Vertical and Lateral Heterogeneity Assessment of the Early Ordovician Braided Deposits of Risha Member, Saudi Arabia

The Early Ordovician Risha Member of the Saq Formation is one of the important subsurface fluvial hydrocarbon reservoirs in Saudi Arabia. A detailed quantitative and qualitative heterogeneity characterization could enhance the optimal exploitation of these reservoirs. The outcropping strata of the Risha Member in Central Saudi Arabia present an excellent analog for the subsurface reservoirs. Detailed description and sampling of the outcrop were followed by detailed laboratory analyses (petrography, XRF, XRD and petrophysics) to describe the sedimentological heterogeneity. High resolution photographs with 60% overlap were taken to produce 3D photogrammetric model. The Risha Member was subdivided into 62 beds (based on field description) and to 73 beds (after petrographic analysis). The identified lithofacies and sedimentary structures are interpreted as deposits from a mature braided fluvial system with fluctuating energy. The variations in the following elements—channel patterns, sediment distribution, bar formation, channel dynamics, and connectivity—are primarily responsible for the heterogeneity of the Risha Member. The photogrammetric 3D model of the Risha Member is an effective tool to examine and comprehend the fine details of the outcrop. Accurate measurements, improved visualization, and a more thorough and interactive analysis of sedimentary environments and geological processes are all made possible by them.