Sequence stratigraphy, depositional history, and hydrocarbon potential of the mancos shale, Uinta Basin, Utah

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Publication Type thesis
School or College College of Mines & Earth Sciences
Department Geology & Geophysics
Author McCauley, Andrew Donald
Title Sequence stratigraphy, depositional history, and hydrocarbon potential of the mancos shale, Uinta Basin, Utah
Date 2013-12
Description The Mancos Shale, an organic-lean marine mudstone dominated by detrital quartz and clay, was deposited into the Upper Cretaceous Western Interior Seaway. It is a proven source rock with potential as a target for hydrocarbon production from horizontal drilling and hydraulic fracturing, but prospective reservoir target intervals from its 4,000 ft (1220 m) thickness must be identified and characterized. The distribution of lithofacies throughout the Mancos has not previously been studied in detail, so this formation remains undifferentiated and the relationship with paleodepositional up- and downdip strata undefined. Previous core-based analysis has provided a depositional and sequence stratigraphic framework for predicting the distribution of lithofacies in the Mancos. However, a unified, basin-wide facies and sequence stratigraphic correlation which tests existing outcrop and core-based models is lacking. 157 wireline logs were chronostratigraphically correlated across the basin to build a regional subsurface map and cross sections that highlight stacking patterns, regional facies relationships, stratal architecture, and sequence stratigraphy within a depositional framework. A sequence stratigraphic model is established for the Mancos Shale, which incorporates seminal outcrop-based models from strata of central Utah, Mancos core, and stacking patterns identified from wireline log data. The Mancos thickens to the north and west, matching regional trends of tectonically driven subsidence, the most significant control on accommodation. The Mancos Shale consists of 29 4th order T-R cycles, which can be stacked to form four 3rd order cycles and a single 2nd order cycle. Whereas the stacking patterns of 2nd and 3rd order cycles are consistent across the basin, suggesting allocyclic control, 4th order cycles are more variable, influenced by both allocyclic and autocyclic controls. Deposition of the Mancos evolved from a low gradient ramp, to a deeper water basin, which was then infilled by basin-floor fans. Two organic-rich facies associations, each corresponding to transgressive and early highstand sequence sets, heterolithic facies of the Juana Lopez and lowermost Blue Gate (FA1) and sediment starved shelf deposits of the Lower Blue Gate (FA2) offer the most prospective intervals for unconventional hydrocarbon production. Preliminary petrophysical analysis and basin modeling corroborate this analysis.
Type Text
Publisher University of Utah
Subject Mancos shale; Sequence stratigraphy; Uinta Basin
Dissertation Institution University of Utah
Dissertation Name Master of Science
Language eng
Rights Management Copyright © Andrew Donald McCauley 2013
Format Medium application/pdf
Format Extent 3,865,582 bytes
Identifier etd3/id/2687
ARK ark:/87278/s6m363xr
Setname ir_etd
Date Created 2014-02-07
Date Modified 2017-11-02
ID 196262
Reference URL https://collections.lib.utah.edu/ark:/87278/s6m363xr