Abstract: The properties of porous material that is hydraulically coupled to a well through openings in cased or in uncased portions of the well are evaluated. The process involves initiating a pressure wave, typically at the well head, so that the pressure oscillations extend to the porous material zone under investigation. Flow of fluid between the well and formation changes the amplitude and frequency content of the oscillations traveling up and down the well. That is, the oscillations are modulated from the form they would have in a like well with no hydraulic communication to the formation. The properties of the formation are derived from these changes.

Abstract: A method of testing a water or petroleum well to obtain information about well features, especially that part of the well beneath the ground surface, is described. The method is especially useful in detecting problems or irregularities in the well such as stuck tools, casing damage, damaged zones in an uncased well, or debris in a well. The method involves creating oscillations in the fluid pressure in the well. Transducers measure the pressure oscillations. 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.