Quality factor extraction using instantaneous frequency at envelope peak of direct waves of VSP data
利用VSP资料直达波的包络峰值处瞬时频率提取介质品质因子

In the work,employing a function with four undetermined parameters to model the source wavelet,an analytical relation between Q-factor and envelope peak instantaneous frequency(EPIF)is derived from the theory of one-way waves propagating in an anelastic medium;at the same time,a method for extracting instantaneous frequency(IF)in wavelet domain is developed for improving the precision and anti-noise performance of IF estimation,and based on these,a method called EPIF in wavelet domain(WEPIF)is proposed for estimating Q-factor of VSP data.Test of synthetic zero-offset VSP data indicates that,comparing with logarithm spectral ratio method and centroid frequency shift method,WEPIF method is more stable and precise,and less sensitive to interface reflection waves.The Q-factors of single-shot zero-offset VSP data of 6-series from a certain gas field is estimated by WEPIF method,and the result shows that the extent of absorption corresponds well to the gas saturation of reservoirs.