Publications

The offshore SE Sumatera Production Sharing Contract (PSC) has been one of the prime oil producing areas in Indonesia for the past 40 years. It has produced at cumulative of 800 MMBOE with a capacity of 90,000 BOPD. It is located in the region of the Asri basin which is in part of a series of Cenozoic half grabens, developed on the SE Asia continental margin, occupying a retro-arc setting since the early Neogene times. This paper presents the results of an integrated structure and sequence stratigraphy approach using seismic, well logs, and core data to build a tectonostratigraphic framework and its implication to the Oligocene-Miocene reservoirs. Hydrocarbon prospectivity of the basin is assessed using near field exploration approach. The objectives of this study are to improve present geological understanding of Asri basin (its structural development, regional tectonic, sequence stratigraphy, paleo-depositional environment), and hydrocarbon prospectivity of the basin. The history of the Asri basin is a typical rift-and-sag model. A fourfold division is therefore proposed to explain its tectonic history and stratigraphy. It comprises four main tectonic activities, (1) rift initiation (Eocene), (2) rift climax (Oligocene-Early Miocene), (3) immediate post rift (Middle-Late Miocene) and (4) late-post rift (Pliocene-Pleistocene). The seismic expression of these kinematic units indicates a relation between stages of basin evolution with their respective depositional products. The stratigraphic review covered a wide range of data, from seismic (3rd order), well log (4th order), and core data (5th order). A reasonably good quality of seismic data allows interpretation of seismic Sequence Boundary (SB) and Maximum Flooding Surface (MFS). This was done after a detailed well log analysis incorporated with core data in the interpretation of sequences and depositional environment. At least two potential play concepts in the Oligocene Miocene interval have been identified, the alluvial fan play of tilted horst block, and the basin margin slide mass. It is expected that these plays will open up a new exploration opportunity in the Asri Basin.