--> ABSTRACT: Crude Oil Composition as an Indicator of Source Rock Character and Migration/Accumulation History: An Example from the Pearl River Mouth Basin, South China Sea, by C. R. Robison, L. W. Elrod; #90097 (1990).

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ABSTRACT: Crude Oil Composition as an Indicator of Source Rock Character and Migration/Accumulation History: An Example from the Pearl River Mouth Basin, South China Sea

C. R. Robison, L. W. Elrod

A detailed study of crude oil composition has been used to explain the source and distribution of oils in the Zhu I Depression of the Pearl

River Mouth basin. This approach is useful in studying areas, such as the Zhu I, where samples of possible source rocks are not available and entrapped oils are widely distributed both stratigraphically and areally. The compositional data from both bulk analyses (e.g., API gravity, pour point, and hydrocarbon vs. nonhydrocarbon content) and more detailed analyses (e.g., gas chromatography of saturated hydrocarbons, stable carbon isotope ratios, and biomarker distributions) permitted comparison of oils from different parts of the subbasin and interpretation of their source rock's depositional environment (including type of organic matter input and lithology), source maturity, possible migration paths, and the extent and type of alteration.

Briefly, the results of our work indicate that the Zhu I oils, despite some minor differences in their bulk properties, are very similar. They are waxy and most likely derived from freshwater lacustrine clastic source rocks that not only have a large proportion of algal organic matter but also contain considerable higher plant debris. The data further suggest that Zhu I oils have experienced both significant vertical and horizontal migration. In some instances the trapped oils exhibit signs of thermal as well as biological alteration.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990