Coupling dynamic in situ X-ray micro-imaging and indentation: A novel approach to evaluate micromechanics applied to oil shale. (15th September 2021)

• Record Type: Journal Article
• Authors: Voltolini, Marco; Rutqvist, Jonny; Kneafsey, Timothy
• Is Part Of: Fuel. Volume 300(2021)
• Publication Date: 2021-09-15
• Subjects: Green River Shale -- Ductile shale -- X-ray micro-tomography -- Micro-mechanics -- Brinell-type indentation -- Geomechanical modeling -- Proppant embedment; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2021.120987
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: A novel method for the characterization of micro-mechanics in shales is presented. Indentation experiments and synchrotron X-ray imaging have been combined. Mechanisms relevant for proppant embedment in ductile shales have been characterized. Improved experimental and modeling tools are now available for oil shale studies. Abstract: Oil and gas shales are a system where understanding the mechanical properties at the microscale is of paramount importance, e.g. to better understand the behavior of proppant-shale contacts and their role in the evolution of propped fractures in unconventional reservoirs. This work shows for the first time an experiment coupling indentation testing with in situ X-ray imaging in a Green River shale sample. A full compliance curve has been measured with the sample in water, allowing to visualize the indentation of the sample in function of axial load, in a purpose-built system for combined in situ indentation and X-ray imaging. A series of 3D datasets were used for a digital volume correlation study to obtain local strain fields. This analysis has been complemented with the analysis of cracks. Finally, geomechanical modeling has been carried out to replicate and generalize the observed behavior in the shale. This study validated this experimental approach, providing a breakthrough in understanding micro-mechanics in shales, and demonstrates how this class of experiments can be important for studies involving the prediction of the evolution of propped fractures in shale reservoirs, with possible applications in a much larger number of application fields (geothermal, materials science, etc.)