Dissolution Hotspots in Fractures

Abstract

AbstractThe injection of reactive fluid into fractured reservoirs is relevant to many subsurface processes. During injection, fracture dissolution forms various patterns. Despite its importance, the evolution of geometries in radial fractures remains unexplored experimentally. Here, by flow‐visualization experiments, we characterize dissolution patterns and show that the patterns shift from compact to wormhole to uniform as flow rate increases. For the first time, we observe dissolution hotspots with maximum local dissolution rate in radial fractures, occurring at a distance from the inlet. We elucidate the key role of gravity for the occurrence of hotspots. The locations of hotspots correspond to the state that the effects of transport in the horizontal and vertical directions are comparable. We establish a theoretical model for predicting locations of hotspots in good agreement with experiments. This work demonstrates transitions of dissolution patterns in fractures and reveals the underlying mechanism for dissolution hotspots previously unidentified.