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Borehole effects on downhole seismic measurements

There are increasing interests in acquiring crosshole and VSP surveys at frequency up to 1 kHz or more, with the intention to resolve the fine details of structures and lithology between Wells (Bregman et al ., 1989; Harris, 1988; Tura, 1991) However, at frequencies on the order 1 kHz, the existence of the fluid-filled borehole has a strong influence on the downhole measurements. Depending on the frequency and angle of incidence, as well as the formation properties, the measured displacements on the borehole Wall or pressure at the center of borehole may be significantly different from those of the incident wave. Without taking proper care of this effect, any imaging or inversion algorithm which utilizes both the amplitude and phase information of recorded energy will produce erroneous results.