Application of the seismic quality factor versus offset and azimuth (QVOA) for fractured reservoir characterization
Fractures impact the permeability of a reservoir and their characterization is important because the presence of fractures determines the flow of hydrocarbons during production. Accurate modelling of the fracture network can help in optimizing the production of the reservoir. Fractures affect the amplitudes of seismic waves; therefore, seismic attenuation is used to determine their characteristics. Here, a new technique of seismic fracture characterization is employed. QVOA, which involves the evaluation of the seismic attenuation (Q) and its variation with offset (O) and azimuth (A). The QVOA method is a two-step process where seismic attenuation is computed first and then its variation is determined with respect to offset and azimuth. We compute seismic attenuation using four different techniques based on the spectral ratio and frequency-shift methods. The variation with respect to offset and azimuth is determined using an approximate method of sectors (ASM) and approximate truncate method (ATM). The QVOA method is similar to the AVOA method for PP-reflection (Rüeger, 1997) since it includes intercept (A), gradient (B) and fracture orientation.