Comment on: “From pore scale to wellbore scale: Impact of geometry on wormhole growth in carbonate acidization by C.E. Cohen et al. [Chemical Engineering Science 63, 3088–3099, 2008

Abstract

During the dissolution of porous rock, positive feedback between fluid transport and mineral dissolution leads to the spontaneous formation of pronounced wormhole-like channels. In a recent paper, Cohen et al. (2008) analyzed wormhole growth and competition in a dissolving porous rock, using a Darcy-scale numerical model developed by Golfier et al. (2002). In particular, they analyzed the competition between wormholes, which hinders the growth of shorter channels and leads to the emergence of a hierarchical structure, with many short wormholes, and only a few long ones. By analyzing the distribution of wormhole lengths (reproduced in Fig. 1) they found evidence for the existence of a characteristic length d ≈ 5cm, at which a change in slope occurs. They concluded that the wormhole competition process is not completely scale invariant. The length scale d was interpreted as marking a transition to a regime where the interplay of diffusion and convection of reactant within a wormhole plays a decisive role in its growth.