Where does overpressure collide?

In blast physics, overpressure is the amount by which the pressure in a shock wave exceeds the ambient atmospheric pressure, with the peak overpressure just behind the shock front and its accompanying impulse the primary measures of a blast's destructive reach. An explosion drives a sharp pressure rise that decays and then dips below ambient, and structures and bodies are rated against the peak overpressure they can survive. Brode's 1955 Numerical solutions of spherical blast waves computed how this overpressure field evolves with distance from a charge. The referent is a transient excess pressure in air, measured in pascals or psi above ambient, and it is an entirely different construct from the sustained pore-fluid overpressure deep in a sedimentary basin, sharing only the word.[1]

Unit

Pressure above ambient atmospheric, in kPa or psi (with the associated impulse)

Recovery means

Not applicable

Measured by

Recorded by pressure gauges at the shock front, or predicted from charge mass and scaled distance via blast-scaling relations

In petroleum geology, overpressure is pore-fluid pressure in the subsurface that exceeds the normal hydrostatic pressure expected for that depth, generated when fluids cannot escape as quickly as burial, compaction, or fluid expansion would require. It governs drilling safety, seal integrity, and hydrocarbon migration, and misjudging it risks blowouts. Osborne and Swarbrick's 1997 Mechanisms for generating overpressure in sedimentary basins: A reevaluation weighs the processes, from disequilibrium compaction to fluid expansion, that produce it. The referent is a sustained excess of pore-fluid pressure over the hydrostatic baseline, measured in megapascals or psi above normal, and it is a different construct from the fleeting excess pressure of a blast wave, joined to it only by the shared word.[2]

Unit

Pore-fluid pressure above the hydrostatic gradient, in MPa or psi

Recovery means

Not applicable

Measured by

Estimated from well pressure tests, mud weights, and wireline or seismic velocity departures from the normal compaction trend