During 1941, the Basin district was the most active in Michigan due chiefly to development in the Detroit River (Devonian) formation in the Reed City field in western Osceola County, the Headquarters Traverse (Devonian) field in southern Roscommon County, and extensive development of "Michigan stray" (Mississippian) gas fields in Osceola, Missaukee, and Clare counties.

Ten new oil fields and extensions and six new gas fields were discovered during the year. The Basin district was most important insofar as new developments were concerned. The most important oil discovery in southwestern Michigan was the West Hopkins Traverse (Devonian) field in Allegan County. Actual oil production dropped approximately 17 per cent below 1940.

More gas wells were drilled in 1941 than in any year since 1936. Gas production reached a new maximum with a 6 per cent increase over 1940. The Gulf Refining Company's Bateson No. 1 in the Kawkawlin field in Bay County was drilled to 10,445 feet into the St. Peter (Ordovician) sandstone, but was plugged back to 7,800 feet and kept as a condensate well. Late in December, gas was discovered in Calhoun County in the Traverse (Devonian) limestone, opening an entirely new area to development.

The Panhandle and Eastern Pipeline Company began construction of a gas transmission line approximately 250 miles long. The line will extend from the Michigan Gas transmission line in the southeastern corner of Lenawee County northward to Pleasant Lake in Washtenaw County. One branch will be laid west to Kalamazoo, the other will extend north to Flint and Saginaw. Construction was begun at Saginaw and the line is expected to be completed during 1942.

Geophysical prospecting and core testing were carried on at a brisk rate particularly in the northern and south-central parts of the Southern Peninsula.