4-dimensional in-situ/in-operando µ-CT imaging of geological processes at elevated temperatures and pressures using x-rays

Abstract

Micro-scale processes have a profound effect on geoenergy applications, ore formation, underground waste storage, geomechanics, and seismic and volcanic hazards. Understanding these processes is thus important for most of our societal interests in the geosphere. However, important aspects of these processes are still poorly understood. This is because replicating the ambient conditions, in particular high pressures and temperatures, in experiments remains challenging. The means to document progress during experiments are limited and, as a consequence, the results of classical 'black-box experiments', equipped only with indirect monitoring systems, are often inconclusive. In-situ imaging of geological processes in experimental studies allows the direct observation and quantification of grain-scale developments that define the macro-scale behavior of geomaterials,with the limitation of small sample sizes. In-situ imaging thus provides a possibility to overcome some of the limitations of classical experiments. Conducting such in-situ µ-CT experiments at the relevant conditions while simultaneously acquiring image data of sufficient quality comes with its own challenges, and extracting relevant quantitative information from the resulting image data remains difficult. Here we present an overview over our activities in that field over the past decade. We outline an array of bespoke x-ray-transparent experimental environments that can recreate a wide range of geological conditions, and demonstrate how previously inaccessible information is gathered from the resulting data using advanced image analysis with the open-source python library SPAM. We demonstrate that the technique promises to significantly advance our understanding of processes shaping the geosphere.

MIST – Mechanical In-situ Stage with Temperature control for X-ray computed tomography

“…Due to the vertical alignment (identical with rotation axis) of the 4-point flexural test setup, high resolution CT scans were enabled. Fusseis et al [7] developed a series of in-situ stages for the investigation of geoscience applications mainly at synchrotron sources over the past decade. Those stages are very modular, for two stages even blueprints are available [8,9].…”

Experimental and Numerical Perspectives on The Role of Localization and Heating in Small-Magnitude Earthquakes

“…Renard et al, 2020) and dehydration experiments (e.g. Fusseis et al, 2022). With this kind of setup, we could conduct incremental XCT scans for a single direct-shear setup and the entire sample (from one end to the other end), without taking apart the piston at different frictional stages.…”