facilitate subsequent quasi-triaxial experimental studies simulating the fracturing process. Specifically, an OFDR fiber optic demodulator can be used to quantitatively analyze the fracture initiation mechanism and fracture propagation law during the fracturing process. For example, various image denoising algorithms, threshold segmentation, and watershed algorithms can be used to distinguish phases, thereby establishing a quantitative dynamic transport law of proppant, while recording the temporary plugging effect of the temporary plugging agent in the perforation.

[0083] The beneficial effect of adopting the above scheme is that, although the dense layered rock samples prepared by the method provided by the present invention have the advantage of visualization, allowing for direct observation of fracture initiation and propagation, proppant migration, and the temporary plugging effect, a quantitative description of this process is still needed. This problem can be effectively solved by the above-mentioned analytical method S300 for the fracturing process of dense layered rock samples.

[0084] Specific implementation parameters can be found in the following examples. Taking a target reservoir porosity of 6.4% as an example, with a sample preparation container volume of 3L, 2.8L of epoxy resin needs to be poured into the sample preparation container first, and 1.2L of helium gas (under normal temperature and pressure conditions) is added to purge air. The mixture is then heated and stirred to obtain a 3L epoxy resin sample. Next, the epoxy resin is poured into a special mold, cooled, and demolded. The surface is then repaired to obtain 10 epoxy resin plates measuring 10cm × 10cm × 1cm. Finally, after applying strong adhesive to adjacent epoxy resin plates, they are placed on a press machine and pressurized at 5MPa for 53 minutes to obtain a 10cm × 10cm × 10cm visualized dense layered rock sample.

[0085] Furthermore, dense, layered rock samples can be placed in a rock mechanics testing system for simulation analysis. For example, a pseudo-triaxial experiment can be conducted under conditions of a radial stress of 20 MPa and a proppant-containing fracturing fluid injection rate of 0.5 ml / min. Experimental results are as follows... Figures 12a-12c As shown, schematic diagrams illustrate the variation of crack width over time, the amount of proppant transported in cracks with different tortuosities, and the aging time of temporary plugging agents with different particle sizes.

[0086] In summary, this invention addresses the challenge of accurately describing fracture initiation and propagation, as well as proppant migration behavior, in existing laboratory experiments by providing a device and method for preparing visualized dense layered rock samples using distributed optical fiber technology. By applying distributed optical fiber technology to prepare visualized dense layered rock samples, this invention achieves low-cost, high-precision, and visualized simulation of reservoir fracturing processes, avoiding the problems of high cost, inability to simulate micro- and nano-level pores and natural bedding fractures, and random pore distribution inherent in conventional methods. Furthermore, this invention can utilize distributed optical fiber technology to record deformation during fracturing, establishing quantitative laws governing the dynamic migration of proppant.

[0087] On the other hand, the present invention also provides an analysis system 400 for the fracturing process of dense layered rock samples, such as... Figure 13 As shown, the analysis system 400 may include:

[0088] The dense layered rock sample preparation system 200 described above is used to obtain dense layered rock samples including distributed optical fibers.

[0089] Fracturing process simulation device 410, used to simulate the fracturing process of dense layered rock samples; and

[0090] The fracturing process analysis device 420 is used to acquire electrical signals of dense layered rock samples during the fracturing process via distributed optical fibers, so as to analyze the fracturing mechanism and fracturing propagation law of the dense layered rock samples.

[0091] For details and beneficial effects of the analytical system for the fracturing process of a dense layered rock sample as described in this application, please refer to the above description of the analytical method for the fracturing process of a dense layered rock sample, which will not be repeated here.

[0092] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0093] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for preparing a dense, layered rock sample, characterized in that, The preparation method includes: The target amount of epoxy resin is placed in a sample dispenser, wherein the target amount of epoxy resin is determined based on the volume of the sample dispenser and the target reservoir porosity. The epoxy resin is heated and stirred under a set atmosphere until the epoxy resin expands and fills the sample dispenser and the proportion of nano-micron level bubbles in the epoxy resin is greater than a set value, so as to obtain a liquid epoxy resin sample. The epoxy resin sample is cooled and demolded by setting a mold to obtain a solid epoxy resin board, wherein the setting mold includes through holes for placing distributed optical fibers. Multiple epoxy resin plates are pressurized and bonded together to obtain a dense, layered rock sample including the distributed optical fiber.

2. The preparation method according to claim 1, characterized in that, Determining the target amount of the epoxy resin includes: Based on the volume V1 of the sample dispenser and the target reservoir porosity θ, the target amount V2 of the epoxy resin is determined by the following formula: V2 = V1 × (100% - θ).

3. The preparation method according to claim 1, characterized in that, The sample mixing device includes: a sealing cap, an air inlet, and an air outlet. The set atmosphere is obtained by injecting inert gas into the air inlet and discharging air from the exhaust port.

4. The preparation method according to claim 1, characterized in that, The sample mixing device includes at least one set of annular blades, and the heating and stirring of the epoxy resin under a set atmosphere includes: The epoxy resin is stirred at a first rotational speed by the at least one set of annular blades; and / or The sample dispenser is rotated at a second rotational speed, wherein the ratio of the first rotational speed to the second rotational speed is 50-80.

5. The preparation method according to claim 1, characterized in that, The mold is a detachable type, including a sample inlet and an exhaust outlet, and the inner wall of the mold is covered with a heat-resistant film.

6. The preparation method according to claim 1, characterized in that, Before the pressure bonding of the multiple epoxy resin boards, the preparation method further includes: Each of the plurality of epoxy resin boards undergoes surface treatment.

7. The preparation method according to claim 1, characterized in that, The pressure bonding of multiple epoxy resin boards includes: Place sheet adhesive between two adjacent epoxy resin boards; and Under a set pressure, multiple epoxy resin boards are pressurized and bonded for a set time, wherein the number of the multiple epoxy resin boards is greater than or equal to 4.

8. A system for preparing dense, layered rock samples, characterized in that, The preparation system includes: A sample preparation device is used to contain a target amount of epoxy resin and to heat and stir the epoxy resin under a set atmosphere until the epoxy resin expands and fills the sample preparation device and the proportion of nano-micron level bubbles in the epoxy resin is greater than a set value, so as to obtain a liquid epoxy resin sample. The target amount of epoxy resin is determined according to the volume of the sample preparation device and the target reservoir porosity. A mold is set up for cooling and demolding the epoxy resin sample to obtain a solid epoxy resin board, wherein the mold includes through holes for placing distributed optical fibers; and A press is used to pressurize and bond multiple epoxy resin boards to obtain a dense, layered rock sample including the distributed optical fibers.

9. A method for analyzing the fracturing process of a dense, layered rock sample, characterized in that, The analytical method includes: A dense layered rock sample including distributed optical fibers is obtained by the method for preparing a dense layered rock sample according to any one of claims 1-7. The fracturing process of the dense, layered rock sample was simulated; and The electrical signals of the dense layered rock sample during the fracturing process are acquired through the distributed optical fiber to analyze the fracture initiation mechanism and fracture propagation law of the dense layered rock sample.

10. An analytical system for the fracturing process of dense layered rock samples, characterized in that, The analysis system includes: The system for preparing dense layered rock samples according to claim 8 is used to obtain dense layered rock samples including distributed optical fibers. A fracturing process simulation device is used to simulate the fracturing process of the aforementioned dense, layered rock sample; and The fracturing process analysis device is used to acquire electrical signals of the dense layered rock sample during the fracturing process through the distributed optical fiber, so as to analyze the fracturing initiation mechanism and fracturing propagation law of the dense layered rock sample.

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