Full text loading...
-
A Stable Scheme of Joint Migration Inversion in the Pseudo-Time Domain
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, EAGE 2020 Annual Conference & Exhibition Online, Dec 2020, Volume 2020, p.1 - 5
Abstract
Joint migration inversion is a full wavefield inversion method that tries to minimize the mismatch between measured and modeled reflection data. One key feature of JMI is its parametrization: two separate parameters, reflectivity and propagation velocity, have orthogonal effects on the modeled data. The reflectivity is responsible for the amplitudes of reflections and the velocity for the phase effects. This separation helps reduce the non-linearity of inversion. During JMI, with the velocity being updated, the reflectors in the updated image are also shifting in depth accordingly. This interaction between the two parameters during inversion is desired to keep the image time-consistent with the measured data, but still may lead to an instability of JMI. Therefore, we propose a more stable JMI scheme, which parameterizes the models with vertical time, termed pseudo-time JMI. In pseudo-time, the updates of velocity will not result in the associated location changes of reflectors in the estimated image. Instead, the reflectors are only getting more focused. Moreover, inversion in pseudo-time also helps avoid the computational waste due to the spatial over-sampling of deep layers. We demonstrate the effectiveness of our proposed method with a synthetic example and a field data from the Vøring basin in Norway.