Abstract: Geological and Petrophysical Characterization of the Ferron Sandstone in Utah, for 3-D Simulation of a Fluvial-Deltaic Reservoir

Thomas C. Chidsey Jr.

Fluvial-deltaic reservoirs contain the largest developed domestic oil reserves, and due to the high degree of reservoir heterogeneity, the largest amount of unrecovered oil of any type of developed reservoirs. The excellent outcrops of the fluvial-deltaic Ferron Sandstone Member of the Cretaceous Mancos Shale make the Coal Cliffs in east-central Utah a world-class area to study reservoir heterogeneity. With funding from the U.S. Department of Energy, a multidisciplinary team is developing a 3-D reservoir model for the Ferron Sandstone.

Our work to date has consisted of: (1) determining geological and petrophysical properties of significant lithofacies, (2) developing new field methods, and (3) interpreting the stratigraphy regionally and within case-study areas. Numerous specific tasks were accomplished. The Ferron Sandstone outcrop belt was obliquely photographed to produce photomosaics for plotting sequence boundaries, major lithofacies, and measured-section locations. Three case-study sites for detailed analysis of the major reservoir types were selected. Numerous sections have been measured, described, and correlated to interpret of the sequence stratigraphy and lithofacies. Lithologic and paleocurrent data were entered into a database to construct statistical models, strip logs, and lithofacies maps. Several ga ma-ray traverses were undertaken primarily for stratigraphic correlation. Numerous core plugs were obtained from various lithofacies for porosity, permeability, and other types of reservoir analyses. Permeability transects were completed across the proximal, middle, and distal portions of the delta-front sandstones. Six core holes were drilled in the central case-study area in a pattern similar to that drilled in an oil field.

The data collected will be integrated into a 3-D representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve management of similar reservoirs worldwide through proper infill and extension drilling strategies, reduction of economic risks, increased recovery, and more reliable reserve calculations.

AAPG Search and Discovery Article #90959©1995 AAPG Rocky Mountain Section Meeting, Reno, Nevada