Petroleum Source Potential of the Beaufortian Succession of the NPRA and Colville Delta Area, North Slope Alaska, Based on Sonic and Resistivity Logs

By

M.A. Keller (U.S. Geological Survey)

Ongoing resource assessment of the North Slope of Alaska by the U. S. Geological Survey includes evaluation of the petroleum source potential of Mesozoic and Cenozoic rocks using the delta log R technique (Passey and others, 1990). This technique uses porosity and resistivity logs in combination with maturity data to produce a continuous profile of total organic carbon (TOC). From the pattern and amount of TOC in the profile produced, the depositional setting and thus the petroleum source-rock potential (kerogen type) of the organic carbon can be inferred (Creaney and others, 1993).

TOC profiles determined by this technique for the Tunalik 1, Inigok 1, N. Inigok 1, and Kuyanak 1 wells of the National Petroleum Reserve in Alaska (NPRA), and the Texaco Colville Delta 1, Nechelik 1, and Bergschrund 1 wells of the Colville Delta area suggest that the Kingak Formation had (or has) important potential for oil and gas generation. Profiles of the Kingak show that it is predominantly less than 2 wt % TOC (cut-off used for effective source potential) and suggest that it contains primarily type III kerogen—consistent with seismic and borehole interpretations of Houseknecht (2001). However, a richer facies is commonly present near the base of the Kingak. The average TOC of this facies in the wells profiled ranges from 2.5 to 3 % (individual values predominantly range from 2–6% TOC) over 150–350 ft. This facies is likely to contain Type II kerogen and be oil prone where deposited in a basinal or other distal setting with low influx of coarse clastic sediment and low oxygen.

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.