Geomechanical Characteristics and Wellbore Instability for Nahr Umr Oil Field

Abstract

Wellbore instability occurs when an open well cannot maintain its size, shape, or structural stability. It is a common issue especially in shale sections and can be caused by both mechanical factors, such as poor drilling technique or weak rock, and chemical factors, such as interactions between the rock and drilling fluid. This problem can lead to costly and dangerous complications. In this study data from three wells in Nahr Umr Oil Field (NR-10, NR-12, and NR-14) in southern Iraq were analyzed to determine pore pressure and rock strength parameters, as well as in situ horizontal stresses. The results showed an increase in pore pressure and horizontal stress in shale units, and various geomechanical parameters were also estimated. The study showed the fault regime in the area is a strike-slip fault and suggested the estimated pore pressure values while drilling hole sections to prevent problems at abnormal and subnormal formations.