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1 Department of Geological Sciences and Energy and Minerals Applied Research Center, University of Colorado, UCB 399, Boulder, Colorado 80309;
matthew.pranter{at}colorado.edu
2 Department of Physical and Environmental Sciences, Mesa State College, 1100 North Avenue, Grand Junction, Colorado 81501;
rcole{at}mesastate.edu
3 Colorado School of Mines, Golden, Colorado; present address: Heavy Oil Operating Unit, Chevron Pacific Indonesia, Duri 28884, Indonesia;
henrikusp{at}chevron.com
4 University of Colorado, Boulder, Colorado; present address: EnCana Oil and Gas (U.S.A.) Inc., 370 17th Street, Suite 1700, Denver, Colorado 80202;
Nicholas.sommer{at}encana.com
Matthew J. Pranter is an associate professor of geological sciences at the University of Colorado at Boulder and the head of the Reservoir Characterization and Modeling Laboratory. He received his B.S. degrees in geology and geological engineering from Oklahoma State University and Colorado School of Mines, respectively; his M.S. degree in geology from Baylor University; and his Ph.D. in geology from the Colorado School of Mines. He was previously with ExxonMobil Upstream Research Company and Conoco. His research interests are in reservoir geology and geophysics, sedimentary geology, and reservoir modeling.
Rex D. Cole is a professor of geology at Mesa State College in Grand Junction, Colorado. He obtained his A.S. degree in geology from Mesa Junior College, his B.S. degree in geology from Colorado State University, and his Ph.D. in geology from the University of Utah. His previous employers include Unocal Corporation, Multi-Mineral Corporation, Bendix Field Engineering Corporation, Southern Illinois University-Carbondale, and Asarco Corporation.
Henrikus Panjaitan is an earth scientist working in the Duri heavy oil field operated by Chevron Pacific Indonesia. He received his B.S. degree in geology from Institut Teknologi Bandung, Indonesia, and his M.S. degree in geology from Colorado School of Mines. His interests include reservoir characterization and modeling.
Nick Sommer is a geologist at EnCana Oil and Gas (U.S.A.) Inc. He received his B.S. degree in geology from the University of Texas at Austin and his M.S. degree in geology from the University of Colorado at Boulder. His interests are in fluvial depositional systems and reservoir characterization and modeling.
ABSTRACT
This study addresses the field-scale architecture and dimensions of fluvial deposits of the lower Williams Fork Formation through analysis of outcrops in Coal Canyon, Piceance Basin, Colorado. The lower Williams Fork Formation primarily consists of mud rock with numerous isolated, lenticular to channel-form sandstone bodies that were deposited by meandering river systems within a coastal-plain setting. Field descriptions, global positioning system traverses, and a combination of high-resolution aerial light detection and ranging data, digital orthophotography, and ground-based photomosaics were used to map and document the abundance, stratigraphic position, and dimensions of single-story and multistory channel bodies and crevasse splays.
The mean thickness and apparent width of the 688 measured sandstone bodies are 12.1 ft (3.7 m) and 364.9 ft (111.2 m), respectively. Single-story sandstone bodies ( N = 116) range in thickness from 3.9 to 29.9 ft (1.2 to 9.1 m) and from 44.1 to 1699.8 ft (13.4 to 518.1 m) in apparent width. Multistory sandstone bodies ( N = 273) range in thickness from 5.0 to 47.1 ft (1.5 to 14.4 m) and from 53.2 to 2791.1 ft (16.2 to 850.7 m) in apparent width. Crevasse splays ( N = 279) range in thickness from 0.5 to 15.0 ft (0.2 to 4.6 m) and from 40.1 to 843.3 ft (12.2 to 257.0 m) in apparent width.
These data show that most sandstone bodies are smaller than the distance between wells at 10-ac spacing (660 ft [201 m]). Analyses of interwell sandstone-body connectivity suggest that even at 10-ac spacing, only half of the sandstone bodies are intersected and few are intersected by more than one well.
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