ACOUSTIC DEVICES TO MEASURE ULTRASOUND VELOCITY IN DRILLING MUD

摘要

An apparatus and method is disclosed for measuring ultrasound drilling mud velocity downhole in real time. One or more generated acoustical pulses are detected upon traversing two separate path lengths, and ultrasonic velocity is determined from differences in the pulses upon traversing their respective path lengths. Alternately, a single measurement can be made using an acoustic pulse traversing a specified path length. A transducer is discussed having a piezoelectric crystal, a backing material having matching impedance, and a facing material disposed between the crystal and the fluid having an impedance intermediate to crystal and fluid. A concave front face of the crystal increases sensitivity to off-axis signals. Improved signal resolution can be achieved using a controlled shape input pulse optimized for certain drilling conditions. A method of echo detection using wavelet analysis is preferred.