VSP (Walkaway) for accurate target location

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When surface seismic is missing or of low quality, a very accurate structural and stratigraphic interpretation can be created by using the upper portion of a partially drilled well to place a geophone array for use in conducting a walkaway VSP. The results of this VSP can be then used to more accurately reinterpret the structure to allow the drilling plan to be redirected. This is particularly useful in drilling horizontal wells to accurately find the “landing zone” and to avoid structural faults unseen by surface seismic.