Oil source rock potential of the lacustrine Jurassic Sim Uuju Formation, West Korea Bay Basin. Part II. Nature of the organic matter and hydrocarbon-generation history

Abstract

The offshore West Korea Bay (WKB) Basin is one of a series of NE-SW rift basins which formed in Korea and eastern China over thin continental crust during the Late Mesozoic and Early Cenozoic, and is characterised by a two-layered structure - a Cenozoic basin is superposed on a pre-Tertiary basin. In Part I of this paper (Massoud et al., 1991), paraffinic oils recovered from Mesozoic and Tertiary sandstone intervals were found to have been generated from different source beds. Also, a probable thick (400-500 m) Jurassic source bed for the Mesozoic oil was geochemically identified in the basinal offshore area of the lacustrine Sim Uuju sequence penetrated by Well 606.

In this Paper, the Authors complete the hydrocarbons survey on the formation by studying the type, amount and maturity of organic matter present, and the history of hydrocarbon generation. They conclude that the Jurassic bed could be considered as a major source for the Mesozoic oil in the WWB Basin, provided that it is of a sufficient extent to have produced large volumes of oil.