Changes

  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

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In settings with extreme overpressure, pore-water pressure approaches the pressure required for [[Natural hydraulic fracturing of top seals|natural hydraulic fracturing]]. If the petroleum column is thick enough, the sum of the [[capillary pressure]] and fluid pressure can equal or exceed the pressure needed to [[fracture]] the rock. The result is natural hydraulic fracturing: the seal becomes hydrofractured and the petroleum leaks.

In settings with extreme overpressure, pore-water pressure approaches the pressure required for [[Natural hydraulic fracturing of top seals|natural hydraulic fracturing]]. If the [[Hydrocarbon column|petroleum column]] is thick enough, the sum of the [[capillary pressure]] and fluid pressure can equal or exceed the pressure needed to [[fracture]] the rock. The result is natural hydraulic fracturing: the seal becomes hydrofractured and the petroleum leaks.

==Characteristics==

==Characteristics==

Unlike other fractured seals, hydrofractures remain open only as long as pore pressure exceeds fracture pressure. Once the total pressure drops, the fracture closes. The [[Hydrocarbon column|petroleum column]] height remains approximately in equilibrium with the difference between the water pressure and the fracture pressure.

Unlike other [[Fractured membrane seal leakage|fractured seals]], hydrofractures remain open only as long as pore pressure exceeds fracture pressure. Once the total pressure drops, the fracture closes. The [[Hydrocarbon column|petroleum column]] height remains approximately in equilibrium with the difference between the water pressure and the fracture pressure.

Hydraulic fracture seal failure affects all rock types, but the fracture gradient is a function of rock type and basin. Usually hydraulic fracturing limits the petroleum column height during charging instead of destroying [[accumulation]]s after charging. This occurs where accumulations are charged during times of peak geopressure so the trap capacity is minimal. Charging occurs during times of peak geopressure because both charging and geopressure are a response to high sedimentation and heating rates.

Hydraulic fracture seal failure affects all rock types, but the fracture gradient is a function of rock type and basin. Usually hydraulic fracturing limits the petroleum column height during charging instead of destroying [[accumulation]]s after charging. This occurs where accumulations are charged during times of peak geopressure so the trap capacity is minimal. Charging occurs during times of peak geopressure because both charging and geopressure are a response to high sedimentation and heating rates.