A Predictive Model of Reservoir Continuity in Fluvial Sand Bodies of a Lacustrine Deltaic System, Colton Formation, Utah

MORRIS, THOMAS H., DEAN R. RICHMOND,* and JORGE E. MARINO, Brigham Young University, Provo, UT

The first predictive model of reservoir continuity and heterogeneity of fluvial sandstone bodies within the Paleocene-Eocene Colton Formation of east-central Utah is developed. The Colton is interpreted to be a fluvial dominated lacustrine deltaic sequence that prograded form the southeast into ancient Lake Uinta. Predictability of reservoir continuity is based largely on understanding the nature of impermeable mudstone drapes within multilateral and multivertical sandstone bodies.

Fluvial sandstones are categorized into three systems according to associated facies, channel morphologies, and sandstone/mudstone (S/M) ratios. Suspended load systems dominate the western distal end of Colton exposures and are characterized as follows: meandering to sinusoidal fluvial systems, abundant lateral accretion sets (LAS), and low S/M ratios (< 30). Reservoir characteristics include poor porosity (< 9%) and permeability (< 0.6 md), poor reservoir continuity, small reservoir size, and good potential for development of numerous hydrocarbon traps. Mixed-load systems are typified by abundant sinusoidal and occasional meandering systems, large LAS, and intermediate S/M ratios (25-55). Reservoirs display good porosity (18.5%) and permeability (> 50 md), intermediate re ervoir continuity, intermediate to large reservoir size, and good potential to develop numerous hydrocarbon traps. Bed-load systems are characterized by relatively straight channels, very few point-bar sequences, and high S/M ratios (> 40). Reservoir characteristics display very good porosity (19.6-22.6%) and permeability (133-2657 md), good reservoir continuity, large reservoir size, and less potential to develop hydrocarbon traps.

Improved technology in horizontal drilling may be used to link large noncommunicating multilateral accretion sets.

AAPG Search and Discovery Article #91010©1991 AAPG Rocky Mountain Section Meeting, Billings, Montana, July 28-31, 1991 (2009)