About This Item
Share This Item
The Ohio Creek member of the Mesaverde Group of Late Cretaceous age grades from a fluvial to a paralic facies from the southern to central parts of the Piceance Creek basin. The Ohio Creek is considered here to be the nonmarine to paralic equivalent of the Lewis transgression to the north. Although it is fluvial in the type area and southern part of the basin, evidence of marine influence in the east central part of the basin includes: (1) zones of abundant logs with large fossil Teredinidae burrows, (2) palynological evidence from outcrops at Rifle Gap and the U.S. Department of Energy MWX wells, and (3) marine-type sedimentary structures visible in outcrop. In this east-central area Ohio Creek depositional environments are interpreted as distributary channel and estuari e.
Although the Ohio Creek is highly altered by diagenesis and is an aquifer in some parts of the basin, the equivalent zones are productive of hydrocarbons in the north-central parts of the basin. Continued changes in facies toward a marine environment to the north affected the petrologic characteristics and sand body/reservoir morphology, increasing the reservoir potential of this zone to the north. The variably thick interval is recognizable in the subsurface as an extensive sandy zone with blocky shaped log profiles; it should provide good reservoirs where porosity and permeability are not occluded by diagenesis, and where continuity with surface exposures has not allowed gas escape and water influx.
End_of_Article - Last_Page 524------------