Understanding the Impact of Open-Framework Conglomerates on Water-Oil
Displacements: Victor Interval of the Ivishak Reservoir, Prudhoe Bay Field,
Alaska
The Victor Unit of the Ivishak Formation in the Prudhoe Bay Oilfield is
characterized by high net-to-gross fluvial sandstones and conglomerates. The
highest permeability is found within sets of cross-strata of open-framework
conglomerate (OFC). They are preserved within unit bar deposits and assemblages
of unit bar deposits within compound (braid) bar deposits. They are thief zones
limiting enhanced oil recovery. We incorporate recent research that has
quantified important attributes of their sedimentary architecture within
preserved deposits. We use high-resolution models to demonstrate the
fundamental aspects of their control on oil production rate, water breakthrough
time, and spatial and temporal distribution of residual oil saturation. We
found that when the pressure gradient is oriented perpendicular to the
paleoflow direction, the total oil production and the water breakthrough time
are larger, and remaining oil saturation is smaller, than when it is oriented
parallel to paleoflow. The pressure difference between production and injection
wells does not affect sweep efficiency, although the spatial distribution of
oil remaining in the reservoir critically depends on this value. Oil sweep
efficiency decreases slightly with increase in the proportion of OFC
cross-strata. Whether or not clusters of connected OFC span the domain does not
visibly affect sweep efficiency.Comment: 27 pages including 14 figure
