A method for determining whether siliceous shale is a deep-water traction flow deposit.

Abstract

The present application provides a method for judging whether siliceous shale is deep water traction flow deposition. The method comprises: determining whether the target siliceous shale has characteristics 1, characteristics 2 and characteristics 3, if yes, the target siliceous shale is deep water traction flow deposition; wherein, characteristic 1: the main skeleton of the rock is composed of more than 45% of silt-sand grade porous quartz particles with a particle size of 4-400 μm; characteristic 2: the auxiliary skeleton of the rock is formed by more than 25% of the rock volume of the mud grade porous quartz particle aggregate with a particle size of less than 4 μm distributed between the main skeleton of the rock; characteristic 3: the porous organic matter and non-porous organic matter accounting for 8-15% of the rock volume are distributed between the rock skeleton including the main skeleton and the auxiliary skeleton of the rock. If the siliceous shale is deep water traction flow deposition, it indicates that the area where the siliceous shale is located is a shale gas sweet spot area with high exploration and development potential.

Description

Technical Field

[0001] This invention relates to a method for determining whether siliceous shale is a deep-water traction flow deposit. Background Technology

[0002] Siliceous shale reservoirs are currently one of the main targets for shale gas exploration and development. Exploration and development have confirmed that shale gas production from horizontal wells in siliceous shale varies greatly. This is manifested in the lack of a direct correlation between siliceous shale thickness and gas production, significant differences in gas production among adjacent wells with similar siliceous shale thickness, and inconsistent production characteristics across large-scale gas fields. These phenomena indicate substantial differences in the petrological characteristics of siliceous shale, which is considered a high-quality reservoir. Current research on shale gas reservoirs mainly focuses on shale facies classification and the description of petrological characteristics of different facies, as well as sedimentary environment analysis. There is an urgent need to conduct petrological characterization and analytical studies of siliceous shale to clarify the distribution patterns of siliceous shale with different petrological characteristics, define the petrological characteristics of siliceous shale as a high-quality reservoir, and select optimal shale gas sweet spots, thereby achieving efficient exploration and development of shale gas in siliceous shale reservoirs.

[0003] Currently, the lithofacies classification and petrological characterization of shale generally rely on whole-rock analysis data and total organic carbon (TOC) test data, while the analysis of sedimentary environments depends on inorganic geochemical test data. Research using these analytical data as evidence suggests that organic-rich shale is a result of still-water physicochemical sedimentation. The siliceous shale, as the target material, is formed from the remains of surface microorganisms that settled to the deep seabed, forming siliceous mud that was then buried and diagenetic. However, neither whole-rock nor TOC testing methods can reveal the occurrence state of minerals and organic matter, leading to a flattened understanding of shale lithofacies, a lack of first-hand data characterizing petrological features, and an inability to analyze the sedimentary environments of siliceous shale with different petrological characteristics.

[0004] Due to the fine grain size and high organic matter content of shale, it is difficult to analyze its petrological characteristics, including the occurrence state of minerals and organic matter, at multiple macroscopic scales such as field outcrops, drill cores, and hand specimens, and at multiple microscopic scales such as optical microscopy and electron microscopy. Based on this, argon ion polishing (argon ion polishing) and MAPS (Magnetic Parametric Analysis) techniques have been developed for the petrological characterization of shale. MAPS involves dividing the argon ion polished sample into a series of regular grids, scanning each grid to obtain a secondary electron scan image, and then stitching together the images of all grids to obtain a two-dimensional large-field-of-view scan image data volume. However, due to the diversity and complexity of the occurrence state of minerals and organic matter in shale, current research using argon ion polishing and MAPS techniques mainly focuses on the description of organic pores and organic matter in shale, and has not yet systematically carried out petrological characterization of shale, let alone petrological characterization of siliceous shale with different petrological characteristics.

[0005] In summary, further research is needed on the petrological characteristics of siliceous shale that can serve as high-quality reservoirs, in order to promote the identification of sweet spots for shale gas in siliceous shale reservoirs and thus achieve efficient exploration and development of shale gas. Summary of the Invention

[0006] The purpose of this invention is to provide a technical solution that can determine whether siliceous shale can serve as a high-quality reservoir, thereby promoting the identification of sweet spots for shale gas in siliceous shale reservoirs and achieving efficient exploration and development of shale gas.

[0007] To achieve the above objectives, the present invention provides a method for determining whether siliceous shale is a deep-water traction flow deposit. If the siliceous shale is a deep-water traction flow deposit, it indicates that the area where the siliceous shale is located is a sweet spot for shale gas and has high exploration and development potential.

[0008] Specifically, the present invention provides a method for determining whether siliceous shale is a deep-water traction flow deposit, comprising:

[0009] Obtain the target siliceous shale; wherein the target siliceous shale has a quartz content of more than 90% by mass, a clay content of no more than 1% by mass, and a total organic carbon content of more than 4% by mass;

[0010] Determine whether the target siliceous shale possesses the following characteristics: Characteristic 1, Characteristic 2, and Characteristic 3:

[0011] Feature 1: The main rock framework consists of silt-sand grade porous quartz particles accounting for more than 45% of the rock volume; among which, the silt grade particles have a particle size of 4-62.5μm and account for 30-45% of the rock volume; the sand grade particles have a particle size greater than 62.5μm and not exceeding 400μm and account for 0-15% of the rock volume.

[0012] Feature 2: The auxiliary rock skeleton, consisting of more than 25% of the rock volume, is composed of mud-grade porous quartz particle aggregates distributed between the main rock skeleton; the mud-grade particle size is less than 4μm.

[0013] Feature 3: Porous organic matter and non-porous organic matter accounting for 8-15% of the rock volume, distributed between the rock skeleton, including the main and auxiliary rock skeletons;

[0014] If the target siliceous shale exhibits characteristics 1, 2, and 3, then the target siliceous shale is a deep-water traction flow deposit.

[0015] The inventors of this invention, through analysis and characterization of the petrological characteristics of siliceous shale, discovered that siliceous shale formed by deep-water traction flow deposition has high exploration and development potential. If siliceous shale possesses characteristic 1 (a main rock framework composed of silt-sand-grade porous quartz particles with a particle size of 4-400 μm accounting for more than 45% of the rock volume), characteristic 2 (an auxiliary rock framework formed by aggregates of mud-grade porous quartz particles with a particle size of less than 4 μm accounting for more than 25% of the rock volume, distributed between the main rock framework), and characteristic 3 (porous organic matter and non-porous organic matter accounting for 8-15% of the rock volume, distributed between the rock framework including the main and auxiliary rock frameworks), then this siliceous shale is a petrified product of siliceous mud formed by deep-water traction flow deposition. Thus, characteristics 1, 2, and 3 can effectively characterize it as deep-water traction flow deposition.

[0016] According to a preferred embodiment of the method for determining whether siliceous shale is a deep-water traction flow deposit, obtaining the target siliceous shale includes:

[0017] Whole-rock analysis and total organic carbon testing were performed on the siliceous shale to be tested to determine the mass content of quartz, clay, and total organic carbon in the siliceous shale.

[0018] If the quartz content of the siliceous shale to be tested is higher than 90%, the clay content is less than 1%, and the total organic carbon content is higher than 4%, then the siliceous shale to be tested is considered the target siliceous shale.

[0019] According to a preferred embodiment of the method for determining whether siliceous shale is a deep-water traction flow deposit, determining whether the target siliceous shale has the following characteristics 1, 2, and 3 includes:

[0020] Argon-ion polished discs of the target siliceous shale were prepared using the target siliceous shale core.

[0021] MAPS rock image data volume of argon-ion polished slides of the target siliceous shale;

[0022] Based on the MAPS rock image data of the argon-ion polished section of the target siliceous shale, observe whether the target siliceous shale has features 1, feature 2 and feature 3;

[0023] More preferably, the resolution of the MAPS rock image data volume of the argon-ion polished slide of the target siliceous shale is 4-10 nm.

[0024] More preferably, the length of the argon-ion polishing disc for the target siliceous shale is 0.8-2 cm;

[0025] More preferably, the width of the argon-ion polishing sheet for the target siliceous shale is 0.8-2 cm;

[0026] More preferably, the thickness of the argon-ion polishing sheet for the target siliceous shale is 0.3-0.8 cm (e.g., 0.5 cm);

[0027] More preferably, the polished surface of the argon-ion polishing disc of the target siliceous shale is parallel to the cylindrical surface of the target siliceous shale core;

[0028] More preferably, the acquisition of MAPS rock image data volume of argon-ion polished sheet of target siliceous shale includes: selecting an area with a length and width not exceeding 400 μm on the polished surface of argon-ion polished sheet of target siliceous shale, and acquiring MAPS rock image data volume;

[0029] More preferably, during the acquisition of MAPS rock image data volumes from argon-ion polished discs of the target siliceous shale, the top surface of the argon-ion polished disc of the target siliceous shale is located above the field of view, and the bottom surface of the argon-ion polished disc of the target siliceous shale is located below the field of view, thereby ensuring that all phenomena observed in the acquired MAPS rock image data volumes are merely magnifications of natural phenomena.

[0030] More preferably, in the process of observing whether the target siliceous shale has features 1, 2, and 3 based on the MAPS rock image data volume of the argon-ion polished section of the acquired target siliceous shale, an image editor (e.g., the offline image editor ATLAS) is used. TM The BROWSER-BASEDVIEWER allows for the viewing of MAPS rock image data volumes on a computer.

[0031] According to a preferred embodiment of the method for determining whether siliceous shale is a deep-water traction flow deposit, wherein, in feature 1, the rock framework mainly composed of silt-sand-grade porous quartz particles also includes at least one of carbonate mineral particles (e.g., calcite and / or dolomite), pyrite, dung pellets and silt-grade non-porous quartz particles.

[0032] More preferably, the solution pores of carbonate mineral particles (e.g., solution pores of calcite and / or dolomite) in the main rock framework are filled with mud-grade porous quartz particles and / or mud-grade porous quartz particle aggregates.

[0033] According to a preferred embodiment of the method for determining whether siliceous shale is a deep-water traction flow deposit, feature 2 further includes: mud-grade porous quartz particles that form a mineral film of quartz particles and / or fecal pellets in the main rock framework, the mineral film fusing the auxiliary rock framework with the main rock framework to form a rock framework.

[0034] According to a preferred embodiment of the method for determining whether siliceous shale is a deep-water traction flow deposit, wherein, in feature 3, the organic matter includes honeycomb-rich nanoporous organic matter and non-porous organic matter.

[0035] According to a preferred embodiment of a method for determining whether siliceous shale is a deep-water traction flow deposit, the method further includes: if the target siliceous shale has characteristics 1, 2 and 3, then the silt-sand-grade porous quartz particles in the main rock framework of the target siliceous shale are determined to be siliceous bioclastic shoals formed by deep-water traction flow deposition.

[0036] According to a preferred embodiment of a method for determining whether siliceous shale is a deep-water traction flow deposit, the method further includes: if the target siliceous shale has characteristics 1, 2 and 3, then the mud-scale porous quartz aggregate in the rock auxiliary framework of the target siliceous shale is determined to be a mud-scale siliceous microbial mat formed by deep-water traction flow deposition on a siliceous bioclastic beach.

[0037] According to a preferred embodiment of a method for determining whether siliceous shale is a deep-water traction flow deposit, the method further includes: if the target siliceous shale has characteristics 1, 2 and 3, then determining that the organic matter distributed between the rock skeleton, including the main rock skeleton and the auxiliary rock skeleton, originates from a carbohydrate-rich microbial mat formed by deep-water traction flow deposition on the basis of siliceous bioclastic beaches and mud-class siliceous microbial mats.

[0038] According to a preferred embodiment of a method for determining whether siliceous shale is a deep-water traction flow deposit, the method further includes: if the target siliceous shale has characteristics 1, 2 and 3, then determining that the silty, non-porous quartz particles with a clay film on their surface are residual terrigenous quartz fragments from deep-water traction flow-modified seafloor sediments.

[0039] The technical solution provided by this invention enables the determination of whether siliceous shale is a deep-water traction flow deposit by characterizing its petrological features. If the siliceous shale is a deep-water traction flow deposit, it indicates that the area where the siliceous shale is located is a sweet spot for shale gas, possessing high exploration and development potential. The technical solution provided by this invention helps to optimize the distribution range of deep-water traction flow-deposited siliceous shale, promotes the identification of shale gas sweet spots with siliceous shale as reservoirs, avoids poorly developed reservoir areas, and thus guides efficient shale gas exploration and development, achieving the economic goal of cost reduction and efficiency improvement in shale gas exploration and development. The proposed technical solution of this invention breaks through the bottleneck in the study of deep-water shale sedimentary environments and contributes to the development of deep-water sedimentology. Attached Figure Description

[0040] Figure 1 This is an observation diagram of the MAPS rock image data volume in the image editor in Embodiment 1 of the present invention.

[0041] Figure 2 This is an observation diagram of the MAPS rock image data volume in the image editor in Embodiment 2 of the present invention. Detailed Implementation

[0042] 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.

[0043] The complexity of shale minerals is mainly reflected in the clay mineral content, which ranges from less than 1% to over 50%, leading to significant variations in the shale's resistance to compaction. The organic matter distributed between mineral particles is pyrite, a product of the thermal evolution of sedimentary organic matter through stages such as kerogen, pre-oil bitumen, solid bitumen, and petroleum. Both solid bitumen and petroleum are completely transformed into pyrite. Specifically, pyrite-modified solid bitumen exhibits honeycomb-like nanopores, while pyrite-modified petroleum lacks porosity. Shale with low clay mineral content has a strong resistance to compaction, and the organic matter bears limited pressure from the overlying strata. The honeycomb-rich pyrite-modified solid bitumen and the non-porous pyrite-modified petroleum each retain their original state. Shale with high clay mineral content has a weak resistance to compaction; the organic matter and clay minerals bear the pressure from the overlying strata, and the nanopores in the pyrite-modified solid bitumen are crushed and disappear, resulting in pyrite-modified solid bitumen and pyrite-modified petroleum having similar morphological characteristics and being difficult to distinguish. The diversity and complexity of the occurrence state of coke pitch caused by the compaction effect have led to a lack of systematic characterization of shale petrology at present.

[0044] To eliminate the interference of compaction, systematic petrological characterization of shale needs to be implemented in at least three stages. The first stage involves petrological characterization of shale with low clay mineral content, low compaction intensity, and high organic matter content, analyzing petrological characteristics, and identifying the depositional environment. Once the first stage is completed, the second stage begins. The second stage involves petrological characterization of shale with moderate clay mineral content and moderate compaction, analyzing petrological characteristics, and identifying the depositional environment. Once the second stage is completed, the third stage begins. The third stage involves petrological characterization of shale with high clay mineral content and strong compaction, analyzing petrological characteristics, and identifying the depositional environment. Only by completing these three stages, with the results of the first stage constraining the results of the second stage, and the results of the second stage constraining the results of the third stage, can the interference of compaction be truly eliminated, and a systematic characterization of shale petrological characteristics and depositional environment analysis achieved.

[0045] Deep-water sedimentary environments mainly include still-water physicochemical sedimentary environments, deep-water gravity flow sedimentary environments, and deep-water traction flow sedimentary environments, corresponding to still-water physicochemical sedimentation, deep-water gravity flow sedimentation, and deep-water traction flow sedimentation, respectively. Currently, it is generally believed that coarse-grained clastic rocks formed in deep-water environments are deep-water gravity flow and deep-water traction flow sediments, while fine-grained clastic rocks rich in organic matter (shale) are formed by still-water physicochemical sedimentation. The main basis for the assertion that deep-water shale forms in still-water physicochemical sedimentary environments is inorganic geochemical testing data, but this data is highly ambiguous.

[0046] The inventors of this invention have pioneered the characterization and analysis of shale petrological features, enabling the determination of whether siliceous shale was deposited by deep-water traction currents simply by characterizing and analyzing its petrological features. This solves the problems of characterizing siliceous shale petrological features and analyzing the depositional environment, providing an effective method for systematically characterizing and analyzing shale petrological features.

[0047] Based on this, the present invention provides a method for determining whether siliceous shale is a deep-water traction flow deposit. If the siliceous shale is a deep-water traction flow deposit, it indicates that the area where the siliceous shale is located is a shale gas sweet spot with high exploration and development potential. The technical solution proposed in this invention helps to promote the identification of shale gas sweet spots with siliceous shale as reservoir, thereby achieving efficient exploration and development of shale gas.

[0048] In one specific embodiment, the method for determining whether siliceous shale is a deep-water traction flow deposit provided by the present invention includes:

[0049] Obtain the target siliceous shale; wherein the target siliceous shale has a quartz content of more than 90% by mass, a clay content of no more than 1% by mass, and a total organic carbon content of more than 4% by mass;

[0050] Determine whether the target siliceous shale possesses the following characteristics: Characteristic 1, Characteristic 2, and Characteristic 3:

[0051] Feature 1: The main rock framework consists of silt-sand grade porous quartz particles accounting for more than 45% of the rock volume; among which, the silt grade particles have a particle size of 4-62.5μm and account for 30-45% of the rock volume; the sand grade particles have a particle size greater than 62.5μm and not exceeding 400μm and account for 0-15% of the rock volume.

[0052] Feature 2: A rock auxiliary framework distributed between the main rock framework, consisting of more than 25% of the rock volume composed of mud-grade porous quartz particle aggregates; wherein, the mud-grade particles have a particle size of less than 4 μm;

[0053] Feature 3: Porous organic matter and non-porous organic matter accounting for 8-15% of the rock volume, distributed between the rock skeleton, including the main and auxiliary rock skeletons;

[0054] If the target siliceous shale exhibits characteristics 1, 2, and 3, then the target siliceous shale is a deep-water traction flow deposit.

[0055] The inventors of this invention, through analysis and characterization of the petrological characteristics of siliceous shale, discovered that siliceous shale formed by deep-water traction flow deposition has high exploration and development potential. If siliceous shale possesses characteristic 1 (a main rock framework composed of silt-sand-grade porous quartz particles with a particle size of 4-400 μm accounting for more than 45% of the rock volume), characteristic 2 (an auxiliary rock framework formed by aggregates of mud-grade porous quartz particles with a particle size of less than 4 μm accounting for more than 25% of the rock volume, distributed between the main rock framework), and characteristic 3 (porous organic matter and non-porous organic matter accounting for 8-15% of the rock volume, distributed between the rock framework including the main and auxiliary rock frameworks), then this siliceous shale is a petrified product of siliceous mud formed by deep-water traction flow deposition. Thus, characteristics 1, 2, and 3 can effectively characterize it as deep-water traction flow deposition.

[0056] Further, the target siliceous shale was obtained, including:

[0057] Whole-rock analysis and total organic carbon testing were performed on the siliceous shale to be tested to determine the mass content of quartz, clay, and total organic carbon in the siliceous shale.

[0058] If the quartz content of the siliceous shale to be tested is higher than 90%, the clay content is less than 1%, and the total organic carbon content is higher than 4%, then the siliceous shale to be tested is considered the target siliceous shale.

[0059] Furthermore, determining whether the target siliceous shale possesses the following characteristics 1, 2, and 3 includes:

[0060] Argon-ion polished discs of the target siliceous shale were prepared using the target siliceous shale core.

[0061] MAPS rock image data volume of argon-ion polished slides of the target siliceous shale;

[0062] Based on the MAPS rock image data of the argon-ion polished section of the target siliceous shale, observe whether the target siliceous shale has features 1, feature 2 and feature 3;

[0063] Furthermore, the resolution of the MAPS rock image data volume of the argon-ion polished slides of the target siliceous shale is 4-10 nm.

[0064] Furthermore, the length of the argon-ion polished discs for the target siliceous shale is 0.8-2 cm;

[0065] Furthermore, the width of the argon-ion polished sheet for the target siliceous shale is 0.8-2 cm;

[0066] Furthermore, the thickness of the argon-ion polished sheet for the target siliceous shale is 0.3-0.8 cm;

[0067] Furthermore, the polished surface of the argon-ion polishing disc of the target siliceous shale is parallel to the cylindrical surface of the target siliceous shale core;

[0068] Furthermore, the acquisition of MAPS rock image data from the argon-ion polished sheet of the target siliceous shale includes: selecting an area with a length and width not exceeding 400 μm on the polished surface of the argon-ion polished sheet of the target siliceous shale, and acquiring the MAPS rock image data.

[0069] Furthermore, during the acquisition of MAPS rock image data volumes from argon-ion polished discs of the target siliceous shale, the top surface of the argon-ion polished discs of the target siliceous shale is positioned above the field of view, and the bottom surface of the argon-ion polished discs of the target siliceous shale is positioned below the field of view, thereby ensuring that all phenomena observed in the acquired MAPS rock image data volumes are merely magnifications of natural phenomena.

[0070] Furthermore, based on the MAPS rock image data of the argon-ion polished sections of the target siliceous shale, during the observation of whether the target siliceous shale possesses features 1, 2, and 3, an image editor (e.g., the offline image editor ATLAS) was used. TM The BROWSER-BASEDVIEWER allows for the viewing of MAPS rock image data volumes on a computer.

[0071] Furthermore, in feature 1, the rock framework dominated by silt-sand grade porous quartz particles also includes at least one of carbonate mineral particles (e.g., calcite and / or dolomite), pyrite, dung pellets, and silt grade non-porous quartz particles.

[0072] Furthermore, the solution pores of carbonate mineral grains in the main rock framework (e.g., solution pores of calcite and / or dolomite) are filled with clay-grade porous quartz grains and / or aggregates of clay-grade porous quartz grains.

[0073] Furthermore, feature 2 also includes: mud-grade porous quartz particles that form a mineral film of quartz particles and / or dung pellets in the main rock framework, which fuses the auxiliary rock framework with the main rock framework to form a rock framework.

[0074] Furthermore, in feature 3, the organic matter includes organic matter rich in honeycomb nanopores and organic matter without pores.

[0075] Furthermore, the method also includes: if the target siliceous shale has features 1, features 2 and features 3, then the silt-sand-grade porous quartz particles in the main rock framework of the target siliceous shale are determined to be siliceous bioclastic shoals formed by deep-water traction flow deposition.

[0076] Furthermore, the method also includes: if the target siliceous shale has features 1, features 2 and features 3, then the mud-scale porous quartz aggregate in the rock auxiliary framework of the target siliceous shale is determined to be a mud-scale siliceous microbial mat formed by deep-water traction flow deposition on a siliceous bioclastic beach.

[0077] Furthermore, the method also includes: if the target siliceous shale has features 1, features 2 and features 3, then determining that the organic matter distributed between the rock skeleton, including the main rock skeleton and the auxiliary rock skeleton, originates from the carbohydrate-rich microbial mat formed by deep-water traction flow deposition on the basis of siliceous bioclastic beaches and mud-class siliceous microbial mats.

[0078] Furthermore, the method also includes: if the target siliceous shale has features 1, feature 2 and feature 3, then the silty, non-porous quartz particles with clay films on their surface are identified as residual terrigenous quartz fragments from deep-water traction current-modified seafloor sediments.

[0079] The rock skeleton of siliceous shale is composed of quartz grains, exhibiting strong resistance to compaction. The overlying strata have limited compaction effect on organic matter. The organic matter distributed between the rock skeleton, including the main and auxiliary skeletons, is asphalt peat. Among them, organic matter rich in honeycomb-like nanopores is asphalt peat-modified solid bitumen, while non-porous organic matter is asphalt peat-modified petroleum. The skeleton of siliceous organisms eventually transforms into porous quartz with enlarged rims through dissolution and precipitation reactions. The silt-sand-grade porous quartz grains in the main rock skeleton are fossils of silt-sand-grade siliceous microorganisms. The non-porous silt-grade quartz with clay films on the surface is terrigenous quartz clasts. The mud-grade porous quartz grains filled with carbonate mineral dissolution pores and adhering to the surface of fecal pellets, as well as the aggregates of mud-grade porous quartz grains in the auxiliary rock skeleton, are aggregates of mud-grade siliceous microbial fossils. If a siliceous shale has a main rock framework dominated by silt-sand-grade porous quartz particles, an auxiliary rock framework formed by aggregates of mud-grade porous quartz particles distributed between the main rock framework, and porous and non-porous organic matter distributed between the rock framework including the main and auxiliary rock frameworks, then this siliceous shale is considered to be a lithological product of siliceous mud formed by deep-water traction flow deposition.

[0080] The deep-water traction current depositional process can be divided into three stages: the first stage is the formation of silt-sand-class siliceous bioclastic beaches; the second stage is the formation of mud-class siliceous microbial mats; and the third stage is the formation of carbohydrate-rich microbial mats. Deep-water traction currents have the ability to erode and transport mud-class particles, manifested in two ways: first, they erode muddy sediments, carrying away clay, deposited organic matter, and other mud-class particles, leaving behind terrestrial quartz fragments, marine calcite fragments, marine dolomite fragments, pyrite, and other silt-class particles; second, they transport clay, organic matter, and other mud-class particles that have settled from the upper waters to the deep waters, while abundant silt-sand-class siliceous bioclastic skeletons (siliceous bioclastics) are deposited on the seabed. It is possible that small amounts of silt-class calcite, pyrite, and dung pellets may also be deposited on the seabed. On the seabed, silty-sand-grade siliceous bioclastics mixed with small amounts of silty-grade terrigenous quartz fragments, marine carbonate mineral fragments, pyrite, and dung pellets form siliceous bioclastic shoals, representing the first sedimentary stage of deep-water traction current deposition. Water flows over these bioclastic shoals, bringing abundant oxygen and nutrients. This oxygen and nutrient supply provides the material basis for the formation of mud-grade siliceous microbial mats, which in turn provide an ideal habitat. These mud-grade siliceous microorganisms inhabit the silty-grade terrigenous quartz fragments, silty-sand-grade siliceous bioclastics, and dung pellets with residual clay on their surfaces, resisting erosion by the flowing water. At depths greater than the CCD (Central Coulomb's depth), calcite and dolomite dissolve intensely, and the dissolution pores are occupied by mud-grade siliceous microorganisms. The formation of these mud-grade siliceous microbial mats occurs during the second sedimentary stage of deep-water traction current deposition. As the mud-like siliceous microbial mat develops, the water flow slows down, and the supply of oxygen and nutrients becomes insufficient. The mud-like siliceous microorganisms cease growth, and in their place, carbohydrate-rich microorganisms flourish, forming a carbohydrate-rich microbial mat. This is the third stage of sedimentation in the deep-water traction current deposition process. At this point, deep-water traction current deposition forms seafloor siliceous mud.

[0081] The diagenetic process of siliceous mud can be divided into four stages: shallow burial diagenesis, early intermediate burial diagenesis, late intermediate burial diagenesis, and deep burial diagenesis. In the shallow burial diagenesis stage, sedimentary organic matter composed of carbohydrate-rich microbial remains is transformed into kerogen through condensation reactions. In the early intermediate burial diagenesis stage, all kerogen is transformed into pre-oil bitumen, which expands in volume and occupies some of the primary pores. In the late intermediate burial diagenesis stage, pre-oil bitumen is transformed into solid bitumen and petroleum, expanding in volume, and the primary pores are filled with petroleum, serving as network channels for the initial migration of petroleum. In the deep burial diagenesis stage, solid bitumen and petroleum are transformed into pitchblende and natural gas. Pitchblende solid bitumen develops honeycomb-like nanopores, while pitchblende petroleum lacks porosity; the honeycomb-like organic pores of the pitchblende solid bitumen store natural gas, becoming an effective part of the reservoir.

[0082] During the burial and diagenesis process, siliceous biomass is transformed into porous quartz with secondary enlargement; silty-sand-grade siliceous bioclastics are transformed into silty-sand-grade rich-porosity quartz; mud-grade siliceous biomass is transformed into mud-grade rich-porosity quartz; and mud-grade rich-porosity quartz films develop on the surface of fecal pellets. The secondary enlargement and fusion of all rich-porosity quartz forms the rock skeleton, effectively protecting organic matter from the alteration caused by compaction.

[0083] Example 1:

[0084] This embodiment provides a method for determining whether the siliceous shale in target siliceous shale area A is a deep-water traction flow deposit, including:

[0085] 1. Perform whole-rock analysis and total organic carbon testing on the core samples taken from the target siliceous shale area A to determine the mass content of quartz, clay, and total organic carbon in the siliceous shale to be tested. If the mass content of quartz in the siliceous shale to be tested is higher than 90%, the mass content of clay is less than 1%, and the mass content of total organic carbon is higher than 4%, then the siliceous shale to be tested will be regarded as the target siliceous shale.

[0086] In this embodiment, the quartz content of the siliceous shale to be tested is higher than 90%, the clay content is not more than 1%, and the total organic carbon content is higher than 4%. Therefore, the siliceous shale to be tested is used as the target siliceous shale, and the core of the siliceous shale to be tested can be directly used as the core of the siliceous shale to be tested.

[0087] 2. Prepare argon-ion polished discs of the target siliceous shale using the core of the target siliceous shale; wherein the argon-ion polished disc of the target siliceous shale is 2cm long, 2cm wide, and 0.5cm thick; the polished surface of the argon-ion polished disc of the target siliceous shale is parallel to the cylindrical surface of the target siliceous shale core, and the top and bottom surfaces of the argon-ion polished disc are marked.

[0088] 3. Select an area with a length and width not exceeding 400 μm on the polished surface of the argon-ion polished disc of the target siliceous shale, and acquire MAPS rock image data volume with a resolution of 4 nm. During the acquisition of MAPS rock image data volume, the top surface of the argon-ion polished disc of the target siliceous shale is located above the field of view, and the bottom surface of the argon-ion polished disc of the target siliceous shale is located below the field of view, thereby ensuring that all phenomena observed in the acquired MAPS rock image data volume are merely magnified natural phenomena.

[0089] 4. Use an image editor (the offline version of the image editor ATLAS). TM The BROWSER-BASEDVIEWER is used to observe the acquired MAPS rock image data on a computer; to observe whether the target siliceous shale has at least one of the three features: feature 1, feature 2, and feature 3.

[0090] Feature 1: The rock framework is composed of silt-sand grade porous quartz particles accounting for more than 45% of the rock volume; the rock framework also includes at least one of carbonate mineral particles (e.g., calcite and / or dolomite), pyrite, dung pellets, and silt-grade non-porous quartz particles, and clay-grade porous quartz particles and / or clay-grade porous quartz particle aggregates filling the dissolution pores (e.g., dissolution pores of calcite and / or dolomite) of the carbonate mineral particles in the rock framework; wherein, the silt-grade particles have a particle size of 4-62.5 μm and account for 30-45% of the rock volume; the sand-grade particles have a particle size greater than 62.5 μm and not exceeding 400 μm and account for 0-15% of the rock volume;

[0091] Feature 2: A rock auxiliary framework consisting of aggregates of mud-grade porous quartz particles accounting for more than 25% of the rock volume, distributed between the main rock framework; mud-grade porous quartz particles serving as mineral films of quartz particles and / or fecal pellets in the main rock framework, which fuse the rock auxiliary framework with the main rock framework to form a rock framework; mud-grade particles with a particle size of less than 4 μm.

[0092] Feature 3: Porous organic matter and non-porous organic matter accounting for 8-15% of the rock volume, distributed between the rock skeleton, including the main and auxiliary rock skeletons;

[0093] If the target siliceous shale exhibits characteristics 1, 2, and 3, then the target siliceous shale is a deep-water traction flow deposit.

[0094] Furthermore, if the target siliceous shale exhibits characteristics 1, 2, and 3, then it is determined that: the silt-sand-grade porous quartz particles in the main rock framework of the target siliceous shale are siliceous bioclastic shoals formed by deep-water traction current deposition; the mud-grade porous quartz aggregates in the auxiliary rock framework of the target siliceous shale are mud-grade siliceous microbial mats formed by deep-water traction current deposition on the basis of siliceous bioclastic shoals; the organic matter distributed between the rock framework, including the main and auxiliary rock frameworks, originates from carbohydrate-rich microbial mats formed by deep-water traction current deposition on the basis of siliceous bioclastic shoals and mud-grade siliceous microbial mats; and the silt-grade non-porous quartz particles with clay films on their surfaces are residual terrigenous quartz fragments from deep-water traction current-modified seafloor sediments.

[0095] In this embodiment, as Figure 1 As shown, the main rock framework of the target siliceous shale is composed of silt-sand grade porous quartz particles (e.g., Figure 1 a, b, and i in the text), and including silt-grade non-porous quartz with clay films scattered among silt-grade porous quartz particles (such as... Figure 1 f), silty calcite (such as ... Figure 1e), silt-grade pyrite (such as...) Figure 1 (as indicated by the arrow in 'a'), silty sand-grade fecal pellets (such as...) Figure 1 (e.g., solid circle in g); the calcite dissolution pores in the main rock framework of the target siliceous shale are filled with mud-sized porous quartz particles (e.g., Figure 1 The target siliceous shale has a rock-supporting framework composed of aggregates of mud-scale porous quartz particles (such as...). Figure 1 The rock is composed of (a, c, d, g, h, i); mud-grade porous quartz particles act as a mineral film of quartz particles and dung pellets in the main rock framework, fusing the auxiliary rock framework with the main rock framework to form the rock framework. The organic matter between the rock frameworks of the target siliceous shale consists of organic matter rich in honeycomb nanopores (such as... Figure 1 c) and non-porous organic matter (such as Figure 1 The target siliceous shale is composed of silt (h) and organic matter within its rock framework accounts for 12.5% ​​of the rock volume. Analysis of this nested structure reveals that the main rock framework is the lithification product of silty-sand-class siliceous bioclastic shoals formed in the first stage of deep-water traction current deposition; the secondary rock framework is the lithification product of mud-class siliceous microbial mats formed in the second stage of deep-water traction current deposition; and the organic matter distributed within the rock framework is the lithification product of carbohydrate-rich microbial mats formed in the third stage of deep-water traction current deposition. Within the main rock framework of the siliceous shale, silt-sand-class porous quartz particles (such as...) constitute... Figure 1 In this context, a, b, and i) represent the lithification products of silty-sand-grade siliceous bioclastics deposited by water sedimentation, including silty-grade non-porous quartz particles with clay films (such as...). Figure 1 f) refers to silty terrigenous quartz fragments remaining after deep-water traction currents have altered seafloor muddy sediments, with residual clay on their surface, and silty calcite (such as...). Figure 1 (e) and pyrite (such as Figure 1 The arrow in 'a' indicates silty, detrital particles remaining from seabed sediments and / or settled by water, such as silty, fecal pellets (e.g.) Figure 1 The solid circle in g represents silty sand particles settled by water. In the rock-supporting framework of siliceous shale, mud-sized porous quartz aggregates (such as...) Figure 1 (a, c, d, g, h, i) are petrification products of mud-grade siliceous microbial mats. The skeleton of the mud-grade siliceous microorganisms is transformed into porous quartz, and the secondary quartz on its surface enlarges and fuses with the porous quartz to form aggregates; calcite dissolution-porous mud-grade quartz (such as...) Figure 1 The arrow in 'e' indicates the lithification of siliceous microorganisms of mud class. This is distributed within the organic matter between the rock skeleton, including the main and secondary rock frameworks, and is rich in porosity (such as...). Figure 1 c) refers to the products of solid asphalt coking, non-porous organic matter (such as... Figure 1In the above, h) represents the products of petroleum coking and bituminization, all of which are thermal evolution products of carbohydrate-rich microbial mats during burial and diagenesis. In the shallow burial and diagenesis stage, carbohydrate-rich microbial mats transform into kerogen; in the early stage of medium burial and diagenesis, kerogen is completely transformed into pre-oil bitumen; in the late stage of medium burial and diagenesis, pre-oil bitumen is completely transformed into solid bitumen and petroleum, and siliceous biological skeletons are transformed into porous quartz with secondary enlargement; in the deep burial and diagenesis stage, both solid bitumen and petroleum are transformed into coking bitumen, of which coking bitumen-modified solid bitumen is rich in honeycomb nanopores, while coking bitumen-modified petroleum lacks porosity.

[0096] In summary, in this embodiment, the target siliceous shale satisfies characteristics 1, 2, and 3, indicating it is a deep-water traction current deposit. Furthermore, the silt-sand-sized porous quartz particles in the main rock framework of the target siliceous shale are siliceous bioclastic shoals formed by deep-water traction current deposition. The mud-sized porous quartz aggregates in the auxiliary rock framework are mud-sized siliceous microbial mats formed by deep-water traction current deposition on the basis of siliceous bioclastic shoals. The organic matter distributed between the rock framework, including the main and auxiliary frameworks, originates from carbohydrate-rich microbial mats formed by deep-water traction current deposition on the basis of siliceous bioclastic shoals and mud-sized siliceous microbial mats. The silt-sized non-porous quartz particles with clay films on their surfaces are residual terrigenous quartz fragments from deep-water traction current-modified seafloor sediments. The area where the target siliceous shale is located (i.e., Target Siliceous Shale Area A) is a sweet spot for shale gas, possessing high exploration and development potential.

[0097] Example 2

[0098] This embodiment provides a method for determining whether the siliceous shale in the target siliceous shale area is a deep-water traction flow deposit.

[0099] The method used in this embodiment is the same as that used in Embodiment 1.

[0100] like Figure 2 As shown, the main rock framework of the target siliceous shale is composed of silt-sized porous quartz particles (such as...). Figure 2 (a and d in the text), and includes non-porous quartz with clay films scattered among silt-grade porous quartz particles (such as... Figure 2 h), calcite (such as Figure 2 f), dolomite (such as f) Figure 2 g), fecal pellets (such as g) Figure 2 i) etc.; the calcite dissolution pores in the main rock framework of the target siliceous shale are filled with mud-sized porous quartz particles (such as i) Figure 2 (The arrow in f indicates the location of the dolomite), and the solution pores of the dolomite are filled with mud-sized porous quartz particles (such as...). Figure 2The target siliceous shale has a rock-supporting framework composed of aggregates of mud-scale porous quartz particles (such as...). Figure 2 The rock is composed of (a, b, e) particles; mud-grade porous quartz particles act as a mineral film for quartz particles and dung pellets in the main rock framework, fusing the auxiliary rock framework with the main rock framework to form the rock framework. The organic matter between the rock framework particles of the target siliceous shale consists of organic matter rich in honeycomb-like nanopores (such as...). Figure 2 e) and non-porous organic matter (such as Figure 2 In the analysis of composition c), the organic matter within the rock framework of the target siliceous shale accounts for 9.6% of the rock volume. Analyzing this nested structure of the siliceous shale, the main rock framework is the lithification product of silty-sand-class siliceous bioclastic shoals formed in the first stage of deep-water traction current deposition; the secondary rock framework is the lithification product of mud-class siliceous microbial mats formed in the second stage of deep-water traction current deposition; and the organic matter distributed within the rock framework is the lithification product of carbohydrate-rich microbial mats formed in the third stage of deep-water traction current deposition. Within the main rock framework of the siliceous shale, silty porous quartz particles (such as…) Figure 2 In the text, (a) and (d) represent the lithification products of silty siliceous bioclastics deposited by water sedimentation, and silty non-porous quartz particles with clay films (such as...). Figure 2 In this context, h) refers to silty terrigenous quartz fragments remaining after deep-water traction currents have altered seafloor muddy sediments, with residual clay on their surface, and silty calcite (such as...). Figure 2 f) refers to silty detrital particles remaining from seabed sediments and / or settled by water, such as silty dolomite (e.g. Figure 2 In this context, "g" refers to silty particles remaining in seabed muddy sediments due to the alteration of dolomite cement by deep-water traction currents, such as silty fecal pellets (e.g.) Figure 2 In this context, i) represents silty particles settled by water. In the rock-supporting framework of siliceous shale, mud-sized porous quartz aggregates (such as...) Figure 2 a, b, and e in the text represent the petrification products of mud-grade siliceous microbial mats. The skeleton of these mud-grade siliceous microorganisms transforms into porous quartz, and the secondary quartz on its surface enlarges and fuses with the porous quartz to form aggregates. Calcite dissolution-porous mud-grade quartz (such as...) Figure 2 (as indicated by the arrow in f) and dolomite-soluble porous mud-grade rich porosity quartz (such as...) Figure 2 The arrow in 'g' indicates the lithification of siliceous microorganisms of mud class. This is distributed within the organic matter between the rock skeleton, including the main and auxiliary rock frameworks, and is rich in porosity (such as...). Figure 2 In this context, 'e' represents the product of solid asphalt coking, a non-porous organic matter (such as...). Figure 2c) represents the products of petroleum coking and bituminization, all of which are thermal evolution products of carbohydrate-rich microbial mats during burial and diagenesis. In the shallow burial and diagenesis stage, carbohydrate-rich microbial mats transform into kerogen; in the early stage of medium burial and diagenesis, kerogen is completely transformed into pre-oil bitumen; in the late stage of medium burial and diagenesis, pre-oil bitumen is completely transformed into solid bitumen and petroleum, and siliceous biological skeletons are transformed into porous quartz with secondary enlargement; in the deep burial and diagenesis stage, both solid bitumen and petroleum are transformed into coking bitumen, of which coking bitumen-modified solid bitumen is rich in honeycomb nanopores, while coking bitumen-modified petroleum lacks porosity.

[0101] In summary, in this embodiment, the target siliceous shale satisfies characteristics 1, 2, and 3, indicating it is a deep-water traction current deposit. Furthermore, the silt-sand-sized porous quartz particles in the main rock framework of the target siliceous shale are siliceous bioclastic shoals formed by deep-water traction current deposition. The mud-sized porous quartz aggregates in the auxiliary rock framework are mud-sized siliceous microbial mats formed by deep-water traction current deposition on the basis of siliceous bioclastic shoals. The organic matter distributed between the rock framework, including the main and auxiliary frameworks, originates from carbohydrate-rich microbial mats formed by deep-water traction current deposition on the basis of siliceous bioclastic shoals and mud-sized siliceous microbial mats. The silt-sized non-porous quartz particles with clay films on their surfaces are residual terrigenous quartz fragments from deep-water traction current-modified seafloor sediments. The area where the target siliceous shale is located (i.e., Target Siliceous Shale Area B) is a sweet spot for shale gas, possessing high exploration and development potential.

[0102] 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 whether a siliceous shale is a deep-water traction current deposit, comprising: obtaining a target siliceous shale; wherein the quartz content of the target siliceous shale is higher than 90% and the clay content of the target siliceous shale is not more than 1% and the total organic carbon content of the target siliceous shale is higher than 4%; determining whether the target siliceous shale has the following characteristics 1, 2 and 3: Characteristic 1: the main framework of the rock is composed of more than 45% of silt-sand grade porous quartz particles in terms of rock volume; wherein the particle size of the silt grade is 4-62.5 μm, and the silt grade porous quartz particles account for 30-45% of the rock volume; the particle size of the sand grade is greater than 62.5 μm and not more than 400 μm, and the sand grade porous quartz particles account for 0-15% of the rock volume; Characteristic 2: the auxiliary framework of the rock formed by more than 25% of the rock volume of the silt grade porous quartz particle aggregate distributed between the main framework of the rock; the particle size of the silt grade is less than 4 μm; Characteristic 3: the porous organic matter and non-porous organic matter accounting for 8-15% of the rock volume distributed between the rock framework including the main framework and the auxiliary framework of the rock; if the target siliceous shale has characteristics 1, 2 and 3, the target siliceous shale is a deep-water traction current deposit; wherein determining whether the target siliceous shale has the following characteristics 1, 2 and 3 comprises: using the target siliceous shale core to make an argon ion polished slice of the target siliceous shale; collecting a MAPS rock image data body of the argon ion polished slice of the target siliceous shale; based on the collected MAPS rock image data body of the argon ion polished slice of the target siliceous shale, observing whether the target siliceous shale has characteristics 1, 2 and 3.

2. The method of claim 1, wherein, Obtaining a target siliceous shale comprises: performing whole rock analysis and total organic carbon test on the siliceous shale to be detected to determine the mass content of quartz, clay and total organic carbon in the siliceous shale to be detected; if the mass content of quartz in the siliceous shale to be detected is higher than 90%, the mass content of clay is not more than 1%, and the mass content of total organic carbon is higher than 4%, the siliceous shale to be detected is taken as the target siliceous shale.

3. The method of claim 1, wherein, The resolution of the collected MAPS rock image data body of the argon ion polished slice of the target siliceous shale is 4-10 nm resolution.

4. The method of claim 1, wherein, The length of the argon ion polished slice of the target siliceous shale is 0.8-2 cm, the width of the argon ion polished slice of the target siliceous shale is 0.8-2 cm, and the thickness of the argon ion polished slice of the target siliceous shale is 0.3-0.8 cm.

5. The method of claim 1, wherein, The polishing surface of the argon ion polished slice of the target siliceous shale is parallel to the cylindrical surface of the target siliceous shale core.

6. The method of claim 1, wherein, Collecting the MAPS rock image data body of the argon ion polished slice of the target siliceous shale comprises: selecting an area with a length and a width not more than 400 μm in the polishing surface of the argon ion polished slice of the target siliceous shale, and collecting the MAPS rock image data body.

7. The method of claim 1, wherein, During the process of collecting the MAPS rock image data body of the argon ion polished slice of the target siliceous shale, the top surface of the argon ion polished slice of the target siliceous shale is located above the field of view, and the bottom surface of the argon ion polished slice of the target siliceous shale is located below the field of view.

8. The method of claim 1, wherein, In Feature 1, the rock primary framework dominated by silt-sand grade porous quartz grains further includes at least one of carbonate mineral grains, pyrite, fecal pellets, and silt grade non-porous quartz grains.

9. The method of claim 8, wherein, Silt grade porous quartz grains and / or silt grade porous quartz grain aggregates filling in the dissolved pores of the carbonate mineral grains in the rock primary framework.

10. The method of claim 1, wherein, The features further include silt grade porous quartz grains as mineral coatings of the quartz grains and / or fecal pellets in the rock primary framework, which fuses the rock secondary framework with the rock primary framework to form the rock framework.

11. The method of claim 1, wherein, In Feature 3, the organic matter includes honeycomb-like nanoporous organic matter and non-porous organic matter.

12. The method of claim 1, wherein, The method further includes determining that the silt-sand grade porous quartz grains in the rock primary framework of the target siliceous shale are siliceous bioclastic shoals formed by deep-water traction current deposition if the target siliceous shale has Feature 1, Feature 2, and Feature 3.

13. The method of claim 1, wherein, The method further includes determining that the silt grade porous quartz aggregates in the rock secondary framework of the target siliceous shale are silt grade microbial mats formed on the basis of the siliceous bioclastic shoals by deep-water traction current deposition if the target siliceous shale has Feature 1, Feature 2, and Feature 3.

14. The method of claim 1, wherein, The method further includes determining that the organic matter distributed between the rock framework including the primary framework and the secondary framework is a carbohydrate-rich microbial mat formed on the basis of the siliceous bioclastic shoals and the silt grade microbial mats by deep-water traction current deposition if the target siliceous shale has Feature 1, Feature 2, and Feature 3.

15. The method of claim 1, wherein, The method further includes determining that the silt-sand grade non-porous quartz grains with clay coatings on the grain surface are residual terrigenous quartz clasts of the seafloor sediments remolded by deep-water traction current if the target siliceous shale has Feature 1, Feature 2, and Feature 3.

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