Rock fractures are of great practical importance to petroleum reservoir engineering because they provide pathways for fluid flow, especially in reservoirs with low matrix permeability, where they constitute the primary flow conduits. Rock fractures may also influence the propagation of hydraulic fractures, and understanding the spatial distribution of natural fracture networks is key to optimizing production in low permeability reservoirs. Properly processed, imaged, and well calibrated surface seismic can be used for obtaining information on the density and orientation of natural fractures, and the magnitude and orientation of the in-situ principal stress components which influence the aperture and hydraulic conductance of such fractures. The use of seismic AVOAz (Amplitude Variation with Offset and Azimuth) inversion to determine fracture density and orientation as well as horizontal stress anisotropy and the orientation of the principal stresses is described. A method for constructing a geologically realistic discrete fracture network (DFN), constrained by seismic amplitude variation with offset and azimuth (AVAz) data, will be presented. Upscaling then allows the anisotropic permeability and elastic stiffness tensor of the fractured reservoir to be determined from the DFN realization. The approach is illustrated using examples from the Middle East and North America.
Colin Sayers is a Scientific Advisor in the Schlumberger Seismics for Unconventionals Group in Houston. He entered the oil industry to join Shell's Exploration and Production Laboratory in Rijswijk, The Netherlands in 1986, and moved to Schlumberger in 1991.
His technical interests include rock physics, exploration seismology, reservoir geomechanics, seismic reservoir characterization, unconventional and fractured reservoirs, seismic anisotropy, borehole/seismic integration, stress-dependent acoustics, and advanced sonic logging.
He is a member of the AGU, EAGE, GSH, HGS, SEG, and SPE, a member of the Research Committee of the SEG, and has served on the editorial boards of the International Journal of Rock Mechanics and Mining Science, Geophysical Prospecting, and The Leading Edge. He has a B.A. in Physics from the University of Lancaster, U. K., a D.I.C. in Mathematical Physics and a Ph.D. in Physics from Imperial College, London, U. K. In 2010 he presented the SEG/EAGE Distinguished Instructor Short Course "Geophysics under stress: Geomechanical applications of seismic and borehole acoustic waves", and was chair of the editorial board of The Leading Edge. 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 received the award for best paper in The Leading Edge in 2013.