Modeling maximum offsets for 2D/3D seismic survey designing- A Simple Python Tool

While designing/modeling for 2D/3D seismic surveys to record P or PS wave data, reflection ray paths of layered (interval) velocity model (based on existing wells or seismic) suggest more optimized ranges of offsets required to image the target depths rather than using empirical rules of thumb e.g. Max. offset = Max. Depth of target etc. Ray paths modelled using simple Snell’s law gives the ranges of angle where the reflections will reach the surface for a given velocity model. Moreover, it would also suggest limiting the largest offset beyond which the reflection strength drastically drops i.e. at the critical angle of refraction for a given target.

Figure-01 shows the relation of reflections arrival of different input incident angles at target depth with the relevant surface offsets. You can note the critical angle in zoomed part in Figure-02, where the energy is critically refracted. The surface offset for angles lower than this critical angle should be considered for designing of maximum offset for 2D/3D seismic surveys. (The results are based on Python code by the author)