Intact microbial fossils in the Permian Lucaogou Formation oil shale, Junggar Basin, NW China

Xie, Xiaomin; Borjigin, Tenger; Zhang, Qingzhen; Zhang, Zhirong; Qin, Jianzhong; Bian, Lizeng; Volkman, John K.

doi:10.1016/j.coal.2015.05.011

Cited by 42 publications

(18 citation statements)

References 78 publications

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“…In addition, some small spherical structures can be found (Fig. 4j) and have been interpreted as microbial fossils (Xie et al 2015). Comparatively, the Hydrogen Indices of Hongyanchi Formation are very consistent but less than~140 mg HC/g TOC.…”

Section: Junggar Shalesmentioning

confidence: 94%

“…15f) bear much shorter chain length distribution indicating a low wax oil organofacies, whereas Lucaogou shales exhibit an obvious heterogeneity through paraffinic oil to gas condensate via PNA oil organofacies. This is likely related to Lucaogou's various organic matter origins consisting of autochthonous aquatic algal (Carroll and Bohacs 2001), microbial assemblages (Xie et al 2015) and allochthonous land plants input. Phenols (Fig.11), as well as aromaticity and sulphur contents (Fig.…”

Section: High Wax Generative Naturementioning

confidence: 98%

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Upper Permian Junggar and Upper Triassic Ordos lacustrine source rocks in Northwest and Central China: Organic geochemistry, petroleum potential and predicted organofacies

Pan

Horsfield

Zou

et al. 2016

International Journal of Coal Geology

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Section: Junggar Shalesmentioning

confidence: 94%

Section: High Wax Generative Naturementioning

confidence: 98%

Upper Permian Junggar and Upper Triassic Ordos lacustrine source rocks in Northwest and Central China: Organic geochemistry, petroleum potential and predicted organofacies

Pan

Horsfield

Zou

et al. 2016

International Journal of Coal Geology

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“…Descriptions of OM type via light microscopy, particularly reflected light microscopy, has been a standard practice for decades; however, petrographic criteria for the identification of OM types using SEM imaging, especially for the identification of hydrocarbon generating organisms and OM pores, remains poorly defined 5,34 . The difficulty in recognizing organic matter types under microscope seriously hinders the recognition of porous types from nonporous types.…”

Section: Methodsmentioning

confidence: 99%

Characteristics of three organic matter pore types in the Wufeng-Longmaxi Shale of the Sichuan Basin, Southwest China

Nie

Jin

Zhang

2018

Sci Rep

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A consensus has been reached through previous studies that organic matter (OM) pores are crucial to porosity in many shale gas reservoirs; however, their origins and types remain controversial. Here, we report the OM pore types hosted in algae, bitumen, graptolite and other fossil fragments in the Wufeng-Longmaxi Formations of the Sichuan Basin, Southwest China. Algae types mainly include multicellular algae, unicellular algae, etc. The OM pores in multicellular algae usually exhibit irregular, bubble-like, spherical and/or elliptical profiles, and their diameters vary between 300 and 800 nm. The shapes of the OM pores in unicellular algae are either irregular or oval, and the pores are hundreds of nanometres in size. The pores associated with solid bitumen are sporadic, isolated and variable in size, ranging from 500 nm to 3 μm. The pores in the graptolite, sponge spicule, radiolarian and other fossil fragments are much smaller and fewer. The pores may only have developed in the surface of the graptolite and bitumen by filling in the biological cavity of the sponge spicule. These new findings provide stronger evidence that multicellular algae are the main hydrocarbon generating organisms of OM pores development.

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“…Lake basin evolution in Junggar Basin has been well-documented through sedimentological and other studies of the Lucaogou Formation and the underlying-overlying section (Carroll et al, , 1995(Carroll et al, , 2010Carroll andBohacs, 1999, 2001). Carroll (1998) described the Lucaogou Formation as primarily laminated dark gray to black mudstones with no evidence for evaporites, whereas Xie et al (2015) described some evaporitic facies and Carroll et al (1992) noted "possible evaporite molds". An organic petrology study by Tao et al (2012) described the Junggar Lucaogou as being composed of lower silty claystones and dolomitic mudstone with tuffs and oil shale, grading upward into oil shale with thin dolomitic marls, argillaceous dolomite and dolomitic mudstones, some with fish bones, followed by an overlying section of dolomitic mudstone, calcareous mudstone and oil shale.…”

Section: Introductionmentioning

confidence: 99%

Organic petrology and geochemistry of mudrocks from the lacustrine Lucaogou Formation, Santanghu Basin, northwest China: Application to lake basin evolution

Hackley

Fishman

et al. 2016

International Journal of Coal Geology

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Exploration for tight oil in the frontier Santanghu Basin of northwest China has resulted in recent commercial discoveries sourced from the lacustrine Upper Permian Lucaogou Formation, already considered a "world class source rock" in the Junggar Basin to the west. Here we apply an integrated analytical program to carbonate-dominated mudrocks from the Lucaogou Formation in Santanghu Basin to document the nature of organic matter (OM) in the context of an evolving lake system. The organic-rich samples wt.%; n=10) were widely spaced from a ~200 m cored section, interpreted from textural and mineralogical evidence to document transition from a lower under-filled to an overlying balanced-filled lake. Organic matter is dominated by moderate to strongly fluorescent amorphous material with Type I geochemical signature (HI values 510-755; n=10) occurring in a continuum from lamellar stringers, 10-20 µm thick, some ≥1 mm in length (possible microbial mat; preserved only in lower under-filled section) to finely-disseminated amorphous groundmass intimately intermixed with mineral matrix. Biomarkers for methanotrophs and photosynthetic cyanobacteria indicate a © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ complex microbial consortium. A unicellular prasinophyte green alga(?), similar to Tasmanites in marine rocks, is present as discrete flattened discs 50-100 µm in diameter. Type III OM including vitrinite (some fluorescent) and inertinite also is abundant. Solid bitumen, indicating local kerogen conversion, fills voids and occurs throughout the cored section. Vitrinite reflectance values are 0.47-0.58%, consistent with strong OM fluorescence but may be "suppressed". Other proxies, e.g., biomarker parameters, indicate the Lucaogou Formation is in the early oil window at this location. On average, slightly more amorphous OM and telalginite are present in the lower section, consistent with a shallow, stratified, saline environment with low sediment dilution. More inertinite is present in the upper section, indicating greater terrestrial influx and consistent with higher quartz and plagioclase content (dominantly authigenic chalcedony and albite). Laminated mudstones in the upper section indicate anoxia prevented bioturbation from benthic grazing, also indicating stratified water column conditions.A decrease upsection in authigenic dolomite with reciprocal increase of ankerite/siderite is consistent with decreasing salinity, as is an overall decrease in gammacerane index values. These observations suggest evolution from a shallow, stratified evaporative (saline) setting to a deeper, stratified freshwater basin with higher water input during Lucaogou deposition. The evolution from an under-filled to balance-filled lake in Santanghu Basin is similar to Lucaogou deposition in Junggar Basin, suggesting similar tectonic and climatic controls. Paleoclimate interpretations from other researchers in this area suggested an evolution from semi-arid ...

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Intact microbial fossils in the Permian Lucaogou Formation oil shale, Junggar Basin, NW China

Cited by 42 publications

References 78 publications

Upper Permian Junggar and Upper Triassic Ordos lacustrine source rocks in Northwest and Central China: Organic geochemistry, petroleum potential and predicted organofacies

Upper Permian Junggar and Upper Triassic Ordos lacustrine source rocks in Northwest and Central China: Organic geochemistry, petroleum potential and predicted organofacies

Characteristics of three organic matter pore types in the Wufeng-Longmaxi Shale of the Sichuan Basin, Southwest China

Organic petrology and geochemistry of mudrocks from the lacustrine Lucaogou Formation, Santanghu Basin, northwest China: Application to lake basin evolution

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