Advanced Failure Analysis in Geomaterials: Application to Reservoir Geomechanics
Abstract
The manifestation of failure in geomaterials and its proper analysis are constitutive
aspects that geotechnical engineers are faced with routinely in design. In most
instances, geostructures are examined at the ultimate plastic state where failure
is deemed to occur along a slip surface where plastic deformations localize. This
plasticity condition is classically analyzed with the Mohr-Coulomb failure criterion.
However, other forms of failure also exist where the localization of deformations
is totally absent such as in the case of static liquefaction. This distinct
mode has been coined as ‘diffuse failure’ which has the peculiarity of occurring at
stress levels well below the plastic limit, thus rendering a classic Mohr-Coulomb
analysis insufficient. Hence, the signature of failure in geomaterials seems to be
directly related to two principal modes by which it is manifested: one with localized
slips, and another variant where deformations are diffused without any
localization phenomena. In order to address the many subtle features of failure, a clear mathematical
representation of the underlying physical phenomena is needed. In this thesis,
failure is considered as an instability of homogeneous deformations, and as such
the observed failuremode is a direct result of the underlying constitutive equations admitting bifurcations in solutions for the material response. Different failure criteria
are derived, serving as failure indicators which signal the various modes that
emerge during loading history following a certain hierarchy. To translate theory into engineering practice, the thesis endeavors to apply
the above mathematical aspects of failure in the study of geomaterials undergoing
multiphasic flow and thermal transport such as in the extraction of heavy oil
from an oilsand reservoir in Alberta, Canada. Governing equations describing the
physics of all phases (solid, water, gas and oil) involved are formulated within
mixture theory using continuum mechanics principles. A special computational
strategy is adopted to solve efficiently the coupled system of equations using both
finite elements and finite differences. Finally, the developed computational model
is tested in the context of an actual oil field case study implicating steam injection
and oil production in an oilsand reservoir in Alberta, Canada. To close the loop,
attention is obviously focused on material failure concepts developed in the first
part of the thesis. Geomechanical properties that enter the computational model
are obtained from a separate comprehensive laboratory testing of shales and oilsands
at high temperature and pressure.
Description
Keywords
Engineering--Civil
Citation
Gong, X. (2017). Advanced Failure Analysis in Geomaterials: Application to Reservoir Geomechanics (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/24722