Ali Mese's dissertation
by
Ali Ihsan Mese, Ph.D.
University of Texas at Austin, 1995
Supervisors: Robert Schechter
Eric P. Fahrenthold
An experimental and theoretical investigation of water content and stress effect on mechanical, chemical and
failure properties has been conducted using core samples from Barnett shale formation. Samples showed plastic
deformation almost immediately with the initiation of loading. Therefore, in addition to the elastic static moduli,
components of the plastic tangential compliance tensor were also obtained from triaxial stress cycling measurements
for dry, partially saturated and fully saturated shale samples. Simultaneous measurements of compressional and shear
wave velocities were carried out using pulse transmission technique in order to obtain the corresponding dynamic
moduli. Static and dynamic Young's moduli decreased greatly in all Barnett shales tested with an increase in saturation
and increased with increasing [sic] at failure. The comparison of the experimental results with various failure
surfaces indicated that partially and fully saturated shale samples are best represented by the Drager-Prager equation
as compared to the von Mises, Mohr-Coulomb and Cap failure surfaces.
A new saturation device was designed based on chemical potential theory in order to control saturation in the shale
samples used. The method also helps to conduct measurements with strain-gauged shale samples which has not been successful prior to this work.
A modified intermolecular force model is presented that provides a quantitative analysis
of how intermolecular forces influence
the expansion of clays and shales. Determination of electrostatic repulsion parameters from cation
exchange capacity and specific surface area
is described. Equilibrium is considered determined by the van der Waals attraction and electrostatic
repulsion. Initial and equilibrium separation distances are calculated.
Relations obtained between salt concentration, plate thickness and swelling which is calculated from
initial and equilibrium separation
distances agree reasonably well with available experimental swelling and swelling pressure data.
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