Geology and Petroleum Potential of the Lomonosov Ridge Microcontinent
Thomas E. Moore1, Janet Pitman2, and Arthur Grantz3
1U.S. Geological Survey, Menlo Park, CA.
2U.S. Geological Survey, Denver, CO.
3Consultant, Palo Alto, CA.
The Lomonosov Ridge (LR) is a narrow microcontinent that spans the central Arctic Ocean between the Siberian and Greenland-Canadian margins via the North Pole. As part of the USGS Circum-Arctic Resource Assessment (CARA), an evaluation of the probability of conventional oil and gas accumulations equal to or greater than 50 MBBOE technically recoverable was completed for this area in 2008. Because the LR is remote and typically lies beneath pack ice, its petroleum geology was inferred from sparse seismic reflection data, a few cores, potential field data, and the regional geology of the eastern Arctic basin.
The LR was rifted away from the Barents Platform of northern Eurasia during the Paleocene, forming the Eurasia Basin and the eastern margin of LR. Its western margin developed as a continental-scale transform related to rotational rifting in the Amerasia Basin in the Jurassic and/or Early Cretaceous and subsequently became the site of clastic outer shelf and progradational continental slope deposits that formed along the northern margin of Europe during the Cretaceous. A thin Cenozoic post-rift sequence composed of fine-grained siliceous to silty mudstones drapes the LR.
Petroleum systems inferred to be potentially active in the LR are those sourced in Triassic and Jurassic marine shales known from the Barents Platform, and in Early and middle Cretaceous condensed shale deposits known elsewhere in the Amerasia Basin. Although containing rich source rocks, the Cenozoic deposits are too thermally immature to have generated petroleum. The Cretaceous strata are hypothesized to contain stratigraphic and structural traps and reservoirs typically present in siliclastic continental margin successions. The traps may have been compromised by Paleogene rift-related erosion and extensional faults.
The LR was divided into shelf and slope assessment units (AUs) separated by a hinge line. The probability of petroleum accumulations of the minimum size was judged to be less than 10 percent in the shelf-deposit AU because of preservation issues, resulting in no quantitative assessment being made. Low to moderate probability in the slope-deposit AU yielded fully-risked mean estimates of 123 MMBO oil (range of 0 to 914 MMBO at 95 and 5 percent probability) and 740 BCF gas (range of 0 to 5528 BCF).
AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia