f Estimation of seismic attenuation from CMP gathers

The estimation of seismic attenuation is of prime importance in hydrocarbon exploration, but it has met with little success except to a certain extent in VSP studies. Different methods have been developed for measuring Q and in recent years Q has been successfully computed from VSPs (Tonn, 1991,Stainsby and Worthington,1985, Jannsen et al,1985) and the strengths and weaknesses of these methods have been documented. Estimation of Q from surface seismic data has not met with much success, maybe because of the multiplicity of ray-paths affecting both the elastic (reflection/transmission, geometric spreading etc.) and inelastic components of energy losses with offset. As well as this, surface seismic data is affected by NMO-stretch along with the usual problems of the presence of noise and multiples. In this presentation, a new scheme for computing Q (which is assumed to be constant within the frequency range of interest in hydrocarbon exploration) from cmp gathers is proposed. The method has provided accurate Q values when applied to models.