Clay controls on reservoir properties in sandstone of Kuzgun formation and its relevance to hydrocarbon exploration, Adana basin, Southern Turkey

The shallow marine lithofacies of Kuzgun formation represented by porous reservoir facies are predominantly represented by the sandstones of Middle-Upper Miocene age. On the basis of texture and mineralogy, the sandstone formation may be classified into three lithological units as a lithofacies-1, -2, -3. The impervious lithofacies-1 (non-reservoir) sandstone formation is represented by alternating layers of mudstone/sandstone exhibiting bioturbation characteristics. The lithofacies-2 and lithofacies-3 units constitute the main reservoir facies in the sandstones of Kuzgun formation. Their microporosity is associated mostly with clay minerals. Approximately one-half of the outcrop sand samples has excellent reservoir potential based upon petrographic, scanning electron microscopy-energy dispersive spectrometry, porosity, permeability and capillary pressure analysis. Sections of the reservoir containing more poorly sorted, and with smaller grain size and grain coating and pore filling authigenic clays, have experienced less exposure to pore-fluid flow and thus less effective porosity and permeability development has occurred. These differences have led to variations in reservoir characteristics such as porosity, permeability, and pore throat. To date no significant deposits of hydrocarbons have been discovered in this sandstones, although an intensive exploratory work towards this end has been carried out in the Adana Basin. The Bulgurdag stratigraphic trap, the only oil field in the basin produces from Palaezoic sediments (basement) capped by the Karaisali carbonates. According to this study lithofacies-2 sandstones of Kuzgun formation are not suitable as diagenetic trap for hydrocarbon exploration in the Adana Basin. But the lithofacies-3 sandstones of Kuzgun formation is expected to have the highest exploration success. (c) 2005 Elsevier B.V. All rights reserved.