Geochemical Characteristics of Oil and Source Rock,Origin and Genesis of Oil in Xihu Depression,East China Sea Basin
Su Ao
Chen Honghan
Abstract：There are plenty of oil in Xihu depression of East China Sea basin,however,few scholars pay attention to the origin and genesis of oil.The samples of source rocks and oil were measured by gas chromatography and Fourier transform infrared spectroscopy (FTIR),and the origin of oil and genesis of condensate and high-wax light oil are discussed based on the analysis of geochemical characteristics.The results suggest that coal measure source rocks of the Pinghu Formation are at the mature stage of thermal evolution.Carbonaceous mudstone and coal mainly came from terrestrial organism,with kerogen type Ⅲ. Dark mudstone mainly came from both terrestrial organism and aquatic organism,with kerogen type Ⅱ-Ⅲ.Genetic potential of carbonaceous mudstone and coal is significantly higher than that of mudstone.The crude oil is mainly divided into condensate with low density and wax and high-wax light oil,and light hydrocarbon displays obvious different compositions.Most of the oil is of humic type with some oil being both humic and sapropelic.Oil is at the medium mature stage.Most oil is derived from carbonaceous mudstone and coal in the Pinghu Formation,whereas only a small amount of oil is derived from dark mudstone.Physical properties of condensate and light oil and their difference of light hydrocarbon composition are unrelated with source rocks.Condensate was produced under the evap-oration fractionation effect and from the oil which had been generated from the kerogen at the mature stage.High-wax light oil is resid-ual oil from evaporation fractionation effect,and some oil has experienced mixing.
Keywords：Xihu depressiongeochemistryorigingenesispetroleum geology
Publication Date：2015-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：11( 1072-1082 )