scholarly journals Natural Gas Exploration Using Carbon Isotopic Fractionation Effect: A Case Study of Shanxi Formation, Upper Palaeozoic Group in the Center of Ordos Basin, China

2013 ◽  
pp. 18-20 ◽  
Author(s):  
Yun-Feng Zhang
Keyword(s):  
Natural Gas ◽  
Ordos Basin ◽  
Isotopic Fractionation ◽  
Carbon Isotopic ◽  
Fractionation Effect ◽  
Carbon Isotopic Fractionation

scholarly journals Carbon and Hydrogen Isotopic Reversals in Highly Mature Coal-Derived Gases: A Case Study of Paleozoic Gases in the Southern Ordos Basin, China

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-23
Author(s):  
Dan Liu
Keyword(s):  
Source Rock ◽  
Vitrinite Reflectance ◽  
Ordos Basin ◽  
Isotopic Fractionation ◽  
Carbon Isotopic ◽  
Wet Gas ◽  
The Ordos Basin ◽  
Almost All ◽  
Mixing Of Gases

The compositional carbon isotopic seriesδ13C-CH4<δ13C-C2H6<δ13C-C3H8<δ13C-C4H10is common in thermogenic gases. With the exploration of deeper strata, however, isotopic reversals (δ13C-CH4>δ13C-C2H6>δ13C-C3H8) in overmature unconventional shale gases and conventional (coal-derived) gases have been identified. Paleozoic gases in the southern Ordos Basin, China, with partial or complete isotopic reversals, were studied as examples of isotopic fractionation in overmature coal-derived gases. Isotopic compositions of gases of different maturities from the Ordos Basin and shale gases from around the world were compared. Results indicate that carbon isotopic series are related to maturity. Complete isotopic reversal occurs mostly in regions with vitrinite reflectanceRo>2.4%. Where2.4%>Ro>2.0%, almost all gases display partial isotopic reversal, withδ13C-CH4>δ13C-C2H6orδ13C-C2H6>δ13C-C3H8. Carbon isotopic reversal in coal-derived gases is not caused by abiotic origin, the mixing of gases from different types of source rock, abiotic polymerization, wet gas cracking, and other mechanisms that contribute to reversal in shale gases. Based on the unique structure of coaly source rock and the geology of the Ordos Basin, closed-system aromatization-polycondensation reactions are considered the most likely cause of carbon isotopic reversal. During the reactions, isotopically light gases are generated by recombination of previously formed hydrocarbons and residual kerogen-coal. Hydrogen isotopic reversal in the southern Ordos Basin might also be caused by aromatization-polycondensation reactions.

Preliminary Study on Relations between Methane Carbon Isotopic Fractionation and Accumulation of Natural Gas of Lower Paleozoic in the Center of Ordos Basin, China

2013 ◽  
Vol 318 ◽  
pp. 477-481
Author(s):  
Yun Feng Zhang
Keyword(s):  
Thermal Evolution ◽  
Ordos Basin ◽  
Isotopic Fractionation ◽  
Source Rocks ◽  
Gas Migration ◽  
Lower Paleozoic ◽  
Carbon Isotopic ◽  
Physical And Chemical ◽  
Methane Carbon ◽  
Carbon Isotopic Fractionation

Carbon isotopic fractionation frequently occurs during the process of source rocks generating hydrocarbon and its migration through the pore media. Conversely, the recorded isotopic information reflects some physical and chemical characteristics of the rocks, such as porosity, permeability and thermal evolution, etc. In this paper, based on the preliminary analysis of methane carbon isotopic fractionation of Lower Paleozoic in the center of Ordos Basin, China, some reservoir-forming factors like thermal evolution centers, gas pool margins, gas migration directions and the favorable accumulation zones were roughly identified. The results show the hydrocarbon-generating centers located in the Yanan-Jingbian area, the gas migrating direction from southeast to northwest, and the gas reservoir bounded by the lower permeable zone of Wuqi-Suligemiao-Yulin-Jiaxian. Finally, the isotopic results are supported by the otherss special research conclusions of source rock maturity and lithofacies palaeogeography. Therefore, the suggested viewpoints about carbon isotope in this paper have higher reliability.

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