Impact of ultrasonic waves on physicochemical characteristics of subsurface fluid-rock systems: A review on mechanisms, synergistic effects, and applications

In recent decades, ultrasonic treatment has emerged as an environmentally friendly method for remediating groundwater contamination, enhancing the recovery of subsurface hydrocarbons, and improving the properties of fluid-rock interactions in subsurface systems. This review provides a comprehensive overview of the thermal, mechanical, and chemical mechanisms underlying ultrasonic wave propagation in porous media, with emphasis on its applications in groundwater remediation and enhanced hydrocarbon recovery. We explore ultrasound's capabilities in disintegrating organic and inorganic scales, reducing fluid viscosity, evolving emulsion systems, and improving permeability and wettability in subsurface environments. Particular attention is given to the synergistic effects achieved by combining ultrasound with other physical and chemical methods, such as chemical injection, thermal treatments, and nanofluid-enhanced recovery. Practical implications are discussed, including the stimulation of hydrocarbon-bearing formations, removal of formation damage, enhancement of sweep efficiency, and disruption of biofilms in groundwater systems, based on recent laboratory and field-scale studies. Despite its promise, field-scale implementation remains limited by challenges in modeling wave propagation and optimizing sonication parameters under variable formation conditions. Future research directions are proposed to advance scalable, sustainable ultrasound-based technologies in subsurface engineering.