To better understand heterogeneity in petroleum reservoirs, it is useful to create three-dimensional stratigraphic models from outcrops, and then use the derived models as reservoir analogues to further model dynamic reservoirs. We used high-resolution, three-dimensional, digital-outcrop data from ramp carbonates of the Nama Group of Namibia to create static reservoir models.

The Nama Group represents the shallow marine and fluvial, carbonate and siliciclastic sedimentary fill of the Nama foreland basin, which is located in southern Namibia. The basal unit of the Nama Group, the terminal Proterozoic Kuibis Subgroup, represents a northwest-dipping, storm- and wave-dominated carbonate ramp that developed during an overall increase in accommodation space. The lowermost member of the Kuibis Subgroup, the Omkyk Member, represents a shoaling-upward, layer-cake ramp sequence within which microbial bioherms and biostromes developed at several stratigraphic levels. These reefs and associated grainstones are the units that were digitally mapped and modeled.


The Omkyk Member is well exposed in the Zebra River Canyon. Grainstones typically form uniform thick beds with planar and hummocky-cross stratification. Reefs geometries are variable and comprise microbial columns (thrombolites and stromatolites) with mudstone-to-grainstone intercolumn fills. Reefs and grainstones are both interbedded with heterolithic units containing various lithofacies, such as mudstones, microbial laminites, and shales. A 3D stratigraphic model was constructed for the updip part of the carbonate ramp. The model is 2 kilometers wide, 4 kilometers long, and 150 meters thick.