RESERVOIR CHARACTERIZATION AND EOR POTENTIAL IN MIDDLE DEVONIAN DUNDEE LIMESTONE RESERVOIRS, MICHIGAN BASIN, USA

The Middle Devonian Rogers City Limestone and subjacent Dundee Limestone formations have combined oil production in excess of 375 MMBO since initial discovery in 1928 at Mount Pleasant field in the Michigan Basin, USA. In general, hydrocarbon production occurs in two distinct reservoir types: 1) bottom water drive, fractured hydrothermal dolomite reservoirs in the Rogers City mostly, but not exclusively, located in the west central Michigan basin and 2) gas expansion drive, depositional facies controlled limestone reservoirs of the Dundee mostly located in the east central basin. The main objective of this study is to evaluate the enhanced oil recovery (EOR) potential in Dundee Limestone reservoirs in the Michigan basin.

Five main depositional facies were identified from core studies in six fields. Three of these facies are productive reservoirs including: 1) fenestral peloidal grainstone / packstone formed in restricted marine, peritidal settings, 2) stromatoporoid boundstone, formed in patch reefs, and 3) crinoidal grainstone that originated in open marine, shoal-water environments. The average porosity and permeability of these primary and secondary reservoir facies is: 10%/223.5md; and 7%/131md; 6%/12md, respectively.

Reservoir drive mechanisms, estimated primary recovery efficiency, and reservoir petrophysics suggest that Dundee reservoirs may be prospective EOR targets in the Michigan basin. We have determined that sedimentary lithofacies dominate the geological controls on reservoir properties in Dundee limestone reservoirs and the interpretation of primary depositional facies contributes substantially to the prediction of EOR potential in six large Dundee fields. Specifically, geological reservoir characterization are used to evaluate the EOR potential with respect to reservoir petrophysics and geometry in Dundee oil fields in the Michigan basin.