In well logging measurements, the effect of the fl uid in the well on the resistivity log curves and the investigation depth/distance for 16 and 64 inches logs were investigated in two-dimensional numerical modeling with the assumption that underground structures are symmetrical. Structural information was obtained via recovering the real resistivity values by using the inversion rather than empirical approaches. Generally, in the case of using the conductive fl uid (1 ohm.m<) depending on the ratio of unit thickness (k) with respect to the length of log (l) (i.e. k/l), the insulating formations produce an "M" shaped signs for k/l<1 and appears as the conductive unit that cause fi ctitious structures in the data. The depth/distance of the research on the other hand causes deviations in the resistivity of structure due to tool length and distance. By the help of the inversion study one of the possible models is obtained. Contribution of this method to such studies is the reveal of compatibility of the resistivity model and data that usually neglected in other approaches.