Datensatz

Zusammenfassung

The Mackenzie Delta, N- Canada, contains 14 -16 km Tertiary and upper Cretaceous intervals of which the upper 5 km are drilled. Therefore estimates of deep basin hydrocarbon potential are one of the major uncertainties in this area. Basin modelling programs, laboratory experiments and hydrocarbon formation models are routinely used to extrapolate from shallower source rock properties to deep settings in the Mackenzie Delta. In the evaluation of deep basin hydrocarbon potential the presence of petroleum prone vs. exhausted source rocks is of major interest here. We show that the Mackenzie Delta sediments are associated with a great risk of underestimating the petroleum potential in overmature sequences. Some deltaic source rocks form a hydrocarbon prone material which degrades beyond the conventional window of primary and secondary hydrocarbon formation. This type of neo-formed macromolecular organic matter is not part of the original, immature organic matter and therefore is overlooked when using established peroleum prediction tools. It contains the potential for the generation of an additional 20% of hydrocarbons beyond the conventional petroleum formation window. This material is most likely formed through recombination processes under closed system conditions. Carbon isotopes of methane formed from this organic matter fits natural gas characteristics in the Mackenzie Delta. Kinetic models were developed which describe its formation and transformation. Applied to the Mackenzie Delta, the bottom of the hydrocarbon formation window is displaced to 2000 m greater depth relative to the conventional estimates. Our results significantly enhance the hydrocarbon prospectivity of deep sediments in deep basins.