Abstract: Wireline Log Detection and Evaluation of Seals in the Western Canadian Basin

Murray Grigg

The Western Canadian basin is comprised of four pressure systems. A shallow hydrodynamic pressure zone is underlain by a deeper underpressured hydrocarbon-charged system. Still deeper in the basin, the section may be overpressured and hydrocarbon saturated, while the deepest sections return to normal pressures. The top of underpressures does not follow a specific stratigraphic horizon, but rather appear to coincide with basin maturity of .8% vitrinite reflectance. The top of the deep, normally pressured regime corresponds to the top of the Paleozoic section.

The top of underpressure and overpressure was identified using a novel wireline log technique together with measured basin pressures. Changes in Cretaceous shale compaction state, as reflected in sonic transit time, were correlated with the onset of hydrocarbon generation and pressure regime. We conclude, that in the Western Canadian basin, the top of underpressure coincides with the top of mature source rock and the onset of hydrocarbon saturation in the Alberta Deep basin area. These observations lead us to believe that hydrocarbon generation is the key control on hydrocarbon saturated area of the basin, and the development of abnormal pressures in the Western Canadian basin. These concepts has been the focus of many exploration plays at Canadian Hunter during the past few years, an some play results are presented.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994