Karsten F. Kroeger

A three-dimensional insight into the Mackenzie Basin (Canada): Implications for the thermal history and hydrocarbon generation potential of Tertiary deltaic sequences

The stratal architecture of the Mackenzie Basin was reconstructed based on seismic and well data and used to define a three-dimensional model to reconstruct the so-far poorly known thermal and maturation history of the basin. To correctly account for the complex tectonic history of the Mackenzie Basin, episodes of uplift and erosion were implemented based on interpretations of original depositional surfaces. Our results indicate that the combined effects of basin inversion and low surface temperatures inhibited maturation from the late Miocene forward in all except the most deeply buried parts of the basin. This explains why upper Eocene and younger deposits are mostly immature despite their burial to more than 5000 m (16,400 ft). The specific history of the basin is shown to control the time intervals of potential hydrocarbon generation. Predictions of transformation ratios using a variety of published kinetics to account for source rock kinetic variability indicate that potential generation from Paleocene and older strata occurred mainly before the late Oligocene. The generation from Eocene strata, however, occurred mainly during the Miocene and, therefore, is interpreted to be a source for Oligocene and younger gas-rich reservoirs. These findings contribute to a better understanding of hydrocarbon systems in the Mackenzie Basin and are the basis for future studies of hydrocarbon migration and accumulation.

Hydrocarbon flow modeling in complex structures (Mackenzie Basin, Canada)

The Mackenzie Basin in northwest arctic Canada has many characteristics of a typical terrestrial, gas-rich sedimentary basin, but the origins of this important hydrocarbon province are still not well known. The three-dimensional basin modeling approach employed here illustrates not only improved capabilities but also potential pitfalls in reproducing flow in complex stratal and structural basin architectures of present-day models. Listric fault structures especially are still inadequately reproduced in most migration models. By integrating individual styles of deformation and introducing a sequence-stratigraphic approach to reproduce the stratal architecture, we are able to identify temporal and spatial relationships between sources and reservoirs. Based on these considerations, three genetic groups of oils in the basin are proposed: a first group mainly related to a Paleocene source rock, a second group related almost exclusively to an early mature source in the Eocene Taglu formation, and a third group related to the Upper Cretaceous Smoking Hills and Boundary Creek formations. In contrast to oil accumulations, gas accumulations resulted mainly from a filling event in the late Miocene, which is interpreted to be related to a decrease in pressure during a late Miocene uplift and erosional event. The Mackenzie Basin is therefore an excellent example to show that the gas proneness of a mature petroleum system, especially if the organic matter is predominantly of terrestrial origin, is mainly a function of expulsion efficiency and timing and thus is directly linked to the structural history of the basin.