Geochemical characteristics of light hydrocarbons in condensate oil from the southwestern Huizhou of the Pearl River Mouth Basin

Abstract

The southwestern Huizhou is an important crude oil enrichment area in the Zhu Ⅰ Depression of the Pearl River Mouth Basin. However, condensate oil and gas have been discovered in the upper memberof Neogene Zhujiang Formation, Paleogene Enping and Wenchang formations, and basement buried hill reservoirs in recent years. In this study, the origin of condensate oil was revealed based on the integration of light hydrocarbons and biomarkers characteristics, which were obtained from GC of whole-oil and GC-MS of saturated fractions.The results, including light hydrocarbon composition, C7 is o-alkanes, naphthene, n-alkanes and other biomarkers indicate that the condensate oil in the H6-1 structure came from the semi-deep to deep lacustrine source rock in Wenchang Formation, which was generated by sapropelic kerogen with relatively high maturity (1.2%-1.3% Ro). In contrast, the condensate oil in the H1-1 structure originated from the shallow lake to peat facies source rock in Enping Formation, the oil was rich in alkanes with low-carbon number which was generated by humic kerogen with relatively low maturity (0.9%-1.1% Ro).The results suggest that the formation of condensate oil in the southwestern Huizhou is both controlled by organic matter type and thermal evolution stage of source rock. This study provides a geochemical basis and support for the evaluation and analysis of condensate oil and gas exploration potential in hydrocarbon-rich depressions.

Keywords

• condensate oil
• light hydrocarbons
• biomarkers
• pearl river mouth basin