Acousto-electric well logging by eccentric source and extraction of shear wave

The nonaxisymmetric acousto-electric field excited byan eccentric acoustic source in the borehole based on Pride seismoelectrictheory is considered. It is shown that the acoustic field inside the borehole,converted electric and magnetic fields and coupled fields outside the boreholeare composed of an infinitude of multipole fields with different orders.The numerical results show that both the electromagnetic waves and the seismoelectric field in the borehole, and the three components of both electric field and magnetic fieldcan be detected. Measurements on the borehole axis will be ofadvantage to determining shear velocity information. The componentsof the symmetric and nonsymmetric acoustic and electromagnetic fieldscan be strengthened or weakened by adding or subtracting the two fullwaveforms logged in some azimuths. It may be a new method of directlymeasuring the shear wave velocity by using the boreholeseismoelectric effect.