Migration,filling history and geochemical characteristics of Ordovician natural gases in the Tahe Oilfield,Tarim Basin,Northwest China |
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Authors: | Jie Wang Wenhui Liu Jianzhong Qin Keyu Liu Yi Gu |
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Affiliation: | (1) Wuxi Institute of Petroleum Geology, SINOPEC, Wuxi, 214151, China;(2) CSIRO Petroleum, P.O.Box 1130, Bentley, WA, 6102, Australia |
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Abstract: | Ordovician natural gases in the Tahe Oilfield are composed predominantly of hydrocarbon gases dominated by methane with a significant amount of heavy hydrocarbon gas component. The non-hydrocarbon gases include N2, CO2 and minor H2S. The Ordovician natural gases are believed to have originated from the same source rocks, and are composite of gases differing in thermal maturity. Carbon dioxide was derived from thermal metamorphism of Ordovician carbonate rocks. The generation of natural gases involves multiple stages from mature normal oil and condensate-associated gas to thermally cracked gas at the maturity to over-maturity stages. In the main part of the Tahe Oilfield, the Ordovician natural gases appear to be filled in two major phases with a typical petroleum-associated gas from southeast to northwest and from east to west in the early stage; and a thermally cracked gas from east to west in the late stage. At the same time, the oil/gas filling boundary has been primarily established between the two stages. |
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Keywords: | Tahe Oilfield Ordovician system gas migration carbon and hydrogen isotopes genetic feature |
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