Regional maturation study in the King Christian Island area, Arctic Canada

The hydrocarbon potential of the Mesozoic succession in the vicinity of Kin g Christian Island in central Sverdrup Basin was evaluated on the basis of maturation parameters and knowledge of the regional geology. The Triassic S chei Point Group, which is the main source rock interval in Sverdrup Basin, is in the mature stage of hydrocarbon generation (Ro > 0.60%). The type of organic matter is mainly planktonic marine algae and bituminite, deposited in an offshore shelf setting. Rock-Eval T-max values are in the range 428- 444 degrees C, in general agreement with reflectance. Organic richness is i ndicated by the high hydrogen index (HI) values in the shales (in excess of 300 mg HC/gTOC) Less rich source rocks are found in the Jurassic-age James on Bay and Ringnes formations, in accordance with previous studies in the n earby Lougheed and Melville islands. Numerous oil and gas fields have been discovered in King Christian Island t o dare. Geology shows that the presence or absence of liquid and gaseous hy drocarbons in the reservoirs is related to the development of a system of f aults and fractures in the successions stratigraphically above the source r ocks. These zones have acted as conduits for oil and gas migration and ulti mately, loss. The presence of bitumen staining and numerous populations of solid bitumen, interpreted as allochthonously derived support the theory of hydrocarbon migration in the King Christian Island succession. Migration h as taken place over a vertical distance of 800 m to 1500 m. Problems were encountered in measuring vitrinite reflectance, related mainl y to the presence of cavings, bitumen staining vitrinite typing oxidation o f organic matter, and effect of igneous intrusions. The thermal effect from igneous silts and dykes resulted in thermal cracking of liquid hydrocarbon s to gaseous in certain areas. A zone of paleo-overpressure was identified near the contact between a chick sandstone unit and overlying shales exhibi ting a "kinky" vitrinite reflectance profile. Overpressure was attributed t o a combination of hydrocarbon generation in the Schei Point or deeper sour ce rocks, high rates of sedimentation in Jurassic to Cretaceous shale units , differential compaction of lithologies, and entrapment of pore wafer.