In-situ stress regime in the Asmari reservoir of the Zeloi and Lali oil fields, northwest of the Dezful embayment in Zagros fold-thrust belt, Iran

Abstract

This paper analyzes in-situ stress field in the Asmari formation with in the complex structures of the Zeloi and Lali oilfields located in the Dezful embayment, SW Iran. The orientation of the maximum horizontal stress, SHmax is determined on the basis of compressive borehole breakouts and drilling-induced tensile fractures observed in eight oil wells, in which we focus on well-log based methods and drilling data to estimate stress magnitudes. In situ stress magnitude in studied fields obtained from 1D mechanical earth modeling in key wells. The maximum horizontal stress trend in this area is NE–SW in accordance with the World Stress Map however a stress perturbation has been recognized in some wells of the Lali field which is approximately perpendicular to the expected direction of the maximum horizontal stress. In situ stress magnitudes in the Lali oil wells are consistent with a strike-slip regime, while in the Zeloi oilfield, normal faulting regime is estimated. The observed strike-slip and normal faulting regime in the Lali and Zeloi wells respectively, Supports the idea that the role of overburden stress magnitude is higher than the horizontal stresses. Undoubtedly, the structural position of the wells, structural framework, faults location, fold geometry, pore pressure changes and mechanical properties of rocks are main factors and have played an important role in stress condition and in situ stress regime in these two hydrocarbon structure.