Borehole Acoustic Reflection Survey for High Resolution Imaging

Summary Borehole Acoustic Reflection Survey (BARS) data were acquired in the Brent formation in the Norwegian North Sea in an exploration well for Hydro. In total, an interval of approximately 300 m was logged. Initial near-wellbore formation images were obtained within 24 hours. The quality of the sonic waveform data was very good. However, significant uncertainties in the actual tool depth caused by rough weather conditions during the time of logging, affected to some extent the coherence and the range of the formation images. The high-resolution image shows an interface dipping at 5° and clearly visible for at least 45 ft away from the well bore. The dip of the interface is in agreement with the expected local geology at the well location. The highresolution event can be correlated to a 1 m thin coal bed intersecting the borehole and indicated by the petrophysical logs. The coal bed is interpreted as the Top Etive Formation. The BARS images helped characterizing the l o cal g eol og y an d th e res erv oi r. In ad di ti on , t h e hi gh resolution sonic images augment the understanding of the seismic responses in the reservoir section.