Previous Talks

Wednesday January 11, 2012

The Microporomechanics of Shale: From Nanoindentation to Macroscopic Prediction

J. Alberto Ortega, Schlumberger

Abstract

The links between the composition, microstructure, and multiscale mechanics of shale have long been enigmas that have deceived many decoding attempts from experimental and theoretical sides. Based on a combination of experimental nanotechnologies and micromechanics modeling, it was possible to deconstruct shale to the scale of an elementary unit with mechanical invariant properties and to upscale these behaviors from the nanoscale to the macroscale of engineering applications. The model development was validated at different length scales using novel experimental results from instrumented nanoindentation, electron probe microanalysis, as well as conventional macroscopic test results. The emerging understanding of the clay fabric in shale as a nanogranular composite translates into a unique poromechanics signature, in which the anisotropy derives from the intrinsic elasticity of the clay phase and is independent of mineralogy composition. For strength properties, the micromechanics approach revealed that the frictional behavior of the elementary unit of consolidated clay is scale independent, whereas size effects modify its cohesive behavior. The synergy of experimental nanomechanics and multiscale homogenization techniques presented in this work provides a viable framework for the modeling and prediction of mechanical properties of other natural porous composites.

Speaker Biography

J. Alberto Ortega is a Development Engineer for the Schlumberger Pressure Pumping and Chemistry Group in Sugar Land, Texas. He received his B.S. degree in Civil Engineering from Texas A&M University in 2002, and his S.M. and Ph.D. degrees from the Department of Civil and Environmental Engineering at MIT in 2006 and 2010. He joined the GeoGenome Industry Consortium led by Profs. F.-J. Ulm (MIT) and Y. Abousleiman (University of Oklahoma) in 2006, where he was responsible for the development of micromechanics-based poroelastic and strength predictive models for sedimentary rocks, with a particular emphasis on shale. His research focuses on granular mechanics, multi-scale modeling of geomaterials, and experimental nanochemomechanics.