A fast algorithm for three-dimensional interpretations of single-well electromagnetic data

An efficient inversion algorithm has been developed for three-dimensional (3D) interpretations for single-hole electromagnetic (EM) logging data based on a modified extended Born approximation (MEBA) scheme. The single-hole data was collected at an oil field undergoing CO2 injection in southern California using a tool, Geo-BILT, developed by Electromagnetic Instruments, Inc (EMI). The tool is equipped with a multi-component source, and an array of multi-component receivers at different separations. The inversion result provides a reasonable electrical conductivity image to a distance of 10 m from the well, and illustrates several zones with lateral conductivity variations that could not be resolved with traditional induction logging tools. The computer cost of the inversion processes can be further reduced using a trivial multi-grid methodology