ARMA UToronto Student Chapter Talk: Prof. Nicola Tisato & Mr. Omar Alamoudi

Title: Attenuation of Seismic Waves

Short Bio: Prof. Nicola Tisato

Nicola Tisato is an experimental rock physicist who combines and proposes new methods to understand natural processes. Since 2016, he has been an assistant professor at the department of geological sciences of The University of Texas, where he is the principal investigator of the Rock Deformation Laboratory. In 2013, under the supervision of Dr. Burlini and Dr. Burg (ETH Zurich), Nicola received his Ph.D. concerning the attenuation of seismic waves in saturated rocks. Nicola has an M.Sc. from the University of Padova (supervisor Prof. Di Toro), and in 2014-2015 he was a post-doc at the University of Toronto (supervisor Prof. Grasselli).

Abstract

Subsurface exploration relies on geophysical methods and the physical properties of rocks and saturating fluids. In the case of seismic tomography, the knowledge of rheology is pivotal to infer the structure and the content of subsurface domains. Nonetheless, geophysicists often treat geo‐material as elastic or nearly-elastic overlooking the role of frequency-dependent attenuation in absorbing seismic energy. I will introduce anelasticity in saturated rocks and magmas and how fluids can produce frequency-dependent attenuation and dispersion. Focusing on sandstones saturated with different portions of gas and liquids, I will present laboratory experiments performed to investigate wave‐induced‐gas‐exsolution‐dissolution and how these attenuation mechanisms could be modelled, revealing details of the subsurface.

Title: Fracture Detection in CT-scans

Short Bio: Mr. Omar Alamoudi

Omar Alamoudi is a PhD student at the Rock Deformation Lab, Jackson School of Geosciences at The University of Texas at Austin. His research is in building and utilizing hydraulically actuated X-Ray transparent tri-axial testing apparatuses. His research's primary objective is to understand how fracturing shale rock samples affects their hydraulic permeability over time. Previously, Omar completed his Master's degree at Stanford University in Geophysics. Before which, Omar worked in Saudi Aramco in geophysics for four years with experience in seismic data acquisition, seismic data processing, seismic data interpretation, geological modeling, and rock physics feasibility studies.

Abstract

Rock deformation experiments are often limited to measuring the kinematic properties of the rock sample. This introduces uncertainties to properly characterizing the deformation of the rock samples. We overcome such limitations by deforming and X-ray imaging rock samples during tri-axial experiments allowing the sample visual inspection. We are interested in understanding how fracturing a rock sample affects its permeability. Thus, it is fundamental to detect and measure fracture properties from microCT images.

Detecting and measuring fractures that propagate over time is challenging. Therefore, we need to produce a methodology that consistently measures fracture properties of time-variant sample images. Here we evaluate and utilize a Multi-scale Hessian Fracture Filtering (MSHFF) technique (Voorn et al. 2013) on synthetic images of fractures and two instances of microCT images of a rock sample. We find that the MSHFF is successful in enhancing and detecting fractures. In addition, this technique reduces further beam hardening of microCT images even when measures to reduce such an artifact were taken during acquisition. Finally, using MSHFF, we improved the fracture surface area estimate of microCT images of a rock sample that was fractured in a rotary shear experiment.