A method for judging ancient ocean water body environment

Abstract

The application provides a method for judging ancient marine water body environment. The method comprises the following steps: obtaining a target shale reservoir core sample in a work area; wherein the target shale reservoir is radiolarian siliceous shale lamina; determining the composition of the shell cavity filling and the filling amount of calcite in the shell cavity in the target shale reservoir based on the target shale reservoir core sample; and determining the ancient marine water body environment during the deposition period of the target shale reservoir in the work area according to the composition of the shell cavity filling and the filling amount of calcite in the shell cavity in the target shale reservoir. The method for judging ancient marine water body environment can effectively combine the oxidation-reduction state of the ancient marine deep water body and the precipitation and dissolution conditions of calcite, so as to better promote the reconstruction of the ancient marine environment.

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] In view of the previous research results, the redox state of the ancient ocean deep water body and the precipitation and dissolution conditions of calcite are respectively studied, the oxygen-rich, oxygen-poor, anoxic and sulfidation of the water body and the CSD, CLD and CCD of the calcite in the water body are fragmented, and the CSD, CLD and CCD are defaulted as the result of the increase of the solubility of calcite with the increase of the depth of seawater, and there is no correlation with the redox state of the water body. This does not conform to the actual situation, and seriously affects the reconstruction of the ancient ocean environment.

[0006] In summary, there is still a need to study a new technical scheme for judging the ancient ocean water body environment, effectively combining the redox state of the ancient ocean deep water body and the precipitation and dissolution conditions of calcite, so as to better realize the reconstruction of the ancient ocean environment. SUMMARY

[0007] The purpose of the present application is to provide a technical scheme for judging the ancient ocean water body environment, which can effectively combine the redox state of the ancient ocean deep water body and the precipitation and dissolution conditions of calcite, so as to better promote the reconstruction of the ancient ocean environment.

[0008] In order to achieve the above-mentioned purpose, the present application provides a method for judging the ancient ocean water body environment, which comprises:

[0009] Obtaining a target shale reservoir core sample in a work area; wherein the target shale reservoir is radiolarian siliceous shale laminae;

[0010] Based on the target shale reservoir core sample, determining the composition of the shell cavity filler and the filling amount of calcite in the shell cavity in the target shale reservoir;

[0011] According to the composition of the shell cavity filler and the filling amount of calcite in the shell cavity in the target shale reservoir, determining the ancient ocean water body environment during the deposition period of the target shale reservoir in the work area; wherein,

[0012] If the shell cavity filler in the target shale reservoir is composed of calcite and organic silicon particle complex and the filling amount of calcite in the shell cavity is less than 80%, the ancient ocean water body environment during the deposition period of the target shale reservoir in the work area is that the surface water body of the ancient ocean 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 the 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 the CCD;

[0013] If the siliceous shell cavity filling in the target shale reservoir is composed of calcite, organic silicon particle complex and pyrite, and the filling amount of calcite in the siliceous shell cavity is less than 80%, the paleo-ocean water body environment during the deposition period of the target shale reservoir in the work area is: the surface water body of the paleo-ocean 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 the CLD, the middle part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CLD and the CCD, and the lower part of the deep water body is anoxic (oxygen-free) sulfidation and located between the CLD and the CCD.

[0014] If the siliceous shell cavity filling in the target shale reservoir is composed of pyrite and organic silicon particle complex, the paleo-ocean water body environment during the deposition period of the target shale reservoir in the work area is: the surface water body of the paleo-ocean 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 the CLD, the middle part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CLD and the CCD, and the lower part of the deep water body is anoxic (oxygen-free) sulfidation and located between the CLD and the CCD, and the bottom of the deep water body is anoxic (oxygen-free) sulfidation and located below the CCD.

[0015] The method for judging the paleo-ocean water body environment provided by the application opens up a new way for judging the redox state of the paleo-ocean deep water body and the CSD, CLD and CCD conditions of calcite by the petrological characteristics of the siliceous shell cavity filling of the radiolarite lamina, effectively combines the redox state of the paleo-ocean deep water body and the precipitation and dissolution conditions of calcite, and has important significance for reconstructing the paleo-ocean environment and understanding the life evolution, seawater chemical conditions, sediment distribution, carbon cycle, enrichment and preservation of organic matter.

[0016] According to the specific implementation mode of the method for judging the paleo-ocean water body environment, preferably, the obtaining of the target shale reservoir core sample in the work area comprises:

[0017] Obtaining a core in the work area;

[0018] Observing the longitudinal section of the core in the work area to determine the radiolarite lamina;

[0019] Taking the rock sample of the radiolarite lamina as the target shale reservoir core sample in the work area.

[0020] According to the specific implementation mode of the method for judging the paleo-ocean water body environment, preferably, based on the target shale reservoir core sample, the composition of the siliceous shell cavity filling in the target shale reservoir comprises:

[0021] Preparation of a target shale reservoir core slice based on the target shale reservoir core sample;

[0022] electron probe microscope, to determine each siliceous shell (including complete siliceous shell and incomplete siliceous shell) in the target shale reservoir core slice;

[0023] performing C, Si, Ca, Mg, Al, Fe, S, O element area scanning on each siliceous shell in the target shale reservoir core slice; based on the C, Si, Ca, Mg, Al, Fe, S, O element area scanning results of each siliceous shell in the target shale reservoir core slice, preliminarily determining the composition of the siliceous shell cavity filling of each siliceous shell in the target shale reservoir core slice; based on the preliminarily determined composition of the siliceous shell cavity filling of each siliceous shell in the target shale reservoir core slice, preliminarily determining whether the composition of the siliceous shell cavity filling in the target shale reservoir core slice is composed of calcite and C fine-grained material, Si fine-grained material, or composed of calcite, pyrite and C fine-grained material, Si fine-grained material, or composed of pyrite and C fine-grained material, Si fine-grained material;

[0024] preparing a target shale reservoir argon ion polishing slice based on the target shale reservoir core slice; based on the target shale reservoir argon ion polishing slice, performing MAPS rock image data body acquisition on the C fine-grained material and Si fine-grained material in the siliceous shell cavity filling; based on the acquired MAPS rock image data body of the C fine-grained material and Si fine-grained material, determining whether the C fine-grained material and Si fine-grained material in the siliceous shell cavity filling are organic silicon particle complexes;

[0025] if it is preliminarily determined that the composition of the siliceous shell cavity filling in the target shale reservoir core slice is composed of calcite and C fine-grained material, Si fine-grained material, and the C fine-grained material and Si fine-grained material in the siliceous shell cavity filling are organic silicon particle complexes, then the composition of the siliceous shell cavity filling in the target shale reservoir is composed of calcite and organic silicon particle complexes;

[0026] if it is preliminarily determined that the composition of the siliceous shell cavity filling in the target shale reservoir core slice is composed of calcite, pyrite and C fine-grained material, Si fine-grained material, and the C fine-grained material and Si fine-grained material in the siliceous shell cavity filling are organic silicon particle complexes, then the composition of the siliceous shell cavity filling in the target shale reservoir is composed of calcite, organic silicon particle complexes and pyrite;

[0027] if it is preliminarily determined that the composition of the siliceous shell cavity filling in the target shale reservoir core slice is composed of pyrite and C fine-grained material, Si fine-grained material, and the C fine-grained material and Si fine-grained material in the siliceous shell cavity filling are organic silicon particle complexes, then the composition of the siliceous shell cavity filling in the target shale reservoir is composed of pyrite and organic silicon particle complexes;

[0028] More preferably, when the composition of the siliceous shell cavity fillings of each siliceous shell in the core sample of the target shale reservoir is independently selected from one of calcite and C-fines and Si-fines, calcite, C-fines and Si-fines, and C-fines and Si-fines, and the siliceous shell cavity fillings of at least one siliceous shell contain calcite, the siliceous shell cavity fillings of at least one siliceous shell contain C-fines and Si-fines, and the siliceous shell cavity fillings of at least one siliceous shell contain C-fines, the composition of the siliceous shell cavity fillings in the target shale reservoir is calcite and C-fines and Si-fines.

[0029] More preferably, when the composition of the siliceous shell cavity fillings of each siliceous shell in the core sample of the target shale reservoir is independently selected from one of calcite and pyrite and C-fines and Si-fines, calcite and pyrite, calcite and C-fines and Si-fines, pyrite and C-fines and Si-fines, calcite, C-fines and Si-fines, and pyrite, and the siliceous shell cavity fillings of at least one siliceous shell contain calcite, the siliceous shell cavity fillings of at least one siliceous shell contain pyrite, and the siliceous shell cavity fillings of at least one siliceous shell contain C-fines and Si-fines, the composition of the siliceous shell cavity fillings in the target shale reservoir is calcite, pyrite and C-fines and Si-fines.

[0030] More preferably, when the composition of the siliceous shell cavity fillings of each siliceous shell in the core sample of the target shale reservoir is independently selected from one of pyrite and C-fines and Si-fines, C-fines and Si-fines, and pyrite, and the siliceous shell cavity fillings of at least one siliceous shell contain pyrite, and the siliceous shell cavity fillings of at least one siliceous shell contain C-fines and Si-fines, the composition of the siliceous shell cavity fillings in the target shale reservoir is pyrite and C-fines and Si-fines.

[0031] According to the method for judging the water body environment of a paleo-ocean, preferably, based on the core sample of the target shale reservoir, the filling amount of calcite in the siliceous shell cavity in the target shale reservoir is determined by:

[0032] A core sample of the target shale reservoir is prepared based on the core sample of the target shale reservoir;

[0033] The core sample of the target shale reservoir is observed under an electron probe microscope to determine each siliceous shell (including complete siliceous shells and incomplete siliceous shells) in the core sample of the target shale reservoir;

[0034] performing C, Si, Ca, Mg, Al, Fe, S, O element area scanning on each siliceous shell in the target shale reservoir core slice; based on the C, Si, Ca, Mg, Al, Fe, S, O element area scanning results of each siliceous shell in the target shale reservoir core slice, the calcite in the siliceous shell cavity filling of each siliceous shell in the target shale reservoir core slice is preliminarily determined;

[0035] based on the C, Si, Ca, Mg, Al, Fe, S, O element area scanning results of each siliceous shell in the target shale reservoir core slice, the area of the siliceous shell cavity of each siliceous shell in the target shale reservoir core slice and the area of the calcite in the cavity filling thereof are determined;

[0036] based on the area of the siliceous shell cavity of each siliceous shell in the target shale reservoir core slice and the area of the calcite in the cavity filling thereof, the total area of the siliceous shell cavity of each siliceous shell and the total area of the calcite in the cavity filling of each siliceous shell in the target shale reservoir core slice are determined;

[0037] based on the total area of the siliceous shell cavity of each siliceous shell and the total area of the calcite in the cavity filling of each siliceous shell in the target shale reservoir core slice, the filling amount of the calcite in the siliceous shell cavity in the target shale reservoir is determined; wherein the filling amount of the calcite in the siliceous shell cavity = the total area of the calcite in the cavity filling of each siliceous shell ÷ the total area of the siliceous shell cavity of each siliceous shell.

[0038] According to the specific embodiment of the method for judging the ancient marine water body environment, preferably, the length of the target shale reservoir core slice is 2.5-7 cm (for example, 5 cm), the width is 2.5-5 cm (for example, 2.5 cm), and the thickness is 30-40 μm (for example, 35 μm).

[0039] According to the specific embodiment of the method for judging the ancient marine water body environment, preferably, before the target shale reservoir core slice is observed under an electron probe microscope, a platinum-gold film is plated on the surface of the target shale reservoir core slice; wherein the thickness of the platinum-gold film can be but is not limited to 5 nm.

[0040] According to the specific embodiment of the method for judging the ancient marine water body environment, preferably, the top surface and the bottom surface of the target shale reservoir core slice are parallel to the top surface and the bottom surface of the target shale reservoir core sample in the underground state.

[0041] According to the specific embodiment of the method for judging the ancient marine water body environment, preferably, during the observation of the target shale reservoir core slice under an electron probe microscope, the top surface and the bottom surface of the target shale reservoir core slice are respectively kept at the top surface and the bottom surface of the field of view.

[0042] According to the specific embodiment of the method for judging the ancient marine water body environment, preferably, the length of the argon ion polished slice of the target shale reservoir is 0.8-2 cm (for example, 1 cm), the width is 0.8-2 cm (for example, 1 cm), and the thickness is 0.3-0.8 cm (for example, 0.5 cm).

[0043] According to the specific embodiment of the method for judging the ancient marine water body environment, preferably, the top surface and the bottom surface of the argon ion polished slice of the target shale reservoir are parallel to the top surface and the bottom surface of the core sample of the target shale reservoir in the underground state.

[0044] According to the specific embodiment of the method for judging the ancient marine water body environment, preferably, during the MAPS rock image data body acquisition process of the C fine-grained material and the Si fine-grained material in the shell cavity filling, the top surface and the bottom surface of the argon ion polished slice of the target shale reservoir are respectively kept at the top surface and the bottom surface of the field of view.

[0045] According to the specific embodiment of the method for judging the ancient marine water body environment, preferably, before the MAPS rock image data body acquisition of the C fine-grained material and the Si fine-grained material in the shell cavity filling, a carbon film with a thickness of not more than 1 nm is plated on the surface of the target shale argon ion polished slice.

[0046] According to the specific embodiment of the method for judging the ancient marine water body environment, preferably, the resolution of the obtained MAPS rock image data body of the C fine-grained material and the Si fine-grained material is 1-10 nm resolution (for example, 4 nm resolution).

[0047] The method for judging the ancient marine water body environment provided by the application effectively combines the redox state of the ancient marine deep water body and the precipitation and dissolution conditions of calcite, and opens up a new way for judging the redox state of the ancient marine deep water body and the CSD, CLD and CCD conditions of calcite through the petrological characteristics of the shell cavity filling of radiolarite siliceous shale lamina of radiolarians, which is of great significance for reconstructing the ancient marine environment, understanding the life evolution, seawater chemical conditions, sediment distribution, carbon cycle and enrichment and preservation of organic matter. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1a It is a radiolarite siliceous shale lamina graph of the core longitudinal section in Example 1.

[0049] Figure 1b It is a characteristic spectrum graph of the incomplete shell and the shell cavity filling in Example 1.

[0050] Figure 1c It is a C element surface scanning graph of Figure 1b in Example 1.

[0051] Figure 1d It is a C element surface scanning graph of Figure 1bSi elemental map.

[0052] Figure 1e Mg elemental map of the complete siliceous shell and shell lumen fillings in Example 1. Figure 1b

[0053] Figure 1f Mg elemental map of the complete siliceous shell and shell lumen fillings in Example 1. Figure 1b

[0054] Figure 1g Fe elemental map of the complete siliceous shell and shell lumen fillings in Example 1. Figure 1b

[0055] Figure 1h S elemental map of the complete siliceous shell and shell lumen fillings in Example 1. Figure 1b

[0056] Figure 1i Al elemental map of the complete siliceous shell and shell lumen fillings in Example 1. Figure 1b

[0057] Figure 1j O elemental map of the complete siliceous shell and shell lumen fillings in Example 1. Figure 1b

[0058] Figure 1k Spectrum of the complete siliceous shell and shell lumen fillings in Example 1.

[0059] Figure 1l Spectrum of the complete siliceous shell and shell lumen fillings in Example 1.

[0060] Figure 1m 4 nm MAPS overview of the complete siliceous shell and shell lumen fillings in Example 1.

[0061] Figure 1n Silicon particle composite in the shell lumen of Example 1.

[0062] Figure 2a Radiolarian siliceous shale laminae in the longitudinal section of the core in Example 2.

[0063] Figure 2b Characteristic spectrum of the broken siliceous shell and shell lumen fillings in Example 2.

[0064] Figure 2c C elemental map of the complete siliceous shell and shell lumen fillings in Example 2. Figure 2b

[0065] Si elemental map of the complete siliceous shell and shell lumen fillings in Example 2. Figure 2d Figure 2b Ca elemental map of the complete siliceous shell and shell lumen fillings in Example 2.

[0066] Figure 2e Figure 2b Ca elemental map of the complete siliceous shell and shell lumen fillings in Example 2. ​​​​​​​​

[0067] Figure 2f Mg element mapping of the complete nassellid test and test cavity fill of Example 2. Figure 2b

[0068] Figure 2g Fe element mapping of the complete nassellid test and test cavity fill of Example 2. Figure 2b

[0069] Figure 2h S element mapping of the complete nassellid test and test cavity fill of Example 2. Figure 2b

[0070] Figure 2i Al element mapping of the complete nassellid test and test cavity fill of Example 2. Figure 2b

[0071] Figure 2j O element mapping of the complete nassellid test and test cavity fill of Example 2. Figure 2b

[0072] Figure 2k Spectrum of the complete nassellid test and test cavity fill of Example 2.

[0073] Figure 2l Spectrum of the complete nassellid test and test cavity fill of Example 2.

[0074] Figure 2m 4 nm MAPS overview of the complete nassellid test and test cavity fill of Example 2.

[0075] Figure 2n Composite of the complete nassellid test and test cavity fill of Example 2.

[0076] Figure 3a Radiolarian siliceous shale laminae of the core longitudinal section of Example 3.

[0077] Figure 3b Characteristic spectrum of the broken nassellid test and test cavity fill of Example 3.

[0078] Figure 3c C element mapping of the complete nassellid test and test cavity fill of Example 3. Figure 3b

[0079] Si element mapping of the complete nassellid test and test cavity fill of Example 3. Figure 3d Figure 3b Ca element mapping of the complete nassellid test and test cavity fill of Example 3.

[0080] Figure 3e Figure 3b Mg element mapping of the complete nassellid test and test cavity fill of Example 3.

[0081] Figure 3f Mg element mapping of the complete nassellid test and test cavity fill of Example 3. Figure 3b

[0082] Figure 3g ​​​​​​​​Fe element face scan map of Example 3. Figure 3b

[0083] S element face scan map of Example 3. Figure 3h Figure 3b Al element face scan map of Example 3.

[0084] Figure 3i Figure 3b O element face scan map of Example 3.

[0085] Figure 3j O element face scan map of Example 3. Figure 3b

[0086] Spectrum of broken siliceous shell and siliceous shell cavity filling of Example 3. Figure 3k

[0087] Spectrum of broken siliceous shell and siliceous shell cavity filling of Example 3. Figure 3l

[0088] 4nm MAPS full view of complete siliceous shell and siliceous shell cavity filling of Example 3. Figure 3m

[0089] Siliceous shell cavity organic silica particle complex of Example 3. Figure 3n DETAILED DESCRIPTION

[0090] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the embodiments of the present application are further described in detail below with reference to the drawings. Herein, the illustrative embodiments of the present application and the descriptions thereof are used to explain the present application, but are not intended to limit the present application.

[0091] MAPS: Modular Automated Processing System. The MAPS technology is to divide the argon ion polished surface of a sample into a series of regular grids, to scan and image each grid, and to splice the images of all the grids to obtain a two-dimensional large-view scanning image data body, i.e. a MAPS data body.

[0092] Siliceous shell refers to radiolarian siliceous shell; complete siliceous shell refers to a siliceous shell of which more than two-thirds is preserved and of which more than two-thirds of the siliceous shell cavity filling is preserved; broken siliceous shell refers to a siliceous shell of which less than two-thirds is preserved and of which less than two-thirds of the siliceous shell cavity filling is preserved.

[0093] ​​​In the past, the redox state of the deep water body of the ancient ocean and the precipitation and dissolution conditions of calcite are studied respectively, the oxygen-rich, oxygen-poor, oxygen-deficient and sulfidation of the water body and the CSD, CLD and CCD of the calcite in the water body are fragmented, and the CSD, CLD and CCD are assumed to be the result of the increase of the solubility of the calcite with the increase of the depth of the seawater, and there is no correlation with the redox state of the water body. This does not conform to the actual situation, and affects the reconstruction of the ancient ocean environment.

[0094] Based on this, the present application is dedicated to studying a technical scheme for judging the water body environment of the ancient ocean which can effectively combine the redox state of the deep water body of the ancient ocean and the precipitation and dissolution conditions of calcite. The present inventors have found that:

[0095] For the radiolarian siliceous shale lamina in which the filling material of the siliceous shell cavity is composed of calcite and organic siliceous particle complex and the filling amount of calcite in the siliceous shell cavity is less than 80%, all the siliceous shells in the radiolarian siliceous shale lamina are fitted into a complete siliceous shell, and the filling material of the complete siliceous shell cavity is calcite and organic siliceous particle complex. The cause of the filling material of the complete siliceous shell cavity being calcite and organic siliceous particle complex is: ① the calcite produced by the metabolism of calcium carbonate microorganisms secreted by the surface oxygen-rich seawater fully fills the dead radiolarian shell cavity (complete siliceous shell cavity); ② when the complete siliceous shell filled with the calcite in the cavity is settled below the CSD, the calcite begins to dissolve and forms calcite dissolution pores in the complete siliceous shell cavity; the environment below the CSD is an oxygen-poor water body, and microorganisms are active in the calcite dissolution pores of the complete siliceous shell cavity, microorganism-induced siliceous particles are precipitated, and microorganism-siliceous particle complex is formed to fill the calcite dissolution pores of the complete siliceous shell cavity; ③ when the dissolution volume of the calcite is greater than 20% (the remaining calcite is less than 80%), the complete siliceous shell filled with the calcite and the microorganism-siliceous particle complex in the cavity is settled in the oxygen-poor water body below the CLD, the dissolution rate of the calcite increases, and calcite dissolution pores are formed in the complete siliceous shell cavity, which are immediately filled with microorganism-siliceous particle complex; ④ the content of calcite in the complete siliceous shell cavity is less than 80%, and the calcite dissolution pores are filled with microorganism-siliceous particle complex, indicating that the target radiolarian siliceous shale lamina is formed between the CLD and the CCD and in an oxygen-poor water body; ⑤ during the burial diagenetic process, the microorganism-siliceous particle complex is transformed into organic siliceous particle complex, and the calcite does not change significantly.

[0096] For the radiolarite shale lamina in which the siliceous shell cavity is filled with calcite, organic-siliceous particle complex and pyrite and the filling amount of calcite in the siliceous shell cavity is less than 80%, all the siliceous shells in the radiolarite shale lamina are fitted into a complete siliceous shell, and the complete siliceous shell cavity is filled with calcite, organic-siliceous particle complex and pyrite. The cause of the complete siliceous shell cavity being filled with calcite, organic-siliceous particle complex and pyrite is: ① the calcite produced by the metabolism of calcium carbonate secreting microorganisms in the surface oxygen-rich seawater completely fills the siliceous shell cavity (complete siliceous shell cavity) of the dead radiolarian; ② when the complete siliceous shell completely filled with calcite sinks below the CSD, the calcite begins to dissolve and form calcite dissolution pores in the complete siliceous shell cavity; the environment below the CSD is a dilute oxygen water body, and microorganisms are active in the calcite dissolution pores in the complete siliceous shell cavity, microorganisms induce siliceous particles to precipitate, forming a microbial-siliceous particle complex filling the calcite dissolution pores in the complete siliceous shell cavity; ③ when the dissolution volume of calcite is greater than 20% (the remaining calcite is less than 80%), the complete siliceous shell filled with calcite and microbial-siliceous particle complex sinks to the anoxic sulfidic water body environment below the CLD, the dissolution rate of calcite increases and calcite dissolution pores are formed in the complete siliceous shell cavity, which are immediately filled with microbial-siliceous particle complex; ④ when the complete siliceous shell filled with calcite and organic-siliceous particle complex sinks to the anoxic sulfidic water body environment below the CLD, due to the acidic nature of the anoxic sulfidic water body, the dissolution of calcite is accelerated, the calcite dissolution pores are filled with pyrite, forming a complete siliceous shell cavity filled with calcite, organic-siliceous particle complex and pyrite, and the content of calcite is less than 80%, indicating that the target radiolarite shale lamina is formed between the CLD and the CCD and in an anoxic sulfidic water body environment; ⑤ during the burial diagenetic process, the microbial-siliceous particle complex is transformed into an organic-siliceous particle complex, and the calcite and pyrite do not change significantly.

[0097] For radiolarite shale lamina with the siliceous shell cavity filling of organic-silica particle complex and pyrite and the filling amount of calcite in the siliceous shell cavity less than 80%, fitting all the siliceous shells in the radiolarite shale lamina into a complete siliceous shell, and the filling of the complete siliceous shell cavity is the genesis of the organic-silica particle complex and pyrite: ①The surface oxygen-rich seawater secretes calcite produced by microbial metabolism to completely fill the siliceous shell cavity (complete siliceous shell cavity) of the dead radiolarian; ②When the complete siliceous shell cavity completely filled with calcite sinks below the CSD, the calcite begins to dissolve and form calcite dissolution pores in the complete siliceous shell cavity; below the CSD is a dilute oxygen water environment, and microorganisms are active in the calcite dissolution pores of the complete siliceous shell cavity, microorganism-induced siliceous particles are precipitated to form a microbial-silica particle complex filling the calcite dissolution pores of the complete siliceous shell cavity; ③When the dissolution volume of calcite is greater than 20% (the remaining calcite is less than 80%), the complete siliceous shell cavity filled with calcite and microbial-silica particle complex sinks to the dilute oxygen water environment below the CLD, the dissolution rate of calcite increases and calcite dissolution pores are formed in the complete siliceous shell cavity, which are immediately filled with microbial-silica particle complex; ④When the complete siliceous shell cavity filled with calcite and organic-silica particle complex sinks to the anoxic sulfidic water environment below the CLD, due to the acidic nature of the anoxic sulfidic water environment, the dissolution of calcite is accelerated, the dissolution pores are filled with pyrite, and the complete siliceous shell cavity filled with calcite, organic-silica particle complex and pyrite is formed; ⑤When the calcite is completely dissolved and the cavity is filled with organic-silica particle complex and pyrite, it indicates that the complete siliceous shell sinks to the anoxic sulfidic water environment below the CCD; ⑥During the burial diagenetic process, the microbial-silica particle complex is transformed into organic-silica particle complex, and the calcite and pyrite do not change significantly.

[0098] Based on the above research conclusion, the present application proposes a brand-new method for judging the ancient marine water environment, which opens up a new way for judging the redox state of the ancient marine deep water and the CSD, CLD and CCD conditions of calcite through the petrological characteristics of the filling of the siliceous shell cavity of the radiolarite shale lamina, effectively combines the redox state of the ancient marine deep water and the precipitation and dissolution conditions of calcite, and has important significance for reconstructing the ancient marine environment and understanding the life evolution, seawater chemical conditions, sediment distribution, carbon cycle, enrichment and preservation of organic matter. The present application takes 100%, 80% and 0% of the volume percentage of calcite in the siliceous shell cavity of the radiolarite shale lamina as the boundary, 100% of the volume of calcite in the siliceous shell cavity as the calcite supersaturated environment of the marine water, the position where the calcite begins to dissolve as the CSD of the marine water, 80% of the volume of calcite in the siliceous shell cavity as the CLD of the marine water, and 0% of the volume of calcite in the siliceous shell cavity as the CCD of the marine water.

[0099] In a specific embodiment, the present application provides a method for judging the ancient marine water environment, which comprises:

[0100] Step S1: obtaining a core sample of a target shale reservoir in a work area; wherein the target shale reservoir is radiolarian siliceous shale lamina;

[0101] Step S2: determining the composition of the shell cavity filling and the filling amount of calcite in the shell cavity in the target shale reservoir based on the core sample of the target shale reservoir;

[0102] Step S3: determining the paleo-ocean water body environment during the deposition period of the target shale reservoir in the work area according to the composition of the shell cavity filling and the filling amount of calcite in the shell cavity in the target shale reservoir; wherein,

[0103] If the shell cavity filling in the target shale reservoir is composed of calcite and organic-silicon particle complex and the filling amount of calcite in the shell cavity is less than 80%, the paleo-ocean water body environment during the deposition period of the target shale reservoir in the work area is that the surface water body of the paleo-ocean 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 the 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 the CCD.

[0104] If the shell cavity filling in the target shale reservoir is composed of calcite, organic-silicon particle complex and pyrite and the filling amount of calcite in the shell cavity is less than 80%, the paleo-ocean water body environment during the deposition period of the target shale reservoir in the work area is that the surface water body of the paleo-ocean 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 the CLD, the middle part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CLD and the CCD, and the lower part of the deep water body is anoxic (oxygen-free) sulfidation and located between the CLD and the CCD.

[0105] If the shell cavity filling in the target shale reservoir is composed of pyrite and organic-silicon particle complex, the paleo-ocean water body environment during the deposition period of the target shale reservoir in the work area is that the surface water body of the paleo-ocean 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 the CLD, the middle part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CLD and the CCD, the lower part of the deep water body is anoxic (oxygen-free) sulfidation and located between the CLD and the CCD, and the bottom of the deep water body is anoxic (oxygen-free) sulfidation and located below the CCD.

[0106] Further, in step S1, the obtaining of the core sample of the target shale reservoir in the work area comprises:

[0107] obtaining a core in the work area;

[0108] observing the longitudinal section of the work area core to determine the radiolarite shale lamina;

[0109] taking the radiolarite shale lamina rock sample as the work area target shale reservoir core sample;

[0110] Further, in the process of observing the longitudinal section of the work area core to determine the radiolarite shale lamina, a layer of white spots (about 0.2 mm in diameter) of pen tip size existing in black shale (usually showing no any fabric) on the longitudinal section of the work area core is determined as the radiolarite shale lamina.

[0111] Further, in step S2, determining the composition of the siliceous shell cavity filling in the target shale reservoir based on the target shale reservoir core sample includes:

[0112] Preparation of the target shale reservoir core slice based on the target shale reservoir core sample;

[0113] Observing the target shale reservoir core slice under the electron probe microscope to determine each siliceous shell (including complete siliceous shell and incomplete siliceous shell) in the target shale reservoir core slice;

[0114] Performing C, Si, Ca, Mg, Al, Fe, S, and O element area scanning on each siliceous shell in the target shale reservoir core slice; based on the C, Si, Ca, Mg, Al, Fe, S, and O element area scanning results of each siliceous shell in the target shale reservoir core slice, preliminarily determining the composition of the siliceous shell cavity filling of each siliceous shell in the target shale reservoir core slice; based on the preliminarily determined composition of the siliceous shell cavity filling of each siliceous shell in the target shale reservoir core slice, preliminarily determining whether the composition of the siliceous shell cavity filling in the target shale reservoir core slice is composed of calcite and C fine-grained material, Si fine-grained material, or composed of calcite, pyrite and C fine-grained material, Si fine-grained material, or composed of pyrite and C fine-grained material, Si fine-grained material;

[0115] Preparation of the target shale reservoir argon ion polishing slice based on the target shale reservoir core slice; based on the target shale reservoir argon ion polishing slice, obtaining the MAPS rock image data volume of the C fine-grained material and Si fine-grained material in the siliceous shell cavity filling; based on the obtained MAPS rock image data volume of the C fine-grained material and Si fine-grained material, determining whether the C fine-grained material and Si fine-grained material in the siliceous shell cavity filling are organic silicon particle complexes;

[0116] If it is preliminarily determined that the composition of the siliceous shell cavity fillings in the core slice of the target shale reservoir is composed of calcite and C fine-grained matter and Si fine-grained matter, and the C fine-grained matter and Si fine-grained matter in the siliceous shell cavity fillings are organic silicon particle complexes, then the composition of the siliceous shell cavity fillings in the target shale reservoir is composed of calcite and organic silicon particle complexes;

[0117] If it is preliminarily determined that the composition of the siliceous shell cavity fillings in the core slice of the target shale reservoir is composed of calcite, pyrite and C fine-grained matter and Si fine-grained matter, and the C fine-grained matter and Si fine-grained matter in the siliceous shell cavity fillings are organic silicon particle complexes, then the composition of the siliceous shell cavity fillings in the target shale reservoir is composed of calcite, organic silicon particle complexes and pyrite;

[0118] If it is preliminarily determined that the composition of the siliceous shell cavity fillings in the core slice of the target shale reservoir is composed of pyrite and C fine-grained matter and Si fine-grained matter, and the C fine-grained matter and Si fine-grained matter in the siliceous shell cavity fillings are organic silicon particle complexes, then the composition of the siliceous shell cavity fillings in the target shale reservoir is composed of pyrite and organic silicon particle complexes;

[0119] Further, when the composition of the siliceous shell cavity fillings of each siliceous shell in the core slice of the target shale reservoir is independently selected from one of calcite and C fine-grained matter and Si fine-grained matter, calcite, C fine-grained matter and Si fine-grained matter, and there is at least one siliceous shell cavity filling containing calcite, at least one siliceous shell cavity filling containing C fine-grained matter and Si fine-grained matter, then the composition of the siliceous shell cavity fillings in the target shale reservoir is composed of calcite and C fine-grained matter and Si fine-grained matter;

[0120] Further, when the composition of the siliceous shell cavity fillings of each siliceous shell in the core slice of the target shale reservoir is independently selected from one of calcite and C fine-grained matter and Si fine-grained matter, calcite, C fine-grained matter and Si fine-grained matter, and there is at least one siliceous shell cavity filling containing calcite, at least one siliceous shell cavity filling containing C fine-grained matter and Si fine-grained matter, then the composition of the siliceous shell cavity fillings in the target shale reservoir is composed of calcite and C fine-grained matter and Si fine-grained matter;

[0121] Further, when the composition of each framboidal cavity fillings in the target shale reservoir core slice is independently selected from one of pyrite and C-fines and Si-fines, consists of C-fines and Si-fines, consists of pyrite, and there is at least one framboidal cavity fillings containing pyrite, at least one framboidal cavity fillings containing C-fines and Si-fines, the framboidal cavity fillings in the target shale reservoir consists of pyrite and C-fines, Si-fines;

[0122] In the element face scanning image, the transition from black, blue, green, yellow to red represents the gradual increase of the content of the element. In each component of radiolarite, the Si and O content of quartz is the highest, the Ca content of calcite is the highest, and the Fe and S content of pyrite is the highest. Therefore, quartz, calcite and pyrite can be distinguished first by the face scanning results of Si, O, Ca, Fe and S elements, then dolomite can be distinguished by the combination analysis of Ca, Mg, C and O elements, and then the distribution area of clay minerals can be distinguished by the combination of Fe, Mg, Si and Al elements. Because C-fines and Si-fines shield each other, the color is degraded. Generally, when the face scanning results of C, Si, Ca, Mg, Al, Fe, S and O elements of the framboid cavity exist the feature that the Ca element face scanning is red, it is considered that the framboid cavity fillings contain calcite; when the face scanning results of C, Si, Ca, Mg, Al, Fe, S and O elements of the framboid exist the feature that the Fe and S element face scanning results are red or yellow, it is considered that the framboid cavity fillings contain pyrite; when the face scanning results of C, Si, Ca, Mg, Al, Fe, S and O elements of the framboid exist the feature that the C element face scanning is blue to green and the Si element face scanning is green to red, it is considered that the framboid cavity fillings contain C-fines and Si-fines.

[0123] In the radiolarite lamina where the framboid cavity fillings consist of calcite and organic-silica particle complex, the broken framboid is caused by the damage of the complete framboid during the sinking process in the deep water of the ocean. In addition to filling calcite and organic-silica particle complex, the framboid cavity is often fully filled with calcite and / or fully filled with organic-silica particle complex, which is caused by the different positions of the framboid cavity filled with calcite and organic-silica particle complex in the radiolarite lamina of the target shale reservoir core slice. When the calcite is cut, the framboid cavity is observed to be fully filled with calcite, and when the organic-silica particle complex is cut, the framboid cavity is observed to be fully filled with organic-silica particle complex.

[0124] In the radiolarite lamina in which the filling of the siliceous shell cavity is composed of calcite, organic-silica particle complex and pyrite, the broken siliceous shell is caused by the damage of the intact siliceous shell during the sinking process in the deep water of the ocean; besides the filling of the organic-silica particle complex and the pyrite, the siliceous shell cavity is commonly filled with the organic-silica particle complex, and / or the siliceous shell cavity is commonly filled with the pyrite. This is caused by the different positions of the siliceous shell cavity filled with the organic-silica particle complex and the pyrite in the radiolarite lamina of the target shale reservoir core slice, when the organic-silica particle complex is cut, the siliceous shell cavity filled with the organic-silica particle complex is observed, when the pyrite is cut, the siliceous shell cavity filled with the pyrite is observed.

[0125] In the radiolarite lamina in which the filling of the siliceous shell cavity is composed of calcite, organic-silica particle complex and pyrite, the broken siliceous shell is caused by the damage of the intact siliceous shell during the sinking process in the deep water of the ocean; besides the filling of the organic-silica particle complex and the pyrite, the siliceous shell cavity is commonly filled with the organic-silica particle complex, and / or the siliceous shell cavity is commonly filled with the pyrite. This is caused by the different positions of the siliceous shell cavity filled with the organic-silica particle complex and the pyrite in the radiolarite lamina of the target shale reservoir core slice, when the organic-silica particle complex is cut, the siliceous shell cavity filled with the organic-silica particle complex is observed, when the pyrite is cut, the siliceous shell cavity filled with the pyrite is observed.

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

[0127] Based on the target shale reservoir core sample, a target shale reservoir core slice is prepared;

[0128] The target shale reservoir core slice is observed under an electron probe microscope, and each siliceous shell (including intact siliceous shell and broken siliceous shell) in the target shale reservoir core slice is determined;

[0129] performing C, Si, Ca, Mg, Al, Fe, S, O element area scanning on each siliceous shell in the target shale reservoir core slice; based on the C, Si, Ca, Mg, Al, Fe, S, O element area scanning results of each siliceous shell in the target shale reservoir core slice, preliminarily determining calcite in the siliceous shell cavity filler of each siliceous shell in the target shale reservoir core slice;

[0130] based on the C, Si, Ca, Mg, Al, Fe, S, O element area scanning results of each siliceous shell in the target shale reservoir core slice, determining the area of the siliceous shell cavity of each siliceous shell in the target shale reservoir core slice and the area of calcite in the cavity filler thereof;

[0131] based on the area of the siliceous shell cavity of each siliceous shell in the target shale reservoir core slice and the area of calcite in the cavity filler thereof, determining the total area of the siliceous shell cavity of each siliceous shell and the total area of calcite in the cavity filler of each siliceous shell in the target shale reservoir core slice;

[0132] based on the total area of the siliceous shell cavity of each siliceous shell and the total area of calcite in the cavity filler of each siliceous shell in the target shale reservoir core slice, determining the filling amount of calcite in the siliceous shell cavity in the target shale reservoir; wherein the filling amount of calcite in the siliceous shell cavity = the total area of calcite in the cavity filler of each siliceous shell ÷ the total area of the siliceous shell cavity of each siliceous shell.

[0133] Further, the length of the target shale reservoir core slice is 2.5-7 cm (for example, 5 cm), the width is 2.5-5 cm (for example, 2.5 cm), and the thickness is 30-40 μm (for example, 35 μm).

[0134] Further, before the target shale reservoir core slice is observed under an electron probe microscope, a platinum-gold film is plated on the surface of the target shale reservoir core slice; wherein the thickness of the platinum-gold film can be but is not limited to 5-10 nm.

[0135] Further, the top surface and the bottom surface of the target shale reservoir core slice are parallel to the top surface and the bottom surface of the target shale reservoir core sample in the underground state.

[0136] Further, during the observation of the target shale reservoir core slice under an electron probe microscope, the top surface and the bottom surface of the target shale reservoir core slice are respectively kept at the top surface and the bottom surface of the field of view.

[0137] Further, the length of the target shale reservoir argon ion polished slice is 0.8-2 cm (for example, 1 cm), the width is 0.8-2 cm (for example, 1 cm), and the thickness is 0.3-0.8 cm (for example, 0.5 cm).

[0138] Further, the top surface and the bottom surface of the argon-ion polished slice of the target shale reservoir are parallel to the top surface and the bottom surface of the core sample of the target shale reservoir in the underground state.

[0139] Further, during the MAPS rock image data body acquisition process of the C fine-grained material and the Si fine-grained material in the shell cavity filler, the top surface and the bottom surface of the argon-ion polished slice of the target shale reservoir are respectively kept at the top surface and the bottom surface of the field of view.

[0140] Further, before the MAPS rock image data body acquisition of the C fine-grained material and the Si fine-grained material in the shell cavity filler, a carbon film with a thickness of not more than 1 nm is plated on the surface of the target shale argon-ion polished slice.

[0141] Further, the resolution of the acquired MAPS rock image data body of the C fine-grained material and the Si fine-grained material is 1-10 nm resolution (for example, 4 nm resolution).

[0142] Further, based on the acquired MAPS rock image data body of the C fine-grained material and the Si fine-grained material, the step of determining whether the C fine-grained material and the Si fine-grained material in the shell cavity filler are organic silicon particle complexes comprises:

[0143] An image editor (for example, an offline image editor ATLAS TM BROWSER-BASED VIEWER) is used to analyze the acquired MAPS rock image data body of the C fine-grained material and the Si fine-grained material on a computer.

[0144] Embodiment 1:

[0145] The embodiment provides a method for judging the paleo-ocean water environment during the deposition period of the A radiolarian siliceous shale lamina.

[0146] The method specifically comprises:

[0147] 1. Obtain a target shale reservoir core sample.

[0148] In this embodiment, the A core longitudinal section is observed, and it is found that there is a lamina with a thickness of 2.5 mm and white spots with a diameter of about 0.2 mm in the A black shale (as shown in FIG. 1), which is an A radiolarian siliceous shale lamina; the A radiolarian siliceous shale lamina rock sample is taken as the target shale reservoir core sample of the work area. Figure 1a

[0149] 2. Based on the target shale reservoir core sample, determine the composition of the shell cavity filler in the target shale reservoir and the filling amount of calcite in the shell cavity; comprising:

[0150] ​1) based on the target shale reservoir core sample, a target shale reservoir core slice with a length of 5 cm, a width of 2.5 cm and a thickness of 35 μm is prepared; wherein the top surface and the bottom surface of the target shale reservoir core slice are parallel to the top surface and the bottom surface of the target shale reservoir core sample in the underground state;

[0151] 2) a platinum-gold film with a thickness of 5 nm is plated on the surface of the target shale reservoir core slice, the top surface and the bottom surface of the target shale reservoir core slice are respectively kept at the top surface and the bottom surface of the field of view, the target shale reservoir core slice is observed under an electron probe microscope, and an electron probe spectrum image of the target shale reservoir core slice is obtained, and then each siliceous shell (including complete siliceous shell and incomplete siliceous shell) in the target shale reservoir core slice is determined;

[0152] 3) C, Si, Ca, Mg, Al, Fe, S and O element area scanning is performed on each siliceous shell in the target shale reservoir core slice; based on the C, Si, Ca, Mg, Al, Fe, S and O element area scanning results of each siliceous shell in the target shale reservoir core slice, the composition of the siliceous shell cavity filler of each siliceous shell in the target shale reservoir core slice is preliminarily determined; based on the composition of the siliceous shell cavity filler of each siliceous shell in the target shale reservoir core slice preliminarily determined, it is preliminarily determined whether the composition of the siliceous shell cavity filler in the target shale reservoir core slice is composed of calcite and C fine-grained material and Si fine-grained material, or composed of calcite, pyrite and C fine-grained material and Si fine-grained material, or composed of pyrite and C fine-grained material and Si fine-grained material;

[0153] When the composition of the siliceous shell cavity filler of each siliceous shell in the target shale reservoir core slice is independently selected from one of calcite and C fine-grained material and Si fine-grained material, calcite, C fine-grained material and Si fine-grained material, and at least one siliceous shell cavity filler contains calcite and at least one siliceous shell cavity filler contains C fine-grained material and Si fine-grained material, the siliceous shell cavity filler in the target shale reservoir is composed of calcite and C fine-grained material and Si fine-grained material;

[0154] When the composition of the shell cavity fillings of each of the siliceous shells in the target shale reservoir core slice is independently selected from one of the group consisting of calcite and pyrite and C-fines and Si-fines, C-fines and Si-fines, and pyrite, and the shell cavity fillings of at least one of the siliceous shells contain calcite, the shell cavity fillings of at least one of the siliceous shells contain pyrite, and the shell cavity fillings of at least one of the siliceous shells contain C-fines and Si-fines, then the shell cavity fillings in the target shale reservoir are composed of calcite, pyrite, C-fines, and Si-fines;

[0155] When the composition of the shell cavity fillings of each of the siliceous shells in the target shale reservoir core slice is independently selected from one of the group consisting of pyrite and C-fines and Si-fines, C-fines and Si-fines, and pyrite, and the shell cavity fillings of at least one of the siliceous shells contain pyrite, and the shell cavity fillings of at least one of the siliceous shells contain C-fines and Si-fines, then the shell cavity fillings in the target shale reservoir are composed of pyrite and C-fines and Si-fines;

[0156] 4) A target shale reservoir argon ion polishing slice with a length of 1 cm, a width of 1 cm, and a thickness of 0.5 cm is prepared based on the target shale reservoir core slice, wherein the top surface and the bottom surface of the target shale reservoir argon ion polishing slice are parallel to the top surface and the bottom surface of the target shale reservoir core sample in the underground state; after a carbon film with a thickness of not more than 1 nm is coated on the surface of the target shale argon ion polishing slice, the C-fines and Si-fines in the shell cavity fillings are obtained by 4 nm of MAPS rock image data volume under the condition that the top surface and the bottom surface of the target shale reservoir argon ion polishing slice are kept at the top surface and the bottom surface of the field of view, respectively, using the target shale reservoir argon ion polishing slice; the 4 nm of MAPS rock image data volume of the C-fines and Si-fines obtained is analyzed on the computer using an image editor (such as an offline image editor ATLAS TM BROWSER-BASED VIEWER) to determine whether the C-fines and Si-fines in the shell cavity fillings are organic silica particle complexes;

[0157] If it is preliminarily determined that the composition of the shell cavity fillings in the target shale reservoir core slice is composed of calcite and C-fines and Si-fines, and the C-fines and Si-fines in the shell cavity fillings are organic silica particle complexes, then the composition of the shell cavity fillings in the target shale reservoir is composed of calcite and organic silica particle complexes;

[0158] If it is preliminarily determined that the composition of the shell cavity filling in the core slice of the target shale reservoir is composed of calcite, pyrite and C fine-grained substance and Si fine-grained substance, and the C fine-grained substance and Si fine-grained substance in the shell cavity filling are organic silicon particle complexes, then the composition of the shell cavity filling in the target shale reservoir is composed of calcite, organic silicon particle complexes and pyrite.

[0159] If it is preliminarily determined that the composition of the shell cavity filling in the core slice of the target shale reservoir is composed of pyrite and C fine-grained substance and Si fine-grained substance, and the C fine-grained substance and Si fine-grained substance in the shell cavity filling are organic silicon particle complexes, then the composition of the shell cavity filling in the target shale reservoir is composed of pyrite and organic silicon particle complexes.

[0160] 5) Based on the C, Si, Ca, Mg, Al, Fe, S and O element area scan results of each shell in the core slice of the target shale reservoir, the filling of each shell cavity filling in the core slice of the target shale reservoir is preliminarily determined. Based on the C, Si, Ca, Mg, Al, Fe, S and O element area scan results of each shell in the core slice of the target shale reservoir, the area of each shell cavity in the core slice of the target shale reservoir and the area of calcite in the cavity filling thereof are determined. Based on the total area of the shell cavity of each shell and the total area of each kind of filling in the cavity filling of each shell, the filling amount of each kind of filling in the shell cavity of the target shale reservoir is determined. Wherein, the filling amount of each kind of filling in the shell cavity = the total area of the filling of the kind in the cavity filling of each shell ÷ the total area of the shell cavity of each shell.

[0161] In this embodiment, as shown in the electron probe spectrum image (such as Figure 1b , Figure 1k , Figure 1l ) and the C, Si, Ca, Mg, Fe, S, Al and O element area scan results of the core slice of the target shale reservoir, the shell cavity filling in the target shale reservoir is composed of calcite and C fine-grained substance and Si fine-grained substance (such as Figure 1c , Figure 1d , Figure 1e , Figure 1f , Figure 1g , Figure 1h , Figure 1i , Figure 1j .

[0162] In this embodiment, the C fine-grained substance and Si fine-grained substance of the shell cavity filling are organic silicon particle complexes (such as Figure 1m , Figure 1n ).

[0163] In this embodiment, the filling amount of calcite in the shell cavity is 61%, and the content of organic silicon particle complexes is 39%.

[0164] 3. According to the composition of the shell cavity filling and the filling amount of calcite in the shell cavity in the target shale reservoir, the paleo-ocean water environment during the deposition period of the target shale reservoir in the work area is determined; wherein,

[0165] If the shell cavity filling in the target shale reservoir is composed of calcite and organic-silica particle complex and the filling amount of calcite in the shell cavity is less than 80%, the paleo-ocean water environment during the deposition period of the target shale reservoir in the work area is: the surface water of the paleo-ocean 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 the 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 the CCD.

[0166] If the shell cavity filling in the target shale reservoir is composed of calcite, organic-silica particle complex and pyrite and the filling amount of calcite in the shell cavity is less than 80%, the paleo-ocean water environment during the deposition period of the target shale reservoir in the work area is: the surface water of the paleo-ocean 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 the CLD, the middle part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CLD and the CCD, and the lower part of the deep water body is anoxic (oxygen-free) sulfidation and located between the CLD and the CCD.

[0167] If the shell cavity filling in the target shale reservoir is composed of pyrite and organic-silica particle complex, the paleo-ocean water environment during the deposition period of the target shale reservoir in the work area is: the surface water of the paleo-ocean 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 the CLD, the middle part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CLD and the CCD, the lower part of the deep water body is anoxic (oxygen-free) sulfidation and located between the CLD and the CCD, and the bottom of the deep water body is anoxic (oxygen-free) sulfidation and located below the CCD.

[0168] In this embodiment, the paleo-ocean water environment during the deposition period of the target shale reservoir in the work area is: the surface water of the paleo-ocean 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 the 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 the CCD.

[0169] Example 2

[0170] The embodiment provides a method for judging the paleo-ocean water environment during the deposition period of the B radiolarian siliceous shale lamina in the B area.

[0171] The difference between it and example 1 is only that:

[0172] In step 1, the longitudinal section of the core in B area is observed, and it is found that there is a layer of lamina with a thickness of 2.9 mm in the B black shale, which is full of white spots with a diameter of about 0.2 mm (as shown in Figure 2a The lamina is a B radiolarian siliceous shale lamina; the rock sample of the B radiolarian siliceous shale lamina is taken as the core sample of the target shale reservoir in the working area.

[0173] In step 2, according to the electron probe spectral image (as shown in Figure 2b 、 Figure 2k 、 Figure 2l ) of the target shale reservoir core slice and the C, Si, Ca, Mg, Fe, S, Al, O element area scan results in this example, it can be known that the shell cavity filling in the target shale reservoir is composed of calcite, pyrite and C fine particle material and Si fine particle material (as shown in Figure 2c 、 Figure 2d 、 Figure 2e 、 Figure 2f 、 Figure 2g 、 Figure 2h 、 Figure 2i 、 Figure 2j The C fine particle material and Si fine particle material filling in the shell cavity are organic silicon particle complexes (as shown in Figure 2m 、 Figure 2n ). The filling amount of calcite in the shell cavity is 16%, the content of organic silicon particle complex is 57%, and the content of pyrite is 23%.

[0174] In step 3, in this example, it is determined that the paleo-ocean water body environment of the target shale reservoir in the working area during the deposition period is: the surface water body of the paleo-ocean 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 the CLD, the middle part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CLD and the CCD, and the lower part of the deep water body is anoxic (oxygen-free) sulfidation and located between the CLD and the CCD.

[0175] Example 3

[0176] The example provides a method for judging the paleo-ocean water body environment of the C radiolarian siliceous shale lamina in the C area during the deposition period.

[0177] The difference between it and example 1 is only that:

[0178] In step 1, the longitudinal section of the core in C area is observed, and it is found that there is a layer of lamina with a thickness of 3.3 mm in the C black shale, which is full of white spots with a diameter of about 0.2 mm (as shown in Figure 3aThe lamina is a C radiolarian siliceous shale lamina, and a C radiolarian siliceous shale lamina rock sample is taken as a target shale reservoir core sample in the work area.

[0179] In step 2, according to the electron probe spectral image (as shown in Figure 3b 、 Figure 3k 、 Figure 3l ) of the target shale reservoir core slice in the embodiment and the C, Si, Ca, Mg, Fe, S, Al, O element area scan results, it can be known that the shell cavity filling in the target shale reservoir is composed of pyrite and C fine-grained substances and Si fine-grained substances (as shown in Figure 3c 、 Figure 3d 、 Figure 3e 、 Figure 3f 、 Figure 3g 、 Figure 3h 、 Figure 3i 、 Figure 3j ). The C fine-grained substances and Si fine-grained substances filling the shell cavity are organic silicon particle complexes (as shown in Figure 3m 、 Figure 3n ). The content of the organic silicon particle complex in the shell cavity is 74%, and the content of the pyrite is 26%.

[0180] In step 3, in the embodiment, it is determined that the paleo-ocean water body environment in the deposition period of the target shale reservoir in the work area is as follows: the surface water body of the paleo-ocean 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 the CLD, the middle part of the deep water body is oxygen-poor (dissolved oxygen content ≤ 2.0 ml / L) and located between the CLD and the CCD, the lower part of the deep water body is anoxic (oxygen-free) sulfidation and located between the CLD and the CCD, and the bottom of the deep water body is anoxic (oxygen-free) sulfidation and located below the CCD.

[0181] The above-described specific embodiments further specifically describe the purposes, technical solutions and advantages of the present application. It should be understood that the above-described specific embodiments are merely specific embodiments of the present application and are not used to limit the protection scope of the present application, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for determining paleo-ocean water body environment, the method comprising: obtaining a core sample of a target shale reservoir in a work area; wherein the target shale reservoir is radiolarite nannofacies; determining a composition of a siliceous shell cavity filler and a filling amount of calcite in the siliceous shell cavity of the target shale reservoir based on the core sample of the target shale reservoir; and determining a paleo-ocean water body environment during deposition of the target shale reservoir in the work area according to the composition of the siliceous shell cavity filler and the filling amount of calcite in the siliceous shell cavity of the target shale reservoir; wherein, if the siliceous shell cavity filler of the target shale reservoir is composed of calcite and organic-silica particle complex and the filling amount of calcite in the siliceous shell cavity is less than 80%, the paleo-ocean water body environment during deposition of the target shale reservoir in the work area is that the surface water body of a paleo-ocean deep water body is oxygen-rich and located above the CSD, the upper part of a deep water body is oxygen-poor and located between the CSD and the CLD, and the lower part of the deep water body is oxygen-poor and located between the CLD and the CCD; if the siliceous shell cavity filler of the target shale reservoir is composed of calcite, organic-silica particle complex and pyrite and the filling amount of calcite in the siliceous shell cavity is less than 80%, the paleo-ocean water body environment during deposition of the target shale reservoir in the work area is that the surface water body of a paleo-ocean deep water body is oxygen-rich and located above the CSD, the upper part of a deep water body is oxygen-poor and located between the CSD and the CLD, the middle part of the deep water body is oxygen-poor and located between the CLD and the CCD, and the lower part of the deep water body is oxygen-poor and located between the CLD and the CCD; and if the siliceous shell cavity filler of the target shale reservoir is composed of pyrite and organic-silica particle complex, the paleo-ocean water body environment during deposition of the target shale reservoir in the work area is that the surface water body of a paleo-ocean deep water body is oxygen-rich and located above the CSD, the upper part of a deep water body is oxygen-poor and located between the CSD and the CLD, the middle part of the deep water body is oxygen-poor and located between the CLD and the CCD, the lower part of the deep water body is oxygen-poor and located between the CLD and the CCD, and the bottom of the deep water body is oxygen-poor and located below the CCD. The method further comprises: determining the composition of the siliceous shell cavity filler of the target shale reservoir based on the core sample of the target shale reservoir, which comprises: preparing a core slice of the target shale reservoir based on the core sample of the target shale reservoir; observing the core slice of the target shale reservoir under an electron probe microscope to determine each siliceous shell in the core slice of the target shale reservoir; performing C, Si, Ca, Mg, Al, Fe, S and O element area scanning on each siliceous shell in the core slice of the target shale reservoir; preliminarily determining the composition of the siliceous shell cavity filler of each siliceous shell in the core slice of the target shale reservoir based on the C, Si, Ca, Mg, Al, Fe, S and O element area scanning results of each siliceous shell in the core slice of the target shale reservoir; and preliminarily determining whether the composition of the siliceous shell cavity filler in the core slice of the target shale reservoir is composed of calcite and C and Si fine particles, or composed of calcite, pyrite and C and Si fine particles, or composed of pyrite and C and Si fine particles based on the preliminarily determined composition of the siliceous shell cavity filler of each siliceous shell in the core slice of the target shale reservoir. ​ ​ ​ ​ ​ 2. The method of claim 1, wherein, ​ ​ ​ ​ The argon ion polished slice of the target shale reservoir is prepared based on the core slice of the target shale reservoir; the C fine particle material and the Si fine particle material in the cavity filling of the siliceous shell are subjected to MAPS rock image data body acquisition; whether the C fine particle material and the Si fine particle material in the cavity filling of the siliceous shell are organic silicon particle complexes is determined based on the acquired MAPS rock image data body of the C fine particle material and the Si fine particle material. If it is preliminarily determined that the composition of the cavity filling of the siliceous shell in the core slice of the target shale reservoir is composed of calcite and the C fine particle material and the Si fine particle material, and the C fine particle material and the Si fine particle material in the cavity filling of the siliceous shell are organic silicon particle complexes, then the composition of the cavity filling of the siliceous shell in the target shale reservoir is composed of calcite and the organic silicon particle complexes. If it is preliminarily determined that the composition of the cavity filling of the siliceous shell in the core slice of the target shale reservoir is composed of calcite, pyrite and the C fine particle material and the Si fine particle material, and the C fine particle material and the Si fine particle material in the cavity filling of the siliceous shell are organic silicon particle complexes, then the composition of the cavity filling of the siliceous shell in the target shale reservoir is composed of calcite, the organic silicon particle complexes and pyrite. If it is preliminarily determined that the composition of the cavity filling of the siliceous shell in the core slice of the target shale reservoir is composed of pyrite and the C fine particle material and the Si fine particle material, and the C fine particle material and the Si fine particle material in the cavity filling of the siliceous shell are organic silicon particle complexes, then the composition of the cavity filling of the siliceous shell in the target shale reservoir is composed of pyrite and the organic silicon particle complexes.

3. The method of claim 2, wherein, The resolution of the acquired MAPS rock image data body of the C fine particle material and the Si fine particle material is 1-10 nm resolution.

4. The method of claim 2, wherein, When the composition of the cavity filling of the siliceous shell in each siliceous shell in the core slice of the target shale reservoir is independently selected from one of calcite and the C fine particle material and the Si fine particle material, composed of calcite, composed of the C fine particle material and the Si fine particle material, and calcite exists in the cavity filling of at least one siliceous shell, and the C fine particle material and the Si fine particle material exist in the cavity filling of at least one siliceous shell, then the composition of the cavity filling of the siliceous shell in the target shale reservoir is composed of calcite and the C fine particle material and the Si fine particle material.

5. The method of claim 2, wherein, When the composition of the cavity filling of the siliceous shell in each siliceous shell in the core slice of the target shale reservoir is independently selected from one of calcite and pyrite and the C fine particle material and the Si fine particle material, composed of calcite and pyrite, composed of calcite and the C fine particle material and the Si fine particle material, composed of pyrite and the C fine particle material and the Si fine particle material, composed of calcite, composed of the C fine particle material and the Si fine particle material, composed of pyrite, and calcite exists in the cavity filling of at least one siliceous shell, pyrite exists in the cavity filling of at least one siliceous shell, and the C fine particle material and the Si fine particle material exist in the cavity filling of at least one siliceous shell, then the composition of the cavity filling of the siliceous shell in the target shale reservoir is composed of calcite, pyrite and the C fine particle material and the Si fine particle material.

6. The method of claim 2, wherein, When the composition of the cavity fillings of each of the siliceous shells in the target shale reservoir core slice is independently selected from one of pyrite and C fine-grained material and Si fine-grained material, C fine-grained material and Si fine-grained material, and pyrite, and there is at least one cavity filling of a siliceous shell containing pyrite, and at least one cavity filling of a siliceous shell containing C fine-grained material and Si fine-grained material, the cavity fillings of the siliceous shells in the target shale reservoir are composed of pyrite and C fine-grained material and Si fine-grained material.

7. The method of claim 2, wherein, The argon ion polished slice of the target shale reservoir has a length of 0.8-2 cm, a width of 0.8-2 cm, and a thickness of 0.3-0.8 cm.

8. The method of claim 2, wherein, Before the C fine-grained material and Si fine-grained material in the cavity fillings are subjected to MAPS rock image data body acquisition, a carbon film with a thickness of not more than 1 nm is plated on the surface of the target shale argon ion polished slice.

9. The method of claim 1, wherein, Based on the target shale reservoir core sample, the filling amount of calcite in the siliceous shell cavity in the target shale reservoir is determined by: Based on the target shale reservoir core sample, a target shale reservoir core slice is prepared; The target shale reservoir core slice is observed under an electron probe microscope to determine each siliceous shell in the target shale reservoir core slice; C, Si, Ca, Mg, Al, Fe, S, and O element area scanning is performed on each siliceous shell in the target shale reservoir core slice; based on the C, Si, Ca, Mg, Al, Fe, S, and O element area scanning results of each siliceous shell in the target shale reservoir core slice, calcite in the cavity fillings of each siliceous shell in the target shale reservoir core slice is preliminarily determined; Based on the C, Si, Ca, Mg, Al, Fe, S, and O element area scanning results of each siliceous shell in the target shale reservoir core slice, the area of the siliceous shell cavity and the area of the calcite in the cavity filling thereof of each siliceous shell in the target shale reservoir core slice are determined; Based on the area of the siliceous shell cavity and the area of the calcite in the cavity filling thereof of each siliceous shell in the target shale reservoir core slice, the total area of the siliceous shell cavity of each siliceous shell and the total area of the calcite in the cavity filling thereof of each siliceous shell are determined; Based on the total area of the siliceous shell cavity of each siliceous shell and the total area of the calcite in the cavity filling thereof of each siliceous shell, the filling amount of calcite in the siliceous shell cavity in the target shale reservoir is determined; wherein the filling amount of calcite in the siliceous shell cavity = the total area of the calcite in the cavity filling thereof of each siliceous shell ÷ the total area of the siliceous shell cavity of each siliceous shell.

10. The method of claim 2 or 9, wherein, The target shale reservoir core slice has a length of 2.5-7 cm, a width of 2.5-5 cm, and a thickness of 30-40 µm.

11. The method of claim 2 or 9, wherein, Before the target shale reservoir core slice is observed under an electron probe microscope, a platinum-gold film is plated on the surface of the target shale reservoir core slice. Before the target shale reservoir core slice is observed under an electron probe microscope, a platinum-gold film is plated on the surface of the target shale reservoir core slice.

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