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Facies relationships and reservoir potential of the Ohio Creek interval across the Piceance Creek basin, northwestern Colorado

Technical Report ·
OSTI ID:6091205

The Ohio Creek Member of the Mesaverde Group, of Late Cretaceous age, grades from a fluvial to a paralic facies from the southern to the central parts of the Piceance Creek basin, and is a facies equivalent of the Lewis transgression/Fox Hills regression to the north. Evidence of marine influence in the east-central part of the basin includes: (1) zones of abundant logs with large Teredolites trace fossils, (2) the results of palynology reports from outcrops at Rifle Gap and the US DOE Multi-Well Experiment (MWX) wells, and (3) marine sedimentary structures visible in outcrop. In this area it is interpreted as the deposits of distributary channel and estuarine environments associated with a fan delta. Northward, the Ohio Creek stratigraphy becomes complex in that while deposition in the southern and central parts of the basin was time-equivalent to the Lewis transgression, those deposits were reworked by early Tertiary erosion and transported north to become younger but correlatable deposits within the stratigraphically higher Fort Union Formation. Although the Ohio Creek in outcrop is highly altered by diagenesis (as documented by Johnson and May, 1980) and is an aquifer in some parts of the basin, the equivalent zones are gas productive in the north-central parts of the basin. Continued changes in facies toward a marine environment to the north affect the petrologic characteristics and sand body/reservoir morphology, increasing the reservoir potential of this zone. The variably thick interval is recognizable in the subsurface as an extensive sandy zone with blocky-shaped log profiles. This interval should provide good (although probably tight) gas reservoirs in those cases where porosity and permeability are not occluded by diagenesis, and where continuity with surface exposures has not allowed gas escape and water influx. 50 references, 15 figures, 2 tables.

Research Organization:
Sandia National Labs., Albuquerque, NM (USA)
DOE Contract Number:
AC04-76DP00789
OSTI ID:
6091205
Report Number(s):
SAND-84-2610; ON: DE85007245
Country of Publication:
United States
Language:
English