One of the major issues in planning and quantitative interpretation of time-lapse seismic data is quantification of the pressure and stress effects on seismic velocities. To this end we are developing theoretical models of rock deformation. In particular, we have developed a method to assess the effect of rock heterogeneity on effective stress coefficients and showed that an addition of a tiny amount of very soft material may significantly affect effective stress coefficients. This has been demonstrated for an idealised concentric sphere geometry. Currently we are examining the magnitude of this effect for more realistic geometries.
A related effort is to assess the effect of core damage of velocity-stress relationships measured in the laboratory. To study this effect we are developing a method to compare laboratory measured velocities with sonic log measurements for different types of rocks.
Prof. Boris Gurevich (B.Gurevich@curtin.edu.au)