The relationship between dolomitization and organic matter occurrence in Lower Paleozoic carbonate in the Ordos Basin

2000 ◽  
Vol 45 (S1) ◽  
pp. 41-46 ◽  
Author(s):  
Rongfen Jia ◽  
Dehan Liu
Keyword(s):  
Organic Matter ◽  
Ordos Basin ◽  
Lower Paleozoic ◽  
The Ordos Basin ◽  
The Relationship

scholarly journals The petrological characteristics and significance of organic-rich shale in the Chang 7 member of the Yanchang Formation, south margin of the Ordos basin, central China

2019 ◽  
Vol 16 (6) ◽  
pp. 1255-1269 ◽  
Author(s):  
Sen Li ◽  
Ru-Kai Zhu ◽  
Jing-Wei Cui ◽  
Zhong Luo ◽  
Jing-Gang Cui ◽  
...  
Keyword(s):  
Organic Matter ◽  
Positive Impact ◽  
Sedimentary Environment ◽  
Ordos Basin ◽  
Redox Status ◽  
Ash Content ◽  
Central China ◽  
X Ray Diffraction ◽  
The Ordos Basin ◽  
The Relationship

Abstract The organic-rich shale of the Chang 7 member is the most important source rock in the Ordos basin. The sedimentary environment and the controlling factors of organic matter enrichment, however, are still in contention. In this investigation, the Yishicun outcrop, located on the south margin of the Ordos basin, has been considered for the study. X-ray diffraction, polarizing microscopy, field emission scanning electron microscopy and cathodoluminescence (CL) were used to investigate the petrological features of the organic-rich shale. The content of volcanic ash and the diameter of pyrite framboid pseudocrystals were measured to illustrate the relationship between oxygen level, ash content and the enrichment of organic matter. It has been found that the diameter of pyrite framboid pseudocrystals has a strong correlation with the total organic carbon, demonstrating that the redox status degree of the water column has a positive impact on the enrichment of organic matter. Additionally, with an increase in the ash content, the content of organic matter increased at first and then decreased, and reached a maximum when the ash content was about 6%, illustrating that the ash input has a double effect on the enrichment of organic matter.

scholarly journals Genetic types and sources of Lower Paleozoic natural gas in the Daniudi gas field, Ordos Basin, China

2017 ◽  
Vol 35 (2) ◽  
pp. 218-236 ◽  
Author(s):  
Xiaoqi Wu ◽  
Jianhui Zhu ◽  
Chunhua Ni ◽  
Kuang Li ◽  
Yanqing Wang ◽  
...  
Keyword(s):  
Natural Gas ◽  
Ordos Basin ◽  
Source Rocks ◽  
Light Hydrocarbons ◽  
Upper Ordovician ◽  
Gas Field ◽  
Lower Paleozoic ◽  
Upper Carboniferous ◽  
Associated Gas ◽  
The Ordos Basin

The molecular composition, stable carbon and hydrogen isotopes, and light hydrocarbons of the Lower Paleozoic natural gas in the Daniudi gas field in the Ordos Basin were investigated to study the geochemical characteristics. The Lower Paleozoic gas in the Daniudi gas field displays methane contents of 87.41–93.34%, dryness coefficients (C1/C1–5) ranging from 0.886 to 0.978, δ13C1 and δ13C2 values ranging from −40.3 to −36.4‰, with an average of −38.3‰, and from −33.6 to −24.2‰, with an average of −28.4‰, respectively, and δD1 values ranging from −197 to −160‰. The alkane gas generally displays positive carbon and hydrogen isotopic series, and the C7 and C5–7 light hydrocarbons of the Lower Paleozoic gas are dominated by methylcyclohexane and iso-alkanes, respectively. The Lower Paleozoic gas in the Daniudi gas field is mixed from coal-derived and oil-associated gases, similar to that observed in the Jingbian gas field. The oil-associated gas in the Lower Paleozoic gas is secondary oil cracking gas and displays a lower cracking extent than that in the Jingbian gas field. The coal-derived gas in the Lower Paleozoic gas in the Daniudi gas field migrated from the Upper Paleozoic gas through the window area where the iron–aluminum mudstone caprocks in the Upper Carboniferous Benxi Formation were missing. The oil-associated gas in the Lower Paleozoic gas in the Daniudi gas field was probably derived from presalt source rocks in the Lower Ordovician Majiagou Formation rather than the limestone in the Upper Carboniferous Taiyuan Formation. It seems unlikely that the marlstone in the Upper Ordovician Beiguoshan Formation and shale in the Middle Ordovician Pingliang Formation on the western and southwestern margins of the Ordos Basin contributed to the oil-associated gas in the Lower Paleozoic gas in the Daniudi gas field.

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