Titel: Unraveling sub-seismic interwell-scale facies heterogeneity of Late Jurassic Arab D Member - Clues from outcrop analogue study to develop high-resolution reservoir models

Gaurav Siddharth Gairola, Pankaj Khanna, Ahmad Ihsan Ramdani & Volker Vahrenkamp

King Abdullah University of Science and Technology, Saudi Arabia; King Abdullah University of Science and Technology, Saudi Arabia

Veranstaltung: Abstract GeoUtrecht2020

Datum: 2020

DOI: 10.48380/dggv-4n7x-ht19

Even though the Late Jurassic Arab-D reservoir is the most prolific oil-producing and one of the most studied intervals in the world, it is a major challenge resolving sub-seismic interwell-scale heterogeneities. In the subsurface, in addition to depositional heterogeneities, diagenetic alteration of depositional fabric developed five distinct dolomite types. They vary highly in reservoir properties ranging from flow baffle to Super K further adding complexity to reservoir architecture. Earlier studies focused on petrographical, geochemical and petrophysical analysis to understand genesis and reservoir properties of these dolomites using well log and core data. But very little is known about the geometry, connectivity and inter-well scale heterogeneity of these dolomites. Understanding of these parameters is crucial for development of a realistic subsurface reservoir model and fluid flow heterogeneity scenarios. Outcrop analogues may help in getting insights about these parameters, however, earlier studies reported little about dolomite and dolomite body geometries in outcrops.

The present study introduces a new outcrop analogue for the Arab-D reservoir which is located approximately 100 km North of Riyadh. The outcrop is unique as it contains multiple layers of stratiform dolomites with facies succession similar to subsurface Arab-D reservoir. In addition to the traditional methods (sedimentary log, sample collecting, thin-section petrography), we have also collected drone based photogrammetry (1x1 km2), spectral gamma ray logs (~100 m) and ground penetrating radar (~2 km). The preliminary studies focus on outcrop to subsurface correlation and characterization of dolomite layers to provide insight about subsurface reservoir architecture and associated fluid flow heterogeneities.

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