Influence of transport and reaction on wormhole formation in porous media

Abstract

The transport and reaction of fluids in porous media results in unique pore growth and channel evolution as the media are dissolved. This often leads to the formation of highly conductive flow channels, commonly referred to as wormholes. The objective of this work is to predict the influence of transport and reaction on the structure of the wormhole channels. An experimental and theoretical investigation of a variety of fluid systems, including strong acids, weak acids, and chelating agents, provides a wide range of conditions for studying wormhole formation. A generalized description of the dissolution phenomenon is introduced, and a common dependence on the DamkÖhler number is demonstrated. The DamkÖhler number is shown to dictate the type of wormhole structure formed by systems with various degrees of transport and reaction limitations. An optimum DamkÖhler number for channel formation is observed at a value of approximately 0.29 for all of the fluid systems investigated. The stochastic nature of the dissolution phenomenon is described using network models. Results from a 2-D network model and a 3-D physically representative network model agree qualitatively with experimental results and substantiate the existence of an optimum DamkÖhler number.