Characterizing well features

A water or petroleum well is tested to obtain information about well features, especially that part of the well beneath the ground surface. Problems of irregularities in the well such as stuck tools, casing damage, damaged zones in an uncased well, or debris in a well, can be detected. Oscillations are created in the fluid pressure in the well. Transducers measure the pressure oscillations, and the measured pressure oscillations are used to determine resonant frequencies. The measured resonant frequencies are used to determine the characteristic impedance and the depth of each reflector in the well, after removing resonances caused by known reflectors. It is then possible to determine the nature of each unknown reflector based on suspected problems or the well's operational history.