A logging-while-drilling(LWD) slim compensated long-spaced sonic tool that can be run in boreholes as small as 5 3/4 in. has been found to have useful drilling applications in the Gulf of Mexico. The 4-3/4-in.-OD tool features a two-transmitter, four-receiver acoustic array. Alternate firings of the two transmitters yield two sets of foure waveforms that are procesed downhole with a semblance correlation technique to compute compressional and shear slowness rangingfrom 40 to 180 microseconds/ft. The waveforms are stored n memory for advanced processing at surface. Applications of the sonic information include real-time processing of synthetic seismorgrams, prediction of pore pressure, computation of acoustic porosity from compressional and shear slowness, and determination of rock emchanical properties for borehole stability analysis.
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