Seismic imaging and migration velocity analysis of Alberta Foothills structural data sets

Seismic imaging of complex structures from the Alberta Foothills can be achieved by applying the closely coupled processes of prestack depth migration (PSDM) and migration velocity analysis (MVA). To address the main issues affecting the final PSDM imaging quality in the Shaw-Basing area of the central Alberta Foothills, both modeling studies and field data investigations were performed to find optimal processing strategies and imaging procedures for handling rugged topographic relief, complicated near-surface velocity variations, complex structural geology with velocity heterogeneity, and seismic anisotropy of steeply dipping clastic overburden.; The imaging comparisons of three typical foothills numerical models, triangle zones, box olds, and pop-ups, show that PSDM from topography using the existing migration algorithms is sufficient and robust in imaging the complicated structural geology and in distinguishing similar geometric structures only if the actual velocity model is available.; A newly developed common-shot gather migration velocity analysis based on the curvature measurement and stacking power was numerically analyzed and successfully applied on the triangle zones numerical modeling data set with and without random noises. When compared with the methods of common-offset MVA and depth-focussing MVA, this technique was demonstrated to be effective and accurate in estimating a velocity model for PSDM.; Field data from a 2D surface seismic survey acquired in the central Alberta Foothills were processed using a wisely designed processing scheme to yield an optimal depth image. With the reliable static derivations and reasonable near-surface velocity structures, PSDM from different surfaces were carried out systematically. The agreement between the PSDM image and well information confirms the validity of the proposed imaging strategies.; To understand the effect of seismic anisotropy on the PSDM images, the techniques of velocity analysis for building an anisotropy model ( V₀, &egr;, δ, &thetas;) were developed. When applied on the TTI numerical modeling data, the integration of NMO inversions and parameter scanning was shown to be robust and was justified in addressing the issue of anisotropic parameter ambiguities. Field data investigations demonstrated that the method employed for building an anisotropy velocity model was effective based on the overall imaging improvements of the reservoir target and structural features.