Publications

The Belut Formation is believed to be an auspicious reservoir addition due to its scattered hydrocarbon discoveries within Block B, West Natuna Basin. Investigations of its nature have been previously reported but challenges due to the reservoirs' distribution, through their sequential paleo-geographic evolution, still exist. An integrated approach to understand the stratigraphy and depositional controls is performed here, with the goal to better understand the reservoir presence in the Belut Formation. An extensive dataset including well-logs, core samples, palynological reports, and 2D-3D seismic data were then utilized around the Bw Graben System, Gb Subbasin, and Trb Subbasin. Syn-rift tectonostratigraphic stage nomenclatures (rift initiation, rift climax, and late syn-rift) are used to understand the sequential basin; form and fill processes. The evolution of paleogeography system, at each tectonostratigraphic stage, resulted in three essential and favorable reservoir settings. The first setting is derived from a lacustrine delta complex (LD), which is sourced transversely from the footwall highland and widely distributed along the basin; hinge margin. The second setting comes from axial fluvial delta (AFD) and fluvial complex (FC) which are axially sourced from pre-established drainages and characterized by the thicker reservoir with limited lateral dimension due to the axial tectonic confinement. The last setting comes from the alluvial fan (AF) and fan delta (FD) which are transversely sourced from the hanging wall highland where the fan compensation is considered to create a large "tank" as the reservoir. The unique reservoir; geometry and distribution in the Belut Formations are concluded to be mainly controlled by rifting phases and the basin configuration, which in turn control the basin; drainage, sediment routing, and specific depositional environments. Further integration between other petroleum system elements are required to calibrate and assess the future opportunities. In addition. The outcomes of this study are believed to be beneficial as analogues to understanding other lacustrine associated reservoirs in Indonesia; rift basins.