A new two-dimensional reaction-transport code CIRF (chemical interaction of rock and fluid) is used to design matrix acidizing fluids. Processes accounted for include aqueous phase, mineral and gel reactions, temperature and salinity-corrected activities, texture-dependent Darcy flow, thermal transport, dispersion, effective reacting surface, diffusion limited kinetics and nucleation. CIRF has built-in thermodynamic and kinetic databases, transport parameters, new adaptive gridding and mixed finite element-finite different schemes and user-friendly graphical I/O for complex lithologic geometries.
Examples are shown in which well designed fluids enhance permeability through matrix dissolution; permeability damage is shown to result from formation collapse induced by excessive dissolution or the formation of plugs through precipitation. Effects of injected fluid composition and velocity and initial formation state are illustrated in the case of a shaly sandstone. Flow self-focusing is shown through flow-reaction coupling via texture-dependent permeability to produce dissolution fingering and holes.