Converted phase elastic migration velocity analysis

Abstract

SUMMARYMulti-component elastic seismic data collected at large offsets have the potential to be used in seismic imaging and velocity analysis. In this study, we present an approach for convertedphase elastic-transmission migration velocity analysis with an application for VSP and micro-seismic studies. Our approach is based on the cross-correlation between converted-phase Pand S-waves propagated backward in time, and is formulated as an inverse problem with a differential semblance criterium objective function for the simultaneous update of both P-and S-wave velocity models. The merit of this approach is that it is fully data-driven and requires only one elastic backward propagation to form an image rather than the two (one forward and one backward) acoustic propagations needed for standard RTM. Moreover, as the method does not require forward propagation, it does not suffer from migration operator source aliasing when a small number of shots are used. We present a derivation of the method and test it with the synthetic Marmousi model. We also show the differences between the standard reflection offset domain common image gathers and the converted-phase image gathers that we use for model updates.

Converted-wave seismic imaging: Amplitude-balancing source-independent imaging conditions

“…Separation using the Helmholtz decomposition (i.e., applying only the divergence and curl operators) produces images with inconsistent amplitude and phase that thus require correction before or after the construction of the images (Sun et al, 2004(Sun et al, , 2011Shang et al, 2012;Shabelansky et al, 2013b). Separation using the vector wavefield decomposition is computationally more expensive, but it produces images with consistent amplitude polarity.…”

Migration-based seismic trace interpolation of sparse converted phase micro-seismic data

“…The imaging/migration step is the converted-phase elastic reverse time migration (CP-ERTM) (e.g., Shabelansky et al, 2013) which for a single source is given as…”

“…To overcome the need to estimate source information, we propose to use the converted phase imaging approach (e.g., Xiao and Leaney, 2010;Shabelansky et al, 2013) for migration, during which we store the back-propagated wavefield in time and then use it in the de-migration in reverse order (i.e., forward) in time as the incident wavefield for Born modeling. Note that for reflection acquisition, the subsurface medium is generally sampled only with the scattered wavefield (i.e., a very small portion of the total wavefield).…”

Source-independent full wavefield converted-phase elastic migration velocity analysis

“…Purnell 1992; Stewart et al 2003;Hardage et al 2011) and transmission seismic data (e.g. Vinnik 1977;Vinnik et al 1983;Bostock et al 2001;Rondenay et al 2001;Brytic et al 2012;Shang et al 2012;Shabelansky et al 2013). In particular, for example Xiao & Leaney (2010) and Shang et al (2012) showed that the CP seismic images can be calculated using one elastic propagation without using source information (i.e.…”