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Speaker: Colin Sayers, Dept of Earth & Atmospheric Sciences, University of Houston
Co Author: Lennert D. den Boer, Consultant, Calgary, Alberta, Canada
The mechanical properties of sandstones, including porosity, density, and elastic moduli, can be estimated non-destructively using elastic wave-velocity measurements. Following the work of Eshelby (1957, 1961), many authors have sought to understand the elastic wave velocities in consolidated sandstones by assuming pores are ellipsoidal. However, results obtained with this assumption may be misleading since pores in sandstones are not ellipsoidal. For example, approaches that assume ellipsoidal pores agree with measured velocities only if the aspect ratio of ellipsoids is low. This follows from the fact that pores in sandstones are much more compliant than ellipsoidal pores. In this presentation, the variation of elastic-wave velocity with porosity in sandstones is studied using the simple model of Sevostianov and Giraud (2013) in which pores are represented as superspherical. Superspheres are defined by a shape parameter that allows the effect of pore concavity on elastic wave velocities to be investigated. Inversion of measured velocities for this parameter indicates that pore concavity decreases with decreasing porosity. Moreover, values of the shape parameter obtained by inverting measured P-velocities alone are found to give a good prediction of both P- and S-wave velocities, confirming the applicability of the model.
Speaker Biography: Colin Sayers, University of Houston
Colin Sayers received a B.A. in physics from the University of Lancaster, UK, and a D.I.C. and Ph.D. in physics from Imperial College, London, UK. He has previously worked for Shell in the Netherlands and the UK and for Schlumberger in the UK and USA. He currently holds a position as an Adjunct Professor in the Department of Earth and Atmospheric Sciences, University of Houston. He is a member of AGU, EAGE, GSH, SEG, and SPE, a member of the Research Committee of SEG, and has served on the editorial boards of the International Journal of Rock Mechanics and Mining Science, Geophysical Prospecting, and The Leading Edge. In 2010 he presented the SEG/EAGE Distinguished Instructor Short Course “Geophysics under stress: Geomechanical applications of seismic and borehole acoustic waves.” In 2013 he was awarded honorary membership of the Geophysical Society of Houston “in recognition and appreciation of distinguished contributions to the geophysical profession.” He shared an award for best paper in The Leading Edge in 2013.
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