Abstract

Applied organic geochemistry provides the information needed to make an evaluation of source rock potential, including the richness, type and thermal maturity of a source rock. This evaluation will determine the amount of oil and gas available for traps and their quality. In addition, using paleogeography data of the basin at that time, the migration pathways and understanding of entrapment process can be developed, provided enough information is available about reservoir and cap rocks distribution.

The source rock extract and the detailed petroleum chemical composition, including biomarkers and stable isotopes, are used to establish their depositional environment.

West Natuna Basin has several possibilities for source rock candidates. They are Keras Shale, Benua Shale and Barat Shale. From the screening analysis and another conventional evaluations, the only effective source in the study area is the Benua Shale at the P-13 well (10,295-10,895 ft) and the P-15 well (11,138-11,280 ft).

It is evident from the burial history modeling and TTI calculations that hydrocarbon generation started 17.5 million years ago and is still occuring within the Lower Gabus Formation at present day.

Crude oil data from the evaluation shows the depositional environment for the source rock is shallow lacustrine environment with terrestrial input.