Geochemical-geomechanical feedback in stressed fracture systems

Abstract:

The performance of emerging energy technologies that target low-permeability reservoirs can be controlled by complex feedback among flow, mechanics, and geochemical reactions within fracture systems. Fluid transport can be dramatically altered by the generation or closure of fractures along with competing geochemical reactions, as mineral dissolution and precipitation can erode or seal flow paths, respectively. This talk will first highlight a series of triaxial direct shear experiments demonstrating how these processes occur simultaneously in natural systems. Carbonate-rich shales were sheared with BaCl₂-rich fluids within an x-ray computed tomography (xCT) scanner, providing real-time monitoring of fracture and precipitate evolution. The results, in combination with preceding core flooding experiments, confirm that freshly activated fractures significantly enhance the rate and extent of mineral precipitation due to the generation of rock fragments with high reactive surface area. However, the impact of precipitates on fluid transport were strongly contingent on their distributions, which are controlled by heterogeneities in fracture geometry, mineral composition, reactive surface area, and fluid chemistry.

The second half will focus on recent efforts to decouple geochemical and geomechanical processes that can promote significant changes to fracture connectivity and flow behavior, such as short-circuiting or flow blocking. Additional triaxial core flooding and complementary microfluidic experiments provide direct non-destructive visualization of micro- and pore-scale phenomena, respectively, in stressed geologic materials under representative subsurface conditions. Integration of experimental outputs into predictive modeling frameworks accounting for chemical-mechanical feedback will also be discussed. In combination, the results demonstrate how fracture geometry, mineral heterogeneities, and resulting effects on flow dynamics control geochemical reactivity, which in turn impacts permeability and fracture strength. Evaluating these coupled processes across multiple scales advances our ability to predict where interplay among geochemical reactions and mechanical deformation may limit or enhance fluid transport in low-permeability formations.