Method for judging whether siliceous shale is subjected to deepwater traction flow deposition or not

Abstract

The invention provides a method for judging whether siliceous shale is in deepwater traction flow deposition or not. The method comprises the steps that whether target siliceous shale has a feature 1, a feature 2 and a feature 3 or not is determined, and if yes, the target siliceous shale is deep water traction flow deposition; the method is characterized in that 1, silt-sand-grade porous quartz particles with the particle size of 4-400 microns account for 45% or above of the volume of the rock to form a rock main framework; 2, a rock auxiliary skeleton which is distributed among the rock main skeletons and is formed by mud-grade porous quartz particle polymers with the particle size of less than 4 microns accounting for 25% or more of the volume of the rock; and 3, porous organic matters and pore-free organic matters which are distributed between the rock skeletons including the main rock skeleton and the auxiliary rock skeleton and account for 8-15% of the volume of the rock. If the siliceous shale is in deepwater traction flow deposition, the area where the siliceous shale is located is the shale gas dessert area, and high exploration and development potential is achieved.

Description

Technical Field

[0001] The invention relates to a method for judging whether siliceous shale is deep-water traction flow deposit. Background Art

[0002] Siliceous shale reservoirs are currently one of the primary targets for shale gas exploration and development. Exploration and development have confirmed that the production of shale gas horizontal wells in siliceous shales varies significantly, manifested in a lack of correlation between siliceous shale thickness and gas production, significant differences in gas production between adjacent wells of similar siliceous shale thickness, and varying production characteristics across large-scale gas fields. These phenomena indicate that the petrological characteristics of siliceous shales, which serve as high-quality reservoirs, vary significantly. Current research on shale gas reservoirs primarily focuses on shale lithofacies division, petrological characterization of different lithofacies, and sedimentary environment analysis. Currently, there is an urgent need to conduct petrological characterization and analysis of siliceous shales, identify the distribution patterns of siliceous shales with different petrological characteristics, clarify the petrological characteristics of siliceous shales as high-quality reservoirs, and prioritize shale gas sweet spots, thereby achieving efficient exploration and development of shale gas using siliceous shales as reservoirs.

[0003] Currently, shale facies classification and petrological characterization generally rely on whole-rock analysis and total organic carbon (TOC) data, while sedimentary environment analysis relies on inorganic geochemical data. Research based on these analytical data indicates that organic-rich shales are the result of hydrostatic physical and chemical deposition, while the target siliceous shales are formed by the sedimentation of surface microbial remains onto the deep seafloor, forming siliceous mud that consolidated into rock during burial. Neither whole-rock nor TOC methods can reveal information about the distribution of minerals and organic matter, leading to a flattened understanding of shale facies, a lack of access to first-hand data characterizing petrological characteristics, and even greater inability to analyze the depositional environments of siliceous shales with diverse petrological characteristics.

[0004] Due to the fine grain size and high organic matter content of shale, petrological characteristics, including the occurrence of minerals and organic matter, are difficult to analyze at multiple macroscales, such as field outcrops, drill cores, and hand specimens, and at multiple microscales, such as optical and electron microscopes. Based on this, argon ion polishing and MAPS techniques have been developed for shale petrological analysis. MAPS divides the argon ion polished sample into a series of regular grids, scans and images each grid, obtains a secondary electron scanning image, and then stitches all the grid images together to produce a two-dimensional large-field scanning image data volume. However, due to the diversity and complexity of the occurrence of shale minerals and organic matter, current research using argon ion polishing and MAPS techniques primarily focuses on describing the organic pores and organic matter in shales. Systematic petrological characterization of shales, and even less research on petrological characterization of siliceous shales with diverse petrological characteristics, has not yet been conducted.

[0005] In summary, there is still a need to study the petrological characteristics of siliceous shales that can serve as high-quality reservoirs in siliceous shales, so as to promote the identification of shale gas sweet spots with siliceous shales as reservoirs, thereby realizing efficient exploration and development of shale gas. Summary of the Invention

[0006] The purpose of the present invention is to provide a technical solution that can determine whether siliceous shale can serve as a high-quality reservoir, thereby promoting the determination of shale gas sweet spots with siliceous shale as a reservoir, and thus realizing efficient exploration and development of shale gas.

[0007] In order to achieve the above objectives, the present invention provides a method for determining whether siliceous shale is deposited by deep-water traction flow. If the siliceous shale is deposited by deep-water traction flow, it indicates that the area where the siliceous shale is located is a shale gas sweet spot with 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] Obtaining target siliceous shale; wherein the target siliceous shale has a quartz mass content greater than 90%, a clay mass content not exceeding 1%, and a total organic carbon mass content greater than 4%;

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

[0011] Characteristic 1: The main rock skeleton is composed of silt-sand porous quartz particles, which account for more than 45% of the rock volume. Among them, the silt-grade particle size is 4-62.5μm, and the silt-grade porous quartz particles account for 30-45% of the rock volume. The sand-grade particle size is greater than 62.5μm and does not exceed 400μm, and the sand-grade porous quartz particles account for 0-15% of the rock volume.

[0012] Feature 2: The auxiliary rock framework is formed by aggregates of mud-grade porous quartz particles, which account for more than 25% of the rock volume and are distributed between the main rock frameworks. The mud-grade particle size is less than 4 μm.

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

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

[0015] After analyzing and characterizing the petrological characteristics of siliceous shale, the inventors of the present invention found that siliceous shale formed by deep-water traction flow deposition has high exploration and development potential. If the siliceous shale has characteristic 1 (a main rock skeleton 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 skeleton formed by aggregates of mud-grade porous quartz particles with a particle size of less than 4 μm distributed between the main rock skeletons, accounting for more than 25% of the rock volume), and characteristic 3 (porous organic matter and non-porous organic matter distributed between the rock skeletons, including the main rock skeleton and the auxiliary rock skeleton, accounting for 8-15% of the rock volume), then this siliceous shale is a lithification product of siliceous mud formed by deep-water traction flow deposition. Therefore, 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 deposited by deep-water traction flow, obtaining target siliceous shale includes:

[0017] Conduct whole-rock analysis and total organic carbon testing on the siliceous shale to be tested to determine the mass content of quartz, clay, and total organic carbon in the siliceous shale to be tested;

[0018] If the quartz mass content of the siliceous shale to be tested is higher than 90%, the clay mass content is no more than 1%, and the total organic carbon mass content is higher than 4%, the siliceous shale to be tested is taken as the target siliceous shale.

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

[0020] using a target siliceous shale core to produce an argon ion polished sheet of the target siliceous shale;

[0021] Collect MAPS rock image data of argon ion polished slices of target siliceous shale;

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

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

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

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

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

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

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

[0029] More preferably, during the process of acquiring the MAPS rock image data volume of the argon ion polished sheet of the target siliceous shale, the top surface of the argon ion polished sheet of the target siliceous shale is located above the field of view, and the bottom surface of the argon ion polished sheet 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;

[0030] More preferably, based on the MAPS rock image data volume of the argon ion polished slice of the target siliceous shale, an image editor (such as an offline image editor ATLAS TM BROWSER-BASEDVIEWER) is used to observe the MAPS rock image data on a computer.

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

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

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

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

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

[0036] According to a preferred embodiment of the method for determining whether siliceous shale is deposited by deep-water traction flow, the method further includes: if the target siliceous shale has characteristics 1, 2 and 3, then determining that the mud-grade porous quartz aggregates in the rock auxiliary skeleton of the target siliceous shale are mud-grade siliceous microbial mats formed by deep-water traction flow deposition on the basis of siliceous bioclastic beach.

[0037] According to a preferred embodiment of the method for determining whether siliceous shale is deposited by deep-water traction flow, 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 skeletons including the main rock skeleton and the auxiliary rock skeleton is derived from the carbohydrate-rich microbial mat formed by deep-water traction flow deposition on the basis of siliceous bioclastic beaches and mud-grade siliceous microbial mats.

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

[0039] The technical solution provided by the present invention can be used to determine whether the siliceous shale is a deep-water traction flow deposit by characterizing the petrological characteristics of the siliceous shale. 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 provided by the present invention helps to optimize the distribution range of siliceous shale deposited by deep-water traction flow, promote the determination of shale gas sweet spots with siliceous shale as a reservoir, avoid areas with poor reservoir development, and then guide the efficient exploration and development of shale gas, so as to achieve the economic goal of exploring and developing shale gas with reduced costs and increased efficiency. The introduction of the technical solution of the present invention has broken the bottleneck of deep-water shale sedimentary environment research and helped to promote the development of deep-water sedimentology. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is an observation diagram of the MAPS rock image data volume in the image editor in Example 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 Example 2 of the present invention. DETAILED DESCRIPTION

[0042] To make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. Here, the exemplary 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 primarily reflected in the clay mineral content, which ranges from less than 1% to over 50%. This results in a wide range of shale resistance to compaction. The organic matter distributed between mineral particles is pyroasphalt, a product of the thermal evolution of sedimentary organic matter through stages such as kerogen, pre-oil asphalt, solid asphalt, and oil. Both solid asphalt and oil are completely converted to pyroasphalt. Pyroasphalted solid asphalt develops honeycomb nanopores, while pyroasphalted oil lacks pores. Shale particles with low clay mineral content have a strong resistance to compaction, as the organic matter bears limited pressure from the overlying strata. The honeycomb nanopore-rich pyroasphalted solid asphalt and the non-porous pyroasphalted oil each retain their original state. Shale with high clay mineral content has a weak resistance to compaction. As the organic matter and clay minerals bear the pressure of the overlying strata, the nanopores in the pyroasphalted solid asphalt are crushed and disappear, resulting in the morphological characteristics of the pyroasphalted solid asphalt and pyroasphalted oil being identical and difficult to distinguish. It is precisely because of the influence of compaction that the occurrence state of pyrobitumen is diverse and complex, resulting in a lack of systematic characterization in shale petrology at this stage.

[0044] To eliminate the interference of compaction, systematic shale petrology characterization needs to be implemented in at least three stages. The first stage involves petrological characterization of shales with low clay mineral content, low compaction intensity, and high organic matter content, and interpreting their petrological characteristics to identify the sedimentary environment. Upon completion of the first stage, the second stage begins. The second stage involves petrological characterization of shales with medium clay mineral content and medium compaction intensity, interpreting their petrological characteristics to identify the sedimentary environment. Once the second stage is completed, the third stage begins. The third stage involves petrological characterization of shales with high clay mineral content and strong compaction intensity, interpreting their petrological characteristics to identify the sedimentary environment. Only after completing these three stages, and with the insights from the first stage constraining those from the second stage and vice versa, can the interference of compaction be truly eliminated and systematic characterization of shale petrology and analysis of sedimentary environments be achieved.

[0045] Deepwater sedimentary environments primarily include still-water physicochemical deposition, deepwater gravity flow deposition, and deepwater traction flow deposition, corresponding to still-water physicochemical deposition, deepwater gravity flow deposition, and deepwater traction flow deposition. Currently, it is generally believed that coarse-grained clastic rocks formed in deepwater environments are deposited by deepwater gravity flow and deepwater traction flow, while organic-rich fine-grained clastic rocks (shales) are deposited by still-water physicochemical deposition. The primary basis for the conclusion that deepwater shales formed in still-water physicochemical deposition is inorganic geochemical data, but this is highly open to interpretation.

[0046] The inventors of the present invention pioneered the characterization and analysis of the petrological characteristics of shale, and achieved the goal of determining whether the siliceous shale was deposited by deep-water traction flow by only characterizing and analyzing the petrological characteristics of siliceous shale. This solved the problem of characterizing the petrological characteristics of siliceous shale and analyzing the sedimentary environment, and provided an effective method for reference for the systematic characterization and analysis of the petrological characteristics of shale.

[0047] Based on this, the present invention provides a method for determining whether siliceous shale is a deepwater traction flow deposit. If so, this indicates that the area containing the siliceous shale is a shale gas sweet spot with high exploration and development potential. This technical solution will help identify shale gas sweet spots in siliceous shale reservoirs, thereby achieving efficient shale gas exploration and development.

[0048] In one embodiment, the present invention provides a method for determining whether siliceous shale is a deepwater traction flow deposit, comprising:

[0049] Obtaining target siliceous shale; wherein the target siliceous shale has a quartz mass content greater than 90%, a clay mass content not exceeding 1%, and a total organic carbon mass content greater than 4%;

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

[0051] Characteristic 1: The main rock skeleton is composed of silt-sand porous quartz particles, which account for more than 45% of the rock volume. Among them, the silt-grade particle size is 4-62.5μm, and the silt-grade porous quartz particles account for 30-45% of the rock volume. The sand-grade particle size is greater than 62.5μm and does not exceed 400μm, and the sand-grade porous quartz particles account for 0-15% of the rock volume.

[0052] Feature 2: The auxiliary rock framework is formed by aggregates of mud-grade porous quartz particles, which account for more than 25% of the rock volume and are distributed between the main rock frameworks. The mud-grade particles are less than 4 μm in size.

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

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

[0055] After analyzing and characterizing the petrological characteristics of siliceous shale, the inventors of the present invention found that siliceous shale formed by deep-water traction flow deposition has high exploration and development potential. If the siliceous shale has characteristic 1 (a main rock skeleton 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 skeleton formed by aggregates of mud-grade porous quartz particles with a particle size of less than 4 μm distributed between the main rock skeletons, accounting for more than 25% of the rock volume), and characteristic 3 (porous organic matter and non-porous organic matter distributed between the rock skeletons, including the main rock skeleton and the auxiliary rock skeleton, accounting for 8-15% of the rock volume), then this siliceous shale is a lithification product of siliceous mud formed by deep-water traction flow deposition. Therefore, characteristics 1, 2 and 3 can effectively characterize it as deep-water traction flow deposition.

[0056] Furthermore, obtaining the target siliceous shale includes:

[0057] Conduct whole-rock analysis and total organic carbon testing on the siliceous shale to be tested to determine the mass content of quartz, clay, and total organic carbon in the siliceous shale to be tested;

[0058] If the quartz mass content of the siliceous shale to be tested is higher than 90%, the clay mass content is no more than 1%, and the total organic carbon mass content is higher than 4%, the siliceous shale to be tested is taken as the target siliceous shale.

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

[0060] using a target siliceous shale core to produce an argon ion polished sheet of the target siliceous shale;

[0061] Collect MAPS rock image data of argon ion polished slices of target siliceous shale;

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

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

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

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

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

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

[0068] Furthermore, collecting a MAPS rock image data volume of an argon ion polished wafer of a target siliceous shale includes: selecting an area with a length and a width not exceeding 400 μm on a polished surface of the argon ion polished wafer of the target siliceous shale, and collecting the MAPS rock image data volume;

[0069] Furthermore, during the acquisition of the MAPS rock image data volume 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, thereby ensuring that all phenomena observed in the acquired MAPS rock image data volume are merely magnified natural phenomena;

[0070] Furthermore, based on the MAPS rock image data volume of the argon ion polished slice of the target siliceous shale, in the process of observing whether the target siliceous shale has features 1, 2 and 3, an image editor (such as the offline image editor ATLAS TM BROWSER-BASEDVIEWER) is used to observe the MAPS rock image data on a computer.

[0071] Furthermore, in feature 1, the main rock skeleton dominated by silt-sand porous quartz particles further includes at least one of carbonate mineral particles (such as calcite and / or dolomite), pyrite, fecal pellets, and silt-grade non-porous quartz particles;

[0072] Furthermore, the dissolved pores of carbonate mineral particles in the main framework of the rock (such as dissolved pores of calcite and / or dolomite) are filled with mud-grade porous quartz particles and / or mud-grade porous quartz particle aggregates.

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

[0074] Furthermore, in feature 3, the organic matter includes honeycomb-rich nanopore organic matter and non-porous organic matter.

[0075] Furthermore, the method also includes: if the target siliceous shale has characteristics 1, 2 and 3, determining that the silt-sand porous quartz particles in the main rock skeleton of the target siliceous shale are siliceous bioclastic beaches formed by deep-water traction flow deposition.

[0076] Furthermore, the method also includes: if the target siliceous shale has characteristics 1, 2 and 3, then determining that the mud-grade porous quartz aggregates in the rock auxiliary skeleton of the target siliceous shale are mud-grade siliceous microbial mats formed by deep-water traction flow deposition on the basis of siliceous bioclastic beach.

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

[0078] Furthermore, the method also includes: if the target siliceous shale has characteristics 1, 2, and 3, determining that the silt-grade non-porous quartz particles with a clay film on the particle surface are residual terrigenous quartz fragments of seabed sediments modified by deep-water traction currents.

[0079] The rock skeleton of siliceous shale is composed of quartz grains, which have strong resistance to compaction. The overlying strata have limited compaction of organic matter. The organic matter distributed between the rock skeletons, including the primary and secondary rock skeletons, is pyroasphalt. Organic matter rich in honeycomb nanopores is pyroasphalted solid asphalt, while non-porous organic matter is pyroasphalted petroleum. The skeletons of siliceous organisms are ultimately transformed into porous quartz with enlarged edges of secondary quartz through dissolution and precipitation reactions. The silt-sand porous quartz grains in the primary rock skeleton are fossils of silt-sand siliceous microorganisms. The silt-sand non-porous quartz with a clay film on its surface is terrigenous quartz debris. The mud-grade porous quartz grains filling carbonate mineral pores and adhering to the surfaces of fecal pellets, as well as aggregates of mud-grade porous quartz grains in the secondary rock skeleton, are aggregates of mud-grade siliceous microbial fossils. If siliceous shale has a main rock skeleton dominated by silt-sand-grade porous quartz particles, an auxiliary rock skeleton formed by aggregates of mud-grade porous quartz particles distributed between the main rock skeletons, and porous organic matter and non-porous organic matter distributed between the rock skeletons including the main rock skeleton and the auxiliary rock skeleton, this siliceous shale is considered to be the lithification product of siliceous mud formed by deep-water traction flow deposition.

[0080] The sedimentation process of deepwater traction currents can be divided into three stages: the first, the formation of silt-sand siliceous bioclastic beaches; the second, the formation of mud-grade siliceous microbial mats; and the third, the formation of carbohydrate-rich microbial mats. Deepwater traction currents have the ability to erode and transport mud-grade particles, which manifests itself in two ways: first, they erode muddy sediments, carrying away mud-grade particles such as clay and sedimentary organic matter, while retaining silt-grade particles such as terrigenous quartz clasts, marine calcite clasts, marine dolomite clasts, and pyrite. Second, they transport mud-grade particles such as clay and organic matter that have settled from the upper water column to the deep water, where they deposit abundant silt-sand siliceous biomass (siliceous bioclastics) onto the seafloor. Small amounts of silt-grade calcite, pyrite, and fecal pellets are also possible. On the seafloor, silty-sand siliceous bioclastics mix with small amounts of silty-terrigenous quartz clasts, marine carbonate mineral clasts, pyrite, and fecal pellets, forming siliceous bioclastic beaches, the first stage of deepwater traction current sedimentation. Water flowing over these bioclastic beaches provides abundant oxygen and nutrients, which provide the material basis for the formation of mud-grade siliceous microbial mats. These microbes inhabit the silty-terrigenous quartz clasts, silty-sand siliceous bioclastics, and fecal pellets, which have residual clay on their surfaces, providing protection from erosion. Deepwater traction currents, active at depths greater than the CCD, lead to intense dissolution of calcite and dolomite, and the pores are occupied by mud-grade siliceous microbes. Mud-grade siliceous microbial mats form during the second stage of deepwater traction current sedimentation. As mud-grade siliceous microbial mats develop, water flow slows, oxygen and nutrient supply becomes insufficient, and the mud-grade siliceous microorganisms cease to grow. Instead, carbohydrate-rich microorganisms flourish, forming a carbohydrate-rich microbial mat. This marks the third stage of deepwater traction current sedimentation. At this point, deepwater traction current sedimentation 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. During the shallow burial diagenesis, sedimentary organic matter composed of carbohydrate-rich microbial remains was converted into kerogen through polycondensation. During the early intermediate burial diagenesis, the kerogen was completely converted into pre-oil asphalt. The pre-oil asphalt generated by the kerogen expanded in volume, occupying some of the primary pores. During the late intermediate burial diagenesis, the pre-oil asphalt was converted into solid asphalt and oil, expanding in volume. The primary pores were filled with oil and served as a network for initial oil migration. During the deep burial diagenesis, the solid asphalt and oil were converted into pyroasphalt and generated natural gas. The pyroasphalted solid asphalt developed honeycomb nanopores, while the pyroasphalted oil lacked pores. The honeycomb organic pores of the pyroasphalted solid asphalt stored natural gas, becoming an effective reservoir.

[0082] During the burial diagenesis process, siliceous biological skeletons were transformed into porous quartz with secondary enlargement, silt-sand grade siliceous bioclastics were transformed into silt-sand grade pore-rich quartz, mud-grade siliceous biological skeletons were transformed into mud-grade pore-rich quartz, and mud-grade pore-rich quartz films developed on the surface of fecal pellets. Secondary enlargement fused all the pore-rich quartz to form the skeleton of the rock, effectively protecting the organic matter from being transformed by compaction.

[0083] Example 1:

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

[0085] 1. Perform whole rock analysis and total organic carbon test on the core of the siliceous shale to be tested taken from 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 quartz mass content of the siliceous shale to be tested is higher than 90%, the clay mass content does not exceed 1%, and the total organic carbon mass content is higher than 4%, the siliceous shale to be tested will be regarded as the target siliceous shale.

[0086] In this embodiment, the quartz mass content of the siliceous shale to be tested is higher than 90%, the clay mass content is no more than 1%, and the total organic carbon mass 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. Use the core of the target siliceous shale to make an argon ion polishing sheet of the target siliceous shale; wherein, the argon ion polishing sheet of the target siliceous shale is 2 cm long, 2 cm wide, and 0.5 cm thick; the polishing surface of the argon ion polishing sheet 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 polishing sheet 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 wafer of the target siliceous shale, and collect a MAPS rock image data volume with a resolution of 4 nm; wherein, during the process of collecting the MAPS rock image data volume, the top surface of the argon ion polished wafer of the target siliceous shale is located above the field of view, and the bottom surface of the argon ion polished wafer of the target siliceous shale is located below the field of view, thereby ensuring that all phenomena observed in the collected MAPS rock image data volume are merely magnifications of natural phenomena.

[0089] 4. Use image editor (offline image editor ATLAS TM Observe the collected MAPS rock image data volume on a computer using a BROWSER-BASED VIEWER 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 main rock skeleton is composed of silt-sand porous quartz particles, accounting for more than 45% of the rock volume. The main rock skeleton also includes at least one of carbonate mineral particles (such as calcite and / or dolomite), pyrite, fecal pellets, and silt-grade non-porous quartz particles, and mud-grade porous quartz particles and / or mud-grade porous quartz particle aggregates filling the dissolved pores (such as dissolved pores of calcite and / or dolomite) of the carbonate mineral particles in the main rock skeleton. The silt-grade particle size is 4-62.5 μm, and the silt-grade porous quartz particles account for 30-45% of the rock volume. The sand-grade particle size is greater than 62.5 μm and does not exceed 400 μm, and the sand-grade porous quartz particles account for 0-15% of the rock volume.

[0091] Feature 2: The auxiliary rock framework is composed of aggregates of mud-grade porous quartz particles, accounting for more than 25% of the rock volume, distributed between the main rock framework. The mud-grade porous quartz particles act as a mineral film on the quartz particles and / or fecal pellets in the main rock framework, and this mineral film fuses the auxiliary rock framework with the main rock framework to form the rock framework. The mud-grade particle size is less than 4μm.

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

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

[0094] And if the target siliceous shale has feature 1, feature 2, and feature 3, it is determined that: the silt-sand-grade porous quartz particles in the main rock skeleton of the target siliceous shale are siliceous bioclastic beaches formed by deep-water traction flow deposition, the mud-grade porous quartz aggregates in the auxiliary rock skeleton of the target siliceous shale are mud-grade siliceous microbial mats formed by deep-water traction flow deposition on the basis of siliceous bioclastic beaches, the organic matter distributed between the rock skeletons including the main rock skeleton and the auxiliary rock skeleton comes from the carbohydrate-rich microbial mats formed by deep-water traction flow deposition on the basis of siliceous bioclastic beaches and mud-grade siliceous microbial mats, and the silt-grade non-porous quartz particles with clay film on the particle surface are residual terrigenous quartz fragments of seabed sediments modified by deep-water traction flow.

[0095] In this embodiment, Figure 1 As shown in Figure 2, the main rock skeleton of the target siliceous shale is mainly composed of silt-sand porous quartz particles (e.g. Figure 1 a, b and i) in the above, and including silt-grade non-porous quartz with clay films scattered among silt-sand grade porous quartz grains (e.g. Figure 1 f), silt-grade calcite (such as Figure 1e in), silt-grade pyrite (such as Figure 1 The arrow in a in the figure points to), silt-grade fecal pellets (such as Figure 1 The solid circle in g is marked); the calcite pores in the main framework of the target siliceous shale are filled with mud-grade porous quartz particles (such as Figure 1 The target siliceous shale rock auxiliary skeleton is composed of mud-grade porous quartz grain aggregates (such as Figure 1 The mud-grade porous quartz particles serve as the mineral film of the quartz particles and fecal pellets in the main rock skeleton, which fuses the auxiliary rock skeleton with the main rock skeleton to form the rock skeleton. The inter-rock skeleton organic matter of the target siliceous shale is composed of organic matter rich in honeycomb nanopores (such as Figure 1 c) and non-porous organic matter (e.g. Figure 1 h) composition, the organic matter between the rock skeletons of the target siliceous shale accounts for 12.5% ​​of the rock volume. Analyzing this nested structure of siliceous shale, the main rock skeleton is the lithification product of the silt-sand siliceous bioclastic beach formed in the first stage of the deep-water traction flow deposition process, the auxiliary rock skeleton is the lithification product of the mud-grade siliceous microbial mat formed in the second stage of the deep-water traction flow deposition process, and the organic matter distributed between the rock skeletons is the lithification product of the carbohydrate-rich microbial mat formed in the third stage of the deep-water traction flow deposition process. In the main rock skeleton of the siliceous shale, the silt-sand porous quartz particles (such as Figure 1 a, b and i) are the lithification products of silt-sand grade siliceous bioclastics settled by water bodies, and silt-grade non-porous quartz particles with clay membranes (such as Figure 1 f) in the figure is the silt-grade terrigenous quartz debris left behind by the transformation of the seabed muddy sediments by deep-water traction flow, with clay remaining on its surface, and silt-grade calcite (such as Figure 1 e) and pyrite (such as Figure 1 The arrow in a in the figure points to silt-grade debris particles remaining in the seabed sediments and / or settled in the water body. Silt-grade fecal pellets (such as Figure 1 The solid circle in g in the figure represents the silt-grade particles that settle in the water. In the auxiliary rock skeleton of siliceous shale, mud-grade porous quartz aggregates (such as Figure 1 a, c, d, g, h, i) are the lithification products of mud-grade siliceous microbial mats. The mud-grade siliceous microbial skeletons are transformed into porous quartz, and the secondary quartz on its surface enlarges and fuses with the porous quartz to form aggregates; the calcite-dissolved pores of mud-grade porous quartz (such as Figure 1 The arrow in e in the figure indicates the lithification of mud-grade siliceous microorganisms. The organic matter distributed between the rock skeletons, including the main rock skeleton and the auxiliary rock skeleton, is rich in pores (such as Figure 1 c) is the product of asphaltification of solid asphalt coke, and the organic matter without pores (such as Figure 1h) in the figure represents the products of petroleum coke asphaltification. These are all products of the thermal evolution of carbohydrate-rich microbial mats during burial diagenesis. During the shallow burial diagenesis stage, the carbohydrate-rich microbial mats transform into kerogen. During the early intermediate burial diagenesis stage, the kerogen is completely converted to pre-oil asphalt. During the late intermediate burial diagenesis stage, the pre-oil asphalt is completely converted to solid asphalt and oil, and the siliceous biomass is converted to porous quartz with secondary enlargement. During the deep burial diagenesis stage, both solid asphalt and oil are converted to pyroasphalt. The pyroasphalted solid asphalt is rich in honeycomb nanopores, while the pyroasphalted oil lacks pores.

[0096] In summary, in this example, the target siliceous shale meets all three characteristics: characteristics 1, 2, and 3, indicating deepwater traction flow deposition. Furthermore, the silt-sand porous quartz particles in the primary rock skeleton of the target siliceous shale are siliceous bioclastic banks formed by deepwater traction flow deposition. The mud-grade porous quartz aggregates in the secondary rock skeleton of the target siliceous shale are mud-grade siliceous microbial mats formed by deepwater traction flow deposition on the basis of the siliceous bioclastic banks. The organic matter distributed within the rock skeletons, including the primary and secondary rock skeletons, originates from carbohydrate-rich microbial mats formed by deepwater traction flow deposition on the basis of the siliceous bioclastic banks and mud-grade siliceous microbial mats. The silt-grade, non-porous quartz particles with clay films on their surfaces are residual terrigenous quartz fragments from seafloor sediments remodeled by deepwater traction flow deposition. The area where the target siliceous shale is located (i.e., target siliceous shale area A) is a shale gas sweet spot with high exploration and development potential.

[0097] Example 2

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

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

[0100] like Figure 2 As shown in Figure 2, the main rock skeleton of the target siliceous shale is mainly composed of silt-grade porous quartz particles (e.g. Figure 2 a and d) and includes non-porous quartz with clay films scattered among silt-grade porous quartz grains (e.g. Figure 2 h in), calcite (such as Figure 2 f), dolomite (such as Figure 2 g in), fecal pellets (such as Figure 2 i) in the target siliceous shale rock; the calcite pores in the main framework of the target siliceous shale are filled with mud-grade porous quartz particles (such as Figure 2 The arrows in f in the figure indicate that the pores of dolomite are filled with mud-grade porous quartz particles (such as Figure 2The target siliceous shale rock auxiliary skeleton is composed of mud-grade porous quartz grain aggregates (such as Figure 2 The mud-grade porous quartz particles serve as the mineral film of the quartz particles and fecal pellets in the main rock skeleton, which fuses the auxiliary rock skeleton with the main rock skeleton to form the rock skeleton. The inter-rock skeleton organic matter of the target siliceous shale is composed of organic matter rich in honeycomb nanopores (such as Figure 2 e) and non-porous organic matter (e.g. Figure 2 In the composition c), the organic matter between the rock skeletons of the target siliceous shale accounts for 9.6% of the rock volume. Analyzing this nested structure of siliceous shale, the main rock skeleton is the lithification product of the silt-sand grade siliceous bioclastic beach formed in the first stage of the deep-water traction flow deposition process, the auxiliary rock skeleton is the lithification product of the mud-grade siliceous microbial mat formed in the second stage of the deep-water traction flow deposition process, and the organic matter distributed between the rock skeletons is the lithification product of the carbohydrate-rich microbial mat formed in the third stage of the deep-water traction flow deposition process. In the main rock skeleton of the siliceous shale, the silt-grade porous quartz particles (such as Figure 2 a and d) are the lithification products of silt-grade siliceous bioclastics settled by water bodies, and silt-grade non-porous quartz particles with clay membranes (such as Figure 2 h) in the figure is the silt-grade terrigenous quartz debris left behind by the transformation of the seabed muddy sediments by deep-water traction flow, with clay remaining on its surface, and silt-grade calcite (such as Figure 2 f) in the figure are silt-grade debris particles remaining in seabed sediments and / or settled in water bodies, silt-grade dolomite (such as Figure 2 The g) in the figure is the silt-grade particles left after the dolomite cement in the seabed muddy sediments is transformed by the deep-water traction flow. The silt-grade fecal pellets (such as Figure 2 The i) in the figure is the silt-grade particles that settle in the water. In the auxiliary rock skeleton of siliceous shale, the mud-grade porous quartz aggregates (such as Figure 2 a, b, and e) are the lithification products of mud-grade siliceous microbial mats. The mud-grade siliceous microbial skeletons are transformed into porous quartz, and the secondary quartz on its surface enlarges and fuses with the porous quartz to form aggregates; the calcite-dissolved pores of mud-grade porous quartz (such as Figure 2 The arrow in f in the figure points to) and the dolomite-soluble pore mud-grade pore-rich quartz (such as Figure 2 The arrow in g in the figure indicates the lithification of mud-grade siliceous microorganisms. The organic matter distributed between the rock skeletons, including the main rock skeleton and the auxiliary rock skeleton, is rich in pores (such as Figure 2 e) is the product of asphaltification of solid asphalt coke, and the organic matter without pores (such as Figure 2(c) in the figure represents the products of petroleum coke asphaltification. These are all products of the thermal evolution of carbohydrate-rich microbial mats during burial diagenesis. During the shallow burial diagenesis stage, the carbohydrate-rich microbial mats transform into kerogen. During the early intermediate burial diagenesis stage, the kerogen is completely converted to pre-oil asphalt. During the late intermediate burial diagenesis stage, the pre-oil asphalt is completely converted to solid asphalt and oil, and the siliceous biomass is converted to porous quartz with secondary enlargement. During the deep burial diagenesis stage, both solid asphalt and oil are converted to pyroasphalt. The pyroasphalted solid asphalt is rich in honeycomb nanopores, while the pyroasphalted oil lacks pores.

[0101] In summary, in this example, the target siliceous shale meets all three characteristics: characteristics 1, 2, and 3, indicating deepwater traction flow deposition. Furthermore, the silt-sand porous quartz particles within the primary rock skeleton of the target siliceous shale are siliceous bioclastic banks formed by deepwater traction flow deposition. The mud-grade porous quartz aggregates within the secondary rock skeleton of the target siliceous shale are mud-grade siliceous microbial mats formed by deepwater traction flow deposition on top of the siliceous bioclastic banks. The organic matter distributed within the rock skeletons, including the primary and secondary rock skeletons, originates from carbohydrate-rich microbial mats formed by deepwater traction flow deposition on top of the siliceous bioclastic banks and mud-grade siliceous microbial mats. The silt-grade, non-porous quartz particles with clay films on their surfaces are residual terrigenous quartz fragments from seafloor sediments remodeled by deepwater traction flow deposition. The area where the target siliceous shale is located (i.e., target siliceous shale area B) is a shale gas sweet spot with high exploration and development potential.

[0102] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A method for determining whether siliceous shale is a deepwater traction flow deposit, comprising: Obtaining target siliceous shale; wherein the target siliceous shale has a quartz mass content greater than 90%, a clay mass content not exceeding 1%, and a total organic carbon mass content greater than 4%; Determine whether the target siliceous shale has the following characteristics 1, 2, and 3: Characteristic 1: The main rock skeleton is composed of silt-sand porous quartz particles, which account for more than 45% of the rock volume. Among them, the silt-grade particle size is 4-62.5μm, and the silt-grade porous quartz particles account for 30-45% of the rock volume. The sand-grade particle size is greater than 62.5μm and does not exceed 400μm, and the sand-grade porous quartz particles account for 0-15% of the rock volume. Feature 2: The auxiliary rock framework is formed by aggregates of mud-grade porous quartz particles, which account for more than 25% of the rock volume and are distributed between the main rock frameworks. The mud-grade particle size is less than 4 μm. Feature 3: Porous organic matter and non-porous organic matter accounting for 8-15% of the rock volume distributed between the rock skeletons, including the main rock skeleton and the auxiliary rock skeleton; If the target siliceous shale has characteristics 1, 2, and 3, the target siliceous shale is a deep-water traction flow deposit.

2. The method according to claim 1, wherein Obtaining target siliceous shale, including: Conduct whole-rock analysis and total organic carbon testing on the siliceous shale to be tested to determine the mass content of quartz, clay, and total organic carbon in the siliceous shale to be tested; If the quartz mass content of the siliceous shale to be tested is higher than 90%, the clay mass content is no more than 1%, and the total organic carbon mass content is higher than 4%, the siliceous shale to be tested is taken as the target siliceous shale.

3. The method according to claim 1, wherein Determining whether the target siliceous shale has the following characteristics 1, 2, and 3 includes: using a target siliceous shale core to produce an argon ion polished sheet of the target siliceous shale; Collect MAPS rock image data of argon ion polished slices of target siliceous shale; Based on the MAPS rock image data volume of the argon ion polished slice of the target siliceous shale, observe whether the target siliceous shale has features 1, 2, and 3; Preferably, the resolution of the MAPS rock image data volume of the argon ion polished slice of the target siliceous shale collected is 4-10 nm; Preferably, the length of the target siliceous shale argon ion polishing sheet is 0.8-2 cm, the width of the target siliceous shale argon ion polishing sheet is 0.8-2 cm, and the thickness of the target siliceous shale argon ion polishing sheet is 0.3-0.8 cm; Preferably, the polishing surface of the argon ion polishing sheet of the target siliceous shale is parallel to the cylindrical surface of the target siliceous shale core; Preferably, collecting the MAPS rock image data volume of the argon ion polished wafer of the target siliceous shale comprises: selecting an area with a length and a width not exceeding 400 μm on the polished surface of the argon ion polished wafer of the target siliceous shale, and collecting the MAPS rock image data volume; Preferably, during the process of collecting the MAPS rock image data volume of the argon ion polished sheet of the target siliceous shale, the top surface of the argon ion polished sheet of the target siliceous shale is located above the field of view, and the bottom surface of the argon ion polished sheet of the target siliceous shale is located below the field of view.

4. The method according to claim 1, wherein In feature 1, the main rock skeleton, which is dominated by silt-sand porous quartz particles, also includes at least one of carbonate mineral particles, pyrite, fecal pellets, and silt-size non-porous quartz particles; Preferably, the dissolved pores of the carbonate mineral particles in the main skeleton of the rock are filled with mud-grade porous quartz particles and / or mud-grade porous quartz particle aggregates.

5. The method according to claim 1, wherein The characteristics also include: mud-grade porous quartz grains as mineral films of quartz grains and / or fecal pellets in the main rock framework, which mineral films fuse the auxiliary rock framework with the main rock framework to form the rock framework.

6. The method according to claim 1, wherein In feature 3, organic matter includes honeycomb-rich nanopore organic matter and non-porous organic matter.

7. The method according to claim 1, wherein The method further includes: if the target siliceous shale has features 1, 2, and 3, determining that the silt-sand porous quartz particles in the main rock skeleton of the target siliceous shale are siliceous bioclastic beaches formed by deep-water traction flow deposition.

8. The method according to claim 1, wherein The method also includes: if the target siliceous shale has characteristics 1, 2 and 3, determining that the mud-grade porous quartz aggregates in the rock auxiliary skeleton of the target siliceous shale are mud-grade siliceous microbial mats formed by deep-water traction flow deposition on the basis of siliceous bioclastic beach.

9. The method according to claim 1, wherein The method also includes: if the target siliceous shale has characteristics 1, 2 and 3, determining that the organic matter distributed between the rock skeletons including the main rock skeleton and the auxiliary rock skeleton is derived from the carbohydrate-rich microbial mat formed by deep-water traction flow deposition on the basis of siliceous bioclastic beaches and mud-grade siliceous microbial mats.

10. The method according to claim 1, wherein The method further includes: if the target siliceous shale has features 1, 2, and 3, determining that the silt-grade non-porous quartz particles with clay films on the particle surfaces are residual terrigenous quartz fragments of seabed sediments modified by deep-water traction currents.

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