From borehole-sonic data, strongly dominated by modes refracted along the borehole, we can generate images of the formation around the well. This is achieved by using adaptive algorithms which separate the components of the wavefield refracted along the wellbore from the components escaping the wellbore and subsequently reflected at bed interfaces, fractures, and possible faults. The reflection data are converted into images of the formation using syntheticaper

ture processing. We show how the information provided by the sonic images at decimeter resolution can contribute to significant changes in the understanding of a reservoir.