Natural fracture analysis and determination of fracture parameter using image log, Bangestan Reservoir, Gachsaran oil field, SW Iran


Fracture system in carbonate reservoirs is very complex. Understanding the features of fractures such as dip, strike and the other parameters can help to distinguish the behaviour of reservoir in any exploration and production plan. Image log is the best way to investigate feature planes like fracture and bedding. Image log in one of drilled well #10x393 of Bangestan reservoir in Gachsaran oilfield was used and interpreted by X-tended Range Micro Imager (XRMI). The study resulted to identify 333 fractures and 78 beddings in interval understudy. Based on stereo net and rose diagram of fracture and bedding, interpreting was made. In this area, according to the origin classification, the fractures divided into three sets: longitude, transverse and oblique. Fracture parameters such as fracture density (VDC), fracture aperture (VDA) and fracture length (VTL) were calculated. Velocity deviation log (VDL) from conventional log calculated and compared with fracture parameters. VDA and VDL data make in past a well agreement together while VDC and VTL are less correlated with VDL. It seems fracture aperture plays an important role than other fracture parameters in the reservoir quality due to their effects on permeability to be increased.