Shallow Gas Production in the Michigan Basin

William Baxter Harrison
Western Michigan University, Kalamazoo, MI

Shallow gas production is significant from the Michigan Basin. Over 1200 wells have shown commercial production from less than 1000 feet deep and nearly 5200 wells produce gas from less than 1500 feet depth. About 91 percent of the shallow gas in Michigan is produced from the Upper Devonian Antrim Black Shale. Most of the 2.5 TCF of gas produced from the Antrim around the basin's northern margin is biogenic in origin. The Antrim shale in this area has seen low thermal maturation (Ro approximately 0.6). The presence of an extensive natural fracture network is the key to commercial production.

Six other formations in the Michigan Basin have relatively small amounts of historic gas production from shallow depths. Mississippian sandstones of the Michigan Formation, Berea Sandstone, Marshall Sandstone and Parma Sandstone all have small amounts of commercial production. The Michigan Formation "Stray" sandstone has been the most productive, occurring in seven different fields. The largest of these fields, Shaver Field in Gratiot County, produced over 11 BCF of gas before being converted to gas storage.

Middle Devonian carbonates of the Traverse and Dundee Limestones have limited gas production from a few shallow conventional reservoirs, often associated with oil production.

Very limited gas production is also known from the Pennsylvanian Saginaw Formation and the Pleistocene Glacial Drift.

Although the production of shallow gas from the Michigan Basin is dominated by the unconventional Upper Devonian Antrim Shale gas play, there are several other shallow conventional-type plays that should not be overlooked.