The limited resolution of conventional seismic surveys often results in challenges to successful reservoir development. Reservoir structure and thickness may not be determined from the seismic to the level of detail necessary, affecting the placement of the horizontal well. We describe a new sonic imaging technique that resolves these features. In addition the position of the well in relation to the reservoir perimeter can be determined with great accuracy

Single-well sonic imaging places the acoustic transmitter and receivers in the same well, analogous to recording a micro-scale seismic reflection survey downhole. Using modified sonic logging technology, sound is broadcast into the formation and reflections are converted into a two- or three-dimensional spatial image of the zone around the borehole. Acoustic reflectors such as the top of the reservoir, calcite stringers, or fractures are mapped at distances of 10-15 meters from the well with resolution on the order of one-half meter. We show several examples of surveys conducted in horizontal wells to illustrate applications of the technique.

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