Abstract

Outcrop studies provide high-resolution information about facies architectural controls on the spatial distribution of petrophysical attributes in reservoir analogs. Unit 5 of the Ferron delta system in central Utah, a wave-modified deltaic sandstone, has been selected for detailed analysis as an analog for Gulf Coast deltaic reservoirs. This deltaic unit consists of a meandering distributary system that fed stratified delta-front deposits. Lateral migration, coupled with rising base level, resulted in horizontally and vertically heterogeneous distributary sandstones, in contrast to the delta front, where vertical heterogeneity is dominant and lateral complexity minimal.

Permeability distribution and structure are strongly related to facies architecture and composition, bedding (or stratal) type, and grain size. Although overlap exists in the permeability character of facies and stratal types, they are statistically different. Bounding surfaces separating facies provide the major discontinuities in permeability structure. Variogram analysis indicates correlation at several scales, and largest correlation lengths are 600 ft (183 m) in the distributary-channel sandstones. At the stratal level, horizontal correlation lengths are less than 20 ft (<6 m) and relate to erosional discontinuities and bed size.