Colin Sayers received a BA in Physics from the University of Lancaster, U.K., a DIC in Mathematical Physics, and a PhD in Physics from Imperial College, London, U.K. He joined Shell’s Exploration and Production Laboratory in The Netherlands in 1986, moving to Schlumberger in 1991. He retired from Schlumberger in May 2020 and currently holds a position as Adjunct Professor in the Department of Earth and Atmospheric Sciences, University of Houston. He is a member of AGU, APS, 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. 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. His research interests include unconventional resources, seismic solutions, rock physics, pore pressure prediction, reservoir geomechanics, time-lapse seismic, analysis of production-induced reservoir stress changes, subsidence, fault reactivation, 3D mechanical earth modeling, fractured reservoir characterization, AVAZ, borehole/seismic integration, stress-dependent acoustics, and advanced sonic logging.
SEG Best Paper in The Leading Edge Award 2013
Cengiz Esmersoy, Arturo Ramirez, Sharon Teebenny, Yangjun Liu, Chung-Chi Shih, Colin Sayers, Andy Hawthorn, and Maurice Nessim received 2013 SEG Best Paper in The Leading Edge Award for their paper A new, fully integrated method for seismic geohazard prediction ahead of the bit while drilling.
2010 SEG/EAGE Distinguished Instructor Short Course
Geomechanical Applications of Seismic and Borehole Acoustic Waves
The state of stress within the earth has a profound effect on the propagation of seismic and borehole acoustic waves, this leads to many important applications of elastic waves for solving problems in petroleum geomechanics. The purpose of this course is to provide an overview of the sensitivity of elastic waves in the earth to the in-situ stress, pore pressure, and anisotropy of the rock fabric resulting from the depositional and stress history of the rock, and to introduce some of the applications of this sensitivity. The course will provide the basis for applying geophysics and rock physics solutions to geomechanical challenges in exploration, drilling, and production. A variety of applications and real data examples will be presented, particular emphasis will be placed on the rock physics basis underlying the use of geophysical data for solving geomechanical problems.
The following topics will be addressed in the course:
- Introduction to the effects of stress in the earth. Why pore pressure, in-situ stress and geomechanical properties are important.
- Sediment compaction and the state of stress in the earth. Vertical stress, pore pressure and sediment compaction. Horizontal stress in a relaxed basin. Estimation of the minimum and the maximum horizontal stress. Tectonic strains.
- Pore pressure. Velocity vs. effective stress relations. Pore pressure estimation from velocity. Clay diagenesis. Unloading. The need for fit-for-purpose seismic velocities. Uncertainty analysis. Combining seismic velocities with well velocities for improved pore pressure estimation. Dipping layers and lateral pore pressure transfer.
- Stress sensitivity of sandstones. Third-order elasticity theory. Dependence of elastic wave velocities on porosity in sandstones. The importance of compliant grain boundaries, microcracks and fractures on velocities in sandstones. The use of elastic waves to monitor stress-induced damage.
- Wellbore stability and wave velocities near a borehole. Stress changes in the vicinity of a borehole. Mechanical behavior of rock in the vicinity of a borehole. Stress dependence of elastic wave velocities. Linearized expressions for the change in velocity for small changes in stress.
- Reservoir geomechanics and 4D seismic monitoring. Reservoir stress path. The effect of stress path on rock deformation and failure. Rock failure. Monitoring reservoir stress changes using time-lapse seismic. The difference in reservoir stress path between injection and depletion.
- Fractured reservoirs. Effects of fractures on seismic waves. Multiple fracture sets. Amplitude Versus Offset and Azimuth (AVOA). Simplifications for weak anisotropy. Effects of inequality between the normal and shear compliance of fractures. Microstructural models of fracture compliance.
- The seismic anisotropy of shales. The relation of shale anisotropy to microstructure. The effect of interparticle regions on seismic anisotropy. Clay mineral anisotropy. Effect of disorder in the orientation of clay particles. The static elastic moduli for a TI medium and the implications for hydraulic fracture containment.
The accompanying textbook is available for purchase.
An article about the course was published in The Leading Edge.
A recording (online streaming version) of this course also is available.