Petrophysical Evaluation of the Hiawatha Deep Unit #5 well in the Vermillion Basin, Northwestern Colorado

Tracy, George¹, Kimberley Kaiser², and Richard Newhart^2
1Schlumberger Oilfield Services, Greenwood Village, CO
²Questar, Denver, CO

    The Hiawatha Deep Unit #5 (HDU #5) is located in Sec. 15- T12N-R100W, Moffat Co., Colorado. The well was drilled into the Jurassic Morrison Formation and reached a total depth of 14,030 ft. Primary objectives in the HDU #5 were the Cretaceous Frontier and Baxter formations. Both reservoirs were buried at depth sufficient to place the intervals in geo-pressure, providing an unconventional play in the Baxter Shale and stratigraphic traps in the Frontier.
     Two cores were cut in the Baxter Shale in the HDU #5 at depths of 12,343 to 12,390 ft and 12,951 to 13,005 ft. Observed lithologies in the cores range from relatively pure, laminated shales to thin interbedded sandstones, siltstones, and shales. Laminated shales contain 0.5 to 2% total organic carbon. The mineralogy in the shalerich and siltstone-rich intervals includes quartz, calcite, dolomite, plagioclase, authigenic pyrite and trace amounts of other minerals. Clays, which comprise 12.8 to 37% of total rock composition, are dominated by illite and chlorite.
     The Schlumberger Platform Express, Dipole Sonic Imager and Formation Micro Imager were used to log the HDU #5. Petrophysical and rock-mechanic models incorporate the observed mineralogy and are calibrated to core analysis. Total organic carbon values from logs are calculated and a representative amount of kerogen is added into the model. With core-derived shale matrix permeabilities of 52 to 115 nanodarcies, traditional log-derived permeability results are inadequate and must be revised. The petrophysical model also includes a gas-in-place calculation that is calibrated to a known core Langmuir desorption/adsorption isotherm profile.

AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah