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ABSTRACT: Imaging of fluvial reservoir systems in the late Oligocene Talang Akar Formation, Offshore Indonesia

Hull, Robert A., Paul Tonkin, Atmawan Temansya, and Jim Hendricks , YPF - Maxus Southeast Sumatra, Jakarta, Indonesia

Three dimensional seismic images have been acquired by YPF Maxus llc which capture detailed reservoir information in the late Oligocene Talang Akar Formation, offshore southeast Sumatra, Indonesia. Seismic data images across large oil fields, such as Widuri (365 MBO ultimate recoverable), Cinta (270 MBO ultimate recoverable), and the Wanda-Gita fields, have provided new levels of detail, delineating sandbody geometry and reservoir compartmentalization. Production from the YPF Maxus oil fields has amounted to over one billion barrels of oil in the last thirty years. The Talang Akar Formation reservoirs consist of fine- to coarse-grained quartzose clastics that have excellent porosity and permeability. They are of mainly fluvial origin, dominated by braided stream and point bar sand deposits. Higher in the sequence, there is an increasing marine influence. Some of the reservoirs in the Widuri area have been deposited within the upper delta plain and show evidence of tidal reworking. Depositional features, including point bars, abandoned channels and thalwegs, meander loops, cut banks and chute bar deposits, can be visualized using 3D seismic facies analysis.

The 3D seismic data have a frequency content approaching 120 Hertz, which combined with an acquisition spacing of 12.5 ms, allows the imaging of channel and depositional features down to a 5 m vertical resolution and a 10 m horizontal resolution.

High resolution amplitude and amplitude vs. offset data have been successfully employed in a number of 3D surveys to maximize the chance of drilling thick reservoir sections in both exploration and production wells.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia