Vertical Stress Estimation in Mansouri Oil Field by Using Graphical and Petrophysical Logs and Determination of an Empirical Relation to Evaluate the Horizontal Isotropic Stress

The magnitude of in-situ stresses is one of the most important factors affecting wellbore stability. In cases we do not encounter special tectonic conditions, in-situ stresses usually consist of three major trajectories, two horizontal and one vertical. In this paper insitu stresses are estimated in the final depth of 4 wells in Mansouri oil field, southwest of Iran. As the most important parameter in vertical stress estimation is density, the formation surrounds the well is divided into three zones: with density log, without density log but with graphical log, and without density and graphical log. Then, the density of formation is evaluated by using these logs and the vertical stress is estimated in wells No. 1, 47, 48, and 56. A relation is also suggested to estimate the horizontal stress by using empirical relations. The results show that the vertical stress gradient calculated in the studied wells has inconsiderable variations in magnitude and can be used as a reference in future studies.