This paper describes a prototype swept impulse hydraulic toolcapable of generating a broadband seismic signal at the bitwhile drilling. The source was designed to overcome thelimitations of drill bit seismic services by allowing operationswith PDC bits in inclined wells and in soft formations.Operating principles, seismic processing techniques andresults of a field demonstration of seismic profiling whiledrilling in a shallow well are described. Downhole tests of aprototype swept impulse tool were conducted in a deviatedwell while drilling with a PDC bit at depths of 2000 to 2500feet. These tests represent the first demonstration of reversevertical seismic profiling while drilling with a PDC bit orwhile drilling in an inclined well. The swept impulse seismicsource generated a broadband, high-intensity compressionwave signal that can be used for high resolution seismicprofiling and look-ahead imaging while drilling. Velocitymeasurement accuracy is comparable to checkshot/VSP orsonic log and the information is available in real time with nointerruption of conventional drilling operations.
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