Northwest Territories Geological Survey

The Shale Basin Evolution Project was initiated by the Northwest Territories Geological Survey (NTGS) in 2014. The primary purpose of the project was to extend the recently completed NTGS source rock characterization studies of the Devonian age shales of the Bluefish Member of the Hare Indian Formation and Canol Formation from the Mackenzie Plain toward the north and west into the Peel Plain and Plateau areas of the Northwest Territories, respectively. NTGS expanded the scope of this study in 2016 to include a rigorous scientific assessment of all of the shales of the Devonian age Horn River Group, now including the Bell Creek Member of the Hare Indian Formation as well as the Bluefish and Canol shales into the study. Outcrop, subsurface core, and chip sample studies have been conducted annually since 2014. This talk focuses on the Middle to Late Devonian stratigraphy of the Horn River Group, and highlights the scientific results from the 2014 and 2016 field seasons in a regional context. Preliminary results from the 2018 season are also discussed.

The Givetian-Frasnian aged Horn River Group comprises the Hare Indian (Bluefish and Bell Creek members), Ramparts, and Canol formations. It overlies the regionally extensive carbonates of the Hume Formation, and is in turn overlain by shales and sandstones of the Imperial Formation. The Hare Indian Formation and Canol Formation, although variable in thickness, are present throughout the study area and comprise organic poor to organic-rich shales. Conversely, the Ramparts Formation is restricted to parts of the northern Mackenzie Plain and southern Peel Plain and Peel Plateau areas and comprises carbonate lithologies. The Kee Scarp Member of the Ramparts Formation produces Canol Formation sourced oil from a conventional oil pool at Norman Wells.

The Bluefish Member of the Hare Indian Formation comprises organic-rich shales with generally good, but regionally variable TOC content, also indicated by consistently high uranium concentration. Silica content in the Bluefish Member is moderate and variable, resulting in lower brittleness of the rock, which was also observed in the field. Terrestrial input, based on geochemical indicators, is generally low, but increases upward in stratigraphy. Palaeoredox indicators suggest deposition under at least partly anoxic conditions. The Bell Creek Member has generally low TOC content and low uranium concentration. Silica content is also low with an elevated terrestrial input signature. Palaeoredox indicators suggest sustained oxic conditions. The Canol Formation has a variable, but generally elevated TOC content. Silica content is the highest of these formations, resulting in brittle fracturing noted in the field. Terrigenous input is low through Canol Formation deposition. Palaeoredox indicators suggest variable conditions during deposition. Source-rock and vitrinite reflectance analyses indicate a regionally variable trend of rock maturity, with generally increasing maturity toward the western part of the study area. Available conodont and stable isotope analysis results aid in delineating the chronostratigraphy of these strata. These results, in conjunction with forthcoming results of the 2018 field work, well sampling, and available seismic data, will be used in a regional basin modelling effort.