4C seismic data analysis for reservoir monitoring in shallow-water environment
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In this report, we present results of seismic modeling and data analysis from a study of a 2D 4C OBC data set acquired in the shallow-water environment typical of the Arabian Gulf. Although surface and interface waves are stronger than in deep-water environment, adequate data processing combined with modelling reveals both high quality reflected P and converted S waves. A combination of shallow water depth and hard bottom rather results in a favorable effective waveform similar to the original source signal. More importantly, we discover that this combination enables inline geophone records to be interpreted as PS-S reflections due to P-S energy conversion at the water/rock interface, stronger than other converted modes. Seismic changes due to water flooding or CO2 injection can be detectable on hydrophone records. Our preliminary analysis indicates that 4C seismic data acquired in shallow-water environment could be helpful for carbonate reservoir production monitoring. In contrast to deep water environment where water column reverberations can present severe problems for seismic imaging and reservoir characterization, the source, the air/water and the water/rock interfaces in shallow-water environment rather act as an effective source that has a similar waveform and short duration as the original source signal. For near-offset data where the energy of converted PS-S reflections are strong, inline geophone data at shallow depths correlate well with synthetic S-wave modeling results using log data. Copyright 2008, Society of Petroleum Engineers.
