MULTIMODE ACOUSTIC IMAGING FOR CASED WELLS Russian patent published in 2009 - IPC E21B47/14 

FIELD: oil and gas industry.

SUBSTANCE: invention pertains to acoustic cement-bond logging methods for cased wells. The method of imaging the area outside the well casing includes a logging sonde located inside the casing string. The logging sonde carries multiple acoustic transducers. The casing string is exposed to the first acoustic wave by using the first acoustic transducer. The first acoustic wave has the first mode which can be any mode of the following set: longitudinal mode, thickness mode, and bending mode. The first echo signal is received at the first acoustic receiving transducer, after which the first signal is generated and the first measurement is derived from the first signal. Then the casing string is exposed to the second acoustic wave with the second mode which can be any mode of the set but is different from the first mode. The second echo signal is received at the second acoustic receiving transducer and the second signal is generated. The second measurement is derived from the second signal. The zone outside the well casing is determined from the combination of the first and second measurements.

EFFECT: more reliable assessment of the zone outside the well casing.

20 cl, 13 dwg