Publications

Tunu is a giant gas and condensate field located at the eastern limit of the present Mahakam delta, between the Peciko and Bekapai fields to the south and the Attaka field to the north. The main pay zone in Tunu field is a lower Middle Miocene deltaic succession that occurs between a regional flooding surface at 7.3 My to a regional unconformity at 10.5 My. This deltaic succession is mainly represented by delta front tracts with minor prodelta deposits and, to a lesser extent, by upper delta plain deposits. High sedimentation rates and limited accommodation space at the Tunu field area resulted in periodic local collapse of the edge of the deposited sediments during the Middle Miocene that produced large slump scars parallel to the strike of Tunu anticline. The slump scars are filled by thick massive marine shales that are locally capped by coarser-grained bar or channel sandstone facies. This goal of this study was to provide detailed maps and reconstructions of the slump scar and slump to mitigate the risk for proposed development well locations. Fifteen slump scar bodies have been identified and mapped utilizing 3D seismic data integrated with well control which cut into the top Tunu field reservoirs from the lower part of Stratigraphic Unit (SU) 4 to lower part of SU5. Rapid sedimentation during this period created slope instability at the shelf margin which triggered slump faults that migrated landward in the unconsolidated sediments. Reactivation of tectonic fault systems in the Kutai Basin area may also initiate shelf margin slumps. Detailed 3D geomodeling combined with a regional geologic perspective and more-detailed seismic studies will give a better understanding on slump scar geometry and its impact on reserve potential, well planning, drilling hazards and future step-out potential at Tunu field.