Title: Overview of Geology and Operations, Grand Valley, Parachute, and Rulison Fields, Piceance Basin, Colorado
Speaker: Steve Cumella, Barrett/ Williams
Date: April 19, 2002
Publication: The Outcrop, April 2002, p. 4-5
Grand Valley, Parachute, and Rulison fields are part of a basin-centered gas accumulation that has formed in the deep part of the basin in an area of active gas generation. Production from these fields, which is from the Williams Fork Formation of the Mesaverde Group, is currently over 170 MMCFPD. The Williams Fork is in these fields is comprised of approximately 3,000-3,500 ft of nonmarine strata, the lower 1,700-2,400 ft of which are gas saturated. The sandstone reservoirs within the gas-saturated interval are predominantly point-bar sandstones that are laterally discontinuous with estimated average widths of approximately 750 ft. The lower 500-900 ft of the Williams Fork is coal bearing and has been named the Cameo Coal Member. The matrix permeability of the sandstones is very low (microdarcy range), but natural fracturing can greatly enhance reservoir permeability. Massive hydraulic stimulation is required to make commercial wells. Wells are typically completed in 4 to 6 stages with average gross intervals of about 300 ft. Net pay averages about 350 ft per well. Estimated ultimate recoveries average 1-2 BCF per well. Over 13,000 acres are currently being developed at 20-acre density, with relatively little evidence of depletion. A pilot is currently being undertaken to determine the viability of 10-acre density.