Lithological and zonal porosity-permeability distributions in the Arab-D reservoir, Uthmaniyah field, Saudi Arabia

Permeability vs. porosity plots for the Arab-D carbonate reservoir show a relatively poor correlation, so permeability estimation still remains an issue for discussion. In this study, we integrated basic core measurements with stratigraphic and petrographic analyses to determine porosity and permeability distributions and to identify the association of high permeability, in Darcy range, with lithology and defined reservoir zones. Carbonate rock types in the Arab-D reservoir have been grouped into three lithofacies: granular, muddy-granular, and muddy. The granular lithofacies is the most porous and permeable, and all permeability measurements in Darcy range are associated with it. The muddy facies is represented by low porosity and permeability values. Porosity and permeability distributions of the muddy-granular facies spread over the two regions representative of the muddy and the granular facies. Porosity and permeability distribution patterns of the Arab-D zones are controlled by both type and the arrangement of different lithologies. Zones made up of granular facies demonstrate uniformly high porosity and permeability distributions and reveal the highest permeability intervals. Zones represented by muddy-granular and muddy facies indicate more heterogeneous and mostly bimodal porosity and permeability distributions.