oa Depositional Model of a Sharp Base Progradational Estuarine Sandstone: A Case Study of B55M Reservoir — West Patricia Field

The Middle Miocene B5.5M sand is the secondary reservoir in the West Patricia Field. It is currently producing approximately 3000 BOPD from two wells. The B5.5M core from WPA-3 well consists of alternating non-calcareous sandstones and shale drapes, with sharp sand and shale boundary at the top of the sand (Fig. 1). However, the base of the sand is gradational with the underlying shale. The presence of Florschuetzia trilobata and Polysphaeridium sp suggest an estuarine depositional setting. The B5.5M sand log signature displays an alternating fining and coarsening up-wards pattern which is interpreted to represent cut & fill channel and river mouth bar facies respectively (Fig.2). These observations suggest that the B5.5M sand was deposited as stacked estuarine river mouth bars and cut & fill channels, in an overall progradational succession.