Hydrocarbon Potential of the Chainman Shale, Western Utah

S. Robert Bereskin, Thomas C. Chidsey, Craig D. Morgan, and John McLennan
AAPG

Examination and sampling of a ~500 m surface section from the Confusion Range of western Utah indicates that the Chainman Shale (Mississippian) possesses clear potential for hydrocarbon production. Although very good stratigraphic and geochemical work has been accomplished in the past, application of relatively new geologic and engineering perspectives has confirmed reservoir potential, particularly in the lower 300 m of the formation. Although geochemical measurements are uniformly modest (1-2 wt % TOC), modern laboratory analysis reveals adequate mudrock porosity (3-9% effective) and oil saturation for largely liquid hydrocarbon production. In fact, one surface sample surprisingly contained substantial amounts of mobile oil (8%). Of the four major unconventional reservoir types recognized (organic siltstone, argillaceous mudstone, calcareous mudstone, and siliceous mudstone), the siliceous mudstone and organic siltstone most likely represent the sweet spot lithologies in this geologic instance. If some gross assumptions are made, including a normally pressured well at 1600 m drilling depth, a 30% water saturation, a 20% recovery factor, estimations of recoverable oil on an 80-acre spacing would amount to 270,000 BO over a 20 year lifespan. This estimate is based on surface mapping and geochemical testing exclusively.

AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62^nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013