Depth Registration of P and S Data
Two critical assumptions are involved in elastic wavefield stratigraphy: (1) Across some stratigraphic intervals, one mode of an elastic wavefield might show different seismic sequences and facies than its companion modes do, and (2) S-wave seismic sequences and facies are just as important in geologic interpretation as P-wave seismic sequences and facies are.
Once those two assumptions are accepted, a serious interpretive challenge then is encountered — depth registration of P and S images. An interpreter must be confident that a targeted data window in P-wave image space is depth equivalent to a data window selected from S-wave image space before seismic sequences and seismic facies in the respective data windows can be combined into an elastic wavefield stratigraphy analysis. Until depth-equivalent P and S data windows are defined, no meaningful geologic interpretation of P and S sequences or facies can be done.
To effectively combine P and S reflection data into a unified stratigraphic interpretation of a prospect, it is necessary to identify the specific P-wave time window and the specific S-wave time window that span each targeted stratigraphic sequence that is to be interpreted. For example, to calculate reliable VP/VS ratios over a reservoir interval, it is essential to identify P and S reflection events that define the top and base of the reservoir sequence as accurately as possible. The interpreter's dilemma is to decide which S-wave reflection event occurs at the same stratigraphic boundary where a P-wave reflection event has been interpreted.
This requirement for a methodology that accurately transforms