Interval Inversion of Borehole Geophysical Data for Surveying Multimineral Rocks

In the paper a new application of the interval inversion method is presented. In investigating multimineral rocks like carbonates and metamorfits the nonlinear well-logging inverse problem becomes an underdetermined or at the best a very narrow type of overdetermined problem. The problem can not be treated by conventional point by point inversion methods with no ambiguity or satisfactory accuracy many times. In order to determine the unknown petrophysical model composed of many parameters in a reliable and accurate way, it is essential using a joint inversion process. Interval inversion is a kind of joint inversion method developed by this team, which adopts a Very Fast Simulated Annealing algorithm in its optimization phase. Having used this method succesfully for the case of shaly sand environments, now the efficiency of the interval inversion method is proven also for the case of rocks with complex lithology. In the presentation carbonate and a metamorfic field examples are shown.