Method for judging ancient ocean water environment

Abstract

The invention provides a method for judging an ancient ocean water body environment. The method comprises the following steps: acquiring a core sample of a target shale reservoir in a work area; wherein the target shale reservoir is a radioactive insect siliceous shale formation; based on the core sample of the target shale reservoir, determining the composition of a silicon shell cavity filler in the target shale reservoir and the filling amount of calcite in a silicon shell cavity; and according to the composition of the silicon shell cavity filler in the target shale reservoir and the filling amount of the calcite in the silicon shell cavity, determining the ancient ocean water body environment of the target shale reservoir in the work area in the deposition period. According to the method for judging the ancient ocean water body environment, the oxidation-reduction state of the ancient ocean deepwater body and the precipitation and dissolution conditions of calcite can be effectively combined, so that the reconstruction of the ancient ocean environment is better promoted.

Description

Technical Field

[0001] This invention relates to a method for determining the environment of ancient oceanic bodies. Background Technology

[0002] The paleooceanic deep-water environment mainly includes the redox state of the paleooceanic deep-water body and the conditions for calcite precipitation and dissolution. Reconstructing the redox state of the paleooceanic deep-water body and the conditions for calcite precipitation and dissolution is of great significance for understanding the evolution of life, ocean currents, seawater chemistry, sediment distribution, carbon cycle, and the enrichment and preservation of organic matter.

[0003] Earth's oceans have undergone a transition from anoxic to oxygen-rich states. Early anoxic water bodies possessed a "sulfide wedge" chemical structure, while modern oxygen-rich water bodies have pore water in their sediments containing oxidation zones and NO2. - Mn 2+ Fe 2+ Chemical zoning such as H2S and CH4. The gradual enrichment of Earth's oceans with oxygen can be understood as the continuous oxidation and reduction of substances by oxygen released by biological photosynthesis. The redox state of the ocean in a local area or on a shorter time scale is mainly controlled by the supply balance between organic matter and various oxidants in the region. Dissolved oxygen is the most important oxidant, and the redox state of the ocean is usually described by terms such as oxygen-rich, oxygen-depleted, and oxygen-deficient sulfidation. For the redox state of ancient oceans, some geochemical information in rocks is usually used to infer it. The shortcomings are: (1) it is assumed that the surface water of ancient oceans is oxygen-rich and the deep water is oxygen-depleted or oxygen-deficient; (2) the relationship between geochemical data such as trace elements, TOC, isotopes, and biomarkers and minerals and organic matter is extremely complex and has strong ambiguity.

[0004] Calcite is a metabolic product of microorganisms that secrete calcium carbonate in the ocean surface. The most significant change that occurs during the settling of calcite from the ocean surface to the seabed is dissolution. The Carbonate Compensation Depth (CCD), Carbonate Lysocline Depth (CLD), and Carbonate Saturability Depth (CSD) are three important depth interfaces for studying calcite dissolution. The CSD is the transition depth at which calcium carbonate in ocean waters changes from saturated to unsaturated, resulting in significant calcite dissolution. The CLD is the calcite dissolution inflection point; above it, calcite dissolution is weak, while below it, calcite dissolution is abundant. The CCD resembles the snow line on land; shallower sediments are rich in calcite, while deeper sediments are poor in calcite. In practice, a calcite content of 2%, 10%, or 20% is usually considered as the CCD.

[0005] Previous research has shown that the redox state of deep-sea paleooceanography and the precipitation and dissolution conditions of calcite were studied separately. The oxygen-rich, oxygen-depleted, and anoxic sulfidation conditions of the water, as well as the CSD, CLD, and CCD of calcite in the water, were treated in isolation. It was assumed that CSD, CLD, and CCD were simply a result of increased calcite solubility with increasing seawater depth and had no correlation with the redox state of the water. This is inconsistent with reality and seriously hinders the reconstruction of paleooceanic environments.

[0006] In summary, new methods and technologies for assessing ancient marine environments are still needed to effectively combine the redox state of deep-sea waters with the precipitation and dissolution conditions of calcite, thereby better enabling the reconstruction of ancient marine environments. Summary of the Invention

[0007] The purpose of this invention is to provide a technical solution for judging the paleooceanic water environment by effectively combining the redox state of the deep water of ancient oceans with the precipitation and dissolution conditions of calcite, thereby better promoting the reconstruction of the paleooceanic environment.

[0008] To achieve the above objectives, the present invention provides a method for determining the paleooceanic water environment, the method comprising:

[0009] Core samples were obtained from the target shale reservoir in the work area; wherein the target shale reservoir is radiolarian siliceous shale with lamellar formations.

[0010] Based on core samples from the target shale reservoir, the composition of the silica cavity filling material and the amount of calcite filling the silica cavity were determined.

[0011] Based on the composition of the silica cavity filling material and the amount of calcite filling the silica cavity in the target shale reservoir, the paleooceanic water environment during the depositional period of the target shale reservoir in the work area was determined; among which...

[0012] If the silica cavity filling material in the target shale reservoir is composed of a composite of calcite and organosilicon particles and the calcite filling amount in the silica cavity is less than 80%, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above the CSD; the upper part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between CSD and CLD; the lower part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between CLD and CCD.

[0013] If the silica cavity filling material in the target shale reservoir is composed of calcite, organosilicon particle complex and pyrite, and the filling amount of calcite in the silica cavity is less than 80%, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above CSD; the upper part of the deep water body is dilute oxygen (dissolved oxygen ≤ 2.0 ml / L) and located between CSD and CLD; the middle part of the deep water body is dilute oxygen (dissolved oxygen ≤ 2.0 ml / L) and located between CLD and CCD; and the lower part of the deep water body is anoxic (anaerobic) and sulfided and located between CLD and CCD.

[0014] If the silica cavity filling material in the target shale reservoir is composed of a complex of pyrite and organosilicon particles, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above the CSD; the upper part of the deep water is dilute (dissolved oxygen ≤ 2.0 ml / L) and located between the CSD and CLD; the middle part of the deep water is dilute (dissolved oxygen ≤ 2.0 ml / L) and located between the CLD and CCD; the lower part of the deep water is anoxic (anaerobic) and sulfided and located between the CLD and CCD; and the bottom of the deep water is anoxic (anaerobic) and sulfided and located below the CCD.

[0015] The method for determining the paleooceanic water environment provided by this invention pioneers the use of petrological characteristics of radiolarian siliceous shale lamellar radiolarian siliceous cavity-filling materials to determine the redox state of paleooceanic deep-water bodies and the CSD, CLD, and CCD conditions of calcite. It effectively combines the redox state of paleooceanic deep-water bodies with the precipitation and dissolution conditions of calcite, which is of great significance for reconstructing paleooceanic environments and understanding life evolution, seawater chemical conditions, sediment distribution, carbon cycle, and the enrichment and preservation of organic matter.

[0016] According to a specific implementation method for determining the paleooceanic water environment, preferably, obtaining core samples from the target shale reservoir in the work area includes:

[0017] Obtain rock cores from the work area;

[0018] The longitudinal sections of the core samples from the work area were observed to determine the laminar texture of the radiolarian siliceous shale.

[0019] Radiolarian siliceous shale lamellar rock samples were taken as core samples of the target shale reservoir in the work area.

[0020] According to the specific implementation method of the method for judging the paleooceanic water environment, preferably, the composition of the silica cavity filling material in the target shale reservoir is determined based on the core sample of the target shale reservoir, including:

[0021] Prepare thin sections of core samples from the target shale reservoir;

[0022] Electron probe microscopy was used to observe thin sections of cores from the target shale reservoir to identify the individual silica shells (including intact and incomplete silica shells) within the core sections.

[0023] Elemental surface scans of C, Si, Ca, Mg, Al, Fe, S, and O were performed on each silica shell in the target shale reservoir core thin section. Based on the C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scan results of each silica shell in the target shale reservoir core thin section, the composition of the silica shell cavity filling material in each silica shell in the target shale reservoir core thin section was preliminarily determined. Based on the preliminarily determined composition of the silica shell cavity filling material in each silica shell in the target shale reservoir core thin section, it was preliminarily determined whether the composition of the silica shell cavity filling material in the target shale reservoir core thin section was composed of calcite and fine-grained C and Si materials, or calcite, pyrite and fine-grained C and Si materials, or pyrite and fine-grained C and Si materials.

[0024] Argon-ion polished sections of the target shale reservoir were prepared based on core thin sections of the target shale reservoir. Based on the argon-ion polished sections of the target shale reservoir, MAPS rock image data volumes were obtained from the fine-grained C and Si materials in the silica cavity filling material. Based on the obtained MAPS rock image data volumes of the fine-grained C and Si materials, it was determined whether the fine-grained C and Si materials in the silica cavity filling material were organosilicon particle complexes.

[0025] If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of calcite and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of calcite and organosilicon particle complexes.

[0026] If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of calcite, pyrite, and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of calcite, organosilicon particle complexes, and pyrite.

[0027] If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of pyrite and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of pyrite and organosilicon particle complexes.

[0028] More preferably, when the composition of the silica cavity filling material of each silica shell in the core thin section of the target shale reservoir is independently selected from one of the following: composed of calcite and fine-grained C and fine-grained Si, composed of calcite, or composed of fine-grained C and fine-grained Si, and there is at least one silica cavity filling material containing calcite, and at least one silica cavity filling material containing fine-grained C and fine-grained Si, then the silica cavity filling material in the target shale reservoir is composed of calcite and fine-grained C and fine-grained Si.

[0029] More preferably, when the composition of the silica cavity filling material of each silica shell in the core thin section of the target shale reservoir is independently selected from one of the following: composed of calcite and pyrite and fine-grained C and fine-grained Si, composed of calcite and pyrite, composed of calcite and fine-grained C and fine-grained Si, composed of pyrite and fine-grained C and fine-grained Si, composed of calcite, composed of fine-grained C and fine-grained Si, or composed of pyrite, and at least one silica cavity filling material contains calcite, at least one silica cavity filling material contains pyrite, or at least one silica cavity filling material contains fine-grained C and fine-grained Si, then the silica cavity filling material in the target shale reservoir is composed of calcite, pyrite and fine-grained C and fine-grained Si.

[0030] More preferably, when the composition of the silica cavity filling material of each silica shell in the core thin section of the target shale reservoir is independently selected from one of the following: composed of pyrite and fine-grained C and fine-grained Si, composed of fine-grained C and fine-grained Si, or composed of pyrite, and there is at least one silica cavity filling material containing pyrite, and at least one silica cavity filling material containing fine-grained C and fine-grained Si, then the silica cavity filling material in the target shale reservoir is composed of pyrite and fine-grained C and fine-grained Si.

[0031] According to the specific implementation method of the method for judging the paleooceanic water environment, preferably, based on the core sample of the target shale reservoir, the determination of the filling amount of calcite in the silica cavity of the target shale reservoir includes:

[0032] Prepare thin sections of core samples from the target shale reservoir;

[0033] Electron probe microscopy was used to observe thin sections of cores from the target shale reservoir to identify the individual silica shells (including intact and incomplete silica shells) within the core sections.

[0034] C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scans were performed on each silica shell in the core thin section of the target shale reservoir. Based on the C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scan results of each silica shell in the core thin section of the target shale reservoir, the calcite in the silica shell cavity filling material of each silica shell in the core thin section of the target shale reservoir was preliminarily determined.

[0035] Based on the surface scanning results of C, Si, Ca, Mg, Al, Fe, S and O elements in each silica shell of the target shale reservoir core thin section, the area of ​​the silica shell cavity and the area of ​​the calcite filling material in the cavity of each silica shell in the target shale reservoir core thin section are determined.

[0036] Based on the area of ​​the silica cavity of each silica shell in the core thin section of the target shale reservoir and the area of ​​calcite in the cavity filling material, the total area of ​​the silica cavity of each silica shell in the core thin section of the target shale reservoir and the total area of ​​calcite in the cavity filling material of each silica shell are determined.

[0037] Based on the total area of ​​the silica cavities in each silica shell and the total area of ​​calcite in the cavity filling material of each silica shell in the core thin section of the target shale reservoir, the filling amount of calcite in the silica cavities of the target shale reservoir is determined; wherein, the filling amount of calcite in the silica cavities = the total area of ​​calcite in the cavity filling material of each silica shell ÷ the total area of ​​the silica cavities of each silica shell.

[0038] According to the specific implementation method of the method for judging the ancient ocean water environment, preferably, the core section of the target shale reservoir has a length of 2.5-7cm (e.g., 5cm), a width of 2.5-5cm (e.g., 2.5cm), and a thickness of 30-40μm (e.g., 35μm).

[0039] According to the specific implementation method of the method for judging the ancient ocean water environment, preferably, before observing the target shale reservoir core thin section under an electron probe microscope, a platinum film is coated on the surface of the target shale reservoir core thin section; wherein, the thickness of the platinum film may be, but is not limited to, 5 nm.

[0040] According to the specific implementation method of the method for judging the ancient ocean water environment, preferably, the top and bottom surfaces of the target shale reservoir core section are parallel to the top and bottom surfaces of the target shale reservoir core sample in the underground state.

[0041] According to the specific implementation method of the method for judging the ancient ocean water environment, preferably, during the observation of the target shale reservoir core thin section under an electron probe microscope, the top and bottom surfaces of the target shale reservoir core thin section are kept at the top and bottom surfaces of the field of view, respectively.

[0042] According to the specific implementation method of the method for judging the ancient ocean water environment, preferably, the length of the argon ion polishing sheet of the target shale reservoir is 0.8-2cm (e.g., 1cm), the width is 0.8-2cm (e.g., 1cm), and the thickness is 0.3-0.8cm (e.g., 0.5cm).

[0043] According to the specific implementation method of the method for judging the ancient ocean water environment, preferably, the top and bottom surfaces of the argon ion polished sheet of the target shale reservoir are parallel to the top and bottom surfaces of the core sample of the target shale reservoir in the underground state.

[0044] According to the specific implementation method of judging the ancient ocean water environment, preferably, during the acquisition of MAPS rock image data of C fine-grained material and Si fine-grained material in the silica shell cavity filling material, the top and bottom surfaces of the argon ion polishing sheet of the target shale reservoir are kept at the top and bottom surfaces of the field of view, respectively.

[0045] According to the specific implementation method of the method for judging the ancient ocean water environment, preferably, before acquiring MAPS rock image data of C fine-grained material and Si fine-grained material in the silicon shell cavity filling material, a carbon film with a thickness of no more than 1 nm is deposited on the surface of the target shale argon ion polishing sheet.

[0046] According to the specific implementation of the method for judging the ancient ocean water environment, preferably, the resolution of the obtained MAPS rock image data of fine-grained C and fine-grained Si materials is 1-10 nm (e.g., 4 nm).

[0047] The method for determining the paleooceanic water environment provided by this invention effectively combines the redox state of the deep-sea water in paleooceanic waters with the precipitation and dissolution conditions of calcite. It pioneers the use of petrological characteristics of radiolarian siliceous shale lamellar radiolarian siliceous cavity infill to determine the redox state of the deep-sea water in paleooceanic waters and the CSD, CLD, and CCD conditions of calcite. This method is of great significance for reconstructing paleooceanic environments and understanding life evolution, seawater chemical conditions, sediment distribution, carbon cycle, and the enrichment and preservation of organic matter. Attached Figure Description

[0048] Figure 1a This is a longitudinal section of radiolarian siliceous shale from Example 1.

[0049] Figure 1b The images show the characteristic spectra of the incomplete silicon shell and the silicon shell cavity filler in Example 1.

[0050] Figure 1c In Example 1 Figure 1b The surface scan of C element.

[0051] Figure 1d In Example 1 Figure 1bSurface scan of Si element.

[0052] Figure 1e In Example 1 Figure 1b Surface scan of Ca element.

[0053] Figure 1f In Example 1 Figure 1b Surface scan of Mg element.

[0054] Figure 1g In Example 1 Figure 1b Surface scan of Fe element.

[0055] Figure 1h In Example 1 Figure 1b The surface scan of the S-element.

[0056] Figure 1i In Example 1 Figure 1b A surface scan of the Al element.

[0057] Figure 1j In Example 1 Figure 1b The surface scan of element O.

[0058] Figure 1k The images show the spectra of the complete silicon shell and the silicon shell cavity filling material in Example 1.

[0059] Figure 11 The images show the spectra of the complete silicon shell and the silicon shell cavity filling material in Example 1.

[0060] Figure 1m This is a 4nm MAPS view of the complete silicon shell and the silicon shell cavity filler in Example 1.

[0061] Figure 1n This is a diagram of the silicon-shell cavity organosilicon particle composite in Example 1.

[0062] Figure 2a This is a longitudinal section of radiolarian siliceous shale from Example 2.

[0063] Figure 2b The images show the characteristic spectra of the incomplete silicon shell and the silicon shell cavity filler in Example 2.

[0064] Figure 2c In Example 2 Figure 2b The surface scan of C element.

[0065] Figure 2d In Example 2 Figure 2b Surface scan of Si element.

[0066] Figure 2e In Example 2 Figure 2b Surface scan of Ca element.

[0067] Figure 2f In Example 2 Figure 2b Surface scan of Mg element.

[0068] Figure 2g In Example 2 Figure 2b Surface scan of Fe element.

[0069] Figure 2h In Example 2 Figure 2b The surface scan of the S-element.

[0070] Figure 2i In Example 2 Figure 2b A surface scan of the Al element.

[0071] Figure 2j In Example 2 Figure 2b The surface scan of element O.

[0072] Figure 2k The images show the spectra of the complete silicon shell and the silicon shell cavity filling material in Example 2.

[0073] Figure 2l The images show the spectra of the complete silicon shell and the silicon shell cavity filling material in Example 2.

[0074] Figure 2m This is a 4nm MAPS view of the complete silicon shell and silicon shell cavity filler in Example 2.

[0075] Figure 2n This is a diagram of the silicon-shell cavity organosilicon particle composite in Example 2.

[0076] Figure 3a This is a longitudinal section of radiolarian siliceous shale from Example 3.

[0077] Figure 3b The images show the characteristic spectra of the incomplete silicon shell and the silicon shell cavity filler in Example 3.

[0078] Figure 3c In Example 3 Figure 3b The surface scan of C element.

[0079] Figure 3d In Example 3 Figure 3b Surface scan of Si element.

[0080] Figure 3e In Example 3 Figure 3b Surface scan of Ca element.

[0081] Figure 3f In Example 3 Figure 3b Surface scan of Mg element.

[0082] Figure 3gIn Example 3 Figure 3b Surface scan of Fe element.

[0083] Figure 3h In Example 3 Figure 3b The surface scan of the S-element.

[0084] Figure 3i In Example 3 Figure 3b A surface scan of the Al element.

[0085] Figure 3j In Example 3 Figure 3b The surface scan of element O.

[0086] Figure 3k The images show the spectra of the incomplete silicon shell and the silicon shell cavity filler in Example 3.

[0087] Figure 3l The images show the spectra of the complete silicon shell and the silicon shell cavity filling material in Example 3.

[0088] Figure 3m This is a 4nm MAPS view of the complete silicon shell and silicon shell cavity filling material in Example 3.

[0089] Figure 3n This is a diagram of the silicon-shell cavity organosilicon particle composite in Example 3. Detailed Implementation

[0090] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0091] MAPS stands for Modular Automated Processing System. MAPS technology divides the argon-polished surface of a sample into a series of regular grids, scans and images each grid, and stitches together the images of all grids to obtain a two-dimensional large field-of-view scan image data volume, which is the MAPS data volume.

[0092] The term "silicone shell" refers to the silicon shell of a radiolarian; a complete silicon shell refers to a silicon shell in which more than two-thirds of the silicon shell and more than two-thirds of the filling material in the silicon shell cavity are preserved; a damaged silicon shell refers to a silicon shell in which less than two-thirds of the silicon shell and less than two-thirds of the filling material in the silicon shell cavity are preserved.

[0093] Previous studies on paleooceanic environments have treated the redox state of deep-sea waters and the precipitation and dissolution conditions of calcite separately. Oxygen-rich, oxygen-depleted, and anoxic sulfidation conditions, as well as the CSD, CLD, and CCD of calcite within these waters, were studied in isolation. It was assumed that CSD, CLD, and CCD were simply a result of increased calcite solubility with increasing seawater depth and had no correlation with the redox state of the water. This is inconsistent with reality and hinders the reconstruction of paleooceanic environments.

[0094] Based on this, this invention focuses on developing a technical solution for assessing the paleooceanic environment by effectively combining the redox state of deep-sea waters with the precipitation and dissolution conditions of calcite. The inventors of this invention have concluded through research that:

[0095] For radiolarian siliceous shale laminae where the silica cavity filling material is a composite of calcite and organosilicon particles, and the calcite content in the silica cavity is less than 80%, if all the silica shells in the radiolarian siliceous shale laminae are fitted into a single complete silica shell, then the filling material of this complete silica cavity is a composite of calcite and organosilicon particles. The formation of this complete silica cavity filling material as a composite of calcite and organosilicon particles is due to: ① Calcite produced by the metabolism of calcium carbonate secreted by microorganisms in the oxygen-rich surface seawater completely filling the silica cavity of dead radiolarians (complete silica cavity); ② When this complete silica shell, filled with calcite, settles below the CSD (Central Surface Depression), the calcite begins to dissolve and forms calcite dissolution pores within the complete silica cavity; below the CSD is a dilute oxygen water environment, where microorganisms become active in the calcite dissolution pores of the complete silica cavity, inducing the precipitation of silica particles and forming a microbial silica particle composite filling the calcite dissolution pores of the complete silica cavity; ③ When the dissolved volume of calcite is greater than 20... When the calcite content is less than 80%, the intact silica shell filled with calcite and microbial silica particle complex settles into the dilute oxygen water environment below the CLD. The calcite dissolution rate increases and calcite dissolution pores are formed in the intact silica shell cavity. The calcite dissolution pores are then filled by the microbial silica particle complex. ④ This intact silica shell cavity has a calcite content of less than 80% and the calcite dissolution pores are filled by the microbial silica particle complex, indicating that the target radiolarian siliceous shale laminae are formed between the CLD and CCD in a dilute oxygen water environment. ⑤ During the burial and diagenesis process, the microbial silica particle complex is transformed into an organosilicon particle complex, and the calcite does not undergo significant changes.

[0096] For radiolarian siliceous shale laminae whose silica cavity filling consists of calcite, organosilicon particle complex, and pyrite, and where the calcite filling amount in the silica cavity is less than 80%, if all the silica shells in the radiolarian siliceous shale laminae are fitted into a complete silica shell, then the filling material of this complete silica cavity is calcite, organosilicon particle complex, and pyrite. The formation of this intact silica cavity, filled with calcite, organosilicon particle complex, and pyrite, is due to the following reasons: ① Calcite produced by the metabolism of calcium carbonate microorganisms secreted from the oxygen-rich surface seawater completely filled the silica cavity of the dead radiolarians (intact silica cavity); ② When this intact silica shell, filled with calcite, settles below the CSD (Central Surface Depression), the calcite begins to dissolve and forms calcite dissolution pores within the intact silica cavity; below the CSD is a dilute oxygen water environment, where microorganisms become active in the calcite dissolution pores of the intact silica cavity, inducing the precipitation of silica particles and forming microbial silica particle complexes filling the calcite dissolution pores of the intact silica cavity; ③ When the dissolved volume of calcite is greater than 20% (with less than 80% of calcite remaining), the intact silica shell filled with calcite and microbial silica particle complexes settles. In the low-oxygen water environment below the CLD, the dissolution rate of calcite increases and calcite dissolution pores are formed in the intact silica shell cavity. The calcite dissolution pores are then filled by microbial silica particle complexes. ④ The intact silica shell filled with calcite and organosilicon particle complexes settles into the anoxic sulfided water environment below the CLD. Due to the acidity of the anoxic sulfided water, the dissolution of calcite is accelerated, and the calcite dissolution pores are filled with pyrite, forming an intact silica shell cavity filled with calcite, organosilicon particle complexes and pyrite, with the calcite content less than 80%. This indicates that the radiolarian siliceous shale laminae formed between the CLD and CCD in an anoxic sulfided water environment. ⑤ During the burial and diagenesis process, the microbial silica particle complexes are transformed into organosilicon particle complexes, while the calcite and pyrite do not undergo significant changes.

[0097] For radiolarian siliceous shale laminae where the silica cavity filling consists of organosilicon particle complexes and pyrite, and the calcite filling volume in the silica cavity is less than 80%, all silica shells in the radiolarian siliceous shale laminae are fitted into a complete silica shell. The formation of this complete silica shell cavity filling with organosilicon particle complexes and pyrite is as follows: ① Calcite produced by the metabolism of calcium carbonate microorganisms secreted from the oxygen-rich surface seawater completely fills the silica shell cavity of dead radiolarians (complete silica shell cavity); ② When this complete silica shell, completely filled with calcite, settles below the CSD, the calcite begins to dissolve and forms calcite dissolution pores in the complete silica shell cavity; below the CSD is a dilute oxygen water environment, and microorganisms become active in the calcite dissolution pores of the complete silica shell cavity. Microorganisms induce the precipitation of silica particles, forming microbial silica particle complexes that fill the calcite dissolution pores of the complete silica shell cavity; ③ When the calcite dissolution volume is greater than 20% (the complete silica shell cavity filling volume is less than 80%), the complete silica shell cavity filling volume is formed by organosilicon particle complexes and pyrite filling volume. When less than 80% of the calcite remains, the intact silica shell filled with calcite and microbial silica particle complex settles into a dilute oxygen water environment below the CLD. The dissolution rate of calcite increases, forming calcite dissolution pores in the intact silica shell cavity, which are then filled by the microbial silica particle complex. ④ When the intact silica shell filled with calcite and organosilicon particle complex settles into an anoxic sulfided water environment below the CLD, the calcite dissolution accelerates due to the acidity of the anoxic sulfided water. The dissolution pores are filled with pyrite, forming an intact silica shell cavity filled with calcite, organosilicon particle complex, and pyrite. ⑤ When all the calcite dissolves and the cavity is filled with organosilicon particle complex and pyrite, it indicates that the intact silica shell has settled into an anoxic sulfided water environment below the CCD. ⑥ During burial and diagenesis, the microbial silica particle complex transforms into an organosilicon particle complex, while calcite and pyrite do not undergo significant changes.

[0098] Based on the above research findings, this invention proposes a novel method for assessing the environment of ancient oceanic waters. It pioneers the use of petrological characteristics of radiolarian siliceous shale lamellar radiolarian siliceous cavity-filling materials to determine the redox state of ancient deep-sea waters and the CSD, CLD, and CCD conditions of calcite. This method effectively combines the redox state of ancient deep-sea waters with the precipitation and dissolution conditions of calcite, which is of great significance for reconstructing ancient oceanic environments and understanding life evolution, seawater chemistry, sediment distribution, carbon cycle, and the enrichment and preservation of organic matter. This invention uses the percentages of calcite in the radiolarian silica cavity of radiolarians (100%, 80%, and 0%) as boundaries. A 100% calcite content in the radiolarian silica cavity represents a supersaturated calcium carbonate environment in marine water, and the location where calcite begins to dissolve is the CSD (Central Depression) of marine water. A 80% calcite content in the radiolarian silica cavity represents the CLD (Central Depression) of marine water, and a 0% calcite content in the radiolarian silica cavity represents the CCD (Central Depression) of marine water.

[0099] In one specific embodiment, the present invention provides a method for determining the paleooceanic water environment, the method comprising:

[0100] Step S1: Obtain core samples of the target shale reservoir in the work area; wherein, the target shale reservoir is radiolarian siliceous shale with lamellar formation;

[0101] Step S2: Based on the core samples of the target shale reservoir, determine the composition of the silica cavity filling material in the target shale reservoir and the amount of calcite filling the silica cavity;

[0102] Step S3: Based on the composition of the silica cavity filling material and the amount of calcite filling the silica cavity in the target shale reservoir, determine the paleooceanic water environment during the depositional period of the target shale reservoir in the work area; among which,

[0103] If the silica cavity filling material in the target shale reservoir is composed of a composite of calcite and organosilicon particles and the calcite filling amount in the silica cavity is less than 80%, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above the CSD; the upper part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between CSD and CLD; the lower part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between CLD and CCD.

[0104] If the silica cavity filling material in the target shale reservoir is composed of calcite, organosilicon particle complex and pyrite, and the filling amount of calcite in the silica cavity is less than 80%, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above CSD; the upper part of the deep water body is dilute oxygen (dissolved oxygen ≤ 2.0 ml / L) and located between CSD and CLD; the middle part of the deep water body is dilute oxygen (dissolved oxygen ≤ 2.0 ml / L) and located between CLD and CCD; and the lower part of the deep water body is anoxic (anaerobic) and sulfided and located between CLD and CCD.

[0105] If the silica cavity filling material in the target shale reservoir is composed of a complex of pyrite and organosilicon particles, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above the CSD; the upper part of the deep water is dilute (dissolved oxygen ≤ 2.0 ml / L) and located between the CSD and CLD; the middle part of the deep water is dilute (dissolved oxygen ≤ 2.0 ml / L) and located between the CLD and CCD; the lower part of the deep water is anoxic (anaerobic) and sulfided and located between the CLD and CCD; and the bottom of the deep water is anoxic (anaerobic) and sulfided and located below the CCD.

[0106] Further, in step S1, obtaining core samples from the target shale reservoir in the work area includes:

[0107] Obtain rock cores from the work area;

[0108] The longitudinal sections of the core samples from the work area were observed to determine the laminar texture of the radiolarian siliceous shale.

[0109] Radiolarian siliceous shale lamellar rock samples were taken as core samples of the target shale reservoir in the work area.

[0110] Furthermore, by observing the longitudinal section of the core samples from the work area, during the process of determining the radiolarian siliceous shale laminae, a layer of white spots (about 0.2 mm in diameter) that are present in the black shale (usually without any texture) was identified as the radiolarian siliceous shale laminae.

[0111] Further, in step S2, based on the core sample of the target shale reservoir, the composition of the silica cavity filling material in the target shale reservoir is determined, including:

[0112] Prepare thin sections of core samples from the target shale reservoir;

[0113] Electron probe microscopy was used to observe thin sections of cores from the target shale reservoir to identify the individual silica shells (including intact and incomplete silica shells) within the core sections.

[0114] Elemental surface scans of C, Si, Ca, Mg, Al, Fe, S, and O were performed on each silica shell in the target shale reservoir core thin section. Based on the C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scan results of each silica shell in the target shale reservoir core thin section, the composition of the silica shell cavity filling material in each silica shell in the target shale reservoir core thin section was preliminarily determined. Based on the preliminarily determined composition of the silica shell cavity filling material in each silica shell in the target shale reservoir core thin section, it was preliminarily determined whether the composition of the silica shell cavity filling material in the target shale reservoir core thin section was composed of calcite and fine-grained C and Si materials, or calcite, pyrite and fine-grained C and Si materials, or pyrite and fine-grained C and Si materials.

[0115] Argon-ion polished sections of the target shale reservoir were prepared based on core thin sections of the target shale reservoir. Based on the argon-ion polished sections of the target shale reservoir, MAPS rock image data volumes were obtained from the fine-grained C and Si materials in the silica cavity filling material. Based on the obtained MAPS rock image data volumes of the fine-grained C and Si materials, it was determined whether the fine-grained C and Si materials in the silica cavity filling material were organosilicon particle complexes.

[0116] If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of calcite and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of calcite and organosilicon particle complexes.

[0117] If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of calcite, pyrite, and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of calcite, organosilicon particle complexes, and pyrite.

[0118] If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of pyrite and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of pyrite and organosilicon particle complexes.

[0119] Furthermore, when the composition of the silica cavity filling material in each silica shell in the core thin section of the target shale reservoir is independently selected from one of the following: composed of calcite and fine-grained C and fine-grained Si, composed of calcite, or composed of fine-grained C and fine-grained Si, and there is at least one silica cavity filling material containing calcite, and at least one silica cavity filling material containing fine-grained C and fine-grained Si, then the silica cavity filling material in the target shale reservoir is composed of calcite and fine-grained C and fine-grained Si.

[0120] Furthermore, when the composition of the silica cavity filling material in each silica shell of the target shale reservoir core section is independently selected from one of the following: calcite and pyrite and fine-grained C and fine-grained Si, calcite and pyrite, calcite and fine-grained C and fine-grained Si, pyrite and fine-grained C and fine-grained Si, calcite, fine-grained C and fine-grained Si, or pyrite, and at least one silica cavity filling material contains calcite, at least one silica cavity filling material contains pyrite, or at least one silica cavity filling material contains fine-grained C and fine-grained Si, then the silica cavity filling material in the target shale reservoir is composed of calcite, pyrite and fine-grained C and fine-grained Si.

[0121] Furthermore, when the composition of the silica cavity filling material in each silica shell in the core thin section of the target shale reservoir is independently selected from one of the following: composed of pyrite and fine-grained C and fine-grained Si, composed of fine-grained C and fine-grained Si, or composed of pyrite, and there is at least one silica cavity filling material containing pyrite, and at least one silica cavity filling material containing fine-grained C and fine-grained Si, then the silica cavity filling material in the target shale reservoir is composed of pyrite and fine-grained C and fine-grained Si.

[0122] In elemental surface scan images, the transition from black, blue, green, and yellow to red represents a gradual increase in elemental content. Among the components of radiolarian siliceous shale, quartz has the highest Si and O content, calcite has the highest Ca content, and pyrite has the highest Fe and S content. Therefore, quartz, calcite, and pyrite can be identified first through elemental surface scans of Si, O, Ca, Fe, and S. Dolomite can then be identified through combined analysis of Ca, Mg, C, and O elements. Finally, the distribution areas of clay minerals can be identified through combined analysis of Fe, Mg, Si, and Al elements. The color degradation is caused by mutual shielding between fine-grained C and Si materials. Generally, if the surface scan results of C, Si, Ca, Mg, Al, Fe, S, and O elements in the silica shell cavity show that Ca element surface scan is red, then the silica shell cavity filling material is considered to contain calcite. If the surface scan results of C, Si, Ca, Mg, Al, Fe, S, and O elements in the silica shell show that Fe and S element surface scans are red or yellow, then the silica shell cavity filling material is considered to contain pyrite. If the surface scan results of C, Si, Ca, Mg, Al, Fe, S, and O elements in the silica shell show that C element surface scan is blue to green and Si element surface scan is green to red, then the silica shell cavity filling material is considered to contain fine C and fine Si particles.

[0123] In radiolarian siliceous shale laminae filled with calcite and organosilicon particle complexes, the incomplete silica shells are caused by the destruction of the complete silica shells during deep-sea settling. In addition to being filled with calcite and organosilicon particle complexes, silica shell cavities are commonly filled with calcite and / or organosilicon particle complexes. This is because the core thin section of the target shale reservoir cuts into different locations of the silica shell cavities filled with calcite and organosilicon particle complexes in the radiolarian siliceous shale laminae. When cutting through calcite, silica shell cavities filled with calcite are observed, and when cutting through organosilicon particle complexes, silica shell cavities filled with organosilicon particle complexes are observed.

[0124] In radiolarian siliceous shale laminae filled with calcite, organosilicon granules, and pyrite, the incomplete silica shell is caused by the destruction of the complete silica shell during the settling process in deep ocean waters. In addition to calcite, organosilicon granules, and pyrite, the silica shell cavities are commonly filled with calcite and pyrite, and / or calcite and organosilicon granules, and / or pyrite and organosilicon granules, and / or the silica shell cavities are filled with pyrite and organosilicon granules, and / or the silica shell cavities are completely filled with calcite, and / or the silica shell cavities are completely filled with organosilicon granules, and / or the silica shell cavities are completely filled with pyrite. This is due to the fact that the core thin section of the target shale reservoir cut into different locations of the siliceous cavities filled with calcite, organosilicon complexes, and pyrite in the radiolarian siliceous shale laminae. When cutting through calcite and pyrite, siliceous cavities filled with calcite and pyrite were observed; when cutting through calcite and organosilicon complexes, siliceous cavities filled with calcite and organosilicon complexes were observed; when cutting through pyrite and organosilicon complexes, siliceous cavities filled with pyrite and organosilicon complexes were observed; when cutting through calcite, siliceous cavities were completely filled with calcite; when cutting through organosilicon complexes, siliceous cavities were completely filled with organosilicon complexes; and when cutting through pyrite, siliceous cavities were completely filled with pyrite.

[0125] In radiolarian siliceous shale laminae filled with pyrite and organosilicon particle complexes, the incomplete silica shells are caused by the destruction of intact silica shells during deep-sea settling. Besides being filled with organosilicon particle complexes and pyrite, silica shell cavities are commonly found to be fully filled with organosilicon particle complexes and / or fully filled with pyrite. This is because the core section of the target shale reservoir cut through different locations of silica shell cavities filled with organosilicon particle complexes and pyrite within the radiolarian siliceous shale laminae. When the section cut through the organosilicon particle complex, fully filled silica shell cavities were observed; when the section cut through the pyrite, fully filled silica shell cavities were observed.

[0126] Further, in step S2, based on the core sample of the target shale reservoir, the amount of calcite filling the silica cavities in the target shale reservoir is determined, including:

[0127] Prepare thin sections of core samples from the target shale reservoir;

[0128] Electron probe microscopy was used to observe thin sections of cores from the target shale reservoir to identify the individual silica shells (including intact and incomplete silica shells) within the core sections.

[0129] C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scans were performed on each silica shell in the core thin section of the target shale reservoir. Based on the C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scan results of each silica shell in the core thin section of the target shale reservoir, the calcite in the silica shell cavity filling material of each silica shell in the core thin section of the target shale reservoir was preliminarily determined.

[0130] Based on the surface scanning results of C, Si, Ca, Mg, Al, Fe, S and O elements in each silica shell of the target shale reservoir core thin section, the area of ​​the silica shell cavity and the area of ​​the calcite filling material in the cavity of each silica shell in the target shale reservoir core thin section are determined.

[0131] Based on the area of ​​the silica cavity of each silica shell in the core thin section of the target shale reservoir and the area of ​​calcite in the cavity filling material, the total area of ​​the silica cavity of each silica shell in the core thin section of the target shale reservoir and the total area of ​​calcite in the cavity filling material of each silica shell are determined.

[0132] Based on the total area of ​​the silica cavities in each silica shell and the total area of ​​calcite in the cavity filling material of each silica shell in the core thin section of the target shale reservoir, the filling amount of calcite in the silica cavities of the target shale reservoir is determined; wherein, the filling amount of calcite in the silica cavities = the total area of ​​calcite in the cavity filling material of each silica shell ÷ the total area of ​​the silica cavities of each silica shell.

[0133] Furthermore, the core sections of the target shale reservoir are 2.5-7 cm long (e.g., 5 cm), 2.5-5 cm wide (e.g., 2.5 cm), and 30-40 μm thick (e.g., 35 μm).

[0134] Furthermore, before observing the target shale reservoir core thin section under an electron probe microscope, a platinum film is coated on the surface of the target shale reservoir core thin section; wherein the thickness of the platinum film may be, but is not limited to, 5-10 nm.

[0135] Furthermore, the top and bottom surfaces of the target shale reservoir core section are parallel to the top and bottom surfaces of the target shale reservoir core sample in its underground state.

[0136] Furthermore, during the observation of the target shale reservoir core thin section under an electron probe microscope, the top and bottom surfaces of the target shale reservoir core thin section were kept at the top and bottom surfaces of the field of view, respectively.

[0137] Furthermore, the argon-ion polished sheet of the target shale reservoir has a length of 0.8-2 cm (e.g., 1 cm), a width of 0.8-2 cm (e.g., 1 cm), and a thickness of 0.3-0.8 cm (e.g., 0.5 cm).

[0138] Furthermore, the top and bottom surfaces of the argon-ion polished sheet of the target shale reservoir are parallel to the top and bottom surfaces of the core sample of the target shale reservoir in its underground state.

[0139] Furthermore, during the acquisition of MAPS rock image data of fine-grained C and Si materials in the silica shell cavity filling material, the top and bottom surfaces of the argon ion polishing sheet of the target shale reservoir are kept at the top and bottom surfaces of the field of view, respectively.

[0140] Furthermore, before acquiring MAPS rock image data of the fine C and fine Si materials in the silicon shell cavity filling material, a carbon film with a thickness of no more than 1 nm is deposited on the surface of the target shale argon ion polishing sheet.

[0141] Furthermore, the resolution of the obtained MAPS rock image data volumes of fine-grained C and fine-grained Si materials is 1-10 nm (e.g., 4 nm resolution).

[0142] Further, based on the obtained MAPS rock image data of fine-grained C and Si materials, the step of determining whether the fine-grained C and Si materials in the silica cavity filling are organosilicon particle complexes includes:

[0143] Use an image editor (such as the offline image editor ATLAS) TM The BROWSER-BASEDVIEWER tool was used to analyze the acquired MAPS rock image data volumes of fine-grained C and Si materials on a computer.

[0144] Example 1:

[0145] This embodiment provides a method for determining the paleooceanic water environment during the depositional period of the siliceous shale lamellars of region A.

[0146] The method specifically includes:

[0147] 1. Obtain core samples from the target shale reservoir.

[0148] In this embodiment, observation of the longitudinal section of the core from area A revealed a 2.5 mm thick layer of white spots (approximately 0.2 mm in diameter) distributed throughout the black shale in area A. Figure 1a As shown in the figure, the laminae are A radiolarian siliceous shale laminae; rock samples of A radiolarian siliceous shale laminae were taken as core samples of the target shale reservoir in the work area.

[0149] 2. Based on core samples from the target shale reservoir, determine the composition of the silica cavity filling material and the amount of calcite filling the silica cavity; including:

[0150] 1) Prepare thin sections of the target shale reservoir core sample with a length of 5 cm, a width of 2.5 cm, and a thickness of 35 μm; wherein the top and bottom surfaces of the thin sections are parallel to the top and bottom surfaces of the target shale reservoir core sample in its underground state;

[0151] 2) A 5nm thick platinum film is deposited on the surface of the target shale reservoir core thin section. The top and bottom surfaces of the target shale reservoir core thin section are kept at the top and bottom of the field of view, respectively. The target shale reservoir core thin section is observed under an electron probe microscope to obtain the electron probe spectrum image of the target shale reservoir core thin section, thereby determining each silica shell (including complete silica shells and incomplete silica shells) in the target shale reservoir core thin section.

[0152] 3) Perform C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scans on each silica shell in the target shale reservoir core thin section; based on the C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scan results for each silica shell in the target shale reservoir core thin section, preliminarily determine the composition of the silica shell cavity filling material in each silica shell in the target shale reservoir core thin section; based on the preliminarily determined composition of the silica shell cavity filling material in each silica shell in the target shale reservoir core thin section, preliminarily determine whether the composition of the silica shell cavity filling material in the target shale reservoir core thin section is composed of calcite and fine-grained C and Si materials, or composed of calcite, pyrite and fine-grained C and Si materials, or composed of pyrite and fine-grained C and Si materials;

[0153] When the composition of the silica cavity filling of each silica shell in the core thin section of the target shale reservoir is independently selected from one of the following: calcite and fine-grained C and fine-grained Si, calcite, or fine-grained C and fine-grained Si, and at least one silica shell cavity filling contains calcite, or at least one silica shell cavity filling contains fine-grained C and fine-grained Si, then the silica cavity filling in the target shale reservoir is composed of calcite and fine-grained C and fine-grained Si.

[0154] When the composition of the silica cavity filling of each silica shell in the core thin section of the target shale reservoir is independently selected from one of the following: calcite and pyrite and fine-grained C and Si, calcite and pyrite, calcite and fine-grained C and Si, pyrite and fine-grained C and Si, calcite, fine-grained C and Si, or pyrite, and at least one silica shell cavity filling contains calcite, at least one silica shell cavity filling contains pyrite, or at least one silica shell cavity filling contains fine-grained C and Si, then the silica cavity filling in the target shale reservoir is composed of calcite, pyrite, fine-grained C, and fine-grained Si.

[0155] When the composition of the silica cavity filling of each silica shell in the core thin section of the target shale reservoir is independently selected from one of the following: pyrite and fine-grained C and fine-grained Si, fine-grained C and fine-grained Si, or pyrite, and there is at least one silica cavity filling containing pyrite, or at least one silica cavity filling containing fine-grained C and fine-grained Si, then the silica cavity filling in the target shale reservoir is composed of pyrite and fine-grained C and fine-grained Si.

[0156] 4) Based on the target shale reservoir core thin section, prepare argon-ion polished discs with a length of 1 cm, a width of 1 cm, and a thickness of 0.5 cm. The top and bottom surfaces of the argon-ion polished discs are parallel to the top and bottom surfaces of the target shale reservoir core sample in its underground state. After depositing a carbon film no more than 1 nm thick on the surface of the argon-ion polished discs, use the argon-ion polished discs, with the top and bottom surfaces of the argon-ion polished discs kept at the top and bottom of the field of view, respectively, to acquire 4 nm MAPS rock image data volumes of C fine-grained materials and Si fine-grained materials in the silica cavity filling material. Use an image editor (e.g., the offline image editor ATLAS). TM The BROWSER-BASEDVIEWER analyzes the 4nm MAPS rock image data of the acquired C fine-grained material and Si fine-grained material on a computer to determine whether the C fine-grained material and Si fine-grained material in the silica cavity filling material are organosilicon particle complexes.

[0157] If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of calcite and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of calcite and organosilicon particle complexes.

[0158] If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of calcite, pyrite, and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of calcite, organosilicon particle complexes, and pyrite.

[0159] If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of pyrite and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of pyrite and organosilicon particle complexes.

[0160] 5) Based on the surface scan results of C, Si, Ca, Mg, Al, Fe, S, and O elements in each silica shell of the target shale reservoir core thin section, preliminarily determine the filling materials in the silica shell cavity of each silica shell in the target shale reservoir core thin section; based on the surface scan results of C, Si, Ca, Mg, Al, Fe, S, and O elements in each silica shell of the target shale reservoir core thin section, determine the area of ​​the silica shell cavity of each silica shell in the target shale reservoir core thin section and the area of ​​calcite in the cavity filling material; based on the total area of ​​the silica shell cavity of each silica shell in the target shale reservoir core thin section and the total area of ​​each type of filling material in the cavity filling material of each silica shell, determine the filling amount of each type of filling material in the silica shell cavity of the target shale reservoir; wherein, the filling amount of each type of filling material in the silica shell cavity = the total area of ​​that type of filling material in the cavity filling material of each silica shell ÷ the total area of ​​the silica shell cavity of each silica shell.

[0161] In this embodiment, the electron probe spectroscopy image of the core thin section of the target shale reservoir (such as...) Figure 1b , Figure 1k , Figure 11 As shown in the figure, and based on the elemental surface scan results for C, Si, Ca, Mg, Fe, S, Al, and O, the silica cavity filling material in the target shale reservoir is composed of calcite and fine-grained C and Si materials (as shown in the figure). Figure 1c , Figure 1d , Figure 1e , Figure 1f , Figure 1g , Figure 1h , Figure 1i , Figure 1j (As shown).

[0162] In this embodiment, the C-particle material and Si-particle material filling the silicon cavity are organosilicon particle composites (such as...). Figure 1m , Figure 1n (As shown).

[0163] In this embodiment, the calcite filling amount in the silica shell cavity is 61%, and the content of organosilicon particle composite is 39%.

[0164] 3. Based on the composition of the silica cavity filling material and the amount of calcite filling the silica cavity in the target shale reservoir, determine the paleooceanic water environment during the depositional period of the target shale reservoir in the work area; among which,

[0165] If the silica cavity filling material in the target shale reservoir is composed of a composite of calcite and organosilicon particles and the calcite filling amount in the silica cavity is less than 80%, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above the CSD; the upper part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between CSD and CLD; the lower part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between CLD and CCD.

[0166] If the silica cavity filling material in the target shale reservoir is composed of calcite, organosilicon particle complex and pyrite, and the filling amount of calcite in the silica cavity is less than 80%, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above CSD; the upper part of the deep water body is dilute oxygen (dissolved oxygen ≤ 2.0 ml / L) and located between CSD and CLD; the middle part of the deep water body is dilute oxygen (dissolved oxygen ≤ 2.0 ml / L) and located between CLD and CCD; and the lower part of the deep water body is anoxic (anaerobic) and sulfided and located between CLD and CCD.

[0167] If the silica cavity filling material in the target shale reservoir is composed of a complex of pyrite and organosilicon particles, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above the CSD; the upper part of the deep water is dilute (dissolved oxygen ≤ 2.0 ml / L) and located between the CSD and CLD; the middle part of the deep water is dilute (dissolved oxygen ≤ 2.0 ml / L) and located between the CLD and CCD; the lower part of the deep water is anoxic (anaerobic) and sulfided and located between the CLD and CCD; and the bottom of the deep water is anoxic (anaerobic) and sulfided and located below the CCD.

[0168] In this embodiment, the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich (dissolved oxygen content > 2.0 ml / L) and located above the CSD; the upper part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CSD and CLD; and the lower part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CLD and CCD.

[0169] Example 2

[0170] This embodiment provides a method for determining the paleooceanic water environment during the depositional period of the B radiolarians in the siliceous shale laminae of region B.

[0171] Its only difference from Example 1 is:

[0172] In step 1, observation of the longitudinal section of the core from area B revealed a 2.9 mm thick layer of laminae covered with white spots approximately 0.2 mm in diameter (as shown in the image). Figure 2a As shown in the figure, the laminae are B radiolarian siliceous shale laminae; rock samples of the B radiolarian siliceous shale laminae were taken as core samples of the target shale reservoir in the work area.

[0173] In step 2, in this embodiment, the electron probe spectroscopy image of the target shale reservoir core thin section (e.g., Figure 2b , Figure 2k , Figure 2l As shown in the figure, and based on the elemental surface scan results for C, Si, Ca, Mg, Fe, S, Al, and O, the silica cavity filling material in the target shale reservoir is composed of calcite, pyrite, and fine-grained C and Si materials (as shown in the figure). Figure 2c , Figure 2d , Figure 2e , Figure 2f , Figure 2g , Figure 2h , Figure 2i , Figure 2j (As shown). The C fine-particle material and Si fine-particle material filling the silicon shell cavity are organosilicon particle composites (such as...). Figure 2m , Figure 2n (As shown). The calcite content in the silica-shell cavity was 16%, the organosilicon particle content was 57%, and the pyrite content was 23%.

[0174] In step 3, in this embodiment, the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is determined as follows: the surface water of the paleooceanic deep water body is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above the CSD; the upper part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between the CSD and CLD; the middle part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between the CLD and CCD; and the lower part of the deep water body is anoxic (anaerobic) and sulfided and located between the CLD and CCD.

[0175] Example 3

[0176] This embodiment provides a method for determining the paleooceanic water environment during the lamellar deposition period of the C-region radiolarians in siliceous shale.

[0177] Its only difference from Example 1 is:

[0178] In step 1, observation of the longitudinal section of the core from area C revealed a 3.3 mm thick layer of laminae covered with white spots approximately 0.2 mm in diameter (as shown in the image). Figure 3aAs shown in the figure, the laminae are C radiolarian siliceous shale laminae; rock samples of C radiolarian siliceous shale laminae were taken as core samples of the target shale reservoir in the work area.

[0179] In step 2, in this embodiment, the electron probe spectroscopy image of the target shale reservoir core thin section (e.g., Figure 3b , Figure 3k , Figure 3l As shown in the figure, and based on the elemental surface scan results for C, Si, Ca, Mg, Fe, S, Al, and O, the silica cavity filling material in the target shale reservoir is composed of pyrite and fine-grained C and Si materials (as shown in the figure). Figure 3c , Figure 3d , Figure 3e , Figure 3f , Figure 3g , Figure 3h , Figure 3i , Figure 3j (As shown). The C fine-particle material and Si fine-particle material filling the silicon shell cavity are organosilicon particle composites (such as...). Figure 3m , Figure 3n (As shown). The content of organosilicon particle complex in the silica shell cavity is 74%, and the content of pyrite is 26%.

[0180] In step 3, in this embodiment, the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is determined as follows: the surface water of the paleooceanic deep water body is oxygen-rich (dissolved oxygen > 2.0 ml / L) and located above the CSD; the upper part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between the CSD and CLD; the middle part of the deep water body is oxygen-depleted (dissolved oxygen ≤ 2.0 ml / L) and located between the CLD and CCD; the lower part of the deep water body is anoxic (anoxic) and sulfided and located between the CLD and CCD; and the bottom of the deep water body is anoxic (anoxic) and sulfided and located below the CCD.

[0181] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining the environment of a paleoocean, the method comprising: Core samples were obtained from the target shale reservoir in the work area; wherein the target shale reservoir is radiolarian siliceous shale with lamellar formations. Based on core samples from the target shale reservoir, the composition of the silica cavity filling material and the amount of calcite filling the silica cavity were determined. Based on the composition of the silica cavity filling material and the amount of calcite filling the silica cavity in the target shale reservoir, the paleooceanic water environment during the depositional period of the target shale reservoir in the work area was determined; among which... If the silica cavity filling material in the target shale reservoir is composed of a composite of calcite and organosilicon particles and the amount of calcite filling the silica cavity is less than 80%, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich and located above the CSD, the upper part of the deep water body is oxygen-poor and located between the CSD and CLD, and the lower part of the deep water body is oxygen-poor and located between the CLD and CCD. If the silica cavity filling material in the target shale reservoir is composed of calcite, organosilicon particle complex and pyrite and the amount of calcite filling the silica cavity is less than 80%, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich and located above CSD, the upper part of the deep water body is deoxygenated and located between CSD and CLD, the middle part of the deep water body is deoxygenated and located between CLD and CCD, and the lower part of the deep water body is anoxic and sulfided and located between CLD and CCD. If the silica cavity filling material in the target shale reservoir is composed of a complex of pyrite and organosilicon particles, then the paleooceanic water environment during the deposition period of the target shale reservoir in the work area is as follows: the surface water of the paleooceanic deep water body is oxygen-rich and located above the CSD; the upper part of the deep water body is oxygen-depleted and located between the CSD and CLD; the middle part of the deep water body is oxygen-depleted and located between the CLD and CCD; the lower part of the deep water body is anoxic and sulfided and located between the CLD and CCD; and the bottom of the deep water body is anoxic and sulfided and located below the CCD.

2. The method according to claim 1, wherein, Based on core samples from the target shale reservoir, the composition of the silica cavity filling material in the target shale reservoir was determined to include: Prepare thin sections of core samples from the target shale reservoir; Electron probe microscopy was used to observe thin sections of cores from the target shale reservoir to identify the individual silica shells within the core sections. Elemental surface scans of C, Si, Ca, Mg, Al, Fe, S, and O were performed on each silica shell in the target shale reservoir core thin section. Based on the C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scan results of each silica shell in the target shale reservoir core thin section, the composition of the silica shell cavity filling material in each silica shell in the target shale reservoir core thin section was preliminarily determined. Based on the preliminarily determined composition of the silica shell cavity filling material in each silica shell in the target shale reservoir core thin section, it was preliminarily determined whether the composition of the silica shell cavity filling material in the target shale reservoir core thin section was composed of calcite and fine-grained C and Si materials, or calcite, pyrite and fine-grained C and Si materials, or pyrite and fine-grained C and Si materials. Argon-ion polished sections of the target shale reservoir were prepared based on core thin sections of the target shale reservoir. Based on the argon-ion polished sections of the target shale reservoir, MAPS rock image data volumes were obtained from the fine-grained C and Si materials in the silica cavity filling material. Based on the obtained MAPS rock image data volumes of the fine-grained C and Si materials, it was determined whether the fine-grained C and Si materials in the silica cavity filling material were organosilicon particle complexes. If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of calcite and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of calcite and organosilicon particle complexes. If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of calcite, pyrite, and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of calcite, organosilicon particle complexes, and pyrite. If it is preliminarily determined that the composition of the silica cavity filling material in the core thin section of the target shale reservoir is composed of pyrite and fine-grained C and Si materials, and the fine-grained C and Si materials in the silica cavity filling material are organosilicon particle complexes, then the composition of the silica cavity filling material in the target shale reservoir is composed of pyrite and organosilicon particle complexes. Preferably, the resolution of the obtained MAPS rock image data volumes of fine-grained C and fine-grained Si materials is 1-10 nm.

3. The method according to claim 2, wherein, When the composition of the silica cavity filling material in each silica shell of a target shale reservoir core section is independently selected from one of the following: composed of calcite and fine-grained C and Si materials, composed of calcite, or composed of fine-grained C and Si materials, and at least one silica cavity filling material contains calcite, or at least one silica cavity filling material contains fine-grained C and Si materials, then the silica cavity filling material in the target shale reservoir is composed of calcite and fine-grained C and Si materials.

4. The method according to claim 2, wherein, When the composition of the silica cavity filling material in each silica shell of the target shale reservoir core thin section is independently selected from one of the following: calcite and pyrite and fine-grained C and Si materials; calcite and pyrite; calcite and fine-grained C and Si materials; pyrite and fine-grained C and Si materials; calcite; fine-grained C and Si materials; or pyrite, and at least one silica cavity filling material contains calcite, at least one silica cavity filling material contains pyrite, or at least one silica cavity filling material contains fine-grained C and Si materials, then the silica cavity filling material in the target shale reservoir is composed of calcite, pyrite, fine-grained C materials, and fine-grained Si materials.

5. The method according to claim 2, wherein, When the composition of the silica cavity filling material in each silica shell in the core thin section of the target shale reservoir is independently selected from one of the following: composed of pyrite and fine-grained C and fine-grained Si, composed of fine-grained C and fine-grained Si, or composed of pyrite, and there is at least one silica cavity filling material containing pyrite, and at least one silica cavity filling material containing fine-grained C and fine-grained Si, then the silica cavity filling material in the target shale reservoir is composed of pyrite and fine-grained C and fine-grained Si.

6. The method according to claim 2, wherein, The length, width, and thickness of the argon ion polishing sheet for the target shale reservoir are 0.8-2 cm.

7. The method according to claim 2, wherein, Before acquiring MAPS rock image data of fine C and fine Si materials in the silicon shell cavity filling material, a carbon film with a thickness of no more than 1 nm is deposited on the surface of the target shale argon ion polishing sheet.

8. The method according to claim 1, wherein, Based on core samples from the target shale reservoir, the amount of calcite filling the silica cavities in the target shale reservoir was determined to include: Prepare thin sections of core samples from the target shale reservoir; Electron probe microscopy was used to observe thin sections of cores from the target shale reservoir to identify the individual silica shells within the core sections. C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scans were performed on each silica shell in the core thin section of the target shale reservoir. Based on the C, Si, Ca, Mg, Al, Fe, S, and O elemental surface scan results of each silica shell in the core thin section of the target shale reservoir, the calcite in the silica shell cavity filling material of each silica shell in the core thin section of the target shale reservoir was preliminarily determined. Based on the surface scanning results of C, Si, Ca, Mg, Al, Fe, S and O elements in each silica shell of the target shale reservoir core thin section, the area of ​​the silica shell cavity and the area of ​​the calcite filling material in the cavity of each silica shell in the target shale reservoir core thin section are determined. Based on the area of ​​the silica cavity of each silica shell in the core thin section of the target shale reservoir and the area of ​​calcite in the cavity filling material, the total area of ​​the silica cavity of each silica shell in the core thin section of the target shale reservoir and the total area of ​​calcite in the cavity filling material of each silica shell are determined. Based on the total area of ​​the silica cavities in each silica shell and the total area of ​​calcite in the cavity filling material of each silica shell in the core thin section of the target shale reservoir, the filling amount of calcite in the silica cavities of the target shale reservoir is determined; wherein, the filling amount of calcite in the silica cavities = the total area of ​​calcite in the cavity filling material of each silica shell ÷ the total area of ​​the silica cavities of each silica shell.

9. The method according to claim 2 or 8, wherein, The core sections of the target shale reservoir are 2.5-7 cm long, 2.5-5 cm wide, and 30-40 μm thick.

10. The method according to claim 2 or 8, wherein, Before observing the core thin sections of the target shale reservoir under an electron probe microscope, a platinum film is coated on the surface of the core thin sections of the target shale reservoir.

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