Reservoir architecture of the Gharif Formation outcrops in the Southern Huqf area, Sultanate of Oman

Abstract

AbstractThe Gharif Formation was deposited in the early Permian and is one of the major producing oil and gas reservoirs in the Sultanate of Oman. The Upper Gharif Unit crops out at Wadi Gharif, where a detailed outcrop characterization was undertaken. Fluvial channel sandstones, inclined heterolithic stratification (IHS) and floodplain palaeosols are the dominant facies associations. Deposition was in a low to moderate sinuosity multistorey fluvial channel belt with fluctuating water levels, allowing water retention in the channel while mud deposited on the upper portions of the point bar was exposed. Sandstone-body geometries indicate ribbon-like channels flowing in a NW orientation. The channel belt is estimated to be between 150 and 250 m wide and encased in oxidized red palaeosols. The depositional units are stacked from east to west and the scour and erosional surfaces are indicative of cut and fill under relatively low accommodation conditions. The reservoir architecture highlights the presence of potential claystone baffles in the IHS section on the margins of the point bars. Differences in grain size between the coarse-grained channel sandstones and the fine-grained IHS sandstones potentially create a permeability contrast while the inclined surfaces will affect fluid movement for both vertical and lateral flow. A deterministic surface-based model was constructed to access static connectivity of the Gharif fluvial channels.