THE MISSISSIPPIAN AND PENNSYLVANIAN ROCKS OF THE DENVER BASIN

The Denver Basin has recently undergone resurgence in drilling for Paleozoic petroleum reservoirs. Recent significant discoveries in the southern part of the basin in the Mississippian and Desmoinesian strata have resulted in an increase understanding of the stratigraphy and structure. The Mississippian contains porous dolomites that are oil productive on structural highs. The source of the oil found in the Mississippian and Pennsylvanian reservoirs is Desmoinesian carbonaceous mudstones that average 11% TOC and are both lacustrine and marine in origin. Within the Cherokee Formation of the Desmoinesian the thin carbonaceous mudstones typically overlie porous carbonates that have great lateral extent. Oil is accumulated within these reservoirs both in structural and stratigraphic traps. The Atoka carbonates tend to be dense and contain little porosity and to date any oil produced this section has been from the carbonaceous mudstones themselves. Presented here will be analysis of the Mississippian and Pennsylvanian rocks demonstrating the internal complexities of the stratigraphy and in some areas complex structures.