Modelling P-wave Velocity in Heavy-oil Sandstone and Its Application

Heavy oils have high densities and extremely high viscosities. Due to their viscoelastic behavior, traditional rock physics based on Gassmann theory becomes inapplicable. In order to determine P-wave velocity in heavy-oil sandstone after fluid substitution, P-wave velocities of three sandstone samples and one shale sample from the heavy-oil field are firstly measured under various temperature and oil saturation conditions. Based on these data a practical rock physics model is proposed. This rock physics model is then used to calculate the P-wave velocity after fluid substitution in the reservoir. The calculated velocity is then utilized in the generation of a synthetic seismogram. The match to the observed seismic data is greatly improved over the synthetic calculated from the sonic log measured before oil production.