Liard Basin—a Multi-Story Petroleum System

David Morrow¹, Bernard MacLean¹, Karen Fallas¹, and Judith Potter^2
1 Geological Survey of Canada (Calgary), Calgary, AB
² JP Petrographics, Calgary, AB

Liard Basin, a 5000 km2 craton margin basin in northwestern Western Canada Sedimentary Basin, has received renewed attention by explorationists because of its proven gas potential. The Cretaceous Maxhamish gas field in northeast British Columbia as well as Devonian (Liard) and Carboniferous (F-36) gas fields, in the Northwest Territories attest to the potential of this basin. Well and seismic data show Liard Basin to contain 5000 meters of preserved Paleozoic (Horn River,Nahanni; Golata/Mattson) to Cretaceous intercalated source rock and reservoir strata (Garbutt/Chinkeh), and to be partly structurally bounded. Bovie Structure, which defines the basin's eastern flank, underwent several stages of movement, including a major westward-verging contractiional motion during the pre-Permian (Carboniferous?). Middle and Upper Devonian source rocks include the overmature Horn River and Besa River shales with up to 5.0% TOC, which may have sourced the Middle Devonian “Manetoe Dolomite” gas fields. Immediately west of Bovie, Carboniferous source rocks, such as the Golata, Prophet, and Banff formations and organic-rich horizons within the Mattson Formation fall within the middle of the oil window but are overmature further northwest. These may have sourced the numerous gas shows in the upper Paleozoic Debolt (Flett), Mattson, and Fantasque formations. Several Cretaceous units, such as the Garbutt Formation, contain moderately rich source rocks but their levels of organic maturities only reach the top of the oil window (0.6%Ro). This suggests that gas trapped in the Cretaceous Chinkeh Formation in the Maxhamish Field has migrated upward from within Liard Basin across multiple formations.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005