Analyses of 958 samples from 54 wells in the NPRA (National Petroleum Reserve in Alaska) for TOC (total organic carbon) and EOM (extractable organic matter) have been made available as part of an extensive exploration program sponsored by the U.S. Geological Survey. In the present study, these data have been analyzed using the equation: EOM(wt. %)/TOC(wt. %) × 0.80 = Generation Index. The ratio of EOM to TOC is generally used as an indicator of thermal maturation. Work done by D. R. Baker demonstrates, however, that values in excess of 0.05 are indicative of migrated hydrocarbons in the sample.

Initial results of mapping these ratios for 11 structural zones in the NPRA indicate younger strata (i.e., Nannushuk, Torok, Pebble Shale, Kingak, and Sag River formations) have a significant probable migration fairway developed along the trace of the north-south-trending Meade arch, and toward the eastern margin of the NPRA. Older strata (i.e., Shublik, Ivishak, Echooka, Lisburne, Endicott formations and basement) generally show ratios in excess of 0.05 along the northern and northeastern margins of the NPRA. Although not enough data are available for detailed EOM/TOC mapping of these older trends, they may be related, in part, to the juxtaposition of younger source rocks that unconformably overlie these older strata.

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