ABSTRACT: Sequence Stratigraphy and Reservoir Characterization of the "Muddy Interval", Bell Creek Field, Northern Powder River Basin, Montana

P. S. Molnar, M. L. Porter

A sequence stratigraphic study of the Bell Creek (Muddy) field was undertaken to develop a detailed geologic architecture of the reservoir to optimize waterflood operations and assess future tertiary potential.

Four depositional sequences are present in the Lower Cretaceous (Albian) Muddy interval in Bell Creek field. These sequences developed in response to the fall and subsequent rise of relative sea level in the Western Interior seaway. The sequences are (in ascending order) the shale-prone, offshore-deposited Rozet Sequence; the sand-rich lowstand shoreline Bell Creek Sequence; the Coastal Plain Sequence, a fluvial/estuarine incised valley-fill complex; and the marginal to open-marine Marine Sequence.

Ninety-six detailed core descriptions reveal that lithofacies associations do not occur randomly in these sequences. The five lithofacies observed in the Bell Creek field reservoir have significant differences in properties such as porosity, permeability, and continuity. Historical production and injection data indicate a strong relationship exists between each sequence and well performance. Recognition of the sequence boundaries and prediction of facies within the sequences is essential to effectively manage the reservoir in the Bell Creek field through secondary waterfloor operations and tertiary development.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990