Abstract

The Manusela Formation consists of skeletal and oolitic grainstones deposited in a high energy environment on the northwestern margin of the Australian Plate during the Pleinsbachian to Bathonian (early to mid Jurassic). The limestone represents the final stages of deposition on the margin prior to the onset of continental breakup and sea-floor spreading during the Callovian. Subsequent northward movement of the Australian plate and interaction and collision with the Eurasian and Pacific-Philippine Plates during the late Miocene, resulted in the development of a detached thrust belt and formation of the island of Seram. These tectonic processes and the influx of later diagenetic fluids have had an important effect on the current reservoir character.

Both matrix and fracture porosity are variably preserved in the Manusela and the unit represents an important target for exploration on the island. Testing of this unit was undertaken in the East Nief-1 well, drilled in 1988. Although uncommercial, hydrocarbons were recovered and have encouraged an ongoing exploration programme. Examples of core material, various analyses and petrography are shown here along with wireline log data.