Stratigraphy and Petrophysics of Gas-Producing Parasequences in the Rollins Sandstone of the Mesaverde Group, Mamm Creek Field, Piceance Basin, Northwest Colorado
Cumella, Stephen P.
Bill Barrett Corp, Denver, CO
The Rollins Sandstone Member of the Iles Formation produces gas from a series of marine shoreface parasequences that pinchout updip along the northwest plunge end of the Divide Creek anticline in the southeast Piceance Basin in northwest Colorado. Very high well density (10- and 20-acre) allows detailed correlation of upwardcoarsening parasequences. In a distal setting, the tops of the parasequences are overlain by marine shale interbeds that thicken in a seaward direction. The shale interbeds pinchout in a landward direction, but in these areas the tops of the parasequences can be identified by a trough cross-stratified, low gamma-ray upper shoreface sandstone overlain by a burrowed, higher gamma-ray lower shoreface sandstone. Rollins shoreline orientation can be accurately determined by mapping the landward pinchouts of these shale interbeds. The productive intervals of the Rollins can be identified on open-hole logs by a combination of neutron-density cross over, high resistivity, and relatively low calculated water saturations. Productive intervals can also be identified by mud-log gas shows and gas seeps on borehole image logs. Maps of the productive portions of the Rollins parasequences show a series of shore-parallel lenses that shale out in a seaward direction.
AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah