Overpressure in a formation, caused by abnormally high fluid pressures, is a concern during all phases of oil field operations—exploration, drilling, casing, completion, and reservoir evaluation. Accurate knowledge of formation pore pressure and fracture pressure is essential for drilling efficient and safe wells with optimum mud weights. Furthermore, knowledge of these pressures aids understanding of fluid migration pathways, sealing potential, and probability of fault leakage.

Overpressure by definition occurs when pore pressure exceeds normal hydrostatic pressure and is related to certain environmental conditions in a given earth section. In the offshore Nile Delta, for example, low permeability shale in the...

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