Mariana Gherasim

Elastic modeling and steep dips: unraveling the reflected wavefield

As part of a larger elastic numerical modeling project, we have been investigating how energy reflected from steeply dipping interfaces is recorded using typical multicomponent acquisition geometries. Specifically, we have been interpreting how rcflection events from the flanks of salt dome structures are distributed on 3C and 4C phones for vertical seismic profiles (VSPs) and ocean bottom seismic (OBS) or land surface surveys. The ultimate goal of this investigation is to improve the structural imaging of steeply dipping interfaces and eventually to evaluate the usc of the recorded elastic wavefield for fluid description near these interfaces. In the current work, we focus on a common assumption used when processing converted wave reflection seismic data that most PP energy is recorded on the vertical geophone and/or the hydrophone and that most PS energy is recorded on the horizontal geophones. This is a useful assumption when it is valid, because it eliminates the need for separation of the recorded wavefield into P and S wavetypes. Using two elastic models and different acquisition geometries, we examine the validity of this assumption in the presence of steeply dipping interfaces and discuss the implications for converted-wave and vector imaging of salt flanks.

A preliminary study of salt flank illumination at Vinton Dome, Louisiana: Do we need lateral wavefield continuation?

Project and study overview Vinton Dome project collaboration between AGL (U of H) and Output Exploration. Salt dome onshore Louisiana (first well drilled in 1901). Simultaneous acquisition of 3D surface seismic data and 3D, 3C VSP data (Constance et al., 1999).