Mechanisms for Abnormal Pressure Seal in Pressure Compartments

Mechanism for pressure seal is still a baffling problem in pressure compartment research, and researchers have been paying much attention on it. Knowledge of the time scales over which these abnormal pressures are maintained is very important for understanding the processes of oil and gas generation migration and conservation. Generally there are two directly different conceptions of abnormal pressure seal mechanisms, which can be called the static and dynamic schools. The static school deems that rocks , which are nearly impermeable (permeability＜10-8×10-3mm2), can prevent almost all the movements of fluids, such as evaporites and intensively mineralized rocks can act as pressure seals, and the gas coming out of   solution form gas-saturated water in layered sequences of fine-grained and coarse-grained rocks can bring enormous capillary pressure to seal the abnormal pressures and the capillary pressure is additive. While the dynamic school claims that both compartment and seals in a water face continues environment the abnormal pressures will be balanced at low rate diffusion even the existence of low permeability seals (permeability＜10-5～10-7×10-3mm2) having excellent seal ability to prevent water movements but low permeability rocks can reduce the dissipation rates of anomalous pressures to an extremely low level and in other words the pressures are maintained in a long period. The static and dynamic overpressure seal mechanisms have their own factual basis, but gas- water two phase capillary pressure and low rate diffusion seal mechanisms may have more universal meaning.