Assessment of the conventional petroleum resource potential of Mesozoic and younger structural plays within the proposed National Marine Conservation area, Lancaster Sound, Nunavut
Authors: Brent T A , Chen Z , Currie L D , Osadetz K 
Published: April 2013

Lancaster Sound and its southern inter-island channels lie within a proposed National Marine Conservation Area (NMCA). This report is a review of the current state of knowledge of petroleum systems and prospectivity of the area, and outlines the geological and
geophysical evidence employed to calculate resource potential using a subjective probability method. Cretaceous and younger age sediments formed thick basins in the northern Baffin Bay region of eastern Nunavut during the multi-phase tectonic rifting of Greenland from Canada. During this separation,
and the resulting formation of Baffin Bay, giant river delta systems and open marine conditions provided basin fill sediment into Lancaster Sound Basin. Continued plate tectonic movements resulted in multiple episodes of faulting, fault block tilting, erosion, and deformation. The Lancaster Sound
sedimentary basin exhibits sharp boundaries on its north and east sides that are derived from high-relief faults and basement structures. Its Cretaceous -Tertiary deltaic and marine sedimentary fill reaches significant thickness (&amp;gt;8 km). These strata overlie tilted basement fault blocks
composed of pre-rift strata, including Paleozoic (Ordovician carbonates), Proterozoic (Borden Basin sandstones), or thinned Archean crystalline rocks. After initial basin rift and syn-rift sediment fill, Eocene-age tectonic events provided some structural inversion and deformation influencing both
structural style and contemporaneous sedimentary sequence distribution and preservation. Part of the Cretaceous-through-Paleocene strata is preserved on Bylot Island and the exposure exhibits stratigraphy suitable for petroleum source, reservoir, and seal. Seismic reflection mapping in Lancaster
Sound indicate structural prospects within the interpreted Cretaceous-through-Eocene strata, and in the underlying basement. Oil and gas accumulations sourced from rocks of marine origin of Cenomanianuronian age (Kanguk Formation equivalent) are expected. A potential Paleozoic petroleum system may
exist but was not assessed. Re-evaluation of originally processed 1973 seismic data provide observations interpreted as natural gas/fluid venting (gas chimneys), carbonate mounds at seabed, natural gas hydrate, and free-gas zones below the gas hydrate stability zone. Seismic expression of relative
highvelocity material at seafloor is interpreted as methanogenic carbonate mounds. Deeper observations on seismic data indicate cross-cutting energy that may be indicative of a conventional hydrocarbon / water contact or, alternately, a structure II gas hydrate or diagenetic boundary. Seismic
reflection reveals structural prospects for two plays, one within Cretaceous-through-Eocene strata, and another on the underlying basement horizon. The play level risk assigned to these plays is 0.8 and 0.84, which represent a 20% and 16% chance of discovery, respectively. The potential of
four expected conceptual stratigraphic plays was not assessed due to the lack of seismic stratigraphic interpretation. Our subjective probability resource calculation used geometric details of structural prospects and other model inputs drawn from basin analogs due to the absence of borehole data.
The resources were calculated exclusively for the proposed NMCA. After aggregation of the calculated oil and gas volumes for the two plays, the mean total oil resource is 719 x 106 m3 (4.5 billion barrels) in-place and total gas is 369 x 109 m3 (13.0 Tcf) in-place with an uncertainty range from 98 x
106 m3 (0.60 Bbbls) oil and 59.2 x 109 m3 (2.10 Tcf) gas at the 90% confidence level, to 1611 x 106 m3 (10.1 Bbbls) oil and 807 x 109 m3 (28.5 Tcf) gas at the 10% confidence level.