Comparison of Oil-Source Rock Correlation Data for Alaskan North Slope: Techniques, Results, and Conclusions: INTRODUCTORY PAPERS

A cooperative Alaskan North Slope oil-rock correlation study was undertaken by 30 private, government, and academic institutions from seven countries. The interpretations reported by all participants were based on independent analyses of the same 9 oil samples and 15 rock samples. Reports by 26 of the participants, plus two supporting papers and this summary paper, are included in this volume. A variety of analytical techniques were used, but certain analyses (organic carbon, pyrolysis assay, solvent extraction, liquid chromatography, carbon isotopes, gas chromatography, and gas chromatography-mass spectrometry) were common to the analytical programs of a majority of the participating laboratories. The results on the same samples reported by different laboratories were generally comparable, except for certain of the more subjective or method-dependent procedures. Statistical comparison of selected results showed that most labs are internally consistent but that the variability among laboratories is greater than expected. Most of the laboratories classified the 9 oils into two oil types, resembling oils from either Prudhoe Bay or Umiat fields, but a number of variations were proposed involving mixing, oil subtypes, and multiple or no oil types. Most of the laboratories conducted a separate geochemical evaluation of the hydrocarbon source potential of the 15 rock samples. Correlation among oils and rocks was difficult owing to the apparent non-source rock character of many of the rock samples. Nevertheless, oil-rock correlations were proposed by 21 of the 26 participating laboratories that contributed reports. Seventeen laboratories indicated the Triassic Shublik Formation as the main source of the Prudhoe-type oil, with eight of those calling upon contribution from the Jurassic Kingak Shale. The pebble shale unit was selected as the source of the Umiat-type oil by 14 labs, with seven labs indicating the Cretaceous Torok Formation as a co-source.