Abstract
On the basis of conventional surface seismic data, the 13-15-63-25W5M exploratory well was drilled into a low-relief Leduc Formation reef (Devonian Woodbend Group) in the Simonette area, west-central Alberta, Canada. The well was expected to intersect the crest of the reef and encounter about 50-60 m of pay; unfortunately it was drilled into a flank position and abandoned. The decision to abandon the well, as opposed to whipstocking in the direction of the reef crest, was made after the acquisition and interpretive processing of both near- and far-offset (252 and 524 m, respectively) vertical seismic profile (VSP) data, and after the reanalysis of existing surface seismic data.The near- and far-offset VSPs were run and interpreted while the drill rig remained on-site, with the immediate objectives of: (1) determining an accurate tie between the surface seismic data and the subsurface geology; and (2) mapping relief along the top of the reef over a distance of 150 m from the 13-15 well location in the direction of the adjacent productive 16-16 well (with a view to whipstocking). These surveys proved to be cost-effective in that the operators were able to determine that the crest of the reef was out of the target area, and that whipstocking was not a viable alternative. The use of VSP surveys in this situation allowed the operators to avoid the costs associated with whipstocking, and to feel confident with their decision to abandon the well.
