HYDRODYNAMICS AND OVERPRESSURING IN THE JEANNE-DARC BASIN, OFFSHORE NEWFOUNDLAND, CANADA - POSSIBLE IMPLICATIONS FOR HYDROCARBON EXPLORATION

The Jeanne d'Arc Basin, offshore Newfoundland, is an oil-producing bas in exhibiting high overpressures. A hydrodynamic approach is used to a ssess the nature of the overpressuring in the basin and its implicatio ns for future hydrocarbon exploration. Two separate formation water pr essure regimes, or hydrostratigraphic units, exist in the Jeanne d'Arc Basin. The first is a normally-pressured formation water zone to dept hs of 3200 to 4500 m (average 4 km), with no effective basinal scale a quitards. Flow is predominantly vertical in this zone, directed toward open faults. Several of the open faults occur very close to the top o f overpressuring and suggest a relationship between the two regimes. T he second hydrostratigraphic unit is an overpressured zone which occur s below the above-stated depths virtually throughout the basin, and is concentrated mainly in Jurassic sediments. The overpressure probably originated through a combination of mechanisms; compaction disequilibr ium does not solely account for the phenomenon. Estimates of horizonta l stresses in the basin show that overpressuring seems to be associate d with a maximum principal stress rotation from vertical to horizontal , suggesting a relationship between overpressure and the stress regime . The results of this study suggest that hydrodynamic techniques are a potentially powerful tool in future exploration in the Jeanne d'Arc B asin. The identification of large hydraulic and pressure (de-watering) gradients above the over-pressuring suggests that potential hydrocarb on traps in the vicinity may be flushed. The open faults which are act ing as fluid conduits in the basin, as identified using hydrodynamics, may also be transporting hydrocarbons from original traps to new ones located up-fault. Further studies are needed to assess the effects of overpressuring on hydrocarbon migration in the region.