Abstract

Results obtained from the detailed geochemical analysis of approximately 350 crude oils were used to identify a number of different petroleum systems in the Circum-Pacific Basins of the Far East. The number and type of effective source rocks were determined by using the geochemical characteristics of the crude oils to establish the number of compositionally distinct oil families and by inferring paleoenvironmental conditions of source rock deposition and possible age. Using multivariate statistical techniques and bulk geochemical parameters, isotopic compositions and biomarker distributions, a number of general petroleum systems were identified, differing from each other in terms of age and source paleoenvironment. The oils are separated into three broad groups: terrigenous, lacustrine, and marine. Further detailed examination of each petroleum system, sometimes using more specific geochemical criteria, typically resulted in the establishment of sub-groups of oils according to specific source environment, such as lacustrine fresh versus lacustrine saline. Areas where mixed oils occur are also identified.