Eliminating the azimuth ambiguity in reflected S-wave imaging logging based on the azimuthal receiver mode

Abstract

Due to the symmetrical directivity of a dipole transducer, dipole reflected S-wave imaging logging results in ambiguous azimuth measurements of reflectors. Based on an orthogonal dipole source and an eight-element azimuthal receiving station, we proposed an improved method for measuring the azimuth of a reflector and applied it to a borehole azimuthal acoustic reflection tool in our laboratory. Based on the dipole transmitting and receiving mode, to determine the strike of a reflector, this method superposes the echo amplitude and azimuth distribution curves of X and Y dipole transmitting and azimuthal receiving and compares the amplitude-superposed value of the echo received by two receiving elements close to the reflector azimuth and a virtual image azimuth. It accurately obtained the true azimuth of the reflector. The feasibility of this method was verified by numerical simulation, a physical experiment, and a field test. The results show that the amplitude of the P–P, P–S/S–P, and S–S echoes received by the different receiving elements were different when there was a reflector in place. For any type of echo, the amplitude superposition value of the echo received by a receiving element close to the reflector azimuth was significantly greater than that of the echo received by a receiving element close to a false azimuth. Therefore, based on the azimuthal receiving mode, the azimuth ambiguity of dipole-reflection S-wave logging can be eliminated.