Long period multiple attenuation by subtraction of the multiple stack

Abstract

Contamination of astacked section by long period multiples often arises because the multiples possess a high amplitude relative to the underlying primary reflections. A multiple suppression technique is presented which makes use of both the difference in moveout between primary and multiple reflections, and the difference in amplitude. When multiples possess a consistent character across a CMP gather an estimate of the average multiple content may be obtained by stacking, following the application of an appropriate moveout correction to transform the multiple to a horizontal event. The moveout correction may be applied to an approximately hyperbolic event where the apex lies at non-zero offset to allow pegleg multiples to be estimated in this fashion. Subtraction of the stacked trace from each trace in the CMP gather will significantly reduce the amplitude of the multiple energy present. The remaining multiple energy will be less coherent and more readily suppressed by the primary stack.