The mineralogy of the clayey-silty siliceous rocks in the Bazhenov Shale Formation (Upper Jurassic) in the west Siberian Basin, Russia: The role of diagenesis and possible implications for their exploitation as an unconventional hydrocarbon reservoir

Argillites that strongly luminesce under UV radiation were detected in the Bazhenov Shale Formation (BSF) of the West Siberian Basin during routine core examination and found to be persistent over a wide lateral area. The mineralogy and fabric of these luminescent layers were characterized by optical and fluorescence microscopy, SEM, TEM, XRD and IR methods. Optical and fluorescence microscopy showed that the luminescent layers were to a large extent derived from volcanic ash falls and could be described as meta-tuffites, although normal detrital sedimentation continued at the same time. The layers have a thickness of several mm to a maximum of 3-4cm and can be defined as a clay-rich regional horizons. XRD showed that two principal clay minerals were present, namely a kaolinite, possibly with some dickite stacking, (kaolin-rich) and a mixed-layer illite-smectite (I/S) with R1 to R2 ordering similar to that found in K-bentonite. Total organic matter in the luminescent layers is much lower than that in the enclosing BSF clayey-silty siliceous sediments above and below as shown by pyrolytic analyses. Evidence is presented that the luminescent characteristic of the argillites is related to their clay mineralogy, specifically to their content *Revised Manuscript (clean copy) Click here to view linked References 2 of kaolin minerals, although a contribution from nitrogenous organic matter cannot be entirely discounted. In some ways the luminescent argillites can be compared with bentonites associated with ash transformations or with tonsteins in coal beds, which are also derived from volcanic ash falls and contain highly crystalline kaolinite. However, tonsteins originate at or near land surface whereas the argillites were apparently formed in the deep ocean. But just as tonsteins can be used for detailed stratigraphic studies and are valuable in the context of coal exploration, so may the luminescent argillites prove to be significant both stratigraphically and in the search for economic hydrocarbon deposits, bearing in mind that their clay mineralogy may be sensitive to temperature and depth of burial and related to their placement in the oil and gas window.

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“…Table 2. Mineral composition of some non-luminescent lithotypes in Bazhenov Formation in well V-5 (Adapted from Shaldybin et al (2017)). Table 3.…”

Section: Discussionmentioning

confidence: 99%

“…This indicates a high potential for hydrocarbon occurrence that could be explored for oil and gas. The essentially detrital nature of the Bazhenov Shales is evident from thin sections, although the role of diagenesis as a determinant of the overall shale mineralogy is also important as shown by Shaldybin et al (2017).…”

Section: Geological Settingmentioning

confidence: 98%

The nature, origin and significance of luminescent layers in the Bazhenov Shale Formation of West Siberia, Russia

Wilson

Lopushnyak

et al. 2019

Marine and Petroleum Geology

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“…Paleoproductivity refers to the total amount of organic matter fixed per unit area per unit time (Algeo et al, 2011;Pan et al, 2020). Generally speaking, high organic productivity is one of the key factors for the formation of hydrocarbon source rocks (Talbot, 1988;Nelson et al, 1995;Mansour et al, 2020a;Mansour et al, 2020b;Yang et al, 2016;Zhao et al, 2021), and a large number of studies have shown that siliceous plankton in marine source rocks is the main provider of marine primary productivity (De Wever and Baudin, 1996;Chou et al, 2012;Xiang et al, 2013;Shaldybin et al, 2017;Jiang et al, 2019;Zhang et al, 2019), whose content is closely related to the biological reproduction in surface water, and its temporal and spatial distribution can be used to reflect the changing process of paleoproductivity. In recent years, many studies have shown that radiolarians enriched in marine hydrocarbon source rocks can gather together and absorb a lot of symbiotic algae in their bodies by using a large number of pseudopodia, forming a good symbiotic relationship with them (Lyle et al, 1988;Erbacher and Thurow, 1997;Xiang et al, 2013;Khan et al, 2019).…”

Section: Relationship Between Biogenic Silica and Organic Mattermentioning

confidence: 99%

The Origin of Silica of Marine Shale in the Upper Ordovician Wulalike Formation, Northwestern Ordos Basin, North China

Zhang

Huang

et al. 2021

Front. Earth Sci.

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The shale of the Wulalike Formation developed in the northwestern Ordos Basin is considered to be an effective marine hydrocarbon source rock. One of the key factors for successful shale gas exploration in the Wufeng–Longmaxi Formation in the Sichuan Basin is the high content of biogenic silica. However, few people have studied the siliceous origin of the Wulalike shale. In this study, we used petrographic observation and element geochemistry to analyze the origin of silica in the Wulalike shale. The results show that the siliceous minerals are not affected by hydrothermal silica and mainly consist of biogenic and detrital silica. A large number of siliceous organisms, such as sponge spicules, radiolarians, and algae, are found under the microscope. It has been demonstrated that total organic carbon has a positive correlation with biogenic silica and a negative correlation with detrital silica, and biogenic silica is one of the effective indicators of paleoproductivity. Therefore, the enrichment of organic matter may be related to paleoproductivity. Through the calculation of element logging data in well A, it is found that biogenic silica is mainly distributed in the bottom of the Wulalike Formation, and the content of biogenic silica decreases, while the content of detrital silica increases upward of the Wulalike Formation. Biogenic silica mainly exists in the form of microcrystalline quartz, which can form an interconnected rigid framework to improve the hardness and brittleness of shale. Meanwhile, biogenic microcrystalline quartz can protect organic pores from mechanical compaction. Therefore, it may be easier to fracture the shale gas at the bottom of the Wulalike Formation in well A.

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Fractal dimension changes of shale pore structure and influence on mechanical properties, relative permeability under different hydration degree

Ning

2023

Environ Earth Sci

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The mineralogy of the clayey-silty siliceous rocks in the Bazhenov Shale Formation (Upper Jurassic) in the west Siberian Basin, Russia: The role of diagenesis and possible implications for their exploitation as an unconventional hydrocarbon reservoir

Cited by 16 publications

References 30 publications

The nature, origin and significance of luminescent layers in the Bazhenov Shale Formation of West Siberia, Russia

The nature, origin and significance of luminescent layers in the Bazhenov Shale Formation of West Siberia, Russia

The Origin of Silica of Marine Shale in the Upper Ordovician Wulalike Formation, Northwestern Ordos Basin, North China

Fractal dimension changes of shale pore structure and influence on mechanical properties, relative permeability under different hydration degree

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