The Role of Fluid Overpressure in the Development of Fracture Corridors: A Finite Element Modelling Study

Fracture corridors, narrow zones of closely-spaced sub-parallel fractures that are critical to fluid flow through many reservoirs, often nucleate around tips or bends in larger faults. In this study we use finite element models to examine the stress field around such fault bends. We focus particularly on the impact of fluid overpressure and of the fractures themselves on the local stress field, and examine whether these factors can account for the development of fracture corridors. We found that fluid overpressure can cause a complete realignment of the stress field around the faults, driving any fractures to propagate outwards, away from the fault, rather than to bend back into the fault as occurs under hydrostatic fluid pressure. This occurs in both permeable and impermeable host rocks. Furthermore, if the overpressure is sufficient to cause the fractures and faults to dilate, a low stress zone develops ahead of the propagating fracture tip that may trigger the propagation of other microcracks in this region. This leads to the development of fracture corridors that propagate outwards from the initial faults and may eventually link with other faults or fracture corridors, providing long-distance flow pathways.