A multi-purpose rock experimental sample and a preparation method thereof

Abstract

This invention discloses a multi-purpose rock experimental sample and its preparation method. The method includes inserting a representative rock sample into a sample stake; injecting resin into the sample stake after insertion to form a post-injection sample; curing and cooling the post-injection sample and then removing it to obtain a cured large sample; and cutting, grinding, and polishing the cured large sample to obtain the multi-purpose rock experimental sample. This invention is designed for preparing rock samples such as shale, which are relatively soft and brittle. The preparation process overcomes the disadvantages of shale being easily fractured and expanded. The prepared rock sample is firmly consolidated, effectively protected, and reusable. It utilizes a mixture of fine-grained sedimentation and chemical sedimentation to support planar samples. Various optical microscopes are used in combination, along with electron microscopy, employing incident light from multiple light sources and electron beam excitation with multiple probe detection methods to complete multi-purpose in-situ analysis and determination.

Description

Technical Field

[0001] This invention belongs to the fields of petroleum geology, rock mechanics and engineering, and specifically relates to a multi-purpose rock experimental sample and its preparation method. Background Technology

[0002] The oil and gas industry is targeting unconventional oil and gas reservoirs for exploration and development. The focus has shifted from the four properties of conventional oil and gas reservoirs to the seven properties of unconventional reservoirs. Specifically, the study has moved from "lithology, physical properties, electrical properties, and oil-bearing properties" to "lithology, physical properties, electrical properties, oil and gas-bearing properties, brittleness, source rock characteristics, and geostress anisotropy," with greater refinement. For example, in lithology, in addition to structure and tectonics, attention is paid to the content and types of fine-grained clastic sediments, the content and types of chemical sediments, and the arrangement of their components. In physical properties, besides measuring porosity and permeability, attention is paid to pore structure, i.e., the influence of pore size and type on porosity and permeability. Furthermore, due to the mixed influence of fine-grained sedimentation and chemical sedimentation, the sediments are small, poorly developed in pores, and widely distributed in hydrocarbons. This makes it difficult to characterize and evaluate some soft and fragile rock reservoirs (such as mudstone and shale reservoirs). Using conventional methods such as selecting samples from a core segment of a sandstone reservoir and conducting joint measurements of porosity and permeability, thin sections, fluorescence thin sections, cast thin sections, and scanning electron microscopy to characterize and evaluate the reservoirs is no longer sufficient to truly reflect the characteristics of mudstone and shale reservoirs.

[0003] In-situ analysis refers to the micro-area analysis of selected areas of a substance using modern techniques, including analysis of composition, content, and distribution. For soft, brittle rock reservoirs like shale, in-situ analysis is an important method. However, in practical applications, several problems exist. Taking scanning electron microscopy (SEM) analysis of sandstone samples as an example, the main purpose is to visually and accurately display the types and sizes of pores in shale. However, conventional shale sample preparation methods result in uneven, high-level surfaces after tapping. In the grayscale image displayed by SEM, high points appear light gray, while low points appear dark gray or black. All low points include weak points where pores and rock components are in contact, making it impossible to determine whether they are pores or to accurately measure their size, significantly impacting the analytical results. Therefore, how to prepare a sample that enables in-situ characterization of shale reservoirs; how to convert brittle, easily expandable rock samples into planar, multi-purpose samples; and how to improve the cumbersome sample preparation process and increase efficiency are all urgent problems to be solved. Summary of the Invention

[0004] To address the above problems, this invention proposes a method for preparing multi-purpose experimental rock samples, the method comprising:

[0005] A representative rock sample was inserted into the sample post;

[0006] Resin is injected into the sample pile after insertion to form a post-injection sample.

[0007] After the infused sample is cured and cooled, it is removed to obtain a cured large sample.

[0008] The solidified sample was cut, sanded, and polished to obtain a multi-purpose experimental rock sample.

[0009] Furthermore, mudstone and shale representative samples and sample piles are prepared before the rock representative samples are inserted into the sample piles;

[0010] The representative rock sample should meet the following conditions:

[0011] The diameter of the surface to be observed in the rock representative sample is less than or equal to 10 mm, and the height is 10-15 mm.

[0012] The rock sample described has no artificial cracks.

[0013] Furthermore, the sample pile is manufactured according to the following steps:

[0014] Separately fabricate sample cups, label windows, and silicone molds;

[0015] Multiple sample cups that have been fabricated are placed in the inner ring of a silicone mold, and the labeling window is placed in the inner ring formed by the multiple sample cups. The multiple sample cups, the labeling window and the silicone mold are in close contact with each other.

[0016] Furthermore, the sample cup is filled with quartz sand, the height of which is 1 / 3 to 2 / 3 of the height of the sample cup, and the particle size of the quartz sand is 0.5-1mm;

[0017] A label is affixed to the bottom of the labeling window, and the label records the sample sequence number and sample pile number of the mudstone and shale representative sample;

[0018] The silicone mold has a silicone wall and silicone bottom that are both no less than 5mm thick, and an inner diameter of 36mm.

[0019] Furthermore, both the sample cup and the labeling window are flat-bottomed right-angled cups, and the flat-bottomed right-angled cups are made of transparent material.

[0020] Furthermore, the insertion is performed in a vacuum environment, with the surface to be observed of the mudstone and shale representative sample facing upwards, and a portion of the rock representative sample is inserted into the quartz sand;

[0021] The side or part of the side of the rock representative sample is attached to the inner wall of the sample cup, and the overall height of the rock representative sample and the sample cup is 17mm to 19mm.

[0022] Furthermore, the curing temperature is 80℃~90℃, and the curing time is more than 18 hours;

[0023] The rock representative sample, quartz sand, and label in the solidified large sample are all transparent and identifiable.

[0024] Furthermore, after cutting, coarse grinding, and polishing the solidified sample, the surface of the rock representative sample to be observed reaches the mirror finish standard.

[0025] On the other hand, the present invention also proposes a multi-purpose rock experimental sample, which includes a sample post, a representative rock sample inserted on the sample post, and epoxy resin poured between the representative rock sample and the sample post.

[0026] The rock multi-purpose experimental sample was obtained by solidifying, cooling, cutting, grinding and polishing the injected sample.

[0027] Furthermore, the rock representative sample is columnar or conical, and the diameter of the surface to be observed of the rock representative sample is less than or equal to 10 mm.

[0028] Furthermore, the sample post includes an external silicone mold, a marking window set in the center of the silicone mold, and a sample cup set between the silicone mold and the marking window;

[0029] The sample cup contains quartz sand with a particle size of 0.5-1 mm.

[0030] A label is affixed to the bottom of the labeling window, and the label records the sample sequence number and sample pile number of the mudstone and shale representative sample;

[0031] The silicone mold has a silicone wall and silicone bottom that are both no less than 5mm thick, and an inner diameter of 36mm.

[0032] Furthermore, both the sample cup and the labeling window are transparent flat-bottomed right-angled cups. The thickness of the cup wall and the bottom of the flat-bottomed right-angled cup is 0.5mm to 1mm, the inner diameter is 10mm, and the height of the cup is 15mm.

[0033] This invention also proposes a method for using a multi-purpose rock experimental sample, the method comprising:

[0034] The rock samples were analyzed and identified using an optical microscope.

[0035] After optical microscopy analysis and identification, the rocks are often subjected to carbon or gold plating on the experimental samples.

[0036] In-situ analysis of multi-purpose rock samples after carbon and gold plating was performed using a combination of electron microscopy, energy dispersive spectroscopy, and electron probe microanalysis.

[0037] The beneficial effects of this invention are:

[0038] This invention addresses the preparation of soft, brittle rock samples, such as shale and mudstone. It overcomes the inherent weaknesses of shale, including its fragility and expansion, by producing firmly consolidated, effectively protected, and reusable rock samples. Through a combination of fine-grained and chemical sedimentary genesis, planar samples are supported. Various optical microscopes are used in conjunction with electron microscopy, employing multiple incident light sources and electron beam excitation with multiple probes for multi-purpose in-situ analysis. The rock sample characteristics determined using the methods proposed in this invention are more realistic and reliable, significantly contributing to the characterization and evaluation of rock reservoirs. It forms the basis for evaluating shale and mudstone reservoirs and improves sample preparation efficiency by more than six times.

[0039] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 The flowchart illustrates the method for preparing and using multi-purpose experimental samples of mudstone and shale provided in this embodiment of the invention.

[0042] Figure 2 A schematic diagram of the roughing process of mudstone and shale samples provided in an embodiment of the present invention is shown;

[0043] Figure 3 A schematic diagram of a sample pile provided in an embodiment of the present invention is shown;

[0044] Figure 4 A schematic diagram of the sample cup manufacturing process provided in an embodiment of the present invention is shown;

[0045] Figure 5 This illustration shows a schematic diagram of the annotation window creation provided in an embodiment of the present invention;

[0046] Figure 6 A schematic diagram of a silicone mold provided in an embodiment of the present invention is shown;

[0047] Figure 7 This diagram illustrates the insertion of a representative mudstone and shale sample according to an embodiment of the present invention.

[0048] Figure 8 This illustration shows a sample pile for completing the insertion of a representative mudstone and shale sample, as provided in an embodiment of the present invention.

[0049] Figure 9 This diagram illustrates the immersion injection of a representative mudstone and shale sample provided in an embodiment of the present invention.

[0050] Figure 10 A schematic diagram of the cured sample provided in an embodiment of the present invention is shown. Attached image description:

[0052] 1. Representative mudstone / shale sample; 11. Surface to be observed; 2. Sample stake; 21. Sample cup; 22. Labeling window; 23. Silicone mold; 211. Sample cup wall; 212. Sample cup bottom; 213. Quartz sand; 221. Labeling window cup wall; 222. Labeling window cup bottom; 223. Label; 224. Sample stake number; 225. Sample sequence number; 231. Silicone bottom; 232. Silicone wall; 3. Epoxy resin. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] This invention, through careful observation of various reservoir experimental analysis techniques, integrates multiple experimental analysis items onto a single sample, achieving multi-purpose, in-situ analysis. Taking shale samples as an example, this invention overcomes the shortcomings of poor correspondence and mutual interpretation of multi-sample joint analysis results in core sections caused by the well-developed bedding and rapid lithological changes in shale. It prepares multi-purpose samples from a single sampling point for experimental analysis, achieving the goal of precise characterization and evaluation of shale reservoirs.

[0055] Based on the above objectives, this invention provides a method for preparing and using shale samples as an example. The prepared samples can be analyzed and identified using five optical microscopes and observed using three electron microscopes. A large number of experimental parameters, such as lithology, pore structure, brittleness, oil content, and source rock characteristics, can be obtained. This achieves breakthroughs in multi-purpose use, in-situ analysis, and repeated experiments, overcoming the disadvantages of shale being easily broken and expanded. The samples are firmly consolidated, effectively protected, and can be reused.

[0056] like Figure 1 As shown, the preparation method mainly includes the following steps:

[0057] S1: Obtain a representative mudstone and shale sample 1. The representative mudstone and shale sample 1 should have the characteristics of having the largest possible observation surface 11 and no artificial gaps.

[0058] Specifically, such as Figure 2 As shown, by obtaining shale samples, and further by hammering, sawing, and shaping with pliers, the diameter of the observation surface 11 of the representative shale sample 1 can be less than or equal to 10 mm. The representative shale sample 1 is a columnar or conical sample with a height of 10-15 mm. Figure 2 (a) shows a representative sample of columnar mudstone and (b) shows a representative sample of conical mudstone.

[0059] S2: Fabricate sample pile 2, which consists of an external silicone mold 23, sample cups 21 arranged in the inner ring of the silicone mold 23, and marking windows 22 located in the center of multiple sample cups 21. The shapes of the sample pile 2, sample cups 21, and marking windows 22 are not particularly limited. The fabricated sample pile 2 must be clearly distinguishable and accurately marked to ensure that the mudstone and shale samples can be used for in-situ multiple experimental analyses and reused.

[0060] The sample pile 2 proposed in this embodiment adopts a cylindrical structure, and six sample cups 21 are provided, but not limited to six, and can be set according to actual needs. A schematic diagram of the sample pile 2 in this embodiment is shown below. Figure 3 As shown, six sample cups 21 are evenly arranged along the inner wall of the cylinder. A labeling window 22 is provided in the middle part of the six sample cups 21. The mark on the labeling window 22 corresponds to the sample sequence number 225 and the sample pile number 224 of the sample cup 21.

[0061] The sample pile shall be made in accordance with the following steps:

[0062] S21: Prepare a sample cup 21, and fill it with quartz sand 213 to fill 1 / 3 to 2 / 3 of the cup's height. Specifically, as follows... Figure 4 As shown, Figure 4 (a) is a sample cup 21 without quartz sand 213. The sample cup 21 is preferably a flat-bottomed right-angled glass cup. The thickness of the sample cup wall 211 and the sample cup bottom 212 is 0.5mm to 1mm, the inner diameter is 10mm, and the cup height is 15mm. Figure 4 (b) is a sample cup 21 containing quartz sand 213, wherein the particle size of quartz sand 213 is 0.5 mm to 1 mm.

[0063] S22: Create a labeling window 22, wherein the labeling window 22 is a flat-bottomed right-angled glass cup (e.g., ...). Figure 5 As shown in (a), invert the right-angled cup and attach label 223 (as shown in the image) to the bottom of the cup. Figure 5As shown in (b), use ink to record sample post number 224 in the center of the right-angled cup, and record sample sequence number 225 on the outer ring. Figure 5 Image (c) shows an overall schematic diagram of the labeling window. Specifically, in this embodiment, the thickness of the labeling window cup wall 221 and the labeling window cup bottom 222 is 0.5mm to 1mm, the inner diameter is 10mm, and the height is 10mm. Preferably, the sample cup 21 and the labeling window 22 can be prepared with the same specifications for ease of preparation. The diameter of the label 223 is equal to that of the labeling window cup bottom 222. In this embodiment, the label 223 is a circular kraft paper with a diameter of 10mm.

[0064] S23: Obtain a silicone mold 23, wherein the silicone mold 23 is made of silicone and is disposed on the outside of a plurality of sample cups 21. In this embodiment, the silicone mold 23 is as follows: Figure 6 As shown, the silicone wall 232 and silicone bottom 231 of the silicone mold 23 are both not less than 5mm, the inner diameter is 36mm, and the height of the silicone mold 23 is 25mm.

[0065] S3: Insert the mudstone and shale representative sample 1 onto the sample post 2, ensuring that the surface to be observed 11 is facing upwards, and semi-fix it in the sample cup 21. In this embodiment, the height of the mudstone and shale representative sample 1 and the sample cup 21 inserted together is controlled at 17-19mm (that is, the height from the top of the mudstone and shale representative sample 1 to the bottom 212 of the sample cup).

[0066] Specifically, such as Figure 7 As shown, with the observation surface 11 of the shale representative sample 1 facing upwards, insert it into the sample cup 21 according to the markings on the label window 22. A portion of the shale representative sample 1 is buried in the quartz sand 213, ensuring that a portion of the cylindrical or conical side of the sample adheres to the inner wall of the sample cup 21. By burying it in the quartz sand 213 and adhering it to the sample cup wall 211, the shale representative sample 1 is secured within the sample cup 21. The insertion of the remaining shale representative samples 1 is then completed sequentially. A schematic diagram of the completed insertion in this embodiment is shown below. Figure 8 As shown, the representative mudstone and shale sample 1 is inserted into the sample cup 21 according to certain requirements.

[0067] S4: After the mudstone and shale representative sample 1 is inserted, the sample pile 2 is placed in the vacuum chamber and resin is injected. In this embodiment, epoxy resin 3 is selected to immerse the mudstone and shale representative sample 1 in the injection.

[0068] A schematic diagram after infusion is shown in this embodiment. Figure 9 As shown, the representative mudstone and shale sample 1 needs to be immersed in the epoxy resin 3, around the mudstone and shale sample 1, and inside the quartz sand 213 to eliminate air bubbles, promote close contact between the epoxy resin 3 and the mudstone and shale sample 1, and at the same time prevent the epoxy resin 3 from entering the pores and affecting the oil content observation. Immersing the mudstone and shale sample 1 plays a protective role.

[0069] S5: Place the injected shale representative sample 1 into a forced-air drying oven and cure for at least 18 hours. Remove the sample from the silicone mold 23 to obtain a cured large-scale sample. The curing temperature is generally controlled below 90℃ to prevent changes in the shale representative sample 1 due to excessive temperature. The epoxy resin 3 solidifies with the shale representative sample 1, forming a rock-like large-scale sample. The specific effect achieved is as follows: Figure 10 As shown, the internal mudstone and shale representative samples 1, 223, and quartz sand 213 are transparent and identifiable.

[0070] S6: Selectively cut or coarsely grind the solidified sample to expose the shale surface 11 to be observed. Further, perform fine grinding, precision grinding and polishing to form a multi-purpose experimental sample of shale.

[0071] Specifically, by using methods such as anhydrous, saline, or dry grinding to prevent the shale sample 30 from expanding, the surface 11 of the shale to be observed is made to meet the mirror standard, specifically forming a smooth plane that allows reflections to be seen from the side. 。

[0072] This invention also proposes a method for using multi-purpose experimental samples of mudstone and shale. During use, various optical microscopes are used in combination, and an electron microscope is applied to complete multi-purpose in-situ analysis and determination by means of incident light from multiple light sources, electron beam excitation, and multi-probe detection.

[0073] After the preparation of multi-purpose mudstone and shale samples through fine grinding and polishing, optical microscopy was first used for analysis and identification, followed by electron microscopy to analyze the nanopore structure, clay minerals and other compositional characteristics of the mudstone and shale.

[0074] Specifically, the optical microscopy analysis and identification includes: detailed core description using a stereomicroscope, and photography under normal light and fluorescence; quantitative identification of the structure, texture, and metallic mineral composition of shale using a reflected light microscope; observation of pore structure characteristics such as the size, type, content, and distribution of micron-sized pores under a laser confocal microscope; and analysis of bitumen type, content, and occurrence state, as well as oil generation characteristics of shale, under a fluorescence microscope. Subsequently, an electron microscope is used to analyze various experimental samples of shale. Depending on the testing items and electron microscope requirements, bare samples, carbon-plated samples, and gold-plated samples are selected to eliminate sample charge. When carbonizing or gold-plating, a rubber sheet is placed over the label; after carbonizing or gold-plating, the rubber sheet is removed to expose the label. Before conducting various in-situ experimental analyses of shale, a cross is drawn around the sample, with the center point of the cross serving as the center for various experimental analyses, enabling in-situ analysis and detection.

[0075] The shale and mudstone multi-purpose experimental samples proposed in this invention can also be saturated with a sample box for repeated observation. If surface changes occur after long storage time, they can be polished again for further observation.

[0076] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a rock multipurpose experimental sample, characterized by, The preparation method includes: inserting a representative rock sample into a sample post; Resin is injected into the sample pile after insertion to form a post-injection sample. After the infused sample is cured and cooled, it is removed to obtain a cured large sample. The solidified sample was cut, sanded, and polished to obtain a multi-purpose experimental rock sample. The sample post is made according to the following steps: sample cup, labeling window and silicone mold are made separately; Multiple sample cups that have been fabricated are placed in the inner ring of a silicone mold, and the labeling window is placed in the inner ring formed by the multiple sample cups. The multiple sample cups, the labeling window and the silicone mold are in close contact with each other. Before inserting the rock representative sample into the sample pile, prepare the mudstone and shale representative sample and the sample pile; The sample cup contains quartz sand; Insertion is performed in a vacuum environment, with the surface to be observed of the mudstone and shale representative sample facing upwards, and a portion of the rock representative sample is inserted into the quartz sand.

2. The method for preparing a multi-purpose rock experimental sample according to claim 1, characterized in that, The representative rock sample should meet the following conditions: The diameter of the surface to be observed in the rock representative sample is less than or equal to 10 mm, and the height is 10-15 mm. The rock sample described has no artificial cracks.

3. The method for preparing a multi-purpose rock experimental sample according to claim 1, characterized in that, The height of the quartz sand is 1 / 3 to 2 / 3 of the height of the sample cup, and the particle size of the quartz sand is 0.5-1mm; A label is affixed to the bottom of the labeling window, and the label records the sample sequence number and sample pile number of the mudstone and shale representative sample; The silicone mold has a silicone wall and silicone bottom that are both no less than 5mm thick, and an inner diameter of 36mm.

4. The method for preparing a multi-purpose rock experimental sample according to claim 1, characterized in that, Both the sample cup and the labeling window are flat-bottomed right-angled cups, and the flat-bottomed right-angled cups are made of transparent material.

5. The method for preparing a multi-purpose rock experimental sample according to claim 2, characterized in that, The side or part of the side of the rock representative sample is attached to the inner wall of the sample cup, and the overall height of the rock representative sample and the sample cup is 17mm to 19mm.

6. The method for preparing a multi-purpose rock experimental sample according to claim 1, characterized in that, The curing temperature is 80℃~90℃, and the curing time is more than 18 hours; The rock representative sample, quartz sand, and label in the solidified large sample are all transparent and identifiable.

7. A method for preparing a multi-purpose rock experimental sample according to claim 1 or 6, characterized in that, After the solidified sample is cut, coarsely ground and polished, the surface of the rock representative sample to be observed reaches the mirror finish standard.

8. A method for using a multi-purpose rock experimental sample, characterized in that, The sample is prepared by the preparation method according to any one of claims 1-7, and the method of use includes: analyzing and identifying the rock multi-purpose experimental sample using an optical microscope. After optical microscopy analysis and identification, the rocks are often subjected to carbon or gold plating on the experimental samples. In-situ analysis of multi-purpose rock samples after carbon and gold plating was performed using a combination of electron microscopy, energy dispersive spectroscopy, and electron probe microanalysis.

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