Estimation of uncertainty in sonic porosity using microcomputerized tomography images

• Microcomputerized tomography is used for resolving pore and grain morphology.
• Uncertainty in Wyllie equation has been estimated for Berea sandstone.
• Wyllie equation is corrected for the error due to mean pore size.
• Accuracy of Wyllie equation is improved using micro-CT simulations.
• Useful for precise characterization of reservoir rock properties.

Acoustic log uses sonic wave characteristics and transit time for the determination of porosity, lithology, and mechanical properties. Pearson correlation coefficients show velocity to be strongly dependent on porosity, mean pore size and its sphericity. Wyllie equation is widely used for relating compressional velocity and porosity. The equation does not consider effect of pore, grain morphology which makes it simple, but results in significant uncertainties. It underestimates velocity of Berea sandstone compared to computed velocities from microcomputerized tomography simulation. An increase in accuracy of Wyllie equation has been observed when correction related to effect of average pore size is incorporated.