EICP-enhanced fracture healing: bridging microfluidic observations and macroscale applications

Bio-mediated carbonate precipitation is crucial in mineral formation and geological evolution, with enzymatically induced carbonate precipitation (EICP) gaining attention for its potential in fracture healing. In this study, the effectiveness of EICP technique was explored in healing fractures across micro-to-macro scales. The pore-scale healing process of real rock fractures was observed in rock-based micromodels. Heterogeneous nucleation sites tended to form on the rock interfaces and subsequently facilitate crystal growth. Moreover, the distribution of precipitates along an extended microchannel was analysed to examine the micro-scale non-uniformity issues related to biocementation. The interaction between flow dynamics and precipitation was employed to interpret the mechanisms underlying fracture healing by way of biocementation. For a broader macro-scale perspective, temporal–spatial distribution of precipitates was visualised by conducting grouting tests within an artificial fracture between transparent glass plates, recorded through time-lapse photography. These visual findings were further validated through column-scale tests involving fractured limestone rock samples, showing that precipitated calcium carbonate (CaCO3) reduced permeability reduction and caused pore clogging. By cross-referencing microfluidic findings with outcomes of macro-scale experiments, the study demonstrates the consistency of size-scale and continuity of time-scale effects across various scales, enhancing the comprehension of the EICP process across various scales, and validating the potential of biocementation in fracture healing.