Nugget formation reservoir characteristics affecting production in the overthrust belt of southwestern Wyoming : Lindquist, S J J Pet Technol, V35, N8, July 1983, P1355–1365

Abstract

The Jurassic-Triassic age Nugget sandstone of the southwestern Wyoming Overthrust Belt is a texturally heterogeneous reservoir with anisotropic directional properties which have been inherited from the depositional environment, modified by diagenesis, and finally overprinted by tectonism. Predominantly eolian processes deposited crossbedded and horizontally-bedded, very fine-grained to coarse-grained sand in dunes, interdunes and associated environments. Original reservoir quality has been somewhat modified by compaction, cementation, dissolution, clay mineralization, and precipitation of hydrocarbon resins. Low-permeability, gougefilled and carbonate-filled fractures potentially restrict hydrocarbon distribution and affect producibility; whereas discontinuous, open fractures enhance permeability in some intervals. Contrast in permeability between dune and interdune intervals ranges over four to five orders of magnitude. Dune and interdune deposits are locally correlatable with the aid of core, conventional log, and stratigraphic dipmeter data. Stratigraphic correlations can then be utilized to model the lateral and vertical extent of directional properties in the reservoir.