ABSTRACT: 3-D seismic imaging and interpretation of thin gas sandstone reservoirs using multi-attribute analysis on post-stack and AVO data, Offshore SE Sumatra Indonesia

AVO and post-stack multi-attribute analysis on 300 Km² of 3D pre-stack time migrated seismic data has been successfully used to define the internal character of a gas sandstone reservoir. The reservoir in the Banuwati field comprises the Early Miocene, A and B sandstones of the Upper Gita Member, Talang Akar Formation. Average depth is 5500 ft; channel sandstones range in thickness from 20 to 70 ft and the gas column is 200 ft. A multistory, tectonically-controlled channel system is clearly outlined by the amplitudes computed in a 12 to 30 ms window below the top TAF horizon. Neural network analysis depicts the channel complex more clearly, showing significant detail such as channel and floodplain depositional features. Stratigraphic ray tracing modeling along with AVO and post-stack attribute analysis was conducted in order to delineate individual sandstones. Interpretations of amplitude and isochron maps are consistent with results of neural network seismic facies, matching extensive well data and conventional core description in the Banuwati A-3 well interpreted as a tidally and marine influenced distributary channel. Among the AVO attributes analyzed, the shear wave reflectivity subtracted from the compressional wave reflectivity seems to be the most effective one in discriminating these sandstones. This study has allowed making both an accurate risked reserves estimation and a well location optimization for the Banuwati field.

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