Basin Hydrodynamics and Petroleum Occurrence, the Beaufort-Mackenzie Basin, Canada
Analyses of temperature, pore pressure and formation water data collected from drill stem test, mud weight and bottom hole temperature logs in 250 petroleum exploration wells illustrates important relationships between petroleum occurrence and hydrodynamics in the Canadian Beaufort-Mackenzie Basin. Three typical temperature profiles are recognized, each of which represents a thermal regime associated with a specific geological setting. Four types of pore pressure profiles are associated with specific and distinct basin tectono-stratigraphic domains, indicating the interplay of a variety of geological factors and processes causing or redistributing overpressure as the result of deep basin hydrological flow systems. The spatial variations of pore pressures at given depths, as well as along and within specific stratigraphic sequences, indicates that basin-scale flow is primarily driven by the expulsion of overpressured fluids upward and toward the basin margin. The overpressure driven system has an outward flow pattern from Tertiary depocenters through porous and fault zone/fracture conduits, causing overpressure at shallow depth and high temperature anomalies in discharge areas. Positive thermal anomalies are observed to be associated with different structural features, such as uplifted areas, major active fault zones and local positive structures. In contrast, temperature depressions are often associated with post-Paleocene depocenters, where thick post-Paleocene sedimentary successions preserve the record of rapid subsidence and sedimentation. Fluid migration in the porous aquifer systems and permeable fault/fracture zones brings advected heat as the result of formation water motion, producing geothermal anomalies that are coincident with, and indicators of petroleum migration fairways. Many significant petroleum discoveries are spatial and stratigraphically associated with the identified anomalously high temperature areas, both in the major fault zones and within the regional permeable stratigraphic aquifer units, indicating that both the structural and stratigraphic framework controlled the preferred fluid migration pathway of both water and petroleum. We illustrate how basin hydrodynamic characteristics correspond with the occurrence of significant discoveries in close association with the structurally and stratigraphically controlled regional permeability network in the Beaufort-Mackenzie basin.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009