Reservoir Characterization of Fluvial Systems, with Examples from Rocky Mountain Region: ABSTRACT

Abstract

Outcrop and subsurface geologic and engineering data have been integrated to evaluate interwell to intrafield-scale stratigraphic heterogeneities and their controls on fluid flow for two Rocky Mountain area reservoir systems. Exposures of the Tertiary Colton Formation in the Sunnyside oil-sand quarry near Price, Utah, illustrate geometries within an exhumed oil reservoir. Flow units were inferred by correlating petrophysical properties (porosity, permeability, relative permeability, capillary pressure, residual saturations) derived from outcrop samples with facies geometries. A similar procedure was employed to map potential flow units along a 2-mi, two-dimensional section of measured surface sections and near-surface cores of the Cretaceous J sandstone near Morrison, Colorado. Lessons from outcrop geometries and petrophysical property distributions were applied to a subsurface study of the Peoria field, Denver basin, in which separate reservoir units correspond to discrete genetic units within the fluvial system. Although near-surface diagenesis affects the absolute values of petrophysical properties, their distribution with respect to facies is consistent from surface to subsurface. Detailed two-dimensional (cross-section) numerical flow simulations were employed to evaluate the importance of various types of heterogeneities identified from the outcrop examples under a variety of flow conditions. Three-dimensional, two-phase simulations and known production history are being used to evaluatemore » subsurface flow-unit analysis. Detailed numerical simulation experiments are also being used in order to evaluate scaling-up procedures for including the effects of important small-scale heterogeneities in a coarse grid.« less