Comparison of image log interpretation and core analysis advantages for study of fractures in hydrocarbon reservoir rocks: a case study in the Asmari reservoir Aghajari oil field

The Oligo-Miocene Asmari Formation is one of the main reservoir rocks of SW Iran with several decades of production history from different oil fields in the Zagros fold- thrust belt. One of the main reasons for the high quality of the Asmari reservoir is well developed fracture system in this formation. Characteristics of fractures such as type, opening and orientation can be determined by the core analysis and also interpreting the image logs. This paper attempts to compare the advantages of the image log and core analysis in detecting fractures and other geological feathers in different zones of the Asmari Formation. To achieve this goal, we have compared the image log and core of well no. 89 of the Aghajari oil field. Comparison of the core well no. 89 of the Aghajari oil field with its image log revealed distinguish of the bedding planes in the core easier and more reliable than the image log. This study demonstrates the image log is more capable than core to detect the open fractures, while it is not suitable for detecting filled fractures. Indeed, image log rarely can detect shear fractures, but if it is calibrated with core, it can detect shear fractures with reasonable accuracy.