Q -factor estimation in CMP gather and the continuous spectral ratio slope method

The attenuation factor or quality factor ( Q -factor or Q ) has been used to measure the energy attenuation of seismic waves propagating in underground media. Many methods are used to estimate the Q -factor. We propose a method to calculate the Q -factor based on the prestack Q -factor inversion and the generalized S-transform. The proposed method specifies a standard primary wavelet and calculates the cumulative Q -factors; then, it finds the interlaminar Q -factors using the relation between Q and offset (QVO) and the Dix formula. The proposed method is alternative to methods that calculate interlaminar Q -factors after horizon picking. Because the frequency spectrum of each horizon can be extracted continuously on a 2D time–frequency spectrum, the method is called the continuous spectral ratio slope (CSRS) method. Compared with the other Q -inversion methods, the method offers nearly effortless computations and stability, and has mathematical and physical significance. We use numerical modeling to verify the feasibility of the method and apply it to real data from an oilfield in Ahdeb, Iraq. The results suggest that the resolution and spatial stability of the Q -profile are optimal and contain abundant interlaminar information that is extremely helpful in making lithology and fluid predictions.