Most fields in Michigan that have produced from the Devonian Dundee formation were produced at high rates during a boom in the 1930's and 1940's, and were rapidly depleted. In 1995, a consortium of universities and an oil company, with support from the Dept. of Energy, drilled a new well in one of those old fields, the Crystal field. The well was first drilled as a vertical well in order to obtain core and logs, and then sidetracked to a horizontal well to explore potential increased productivity.

In the vertical well, the top of the Dundee was lower than predicted, and the core showed good oil stains. The logs, on the other hand, suggest that the oil in this section is residual oil, having been swept by earlier production. The horizontal well encountered the Dundee at the highest elevation to date in this field, and has produced prolifically over the past two years. Subsequent wells drilled in this field have not been as successful, and some other wells in similar Dundee fields have had mixed success. Detailed data from some of these wells has recently become available, and should shed additional light on the play.

The topography of the Dundee surface appears to be highly irregular, resembling a karstic surface, and evidence of cavern fill was found in the cored well at Crystal field. The targets of current exploration should include “attic” oil found above previous wells into the Dundee, where local heterogeneities have resulted in compartments that have not been tapped by earlier production.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah