The magnitude and direction of the effective stress acting on a fracture is an important control on whether a fracture is open to flow and the size of the hydraulic aperture. A new option for modelling the coupling of effective stress to fracture aperture has been implemented in NAPSAC.

The principal components of a static effective stress-field are defined that can vary with depth, and whose orientation can vary spatially (for example, oriented relative to structural contours). Hence, a geomechanically based model of aperture variations with orientation and depth can be constructed. The new facility has been tested on an application to a salt dome.