Geochemistry and depositional environment of fresh lacustrine source rock: A case study from the Triassic Baijiantan Formation shales in Junggar Basin, northwest China

Gao, Gang; Aderoju, Titi; Yang, Shangru; Tang, Yong; Kong, Yali; He, Wenjun

doi:10.1016/j.orggeochem.2017.08.002

Cited by 28 publications

(13 citation statements)

References 27 publications

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“…The depositional environment has significant effects on the composition of shale with different types of kerogen [45,46,[55][56][57]. In addition, for shales with different kerogen types, they have their own relationships between different compositions [34,[58][59][60].…”

Section: Composition Of the Shale Samples With Type III Kerogen Formementioning

confidence: 99%

Nanostructure Effect on Methane Adsorption Capacity of Shale with Type III Kerogen

et al. 2020

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This study focuses on the nanostructure of shale samples with type III kerogen and its effect on methane adsorption capacity. The composition, pore size distribution, and methane adsorption capacities of 12 shale samples were analyzed by using the high-pressure mercury injection experiment, low-temperature N2/CO2 adsorption experiments, and the isothermal methane adsorption experiment. The results show that the total organic carbon (TOC) content of the 12 shale samples ranges from 0.70% to ~35.84%. In shales with type III kerogen, clay minerals and organic matter tend to be deposited simultaneously. When the TOC content is higher than 10%, the clay minerals in these shale samples contribute more than 70% of the total inorganic matter. The CO2 adsorption experimental results show that micropores in shales with type III kerogen are mainly formed in organic matter. However, mesopores and macropores are significantly affected by the contents of clay minerals and quartz. The methane isothermal capacity experimental results show that the Langmuir volume, indicating the maximum methane adsorption capacity, of all the shale samples is between 0.78 cm3/g and 9.26 cm3/g. Moreover, methane is mainly adsorbed in micropores and developed in organic matter, whereas the influence of mesopores and macropores on the methane adsorption capacity of shale with type III kerogen is small. At different stages, the influencing factors of methane adsorption capacity are different. When the TOC content is <1.4% or >4.5%, the methane adsorption capacity is positively correlated with the TOC content. When the TOC content is in the range of 1.4–4.5%, clay minerals have obviously positive effects on the methane adsorption capacity.

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Section: Composition Of the Shale Samples With Type III Kerogen Formementioning

confidence: 99%

Nanostructure Effect on Methane Adsorption Capacity of Shale with Type III Kerogen

et al. 2020

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“…Gao et al, 2017). On this condition, the C 20 -C 21 -C 23 TT data are strongly controlled by the source instead of depositional environment.…”

mentioning

confidence: 90%

“…Marine-continental transitional facies is represented by the C 20 -C 21 -C 23 TT data from 11 basins in nine countries collected by Zumberge (1987) and Gao et al (2017) (Table 1). The majority of the C 21 /C 20 TT ratios are lower than 1.0, while the C 23 /C 21 TT ratios are mostly greater than 1.0 (Figure 2), showing an abundance pattern of C 20 >C 21 <C 23 TT (e.g., Figure 3D).…”

Section: Marine-continental Transitional Faciesmentioning

confidence: 99%

C20-C21-C23 tricyclic terpanes abundance patterns: Origin and application to depositional environment identification

Wang

Li²,

Li³

et al. 2023

Front. Earth Sci.

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Reconstruction of paleo-depositional environments in a sedimentary basin is often obstructed by the absence of typical environmental indicators in sedimentary rocks. Here, we propose a biomarker method using C20-C21-C23 tricyclic terpanes (TTs) as a tracer, which is simple in analysis but robust to provide reliable and detailed environmental information. Based on the analysis of 271 C20-C21-C23TT data from 32 basins in 18 countries, we observed a relationship between C20-C21-C23TT abundance patterns and depositional environments. This relationship was attributed to the control of depositional environments on the input proportions of plankton and terrigenous plants, which act as two end-member precursors for the TTs in a depositional system. The various mixing proportions between these two end-members result in different C20-C21-C23TT abundance patterns associated with different depositional environments, e.g., C20>C21>C23TT in river-lake transitional, C20<C21<C23TT in marine or saline lacustrine environments, C20<C21>C23TT in freshwater lacustrine and C20>C21<C23TT in marine-continental transitional environments. In addition, the C23/C21TT ratio increases with elevated salinity of depositional water, and the C21/C20TT ratio increases with increasing water depths. Based on these observations, a discrimination diagram using C23/C21TT vs. C21/C20TT was developed for environmental identification. The validity of this C20-C21-C23TT biomarker method is well demonstrated by the rock samples with typical environmental indicators. This method is applicable in a broad spectrum of rocks and in maturities up to 2.4%Ro. Its strength was shown by a case study of a complex depositional system in the East China Sea Basin, which has been strongly affected by eustasy.

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“…The kerogen ternary diagram of organic macerals shows that mixed-type organic matter is dominant in source rock intervals of the Dongying Formation, while quite a small amount of samples indicates the incorporation of sapropelite (Figure 4c). The thermal maturity of source rocks can effectively be determined by R o , T max and production index (PI) (Awan et al, 2021;Gao et al, 2017;Peters, 1986). The R o of source rocks in the Dongying Formation increases with burial depth, indicating thermal maturity increases with depth (Figure 5a).…”

Section: Organic Matter Typementioning

confidence: 99%

Investigation on the thermal maturity, organic matter sources and depositional environment of lacustrine source rocks in the Dongying Formation of the Bozhong Sag, Bohai Bay Basin, China

Li,

Liu,

Chen

et al. 2024

Geological Journal

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The unclear understanding of the source rock characteristics for the Paleogene Dongying Formation in the Bozhong Sag leads to the lack of cognition in oil and gas exploration. This research systematically evaluated the discrepancy in geochemical characteristics of source rock intervals in the Dongying Formation based on detailed analysis using Rock‐Eval pyrolysis, total organic carbon (TOC), vitrinite reflectance (Ro), maceral components, stable carbon isotopes and biomarker parameters. It discusses the organic matter sources, depositional environment, thermal maturity and hydrocarbon generation potential in the source rock intervals of the Dongying Formation. The organic matter abundance in the third member (E3d3) and lower sub‐member of the second member (E3d2L) of the Dongying Formation is higher, with an average TOC of 2.08% and 1.03%, respectively, indicating that these source rock intervals could have good and excellent quality. The source rocks of the Dongying Formation predominately contain exinite maceral group and type II1 and II2 kerogen. The thermal evolution is mainly in the low‐mature and mature stages. The organic matter sources in the Dongying Formation are mainly dominated by mixed origin (the carbon isotope reversal of aromatics also provides a potential explanation). However, the values of 1,2,5−/1,3,6‐trimethylnaphthalene, (1,2,5,6 + 1,2,3,5)‐tetramethylnaphthalene/tetramethylnaphthalenes, methyldibenzofuran/methylphenanthrene (MDBF/MP) and dibenzofuran/phenanthrene (DBF/PHEN) parameters in the E3d3 and some samples in E3d2L decipher relatively smaller values than other source rock intervals, proving the enhancement of the contribution of lower organisms. Moreover, the terrestrial input in the bottom‐up deposition process of the Dongying Formation gradually increases. The depositional environment reveals the Dongying Formation source rocks mainly developed freshwater sulphur‐poor lacustrine facies and shallow lake‐fluvial delta facies in an open clay‐rich sedimentary environment with poor water column stratification, belonging to the typical weak oxidation–reduction depositional conditions. The comprehensive geochemical evaluation concludes that the favourable supply of lower organisms and stable clay‐rich depositional environment in the E3d3 interval of the Dongying Formation are potential explanations for the formation of lacustrine source rocks with high organic matter abundance, intermediate thermal evolution and excellent hydrocarbon generation potential, providing a good foundation for the exploration and development prospects of hydrocarbons.

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Geochemistry and depositional environment of fresh lacustrine source rock: A case study from the Triassic Baijiantan Formation shales in Junggar Basin, northwest China

Cited by 28 publications

References 27 publications

Nanostructure Effect on Methane Adsorption Capacity of Shale with Type III Kerogen

Nanostructure Effect on Methane Adsorption Capacity of Shale with Type III Kerogen

C20-C21-C23 tricyclic terpanes abundance patterns: Origin and application to depositional environment identification

Investigation on the thermal maturity, organic matter sources and depositional environment of lacustrine source rocks in the Dongying Formation of the Bozhong Sag, Bohai Bay Basin, China

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