New Exploration Opportunities in the Sverdrup Basin

Keith Dewing
Geological Survey of Canada, Calgary, AB, Canada.

The Sverdrup Basin originated during an Early Carboniferous rifting phase that included evaporite deposition. Sedimentation continued until the Cretaceous. Intrusion of igneous rocks related to Alpha Ridge spreading occurred in the Early Cretaceous. Younger events affecting the basin were burial by sediments derived from the Eurekan Orogen in the Paleocene followed by folding in the Eocene. A significant portion of known hydrocarbon resources are spatially associated with salt domes. New exploration targets will likely focus on traps associated with allochthonous salt.

A thermal maturity dataset has been compiled from Rock-Eval and vitrinite reflectance analyses of subsurface and surface samples. Thermal maturity of subsurface shale correlates well with sonic velocity, indicating a uniform response to thermal stress with depth for Mesozoic strata. Thermal maturity was established at the level of the Upper Triassic Gore Point Member; a good seismic reflector, also in close vertical proximity to the two main oil-prone source rocks in the basin. The Gore Point Member is in the gas window (Ro>1.35%) in the northeastern part of the Sverdrup Basin. The thermal maturity is low along the northern rim of the Sverdrup Basin; an area of potential economic interest, as yet entirely unexplored. The maturity of the Gore Point Member does not exceed 1.2 Ro % in the western Sverdrup Basin. Based on these observations, large quantities of gas found at the Drake, Hecla, and Whitefish fields must be derived from a deeper source. Traps in sandstone of the Lower Triassic Bjorne Formation may be prospective for natural gas where they are covered by an effective seal.

Given that vitrinite reflectance cannot decrease after is it set, it is possible to determine uplift by comparing the depth inferred by the vitrinite reflectance to the current depth of burial. A normal burial curve is established using boreholes drilled in areas with no structural complexity. Low amplitude structures, including the Drake, Hecla and Whitefish fields, show little or no uplift following maximum burial in the Paleocene, indicating that these structures formed prior to the Eocene Eurekan Orogeny. Because they were present at the time of maximum burial, they were available to be charged during hydrocarbon migration. In contrast, high amplitude structures show evidence of large uplifts following maximum burial. They formed in the Eocene and hence post-date most hydrocarbon migration.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia