Abstract: In strict sense of electric log inversion, multiple forward calculations are performed many times during each iterative procedure of inversion algorithm, which takes a long time. In particularly, real-time inversion of electrolog data is unlikely to be achieved in complex three-dimensional stratigraphic models. There is a great challenge to process efficiently electrolog data in real time. In this paper, based on radial step medium model, forward response is pre computed and linear interpolation is called directly in inversion process, which greatly saves inversion time. An adaptive differential evolution algorithm is proposed to transform array lateral inversion problem into a nonlinear global optimization problem. Compared with classical differential evolution algorithm and Marquette algorithm, the adaptive differential evolution algorithm has characteristics of high search success rate (90%), low average number of iterations (21), and good noise immunity. The algorithm is tested under layered media model with different invasive conditions. Resistivity using the algorithm is closer to the true resistivity than apparent resistivity, which meets evaluation needs of oil and gas reservoirs.

Key words: adaptive differential evolution algorithm, array laterolog, rapid inversion, nonlinear global optimization