Abstract:
Geomechanical parameters of rocks are essential for understanding their elastic behavior. These parameters find their applications in various fields such as petroleum engineering, and geological studies related to formations and underground layers. There are several methods to obtain these parameters, including experimental methods and modeling. Since most of geomaterials are highly heterogeneous in constituent components, detailed understanding of mechanical properties in a multi-scale (nano, micro, macro and field) is vital and can present various results. Macroscale methods such as unconfined/triaxial compression tests with the use of core plugs and logging data interpretation are commonly used to obtain mechanical properties. However, these methods have their own limitations. Thus, to address the difficulty in the measurement of the mechanical properties of geomaterials, the advanced approach such as nanoscale: atomic force microscopy (AFM) and microscale: nanoindentation techniques were used. AFM and nanoindentation measurements were done both parallel and perpendicular to the bedding plane to examine mechanical anisotropy. Data were analyzed via multivariate statistical deconvolution technique (maximum likelihood approach and expectation–maximization algorithms) to reveal different mechanical phases, considering their Young’s modulus and hardness. Nano and microscale data first captured from clay rich shale geomaterial followed by, polyaxial compression tests on similar cubical core plugs to acquire modulus values in nano, micro and macroscale respectively.
The nanoindentation and AFM results are upscaled to the centimeter scale through the Mori-Tanaka (MT) method, Self-Consistent Scheme (SCS), Differential Effective Medium (DEM) theory, Kuster and Toksöz (KT)method and Dilute Model (DM). The upscaled results exhibit satisfactory fitting with the conventional polyaxail compression results, although the fitting of the upscaled AFM results is better than nanoindentation. Furthermore, thin section, XRD, and Rock-Eval pyrolysis enabled us to determine mineralogy, geochemical properties, and intrinsic structure of the studied samples as the most important controlling factors on the elastic response of rocks.
The key findings of this investigation can provide reliable input data for multiscale geomechanical modeling in understanding engineering issues associated with unconventional reservoirs, e.g., shale gas, shale oil and coalbed methane, as well as engineering designs in shale or mudstone deposited strata.
Biography:
Dr.Ing. Hem Bahadur Motra is a highly accomplished researcher and academic specializing in geomechanics, rock physics, and geotechnical engineering at the University of Kiel, Germany. His professional journey reflects a deep commitment to advancing the understanding of subsurface processes through innovative experimental and computational approaches. He hold advanced degrees in civil and structural engineering and have completed extensive postdoctoral research in geotechnics, rock mechanics, and subsurface physics. As a research associate and head of the Geomechanics and Rock Mechanics Experimental Laboratory at Kiel University, He have contributed significantly to the study of the mechanical, thermal, and acoustic behavior of geomaterials under complex in-situ conditions. His multidisciplinary expertise bridges geosciences, civil engineering, and energy technologies, integrating rock physics, structural mechanics, and environmental sustainability. He have authored more than 70 scientific publications, including peer-reviewed journal articles, conference papers, and technical reports. His work has appeared in leading international journals such as the International Journal of Rock Mechanics and Mining Sciences, Applied Energy, Rock Mechanics and Rock Engineering, Scientific Reports, and Geotechnical and Geological Engineering, reflecting sustained contributions across geomechanics, rock mechanics, rock physics, energy, and geotechnical engineering. His extensive publication record spans top-tier journals, including International Journal of Rock Mechanics and Mining Sciences, Applied Energy, and Geotechnical and Geological Engineering. His research interests encompass multiscale geomechanical modeling, seismic anisotropy, CO₂ storage, geothermal energy, and the use of artificial intelligence in geological systems. He have led and collaborated on numerous national and international research projects funded by organizations such as DFG, DAAD, and the EU, focusing on sustainable infrastructure, rock deformation, and energy geotechnics. In addition to research, I serve as an influential editorial board member and special issue editor for several prestigious journals, contributing to the dissemination of cutting-edge developments in the field. His leadership in scientific committees, professional societies, and technical working groups further highlights my commitment to advancing interdisciplinary collaboration. Through his pioneering research, academic mentorship, and global collaborations, he continue to make impactful contributions to the scientific community, shaping the future of geotechnical and rock mechanics research and promoting innovative, sustainable solutions to address the challenges of modern engineering and Earth sciences.
