Two-phase reactive flow within variable aperture fractures

The dynamics of reactive two-phase flow in variable-aperture rock fractures are controlled by the feedback between capillary and gravitational forces, fluid phase structures, and reactions between the aqueous phase and fracture surfaces. In order to overcome the slow dissolution of rock surfaces by water, we used an analog geochemical system involving limestone and a weak hydrochloric acid solution.; In fractures with a near-vertical alignment, the influence of gravity forces leads to fingered phase geometries with relatively low areal saturations. After an initial phase involving competition between aperture-spanning flow paths, film flow was initiated in the fractures.; In low-angle fractures where capillary forces dominate, dissolution of the limestone led to aperture increase and drainage at the top of the fracture. Film flow was not initiated in low angle fractures. There appears to be a general tendency for the establishment of a capillary barrier as a terminal state.