Abstract

Crude oils in the North Sumatra Basin can be generally grouped into two groups based on their material types, i.e. shaly and coaly. These two oil groups show a quite distinct biomarker distributions.

The 30-norhopanes as one of carbonate biomarkers have been proposed recently. Characteristics of the hopane distribution in carbonate or crude oils derived from carbonate source rocks is specific and different to that of shaly or coaly sediment.

Three types of source rocks have been recognised in the North Sumatra Basin namely shale, carbonaceous shale and calcareous shale. n-Alkanes and steranes can only be used to distinguish two source types since the shale and calcareous shale show relatively similar characteristics. Recognition of the three source types can only be observed using the hopane distribution. One crude oil can be correlated to the calcareous shale and two crude oils are correlative to the shale type source rock. Crude oil of coaly shale type is not found during this study.