Acoustic-Wave Radiations of Mono- and Dual-Sources in Poorly Bonded Cased Boreholes: Modeling and Field Applications

Measurement of formation acoustic properties from cased-hole acoustic logging is often problematic when the casing is poorly bonded with formation. A dual-source technology has been used to measure formation acoustic properties through casing, and the development of this dual-source technology requires an understanding of the effects of acoustic-wave radiation. Here, the theoretical formulations for the acoustic-wave radiation in well and poorly bonded cased boreholes are derived, and the acoustic-wave radiation excited by dual-source and monopole sources under various casing-cement bonding conditions are simulated. The analytical modeling results showed that the formation signal excited by acoustic dual-source can be significantly enhanced, indicating the advantages of this dual-source design in the cased borehole. The modeling results were applied to interpret acoustic data acquired in cased boreholes, where theoretical predictions and measurements were in good agreement.