Ultrasonic P and S Wave Velocities in Carbonates from the Arab Formation and Western Canada Sedimentary Basin

摘要

Understanding the effects of porosity, pore type, saturation and pressure on the elastic properties of reservoir rock is essential for the adequate interpretation of seismic reflection amplitudes and amplitude versus offset responses. Most studies to understand these effects have been carried out on sandstones. However, the same models are generally felt to be not applicable to carbonate rocks. In this study we have measured the compressional and shear velocities and the quasi-static strains for carbonate samples in both dry and saturated conditions under different hydrostatic pressures. The samples show general increase in velocities with increasing pressure. Samples with low porosity show less velocity variation with pressure increase. The dry compressional velocities increased with water saturation whereas the dry shear velocities decreased in the porous samples. These observations appear to be in accordance with Gassmann s theory. in these rocks Gassmann s low frequency relation appears to adequately describe the S-wave velocity but significantly overestimates the P-wave velocity. Preliminary result of static and dynamic bulk moduli are shown.