Microfracturation in rocks: from microtomography images to processes

Fracturing of rocks and other geomaterials involves multi-scale processes, from the nucleation of small cracks, their propagation into a complex heterogeneous solid, to their final arrest. In the past 10 years, advances in X-ray tomography imaging techniques, either three dimensional or four dimensional when time-lapse acquisitions are performed, allow detecting fractures at small scale and the growth and coalescence of tiny cracks into well-developed fractures. Some of these fracturing processes involve the coupling between fluids, chemical reactions and fracturing. In the present study I illustrate some of these processes, how they can be imaged using high-resolution X-ray computed tomography; and how conceptual models can make the link between microscopic processes and macroscopic fracturing. This concerns a wide range of applications in geophysics, from fundamental understanding of the rheology of rocks in the Earth’s crust, to salt damage of cultural heritage monuments, hydraulic fracturing of underground reservoirs or emerging technologies of non-conventional hydrocarbon recovery and the underground geological storage of carbon dioxide