Method for preparing sample for fracturing experiment of transitional continental shale reservoir
By preparing fracturing test samples similar to those from marine-continental transitional shale reservoirs, the immaturity of hydraulic fracturing technology was addressed, enabling more efficient experimental simulation and parameter determination.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-27
- Publication Date
- 2026-05-29
AI Technical Summary
In the existing technology, the hydraulic fracturing technology for marine-continental transitional shale reservoirs is not very mature, making it difficult to conduct effective fracturing experiments. Furthermore, multiple rock layers are distributed in marine-continental transitional shale reservoirs, making it difficult to directly collect rock samples for fracturing simulation experiments.
By obtaining rock samples from various strata of the marine-continental transitional shale reservoir, analyzing core characteristics, determining the ratio of simulated materials and target simulated materials, and preparing fracturing test specimens, we ensure that the simulated specimens are similar to the actual reservoirs, including similar rock mechanical parameters, mineral composition, and grain size.
It improves the feasibility and accuracy of hydraulic fracturing experiments in marine-continental transitional shale reservoirs, enabling better simulation of actual reservoir conditions and providing support for fracturing parameters during the hydraulic fracturing process.
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Figure CN122108699A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of marine-continental transitional shale reservoir development technology, and particularly relates to a method for preparing fracturing test samples for marine-continental transitional shale reservoirs. Background Technology
[0002] Currently, the exploitation of transitional shale reservoirs between marine and continental areas is one of the important areas of oil and gas exploration. Hydraulic fracturing technology is a key technology for the efficient development of transitional shale reservoirs between marine and continental areas. Among the existing technologies, the hydraulic fracturing technology for transitional shale reservoirs between marine and continental areas is still not very mature. Therefore, it is necessary to conduct fracturing experiments on transitional shale reservoirs between marine and continental areas to improve the hydraulic fracturing technology. Based on this, how to improve the feasibility of fracturing experiments on transitional shale reservoirs between marine and continental areas is an urgent technical problem to be solved. Summary of the Invention
[0003] The embodiments of this application provide a method for preparing experimental samples for fracturing in marine-continental transitional shale reservoirs, thereby improving the feasibility of fracturing experiments in marine-continental transitional shale reservoirs.
[0004] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.
[0005] According to a first aspect of the embodiments of this application, a method for preparing fracturing test specimens for a marine-continental transitional shale reservoir is provided. The method includes: obtaining rock samples corresponding to each stratum of the marine-continental transitional shale reservoir, the strata including tight sandstone, limestone, coal, carbonaceous shale, and siliceous shale; obtaining core characteristics corresponding to the rock samples of each stratum, the core characteristics including rock mechanical parameters, rock mineral composition, and rock grain size; determining simulation materials for each stratum except for the coal stratum based on the core characteristics, and collecting coal from the coal stratum of the marine-continental transitional shale reservoir as the simulation material for the coal stratum; determining the target simulation material ratio for each simulation material based on the core characteristics, and preparing the fracturing test specimens for the marine-continental transitional shale reservoir using the simulation materials and the target simulation material ratio.
[0006] In some embodiments of this application, based on the foregoing scheme, obtaining rock samples corresponding to each stratum of the marine-continental transitional shale reservoir includes: collecting rocks from each stratum of the marine-continental transitional shale reservoir; and processing the rocks of each stratum according to a preset rock specification to obtain rock samples corresponding to each stratum.
[0007] In some embodiments of this application, based on the foregoing scheme, obtaining the core characteristics corresponding to the rock samples of each rock layer includes: performing rock mechanical parameter tests on each rock sample to determine the rock mechanical parameters of each rock sample, wherein the rock mechanical parameters include elastic modulus, Poisson's ratio, stress, cohesion, tensile strength, compressive strength and internal friction angle; performing whole-rock mineral analysis on each rock sample to determine the rock mineral composition of each rock sample; and performing grain size analysis on each rock sample to determine the rock grain size of each rock sample.
[0008] In some embodiments of this application, based on the foregoing scheme, determining the simulated materials of each rock layer other than the coal layer based on the core characteristics includes: determining the composition of the simulated materials corresponding to each rock layer other than the coal layer based on the rock mineral composition; and determining the particle size of the simulated materials corresponding to each rock layer other than the coal layer based on the rock grain size.
[0009] In some embodiments of this application, based on the foregoing scheme, determining the target simulated material ratio of each simulated material based on the core characteristics includes: determining the simulated material ratio corresponding to each rock layer based on the rock mechanical parameters; preparing simulated samples according to the simulated material ratio, determining the simulated mechanical parameters of the simulated samples, and judging whether the simulated material ratio is reasonable based on the simulated mechanical parameters and the rock mechanical parameters; if the simulated material ratio is reasonable, then determining the simulated material ratio as the target simulated material ratio; if the simulated material ratio is unreasonable, then returning to the step of determining the simulated material ratio corresponding to each rock layer based on the rock mechanical parameters.
[0010] In some embodiments of this application, based on the foregoing scheme, the rationality of the simulated material ratio is determined by the following formula:
[0011]
[0012] α v =1
[0013]
[0014] Where, α E Let α be the similarity coefficient of the elastic modulus. σ Stress similarity coefficient, The similarity coefficient is the tensile strength. α is the similarity coefficient for compressive strength. v Let α be the similarity coefficient of Poisson's ratio. c The similarity coefficient of cohesion. σ is the similarity coefficient for the internal friction angle. c For compressive strength, σ tFor tensile strength, m represents the rock stratum, n represents the simulated sample, and the similarity coefficient is the ratio of the rock mechanical parameters to the corresponding simulated mechanical parameters. If all formulas are true, it indicates that the simulated material ratio is reasonable; if any formula is false, it indicates that the simulated material ratio is unreasonable.
[0015] In some embodiments of this application, based on the foregoing scheme, the preparation of the fracturing test specimen of the marine-continental transitional shale reservoir by mixing the simulated material and the target simulated material includes: preparing the target specimen slurry corresponding to each rock layer according to the target simulated material ratio corresponding to each rock layer; mixing the simulated materials corresponding to the rock layers on both sides of the transition layer according to a preset ratio and preparing the transition specimen slurry, wherein the transition layer is the boundary area between adjacent rock layers; and sequentially pouring the target specimen slurry and the transition specimen slurry into the mold according to the rock layer distribution order in the marine-continental transitional shale reservoir to obtain the fracturing test specimen of the marine-continental transitional shale reservoir.
[0016] In some embodiments of this application, based on the foregoing scheme, the step of sequentially pouring target sample slurry and transition sample slurry into the mold according to the strata distribution order in the marine-continental transitional shale reservoir includes: vertically pouring target sample slurry corresponding to a tight sandstone layer, a transition sample slurry corresponding to a first transition layer, a target sample slurry corresponding to a limestone layer, a transition sample slurry corresponding to a second transition layer, and a target sample slurry corresponding to a coal layer into the mold, thereby obtaining simulated tight sandstone layers, simulated first transition layers, simulated limestone layers, simulated second transition layers, and simulated coal layers distributed sequentially in the vertical direction. The first transition layer is the transition layer between the tight sandstone layer and the limestone layer, and the second transition layer is the transition layer between the limestone layer and the coal layer. Horizontally, sequentially pouring transition sample slurry corresponding to a third transition layer, a fourth transition layer, and a fifth transition layer onto the simulated coal layer, thereby obtaining a simulated third transition layer distributed sequentially in the horizontal direction. The simulation includes a fourth transition layer and a fifth transition layer. The third transition layer is the transition layer between the coal-rock layer and the first carbonaceous shale layer. The fourth transition layer is the transition layer between the coal-rock layer and the siliceous shale layer. The fifth transition layer is the transition layer between the coal-rock layer and the second carbonaceous shale layer. Following the horizontal direction, target sample slurries corresponding to the first carbonaceous shale layer, the sixth transition layer, the siliceous shale layer, the seventh transition layer, and the second carbonaceous shale layer are sequentially poured onto the simulated third, fourth, and fifth transition layers, respectively. This results in simulated first carbonaceous shale layer, simulated sixth transition layer, simulated siliceous shale layer, simulated seventh transition layer, and simulated second carbonaceous shale layer distributed sequentially in the horizontal direction. The sixth transition layer is the transition layer between the first carbonaceous shale layer and the siliceous shale layer, and the seventh transition layer is the transition layer between the second carbonaceous shale layer and the siliceous shale layer.
[0017] In some embodiments of this application, based on the foregoing scheme, the thickness of the simulated tight sandstone layer is 70–90 mm; the thickness of the simulated first transition layer is 5–15 mm; the thickness of the simulated limestone layer is 140–160 mm; the thickness of the simulated second transition layer is 5–15 mm; the thickness of the simulated coal and rock layer is 140–160 mm; the width of the simulated third transition layer in the horizontal direction is 70–90 mm, and the thickness in the vertical direction is 5–15 mm; the width of the simulated fourth transition layer in the horizontal direction is 100–120 mm, and the thickness in the vertical direction is 5–15 mm; the width of the simulated fifth transition layer in the horizontal direction is 100–120 mm, and the thickness in the vertical direction is 5–15 mm. The simulated first carbonaceous shale layer has a horizontal width of 70-90 mm and a vertical thickness of 210-230 mm; the simulated sixth transition layer has a horizontal width of 5-15 mm and a vertical thickness of 210-230 mm; the simulated siliceous shale layer has a horizontal width of 100-120 mm and a vertical thickness of 210-230 mm; the simulated seventh transition layer has a horizontal width of 5-15 mm and a vertical thickness of 210-230 mm; the simulated second carbonaceous shale layer has a horizontal width of 100-120 mm and a vertical thickness of 210-230 mm.
[0018] In some embodiments of this application, based on the foregoing scheme, a curing agent is added to the target sample slurry and the transition sample slurry, and a lubricant is applied to the mold.
[0019] Based on the technical solution proposed in this application, the ratio of simulated materials and target simulated materials for each rock layer in the marine-continental transitional shale reservoir is determined by core characteristics. Based on the ratio of the simulated materials and target simulated materials, fracturing test specimens for the marine-continental transitional shale reservoir are prepared. During the preparation process, each simulated rock layer and simulated transitional layer is cast according to the rock layer distribution sequence in the marine-continental transitional shale reservoir. This ensures that the fracturing test specimens for the marine-continental transitional shale reservoir have a similar rock layer distribution sequence to the marine-continental transitional shale reservoir, and that each simulated rock layer in the fracturing test specimens has similar rock composition, rock grain size, and rock mechanical parameters to the various rock layers in the marine-continental transitional shale reservoir. Therefore, the fracturing test specimens for the marine-continental transitional shale reservoir have a better simulation effect, thereby improving the feasibility of fracturing experiments in the marine-continental transitional shale reservoir.
[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description
[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:
[0022] Figure 1 A schematic diagram of a marine-continental transitional shale reservoir is shown in one embodiment of this application;
[0023] Figure 2 A flowchart illustrating the method for preparing experimental samples for fracturing in a marine-continental transitional shale reservoir according to one embodiment of this application is shown.
[0024] Figure 3 A schematic diagram of a test specimen mold for fracturing a marine-continental transitional shale reservoir is shown in one embodiment of this application. Detailed Implementation
[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0026] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.
[0027] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.
[0028] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.
[0029] It should also be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such uses of these terms can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described.
[0030] To enable those skilled in the art to better understand this application, firstly, in conjunction with Figure 1 This application provides a brief description of the marine-continental transitional shale reservoir.
[0031] See Figure 1 This illustration shows a schematic diagram of a marine-continental transitional shale reservoir in one embodiment of this application.
[0032] like Figure 1 As shown, the marine-continental transitional shale reservoir, in the vertical direction, can be a tight sandstone layer 110, a limestone layer 120, a coal layer 130, and a marine-continental transitional shale layer 140, wherein the marine-continental transitional shale layer 140, in the horizontal direction, can be a carbonaceous shale layer 141, a siliceous shale layer 142, and a carbonaceous shale layer 143.
[0033] Since the exploitation of marine-continental transitional shale reservoirs is one of the important areas of oil and gas exploration, and hydraulic fracturing technology is a key technology for the efficient development of marine-continental transitional shale reservoirs, the existing hydraulic fracturing technology for marine-continental transitional shale reservoirs is not very mature, and fracturing experiments of marine-continental transitional shale reservoirs are required. In addition, because multiple rock layers are distributed in marine-continental transitional shale reservoirs, it is difficult to directly collect rock samples for fracturing simulation experiments. Based on this, the inventors of this application propose a method for preparing fracturing experimental samples for marine-continental transitional shale reservoirs to improve the feasibility of fracturing experiments in marine-continental transitional shale reservoirs.
[0034] Next, we will combine Figure 2 The method for preparing experimental samples for fracturing in marine-continental transitional shale reservoirs proposed in this application is described in detail.
[0035] See Figure 2 This paper illustrates a method for preparing fracturing test samples in a marine-continental transitional shale reservoir according to one embodiment of this application. The method can be performed at least according to steps 210 to 240 as follows:
[0036] Step 210: Obtain rock samples corresponding to each stratum of the marine-continental transitional shale reservoir, wherein the strata include tight sandstone, limestone, coal, carbonaceous shale, and siliceous shale.
[0037] Step 220: Obtain the core characteristics corresponding to the rock samples of each rock layer. The core characteristics include rock mechanical parameters, rock mineral composition and rock grain size.
[0038] Step 230: Based on the core characteristics, determine the simulation materials for each rock layer other than the coal seam, and collect coal from the coal seam of the marine-continental transitional shale reservoir as the simulation materials for the coal seam.
[0039] Step 240: Determine the target simulated material ratio for each simulated material based on the core characteristics, and prepare the fracturing test sample of the marine-continental transitional shale reservoir using the simulated materials and the target simulated material ratio.
[0040] In this application, by obtaining rock samples corresponding to each stratum of the marine-continental transitional shale reservoir and analyzing the core characteristics of the rock samples corresponding to each stratum, the mechanical parameters, mineral composition, and grain size of the rocks in each stratum of the marine-continental transitional shale reservoir can be obtained. This allows for accurate analysis of the geological characteristics of each stratum in the marine-continental transitional shale reservoir, providing a data basis for the preparation of fracturing test samples for the marine-continental transitional shale reservoir, thereby improving the feasibility of fracturing experiments in the marine-continental transitional shale reservoir.
[0041] It is understandable that in this application, the simulated material for the coal seam can be directly obtained from the marine-continental transitional shale reservoir. This is because the main mineral in the coal seam is coal, and the composition of coal includes many different kinds of organic compounds. In the process of preparing the simulated material, it is difficult to directly select a simulated material with a composition similar to that of the coal seam. Therefore, by collecting coal from the coal seam of the marine-continental transitional shale reservoir as the simulated material for the coal seam, the problem of finding a simulated material with a composition similar to that of the coal seam can be avoided, thereby improving the feasibility of fracturing experiments in marine-continental transitional shale reservoirs.
[0042] In this application, the simulated materials of each rock layer other than the coal seam are determined by the core characteristics, and coal is collected from the coal seam of the marine-continental transitional shale reservoir as the simulated material of the coal seam. This can improve the similarity between the fracturing test sample of the marine-continental transitional shale reservoir and the marine-continental transitional shale reservoir, thereby improving the accuracy of the simulation of the fracturing test sample of the marine-continental transitional shale reservoir, and thus improving the scientificity and feasibility of the fracturing experiment of the marine-continental transitional shale reservoir.
[0043] In step 210 above, obtaining rock samples corresponding to each stratum of the marine-continental transitional shale reservoir can be specifically performed according to steps 211 to 212 as follows:
[0044] Step 211: Collect rocks from each stratum in the marine-continental transitional shale reservoir.
[0045] Step 212: Process the rocks of each rock layer according to the preset rock specifications to obtain rock samples corresponding to each rock layer.
[0046] In this application, the preset rock specifications can be a cylinder with a base radius of 25mm and a height of 50mm. Depending on actual needs, it can also be a cuboid or a cube. This application does not impose any further limitations on this.
[0047] In this application, collecting rocks from various strata within the marine-continental transitional shale reservoir ensures the comprehensiveness of the collected rock samples, enabling a more complete understanding of the stratigraphic characteristics of the marine-continental transitional shale reservoir. This provides a data foundation for subsequent fracturing experiments in the marine-continental transitional shale reservoir, thereby improving the feasibility of such experiments to a certain extent. Furthermore, processing the rocks according to predetermined specifications ensures that the obtained rock samples have consistent size standards. This improves the consistency of core characteristics between different rock samples, ensuring data consistency during fracturing experiments in the marine-continental transitional shale reservoir, further enhancing the feasibility of such experiments.
[0048] In step 220 above, obtaining the core characteristics corresponding to the rock samples of each rock layer can be specifically performed according to steps 221 to 223 as follows:
[0049] Step 221: Perform rock mechanical parameter tests on each rock sample to determine the rock mechanical parameters of each rock sample. The rock mechanical parameters include elastic modulus, Poisson's ratio, stress, cohesion, tensile strength, compressive strength and internal friction angle.
[0050] Step 222: Perform whole-rock mineral analysis on each rock sample to determine the rock mineral composition of each rock sample.
[0051] Step 223: Perform grain size analysis on each rock sample to determine the rock grain size of each rock sample.
[0052] In this application, it is understood that the rock mechanical parameters can provide support for the specific fracturing parameters of hydraulic fracturing experiments (such as fracturing fluid pressure, fracturing fluid type and proppant dosage during hydraulic fracturing), and the rock mineral composition and rock grain size can provide a basis for determining the simulated materials of various rock layers other than coal seams in marine-continental transitional shale reservoirs.
[0053] In this application, by conducting rock mechanical parameter tests, whole-rock mineral analysis, and grain size analysis on various rock samples, detailed rock mechanical parameters, rock mineral composition, and rock grain size of each rock sample can be determined. This provides data support for understanding the core characteristics of each rock layer in the marine-continental transitional shale reservoir. At the same time, it also provides a basis for determining the simulation material of the fracturing test specimens for the marine-continental transitional shale reservoir, thereby further improving the feasibility and accuracy of the marine-continental transitional shale reservoir experiment.
[0054] In step 230 above, the step of determining the simulated materials of each rock layer other than the coal seam based on the core characteristics can be specifically performed according to steps 231 to 232 as follows:
[0055] Step 231: Determine the composition of the simulated material corresponding to each rock layer other than the coal layer based on the rock mineral composition.
[0056] Step 232: Determine the particle size of the simulated material corresponding to each rock layer other than the coal seam based on the rock particle size.
[0057] In this application, the simulated material can be bone meal, shell powder, or other substances that conform to the composition of rock minerals, depending on actual needs. This application does not make any specific limitations in this regard.
[0058] In this application, by determining the simulated materials corresponding to each rock layer other than the coal seam based on rock mineral composition and rock grain size, the similarity between the simulated rock layers corresponding to each rock layer in the fracturing test sample of the marine-continental transitional shale reservoir and the rock layers in the marine-continental transitional shale reservoir can be improved. This can provide reasonable experimental samples for the implementation of fracturing experiments in marine-continental transitional shale reservoirs, thereby providing data support for the hydraulic fracturing of marine-continental transitional shale reservoirs, and further improving the accuracy and feasibility of fracturing experiments in marine-continental transitional shale reservoirs.
[0059] In step 240 above, the determination of the target simulation material ratio for each simulation material based on the core characteristics can be specifically performed according to steps 241 to 244 as follows:
[0060] Step 241: Based on the rock mechanical parameters, determine the simulated material ratio corresponding to each rock layer.
[0061] Step 242: Prepare a simulated sample according to the simulated material ratio, determine the simulated mechanical parameters of the simulated sample, and judge whether the simulated material ratio is reasonable based on the simulated mechanical parameters and the rock mechanical parameters.
[0062] Step 243: If the simulated material ratio is reasonable, then the simulated material ratio is determined as the target simulated material ratio.
[0063] Step 244: If the simulated material ratio is unreasonable, return to the step of determining the simulated material ratio corresponding to each rock layer based on the rock mechanical parameters.
[0064] In step 242 above, the rationality of the simulated material ratio can be determined by the following formulas (1) to (4):
[0065]
[0066] α v =1 (2)
[0067]
[0068] Where, α E Let α be the similarity coefficient of the elastic modulus. σ Stress similarity coefficient, The similarity coefficient is the tensile strength. α is the similarity coefficient for compressive strength. v Let α be the similarity coefficient of Poisson's ratio. c The similarity coefficient of cohesion. σ is the similarity coefficient for the internal friction angle. c For compressive strength, σ t For tensile strength, m represents the rock stratum, n represents the simulated sample, and the similarity coefficient is the ratio of the rock mechanical parameters to the corresponding simulated mechanical parameters. If all formulas are true, it indicates that the simulated material ratio is reasonable; if any formula is false, it indicates that the simulated material ratio is unreasonable.
[0069] In this application, the similarity coefficient can be the ratio of rock mechanical parameters to the corresponding simulated mechanical parameters, or it can be the ratio of simulated mechanical parameters to the corresponding rock mechanical parameters. This application does not make any specific limitation in this regard.
[0070] In this application, it should be noted that if the above formulas (1) to (4) are satisfied at the same time, it means that the simulated sample prepared according to the simulated material ratio satisfies the mechanical similarity, stress similarity, deformation similarity and failure similarity with the rock sample. That is, it can be considered that the simulated sample can accurately simulate the rock sample, and the simulated sample has similar core characteristics to the rock sample.
[0071] In this application, by determining the simulated material ratio through rock mechanics parameters, the simulated rock layers in the simulated marine-continental transitional shale reservoir fracturing test sample can be made to have similar mechanical properties to the rock layers in the marine-continental transitional shale reservoir. Furthermore, by simulating hydraulic fracturing on the marine-continental transitional shale reservoir fracturing test sample, some fracturing parameters in the hydraulic fracturing process of the marine-continental transitional shale reservoir can be determined. In addition, by judging whether the simulated material ratio is reasonable through formulas (1) to (4), the accuracy of each simulated rock layer in the marine-continental transitional shale reservoir fracturing test sample can be improved, thereby improving the feasibility of the marine-continental transitional shale reservoir fracturing test.
[0072] In step 240 above, the preparation of the fracturing test sample of the marine-continental transitional shale reservoir by mixing the simulated material and the target simulated material can be specifically performed according to steps 245 to 247 as follows:
[0073] Step 245: Prepare the target sample slurry corresponding to each rock layer using the target simulation material ratio corresponding to each rock layer.
[0074] Step 246: Mix the simulated materials corresponding to the rock layers on both sides of the transition layer according to a preset ratio and prepare the transition sample slurry. The transition layer is the boundary area between adjacent rock layers.
[0075] Step 247: According to the strata distribution order in the marine-continental transitional shale reservoir, the target sample slurry and the transitional sample slurry are poured into the mold in sequence to obtain the fracturing test sample of the marine-continental transitional shale reservoir.
[0076] In step 247 above, the target sample slurry and the transition sample slurry are poured into the mold sequentially according to the strata distribution order in the marine-continental transitional shale reservoir. Specifically, this can be performed according to steps 2471 to 2473 as follows:
[0077] Step 2471: In the vertical direction, the target sample slurry corresponding to the dense sandstone layer, the transition sample slurry corresponding to the first transition layer, the target sample slurry corresponding to the limestone layer, the transition sample slurry corresponding to the second transition layer, and the target sample slurry corresponding to the coal and rock layer are poured into the mold in sequence to obtain a simulated dense sandstone layer, a simulated first transition layer, a simulated limestone layer, a simulated second transition layer, and a simulated coal and rock layer distributed in sequence in the vertical direction. The first transition layer is the transition layer between the dense sandstone layer and the limestone layer, and the second transition layer is the transition layer between the limestone layer and the coal and rock layer.
[0078] Step 2472: In the horizontal direction, the transition sample slurry corresponding to the third transition layer, the transition sample slurry corresponding to the fourth transition layer, and the transition sample slurry corresponding to the fifth transition layer are sequentially poured on the simulated coal and rock layer to obtain simulated third transition layer, simulated fourth transition layer, and simulated fifth transition layer distributed in the horizontal direction. The third transition layer is the transition layer between the coal and rock layer and the first carbonaceous shale layer, the fourth transition layer is the transition layer between the coal and rock layer and the siliceous shale layer, and the fifth transition layer is the transition layer between the coal and rock layer and the second carbonaceous shale layer.
[0079] Step 2473: In accordance with the horizontal direction, target sample slurry corresponding to the first carbonaceous shale layer, the sixth transition layer, the siliceous shale layer, the seventh transition layer, and the second carbonaceous shale layer are sequentially poured onto the simulated third transition layer, the simulated fourth transition layer, and the simulated fifth transition layer, respectively, to obtain simulated first carbonaceous shale layer, simulated sixth transition layer, simulated siliceous shale layer, simulated seventh transition layer, and simulated second carbonaceous shale layer distributed sequentially in the horizontal direction. The sixth transition layer is the transition layer between the first carbonaceous shale layer and the siliceous shale layer, and the seventh transition layer is the transition layer between the second carbonaceous shale layer and the siliceous shale layer.
[0080] In this application, a curing agent is added during the casting process of the target sample slurry corresponding to each rock layer, which can solidify the target sample slurry in a short time and fix its shape. Before casting the target sample slurry, the mold is coated with a lubricant, which can assist in demolding after casting to improve the success rate of demolding. In a specific embodiment, the curing agent can be a high-viscosity gypsum with a mass fraction of 5%. In other embodiments, it can also be other curing agents. This application does not make specific limitations on this.
[0081] In this application, combined with Figure 3 This application includes a schematic diagram of a fracturing test sample mold for a marine-continental transitional shale reservoir in one embodiment. The rock strata in the marine-continental transitional shale reservoir are distributed in sequence, and the target sample slurry and the transitional sample slurry are poured into the mold in that order. Figure 3 Specifically, in the vertical direction (along direction A), the layers can be, in sequence, dense sandstone, limestone, coal, and marine-continental transitional shale. In the marine-continental transitional shale, in the horizontal direction (along direction B), the layers can be, in sequence, first carbonaceous shale, siliceous shale, and second carbonaceous shale. Depending on the actual situation, other rock layer pouring sequences are also possible, and this application does not impose specific limitations on this.
[0082] In this application, after each pouring of the target sample slurry or the transition sample slurry, a preset time is required to allow the poured simulated rock layer to solidify in order to carry out subsequent pouring. In a specific embodiment, the preset time can be 5 minutes or 10 minutes. This application does not impose any further limitations on this.
[0083] In this application, the thickness of the simulated tight sandstone layer is 70-90 mm, specifically 80 mm; the thickness of the simulated first transition layer is 5-15 mm, specifically 10 mm; the thickness of the simulated limestone layer is 140-160 mm, specifically 150 mm; the thickness of the simulated second transition layer is 5-15 mm, specifically 10 mm; the thickness of the simulated coal and rock layer is 140-160 mm, specifically 150 mm; the width of the simulated third transition layer in the horizontal direction is 70-90 mm, specifically 80 mm, and the thickness in the vertical direction is 5-15 mm, specifically 10 mm; the width of the simulated fourth transition layer in the horizontal direction is 100-120 mm, specifically 110 mm, and the thickness in the vertical direction is 5-15 mm, specifically 10 mm; the width of the simulated fifth transition layer in the horizontal direction is 100-120 mm, specifically 110 mm, and the thickness in the vertical direction is 5-15 mm, specifically... The width of the simulated first carbonaceous shale layer in the horizontal direction is 70-90mm, specifically 80mm, and the thickness in the vertical direction is 210-230mm, specifically 220mm; the width of the simulated sixth transition layer in the horizontal direction is 5-15mm, specifically 10mm, and the thickness in the vertical direction is 210-230mm, specifically 220mm; the width of the simulated siliceous shale layer in the horizontal direction is 100-120mm, specifically... The thickness of the simulated seventh transition layer is 110mm, and the vertical thickness is 210-230mm, specifically 220mm; the horizontal width of the simulated seventh transition layer is 5-15mm, specifically 10mm, and the vertical thickness is 210-230mm, specifically 220mm; the horizontal width of the simulated second carbonaceous shale layer is 100-120mm, specifically 110mm, and the vertical thickness is 210-230mm, specifically 220mm.
[0084] In this application, the target sample slurry and the transition sample slurry are sequentially poured into the mold according to the strata distribution order in the marine-continental transitional shale reservoir. This makes the poured marine-continental transitional shale reservoir fracturing test sample similar to the strata distribution order in the marine-continental transitional shale reservoir. In this way, during the marine-continental transitional shale reservoir fracturing experiment, the fracturing parameters in the actual marine-continental transitional shale reservoir hydraulic fracturing process can be determined by performing hydraulic fracturing on the simulated sample, further improving the accuracy and feasibility of the marine-continental transitional shale reservoir fracturing experiment.
[0085] Based on the technical solution proposed in this application, the ratio of simulated materials and target simulated materials for each rock layer in the marine-continental transitional shale reservoir is determined by core characteristics. Based on the ratio of the simulated materials and target simulated materials, fracturing test specimens for the marine-continental transitional shale reservoir are prepared. During the preparation process, each simulated rock layer and simulated transitional layer is cast according to the rock layer distribution sequence in the marine-continental transitional shale reservoir. This ensures that the fracturing test specimens for the marine-continental transitional shale reservoir have a similar rock layer distribution sequence to the marine-continental transitional shale reservoir, and that each simulated rock layer in the fracturing test specimens has similar rock composition, rock grain size, and rock mechanical parameters to the various rock layers in the marine-continental transitional shale reservoir. Therefore, the fracturing test specimens for the marine-continental transitional shale reservoir have a better simulation effect, thereby improving the feasibility of fracturing experiments in the marine-continental transitional shale reservoir.
[0086] The above description is merely an embodiment of this application and is not intended to limit 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 sample for a fracturing experiment of a transitional shale reservoir, characterized in that, The method includes: Rock samples were obtained from each stratum of the marine-continental transitional shale reservoir, including tight sandstone, limestone, coal, carbonaceous shale, and siliceous shale. Obtain the core characteristics of rock samples corresponding to each rock layer. The core characteristics include rock mechanical parameters, rock mineral composition, and rock grain size. Based on the core characteristics, the simulation materials for each rock layer other than the coal layer were determined, and coal was collected from the coal layer of the marine-continental transitional shale reservoir as the simulation material for the coal layer. Based on the core characteristics, the target simulated material ratios for each simulated material are determined, and the fracturing test specimens of the marine-continental transitional shale reservoir are prepared using the simulated materials and the target simulated material ratios.
2. The method of claim 1, wherein, The process of obtaining rock samples corresponding to each stratum of the marine-continental transitional shale reservoir includes: Rock samples were collected from various strata within the aforementioned marine-continental transitional shale reservoir. According to the preset rock specifications, the rocks of each rock layer are processed to obtain rock samples corresponding to each rock layer.
3. The method according to claim 1, characterized in that, The acquisition of core features corresponding to rock samples from each rock layer includes: Rock mechanical parameters were tested on each rock sample to determine the rock mechanical parameters of each rock sample. The rock mechanical parameters include elastic modulus, Poisson's ratio, stress, cohesion, tensile strength, compressive strength and internal friction angle. Whole-rock mineral analysis was performed on each rock sample to determine the rock mineral composition of each sample. Grain size analysis was performed on each rock sample to determine the rock grain size of each sample.
4. The method according to claim 1, characterized in that, The determination of the simulated materials for each rock stratum other than the coal seam based on the core characteristics includes: Based on the rock mineral composition, determine the composition of the simulated materials corresponding to each rock layer other than the coal layer; Based on the rock grain size, the grain size of the simulated material corresponding to each rock layer other than the coal seam is determined.
5. The method according to claim 1, characterized in that, The determination of the target simulation material ratio for each simulation material based on the core characteristics includes: Based on the aforementioned rock mechanics parameters, the simulated material ratios corresponding to each rock layer are determined; Simulated samples were prepared according to the simulated material ratio, the simulated mechanical parameters of the simulated samples were determined, and the rationality of the simulated material ratio was judged based on the simulated mechanical parameters and the rock mechanical parameters. If the simulated material ratio is reasonable, then the simulated material ratio shall be determined as the target simulated material ratio; If the simulated material ratio is unreasonable, return to the step of determining the simulated material ratio corresponding to each rock layer based on the rock mechanical parameters.
6. The method according to claim 5, wherein the rationality of the simulated material ratio is determined by the following formula: α v ＝1 in, α E Let α be the similarity coefficient of the elastic modulus. σ Stress similarity coefficient, The similarity coefficient for tensile strength is... α is the similarity coefficient for compressive strength. v α is the similarity coefficient of Poisson's ratio. c The similarity coefficient of cohesion. σ is the similarity coefficient for the internal friction angle. c For compressive strength, σ t For tensile strength, m represents the rock stratum, n represents the simulated sample, and the similarity coefficient is the ratio of the rock mechanical parameters to the corresponding simulated mechanical parameters; If all formulas hold true, it indicates that the simulated material ratio is reasonable; If any formula is invalid, it indicates that the simulated material ratio is unreasonable.
7. The method according to claim 1, characterized in that, The preparation of the fracturing test specimen for the marine-continental transitional shale reservoir by mixing the simulated material and the target simulated material includes: According to the target simulation material ratio corresponding to each rock layer, the target sample slurry corresponding to each rock layer is prepared using the simulation material corresponding to each rock layer; Simulated materials corresponding to the rock layers on both sides of the transition layer are mixed in a preset ratio to prepare a transition sample slurry. The transition layer is the boundary region between adjacent rock layers. According to the strata distribution order in the marine-continental transitional shale reservoir, the target sample slurry and the transitional sample slurry are poured into the mold in sequence to obtain the fracturing test sample of the marine-continental transitional shale reservoir.
8. The method according to claim 7, characterized in that, The step of sequentially pouring the target sample slurry and the transitional sample slurry into the mold according to the strata distribution order in the marine-continental transitional shale reservoir includes: In a vertical direction, the target sample slurry corresponding to the dense sandstone layer, the transition sample slurry corresponding to the first transition layer, the target sample slurry corresponding to the limestone layer, the transition sample slurry corresponding to the second transition layer, and the target sample slurry corresponding to the coal and rock layer are poured into the mold in sequence to obtain simulated dense sandstone layer, simulated first transition layer, simulated limestone layer, simulated second transition layer, and simulated coal and rock layer distributed in a vertical direction. The first transition layer is the transition layer between the dense sandstone layer and the limestone layer, and the second transition layer is the transition layer between the limestone layer and the coal and rock layer. Along the horizontal direction, transition sample slurries corresponding to the third transition layer, the fourth transition layer, and the fifth transition layer are sequentially poured onto the simulated coal and rock layer to obtain simulated third, fourth, and fifth transition layers distributed sequentially in the horizontal direction. The third transition layer is the transition layer between the coal and rock layer and the first carbonaceous shale layer, the fourth transition layer is the transition layer between the coal and rock layer and the siliceous shale layer, and the fifth transition layer is the transition layer between the coal and rock layer and the second carbonaceous shale layer. In the horizontal direction, target sample slurry corresponding to the first carbonaceous shale layer, the sixth transition layer, the siliceous shale layer, the seventh transition layer, and the second carbonaceous shale layer are sequentially poured onto the simulated third transition layer, the simulated fourth transition layer, and the simulated fifth transition layer, respectively. This results in simulated first carbonaceous shale layer, simulated sixth transition layer, simulated siliceous shale layer, simulated seventh transition layer, and simulated second carbonaceous shale layer distributed sequentially in the horizontal direction. The sixth transition layer is the transition layer between the first carbonaceous shale layer and the siliceous shale layer, and the seventh transition layer is the transition layer between the second carbonaceous shale layer and the siliceous shale layer.
9. The method according to claim 8, characterized in that, The simulated tight sandstone layer has a thickness of 70–90 mm; the simulated first transition layer has a thickness of 5–15 mm; the simulated limestone layer has a thickness of 140–160 mm; the simulated second transition layer has a thickness of 5–15 mm; and the simulated coal and rock layer has a thickness of 140–160 mm. The simulated third transition layer has a width of 70-90 mm in the horizontal direction and a thickness of 5-15 mm in the vertical direction; the simulated fourth transition layer has a width of 100-120 mm in the horizontal direction and a thickness of 5-15 mm in the vertical direction; the simulated fifth transition layer has a width of 100-120 mm in the horizontal direction and a thickness of 5-15 mm in the vertical direction. The simulated first carbonaceous shale layer has a horizontal width of 70–90 mm and a vertical thickness of 210–230 mm; the simulated sixth transition layer has a horizontal width of 5–15 mm and a vertical thickness of 210–230 mm; the simulated siliceous shale layer has a horizontal width of 100–120 mm and a vertical thickness of 210–230 mm; the simulated seventh transition layer has a horizontal width of 5–15 mm and a vertical thickness of 210–230 mm; and the simulated second carbonaceous shale layer has a horizontal width of 100–120 mm and a vertical thickness of 210–230 mm.
10. The method according to claims 7 to 8, characterized in that, The target sample slurry and the transition sample slurry contain a curing agent, and the mold is coated with a lubricant.