Single well sonic imaging of near borehole structure

Summary form only given, as follows. Modern exploration for oil-bearing reservoirs involves characterization of subsurface structural features. Sonic measurements using an array of receivers have made possible the acquisition of entire waveforms, allowing the processing of arrivals that appear later than the compressional headwave. Secondary sonic arrivals (reflections from near-borehole structural features) are recorded and processed to form an image of the formation structure surrounding the borehole, in a manner similar to seismic migration. The processing technique is illustrated with both synthetic data and data from a real borehole experiment performed in Alaska. Images are shown of near-borehole structure features out to a distance of 18 m from the borehole. Possible use of this imaging technique include horizontal well logging, structural dip and contour determination, imaging faults, salt domes, pinnacle reefs and fracture zones, and steam flood monitoring for enhanced oil recovery