Combination of inorganic and organic geochemical characteristics to study the causes of carbon isotopic anomaly of natural gas: A case study from the central gas field of the Ordos Basin, China

2021 ◽  
pp. 104310
Author(s):  
Wenxue Han ◽  
Xia Luo ◽  
Shizhen Tao ◽  
Jinzhong Liu
Keyword(s):  
Natural Gas ◽  
Ordos Basin ◽  
Geochemical Characteristics ◽  
Gas Field ◽  
Isotopic Anomaly ◽  
Carbon Isotopic ◽  
The Ordos Basin ◽  
Inorganic And Organic

Geochemical characteristics and reasons for the carbon isotopic reversal of natural gas in the southern Jingbian gas field, Ordos Basin, China

2019 ◽  
Vol 157 (4) ◽  
pp. 527-538 ◽  
Author(s):  
Wenxue Han ◽  
Xiangchun Chang ◽  
Weijiao Ma ◽  
Shizhen Tao ◽  
Jingli Yao ◽  
...  
Keyword(s):  
Natural Gas ◽  
Carbon Isotope ◽  
Ordos Basin ◽  
Thermal Cracking ◽  
Critical Value ◽  
Geochemical Characteristics ◽  
Thermal Maturity ◽  
Gas Field ◽  
Carbon Isotopic ◽  
Rare Phenomenon

AbstractThe carbon isotope value of ethane in the southern part of the Jingbian gas field is lower than that in the northern part, indicating a carbon isotopic reversal in the southern Jingbian gas field (δ13Cmethane > δ13Cethane). Through comparing the geochemical characteristics of gases in the southern and northern parts of the gas field, the reasons for the carbon isotopic reversal in the southern Jingbian gas field were determined to be high thermal maturity and mixing action. When thermal maturity reaches a critical value, the carbon isotope value of ethane becomes relatively more depleted with thermal maturity. Although the carbon isotope value of methane increases with thermal maturity, the extent is relatively smaller. Finally, the rare phenomenon of δ13Cmethane > δ13Cethane occurs. High thermal maturity leads to the secondary thermal cracking of gases. Mixing of the cracked gases and primary gases also leads to carbon isotopic reversal. Both of the above mechanisms share a common premise, which is high thermal maturity.

scholarly journals Geochemical characteristics and genesis of natural gas in the Yan’an gas field, Ordos Basin, China

2016 ◽  
Vol 102 ◽  
pp. 67-76 ◽  
Author(s):  
Ziqi Feng ◽  
Dan Liu ◽  
Shipeng Huang ◽  
Deyu Gong ◽  
Weilong Peng
Keyword(s):  
Natural Gas ◽  
Ordos Basin ◽  
Geochemical Characteristics ◽  
Gas Field

Geochemical characteristics of tight gas and gas-source correlation in the Daniudi gas field, the Ordos Basin, China

2017 ◽  
Vol 79 ◽  
pp. 412-425 ◽  
Author(s):  
Xiaoqi Wu ◽  
Quanyou Liu ◽  
Jianhui Zhu ◽  
Kuang Li ◽  
Guangxiang Liu ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Geochemical Characteristics ◽  
Tight Gas ◽  
Gas Field ◽  
Gas Source ◽  
Source Correlation ◽  
The Ordos Basin

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.

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