Facies Architecture, Paleoenvironment, and Reservoir Quality of the Mid-Cretaceous Wara Member, Arabian Gulf, Offshore Saudi Arabia

Abstract The mid-Cretaceous Wara Member of the Wasia Formation in the Arabian Gulf is composed of fluvio-deltaic to shallow-marine deposits. The aim of this study is, within a sequence stratigraphic framework, to characterize the facies and their distribution in terms of potential reservoir sands using core and wireline log correlations. Detailed core description, well log interpretation and correlation, sequence stratigraphy, depositional model generation, petrographic analysis, and reservoir quality assessment are integrated to gain a more comprehensive understanding of the potential reservoir quality and depositional geometries. Seven high-frequency chronostratigraphic units are identified. They are composed of up to six depositional facies associations, which include fluvial and distributary channels, shoreline and mouth-bar sand, estuarine-lagoonal deposits, delta-plain heterolithics, shelfal marine deposits, and prodelta-offshore marine shales. Lowstand to early-transgressive systems tract, fluvial and distributary channel sands are considered to be potentially the best candidate reservoir units because of the relatively high proportion of medium-grained sand with low diagenetic overprinting. Early transgressive systems tract units of shoreline sands and estuarine-lagoonal deposits are considered to be potential secondary candidates because of more pervasive diagenesis, and their finer-grained character. A west-northwest to east-northeast sand input direction has also been identified and the shoreline orientation improved.