Method and system for identifying ocean-going deposition and semi-ocean-going deposition by utilizing deposition structure

Abstract

The invention discloses a method and a system for identifying ocean-going deposition and semi-ocean-going deposition by utilizing a sedimentary structure, and relates to the technical field of shale oil and shale gas exploration and development engineering, and the method comprises the following steps: S1, making and imaging a large shale slice; s2, identifying a horizontal stripe layer and a sequential composite gradient stripe layer group according to the shale large slice imaging data; and S3, identifying ocean-going deposition and semi-ocean-going deposition according to the horizontal stripe layer and the sequential composite gradient stripe layer group. According to the method, the sedimentary facies type is clarified by means of shale large slice imaging data bedding research on the basis of the basic knowledge of ocean sedimentary development page type horizontal bedding and semi-ocean sedimentary development sequential type composite gradient bedding under the strong reduction water body condition. The invention provides a new method for quickly and accurately identifying and distinguishing ocean-going deposition and semi-ocean-going deposition, so that a foundation is laid for optimizing favorable zones and targets of shale gas.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil and shale gas exploration and development engineering, and in particular to a method and system for identifying pelagic and semi-pelagic deposits by utilizing sedimentary structures. Background Art

[0002] Marine sedimentary systems primarily include turbidity currents, contour currents, and pelagic and semi-pelagic sedimentary systems. Shale oil and gas source rocks and organic-rich shale gas reservoirs are primarily found in pelagic and semi-pelagic sedimentary systems. Pelagic sediments form in completely stagnant waters. Sediments are primarily derived from vertical sedimentation, primarily of biogenic origin, with a smaller portion derived from fine-grained terrigenous material or other detrital material in surface waters. Hemipelagic sediments are sediments or sedimentary rocks composed of a mixture of biogenic material (generally greater than 10%) and terrigenous (or volcanic) material (generally greater than 10%). Compared with pelagic sediments, hemipelagic sediments are mostly formed in relatively stagnant water bodies, where there is both vertical sedimentation and slow lateral advection (such as the literature: Stow and Smille. Distinguishing between deep-water sediment facies: Turbidites, contourites and hemipelagites. Geosciences, 2020, 10, 68). The driving force of lateral advection in hemipelagic sedimentary environments comes from the inertia of rivers or turbidity plumes, the diffusion of glacial meltwater, internal waves and internal tides, and slow-flowing midwater currents. In addition, the advection of some fine-grained materials at a certain angle to the shelf or from the shelf to the slope, and the resuspension of seabed materials, also contribute to the lateral advection.

[0003] Pelagic and hemipelagic sediments are crucial source and reservoir rocks because their primary components are biogenic, with high organic carbon content, well-developed organic pores, and high concentrations of brittle minerals. Furthermore, due to their extremely slow sedimentation rates, these sediments have highly developed lamination and foliation, significantly impacting fracturing during shale oil and gas development.

[0004] Because pelagic and hemipelagic sediments are extremely fine-grained and cannot be observed with the naked eye, scholars have traditionally relied primarily on whole-rock XRD analysis and argon ion polishing scanning electron microscopy to analyze their sedimentary components (e.g., Zhao Chenglin, Principles of Sedimentology. Beijing: Petroleum Industry Press, 2001, 1-214). However, years of practice have shown that black shales undergo intense diagenetic alteration after deposition. The original components undergo diagenetic processes such as compaction, cementation, and recrystallization, resulting in significant changes in particle composition and size. Therefore, the accuracy of compositional identification is very low. Furthermore, because the formation process of black shales cannot be directly observed, it is generally impossible to visually determine whether the shales were formed by vertical subsidence, lateral advection, or other dynamic processes. Therefore, interpretations of their origin are not very reliable. In recent years, some researchers have found that in strongly reducing waters, where biological activity is weak or absent, the bedding structure of pelagic and hemipelagic sediments can be completely preserved. Pelagic sedimentation results from vertical subsidence, resulting in extremely low shale deposition rates (<1 cm / ka). Consequently, the resulting shales are primarily composed of thin horizontal laminae (<5 mm thick per layer) with book-shaped horizontal bedding. Hemipelagic sedimentation, a mixture of vertical subsidence and very weak lateral advection, with the latter exhibiting cyclical variations due to seasonal influences, results in relatively high deposition rates (5-15 cm / ka). Consequently, sequential, composite, graded bedding develops, with unclear laminar set boundaries and a characteristic gradual shift.

[0005] In black shales, book-shaped horizontal bedding refers to a type of bedding composed of horizontal laminae. This type of bedding often appears book-like and consists of a series of horizontal laminae with individual layers less than 5 mm thick, and the laminae interfaces are mostly parallel. Sequential composite gradational bedding refers to a type of shale bedding composed of a series of sequential composite gradational laminae. This type of bedding has well-developed lamina on the surface, but the laminae interfaces are often discontinuous or interwoven. Individual laminae are not identifiable within these gradational laminae, but the shale grain size gradually coarsens and then fines from bottom to top. Summary of the Invention

[0006] The present invention aims to provide a method and system for identifying pelagic and semi-pelagic deposits using sedimentary structures. By accurately identifying shale book-type horizontal bedding and sequential composite graded bedding, these deposits can be identified and differentiated. This allows for more accurate determination of the sweet spots and optimal target distribution of shale oil and gas, thereby improving drilling success rates and single-well production. To achieve this objective, the present invention provides the following technical solutions:

[0007] The present invention provides a method for identifying pelagic and hemipelagic deposits by using sedimentary structures, the method comprising:

[0008] Step S1, preparation and imaging of large shale slices;

[0009] Step S2: identifying horizontal laminae and sequential composite graded laminae groups based on shale thin section imaging data;

[0010] Step S3: identifying pelagic and hemipelagic deposits based on horizontal laminae and sequential composite graded laminae.

[0011] Furthermore, the step S2 of identifying horizontal laminae and sequential composite graded laminae groups based on shale thin section imaging data includes:

[0012] Step S21, identification of shale inner layer interfaces: in a large thin section, identification of shale layer interfaces based on lithologic abrupt changes, longitudinal grain size abrupt changes, compositional changes, stratigraphic pinch-outs, and biological colonization surfaces;

[0013] Step S22, division of shale inner layers: dividing the shale into multiple single layers according to the layer interface;

[0014] Step S23, identifying laminae interfaces within a single layer: within a single layer, identifying laminae interfaces based on the weak erosion characteristics of the shale, the discontinuity of the shale composition material structure, and the micro-sedimentary discontinuity characteristics;

[0015] Step S24, dividing the lamina groups according to the lamina group interfaces: dividing the single layer into a series of lamina groups or laminas according to the lamina group interfaces, requiring that there are no other erosion surfaces or sedimentary discontinuities within the divided lamina groups;

[0016] Step S25, determining the interface morphology and geometric relationship of the laminae group: if the laminae group interface is plate-shaped or wavy, and the upper and lower interfaces are parallel to each other, proceed to the next step;

[0017] Step S26, division of lamina within lamina group: for lamina groups with plate-like or wavy interfaces and parallel upper and lower interfaces, the lamina are divided based on slight differences in grain size, color, arrangement or mineral composition;

[0018] Step S27, division of laminae within laminae groups: for laminae groups with plate-like or wavy interface morphology, parallel upper and lower interfaces, and in which clear laminae interfaces are difficult to find, horizontal laminae are identified based on whether the thickness of a single layer is less than 5 mm; if the thickness of a single layer is less than 5 mm, it is determined to be a horizontal laminae;

[0019] Step S28, identification of sequential composite graded lamination groups: For lamination groups with plate-like or wavy interface morphology, parallel upper and lower interfaces, difficult to find clear lamination interfaces inside, and single-layer thickness greater than 1 mm, sequential composite graded lamination groups are identified based on their grain size variation characteristics; if the shale grain size shows a grain size variation pattern of first changing from fine to coarse and then from fine to coarse, it is determined to be a sequential composite graded lamination group.

[0020] Furthermore, the step S3 of identifying pelagic and hemipelagic sediments based on horizontal laminae and sequential composite graded laminae groups includes:

[0021] Step S31, determining the bedding type of the shale: observing a large thin section and determining the bedding type by identifying the laminae or laminae groups of the shale;

[0022] Step S32, determining pelagic and hemipelagic deposits: observing large thin sections, and determining pelagic and hemipelagic deposits based on the bedding type of the shale.

[0023] Furthermore, the step S31 of determining the bedding type of shale includes:

[0024] 1) Determination of book-shaped horizontal bedding: If the shale is composed of horizontal laminae and the thickness of a single horizontal laminae is less than 1 mm, then the shale is determined to have book-shaped horizontal bedding;

[0025] 2) Determination of sequential composite transitional bedding: If the shale is composed of sequential composite transitional lamination groups, it is determined that the shale has developed sequential composite transitional bedding.

[0026] Furthermore, the step S32 of determining the pelagic and semi-pelagic deposits includes:

[0027] 1) Determination of pelagic deposits: If the shale develops book-shaped horizontal bedding, it is determined to be a pelagic deposit;

[0028] 2) Determination of Hemipelagic Deposits: If the shale develops sequential composite graded bedding, and the laminae are not clearly plate-like or wavy, with a continuous transition relationship between the upper and lower interfaces, it is determined to be a Hemipelagic deposit.

[0029] The present invention also provides a system for identifying pelagic and hemipelagic deposits using sedimentary structures, the system comprising:

[0030] Shale large thin section production and imaging module, used for shale large thin section production and imaging;

[0031] Horizontal laminae and sequential composite graded laminae identification module, used to identify horizontal laminae and sequential composite graded laminae based on shale thin-section imaging data;

[0032] The module for identifying pelagic and hemipelagic deposits is used to identify pelagic and hemipelagic deposits based on horizontal laminae and sequential composite graded laminae.

[0033] Furthermore, the horizontal lamination and sequential composite graded lamination group identification module includes:

[0034] The layer interface identification unit is used to identify the interface of shale layers: in large thin sections, the layer interface of shale is identified based on lithologic mutation, longitudinal grain size mutation, composition change, stratigraphic pinch-out and biological colonization surface;

[0035] Layer division unit, used for dividing the inner layers of shale: shale is divided into multiple single layers according to the layer interface;

[0036] The laminae interface recognition unit is used to identify laminae interfaces within a single layer: within a single layer, laminae interfaces are identified based on the weak erosion characteristics of shale, the discontinuity of shale composition and the micro-sedimentary discontinuity characteristics;

[0037] Lamina group division unit is used to divide lamina groups according to the lamina group interface: a single layer is divided into a series of lamina groups or laminas according to the lamina group interface, and it is required that there are no other erosion surfaces or sedimentary discontinuities within the divided lamina groups;

[0038] The unit for determining the interface morphology and geometric relationship of the lamina group is used to determine the interface morphology and geometric relationship of the lamina group: if the lamina group interface is plate-shaped or wavy, and the upper and lower interfaces are parallel to each other, the next step is carried out;

[0039] Lamina division unit, used to divide lamina within a lamina group: for lamina groups with plate-like or wavy interfaces and parallel upper and lower interfaces, lamina division is based on slight differences in grain size, color, arrangement or mineral composition;

[0040] The horizontal laminae identification unit is used to identify horizontal laminae within a laminae group: for laminae groups with plate-like or wavy interfaces, parallel upper and lower interfaces, and where clear laminae interfaces are difficult to find, horizontal laminae are identified based on whether the thickness of a single layer is less than 5 mm. If the thickness of a single layer is less than 5 mm, it is determined to be a horizontal laminae.

[0041] The sequential composite graded lamination group identification unit is used to identify sequential composite graded lamination groups: for lamination groups with plate-like or wavy interface morphology, parallel upper and lower interfaces, difficulty in finding clear lamination interfaces inside, and single-layer thickness greater than 1 mm, sequential composite graded lamination groups are identified based on their grain size variation characteristics; if the shale grain size shows a grain size variation pattern from fine to coarse and then back again, it is determined to be a sequential composite graded lamination group.

[0042] Furthermore, the pelagic and semi-pelagic sediment identification module includes:

[0043] The shale bedding type determination unit is used to determine the bedding type of shale: observing large thin sections, the bedding type is determined by identifying the type of laminae or laminae groups of shale;

[0044] Determination of Pelagic and Hemipelagic Deposits Units used to determine Pelagic and Hemipelagic deposits: Observe large thin sections and determine Pelagic and Hemipelagic deposits based on the bedding type of shale.

[0045] Furthermore, the shale bedding type determination unit is specifically used to:

[0046] 1) Determination of book-shaped horizontal bedding: If the shale is composed of horizontal laminae and the thickness of a single horizontal laminae is less than 1 mm, then the shale is determined to have book-shaped horizontal bedding;

[0047] 2) Determination of sequential composite transitional bedding: If the shale is composed of sequential composite transitional lamination groups, it is determined that the shale has developed sequential composite transitional bedding.

[0048] Furthermore, the pelagic sedimentation and semi-pelagic determination unit is specifically used to:

[0049] 1) Determination of pelagic deposits: If the shale develops book-shaped horizontal bedding, it is determined to be a pelagic deposit;

[0050] 2) Determination of Hemipelagic Deposits: If the shale develops sequential composite graded bedding, and the laminae are not clearly plate-like or wavy, with a continuous transition relationship between the upper and lower interfaces, it is determined to be a Hemipelagic deposit.

[0051] Technical effects and advantages of the present invention:

[0052] This invention, based on the fundamental understanding that pelagic sediments develop book-shaped horizontal bedding and hemipelagic sediments develop sequential, composite graded bedding under strongly reducing water conditions, uses bedding analysis with large-thin shale imaging data to clarify sedimentary facies types. This invention provides a new method for rapidly and accurately identifying and differentiating pelagic and hemipelagic deposits, laying the foundation for selecting favorable shale gas zones and targets.

[0053] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0055] Figure 1 A flow chart of a method for identifying pelagic and semi-pelagic deposits using sedimentary structures according to the present invention;

[0056] Figure 2 for Figure 1 Detailed flow chart of step S2;

[0057] Figure 3 for Figure 1 Detailed flow chart of step S3;

[0058] Figure 4 This is a schematic diagram of the main identification marks of the black shale middle layer interface of the present invention;

[0059] Figure 5 Schematic diagram of the characteristics of book-page-type horizontal bedding and sequential composite graded bedding in black shale of the present invention; wherein a is book-page-type horizontal bedding, and b is sequential composite graded bedding;

[0060] Figure 6 The black shale slices of the present invention and their polarizing microscope images; a and b are large slices, and c is a polarizing microscope image of the large slice;

[0061] Figure 7 Schematic diagram of the method and characteristics of identifying horizontal laminae and horizontal bedding in black shale according to the present invention; wherein a is a core photo, and b is a large thin section imaging photo;

[0062] Figure 8 The following is a schematic diagram of the identification method and characteristics of the sequential composite graded lamination group and sequential composite graded bedding of black shale according to the present invention; wherein a is a core photo, and b is a large thin section imaging photo;

[0063] Figure 9 A schematic diagram of a system for identifying pelagic and semi-pelagic deposits using sedimentary structures according to the present invention;

[0064] Figure 10 for Figure 9 Detailed schematic diagram of the module for identifying medium-horizontal laminae and sequential composite graded laminae groups;

[0065] Figure 11 for Figure 9 Detailed schematic diagram of the mesopelagic and hemipelagic sediment identification modules. DETAILED DESCRIPTION

[0066] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0067] In order to solve the deficiencies of the prior art, the present invention discloses a method for identifying pelagic and semi-pelagic deposits by using sedimentary structures. Figure 1 This is a flow chart of a method for identifying pelagic and semi-pelagic deposits using sedimentary structures according to the present invention. Figure 1 As shown, the method includes: making and imaging large thin sections of shale, identifying horizontal laminae and sequential composite graded laminae, and identifying pelagic and hemipelagic deposits; the specific steps are as follows:

[0068] Step S1: Preparation and imaging of large shale slices:

[0069] The research content is to obtain large-thin slice image data of black shale through large-thin slice production and imaging of the collected shale samples. The specific operation steps are as follows:

[0070] Step S11: Make a large thin section. Perpendicular to the black shale bedding direction, make a large thin section with a length of 7 cm, a width of 5 cm, and a thickness of 0.03 mm. Mark the top and bottom of the formation. The specific specifications and production process of the large thin section refer to the petroleum and natural gas industry standard SY / T5913-94.

[0071] Step S12: Full-thin slice data acquisition and image stitching. This is divided into the following specific operation processes (for the specific operation process, please refer to the patent: Shale Bedding Identification Method (Patent No.: ZL201810598748.4))

[0072] 1) Use the German LEICA4500P high-precision digital microscope platform and a 20×1.5x lens to determine the diagonal position of the acquisition area and divide the slice into several squares according to the accuracy requirements;

[0073] 2) Select a diagonal (or cross, or tic-tac-toe, or even a grid) field of view for focus. The high-precision digital platform automatically records the focal length (Z value). When capturing an unfocused field of view, the focus is automatically adjusted based on the focal length of a nearby focused field of view. No manual adjustment of the Z-axis focus is required during the capture process.

[0074] 3) Use a high-precision digital platform to collect data on snake-shaped full-length thin sections;

[0075] 4) Select a high-configuration workstation and use Adobe Photoshop CS5 or above version of graphics processing software to seamlessly stitch together the large number of collected single photos. The stitching process is to first stitch together the 4 adjacent images into 1, and then stitch together the 4 synthesized adjacent large images again. Repeat this method until all stitching is completed.

[0076] Step S2: Identification of horizontal laminae and sequential composite graded laminae groups:

[0077] In black shale, the basic units of shale are laminae, laminae groups, and layers. Multiple laminae of related origins constitute a laminae group, while multiple laminae or laminae groups of similar origins constitute a layer. The key to identifying laminae and laminae groups is to first identify and delineate layers, then, within a single layer, delineate laminae groups based on laminae group interfaces, and finally, delineate laminae within laminae groups. This step focuses on identifying horizontal laminae. Figure 2 for Figure 1 The detailed flow chart of step S2 is as follows: Figure 2 The specific steps are as follows:

[0078] Step S21, identification of the inner interface of shale. In the large thin section, the interface of black shale is identified based on the lithologic mutation, longitudinal grain size mutation, composition change, stratum pinch-out (onlap, underlap and erosion), biological colonization surface, etc. Figure 4 Onlap is the geological phenomenon in which a set of inclined strata overlaps successively upward against the inclination of an originally steeper sedimentary surface; underlap is the basal overlap of an originally horizontal or inclined surface in a downward direction; and truncation is the lateral disappearance of a stratum due to erosion. A bioturbation surface is a surface in a stratum where organisms live due to low or absent sedimentation rates.

[0079] Step S22: Division of shale inner layers: Divide the shale into multiple single layers based on the layer interfaces.

[0080] Step S23: Identify the laminae interface within a single layer. Within a single layer, the laminae interface is identified based on the weak erosion characteristics of the shale, the discontinuity of the shale composition material structure, and micro-sedimentary discontinuities.

[0081] Step S24: Delineate lamina groups according to lamina group interfaces. Divide a single layer into a series of lamina groups (or laminae) according to the lamina group interfaces, requiring that no other erosion surfaces or sedimentary discontinuities exist within the divided lamina groups.

[0082] Step S25: Determine the interface morphology and geometric relationship of the laminae group. If the laminae group interface is plate-shaped or wavy, and the upper and lower interfaces are parallel to each other, proceed to the next step.

[0083] Step S26: Division of laminae within a laminae group. For laminae with plate-like or wavy interfaces and parallel upper and lower interfaces, laminae are divided based on slight differences in grain size, color, arrangement, or mineral composition. Individual laminae must be completely uniform in grain size, color, arrangement, or mineral composition, and no further subdivision is permitted.

[0084] Step S27, identification of horizontal laminae within the laminae group. For laminae groups with plate-like or wavy interface shapes, parallel upper and lower interfaces, and internal laminae with difficulty in finding clear laminae interfaces, horizontal laminae are identified based on whether the thickness of the single layer is less than 5 mm. If the thickness of the single layer is less than 5 mm, it is determined to be a horizontal laminae ( Figure 5 a).

[0085] Step S28, identification of sequential composite transitional laminations. For laminations with plate-like or wavy interface morphology, parallel upper and lower interfaces, difficulty in finding clear lamination interfaces inside, and single layer thickness greater than 1 mm, sequential composite transitional laminations are identified based on their grain size variation characteristics. If the shale grain size changes from fine to coarse and then from fine to coarse, it is identified as a sequential composite transitional lamination ( Figure 5 b). The solid red line represents the laminae interface, and the dashed red line represents the laminae group interface.

[0086] Step S3: Determination of Pelagic and Semi-Pelagic Deposits:

[0087] The purpose of this step is to determine the bedding type of black shale, thereby determining whether it is pelagic or hemipelagic. Figure 3 for Figure 1 The detailed flow chart of step S3 is as follows: Figure 3 The specific steps are as follows:

[0088] Step S31: Determine the bedding type of the shale. Observe a large thin section and determine the bedding type by identifying the laminae or laminae groups of the shale.

[0089] 1) Determination of book-shaped horizontal bedding. If the black shale is composed of horizontal laminae and the thickness of a single horizontal laminae is less than 1 mm, it is determined that the shale has developed book-shaped horizontal bedding ( Figure 5 a).

[0090] 2) Determination of sequential composite transitional bedding. If the black shale is composed of sequential composite transitional lamination groups, it is determined that the shale has developed sequential composite transitional bedding ( Figure 5 b).

[0091] Step S32: Determine pelagic and hemipelagic deposits. Observe large thin sections and determine pelagic and hemipelagic deposits based on the bedding type of the shale. This step mainly includes the following processes:

[0092] 1) Determination of pelagic deposits: If the shale exhibits book-shaped horizontal bedding, it is determined to be pelagic.

[0093] 2) Determination of Hemipelagic Deposits: If the shale develops sequential composite graded bedding, and the laminae are unclear, plate-like, and wavy, with a continuous transitional relationship between the upper and lower laminae, it is determined to be a hemipelagic deposit.

[0094] Example:

[0095] Taking the black shale cores from the Wufeng and Longmaxi Formations in southern Sichuan as an example, by preparing and imaging large thin core sections, identifying horizontal laminae and sequential composite graded laminae, and identifying horizontal bedding and sequential composite graded bedding, we can quickly and accurately identify and differentiate between pelagic and hemipelagic deposits:

[0096] Step S1: Preparation and imaging of large shale slices:

[0097] The research content is to obtain large thin-section image data of black shale. The specific steps are as follows:

[0098] Step S11, collect core data and make large thin slices. Vertically along the bedding direction of the black shale core, make large thin slices of 7 cm long × 5 cm wide × 0.03 mm thick, and standardize the top and bottom of the formation ( Figure 6 a, 6b);

[0099] Step S12: Full-thin slice data acquisition and image stitching. This is divided into the following specific operation processes (for the specific operation process, please refer to the patent: Shale Bedding Identification Method (Patent No.: ZL201810598748.4))

[0100] 1) Use the German LEICA4500P high-precision digital microscope platform and a 20×1.5x lens to determine the diagonal position of the acquisition area and divide the slice into several squares according to the accuracy requirements;

[0101] 2) Select a diagonal (or cross, or tic-tac-toe, or even a grid) field of view for focus. The high-precision digital platform automatically records the focal length (Z value). When capturing an unfocused field of view, the focus is automatically adjusted based on the focal length of a nearby focused field of view. No manual adjustment of the Z-axis focus is required during the capture process.

[0102] 3) Use a high-precision digital platform to collect data on snake-shaped full-length thin sections;

[0103] 4) Use a high-end workstation and Adobe Photoshop CS5 or above graphics processing software to seamlessly stitch together the large number of collected single photos. The stitching process is to first stitch together 4 adjacent images into 1, and then stitch together the 4 adjacent large images. Repeat this method until all stitching is completed. Figure 6 c).

[0104] Step S2: Identification of horizontal laminae and sequential composite graded laminae groups:

[0105] Using large-section imaging data, horizontal laminae and sequential composite graded laminae can be identified by identifying layer interfaces, laminae group interfaces, laminae interfaces, and single-layer thickness. The specific steps are as follows:

[0106] Step S21: Identification of shale inner layer interfaces. In the large thin-section imaging photograph, the black shale layer interfaces are identified based on lithologic abrupt changes, longitudinal grain size abrupt changes, compositional changes, stratigraphic pinch-outs (onlap, underlap, and erosion), and biological colonization surfaces.

[0107] Step S22: Division of shale inner layers: Divide the shale into multiple single layers based on the layer interfaces.

[0108] Step S23: Identify the laminae interface within a single layer. Within a single layer, based on the weak erosion characteristics of shale, the discontinuity of the shale composition material structure, micro-sedimentary discontinuities and other characteristics, identify the laminae interface ( Figure 7 b).

[0109] Step S24: Delineate lamina groups according to lamina group interfaces. Divide a single layer into a series of lamina groups (or laminae) according to the lamina group interfaces, requiring that no other erosion surfaces or sedimentary discontinuities exist within the divided lamina groups.

[0110] Step S25: Determine the interface morphology and geometric relationship of the laminae group. If the laminae group interface is plate-shaped or wavy, and the upper and lower interfaces are parallel to each other, proceed to the next step.

[0111] Step S26: Division of laminae within a laminae group. For laminae with plate-like or wavy interfaces and parallel upper and lower interfaces, laminae are divided based on slight differences in grain size, color, arrangement, or mineral composition. Individual laminae must be completely uniform in grain size, color, arrangement, or mineral composition, and no further subdivision is permitted.

[0112] Step S27: Division of laminae within laminae groups. For laminae groups with plate-like or wavy interfaces, parallel upper and lower interfaces, and where it is difficult to find clear laminae interfaces, horizontal laminae are identified based on whether the thickness of a single layer is less than 5 mm. If the thickness of a single layer is less than 5 mm, it is determined to be a horizontal laminae ( Figure 7 b).

[0113] Step S28, identification of sequential composite transitional lamination groups. For lamination groups with plate-like or wavy interface morphology, parallel upper and lower interfaces, internal lamination interfaces that are difficult to find clearly, and single layer thickness greater than 5mm, sequential composite transitional lamination groups are identified based on their grain size variation characteristics. If the shale grain size changes from fine to coarse and then from fine to coarse, it is determined to be a sequential composite transitional lamination group ( Figure 7 ).

[0114] Step S3: Determination of Pelagic and Semi-Pelagic Deposits:

[0115] Step S31: Determine the bedding type of the shale. Observe a large thin section and determine the bedding type by identifying the laminae or laminae groups of the shale.

[0116] 1) Determination of book-shaped horizontal bedding. If the black shale is composed of horizontal laminae and the thickness of a single horizontal laminae is less than 1 mm, it is determined that the shale has developed book-shaped horizontal bedding ( Figure 7 ).

[0117] 2) Determination of sequential composite transitional bedding. If the black shale is composed of sequential composite transitional lamination groups, it is determined that the shale has developed sequential composite transitional bedding ( Figure 8 ).

[0118] Step S32: Determine the pelagic and semi-pelagic deposits. Determine the pelagic and semi-pelagic deposits based on the shale bedding type. This step mainly includes the following process:

[0119] 1) Pelagic deposits. If the shale has book-shaped horizontal bedding, it is determined to be a pelagic deposit.

[0120] 2) Hemipelagic sediments. If the shale develops sequential composite graded bedding, and the laminae are not clearly plate-like or wavy, with a continuous transitional relationship between the upper and lower interfaces, it is determined to be hemipelagic.

[0121] Based on the same concept, the present invention also discloses a system for identifying pelagic and semi-pelagic deposits using sedimentary structures. Figure 9 Schematic diagram of a system for identifying pelagic and semi-pelagic deposits using sedimentary structures according to the present invention. Figure 9 As shown, the system includes: a shale thin section production and imaging module 201, which is used for producing and imaging shale thin sections; a horizontal lamination and sequential compound transitional lamination group identification module 202, which is used for identifying horizontal laminations and sequential compound transitional lamination groups based on shale thin section imaging data; and a pelagic deposit and semi-pelagic deposit identification module 203, which is used for identifying pelagic deposits and semi-pelagic deposits based on horizontal laminations and sequential compound transitional lamination groups.

[0122] Further, Figure 10 for Figure 9 Detailed schematic diagram of the identification module for medium-horizontal laminae and sequential composite graded laminae groups, as shown in Figure 10 As shown, the horizontal lamination and sequential composite transition lamination group identification module 202 includes: a layer interface identification unit 2021 for identifying the inner layer interface of shale: in a large thin slice, the layer interface of shale is identified based on lithologic mutation, longitudinal grain size mutation, composition change, stratigraphic pinch-out and biological colonization surface; a layer division unit 2022 for dividing the inner layer of shale: the shale is divided into multiple single layers based on the layer interface; a laminae group interface identification unit 2023 for identifying the laminae group interface in a single layer: in a single layer, the laminae group interface is identified based on the lithologic mutation, longitudinal grain size mutation, composition change, stratigraphic pinch-out and biological colonization surface; The weak erosion characteristics of shale, the discontinuity of shale composition and the micro-sedimentary discontinuity characteristics are used to identify the laminae interface; the laminae group division unit 2024 is used to divide the laminae according to the laminae interface: according to the laminae interface, a single layer is divided into a series of laminae or laminae, and it is required that there are no other erosion surfaces or sedimentary discontinuities in the divided laminae; the laminae interface morphology and geometric relationship determination unit 2025 is used to determine the interface morphology and geometric relationship of the laminae: if the laminae interface is plate-like or wavy, If the upper and lower interfaces are parallel to each other, the next step is carried out; the laminae division unit 2026 is used to divide the laminae within the laminae group: for laminae groups with plate-shaped or wavy interfaces and parallel upper and lower interfaces, the laminae are divided according to slight differences in grain size, color, arrangement or mineral composition; the horizontal laminae identification unit 2027 is used to identify horizontal laminae within the laminae group: for laminae groups with plate-shaped or wavy interfaces, parallel upper and lower interfaces, and where it is difficult to find a clear laminae interface inside, the horizontal laminae are identified based on whether the single layer thickness is less than 5 mm. Identify horizontal laminae; if the thickness of a single layer is less than 5 mm, it is determined to be a horizontal laminae; the sequential composite graded laminae group identification unit 2028 is used to identify sequential composite graded laminae groups: for laminae groups with plate-like or wavy interface morphology, parallel upper and lower interfaces, difficulty in finding clear laminae interfaces inside, and single layer thickness greater than 1 mm, determine the sequential composite graded laminae group based on their grain size variation characteristics; if the shale grain size has a grain size variation pattern of first changing from fine to coarse and then from fine to coarse, it is determined to be a sequential composite graded laminae group.

[0123] Further, Figure 11 for Figure 9 Detailed schematic diagram of the mesopelagic and hemipelagic sediment identification module, such as Figure 11 As shown, the pelagic and semi-pelagic deposit identification module 203 includes: a shale bedding type determination unit 2031, used to determine the bedding type of shale: observing a large thin section, and determining the bedding type by identifying the lamination or lamination group type of the shale; a pelagic and semi-pelagic deposit determination unit 2032, used to determine pelagic and semi-pelagic deposits: observing a large thin section, and determining pelagic and semi-pelagic deposits according to the bedding type of the shale.

[0124] Furthermore, the shale bedding type determination unit 2031 is specifically used for: 1) determining book-type horizontal bedding: if the shale is composed of horizontal laminae and the single-layer thickness of the horizontal laminae is <1 mm, then it is determined that the shale develops book-type horizontal bedding; 2) determining sequential composite transitional bedding: if the shale is composed of sequential composite transitional laminae groups, then it is determined that the shale develops sequential composite transitional bedding.

[0125] Furthermore, the pelagic and semi-pelagic determination unit 2032 is specifically used for: 1) determining pelagic deposits: if the shale develops book-shaped horizontal bedding, the shale is determined to be pelagic deposits; 2) determining semi-pelagic deposits: if the shale develops sequential composite graded bedding, and the laminae interface is unclear plate-like and wavy, and the interface shows a continuous transition relationship above and below, it is determined to be semi-pelagic deposits.

[0126] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for identifying pelagic and hemipelagic deposits using sedimentary structures, characterized in that: The method comprises: Step S1, preparation and imaging of large shale slices; Step S2: identifying horizontal laminae and sequential composite graded laminae groups based on shale thin section imaging data; Step S3: identifying pelagic and hemipelagic deposits based on horizontal laminae and sequential composite graded laminae.

2. The method for identifying pelagic and hemipelagic deposits by using sedimentary structures according to claim 1, characterized in that: The step S2 of identifying horizontal laminae and sequential composite transitional laminae groups based on shale thin-section imaging data includes: Step S21, identification of shale inner layer interfaces: in a large thin section, identification of shale layer interfaces based on lithologic abrupt changes, longitudinal grain size abrupt changes, compositional changes, stratigraphic pinch-outs, and biological colonization surfaces; Step S22, division of shale inner layers: dividing the shale into multiple single layers according to the layer interface; Step S23, identifying laminae interfaces within a single layer: within a single layer, identifying laminae interfaces based on the weak erosion characteristics of the shale, the discontinuity of the shale composition material structure, and the micro-sedimentary discontinuity characteristics; Step S24, dividing the lamina groups according to the lamina group interfaces: dividing the single layer into a series of lamina groups or laminas according to the lamina group interfaces, requiring that there are no other erosion surfaces or sedimentary discontinuities within the divided lamina groups; Step S25, determining the interface morphology and geometric relationship of the laminae group: if the laminae group interface is plate-shaped or wavy, and the upper and lower interfaces are parallel to each other, proceed to the next step; Step S26, division of lamina within lamina group: for lamina groups with plate-like or wavy interfaces and parallel upper and lower interfaces, the lamina are divided based on slight differences in grain size, color, arrangement or mineral composition; Step S27, division of laminae within laminae groups: for laminae groups with plate-like or wavy interface morphology, parallel upper and lower interfaces, and in which clear laminae interfaces are difficult to find, horizontal laminae are identified based on whether the thickness of a single layer is less than 5 mm; if the thickness of a single layer is less than 5 mm, it is determined to be a horizontal laminae; Step S28, identification of sequential composite graded lamination groups: For lamination groups with plate-like or wavy interface morphology, parallel upper and lower interfaces, difficult to find clear lamination interfaces inside, and single-layer thickness greater than 1 mm, sequential composite graded lamination groups are identified based on their grain size variation characteristics; if the shale grain size shows a grain size variation pattern of first changing from fine to coarse and then from fine to coarse, it is determined to be a sequential composite graded lamination group.

3. The method for identifying pelagic and hemipelagic deposits by using sedimentary structures according to claim 1 or 2, characterized in that: The step S3 of identifying pelagic and hemipelagic sediments based on horizontal laminae and sequential composite graded laminae groups includes: Step S31, determining the bedding type of the shale: observing a large thin section and determining the bedding type by identifying the laminae or laminae groups of the shale; Step S32, determining pelagic and hemipelagic deposits: observing large thin sections, and determining pelagic and hemipelagic deposits based on the bedding type of the shale.

4. The method for identifying pelagic and hemipelagic deposits by using sedimentary structures according to claim 3, characterized in that: The step S31 of determining the bedding type of shale includes: 1) Determination of book-shaped horizontal bedding: If the shale is composed of horizontal laminae and the thickness of a single horizontal laminae is less than 1 mm, then the shale is determined to have book-shaped horizontal bedding; 2) Determination of sequential composite transitional bedding: If the shale is composed of sequential composite transitional lamination groups, it is determined that the shale has developed sequential composite transitional bedding.

5. The method for identifying pelagic and hemipelagic deposits by using sedimentary structures according to claim 3 or 4, characterized in that: The step S32 of determining the pelagic and semi-pelagic deposits includes: 1) Determination of pelagic deposits: If the shale develops book-shaped horizontal bedding, it is determined to be a pelagic deposit; 2) Determination of Hemipelagic Deposits: If the shale develops sequential composite graded bedding, and the laminae are not clearly plate-like or wavy, with a continuous transition relationship between the upper and lower interfaces, it is determined to be a Hemipelagic deposit.

6. A system for identifying pelagic and hemipelagic deposits using sedimentary structures, characterized in that: The system comprises: Shale large thin section production and imaging module, used for shale large thin section production and imaging; Horizontal laminae and sequential composite graded laminae identification module, used to identify horizontal laminae and sequential composite graded laminae based on shale thin-section imaging data; The module for identifying pelagic and hemipelagic deposits is used to identify pelagic and hemipelagic deposits based on horizontal laminae and sequential composite graded laminae.

7. The system for identifying pelagic and hemipelagic deposits using sedimentary structures according to claim 6, characterized in that: The horizontal lamination and sequential composite graded lamination group identification module includes: The layer interface identification unit is used to identify the interface of shale layers: in large thin sections, the layer interface of shale is identified based on lithologic mutation, longitudinal grain size mutation, composition change, stratigraphic pinch-out and biological colonization surface; Layer division unit, used for dividing the inner layers of shale: shale is divided into multiple single layers according to the layer interface; The laminae interface recognition unit is used to identify laminae interfaces within a single layer: within a single layer, laminae interfaces are identified based on the weak erosion characteristics of shale, the discontinuity of shale composition and the micro-sedimentary discontinuity characteristics; Lamina group division unit is used to divide lamina groups according to the lamina group interface: a single layer is divided into a series of lamina groups or laminas according to the lamina group interface, and it is required that there are no other erosion surfaces or sedimentary discontinuities within the divided lamina groups; The unit for determining the interface morphology and geometric relationship of the lamina group is used to determine the interface morphology and geometric relationship of the lamina group: if the lamina group interface is plate-shaped or wavy, and the upper and lower interfaces are parallel to each other, the next step is carried out; Lamina division unit, used to divide lamina within a lamina group: for lamina groups with plate-like or wavy interfaces and parallel upper and lower interfaces, lamina division is based on slight differences in grain size, color, arrangement or mineral composition; The horizontal laminae identification unit is used to identify horizontal laminae within a laminae group: for laminae groups with plate-like or wavy interfaces, parallel upper and lower interfaces, and where clear laminae interfaces are difficult to find, horizontal laminae are identified based on whether the thickness of a single layer is less than 5 mm. If the thickness of a single layer is less than 5 mm, it is determined to be a horizontal laminae. The sequential composite graded lamination group identification unit is used to identify sequential composite graded lamination groups: for lamination groups with plate-like or wavy interface morphology, parallel upper and lower interfaces, difficulty in finding clear lamination interfaces inside, and single-layer thickness greater than 1 mm, sequential composite graded lamination groups are identified based on their grain size variation characteristics; if the shale grain size shows a grain size variation pattern from fine to coarse and then back again, it is determined to be a sequential composite graded lamination group.

8. The system for identifying pelagic and hemipelagic deposits using sedimentary structures according to claim 6, characterized in that: The pelagic and semi-pelagic sediment identification module includes: The shale bedding type determination unit is used to determine the bedding type of shale: observing large thin sections, the bedding type is determined by identifying the type of laminae or laminae groups of shale; Determination of Pelagic and Hemipelagic Deposits Units used to determine Pelagic and Hemipelagic deposits: Observe large thin sections and determine Pelagic and Hemipelagic deposits based on the bedding type of shale.

9. The system for identifying pelagic and hemipelagic deposits using sedimentary structures according to claim 8, characterized in that: The shale bedding type determination unit is specifically used for: 1) Determination of book-shaped horizontal bedding: If the shale is composed of horizontal laminae and the thickness of a single horizontal laminae is less than 1 mm, then the shale is determined to have book-shaped horizontal bedding; 2) Determination of sequential composite transitional bedding: If the shale is composed of sequential composite transitional lamination groups, it is determined that the shale has developed sequential composite transitional bedding.

10. A system for identifying pelagic and hemipelagic deposits using sedimentary structures according to claim 8 or 9, characterized in that: The pelagic sediment and semi-pelagic determination unit is specifically used for: 1) Determination of pelagic deposits: If the shale develops book-shaped horizontal bedding, it is determined to be a pelagic deposit; 2) Determination of Hemipelagic Deposits: If the shale develops sequential composite graded bedding, and the laminae are not clearly plate-like or wavy, with a continuous transition relationship between the upper and lower interfaces, it is determined to be a Hemipelagic deposit.

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