Albion-Scipio and Stoney Point Fields, Michigan Basin, U.S.A.

HURLEY, NEIL F., Marathon Oil Company, Littleton, CO, and RON BUDROS, Lithos Exploration, Traverse City, MI

Albion-Scipio and Stoney Point fields have produced more than 125 million barrels of oil from dolomites in the Middle Ordovician, Trenton, and Black River groups. Albion-Scipio is approximately 30 mi (48 km) long and Stoney Point is 10 mi (16 km) long; both fields are about 0.5 mi (0.8 km) wide. Porous reservoir dolomites lie in abrupt lateral contact with adjacent nonproductive regional limestones.

At reservoir depth, the only structural expression is a shallow (up to 60 ft, 18 m) synclinal sag on a regional homoclinal surface. The sag is attributed to Late Silurian-Early Devonian left-lateral strike-slip motion on a reactivated basement fault. Reservoirs apparently formed as stratigraphic traps where dolomite developed above buried faults. Despite relatively poor matrix properties, initial flow tests of several hundred to several thousand BOPD are common. Fractures in core, bit drops, and lost circulation while drilling occurred commonly during field development. Apparently, an interconnected system of fractures, vugs, and caverns provides much of the deliverability and a significant part of the storage in these fields.

Structure maps, fluid contacts, producing gas-oil ratios, bottom-hole pressures, and drilling data from lateral wells provide evidence that these fields can be subdivided into discrete reservoir compartments along their length. Heterogeneities are present at scales ranging from field to interwell to pore-size. Reservoir energy is supplied mainly by gas-cap expansion and gravity drainage. Lateral drilling, which has had limited success to date, holds potential for future field development.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)