Electroseismic Prospecting in Layered Media

Source abstract

Electroseismic (ES) prospecting is an experimental method that seeks to use the conversion of electromagnetic (EM) waves to seismic waves in the earth to explore for oil and gas. The wave conversion occurs through the phenomenon of electrokinetics, for which a complete set of partial differential equations was derived by S. Pride. In this paper, we show how Pride’s equations in plane layered media can be written in a convenient mathematical form suggested by B. Ursin, who used this form to give a unified treatment of EM waves, acoustic waves, and the waves of isotropic elasticity in plane layered media. We use Ursin’s formalism, which we develop and simplify for the case of a stack of homogeneous layers, to derive explicit formulas that can be made the basis of an efficient computer code. Numerical results are presented for spatially extended electrode sources that have been used in field tests of ES prospecting. More generally, the methods developed are applicable to any system that can be put into Ursin’s form. In particular, the code that was written for ES can be modified to compute purely seismic waves, purely EM waves, or the waves of Biot theory, since all these phenomena are included in the equations of electrokinetics when parameters are specialized appropriately.