Reservoir Characterization Study: Porosity, Permeability, Petrography, and Facies Analysis, Upper Cretaceous Tuluvak Sandstone and Other Tertiary to Mississippian Age Units, East-Central Brooks Range Foothills and North Slope, Alaska

By

R.R. Reifenstuhl (Alaska Division of Geological & Geophysical Surveys)

A reservoir characterization pilot study based on surface geologic mapping, facies analysis, petrography, porosity, and permeability focuses on the siliciclastic Upper Cretaceous Tuluvak Formation in particular and on other Cretaceous to Mississippian units in general. The data yield significant reservoir information and bear on petroleum resource assessment, new play-type evaluations, and surface and subsurface stratigraphic correlations of the eastern Colville basin. These rocks are part of the parautochthonous and autochthonous Brookian sequence that crops out in the Brooks Range foothills, and the allochthonous Ellesmerian sequence that crops out along the Brooks Range mountain front. Samples were collected for porosity and permeability analyses from the Schrader Bluff and Tuluvak Formations (Upper Cretaceous), Torok and Nanushuk Formations and Gilead sandstone (Albian to Cenomanian), Fortress Mountain Formation and Cobblestone Member (Aptian to Lower Albian), and Okpikruak Formation (Neocomian), Otuk Formation and Karen Creek Sandstone (Upper Triassic), and Lisburne Group (Carboniferous). Some of the more significant porosity and Klinkenberg permeability data include:

• Tuluvak Formation . . . 8–19% porosity, 0.5–8,000 millidarcy (mD)

• Nanushuk Formation . . . 3–14%, 0.005–247 mD

• Gilead sandstone . . . 5–6%, 0.001 mD

• Fortress Mountain Formation . . . 3–8%, 0.1, 12 mD

• Cobblestone Member of Fortress Mountain Formation . . . 2%, 0.001 mD

• Lisburne Group . . . 1.4–2.8%, 0.1–0.4 mD

The data suggest that the eastern end of the Colville basin may contain significant plays in the Tuluvak and Nanushuk Formation as well as in other units.

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.