Tectonic Analysis one of the South Western Oil fields in Iran, Using FMI Image Log

Most hydrocarbon reserves are stored in natural fractured reservoirs and such systems can affect significantly on the reservoir performance. Therefore, geomechanical studies, understanding and investigating fracture patterns to optimize hydrocarbon production are of great importance for the geologists and oil engineers. Geomechanical studies generally include size and orientation of the three main axes of stress, including vertical stress (Sv), maximum horizontal stress (SHmax) and minimum horizontal stress (Shmin). Studies related to well logging and geomechanical issues are the main objectives of electrical imaging techniques of the well wall. Electrical, sonic or image log, which record high-quality images are pushed in to the well and provide important information regarding boundaries of bedding, structural elements such as faults, folds, discontinuities, fractures and even secondary porosities. Accordingly, in this study, in one of the west south oil fields of Iran using Fullbore Formation Micro Imager (FMI) regarding natural and induced fractures related to regional folding and faulting, some characteristics of the fracture patterns have been studied. These characteristics include the type of fracture, orientation, density, openness, amount of sleep and their relationship with regional construction of the ground. Despite the geological complexities of understudied field, orientations of sub surface fractures indicated clear relationship with the local folding axis and in some cases, it seems that it relates more the orientation of the maximum horizontal stress to the present location of the local strike slip fault too. Orientation of the maximum and minimum horizontal stress obtained N30E- N60W and N50E- N40W respectively based on two wells data analysis. According to the open fractures observed in the wells, three stages of fracture are proposed: pre-folding, early-folding and post-folding fractures.