Effects of Geometrical-Size of Cylindrical-Shell Transducer on Acoustic-Beam Steering Efficiency for a Slim-Hole Acoustic-Logging Tool

ABSTRACT

The slim-hole acoustic-logging tool is often used for measurement while drilling and horizontal well logging. The source and receiver are generally thin cylindrical-shell piezoelectric transducers. The radius of the drilling-collar limits the size of the cylindrical-shell transducer in the logging tool. The smaller the radiation area of the transducer, the smaller the radiated acoustic energy, and the smaller its radius, the higher the frequency of the radiated acoustic signals. Besides, the attenuation for higher frequency wave propagating in the medium is higher. Due to these reasons the amplitude of the measured acoustic signal by using the slim-hole logging tool is usually much smaller than that by using the conventional logging tool. Therefore, the acoustic-beam steering technology is important for enlarging the amplitude of the received acoustic signal during logging with a slim-hole logging tool. The geometrical-size of the cylindrical-shell transducer influences the acoustic-beam steering efficiency of the logging tool with a line-array source and a receiver. In this paper, in the frame work of the acoustic-logging transmission network model with the concept of directivity-weighted coefficient, we have carried out the calculation and analysis of the effects of geometrical-size of the transducer on the acoustic-beam steering efficiency of the slim-hole acoustic-logging tool with a line-array source and a receiver. The calculated results are useful for optimizing the design of the slim-hole acoustic-logging tool with a line-array source and a receiver.