Design of ultrasonic array transducer for downhole forward-looking imaging

In order to realize downhole forward-looking imaging, an ultrasonic phased array transducer for downhole forward-looking imaging has been designed. The transducer consists of a planar circular array combined with a concave focusing acoustic lens. By using phased array emitting focused acoustic beams and controlling these beams for rotational scanning, it achieves acoustic beam coverage and image acquisition in the forward direction of the borehole under conditions of relatively few array elements. This paper derives the spatial acoustic field of the transducer and simulates the acoustic field characteristics and the effects of related parameters on the focusing performance of the transducer. Based on theoretical derivation and simulation, various parameters of the transducer were determined, and a forward-looking imaging transducer was fabricated. Experimental tests were conducted on the acoustic field of the transducer, and preliminary imaging experiments were carried out. The experimental results show that the measured acoustic field of the transducer is basically consistent with the simulation results, and the obtained forward images can show the shape and position of obstacles.