An Assessment of gas resources in low-permeability sandstones of the Upper Cretaceous Mesaverde Group, Piceance basin, Colorado

Abstract

LIST OF FIGURES Figure 1. Structure contour map of the top of the Rollins or Trout Creek Sandsone. Contour interval: 500 ft. 2. Generalized Stratigraphic charts for the Piceance basin: a) northern part of study area, b) central part of study area, 3) southern part of study area. From Johnson and Finn (1986). 3. Isopach of the lies Formation (excluding the Castlegate Sandstone). Contour interval: 100 ft. 4. Isopach map of the Williams Fork Formation. Contour interval: 250 ft, 5. Generalized east-west cross section showing the lies and Williams Fork Formations, and the gas, and gas-water transition zones. 6. Cross section showing lithologies, environments of deposition, present-day formation temperatures, vitrinite reflectance, gas shows, and perforation recoveries. From Chancellor and Johnson (1986). Location of cross section on figure 1. 7. Chart showing relationship between Ro and hydrocarbon generation for type I, type II and type III organic matter. From Dow (1977). 8. Isopach map showing total thickness of sandstones ten feet or greater in the Williams Fork Formation. Contour interval: 100 ft. 9. Isopach map showing total thickness of sandstones ten feet thick or greater in the ILes Formation. Contour interval: 50 ft. 10. Approximate distance above or below the top of the Rollins or Trout Creek Sandstone to the Ro 1.1 thermal maturity level. Contour interval: 1000 ft. 11. Approximate distance above or below the top of the Rollins or Trout Creek Sandstone to the Ro 0.73 thermal maturity level. Contour interval: 1000 ft.

Reserve estimates in western basins. Part 2: Piceance Basin

“…Igneous activity had begun in Early Laramide time and continued in the southeast corner of the Piceance Creek Basin during Oligocene. Johnson (1987) The Piceance Basin gas resources identified by the USGS are contained in the low permeability sandstone reservoirs of the Mesaverde group, located in the central portions of the basin. These reservoirs usually have an in-situ permeability to gas of less than 0.1 md and require hydraulic fracturing to produce gas at commercial rates.…”

“…The National Petroleum Council (NPC, 1980) estimated 33 Tcf of ultimately physically recoverable gas independent of price in the Piceance Basin. The USGS estimate (Johnson et al, 1987) estimated a mean recoverable resource of 13.4 Tcf under the assumptions of current technology and $5.00/ Mcf gas and a mean estimate of 67.9 Tcf under the assumption of advanced technology and an unspecified gas price assumption. The NPC 1992 study estimated 17.4 Tcf under a current technology case and 27.9 Tcf under advanced technology.…”

“…The principal differences between the methods of Scotia and Johnson et al (1987) involve quantification of reservoir properties which were estimated using the Delphi approach (consensus estimates by experts) in the USGS case versus Scotia's approach of measuring and mapping such properties. The principal differences between the USGS estimate and Scotia's estimate involve differences in the porosity distribution as well as the magnitude of the correlation for water saturation.…”

“…The Castlegate and Sego are also considered as separate formations while the Corcoran and Cozzette sandstones are considered members of the Mount Garfield and Iles formations but were originally defined as members of the Price River formation. Figure 30 illustrates the regressive limits of the Mancos tongue and Iles formation and the transgressive limits of the Mancos shale flood surface after Johnson (1987). Note however that Corcoran and Cozzette production is reported far southeast of their regressive limits in the Ragged Mountain and Coal Basin fields.…”

“…The starting point for this study is a resource estimate completed by the U.S. Geological Survey (USGS) (Johnson et al, 1987). The USGS estimate was based on a modified volumetric approach to estimate in-place and recoverable gas resources in low permeability sandstones of the Upper Cretaceous Mesaverde group in the Piceance Basin.…”