--> --> Abstract: Preliminary Regional Stratigraphic Correlation, Facies Analysis and Reservoir Characterization of the Upper Cretaceous Mesaverde Group, Uinta Basin, Utah, by Raju Sitaula and Jennifer L. Aschoff; #90124 (2011)

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Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Preliminary Regional Stratigraphic Correlation, Facies Analysis and Reservoir Characterization of the Upper Cretaceous Mesaverde Group, Uinta Basin, Utah

Raju Sitaula1; Jennifer L. Aschoff1

(1) Geology and Geological Engineering, Colorado School of Mines, Golden, CO.

The Campanian-Maastrichtian upper Mesaverde Group (UMG) is a prominent gas-producing interval in the Uinta basin, consisting of a complex suite of fluvial sandstone, mudstone and conglomerate. Several studies have been conducted in UMG, yet the basin-wide correlation, regional depositional systems and architecture of facies are not fully understood. This study (1) identifies the regional distribution of UMG lithofacies in outcrop, (2) qualitatively interprets their reservoir potential, (3) presents a preliminary, regional, sequence-stratigraphic correlation that places specific facies within the regional context, and (4) interprets the structural control on sedimentation. Data and analyses include 15 stratigraphic profiles, outcrop gamma-ray curves, and a regional correlation spanning the Book Cliffs and southern Uinta Mountains. 6 lithofacies assemblages were identified within the Farrer and Tuscher Formations, Price River Formation, and Current Creek Formation in the southeastern, western and northwestern Uinta basin respectively. Generally, the lowermost UMG consists of meandering fluvial and tidally-influenced fluvial facies overlain by a succession of stacked braided-fluvial sandstone, and single- and multi-story meandering fluvial sandstone. Pebbly sandstone and mudstone with pedogenic carbonate nodules caps the succession in the western Uinta basin partitioned from the southeastern Uinta basin by the San Rafael Swell (SRS), a Laramide-style uplift. In the southeastern and eastern Uinta Basin, a conglomerate layer (Dark Canyon Member) marks sequence boundary at the top of the succession. 2 regional-scale flooding surfaces, facies stacking patterns and the sequence boundary at the base of the Dark Canyon Member aided UMG correlation in the basin. In the vicinity of the Swell, flooding surfaces are difficult to track, and the Farrer-Tuscher interval is truncated by several intraformational unconformities. Paleocurrents are highly variable near the Swell, yet lithofacies distribution and stacking patterns are consistent across the Swell. The intraformational unconformities, and paleocurrent shifts are consistent with previous suggestions that deposition was periodically interrupted by the uplift of SRS. Because of the added complexity near the Swell, potential tight gas sandstones are stacked meandering fluvial channels (3-5 m thick) concentrated in the upper section of the Farrer-Tuscher and Price River succession in areas unaffected by SRS.