多极源随钻动电测井波场特性实验研究

To develop the new logging while drilling (LWD) method with seismoelectric effect is one of the current focused topics in geophysical exploration. To further understand the coupling mechanism between the elastic field and electromagnetic field in LWD measurements, seismoelectric LWD measurements are conducted in a scaled sandstone borehole with multipole sources (monopole/dipole/quadrupole). The time domain waveforms of seismoelectric LWD signals are recorded by a high resolution experimental set-up in the laboratory. They are analyzed and compared with the signals measured from the acoustic LWD method. The comparison shows that the relative amplitudes of the seismoelectric signals induced by collar waves decrease significantly in the full waveforms of seismoelectric LWD, so that the formation wave velocities can be obtained accurately from the logging data. This confirms the theoretical prediction that the seismoelectric LWD can effectively restrain the influence of collar waves on formation waves. The coupling and attenuation characteristics of seismoelectric signals induced by collar waves are further studied based on the experimental data. Then a quantitative analysis on the mechanism of seismoelectric LWD technique is presented in this paper by combining the seismoelectric LWD measurements in a Lucite borehole and the acoustic LWD measurements in the water tank without borehole. This work is also helpful for data interpretation of theoretical simulations.