Image Number 11 for United States Patent #4953147.
An acoustic transducer having a curved surface to match the inner or outer surfaces of a target surface such as a cylindrical borehole tubular is disclosed. A sequence of excitation pulses causes the transducer to launch a series of high-frequency, short duration acoustic energy pulses toward the tubular. The transducer face receives echos reflected from the surface of the tubular, including multiple echo structures indicative of the repeated echoing of the acoustic energy between the inner and outer faces of the tubular. The characteristics of the tubular surfaces, including the location, area and depth of any corrosion pits on the tubular surfaces, are determined from the full echo waveform. A rule-based Expert System analyzes the full waveform of the echo pulses returned from the tubular to determine the most likely characteristics of the surfaces which produced the full echo waveform. More specifically, the Expert System uses expertise about the acoustic properties of the target medium, as well as constraints chosen by an expert, to determine which signal structures are informational and which signal structures are confounding. As the confounding structures are selectively eliminated from consideration, the Expert System draws conclusions about the condition of the target surfaces.