World-Class Cores for Fluvial-Deltaic Reservoir Characterization: The Cretaceous Ferron Sandstone of East Central Utah

Michael D. Laine, Thomas C. Chidsey, and J. Thomas Dempster
Utah Geological Survey, Salt Lake City, UT

The Upper Cretaceous Ferron Sandstone of east-central Utah is interpreted as an analog for many of the highly productive, fluvial-deltaic oil and gas reservoirs in the Alaskan North Slope, Gulf Coast, North Sea, and Rocky Mountain regions. These classic rocks are studied for reservoir characterization and permeability structures by petroleum geologists worldwide.

The Ferron Sandstone consists of stacked, transgressive-regressive cycles which are spectacularly displayed, not only in outcrop but in superb cores held at the Utah Core Research Center (UCRC). These deposits accumulated on a deltaic shoreline in a rapidly subsiding portion of the Cretaceous foreland basin recording the influences of fluvial, tidal, and wave energy.

For example, UCRC cores from the Muddy Creek Canyon site display all, or portions of, the complex of facies that make up a typical fluvial-dominated deltaic deposit. Such facies include deposits of: (1) meandering, distributary, and tidal channels; (2) shoreface sequences; and (3) transgressive events, bays, lagoons, and flood basins.

The Muddy Creek cores reveal parasequence sets, defined by flooding surfaces, which make up large-scale reservoir blocks. Marine and/or delta-plain shales between stratigraphic units act as laterally extensive permeability barriers. The dimensions and depositional environments of parasequence sets and the nature of the contacts between parasequences and facies are also well displayed. Bounding surfaces (fluid-flow barriers or baffles), geometries, and depositional environments of these rocks characterize the variability of fluvial-dominated deltaic reservoirs.

The UCRC offers a comprehensive regional collection of well core, cuttings, and oil samples for industry research, workshops, and academic studies.