The Theory and Application of Layer Q Inversion Based on VSP Data

Abstract

According to the compensation principle of surface energy consistency, this paper described a method to eliminate the difference of the excitation energy in zero-offset VSP data, and then use the FK method to separate the down-going wavefield with amplitude preserved processing. Through the analyzing of the difference of amplitude spectra between selected down-going wavefield and monitoring wavelet, we removed the variation of source wavelet in the Q inversion results. After combined with the analytical method, we obtained reasonable equivalent Q values. Based on the relationship between layer Q and equivalent Q, we achieved the stable layer Q values. By working through the contrast between the estimated layer Q and interval velocity, and the results of inverse Q filtered to VSP and near-well surface seismic data for amplitude compensation, we have achieved following improvements: (1) the inversed layer Q and layer velocity are very similar; (2) inverse Q filtering broadened the data spectrum, enhanced the dominant frequency, and improved the seismic resolution greatly; (3) the real data examples showed that this layer Q inversion method is reasonable, effective and stable.