Isotopic geochemical characteristics of two types of carbonate concretions of Chang 7 member in the middle-upper Triassic Yanchang Formation, Ordos Basin, Central China

Zhu, Rixiang; Cui, Jingwei; Luo, Zhendong; Li, Sen; Mao, Zhiguo; Xi, Kelai; Su, Ling

doi:10.1016/j.marpetgeo.2020.104312

Cited by 12 publications

(15 citation statements)

References 40 publications

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“…The unit with higher concentration of Ca and Mg is due to the evolution of organic matter to form acids, and with further evolution, acid decarboxyl group to form hydrocarbons and carbonate ions. These carbonate ions combine with Ca and Mg in water to form calcite and dolomite [9,[33][34][35]. Ca/Mg values can reflect climates humidity due to the varied solubility [36][37][38].…”

Section: Discussionmentioning

confidence: 99%

X-Ray Fluorescence for Laminated Silty Shale Reservoirs in Ordos Basin, China: Implications for Lithology Identification

Cheng

et al. 2022

Geofluids

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Shale lithofacies were an important key for the exploration and development of unconventional oil and gas reservoirs. Previous studies usually use logging data, X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM) to identify shale lithofacies, but these methods cannot accurately and quickly identify geochemical characteristics. Portable X-ray fluorescence (XRF) analysis can identify geochemical characteristics. However, few publications reported the feasibility of XRF identifying lithology. We tested the major elements of this formation systematically by X-ray fluorescence and compared the characteristics of these elements in the silty laminated shales against the calcareous laminated shale and the argillaceous shales. We analyzed the geochemical characteristics of shale using portable XRF and proposed a method to identify argillaceous shale, silty laminated shale, and calcareous laminated shale in the Chang 7 of Well Y1 (in Xiasiwan area). Furthermore, we established a lithoface identification standard. We also found that Ca/Mg of calcareous laminated shale was the highest which indicated a dry depositional environment; in contrast, lowest Ca/Mg of silty laminated shale indicated a humid depositional environment. Argillaceous shale was deposited in a strongly reducing environment because Fe content of argillaceous shale was the highest. Finally, this criterion is tested against the data from the Well Y2, and the results are in good agreement with the thin section analysis and core data.

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Section: Discussionmentioning

confidence: 99%

X-Ray Fluorescence for Laminated Silty Shale Reservoirs in Ordos Basin, China: Implications for Lithology Identification

Cheng

et al. 2022

Geofluids

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“…The instrument utilized for the measurements is a MAT 253 stable isotope mass spectrometer, and the test standard is DZ/T 0184.17‐1997 ‘Determination of carbon and oxygen isotopic composition of carbonate minerals or rocks by phosphoric acid method’. Detailed analytical procedure and approaches are introduced in similar studies elsewhere (Huang et al, 2019; Wu et al, 2017; Zhu et al, 2020).…”

Section: Materials and Analytical Methodsmentioning

confidence: 99%

“…'Determination of carbon and oxygen isotopic composition of carbonate minerals or rocks by phosphoric acid method'. Detailed analytical procedure and approaches are introduced in similar studies elsewhere (Huang et al, 2019;Wu et al, 2017;Zhu et al, 2020).…”

Section: Isotope Testing Of Fracture Fillingsmentioning

confidence: 99%

Characteristics, influencing factors, and prediction of fractures in weathered crust karst reservoirs: A case study of the Ordovician Majiagou Formation in the Daniudi Gas Field, Ordos Basin, China

Xie

Zhou

Zhang³

et al. 2020

Geological Journal

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The study of fractures in karst reservoirs is a hot spot in the field of geosciences. In this article, we conducted a systematic study on the characteristics, influencing factors, and prediction methods of karst reservoir fractures of the Ordovician Majiagou Formation in the Daniudi Gas Field, China. Both weathering and tectonic fractures are mainly developed in the Ma 5 member of the Majiagou Formation. The former is categorized into surface weathering, steep wall tensile and karst collapse fractures, and the latter is made of tensile and shear fractures. The palaeo-temperatures of the fracture filling inclusions range from 90 to 140 C, peaking at 111-120 C, which are derived from oxygen isotopes of −7.9 to −17.5‰, with average −14.1‰ from the same filling inclusions. Integrations of regional tectonic activities, inclusion tests, and stable isotope analysis recognizes four formation periods of fractures since the Caledonian. The factors controlling the development degree of the karst reservoir fractures include lithology, petrophysical properties, rock layer thickness, structural deformation strength, and karst palaeomorphology. The buckling thin plate simulation results show a good positive correlation between the maximum principal stress and tensile fracture density. The same positive correlation is also observed between the shear stress and fracture density. The ancient karst landforms have strongly affected the distribution of weathering fractures. Surficial weathering fractures occur typically in the weathered residual monadnocks, while steep wall tension ruptures in areas near geomorphic steep ridges, and karst collapse fractures in karst residual monadnocks and karst pit areas.

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“…In the Junggar Basin, the maximum δ 13 C value of methanogenic genetic dolomite in the Permian Lucaogou Formation can reach 20‰ [18]. In the Ordos Basin, the carbonate concretion related with methanogenesis arising from bacterial activities in the fermentation zone have δ 13 C values ranged from 10.0‰ to 14.2‰ [47]. Furthermore, the release of CH4 may also promote the prosperity of methanotroph with biomarkers of 13 C-depleted 3β-methylhopanes [48].…”

Section: Microbial Early Diagenesis In the Ostracodsmentioning

confidence: 99%

Early Diagenesis in the Lacustrine Ostracods from the Songliao Basin 91.35 Million Years Ago and Its Geological Implications

Liu

Liu²,

Du³

et al. 2022

Minerals

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Diagenesis is a double-edged sword of geochemical recordings. It makes us always doubt about the representativeness of many geochemical indicators, especially the isotope and mineral related. It also provides a window to explore the biogeochemical processes at the water–rock interface, which are related to the interactions between the hydrosphere, biosphere, and lithosphere. In this study, we identified microbial early diagenesis in lacustrine ostracods from the Songliao Basin 91.35 million years ago by using in situ mineralogical and carbon isotope analytical methods. Our results suggest multiple biological early-diagenesis processes and the formation of a ferric and methane transition zone (FMTZ) in the sulfate-poor pore water, which are conducive to the formation of dolomite and ankerite. These secondary carbonate minerals related to dissimilatory iron reduction and methanogenesis have heavier carbon isotopic compositions than the calcified ostracod shell in the water column and might bring interferences to the geochemical parameters of ostracods.

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Isotopic geochemical characteristics of two types of carbonate concretions of Chang 7 member in the middle-upper Triassic Yanchang Formation, Ordos Basin, Central China

Cited by 12 publications

References 40 publications

X-Ray Fluorescence for Laminated Silty Shale Reservoirs in Ordos Basin, China: Implications for Lithology Identification

X-Ray Fluorescence for Laminated Silty Shale Reservoirs in Ordos Basin, China: Implications for Lithology Identification

Characteristics, influencing factors, and prediction of fractures in weathered crust karst reservoirs: A case study of the Ordovician Majiagou Formation in the Daniudi Gas Field, Ordos Basin, China

Early Diagenesis in the Lacustrine Ostracods from the Songliao Basin 91.35 Million Years Ago and Its Geological Implications

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