Method and apparatus for communicating data in a wellbore and for

Abstract

A transducer is described especially for use in providing acoustic transmission in a borehole. The transducer includes a multiple number of magnetic circuit gaps and electrical windings that have been found to provide the power necessary for acoustic operation in a borehole while still meeting the stringent dimensional criteria necessitated by boreholes. Various embodiments conforming to the design are described. Moreover, the invention includes transition and reflector sections, as well as a directional coupler and resonator arrangement particularly adapted for borehole acoustic communication. An acoustic communication system is described especially designed for use in providing acoustic transmission of information in a borehole. The communication system comprises a surface transceiver and at least one downhole transceiver. The surface transceiver operates in conjunction with a host computer that sends commands to the downhole transceiver. Subsequently, the downhole transceiver transmits encoded data from subsurface, borehole sensors to the surface transceiver. The preferred embodiment uses Minimum Shift Keying (MSK) modulation for both transmitting commands to the downhole unit and for transmitting data to the surface transceiver. To facilitate operation of a coherent communication system in the inhospitable environment of a borehole, the acoustic channel is characterized to enable the system to choose the best possible frequency and bandwidth for communication transmission. Additionally, the system achieves synchronous operation by transmitting synchronization signals between the downhole transceiver and the surface transceiver prior to the units exchanging commands and data.