Delineation of thin conglomerate deposits using multicomponent seismic data

Abstract

Multicomponent surface seismic acquired in the Carrot Creek oilfield of West Central Alberta shows a strone radial component (P-SV) amplitude anomaly at the locatioi of oil-producing conglomerate deposits. The vertical component comparatively exhibits only a subtle amplitude variation at the same location. The Canlium conglomerate in this area was found to have a P-wave velocity of 4300 m/s and a Poisson’s Ratio of between 0.18 and 0.22. Over and underlying the conglomerate are thick shale deposits having P-wave velocities of 3900 and 4000 m/s respectively, and a Poisson’s Ratio of 0.3 1. AVO forward modeling, shows a polarity reversal with offset occurring on the vertical (P-P) but not the radial (P-SV) component for the conglomerate vent The AVO responses were also found to be highly dependent upon the conglomerate thickness, decreasing AVO response occurs with decreasing thickness. It is the polarity reversal on the vertical (P-P) component which causes the poor amplitude response at the location of the Cardium conglomerate. Upon stacking, the near and far-offsets of the vertical component add destructively whereas the radial component offsets add constructively, thus causing the Cardium conglomerate obe mote easily seen on the radial component section.