Multimode acoustic imaging in cased wells

A method for imaging a description of a zone behind a casing of a well, the method using a logging tool positionable inside the casing, the logging tool carrying a plurality of acoustic transducers, the method comprising:

• a. insonifying (72) the casing with a first acoustic wave using a first acoustic transducer for transmitting among the plurality of acoustic transducers, the first acoustic wave having a first mode that may be any mode of a set of modes defined as follows:
• extensional mode, thickness mode, flexural mode;
• b. selecting (71) at least a first acoustic transducer for receiving among the plurality of transducers, the first acoustic transducer for receiving having a location adapted to receive a first echo corresponding to the first acoustic wave;
• c. receiving (73) at the first acoustic transducer for receiving the first echo, and producing a first signal;
• d. extracting (76) from the first signal a first measurement;
• e. insonifying (74) the casing with a second acoustic wave using a second transducer for transmitting among the plurality of acoustic transducers, the second acoustic wave having a second mode that may be any mode of the set of modes and is distinct from the first mode;
• f. selecting (79) at least a second acoustic transducer for receiving among the plurality of transducers, the second acoustic transducer for receiving having a location adapted to receive a second echo corresponding to the second acoustic wave;
• g. receiving (75) at the second acoustic transducer for receiving the second echo and producing a second signal;
• h. extracting (77) from the second signal a second measurement;
• i. evaluating (78) from a combination of the first measurement and the second measurement the description of the zone behind the casing of the well.