Wave Velocities in carbonate rock specimens of a hydrocarbon reservoir in the south of Iran

In this research, effects of different parameters on elastic wave velocities were assessed for eight carbonate rock specimens and different theories applied to laboratory data. Ultrasonic measurements were made on the samples in both dry and saturated states. Pore pressure of fluid (kerosene) was kept constant at 5MPa and the range of effective pressures was from 5MPa to 60 MPa. Central wave frequency of P-wave was I MHz and that of S-wave 0.6 MHz. All the experiments were carried out in room temperature. The results show that by saturating the samples, P-wave velocities will increase but S-wave velocities show negligible changes. An increase in effective pressure causes the velocities to rise in both dry and saturated states, though the rate of P-wave velocity increase is more than that of S-wave. Results also show that wave velocities will increase by increasing the density or decreasing the porosity. We applied Gassmann and Biot theories to the laboratory data. The results showed that these theories were in agreement with the results of ultrasonic measurements. Gassmann deviation was between -3% and +1%. Biot dispersion for P- and S- wave velocities was less than 0.3 and 0.5 percent, respectively. We also concluded that wyllie´s time average equation did not show a good agreement with the laboratory data