Geologically-Sensible Modelling of the Spatial Distribution of Permeability in Eolian Deposits: Page Sandstone (Jurassic), Northern Arizona

The spatial arrangement of permeability, one of the fundamental rock properties affecting fluid movement in petroleum reservoirs, is often poorly defined in current industry models. In addition, these models usually downplay many of the geological factors that contribute to the resulting spatial distribution of permeability in the interwell region of a productive interval. In a detailed study of outcrops of eolian (windblown) deposits, more than 10,000 localized permeability measurements were collected using a field minipermeameter on eleven different formations scattered over a six-state region of the midwestern and southwestern United States. Although most of these measurements were concentrated on a Page Sandstone (Jurassic) outcrop in Northern Arizona, the wide variety of sampling techniques applied in this study permitted the development of a generalized geostatistical model of the spatial arrangement of permeability in eolian deposits. Based on the knowledge of how bedding units and stratification types control the permeability distribution, a geologically-based, geostatistical permeability generation scheme was developed. This nested-kriging approach, the outer loop which handles the between-unit trends in permeability and the inner loop which handles the within-unit cross-bedding, accounts for the two geologic volume-scales of permeability variation present in the generalized geostatistical model. In order to establish the accuracy and reliability of the field permeameter used in this study, a careful theoretical and experimental analysis of the device response is made for a variety of field and laboratory applications. Two non-linear deviations associated with gas flow measurements of permeability in porous media are addressed.Petroleum and Geosystems Engineerin