Seismic Imaging of Converted Waves in the Presence of Significant Overburden: A Modelling Study

Overburden layers continue to be a problem for recording and analyzing information in seismic surveys. This study aims to examine the effects of overburden layers on seismic wave propagation and imaging. In the investigation, we look at the effect of low velocity, low density overburden on seismic imaging. To investigate this problem, a finite difference elastic wave modelling study was conducted to evaluate the effects of overburden layer when using 3component surface or borehole receivers. The study compares the responses from a lenticular inclusion in a 2D background model with and without an overburden layer. The relatively slow Pwave and S-wave velocity of the overburden material impacts the travel time and the shape of the wave. As expected with borehole receivers, only the first few traces from shallow receivers are corrupted by highly dispersed surface waves. Deeper receivers from the borehole acquisition (Vertical Seismic Profiling-VSP) show clearer reflections from the sulfide lens than similar records from the surface receiver spread. The location of the shot also affects the seismic response depending on whether it originates inside the overburden or below.