Geochemistry of carbonate-derived oils in the Seram Basin, eastern Indonesia: A new hydrocarbon generation, migration, and preservation model for exploration in fold-thrust belts

Seram Basin, a petroliferous basin in eastern Indonesia, provides a good example to understand the hydrocarbon generation, migration, and preservation on fold-thrust belt settings. It has been widely accepted that crude oils in the area have been derived from a single carbonate source. Some notes should be taken that carbonate rock varies in its organic matter type and composition, so it may expel crude oil with distinctive characters. This study aims to re-interpret the nature and origin of oils in the Seram Basin. Moreover, this study also recognize several post-expulsion hydrocarbon alteration processes that modify crude oil geochemical composition. The orga-nofacies of carbonate probable source rocks in the Seram Basin were determined based on comprehensive biomarker analysis. Chemometric analysis on twenty-six crude oil samples from the Lofin, Nief, Oseil, and Bula Fields was also performed. Our study classifies the carbonate-derived Seram oil further into two families, they are Family A, a group of oil derived from diatom-and-bacterial-rich basinal carbonate, and Family B, a group of oil derived from algae-and-plankton-rich shelf edges carbonate. Different from the previous concept, our study shows that the single-sourced carbonate oil still could be divided into several families. This idea significantly improve the understanding of the petroleum system in the Seram Basin and could be applied to other global fold-thrust belts.