Three-dimensional inverse scattering applied to cross-well induction sensors

Cross-well induction logging as known in the oil industry is a method for d etermining the electrical conductivity distribution between boreholes from the low frequency electromagnetic field measurements in the boreholes. In t his paper, we discuss the reconstructions of the three-dimensional (3-D) co nductivity distribution using the contrast source inversion (CSI) method. I n order to improve the reconstruction results, the concept of the extended Born approximation has been used to arrive at a preconditioning operator. R esults of a number of numerical examples show that by using this preconditi oning operator, a large conductivity contrast of the unknown objects (facto r of 100) can be reconstructed up to an acceptable degree of accuracy. More over, in each iteration, the computational effort to generate the precondit ioning operator is negligible.