Velocity Dispersion in Sandstones with Oil and Brine: Experimental Measurements and Theoretical Predictions

We measured ultrasonic P- and S-wave velocities of sandstone on 36 fine-grained and 14 medium-grained samples collected from Changyuan area of Daqing oilfield, northeast China at dry, full brine- and oil- saturated conditions. Relations between acoustic velocity and saturation were measured on 6 samples saturated with oil-brine mixture under hydrostatic pressure at 25MPa and pore pressure varying between 0.1 to 10MPa. The Biot-Gassmann theory was used in the analysis of velocity dispersion. Its predictions of P-wave in full-brine-saturated rocks were consistent with the measurements for most samples, whereas those of S-waves were less than measurements. Comparisons also show that Biot-Gassmann theory could be applicable for describing the changes of Vp with brine(oil) saturation in the oil-brine mixture-saturated sandstones.