Sedimentary Facies, Depositional Settings and Reservoir Potential of the Owelli Sandstone in Anambra Basin, Southeastern Nigeria

Abstract

The study was undertaken on the Owelli Sandstone for the purpose of evaluation of its lithofacies, depositional settings and reservoir potential. Methodology involves fielding mapping and outcrop logging, lithofacies, paleocurrent and grain size analyses. Seven lithofacies identified were grouped into three lithofacies association; tidal channel, fluvio- Delta and tidal Delta. The rose plots of cross bed azimuths are consistent with the mean vector azimuths, current variance and vector strength, suggesting paleocurrent to be unimodal in the southwesterly directions with dominantly high energy and low variance. Integration of facies association, paleocurrent and grain size data indicated the depositional settings of the Owelli Sandstone to range from marginal to shallow marine. The estimated porosity and permeability range of 45 to 50% and 30.1 to 2301md respectively rated the Owelli Sandstone as good to excellent reservoir. The best reservoirs in the formation is the shallow marine sandstone at Agbogugu area.