Capturing the Dynamic Processes of Porosity Clogging

Understanding mineral precipitation induced porosity clogging and being able to quantify its non-linear feedback on transport properties is fundamental for predicting the long-term evolution of energy-related subsurface systems. Commonly applied porosity-diffusivity relations used in numerical simulations on the continuum-scale predict the case of clogging as a final state. However, recent experiments and pore-scale modeling investigations suggest dissolution-recrystallization processes causing a non-negligible inherent diffusivity of newly formed precipitates. To verify these processes, we present a novel microfluidic reactor design that combines time-lapse optical microscopy and confocal Raman spectroscopy, providing real-time insights of mineral precipitation induced porosity clogging under purely diffusive transport conditions. Based on 2D optical images, the effective diffusivity was determined as a function of the evolving porous media, using pore-scale modeling. At the clogged state, Raman isotopic tracer experiments were conducted to visualize the transport of deuterium through the evolving microporosity of the precipitates, demonstrating the non-final state of clogging. The evolution of the porosity-diffusivity relationship in response to precipitation reactions shows a behavior deviating from Archie's law. The application of an extended power law improved the description of the evolving porosity-diffusivity, but still neglected post-clogging features. Our innovative combination of microfluidic experiments and pore-scale modeling opens new possibilities to validate and identify relevant pore-scale processes, providing data for upscaling approaches to derive key relationships for continuum-scale reactive transport simulations.