Characterising Jurassic Carbonate Successions: Exploring Southern Outcrops of the Hanifa Formation, Saudi Arabia

Abstract

The Jurassic successions in Saudi Arabia are significant as they are both reservoirs and source rocks for the World’s largest hydrocarbon fields. There are seven formations that make up Saudi Arabia's Jurassic system: the Marrat, Dhurma, Tuwaiq Mountain, Hanifa, Jubailah, Arab, and Hith. In central Saudi Arabia, the Jurassic carbonate strata of the Hanifa Formation play a significant role as a hydrocarbon-producing interval. The main objective of this thesis is to provide a high-resolution sedimentology and stratigraphic study of the carbonate rocks of the Hanifa Formation in a series of previously unstudied outcrops, south of the main oil fields. The goal was to evaluate the reservoir characterisation by studying the outcrops using traditional field techniques and novel virtual outcrops (VOs) methods to investigate analogues for reservoir performance on an inter well scale. The Hanifa is interpreted as a being deposited on a shallow carbonate ramp. The studied outcrops lie along a depositional dip profile and allow comparison between systems from proximal upper ramp dominated by corals and stromatoporoid reef facies to a more muddy distal outer ramp. Silica layers are also present within the carbonates the proximal settings, they are linked to periods of allocyclic inputs of silicious material to the basin. There origin and impact on reservoir performance are discussed. Carbonate systems are not straightforward to interpret in the virtual outcrop models (VOMs) and many of the layers look broadly similar, thus petrographic analysis and geochemistry were also incorporated into the study to provide a multiscale view of the reservoir potential. Where all these approaches together achieved excellent outcomes to determine the depositional environment and investigate the reservoir characterisations of the Hanifa formation.