Use of full-waveform sonic data to image near-borehole structural features

The full waveforms recorded by an array of receivers in a modern full-waveform sonic tool contain secondary arrivals that are reflected from near-borehole structural features. These arrivals are used to form an image of the near-borehole structural features in a manner similar to seismic migration. Possible uses of this technique include horizontal well logging; structural dip and contour determination; fault, salt dome, pinnacle reef, and fracture zone imaging; and EOR steam-flood monitoring. Examples are given for a deviated well penetrating a North Sea reservoir, and for a horizontal well penetrating a thin (10m thick) reservoir. For the horizontal well case, full-waveform sonic data are successfully used to image the reservoir top as the well penetrates into the reservoir and continues near-parallel to the reservoir boundary.