Abnormal pressure

pressure exerted by a formation and exceeding or falling below the normal pressure to be expected at a given depth. Normal pressure increases approximately 0.465 psi per foot of depth. Thus, normal pressure at 10,000 ft is 4,650 psi; abnormal pressure is higher than or lower than 4,650 psi. Formations with abnormally high pressure must be controlled to prevent a blowout. (See pressure gradient.)