Transport‐Controlled Dissolution in an Evolving Fracture: The Extended Purday Solution and Fracture Flow Tests

Abstract

Understanding the controlling mechanism and the resulting rate of reactive transport processes is crucial for an accurate prediction of the evolution of the rock-fluid system in many geological processes and engineering applications. In this study, transport-controlled dissolution in a single fracture was investigated analytically with the development of the extended Purday solution and experimentally with fracture flow tests. The extended Purday solution simulates dissolution in an evolving fracture and extends the validity domain of the Purday solution from a fracture with a uniform aperture to a fracture with aperture heterogeneity in the flow direction. The fracture flow tests include continuous effluent concentration measurements with a novel experimental setup and three-dimensional fracture geometry analysis. The modeling and experimental results agree well and show that the high dissolution rate in the entrance region results in a converging fracture geometry (decreasing aperture in the flow direction). This converging geometry, in turn, reduces the overall dissolution rate in the fracture. The comparison between the modeling and experimental results shows that channel formation and sidewalls affect the morphology of the fracture. The resulting cross-section geometry of the fracture also tends to reduce the overall dissolution rate. This study shows that the extended Purday solution accurately predicts the dissolution rate in an evolving fracture, and that factors, such as channel formation and sidewalls, affect fracture morphology and reduce the overall dissolution rate.