Nonlinear inversion of the electrode logging measurements in a deviated well

We develop a nonlinear inversion method for reconstructing the 3-D electric al conductivity in a highly deviated well with invasion using electrode log ging (static field) measurements. The integral equation is formulated in an oblique polar coordinate system so that the dipping bed environment can be modeled without approximations. The computation time is dramatically reduc ed by using a nonuniform discretization grid in the direction away from the borehole. Moreover, the contrast source inversion method, which has been s uccessfully applied to the electrode logging problem using a homogeneous ba ckground, has been modified so that the inhomogeneous background carl be us ed without introducing a borehole Green's function. Numerical examples have shown that the present inversion method formulated in an oblique polar coo rdinate system can be used as an interpretation technique for the electrode logging measurements.