Estimating quality factor Q by time-domain centroid frequency shift method

Abstract

Summary The quality factor is the parameter that characterizes seismic wave energy attenuation caused by underground medium. And it is a key parameter in the reservoir predication and hydrocarbon detection. Centroid frequency method is one of common methods to evaluate quality factor, which has high precision and stability. But this method needs the centroid frequency and bandwidth of spectrum, which mainly relies on the quality of seismic spectrum. Time-domain centroid frequency shift method (DCFS for short) directly estimates the quality factor according to calculating the centroid frequency and bandwidth of seismic wavelet in time domain. For constant-phase wavelet, its centroid frequency of spectrum is the instantaneous frequency of its envelope at the peak, and for Gauss window its bandwidth can be calculated by converting the envelope width (the product of them is constant).when seismic wavelet approximates to constant phase and Gauss window, we can calculate the centroid frequency and bandwidth in the time domain, then evaluate the quality factor according to the centroid formula, which avoids the extraction of seismic wavelet spectrum. The test of VSP down-wave model shows that the time-domain centroid frequency shift method is feasible and credible.