Excess Pressure and Reservoir Compartmentalization in the Sable Subbasin, Offshore Nova Scotia
Abstract
In the Sable Subbasin, fluid pressures have been observed in Jurassic and Early Cretaceous reservoirs in over 200 wells and increase with depth in unexpected increments from hydrostatic to excess pressured. In this study, the pressure distribution in the Sable Subbasin was investigated with a geocellular model of the reservoirs in five gas fields. The model was built by interpreting 3D seismic data calibrated with wells, and populated with excess pressure and petrofacies. In the “deep” section, fluids and pressures are interpreted to be dissipating by mechanical leak. In the “intermediate” section, pressure equilibration within pressure cells occurs where displacement of minor crestal faulting exceeds the thickness of seals. In the “shallow” section, reservoirs are hydropressured. The distribution and dissipation of pressure in the Sable Subbasin is controlled by reservoir connectivity, which is dependent on permeability and a result of interplay between the regional structure, stratigraphy, diagenesis, and seal integrity.