Application of hydrodynamics to sub-basin-scale static and dynamic reservoir models

The study of basin hydrodynamics uses techniques that take into account the fact that, while the pre-production trapped hydrocarbon phase is static, the aquifer at the base of the hydrocarbon accumulation is dynamic. Regional boundary conditions can be identified that drive formation water flow and help define formation water influx and discharge from an aquifer system rather than assuming a fixed aquifer volume. Pressures in an aquifer may therefore vary for a given depth, due to variations in the hydraulic potential field resulting from differences in aquifer properties across a sub-basin. Hydrodynamic techniques also characterise formation pressure data using a hydraulic head to avoid the requirement of referencing a formation pressure to a depth datum. It removes the need to assume a particular fluid pressure gradient when the fluid composition is not known. This paper describes how hydrodynamic techniques can be incorporated into the static and dynamic reservoir models to reduce errors and uncertainty in the model results. These include the use of a potentiometric energy distribution for the aquifer to obtain aquifer pressure rather than an average hydrostatic gradient and a basin wide depth datum, and the characterisation of natural inflows and discharges rather than assuming a fixed aquifer volume. The approach is exemplified with data from various basins.