A Well Path Optimization Approach in an Iranian Oil Field in the Persian Gulf Using a Mechanical Earth Model

Wellbore instability is one of the main or principal problems during drilling. Instability’s issues may cost lots of money and time for companies. Therefore, immense efforts have been devoted to solve it. In this article, using a Mechanical Earth Model and various failure criteria, this problem has been analyzed, and the best stable trajectory has been determined in order to avoid drilling induced wellbore failures. On this purpose, first, the mechanical properties of rock have been specified through log and core data altogether. By the help of (1) density log, (2) Stress Polygon, (3) drilling reports and (4) wall failure data, the magnitude and azimuth of stresses in the region have been calculated. Then to find the stable well path and examine the effect of choosing failure criteria on this procedure, three failure criteria applied to determine safe mud window for all of the possible trajectories. Mohr – Coulomb, as the prevalent criteria, and Mogi - Coulomb and Modified Lade, as criteria that include effect of intermediate stress, are utilized. The results show that, a trajectory characterized by 60 degree inclination from a vertical well and 70-80 degree Azimuth is optimum orientation. Also it is founded out that various failure criteria give same results.