Reservoir Characteristics Controlled by Depositional Facies and Diagenesis, Devonian System of Michigan Basin

William B. Harrison

Hydrocarbon production from Devonian rocks has been the longest lived and most prolific of any system in the Michigan basin. The Traverse, Dundee, and Lucas Formations have produced nearly all of the 525 million bbl of oil and 150 bcf of gas taken from Devonian rocks since the late 1920s. No detailed or comprehensive study of reservoir characteristics exists for this economically significant sequence of rocks. Detailed analyses of many recently acquired cores and modern wireline log suites from producing reservoirs show that porosity results from primary depositional facies-controlled fabrics, diagenetic alteration fabrics, or both.

Traverse production is concentrated on the western side of the state in patch reef-skeletal grainstone complexes associated with small structural highs or monoclines resulting from Silurian salt-edge dissolution. Some Traverse production in the center of the state is from localized pods of fractured dolomite surrounded by tight micritic limestone. Widespread throughout the east-central basin are fenestral limestones and patch reef complexes of the Dundee Formation that are located atop structural highs. Only minor diagenesis has modified these initially porous sediments. Other Dundee fields are localized or linear pods of fractured dolomite within tight limestone. Dundee fields to the west are combinations of porous facies that have been pervasively dolomitized. Lucas production comes from multiple zones throughout a thick sabhka and basin-centered carbonate and evaporite sequence. Reservoirs occur in intercrystalline or leached moldic porosity in dolomitized carbonates on structural highs or at facies pinch-outs into anhydrite.

This understanding of diagenesis and facies geometries should facilitate future wildcat exploration and enhanced-recovery development in existing fields.

AAPG Search and Discovery Article #91023©1989 AAPG Eastern Section, Sept. 10-13, 1989, Bloomington, Indiana.