Eliminating the azimuth ambiguity in single-well imaging using 3C sonic data

Abstract

The shortcomings of conventional single-well sonic imaging are the inefficiency in eliminating azimuth ambiguity of the reflector outside boreholes. To resolve this problem, we proposed that 3C data of the reflection echoes be migrated simultaneously. The quantitative expressions of the received 3C data were first derived. The direct correlations between the polarity of the 3C data and the reflector azimuth were analyzed. It was revealed that the reflector positions can be fully identified by the associated echoes consisting of the transverse and axial components of wavefields. And an improved single-well imaging procedure using axial displacement component in addition to transverse components was thus developed. Numerical examples were evaluated for validation of the imaging method. According to the numerical results, the image intensity of the reflectors was effectively enhanced whereas the artificial mirrors of the reflectors were greatly weakened. It was suggested that a sonic logging tool with the 3C receivers be necessary for the image of reflectors without azimuth ambiguity.