A DOWNHOLE ULTRASONIC TRANSDUCER, DOWNHOLE PROBE AND TOOL COMPRISING SUCH A TRANSDUCER

摘要

A downhole ultrasonic transducer (10) used to transmit and/or receive ultrasonic waves in a hydrocarbon well where a fluid is present comprises: - a metal housing (11) defining an internal cavity (12) isolated from the fluid of the hydrocarbon well (100) by a membrane wall (13) made of metal or metal alloy; - a piezoelectric element (14) mounted inside the internal cavity (12), the piezoelectric element (14) having a front side (20) mechanically coupled on the membrane wall (13); wherein: - the internal cavity (12) is at a pressure unrelated to a hydrocarbon well pressure; - a back side (21) of the piezoelectric element (14) is arranged to be free to oscillate in the internal cavity (12) so as to generate a high acoustic impedance mismatch between the piezoelectric element (14) and the internal cavity (12) at the back side (21) and to maximize acoustic transmission at the front side (20); and - a thickness (ei) of the membrane wall (13) is such that there is a common resonance between the membrane wall and the piezoelectric element thereby achieving high acoustic transmission through the membrane wall (13), and such that the membrane wall (13) is suitable to resist to the hydrocarbon well pressure.