Joint inversion approaches for geophysical electromagnetic and elastic full-waveform data

We present joint inversion approaches for integrating controlled source electromagnetic data and seismic full-waveform data for geophysical applications. The first approach is the joint petrophysical inversion carried out by reconstructing petrophysical parameters such as porosity and saturations instead of the usual geophysical parameters such as resistivity, seismic velocities and mass density. This approach utilizes the strong correlation between the electromagnetic and seismic parameters through the petrophysical relationships. Another approach that does not require the a priori petrophysical correlation is the joint structural inversion method. In this approach, the inversion is carried out by employing a regularization function for enforcing the structural similarity between the resistivity and the seismic velocities and the mass density. In this method, we employ the cross-gradient function, which has been shown on many occasions to be quite effective. By using a time-lapse reservoir monitoring example, we show that both joint inversion approaches produce results that are superior to those obtained by disjointed inversions. Hence, these joint inversions have great potential to be the next-generation tools for reservoir characterization and monitoring.