Cap rock integrity is an essential characteristic of any reservoir to be used for long-term CO 2 storage. Seismic AVOA (amplitude variation with offset and azimuth) techniques have been applied to map HTI anisotropy near the cap rock of the Weyburn field in southeast Saskatchewan, Canada, with the purpose of identifying potential fracture zones that may compromise seal integrity. This analysis, supported by modeling, observes the top of the regional seal (Watrous Formation) to have low levels of HTI anisotropy, whereas the reservoir cap rock (composite Midale Evaporite and Ratcliffe Beds) contains isolated areas of high intensity anisotropy, which may be fracture-related. Properties of the fracture fill and hydraulic conductivity within the inferred fracture zones are not constrained using this technique. The predominant orientations of the observed anisotropy are parallel and normal to the direction of maximum horizontal stress (northeast-southwest) and agree closely with previous fracture studies on core samples from the reservoir. Anisotropy anomalies are observed to correlate spatially with salt dissolution structures in the cap rock and overlying horizons as interpreted from 3D seismic cross sections.

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I've been fortunate to have received advice and assistance from many people for this study. I'm particularly grateful for the excellent supervision of Don White and Claire Samson who provided a challenging project opportunity and ensured its success. My thanks to Barbara Dietiker for her advice and assistance with software and for always answering unexpected drop in questions. Thanks also to Steve Hall, for his assistance with AVOA analysis and recommendations for methodology. This study benefits greatly from his expertise and input. I enjoyed my stay in Bristol and am grateful to Mike Kendall and James Wookey for providing modeling software and their insight. Modeling would not have been possible without their contribution. Thanks also to James Verdon for his help with CO2 properties for modeling. I've spent much of this project taxing the resources of the GSC which made the seismic processing and inversion portion of this study possible. I'd like to thank Gilles Bellefleu for answering many questions and for his advice on true amplitude processing. My thanks to Jun-Wei Huang for his input on uncertainty analysis. Thanks to Brian Roberts for his help with ProMAX and for dropping Don off the license server for me. I'd like to thank Cenovus for providing the Weyburn field data and David Cooper for his insight and processing recommendations. Thanks to the PTRC for providing funding and the opportunity to present at the PRISM CCS meetings. I'd also like to thank the Ontario Graduate Scholarship, Natural Resources Canada, Society of Exploration Geophysicists, Canadian Society of Exploration Geophysicists (CSEG) and Canadian Exploration Geophysics Society for their support (KEGS).