The Effects of Mud-Filtrate Invasion on the Interpretation of Induction Logs

A rigorous model of mud-filtrate invasion has been developed with a numerical fluid-flow simulator. This model is used to investigate the effects of certain fluid-flow properties of the invasion process. The model also has the capability to calculate the resistivities that would be measured by deep and medium induction logs. The resistivity measured by the two logs is shown to vary with time, and the difference between the resistivities measured by the two logs is indicative of the amount of invasion that has occurred. This study indicates that multiple logging runs over an interval could be used to evaluate the fluid-flow characteristics of a formation.