The Deerfield oil field, representing the only commercial production from the Trenton formation in Michigan, is centrally located near the western boundary of Monroe County, 35 miles southwest of Detroit. Activity in this field which started during 1920 was renewed in the spring of 1927 and has continued intermittently to the present time.

This field, the northward extension of the "Bowling Green fault" or "drop-off," is on the northern and western edges of a north-plungingstructural nose on the northwestern flank of the Cincinnati arch.

The Trenton formation is encountered at depths ranging from 2,050 to 2,110 feet. The producing zones are of secondarily crystallized dolomite and occur at various depths in the upper 125 feet of the Trenton. A non-productive area on top of the anticline is caused by a greater westward dip of the oil zones than of the Trenton formation.

The productive closure is a 40- to 50-foot "halo" on the north and west flanks of the fold. The productive area is, therefore, approximately 220 acres with a total estimated recovery of 2,500 barrels per acre. This reservoir is of the gas-expansion type with no apparent water drive. The oil is dark green and has a gravity of 42.7° and a sulphur content of 0.17 per cent. Forty producing wells have been drilled into the field and seventeen of these are now on production.

Two tests have been drilled below the Trenton. The deepest test, the Consolidated Development Company's Lamont Bragg B-2, reached the total depth of 3,250 feet. It was estimated that the granite would have been encountered at approximately 3,800 feet.