--> Abstract: Integrated Sedimentary, Geochemical, and Geomechanical Evaluation of the Mancos Shale, Uinta Basin, Utah, by Lauren P. Birgenheier, Cari Johnson, Angela Kennedy, Brendan Horton, and John McLennan; #90124 (2011)

Datapages, Inc.Print this page

AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Integrated Sedimentary, Geochemical, and Geomechanical Evaluation of the Mancos Shale, Uinta Basin, Utah

Lauren P. Birgenheier1; Cari Johnson2; Angela Kennedy2; Brendan Horton2; John McLennan1

(1) Energy & Geoscience Institute, University of Utah, Salt Lake City, UT.

(2) Geology & Geophysics Department, University of Utah, Salt Lake City, UT.

The Mancos Shale is a clastically-influenced shallow marine deposit that demonstrates potential for shale gas production in the Uinta Basin, Utah. A detailed understanding of vertical and lateral lithologic and geochemical heterogeneity and its predictability are lacking, yet are necessary for delineating prospective development targets. It has proved difficult to link prospective geologic characteristics to engineering success in many shale gas plays. Here, we have conducted an integrated sedimentary, geochemical and geomechanical study on one Mancos core in order to identify geologic predictors of geomechanical properties that are favorable from an engineering standpoint (i.e. brittleness, hydraulic fracture potential, or the colloquial term “fracability”). Detailed sedimentology and stratigraphic descriptions of the upper Tununk and lower Blue Gate Member of the RGU-1 core, drilled in the Drunkard’s Wash Field in central Utah reveals nine characteristically and depositionally distinct facies, ranging from bioturbated siltstone, to fissile, fractured claystone, and delicately interlaminated sandstone and siltstone. Geochemical proxies collected include X-Ray Fluorescence, %Corg (a proxy for TOC), organic carbon isotopes, and Rock-Eval. Mineralogical analyses, including X-Ray Diffraction and QEMSCAN (Quantitative Evaluation of Minerals by SCANning electron microscopy), were performed on representative samples. Geochemical proxy data provide additional insight into environmental and paleoclimatic conditions. Geomechanical testing on intervals with contrasting sedimentary and geochemical characteristics is in progress and will be statistically evaluated to demonstrate significant geologic-geomechanical relationships. The Mancos Shale and similar Cretaceous Western Interior Seaway deposits are widespread across the Rocky Mountain Region. Therefore, understanding these relationships is relevant to assessing shale gas potential in a broader context, improving selection of premium zones for completion, and designing relevant stimulation techniques.