Organic petrology, maturity, hydrocarbon potential and thermal history of the Upper Devonian and Carboniferous in the Liard Basin, Northern Canada

Abstract

Organic petrology and RockEval-TOC pyrolysis studies were carried out on over 600 samples of shales, siltstones, marls and coals from forty three sections in the Upper Devonian and Carboniferous strata of the northern part of the Liard Basin and adjacent areas of northern Canada between latitudes 59° 30' N and 60° 30' N and longitudes 121° 30' W and 125° W, to determine the hydrocarbon source potential, thermal maturity and thermal history. The focus of the study is on the optical characteristics and genesis of bitumens and their viability as indicators of thermal maturity. Total organic carbon (TOC) contents indicate that potential oil and gas source rocks occur in the Muskwa, Kotcho, Besa River, Exshaw, Lower Banff, Yohin, Clausen, Golata and Mattson formations; the latter includes thin algal laminites and sapropelic coals. Hydrogen versus oxygen indices indicate that the organic matter comprises Type II kerogen, except for the Golata and Mattson formations which contain mixed Type II and Type III kerogen. Petrographic analysis indicates that the organic components consist of primary and secondary liptinites of marine origin and indigenous microscopic bitumens. In addition, shales in the Golata and Mattson contain structured liptinite macerals, predominantly sporinite derived from Carboniferous mega- and microspores. ... Organic petrology and RockEval-TOC pyrolysis studies were carried out on over 600 samples of shales, siltstones, marls and coals from forty three sections in the Upper Devonian and Carboniferous strata of the northern part of the Liard Basin and adjacent areas of northern Canada between latitudes 59° 30' N and 60° 30' N and longitudes 121° 30' W and 125° W, to determine the hydrocarbon source potential, thermal maturity and thermal history. The focus of the study is on the optical characteristics and genesis of bitumens and their viability as indicators of thermal maturity. Total organic carbon (TOC) contents indicate that potential oil and gas source rocks occur in the Muskwa, Kotcho, Besa River, Exshaw, Lower Banff, Yohin, Clausen, Golata and Mattson formations; the latter includes thin algal laminites and sapropelic coals. Hydrogen versus oxygen indices indicate that the organic matter comprises Type II kerogen, except for the Golata and Mattson formations which contain mixed Type II and Type III kerogen. Petrographic analysis indicates that the organic components consist of primary and secondary liptinites of marine origin and indigenous microscopic bitumens. In addition, shales in the Golata and Mattson contain structured liptinite macerals, predominantly sporinite derived from Carboniferous mega- and microspores.