Simulation of well-log response of the acoustically-induced electromagnetic field in a porous formation
孔隙地层中声波诱导的电磁场测井响应模拟

During acousto-electric logging, the acoustic wave excited by a point acoustic source in a fluidfilled borehole propagates into the fluid-saturated porous medium and causes relative motion between the charge-bearing pore fluid and the skeleton, inducing electromagnetic field. To simulate the logging response, a numerical full-waveform simulation method is proposed. The acoustic field is taken as uninfluenced by the converted electromagnetic field, and is solved separately. The electric field is taken as quasi-steady. The full Biot-Rosenbaum model is adopted to obtain expressions for the acoustic field around the borehole. These expressions are then used to formulate the converted electric and magnetic fields in and out of the borehole. Calculations show there are electric and magnetic fields that accompany the compressional, the shear and the Stoneley waves. And there is a critically refracted electromagnetic wave, which travels along the borehole wall. The amplitude of this wave is very weak in the full waveform. Both the axial and the radial components of the electric field increase when the receiver is placed farther off the borehole axis. On the borehole wall, the shape of the waveform of magnetic field is similar to that of the axial electric field.