Correlations between geochemical characteristics of source rocks and chemical compositions of crude oils from LD field, block 15-1/05, Cuu Long basin

Abstract

LD field is the second oil discovery on offshore Block 15-1/05, which is located 15 kilometres East-North East of the first discovery (LDN field). The major aim of this study is to evaluate correlations between accumulated hydrocarbons and source rocks of LD structure, in order to verify their potential for generating oil and gas. Therefore, the authors have synthesized and analyzed geochemical and biomarker characteristics, structures, and chemical compositions of crude oils and source rock extracts by gas chromatography–mass spectrometry analysis to interpret hydrocarbon origins of the LD field. Oil samples and source rock hydrocarbon extracts were from LD-1X/LD-1Xst and LD-3X/LD-3Xbis well of the LD field. Based on biomarker distributions, five oil samples as well as nineteen studied extracts from source rocks indicated predominant non-marine algal organic substances as well as contributions of bacterial and higher plant input. Such samples are characterized by the presence of oleananes, high concentration of C27 steranes compared to C29 and C28 steranes, and the presence of 4-methyl C30-steranes low to moderate concentration. Those evidences show that the oil samples are derived from a single source unit.