Acoustic excitation with NMR pulse

摘要

NMR measurements are made along with acoustic measurements using one tool. The antenna of the NMR sensor is used to create acoustic signals. Interference between the acoustic and NMR measurements is avoided due to the frequency difference, and by having the acoustic excitation during a wait time of the NMR pulse sequence.

主权项

1. An apparatus configured to evaluate an earth formation, the apparatus comprising:
a logging tool configured to be conveyed into a borehole; a first antenna on a first sensor assembly on the logging tool, the first antenna configured to be switched between a transmit mode and a receive mode, the first antenna configured to be switched between being tuned to a radio frequency signal and an acoustic frequency signal; at least one receiver amplifier on the first sensor assembly configured to produce a first output responsive to the radio frequency signal from the first antenna when in the receive mode and tuned to the radio frequency signal, the at least one receiver amplifier on the first sensor assembly configured to produce a second output responsive to the audio frequency signal from the first antenna when in the receive mode and tuned to the audio frequency signal; andat least one processor configured to estimate from the first and second outputs of the at least one receiver amplifier a property of the earth formation.