The SOHIO Nechelik No. 1 Well, Colville River Delta Area, Alaska
The SOHIO Nechelik No. 1 well is located in Sec. 18, T.12N., A.SE., Colville River delta area, northern Alaska, west of the Kuparuk and Prudhoe Bay fields, and just east of the National Petroleum Reserve in Alaska (NPRA). It was drilled in 1982, reaching a total depth
of 10,018 feet.
Samples of core chips from eighteen horizons over the depth interval 7113-7216 feet were examined megascopically and microscopically. These horizons have been interpreted as being stratigraphic equivalents of the Kuparuk River Formation. They have informally been termed the "Nuiqsut Sands" by other investigators. Of principal interest were structural and textural characteristics, the nature and relative abundances of principal rock fabric elements framework grains, matrix, cements, porosity, as well as proportions of constituent framework grain types. Reservoir quality attributes, diagenetic relationships, and sedimentologic information were of particular concern.
The samples analyzed are fine- to very fine-grained sandstones: principally sublithic arenites/wackes; one is a quartz arenite/wacke, another two are sublithic arenites. All contain appreciable proportions of pervasive and/or laminated clay-size materials, in part at least apparently involved in bioturbation. Grains of glauconite are commonly present, in trace amounts. With one exception, these rocks are all quite low in visual porosity, and presently exhibit poor apparent fluid storage or transmissive qualities. However, oil-staining/hydrocarbon shows have been recognized throughout this interval.
Additionally, two thin-sections representing depth intervals of 6382 and 6387 feet, within the lower portion of the Torok Formation (Brookian), were similarly studied petrographically.
The latter samples are very fine-fine grained sandstones: litharenites, with a preponderance of the constituent lithic grains comprised of sedimentary rocks: argillaceous, cherts, carbonate materials. These rocks are also slightly feldspathic, containing both plagioclase and potassium feldspars. Each of the two sandstones exhibits a moderate amount of visible porosity (12%), principally secondary in character, but there is appreciable microporosity associated as well.