Abnormally high pressure exerted by subsurface formations is known as what term?

• A. Overpressure
• B. Lithostatic
• C. Hydrostatic
• D. Geopressure

Answer: (D)

Geopressure is the term used for abnormally high pore pressure within subsurface formations. This pressure exceeds what would be expected from the normal water column (hydrostatic) and is not the total stress carried by the rock itself (lithostatic); instead, it’s the fluid pressure in the rock’s pore spaces that remains elevated due to factors like rapid burial, undercompaction, clay diagenesis, or hydrocarbon generation. Recognizing geopressure is crucial in drilling because it reduces effective stress on the rock, increases the risk of kicks or blowouts, and dictates the need for heavier drilling mud or other pressure-control measures to safely balance the formation pressure. Overpressure is a general way to describe high pressures, but geopressure specifically refers to the abnormal pore pressure found in formations, which is why it’s the best term here.