f Characteristics of crosswell seismic data for reflection imaging

Phillips Petroleum Company acquired three tomographic crosswell datasets in early 1992 at the British Petroleum Devine test site, Frio County, TX, using Stanford University's piezoelectric Bender source and hydrophone receivers. These three datasets, recorded with source well to receiver well offsets of 100m, 200m, and 300m, show that the wavefield changes as a function of offset, even though there is little lateral change in the lithology. Onderstanding the nature of the wave propagation at the different offsets is important in determining how to process the data for traveltime tomography and reflection imaging. We find that coherent source related noise (tube waves propagating in both the source and receiver wells is a dominant waveform at all three offsets, especially at later times in the records. At farther offsets, most of the recorded wave field energy appears both as tube waves in the source and receiver wells, and as post-critical reflections from the major lithological interfaces.