Abstract: The Deep Madden Field, a Super-deep Madison Gas Reservoir, Wind River Basin, Wyoming

MOORE, CLYDE H. and CONNIE HAWKINS

Madison dolomites form the reservoir of a super deep, potential giant sour gas field developed on the Madden Anticline immediately in front of the Owl Creek Thrust along the northern rim of the Wind River Basin, central Wyoming. The Madison reservoir dolomites are presently buried to some 25,000 feet at Madden Field and exhibit porosity in excess of 15%. An equivalent dolomitized Madison sequence is exposed in outcrop only 5 miles to the north on the hanging wall of the Owl Creek thrust at Lysite Mountain. Preliminary comparative stratigraphic, geochemical and petrologic data, between outcrop and available cores and logs at Deep Madden suggests: 1) early, sea level-controlled, evaporite-related dolomitization of the reservoir and outcrop prior to significant burial; 2) both outcrop and deep reservoir dolomites underwent significant recrystallization during a common burial history until their connection was severed during Laramide faulting in the Eocene; 3) While the dolomite reservoir at Madden suffered additional diagenesis during an additional 7-10 thousand feet of burial, the pore systems between outcrop and deep reservoir are remarkably similar.

The two existing deep Madison wells at Madden are on stream, with a third deep Madison well currently drilling. The sequence stratigraphic framework and the diagenetic history of the Madison strongly suggests that outcrops and surface cores of the Madison in the Owl Creek Mountains will be useful in further development and detailed reservoir modeling of the Madden Deep Field, Finally, the effort at Madden has rekindled interest in potential deep Paleozoic carbonate plays throughout the Rockies.

AAPG Search and Discovery Article #90946©1997 AAPG Rocky Mountain Section Meeting, Denver, Colorado