Combined stratigraphic and structural traps of Lower Talang Akar Formation (LTAF) syn-rift deposits create a typical play type in South Sumatra Basin, Indonesia. Three field examples from Jabung Block show pop-up features caused by Plio-Pleistocene tectonics inverting the pre-existing structures. This phenomenon creates the major hydrocarbon traps in the Jabung (Tungkal) sub-basin providing strong targets for further exploration work.
Incorporating existing 3D seismic and wireline log data, a tectono-sedimentary model unique for the each field was generated. All three field geological models are in close proximity to each other within the Betara Complex. Generally, there are three distinct identifiable sub-basin evolution periods. First, a period of horst-graben development controlled by major localized extensional faults that initiated the basin architecture. This episode was followed by rapid to moderate sedimentation controlled by normal faults resulting in deposition of Oligocene Talang Akar alluvial, fluvial and deltaic deposits. Secondly, a period of decreased fault activity along with regional subsidence coinciding with the deposition of post-rifting fine marine Miocene sediments which provided a regional seal for the underlying reservoirs. The third period is marked by regional uplift resulting in wide spread basin inversion over the entire region providing a period of hydrocarbon trapping.
Basin evolution provided complex stratigraphic and structural features and constitutes compartmentalized reservoirs. Complex-multiple gas and oil contacts and variation in CO2 distribution has verified the complexity of the basins geological framework.
Drainage patterns identified from localized paleo-geographic configurations can be used to locate sedimentary styles and trends. When combined with attribute extractions and structural analysis, these patterns can help explorationists develop excellent opportunities for further exploration and development of the area.
The study area is located in PetroChina's Jabung Block in the northern area of the South Sumatra Basin (Figure-1). This northern area has become more actively explored since the discovery of North Geragai and Northeast Betara fields by Santa Fe Energy Resources. Properties currently are held by PetroChina International.