Lithostatic gradient

Fig. 11. Plot of fracture pressure gradients versus depth. Fracture pressure gradients approach the lithostatic gradient with increasing depth and the two trends more-or-less coincide below 5000 m.

Fig. 14. Relationships between pore-pressures, the hydrostatic gradient, the fracture pressure gradient (approximation to the minimal horizontal stress, Sf,) and the lithostatic pressure gradient (approximation to the vertical stress, S ). Pore-pressures from sea floor to base Pliocene equals hydrostatic. The yellow, dark blue and red pore-pressure trend-lines represent the pore-pressure versus depth gradients for the Paleocene-Eocene, Mid-late Cretaceous and Upper Jurassic-lowermost Cretaceous, respectively. The portion of the red trend-line below approximately 2550 m MSL equals the maximum reservoir pore-pressure trend-line of Fig. 13 and reflects the counter-pressure of the topseal controlling the pore-pressure distribution of hydraulic compartments II, III and (probably) IV.

Fig. 2). Hydrocarbon accumulations within these reservoirs exhibit a range of pore pressures, with the more extreme approaching the lithostatic pressure gradient at depth. 

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