Deepest Production in Rocky Mountain Province: Madden Anticline, Fremont County, Wyoming: ABSTRACT

Abstract

The Monsanto Oil Company 1-5 Bighorn well was drilled at a crestal location on the 6-mi (9.6-km) wide by 20-mi (32.2-km) long Madden anticline. It penetrated all the previously undrilled pre-Cody rocks on the structure before reaching a total depth of 24,877 ft (7,582 m), or 64 ft (20 m) into precambrian granitic rocks, where the bottom-hole temperature was recorded at 425/sup 0/F (218/sup 0/C). The well was completed August 1985 through perforations from 23,758 ft (7285 m) in the lower part of the Mississippian Madison Formation. Gas flowed at 20 MMCFD (566,000 m/sup 3//d) with a flowing tubing pressure of 5800 psi (40 MPa) and a shut-in tubing pressure of 6700 psi (46 MPa). The porosity logs indicated 70 net ft (21.3 m) of porosity, with an average porosity of 8% and a maximum of 14%. The gas composition is 74% methane, 14% CO/sub 2/, 10% H/sub 2/S, and 2% miscellaneous inerts. The productive interval in this well deepened the Rocky Mountain province depth-of-production record by 3400 ft (1034 m). Mechanical logs, gas shows, and drilling parameters indicated additional potentially commercial accumulations of gas in the Upper Cretaceous Frontier sands, the Lower Cretaceous Muddy and Cloverly sands, the Triassicmore » Crow Mountain Sandstone, the Permian Park City Formation, and the Pennsylvanian Tensleep Sandstone. The Frontier through Crow Mountain interval was significantly overpressured and required 17 lb/gal 92037 kg/m/sup 3/) of drilling fluid to maintain balance while drilling. Pressure regressed to a normal gradient near the top of the Paleozoic rocks at approximately 22,700 ft (6919 m). As many as 20 additional wells may be needed to develop the previously untested pre-Cody reservoirs on the Madden anticline.« less