Abstract

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Title:: Comparisons of Geochemical Characteristics of Crude Oils from Lenghu Structure Zone and Mabei Oilfield in the Northern Qaidam Basin

Author(s):: WANG Zhi-feng; BAO Jian-ping; 1. Key Laboratory of Exploration Technologies for Oil and Gas Resources of Ministry of Education, Yangtze University, Wuhan 430100, Hubei, China; 2. College of Resources and Environment, Yangtze University, Wuhan 430100, Hubei, China

Keywords:: biomarker; Pr/Ph; terpane; sterane; gammacerane; crude oil correlation; Jurassic; Qaidam Basin

Abstract:: The distributions and compositions of biomarkers of 26 samples of crude oils from Lenghu structure zone and Mabei oilfield in the northern Qaidam Basin were analyzed.
The results show that the crude oil from Mabei oilfield is characterized by relatively lower Pr/Ph (<2.0) and higher gammacerane index (0.10~0.20), and rich in C₂₇ steranes relative to C₂₉ steranes together with elevated diasteranes, suggesting that the oil should be derived from Middle Jurassic lacustrine mudstones in adjacent hydrocarbongenerating sag; however, for the crude oil from Lenghu structure zone, the Pr/Ph (2.0~2.5) is relatively higher, and gammacerane index (<0.05) is lower, and C₂₉ steranes surpass C₂₇ homologues. These characteristics might reveal that they are generated by lower Jurassic lacustrine mudstones.