西南石油大学学报(自然科学版)

Previous Articles     Next Articles

Estimating Quality Factor Q with Time-domain Centroid Frequency Shift Method

Yu Lianyong1, Fan Ting´en1, Hu Guangyi1, Cao Siyuan2, Wang Zongjun1   

  1. 1. CNOOC Research Institute,Dongcheng,Beijing,100027,China
    2. CNPC Key Laboratory of Geophysical Exploration,China University of Petroleum(Beijing),Changping,Beijing 102249,China
  • Online:2014-08-01 Published:2014-08-01

Abstract:

The quality factor Q is the parameter that characterizes seismic wave energy attenuation caused by underground medium,and it is a key parameter in reservoir predication and hydrocarbon detection. Centroid frequency method is a common method to evaluate quality factor,which has high precision and stability. But this method needs calculation of the centroid frequency and bandwidth of spectrum,which mainly relies on the quality of seismic spectrum. To avoid extraction of wavelet spectrum,time-domain centroid frequency shift method(TCFS for short)is put forward. This method estimates the quality factor by calculating the centroid frequency and bandwidth of seismic wavelet in time domain. Centroid frequency of spectrum of constant-phase wavelet is the instantaneous frequency of its envelope at the peak,and Gauss window 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,and 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.

Key words: time domain, centroid frequency shift, quality factor, instantaneous frequency, band width