Title: Virtual field trip to Late Jurassic Hanifa Formation of the Central Saudi Arabia

Pankaj Khanna, Ahmad Ihsan Ramdani, Teyyuba Adigozalova, Gaurav Gariola, Volker Vahrenkamp

Ali I. Al-Naimi Petroleum Engineering Research Center, Saudi Arabia

Event: GeoKarlsruhe 2021

Date: 2021

DOI: 10.48380/dggv-kmed-a743

Tuwaiq Mountain Escarpment in the Central Saudi Arabia exposes the Late Jurassic carbonates, which are one of the world’s most prolific oil-producing strata in the subsurface. The outcrops provide a window of opportunity to study the architecture of these strata that is found usually complex due to heterogeneous lateral and vertical facies. These heterogeneities are sub-seismic in scale, thus, the information from outcrops bridge the gap between seismic and core data. This virtual field trip focuses on the Late Jurassic Hanifa Formation outcrops at Wadi Birk, central Saudi Arabia with an objective to highlight and display interwell scale heterogeneities associated with depositional architecture. The Hanifa Fm is one of the major hydrocarbon reservoirs in the subsurface of Saudi Arabia and is also in many respects analogous to the even more prolific overlying Arab D reservoirs.

The virtual field trip will include a 4x4 km2 3D digital outcrop model (DOM). The VRGS (Virtual Geoscience) platform will be used to run this field trip. The participants will be taken to one of the most spectacular exposures of the Hanifa Formation at Wadi Birk in Central Saudi Arabia. Depositional facies (in outcrop and thin section), 3D Digital Outcrop Models, and geophysical (GPR, Seismic) and petrophysical datasets (Spectral Gamma Ray - SGR) will be discussed. The main learning outcome of this field trip is to show reservoir equivalent facies in the outcrops but also provide clues into the intricacies of the stratal architecture. It will be demonstrated that the layered architecture is actually not so layered (as usually observed and published). Depositional cycles will be defined based on geological, geophysical, and petrophysical datasets (measured sections, core, thin section, and SGR). The mapping of the depositional cycles within the 4x4 km2 area at Wadi Birk will aid in demonstrating that vertically and laterally the depocenters (sediment production) were migrating. These depocenters are a product of high sediment production by the buildups (stromatoporoid/coral), and relatively low sediment production or current winnowing in the inter-buildups areas. Further, the variability in the shape and sizes of the stromatoporoid/coral build-ups laterally adds more complexity to the thickness of a depositional cycle and provides clues to environmental dynamics. Uneven topography is healed during the deposition of the next cycle with the areas of higher accommodation availability becoming natural depocenters.

The observations and results will be used as input into high-resolution static reservoir models to address the gap of our understanding in inter-well scale heterogeneities of similar subsurface hydrocarbon reservoirs.

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