ABSTRACT: Facies, Cyclicity, and Waterflood Performance: Dundee (Devonian) Reservoir, West Branch Field, Michigan

CURRAN, BRENDAN C., Marathon Oil Company, Midland, TX, and NEIL F. HURLEY,* Marathon Oil Company, Littleton, CO

West Branch field, Michigan, has produced over 12 million barrels (2 million cubic m) of oil from the Dundee and Rogers City limestones (Middle Devonian). The Dundee Limestone, which is roughly 160 ft (49 m) thick, was deposited on a carbonate ramp that dipped gently to the northwest. The reservoir is dominated by hemicyclic, normal-marine, skeletal-peloidal grainstones and packstones with primary porosity. Crinoids are very abundant and comprise nearly 100% of the grains in some intervals.

Coarsening-upward hemicycles, which range in thickness from 2 to 18 ft (0.6 to 5 m) are common throughout the field. In ascending order, idealized hemicycles consist of: (1) skeletal wackestones, (2) peloidal-skeletal packstones, and (3) skeletal-peloidal grainstones with interspersed hardgrounds. Hemicycles are demonstrably thicker in the northwestern (more seaward) part of the field.

Two large-scale waterflood projects exist in this reservoir. Facies and cyclicity have measurably affected the relative success of these projects. A very successful waterflood in the east-central part of the field is characterized by a shallower water, hemicyclic, but relatively homogeneous reservoir section. A less successful flood in the west-central part of the field has thicker cycles and a basal, 15 ft (4 m) thick crinoidal grainstone layer that has preferentially channeled injected water. This porous and permeable crinoidal zone grades into shallower water deposits to the east where it has no effect on the waterflood.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)