Historical Trends in Minnelusa Exploration - Powder River Basin, WY

Ralph Specht

The Minnelusa play in the greater Powder River Basin area has been varied and almost episodic in its historical drilling activity. More than 7900 wells have been drilled to Minnelusa-penetrating depths in the Powder River Basin since 1901. Since first production of oil from the Minnelusa Fm in 1948, more than 675 Mmbo have been produced, ranking it as the number one oil-producing formation in the Powder River Basin. Drilling trends suggest that factors including successes, price of oil, technologic developments, intra-company business policies and competition with other plays have had significant influence on Minnelusa drilling activity. Exploration techniques have run the gamut from early state-of-the-play geologic 'dart-throwing' to detailed 3-D seismic applications with sub drilling-spacing-unit infill drilling. It is notable that in the 64 years since first discovery of producible oil, records indicate a 26% success rate for all wells drilled to the Minnelusa regardless of the exploration methodology, operator, or wildcat vs. development status. Of these successful wells, the average initial production rate was 250 bopd. Due to internal reservoir stratigraphy, oil character, and stratigraphic variability, Minnelusa-specific operational practices such minimum interval drillstem testing and accurate borehole monitoring significantly 'up the odds' for success. Some speculate that these averages qualify the Minnelusa as a quasi-resource play that is under-exploited until each drilling-spacing-unit has been tested. For many, however, the Minnelusa remains a play that one 'hates to love' with success seeming frustratingly elusive and confounding at times, but production and economics too good to ignore.

AAPG Search and Discovery Article #90156©2012 AAPG Rocky Mountain Section Meeting, Grand Junction, Colorado, 9-12 September 2012