Wellbore stability analysis using integrated geomechanical modeling: a case study from the Sarvak reservoir in one of the SW Iranian oil fields

Abstract

In this study, an integrated geomechanical analysis was carried out for the Sarvak carbonate reservoir in three wells of one of the oil fields in Abadan Plain, SW Iran. The static Young’s modulus (ES), unconfined compressive strength (UCS), cohesion (C), and angle of internal friction (Φ) were determined directly, using rock mechanics tests. Subsequently, some correlations were introduced based on tests-to-logs relationships. The 1D geomechanical models were constructed for three wells in the north, center, and south of the studied field. The results show that the stress state is not uniform for the studied wells, as it is strike-slip normal in northern well, strike-slip in central well, and strike-slip reverse in southern well. Likewise, the stability of the wells was evaluated using Mohr-Coulomb and Mogi-Coulomb criteria, and it was observed that the Mogi-Coulomb criterion could more accurately estimate the breakout pressure. According to the recognized borehole breakouts in image logs, the SHmax direction is to NE-SW in all three wells. Based on the wellbore stability analysis, it was concluded that the more stable directions for drilling are NW-SE in the northern part, E-W and N-S in the central part, and NE-SW in the southern part of the studied oil field.