f What is a Suitable Reference Stress State for Overpressure Modelling?

Sedimentary basins are generally broad depressions (large width thickness ratios), and each has a unique geologic history (Dickenson, 1993) that may include rapid, localised subsidence episodes, with consequent development of compaction dis-equilibrium overpressure. Process-based models (generally 1-D) are widely used to simulate the effects of this rapid deposition and the inability of the newly-loaded sedimentary rocks to achieve sufficient de-watering. Such models are highly dependent on the values assigned to unconstrained variables such as shale permeabilities. Indeed, if it were not for the built-in preventive measures, the calculated fluid pressures could easily exceed the "limiting" lithostatic pressure.