Fracture Potential of Evaporite Seals
S. Esperancinha1 and J. Cosgrove1
Cap-rocks or seals are fine grained, low capillary-entry pressure units that serve as aquitards and prevent the upward migration of fluids (Gluyas and Swarbrick, 2003). Evaporite rocks such as anhydrite are generally seen as efficient cap-rocks, as a result of their low permeability and because they are thought to deform in a ductile manner. However, examples from mudrock such as the Mercia Mudstone, where the chance preservation within evaporite-rich horizons of generally transient fracture networks by the injection of sandstone dykes or the precipitation of satin spar veins, demonstrate that transient networks of fluid induced fractures form in low permeability rocks (Cosgrove, 2001) allowing the movement of fluids both out of and through these potential seals.
AAPG Search and Discovery Article #90188 ©GEO-2014, 11th Middle East Geosciences Conference and Exhibition, 10-12 March 2014, Manama, Bahrain