Integrated Multidisciplinary Reservoir Characterization of a Deltaic System-1: Architecture and Lithofacies of the Cretaceous-Age Ferron Sandstone, East-Central Utah

R. D. Adams, T. C. Chidsey Jr., M. D. Laine, P. B. Anderson, T. A. Ryer

The Ferron Sandstone Member of the Mancos Shale was deposited in a fluvial-deltaic environment where fluvial-dominated deltas were modified by wave processes. In Ferron deltaic deposits, parasequences may be considered as primary reservoir building blocks because marine and/or delta plain shales act as laterally extensive permeability barriers and commonly separate parasequences. Fluid-flow communication may occur between parasequences where shales are absent due to erosion or non-deposition. Porosity and permeability values, dependent on lithofacies distribution, vary laterally and vertically within a parasequence. Mouth-bar and proximal-delta-front lithofacies are of optimum reservoir quality; distribution of these lithofacies is related to spatial arrangement of parase uences making up the reservoir. Hence, the initial stage in reservoir characterization must be an analysis of the architecture of parasequences and lithofacies within parasequences.

Ferron parasequences are grouped into several parasequence sets that have been previously recognized and correlated throughout east-central Utah. Within a parasequence set, the thickest and most extensive development of delta plain lithofacies is associated with the uppermost parasequence Because of this, fluid-flow communication between parasequences most commonly occurs within a parasequence set and less commonly between parasequence sets.

In the vicinity of Ivie Creek interpreted photomosaics, measured sections, extensive paleocurrent measurements, and core descriptions document stratigraphic relationships between and within parasequence sets, parasequences, and lithofacies. Photomosaic interpretation of two deltaic parasequence sets facilitates delineation of prodelta, delta front, mouth bar, distributary channel, and delta plain lithofacies within individual parasequences. Closely spaced stratigraphic sections document vertical and lateral change within and between lithofacies. Snelgrove and others (1995) present the second stage of reservoir characterization analyses and modeling of petrophysical data collected in conjunction with this geologic study.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995