3D fracture assessment using AVAz and a layer-stripping approach

Abstract

Subtle variations in P-wave multi-azimuthal seismic reflections can be used to map lineations in a horizon, representing seismic amplitude changes resulting from the presence of vertical fractures. This paper studies the phenomenon of P-wave propagation through vertically fractured media under controlled laboratory conditions, and shows how resulting amplitude maps can be used to predict fractured layers. A scheme of layer-stripping, based on Ruger's reflection coefficient approximations, can reduce the overburden effect on reflection amplitudes of underlying layers. By removal of overburden transmission effects, greater clarity is achieved in mapping any deeper fractured horizons. The effect of fractures is examined using physical model data, and the technique is demonstrated using field data.