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Upper Shu’aiba Limestone Reservoirs of Northwest Oman - Geometry, Depositional Facies and Controls on Reservoir Quality
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 77th EAGE Conference and Exhibition 2015, Jun 2015, Volume 2015, p.1 - 5
Abstract
A comprehensive geological and petrophysical dataset from Upper Shu’aiba clinoform bodies in northwest Oman has been used for reservoir characterization, understanding the factors determining reservoir quality, and reservoir rock typing. Lithofacies are grouped into three main facies belts, showing increasing bioclast proportions and size both upwards within each clinoform and towards the basin margin. Most lithofacies are mud-rich, with even the coarsest floatstones and rudstones containing abundant mud matrix between rudist, sclerosponge, and coral clasts. Total porosity is strongly partitioned between the lower and upper hemicycles of each clinoform and also increases towards the basin margin.
Wide porosity variations within each lithofacies reflect control of porosity loss by clay abundance, as reflected in overall inverse correlation between total porosity and bulk-rock alumina content.
Reservoir rock types with meaningful differences in both porosity-permeability transforms and MICP parameters were defined by applying porosity cut-offs at an arbitrary value of 20% to the three main lithofacies. Because both lithofacies and porosity are predictably related to the sedimentological and stratigraphic organization within the clinoform bodies, the RRT thus defined can potentially be implemented for assigning specific ranges of petrophysical properties throughout a reservoir model.