Abstract:

Recent laboratory experiments in an intermediate-scale Hele-Shaw cell, designed to represent a coarse sand aquifer, demonstrate that mixing-induced calcite precipitation leads to the formation of a self-organized, heterogeneous porous medium. This morphology, characterized by elongated carbonate structures and internal preferential flow channels, induces strong anomalous transport features, including early solute arrival, distinct double-peak breakthrough curves, and pronounced tailing. In this article, we investigate the link between this precipitation-induced heterogeneity and solute transport by implementing varying permeability scenarios, derived from experimental image analysis, into a transport model. Our analysis reveals that while a standard dual-permeability approach, which simply delineates the total precipitated area, captures the flow diversion responsible for the emergence of the double peak, it fails to reproduce the transition between peaks and the late-time tailing. To address this, we introduce a novel triple-permeability model that incorporates internal preferential flow channels within the high-precipitation zones. By resolving the internal structure of these zones, the triple-permeability model accurately captures the dual-peak transition and tailing behavior. These findings provide critical insights for applications such as geological carbon sequestration and enhanced oil recovery. Although determining exact internal structures in field settings is challenging, our results demonstrate that effective transport models must account for the internal heterogeneity of high-precipitation zones, rather than treating them as uniform barriers, to accurately predict the channeling effects that govern injectivity and long-term storage security.

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