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A B S T R A C TWe have developed a straightforward and ray based methodology to estimate both the maximum offset and reflection imaging radius for multi-layered velocity models, which can be used for a 2D/3D VSP survey design. Through numerical examples, we demonstrate that the presence of a high-velocity layer above a target zone significantly reduces the maximum offset and reflection imaging radius. Our numerical examples also show that including in a migration VSP data acquired beyond a recommended maximum offset, radically degrades the quality of the final VSP image. In addition, unlike the conventional straight-line based approximation that often produces an incorrect large reflection imaging radius, our methodology predicts the VSP imaging radius with more accuracy than does the conventional approximation.

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