We show on synthetic and field data examples that joint pre-stack AVA inversion of PP- and PS-wave data can significantly improve estimation of P-impedance, S-impedance and density. For reservoir characterization, improvements in these parameters can better identify reservoir rock and fluid properties. For reservoir monitoring time-lapse (4D) changes in P-impedance, S-impedance and density can lead to inversion of saturation and pressure changes. We see that, in the joint inversion, 4D S-impedance is better estimated and not coupled to 4D P-impedance. These claims are first demonstrated on synthetic data, and then shown on an onshore unconventional play from Colorado and on offshore 4-D -4-C dataset from the North Sea. Joint inversion of PP- and PS-wave data requires a higher level of care compared to PP-waves since the two wave-modes need to be acquired, processed and merged properly. This has diminished the use of converted waves in the past. However, modern acquisition and processing on land and offshore data make this technology quantitatively more accurate and realizable. As such, we also provide best practices for a successful project. We shown that joint inversion can lead to a larger chance of success in placing exploration and development wells.

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