Abstract

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Title:: Comparison of Geochemical Characteristics of Two Kinds of Crude Oils in Huizhou Sag of Pearl River Mouth Basin

Author(s):: WANG Fang; BAO Jian-ping; ZHU Cui-shan; 1. Key Laboratory of Oil and Gas Resource and Exploration Technology of Ministry of Education, Yangtze University, Wuhan 430100, Hubei, China; 2. School of Earth Environment and Water Resources, Yangtze University, Wuhan 430100, Hubei, China

Keywords:: organic geochemistry; crude oil; biomarker; chain alkane; terpane; sterane; Huizhou sag; Pearl River Mouth Basin

Abstract:: Based on the distributions and compositions of various biomarkers from different crude oils in Huizhou sag of Pearl River Mouth Basin, they can be classified into coalderived and lacustrine oil. The coalderived oils from well HZ9-2-1 have the characteristics of higher Pr/Ph value (more than 4.5), abnormally abundant C₂₄tetracyclic terpane, steplike decreasing pattern for C₁₉-C₂₆ tricyclic terpanes, more abundant C₂₉norhopane and C₃₁ homohopane, lower neohopanes in C₂₇-C₃₅ hopanes, and absolutely predominant C₂₉ rearranged and regular steranes in C₂₇-C₂₉ steranes. These features are the main indicators to discriminate coalderived oils from other oils. However, for lacustrine oils, their Pr/Ph values are relatively low (less than 3.0), the abundances of C₂₄tetracyclic terpane and C₂₆ tricyclic terpane are similar, the distribution of C₁₉-C₂₆ tricyclic terpanes is normal with the main peak of C₂₁, neohopanes and rearranged hopanes are moderate, gammacerane index indicating paleosalinity is very low. It is noted that 2-methylhopanes and 4-methylsteranes indicating cyanobacteria and dinoflagellate input are very abundant respectively, and the variation of their relative abundances has a normal correlation, representing a specific ecosystem condition to be suitable for the growth of two kinds of microbes. They have an important role in oilsource correlation.