--> Understanding the Role of Fault Juxtaposition to Mitigate Charge and Seal Risk in Central Saudi Arabia

AAPG Middle East Region, Second EAGE/AAPG Hydrocarbon Seals of the Middle East Workshop

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Understanding the Role of Fault Juxtaposition to Mitigate Charge and Seal Risk in Central Saudi Arabia


The Central Arabian Platform represents a prolific hydrocarbon province populated with numerous oil and gas field reservoirs housed within Paleozoic Petroleum Systems. The fluids are of very high quality (Arabian Super Lights) and represent a significant prize in the ongoing exploration in this area. The reservoirs range in age from Ordovician to Permian and are composed mostly of clastic fluvial, aeolian and glacial deposits. The source rock for the system is a Silurian shale characterized as a marine clastic source rock with Type II kerogen (Organofacies B) (Pepper and Corvi, 1995); this interval is responsible for the vast majority of Paleozoic hydrocarbon accumulations within the Kingdom, including the light oils and gases found in this region. The main top seal for the Permian is composed of anhydrites and tight carbonates within the Upper Permian, whereas the Ordovician reservoirs are top sealed by the Silurian source rock. Both reservoir systems are also noted to have lateral fault seal components throughout the area. Significant throws on near vertical faults have resulted in juxtaposing both Permian and Ordovician reservoirs against non-reservoir facies, resulting in lateral sealing components for fault bounded closures. This structural faulting overprint on the relatively low amplitude 4-way closures, has served in creating additional 3-way trap volume in a number of cases, throughout the study area. Faulting in the area is also noted to be an important component in creating charge access routes, from mature Silurian shale source rock into the stratigraphically older Ordovician reservoir units. The current work demonstrates how a combination of maturity modeling, fault throw analysis, and mud gas data have been used to help mitigate charge and seal risk for several exploration targets in the study area.