Fracturing and Porosity Channeling in Fluid Overpressure Zones in the Shallow Earth’s Crust

Figure 3

Two end-member cases for the development of effective stresses: fluid overpressure zone versus fluidization. (a) The effective stresses for scenario 1 where all stresses including the differential stress decrease and become zero. (b) The fluid pressure, (c) the porosity pattern, and (d) the mean stress in color and corresponding fractures in black. Scenario 1 leads to a semihorizontal high-porosity channel and a breccia-like fracture zone. (e) The stresses for scenario 2 with the effective mean stress decreasing while the effective differential stress stays almost constant. (f) The fluid pressure, (g) the porosity pattern, and (h) the mean stress and fractures for the fluid overpressure zone. A vertical central dilating zone with high-porosity channels develops in a zone that is much narrower than the high fluid pressure zone and the fracturing. Time is in hours (relative color scale below the figure).

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