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U.S. Department of Energy
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Mineralogy and petrology aspects of Mesaverde Formation at Rifle Gap, Colorado, specific to the sedimentology and gas-bearing intervals in the subsurface

Technical Report ·
OSTI ID:6496301

Rifle Gap, situated on the eastern edge of the Piceance Creek Basin, northwestern Colorado, has been the focus of sedimentological studies in an effort to understand the tight, gas-bearing intervals of the inner-basin subsurface. These Mesaverde Formation sandstone exposures were sampled and anlayzed for mineral content and grain morphology. Varying detrital mineralogy supports a sedimentological model for the area which includes shoreline blanket, paludal, fluvial, and marine zones (from bottom to top). Observable mineralogical determinants for the depositional groups include chert, organic and feldspar content, sorting, and grain size. Statistical methods were successful in distinguishing groups in the data which correspond nicely to the model's environments of deposition. Analcime, feldspar, clay, rock fragments, and organics are significant variables in group separation. Time, stability, rock matrix relationships, and grain morphology are proposed as explanatory elements for correlations of variables. The upper and lower half of the section have distinctly different analcime content. Kaolinite is correlated inversely with analcime suggesting an alteration relationship dependent on alkaline lake waters. All observations, correlations, and interpretations of the Rifle Gap data provide a basis for explaining gas-bearing subsurface deposits in the Department of Energy's Wester Gas Sands project Multi-Well Experiment, 12 miles away.

Research Organization:
Sandia National Labs., Albuquerque, NM (USA)
DOE Contract Number:
AC04-76DP00789
OSTI ID:
6496301
Report Number(s):
SAND-83-0287; ON: DE83009473
Country of Publication:
United States
Language:
English