We would like to report on a new development in monopole acoustic logging technology that opens the way for new applications. A programmable monopole source has been developed that allows the source transmitter pulse frequency and amplitude (signature) to be tuned for the formation and borehole encountered to optimize the monopole wave propagation. This development allows a broader band source signature than possible using a conventional non-programmable monopoie acoustic source. Theoretical studies by various authors, confirmed with field data, show that the borehole geometry plays an important part in the excitation of P wave / P leaky modes and the refracted S / pseudo-Rayleigh wave packet. A larger diameter borehole requires a lower frequency excitation and vice versa. The acoustic source we describe in this paper can be tuned to achieve maximum P wave excitation in high velocity, low Poisson's ratio formations where the P wave signals are low. In another applications, it can be tuned to excite the fundamental P mode in very slow velocity formations where the P wave arrivals are dispersive. Changing the monopole acoustic pulse frequency can be used to selectively enhance or diminish Stoneley wave excitation. The broader spectrum also allows for a more detailed, high-resolution dispersion analysis of the different wave modes for quality control. Programmability of the source ensures optimization for varying formation and/or borehole conditions with a single pass in the well. Field examples of how this source gives superior results compared to conventional monopole sources in a wide range of borehole and formation conditions will be discussed.
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