The Effect of Fault Plane on the Horizontal In Situ Stresses Orientation: a Case Study in one of Iranian Oilfield

Knowledge of the orientation of horizontal in situ stresses is important to some areas of oil and gas field development plans. Borehole breakouts observed in image logs and drilling-induced fractures are the main parameters for the determination of the stresses’ directions in situ.
In this work, the orientations of borehole breakouts were investigated as a function of depth in oil wells A and B in Lali oilfield, in the Southwest of Iran. Borehole breakouts were detected from FMI logs. By the statistical analysis of the borehole breakouts’ orientation in the foregoing two wells, it was found that, while a mean orientation of minimum horizontal stress in well A is NE-SW, the azimuth of breakout in well B is different with a mean azimuth of 312˚±10˚. The result reveals that the orientation must be different in these two wells due to some geological abnormality. Therefore, accurate and reliable geomechanical analyses are crucial steps toward minimizing the costs of drilling and completion programs and mitigating borehole instability problems.