ABSTRACT: Reservoir characterization of South Tapti field, Bombay Offshore Basin, India

Kaiser, Charles J., Michael D. Van Horn, Laura J. Ullrich, and Steven W. Bailey , Enron Global Exploration & Production Inc, Houston, TX

The South Tapti gas field is located on the crest of a NE-SW anticline in the Surat Depression of the Bombay Offshore Basin. The anticline is a post-Mid Miocene inversion structure overlying a Late Cretaceous rift. Sands of the Early Miocene Mahim Fm. and Late Oligocene Daman Fm. lie within simple four-way closure, with a major fault on the northeast end of the field enhancing closure in the upper sands. Integrated well log, core, biostratigraphic and seismic data indicate that the major reservoirs are hosted by alluvial/fluvial and estuarine sediments within incised valleys and by overlying sheet-like shoreface and deltaic sediments. The 450-m stratigraphic interval containing the 13 pay zones is composed of numerous, erosion based sedimentary sequences. The fluvial and estuarine reservoir sands are predominately quartz arenites with Fe-rich chlorite and siderite cements. Paralic sheet sands are typically very shaley and bioturbated. The major gas-bearing sands usually generate amplitude anomalies that can be mapped in the 3D seismic survey. Commonly the amplitudes dim significantly at the gas/water contact. Amplitude anomaly maps proved useful in characterizing the nature of the sands and in delineating the extent of the reservoirs. The channels that can be imaged in the seismic survey tend to show sediment transport from NE to SW. High resolution MDT data has been used to identify reservoir communication and gas/water contacts, and resolve sand correlations. Early production characteristics of the reservoirs suggest that the small faults within the field only partially restrict fluid flow.

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