Ultrasonic signal noise reduction processing in borehole imaging application

Ultrasonic imaging instruments are routinely used for formation fracture, stratigraphie dip, and borehole shape determination. Pulse-echo transducers measure the properties of the echoes reflected from the formation, and the signal amplitude and travel time are typically displayed as a circumferential image of the borehole wall. However, a significant interference pattern can be generated when the electroacoustic ringdown of the transducer interferes with low amplitude echoes. In this paper, an image signal processing technique based on borehole fluid/eccentricity correction and median filtering is applied to extract the interference pattern. The proposed processing provides a good noise reduction, preserving formation features.