A hydro-geomechanical view of seal formation and failure in overpressured basins

The formation of seals, and the consequent retention of overpressure, is a common and expected event during normal basin evolution in active basins that have a significant mudrock succession. Seal failure, and the resultant limitation to fluid-pressure increase (valve action), is also an expected process. Hydrogeomechanical concepts, including poro-elasto-visco-plasticity (PEVP), and discontinuum models, allow the processes of seal formation and failure to be explained, and predict the state of stress in, and behaviour of, overpressured rocks. Importantly, properties that relate to porosity (such as permeability) can be integrated with this approach. These concepts provide a capability to undertake simulations that can serve as predictive tools. The fluid/rock interactions in a basin can be viewed as a self-organizing system, in the sense that overpressure and the undercompaction it permits retard the creation of accommodation space, and hence act as a negative feedback mechanism that slows the loading rate.