Effects of Stratigraphic Heterogeneity on Permeability in Eolian Sandstone Sequence, Page Sandstone, Northern Arizona

Outcrop and core data from the eolian Middle Jurassic Page Sandstone of northern Arizona show that realistic reservoir characterization can be based on stratigraphic architecture. Outcrop displays of differential weathering, coloration, cementation, and seepage reflect stratigraphic control of fluid flow within the sandstone. Measurements of permeability using a field permeameter and conventional analysis yield a five-order-of-magnitude range of values between distinct populations. Extra-erg and/or interdune deposits are least permeable (0.67-1,800 md), followed by wind-ripple strata (900-5,200 md), with grain-flow strata being the most permeable (3,700-12,000 md). Extra-erg and interdune deposits and some extensive bounding surfaces form significant flow barriers and tend to compartmentalize the reservoir. Reservoir characteristics of the dune cross-strata are a function of the types, distributions, and orientations of the internal stratification. Directional-flow properties within the strata are most pronounced within wind-ripple laminae. Recognition of the levels of reservoir heterogeneity is sampling-scale dependent. General models for flow within single sets of cross-strata as well as within eolian sequences can be generated based upon relative permeability between stratigraphic units.