Résumé
We develop a new coupled hydro‐mechanical‐chemical (HMC) model to investigate the stress‐controlled evolution of dissolution cavities along a hectometer‐scale heterogeneous fracture. The fracture is conceptualized to consist of numerous patches associated with spatially‐variable, stress and dissolution‐dependent local stiffnesses and apertures. We consider the complete coupling relationships among mechanical deformation, fluid flow, and chemical dissolution within the fracture. More specifically, our model captures non‐linear fracture deformational responses and their consequences on localized flow pattern and dissolutional aperture growth, as well as the feedback of dissolution to mechanical weakening and stress redistribution. We elucidate how geomechanical processes affect the aperture and flow patterns and the formation of small to large dissolution cavities. Our simulation results show that stress retards the permeability increase with the extent of retardation positively related to a dimensionless penetration length l p ′. Stress induces the splitting of the dissolution front, promoting localized flow and branched dissolution. At low l p ′ (wormhole dissolution regime), stress also promotes the sustained growth of dissolution branches. Hence, there is no apparent increase in global flow heterogeneity. At high l p ′, stress transitions the system from uniform dissolution into wormhole formation. Wormholes initiate from remote stiffer regions and converge toward the inlet. Our results have important implications for understanding various dissolution phenomena in subsurface fractured rocks, ranging from karstification to reservoir acidization.
Understanding how fractures dissolve is of great importance for various geoscience and geoengineering problems, such as karst formation, hydrocarbon extraction, groundwater management, and geothermal development. However, subsurface fractures are inevitably influenced by the associated stress condition. The interplay among stress, heterogeneity, flow, and dissolution in field‐scale fractures still has not been well understood so far. Here, we develop a new numerical model that couples fracture dissolution with mechanical deformation and fluid flow to investigate this problem. We elucidate how fracture dissolution affects the stress re‐distribution, which, in turn, controls the fracture opening and the flow organization as well as the dissolution process. The simulation results show that stress can slow the fracture opening due to dissolution and lead to more branched dissolution pathways. Under conditions of high flow rates or less soluble rock, localized dissolution is favored instead of uniform dissolution under the application of stress. Additionally, the localized dissolution pathways develop from the outlet. This study provides mechanistic insights for some karst morphologies observed in nature and also has important implications for relevant engineering applications.
A new coupled HMC model is developed to capture stress‐dependent dissolution along a field‐scale heterogeneous fracture Stress promotes branched and localized dissolution, which may cause a qualitative change in the dissolution regime Wormholes initiate from remote stiffer regions and converge toward the inlet for a dissolution regime with a high penetration length