Seismic anisotropy and salt detection: A physical modelling study

Zandong Sun, R. James Brown, Donald C. Lawton

Salt has been of considerable interest in petroleum exploration in western Canada. Identifying and separating salt remnants from reefs on seismic sections is of great concern for petroleum explorationists. In this physical modelling study, zero-offset transmission experiments have been undertaken on three different types of salt and salt-correlated anhydrite. Velocity of a salt sample under different pressure and temperature also has been tested. Pure salt and recrystallized salt have been found to exhibit shear-wave splitting. However, impure salts (salt mixed with clay, sands, etc.) show no shear-wave splitting. Theoretically, the wave (group-velocity) surfaces indicate that there should be only a single shear-wave velocity along principal (symmetry) axes. The minimum value of P-wave velocity and the maximum difference between qSV and qSH velocities axe in the (1,1,0) direction in the first quadrant. Seismic anisotropy should be able to help us to identify pure salt and recrystallized salt, and anisotropy in anhydrite may provide indirect information about the evaporite sequence. There is little velocity change in salt with changes in pressure and temperature.