Azimuthal acoustic reflection imaging logging,which can measure the distance and azimuth of geological bodies within a range of tens of meters beside the borehole,is becoming an important technology for geophysical applications.Measurements and analysis for single-well acoustic reflection imaging in the model with 1∶1 reflection interface outside the borehole provide physical validation of this technique.In this paper,the analytical solution for the response wavefield of monopole P-wave in the fluid-filled borehole is deduced first by using the virtual source analogy combined with the cylindrical wave expansion method.The simulation proves that the radiation wave from the nearby borehole is equivalent to the reflected wave from the reflector outside the borehole.On this basis,the experimental idea of using two model wells to achieve the verification experiment of single-well azimuthal reflected P-wave imaging is proposed.That is,a multi-directional receiving acoustic system is placed in the measurement hole,and a monopole source is placed in the other nearby borehole to radiate P-waves to the measurement hole in order to equate the reflected P-waves from the interface outside the borehole.And the experiment about azimuthal reflected P-wave imaging logging was carried out relying on the laboratory model well group.The experimental measurement results show that the amplitude and arrival time of the azimuthal reflected P-wave are sensitive to the azimuth of the reflector outside the borehole(directional radiation wave),based on which the precise positioning of geological anomalies outside the borehole can be realized.Under the guidance of theoretical simulation and experiment,the prototype of azimuthal acoustic reflection imaging logging tool was designed and developed independently and field tests were conducted to successfully obtain azimuthal reflected P-wave with high signal-to-noise ratio,which fully verified the reliability and effectiveness of the azimuthal acoustic reflection imaging logging technology in measuring the azimuth of reflectors outside the borehole.
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